Vol 12, No 2 (2022)

Cover Page

Full Issue


Proteins of the lectin pathway of the complement system activation: immunobiological functions, genetics and involvement in the pathogenesis of human diseases

Smolnikova M.V., Tereshchenko S.Y.


The complement system is the most ancient components in the innate immunity, mainly functioning to primarily eliminate bacterial agents intravascularly. Moreover, the complement complex proteins play a role as a “bridge” between the systems of innate and adaptive immunity providing adequate conditions for maturation and differentiation of B- and T-lymphocytes. The complement system consists of plasma proteins and membrane receptors. Plasma proteins interact with each other via the three described cascade pathways — lectin (which is most ancient phylogenetically), alternative and classical. Lectins are proteins comprising a separate superfamily of pattern-recognizing receptors able to sense molecules of oligo- and polysaccharide nature and induce their aggregation. Among all the lectins, ficolins (FCN) (common domain — fibrinogen) and collectins (common domain — collagen) — mannose-binding lectin (MBL), hepatic and renal collectins have exert unique functions by complexing with carbohydrate components of microbial wall. Formation of a compound complex “microbial wall polysaccharides + collectin/ficolin + specific mannose-binding lectin-associated serine proteases (MARP)” results in the complement system activation, inflammatory reaction and bacterium elimination. Such scenario is proceeded along the lectin pathway compared to the two other pathways called classical and alternative. Examining a role of the complement system and congenital protein defects in the pathogenesis of various diseases is of topical interest because inborn deficiency of the complement components comprises at least 5% out of total primary immunodeficiency rate, whereas the aspects of their prevalence and pathogenesis remain unexplored. Relevance of investigating the complement system components for diverse populations is tremendous, taking into consideration accumulated evidence regarding an important role of the lectin pathway in viral infections. Lectins, the main proteins in the lectin pathway of the complement activation, are encoded by polymorphic genes, wherein single nucleotide polymorphisms (SNPs) result in altered protein conformation and expression, which, in turn, affects functionality and potential to respond to a pathogen. The distribution of the lectin polymorphic gene frequencies and their haplotypes displays extremely marked population differences. According to analyzing available data, population SNP frequencies including those associated with inborn deficiencies for components of the lectin pathway have been currently scarce or unexplored. hence, here we review major lectins and their functions, their functionally significant SNPs in diverse populations and their pathogenetic importance for host defense functions.

Russian Journal of Infection and Immunity. 2022;12(2):209-221
pages 209-221 views

The third ethical commentary to COVID-19 (two years later) — vaccination, solidarity, and trust

Kubar O.I., Mikirtichan G.L., Vladimirova E.Y., Taghi-zade T.G., Mamedova F.M., Gadgieva U.K., Davtyan S.A., Mavsisyan F.M., Tilekeeva U.M., Gramma R.K., Nasyrova F.Y., Tishkova F.H., Mukhamedova Z.M., Atamuradova F.S.


The systematic monitoring of ethical contents and events related to COVID-19 pandemic, carried out over the last two years, serves to develop a multi-professional discussion on one of the most relevant platforms — Russian Journal Infection and Immunity. Two previous articles consistently presented the moral context of historically established regulatory and epidemiological paradigms and the analysis of readiness/unwillingness to follow them in the real-life conditions during the epidemic crisis. The contemporary moral cross-section of the pandemic, characterized by the state of global loss of values of social unity, trust and solidarity leaves virtually no doubt about the dominant role of ethics as a criterion for resolving conflicts of interest. The point of the peak moral tension was vaccine prevention at all levels of its introduction into an effective resource for containing COVID-19. According to the authors’ personal and professional responsibility, based on long-term scientific research of vaccination-related ethics, embodied in the books Ethics of Infectious Pathology (2014) and Ethics of Vaccination (Criterion of Scientific and Humanitarian Breakthrough (2018), account for our interest in writing this paper. In the Third Ethical Commentary presented to the readers the two ideologically related tasks have been set. First, to consider the ethically verified canon of vaccine prevention specifically exemplified by COVID-19 pandemic. Second, to expand the scope in the discussion of the ethics role by connecting the vaccination in the context of a regional cluster, namely the CIS member states. This opportunity took place owing the long-term cooperation to create ethical evaluation system within the framework of the WHO project Forum of Ethics Committees in the Commonwealth of Independent States (FECCIS) and the practice of developing model laws in the field of social policy and human rights of the IPA CIS. The perspective focus of this work is the need for an innovative approach to develop management decisions by enlarging the interdisciplinary range and expanding the areas of responsibility of social and bioethical meaning while protecting public health in epidemic crisis.

Russian Journal of Infection and Immunity. 2022;12(2):222-238
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Topical issues of clinical symptoms and diagnostics of septic shock

Gomanova L.I., Fokina M.A.


Currently, septic shock remains an unresolved public health problem that leads to serious epidemiological, economic and social problems. Septic shock is a common hemodynamic disorder caused by the interaction between pathogenic microbes and host cells, resulting in developing hypoxia, severe metabolic disorders and multiple organ failure. By now, no unified concept for pathophysiology of septic shock are available. However, the aforementioned data prove that one of the key arms in the pathogenesis is endothelial dysfunction and associated ischemic disorders. In the clinical course of septic shock, three stages are distinguished: the stage of compensation, decompensation as well as the stage of irreversible disorders. The initial stage, or the stage of compensation, is characterized by the activated inflammatory response against infectious agents. Clinically, this stage is characterized by the development of “warm shock”: fever, dermal hyperemia, hyperventilation, increased cardiac output, and tachycardia. The second stage in developing septic shock is characterized by arising “cold shock” as a consequence of escalating heart and respiratory failure. The final stage is the development of multiple organ failure manifested by emerging “shock” organs. Multiple organ failure occurs due to microthrombosis and increasing ischemia, which leads to hypoxia and development of mitochondrial dysfunction in immune cells. At this stage patients are characterized by the progressive cyanosis, developing anuria and intestinal obstruction, as well as altered mental status. Laboratory and instrumental diagnostics of septic shock is a promising approach to examine septic shock. The level of serum C-reactive protein, lactate, and proinflammatory cytokines are not highly specific diagnostic parameters of septic shock, because they can be found in any inflammatory process. Today, the promising diagnostic markers are pentraxin-3, high-density lipoproteins, and phosphatidylcholine. The severity of septic shock can be assessed by determining blood schistocytes, central venous pressure, and the ratio of venous-arterial CO2 and arterial-venous O2 pressure. The following diagnostic methods can be used to determine multiple organ failure: level of serum proenkephalin A119–159 and heparin-binding protein; echocardiography, troponin I concentration and N-terminal pro-b-type natriuretic peptides; measuring activity of the renin-angiotensin-aldosterone system. Here we discuss the key aspects of pathogenesis, clinical picture and morphological changes of septic shock. The promising methods for diagnosing the disease and its complications have been studied.

Russian Journal of Infection and Immunity. 2022;12(2):239-252
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Identifying correlates of protection from Yersinia pestis on a mouse model and assessing an opportunity for their use as markers of human vaccination efficiency

Klyueva S.N., Bugorkova S.A., Kashtanova T.


In case no assessment of changes in incidence rate can be used as an indicator for effectiveness of applied live plague vaccine, it is really necessary to search for other, particularly immunological correlates for vaccine-based protection. The aim of this study was to reveal immunological correlates for plague protection in mice immunized with Yersinia pestis EV NIIEG, and assess dynamics changes in select markers of plague vaccinated subjects. BALB/c mice were immunized with Y. pestis EV at dose of 2 × 102, 1 × 103, 5 × 103, 2.5 × 104 CFU, and on day 21 they were challenged with Y. pestis 231 at a dose of 400 LD50. Immunogenicity was calculated by the Kerber method and ImD50 was determined. Volunteers — 20 subjects who were first vaccinated with live plague vaccine and 20 subjects who were not vaccinated against the plague. Blood cytokine production was measured on the LAZURIT analyzer (Dynex Technologies, USA) in mouse groups before Y. pestis 231 infection on day 14 as well as 21 days after vaccination, in humans — before vaccination, 1, 6 and 12 months after vaccination. The immunized mice showed a significant increase (by 2.2 times) in the induced production of IFNγ and a moderate increase in the concentration of TNFα, IL-10 and IL-17A on day 14 of disease. A high correlation was found between the survival rate of animals and the level of antigen-/mitogen-induced IFNγ production (r = 0.94, p = 0.039), both on day 14 and 21, as well as a noticeable relationship with the level of produced IL-10 and IL-17A on day 14. One month after vaccination volunteers had significantly increase by month 6 (p < 0.05) levels of IFNγ, TNFα, IL-10, IL-17A, although only for IFNγ and IL-17A, the persistence of induced production was noted at a fairly high level for up to a year. Thus, IFNγ and IL-17A can be considered as possible informative correlates of mouse protection against Y. pestis on days 14 and 21, considering the increase in the induced production of these cytokines as adequate markers of the protective efficacy of immunization, and assessing dynamics in these parameters of volunteers vaccinated with the plague live vaccine, the increase in the levels of IFNγ and IL-17A can be considered as a favorable prognostic marker of the immunological efficacy of the vaccine in the period from the month 6 to 12 of observation.

Russian Journal of Infection and Immunity. 2022;12(2):253-262
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A comparative analysis of miRNA expression in human lung epithelial cells during infection with influenza virus and RNAse treatment

Baichurina I.A., Markelova M.I., Shah Mahmud R.


The influenza virus is capable of causing an acute respiratory infection that affects 5 to 20% of the human population annually. The spread of the influenza virus epidemic occurs within a short period of time due to its high contagiousness. In addition, the annual circulation of the virus among livestock and waterfowl increases for new strains a risk of zoonotic transmission to human populations with unestablished yet immunity. In addition, several high virulence pandemic strains have emerged in the past, and the threat of a new pandemic strain is constantly present. The identification of the physiological and molecular aspects related to influenza A can help developing therapeutic approaches to lower side effects associated with the disease caused by this virus. The RNA profile in human cells changes after exposure to influenza virus. Currently, scientists have been increasingly paying attention to study of microRNAs capable of regulating gene expression. Thus, microRNAs may play a critical role in a wide range of biological processes and have been previously shown to be important effectors in multilayered host-pathogen interplay. The study of the quantitative and qualitative miRNA composition is an important tool for diagnosing and treating various diseases at an early stage. The aim of this work is to analyze the microRNA profile for investigating an effect of influenza A (H1N1) virus on human lung epithelial adenocarcinoma cells. The microRNA fraction was isolated by using phenol-chloroform extraction and analyzed with high-throughput sequencing on the SOLiD 550xl wildfire platform using bioinformatic methods. The study examined 129 mature microRNAs from uninfected cells treated with Bacillus pumilus RNAse as well as cells infected with the influenza A (H1N1) virus. It was found that uninfected cells treated with RNase contained 2-fold more different microRNAs that can participate in suppressing carcinogenesis. The peak expression in influenza virus-infected cells is observed for miR-6884-5p. For cells treated with RNase, the peak expression is observed for miR-3923 that was higher by 400-fold than in cells infected with the influenza virus. We hypothesize that intact viruses or their intracellular components are able to alter cellular metabolism by skewing it to decreased resistance to carcinogenesis processes.

Russian Journal of Infection and Immunity. 2022;12(2):263-270
pages 263-270 views

Cytokine markers of clinical variants of infective endocarditis

Samoylenko E.S., Kolesnikova N.V., Podsadnyaya A.A., Bratova A.V.


Introduction. Infective endocarditis is a bacterial disease. Pathogen is localized mainly on heart valves and endocardium. This condition is accompanied by immunopathological manifestations and potential generation of septic process being unfavorable prognosis for disease outcome. Currently, the causes of death of patients with endocarditis have been increasingly presented as thromboembolic complications, which severity depends on variant of the disease course. An important role in imbalanced immune system in the infectious process is assigned to altered intercellular interaction mediated via cytokine network. Activated immune cells produce cytokines, which investigating is important in terms of interpreting changes in immune system functionality, assessing the severity of diseases and controlling therapeutic effectiveness. Infective endocarditis remains a severe disease associated with high mortality despite current advances in diagnostics and treatment. A timely diagnostic process and early initiation of treatment are major factors for successful patient management necessitating to improve diagnostics of various clinical variants of endocarditis course, taking into account pathogenetically relevant cytokines. Objective was to comparatively evaluate the importance of serum cytokine concentrations in patients with uncomplicated course of infective endocarditis and its thromboembolic complications and determine cytokine markers of various variants of endocarditis course. Materials and methods. An immunological examination of 119 blood serum samples from patients with confirmed diagnosis of infectious endocarditis and 20 samples from apparently healthy persons was carried out. Depending on the clinical disease form, the patients were divided into 4 groups: group 1 — primary infective endocarditis (PIE) with thromboembolic complications (n = 24), 2 — PIE without thromboembolic complications (n = 34), 3 — secondary IE with thromboembolic complications (n = 27), 4 — secondary IE without thromboembolic complications (n = 34). The control group consisted of 20 apparently healthy subjects. Immunological studies of serum cytokine concentrations were conducted in all groups. Results. Statistically significant increase in serum concentration of IL-10, IL-6, VEGF-A, IL-18, IL-1Ra and IL-8 was revealed in all clinical groups of patients compared to those in control group (p < 0,05). By correlation analysis, we found a significant positive relationship between IL-10 and IL-18 or IL-6. An increase in the concentration of IL-10 leads to increased level of pro-inflammatory IL-18 and IL-6. The marker of secondary endocarditis was observed as increased level of serum concentrations of IFNγ. A characteristic feature of primary infective endocarditis with thromboembolic complications was revealed as significantly increased serum concentration of IL-8, IL-1Ra and IL-6. Markers of secondary complicated endocarditis were identified as increased level of IL-6, VEGF-A and IL-18.

Russian Journal of Infection and Immunity. 2022;12(2):271-278
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Anti-interferon alpha autoantibodies and their significance in COVID-19

Petrikov S.S., Borovkova N.V., Popugaev K.A., Storozheva M.V., Kvasnikov A.M., Godkov M.A.


During the last two years, treatment of patients with novel coronavirus infection COVID-19 remains an urgent health problem. Interferon proteins are known to play a significant role in antiviral immunity. Some pathological conditions are accompanied by production of neutralizing autologous immunoglobulins against own host interferons (auto-IFN-Abs). There is evidence that autoantibodies against interferons alpha and omega are detected in patients with life-threatening course of COVID-19 pneumonia. The aim of our study was to analyze prevalence of autoantibodies against interferon alpha in patients with COVID-19 coronavirus infection and assess their impact on clinical course of the disease. We examined 70 patients with severe COVID-19, who received inpatient treatment at the intensive care units. Serum autoantibodies against interferon alpha were determined on day 8–50 after disease onset by using solid-phase enzyme immunoassay (ELISA). Patients were divided into 2 groups: those with and without (group 2) autoantibodies against interferon alpha (group 1). Anti-COVID serum from 57 donors was used a control. Among patients, autoantibodies against interferon alpha were detected in 13 (18%) subjects, which level ranged from 26.8 to 1000 ng/ml. Among donors, auto-IFN-Abs were detected in 5 (8.8%) subjects at trace concentrations (from 1.65 to 12.0 ng/ml). Respiratory failure developed significantly more often in patients with auto-IFN-Abs. While analyzing laboratory parameters, it was noted that the concentration of C-reactive protein was significantly higher in the group of patients with auto-IFN-Abs. Mortality rate of patients with high auto-IFN-Abs levels was 60%. In conclusion, it was found that serum autoantibodies against IFN alpha in COVID-19 patients caused lung damage that significantly more often required hardware respiratory support, so comparable by duration with it for patients without auto-IFN-Abs. High concentrations of auto-IFN-Abs (more than 100 ng/ml) in patients with COVID-19 can be considered as a predictor of unfavorable disease outcome.

Russian Journal of Infection and Immunity. 2022;12(2):279-287
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Decreased beta-defensin-2 level in the gingival crevicular fluid as a potential predictor for developing inflammatory periodontal diseases

Tikhomirova E.A., Atrushkevich V.G., Linnik E., Konopleva M.V., Zudina I.V.


β-defensin-2 (HBD-2) is a peptide of innate immunity that provides the first defenсe line in the oral mucosa against invading pathobionts. Under inflammatory conditions, epithelial cells and gingival fibroblasts produce HBD-2. The defective defensin secretion may play a crucial role in the development of inflammatory periodontal diseases. The study was aimed at comparing HBD-2 levels in the gingival fluid and/or periodontal pockets in patients with dental plaque-induced gingivitis (PG), aggressive periodontitis (AgP), chronic generalized periodontitis (CP) and in the periodontally healthy subjects (Control). We examined 142 patients (45.0±1.03 years) residing in Moscow, including 11 patients with PG (35.7±3.69 years), 43 patients with AgP (35.4±0.84 years), 71 patients with CP (54.4±0.86 years) and 17 controls (36.1±2.92 years). We assessed the periodontal tissue condition in all patients during the periodontal and X-ray examination. The samples of the gingival crevicular fluid and periodontal pocket contents were collected from the gingival sulcus and periodontal pockets at 8 teeth of both jaws by paper points. The concentration (C) of β-defensin-2 was determined by enzyme immunoassay (ELISA Kit for Defensin Beta 2, Cloud-Clone Corp., USA). Mann–Whitney U-test (U), the Kruskal–Wallis test (H) and the Dwass–Steel–Critchlow–Fligner post hoc test (W) analyzed a difference significance between the parameters. We estimated the parameter relationship and its power by using the Spearmanʼs rank correlation coefficient (rS). The critical significance level was p ≤ 0.05. The current study showed that the progression of the periodontal inflammation is accompanied by sharply decreased HBD-2 concentration in patient samples (H = 42.8, df = 3, р < 0.001). Thus, the concentration of HBD-2 in the gingival crevicular fluid of the periodontally healthy subjects (control group) ranged from 225 to 1720 pg/ml (C = 738 [477; 1114] pg/ml). In patients with PG, the median value of peptide concentration was 242 [42.5; 610] pg/ml (Cmin = 19 pg/ml, Cmax = 1000 pg/ml). In patients with periodontitis, it declined to critically low levels: CAgP = 54 [3; 195] pg/ml (Cmin = 0, Cmax = 478 pg/ml) and ССP = 25.5 [0; 125] pg/ml (Cmin = 0, Cmax = 298 pg/ml). Thus, we can consider the level of HBD-2 in the gingival crevicular fluid as a potential predictor for developing inflammatory periodontal diseases.

Russian Journal of Infection and Immunity. 2022;12(2):288-298
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Immunodepressive and pathogenetic mechanisms in infectious allergy

Dobrodeeva L.K., Samodova A.V.


The incidence of infectious allergy has been growing mainly due to infection with Staphylococcus aureus, Streptococcus pneumoniae, Klebsiella pneumoniae, with enhancing allergic background by yeast-like fungi of the genus Candida. The frequency of infection has currently become a threat without tending to decline. Undoubtedly, Staphylococcus aureus is a pathogenic species producing highly powerful exotoxins exerting properties of cytolysin capable of disrupting the integrity of any cell wall, destroying epithelial cells, damaging mucous membranes in any organ, including the intestines, wherein it becomes accumulated at any location of staphylococcal inflammation. At the same time, almost 90% of cases of allergic reactions are diagnosed with atopic dermatitis because IgE level in some cases of infectious allergy is increased. The mechanism of the pathogenetic action of reagins is realized by re-binding of antigens to IgE fixed on mast cell and basophil surface resulting in FcR1 cross-linking and release of vasoactive mediators responsible for developing early phase of allergy. IgE concentrations, accounting for only 0.002% of the total blood immunoglobulins in an apparently healthy person, may remain low in atopic bronchial asthma, atopic dermatitis, allergic rhinoconjunctivitis, etc. IgE level is increased not only in atopy, but also in oncopathology, autoimmune diseases, whole body cooling and IgA deficiency. In allergic reactions, an increased level in the extracellular pool of various receptor structures is recorded. Of interest is a comparative analysis of the ratio between frequency of IgE reactions and CD23 shedding in infectious allergies of various etiology. The aim of the study is to establish a role of the CD23 extracellular pool in pathogenetic mechanisms of infectious allergy. There were examined 678 subjects who were at apparently healthy state at the time of the examination, including 545 females and 133 males, as well as 1481 patients with verified infectious allergy who live in the Arkhangelsk Region. It has been established that patients with staphylococcal infection had markedly aggravated symptom complex of pathological reactions linked to anemia, neutropenia and deficiency of phagocytic protection. Pathological reactions in infectious allergies are accompanied by sharply increased level of sCD23 with its abnormally high concentrations (> 200 ng/ml) found in 51.7% of cases paralleled by increased level of serum IL-10 and reagins in 21.43 and 35.7% cases, respectively, along with phagocytic defense deficit observed in 85.7% as well as accumulation of CEC in 92.86%. A parallel increase in level of sCD23 and IgE is associated with increased percentage of T helpers, cytotoxic T lymphocytes, activated T cells expressing IL-2 receptor, along with upregulated of the MHC II molecules.

Russian Journal of Infection and Immunity. 2022;12(2):299-305
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Analysis of the state of immunity in patients with chronic gastritis infected with Helicobacter pylori

Mokhonova E.V., Lapin V.A., Melentiev D.A., Novikov D.V., Neumoina N.V., Perfilova K.M., Neumoina M.V., Troshina T.A., Shutova I.V., Novikov V.V.


Helicobacter pylori is considered an etiological agent of chronic gastritis and a number of other diseases of the gastrointestinal tract. The immune response to H. pylori is characterized by the development of both pro-inflammatory and tolerogenic reactions. Against this background, the possibility of forming autoimmune shifts is also assumed. The purpose of the present study was to conduct a comparative analysis of the state of immunity in patients with chronic gastritis in the exacerbation stage associated with and not associated with H. pylori infection. There were used whole peripheral blood (n = 50) and serum (n = 49) samples from 162 patients with primary chronic gastritis at the exacerbation stage, in which the presence or absence of H. pylori DNA was tested by real-time PCR in gastric juice. In the peripheral blood of patients, the relative content of CD4+FoxP3+ cells (T regulators) and CD4+CD161+ cells (IL-17 producing cells) was evaluated using flow cytofluorometry and monoclonal antibodies method, the level of mRNA FoxP3 and mRNA IL-17A was determined using real time RT-PCR, and the concentration of IL-2 and IL-23 was determined using enzyme immunoassay. It has been shown that in H. pylori-infected patients with chronic gastritis in the exacerbation stage in comparison with patients not infected with H. pylori, the content of CD4+FoxP3+ cells, CD4+CD161+ cells does not change in the blood, also with the level of mRNA FoxP3 and mRNA IL-17A. Since the equilibrium between the populations of Th17 cells and T regulators is modulated by IL-2, which is important for generating the population of T regulators, but inhibits polarization of the immune response towards Th17 cells, we conducted a comparative assessment of the serum IL-2 level in patients with chronic gastritis. All patients showed an increase in IL-2 content in comparison with the norm. In this case, the concentration of IL-2 in the blood of infected H. pylori patients was statistically significantly higher than in H. pylori-uninfected patients. An important regulator of the function of Th17 cells is also IL-23, which induces the differentiation of naive T lymphocytes into Th17 cells involved in inflammatory and autoimmune reactions. In this regard, we determined the level of this cytokine in the blood of patients with chronic gastritis. Multiple increase of IL-23 concentration in comparison with normal level and higher content of IL-23 in H. pylori-infected patients in comparison with uninfected patients were revealed. On the basis of the obtained data, it can be concluded that an increase in the concentration of IL-23 does not exclude the possibility of forming autoimmune shifts with its participation in persons with helicobacter infection, but the issue requires further study.

Russian Journal of Infection and Immunity. 2022;12(2):306-314
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Genetic polymorphisms of helicobacter pylori clinical isolates in St. Petersburg, Russia

Svarval A.V., Starkova D.A., Ferman R.S., Narvskaya O.V.


Introduction. Helicobacter pylori was proved to be the principal causative agent of gastroduodenal disorders in human. Although Russian Federation is among the countries with a high prevalence of H. pylori infection (60–90%), currently there is a very limited number of studies evaluating H. pylori genotypes in Russia. Objective. Based on the assessment of virulence-associated cagA, oipA, and vacA genes, our study was aimed to determine H. pylori genotypes associated with the clinical outcomes in patients with H. pylori infection in St. Petersburg, Northwest Russia. Materials and methods. Using PCR for the detection of cagA, oipA, and vacA s, m, i allelic variants, we analyzed 61 H. pylori isolates isolated and cultured from biopsies collected during endoscopy of patients with chronic gastritis (G), duodenal ulcer (DU), and gastric cancer (GC). Results. The genetic diversity of H. pylori clinical isolates has been revealed (HGDI 0.88): 41 (67%) of 61 H. pylori isolates were cagA-positive, 38 (62%) — oipA-positive. The proportions of cagA+ isolates differed in patients with G (56.7%) and DU (80.9%) (p = 0.06). The s, m, and i allelic variants of the vacA gene were detected in all strains, although the vacA s1 allele was significantly dominant in patients with DU (95.2%) rather than with G (64.9%) (p = 0.01). The vacA alleles m1 and i1 in the isolates from patients with G and DU were found in almost equal proportions: 45.9% and 42.8% for m1 allele, 45.9% and 47.6% for i1 allele, respectively. Seven isolates (11.5%) were positive for different mixed combinations of vacA alleles s, m, and i. Noteworthy, all vacA s2 strains were cagA-negative and had the m2 allele. OipA+ strains were found in almost equal proportions in patients with G (62.2%) and DU (57.1%) (p = 0.71). All three cagA- and oipA-positive isolates from patients with GC carried vacA s1/m1/i1 alleles. Different combinations of virulence-associated determinants constituted 17 genetic profiles. The most common combined genotype cagA+/oipA+/vacA s1/m1/i1 comprised 18 (29.5%) H. pylori isolates. Conclusion. We have determined predominant genotypes in the H. pylori population in the Northwest of Russia. The significant association between vacA s1 genotype of the pathogen and clinical manifestations of H. pylori infection has been established in our study.

Russian Journal of Infection and Immunity. 2022;12(2):315-322
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Characteristics of cellular and humoral immunity parameters in patients with mechanical jaundice, caused by cholangiocarcinoma

Smirnova O.V., Gubanov .G., Kasparov E.V., Darenskaya M.A., Kolesnikova L.I., Kolesnikov S.N.


In the modern world, obstructive jaundice caused by developing a malignant disease — cholangiocarcinoma, poses a significant medical and social problem in economically developed and in developing countries. The aim of this study was to examine parameters of cellular and humoral immunity in patients with obstructive jaundice caused by cholangiocarcinoma before and after surgical intervention. There were enrolled 56 patients with obstructive jaundice caused by cholangiocarcinoma (stages T2-3N0-1M0) and 90 age-matched apparently healthy volunteers. Cellular immunity parameters were studied by using an FC500 flow cytometer (Beckman Coulter, USA). The parameters of humoral immunity were assessed by measuring level of serum immunoglobulins A, M, G, E by using enzyme-linked immunosorbent assay kits manufactured by Vector-Best (Russia). The results were statistically analyzed using the Statistica v. 12.0 software (StatSoft Inc., USA). According to the study results, in patients with obstructive jaundice caused by cholangiocarcinoma, there was revealed activation of humoral immunity due to increased serum level of IgA, IgG, IgE with a profoundly depressed some arms of cellular immunity contributing to the imbalanced work of the entire immune system. The imbalance in the cellular arm of immune system was manifested by decreased count of T helper and increased cytotoxic T cell subsets as well as decline in the CD4+/CD8+ T cell ratio. An increased count of cytotoxic T lymphocytes points at lowered T cell immunity and existence of a cytotoxic effect at the cellular level. A decrease in the count of pan-marker-positive T lymphocytes indicates about generally reduced activity of the T cell arm due to altered T cell function and, as a result, affected antigen-presenting function in immune cells. The development of T cell immunodeficiency due to T-cell apoptosis confirms upregulated expression of immunomarkers CD38+, CD95+. An increased serum level for some immunoglobulins suggests developing imbalance in the humoral immunity, whereas rise in the circulating immune complexes indicates about pronounced body intoxication caused by obstructive jaundice due to hyperbilirubinemia and disintegration of tumor cells. Application of surgical correction of obstructive jaundice contributed to normalizing parameters of cellular and humoral immunity, resulting in immunocorrective effect.

Russian Journal of Infection and Immunity. 2022;12(2):323-330
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Comparative characteristics of the nasal mucosa microflora at different level of allergic inflammation in the respiratory tract

Lazareva A.M., Smirnova S.V., Kolenchukova O.A.


In the modern world, allergic respiratory diseases hold a huge place among all chronic diseases. The annual increase in the prevalence of allergic rhinitis and bronchial asthma among the global population makes relevant studies underlying their pathogenesis. Changes in the nasal mucosa alter its most important function — protection from aggressive environmental factors — allergens and pollutants. Inflammatory processes in the nasal cavity interfere with the normal mucosa functioning as a non-specific barrier, and facilitate their further penetration into the macroorganism. Objective of the study is to provide a comparative microbiological characteristic of the nasal mucosa of patients with respiratory allergies of various origin and level of respiratory tract damage. Patients with respiratory allergies aged 23 to 51 years old as well as sex- and age-matched apparently healthy subjects (n = 120) were examined. The study groups were as follows: atopic rhinosinusitis (AR, n = 28), atopic bronchial asthma (ABA, n = 28), polyposis rhinosinusitis (PRS, n = 68), and asthmatic triad (AT, n = 28). Diagnostics were carried out by an allergist-immunologist as well as an otorhinolaryngologist. Isolation of microorganisms was carried out by placing them on nutrient differential diagnostic media. Seeding was carried out by using the sector method. The culture media were incubated in a thermostat at 37°C for 48 hours. Statistical processing was performed using the Statistica 7.0 software package. The study sample is described by calculating median as well as 25 and 75 percentiles. The normality distribution was checked by using the Kolmogorov–Smirnov method. The significance of differences between parameters of independent samples was assessed by using the nonparametric Mann–Whitney test. Dominance of opportunistic microorganisms in respiratory atopy (AR, ABA) relative to respiratory pseudoatopia (PRS, AT) was noted. The increased number of bacteria from the family Enterobacteriaceae and Enterococcus on the nasal mucosa characterizes dysbacteriosis, emphasizing the greatest importance of these families in the initiation of allergic pathology in the upper and lower respiratory tract during atopy. A distinctive intergroup feature is a high concentration of the Enterobacteriaceae family members in AR vs. PRS as well as microorganisms of the genus Enterococcus in ABA vs. AT. Thus, regardless of the cause of inflammation, allergic rhinosinusitis and bronchial asthma were featured with a pronounced dysbacteriosis due to rise in the opportunistic microflora on the nasal mucosa compared to the control group.

Russian Journal of Infection and Immunity. 2022;12(2):331-338
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The role of increased intestinal permeability markers in developing urinary tract infection in children of the first three years of life

Sergeeva E.V., Nee A., Shumatova T.A., Bykova O.G., Prikhodchenko N.G., Zernova E.S.


Urinary tract infection (UTI) is one of the urgent problems in pediatric nephrology and pediatrics. Despite numerous works devoted to the study of pathogenetic mechanisms and development of new diagnostic measures in patients with urinary tract infection, many questions on pathogenesis have not yet been clearly elucidated. Considering that non-specific symptoms prevailing in the disease clinical picture in children of the first three years of life, it is necessary to search for reliable, early, non-invasive methods for diagnosing urinary tract infections. Purpose of the study is to determine diagnostic and pathogenetic significance of proteins that bind fatty acids as well as zonulin in diagnosis of urinary tract infection in children of the first three years of life. Materials and methods. There were examined 120 children, aged from 29 days of life to 2 years 11 months and 29 days inclusive with urinary tract infection. Control group — 30 healthy children. All children were tested for serum level of proteins that bind fatty acids L-FABP and I-FABP, and the level of I-FABP, L-FABP and zonulin was measured in urine by enzyme-linked immunosorbent assay. Results. In the blood serum of children with urinary tract infection, the levels of L-FABP and I-FABP were significantly increased compared with those in children of the control group (L-FABP — 753.94±26.16 ng/ml vs. 148.7±19.6 ng/ml, I-FABP — 92.97±1.41 ng/ml vs. 18.03±3.03 ng/ml, respectively, p < 0.001). Fractions of urine proteins L-FABP and I- FABP in sick vs. healthy children were also determined at a higher level (6.96±0.19 ng/ml and 1.01±0.25 ng/ml vs. 0.37±0.01 ng/ml and 0.1±0.02 ng/ml, respectively, at p < 0.001). The level of urine zonulin was increased (2.84±0.12 ng/ml) in sick vs. healthy children (0.17±0.04, p < 0.05). Conclusion. The study allowed to identify early markers of kidney and urinary tract damage (L-FABP, I-FABP, ZO) involved in developing inflammatory bacterial process, whereas measuring urine I-FABP, L-FABP, zonulin level can be used for non-invasive UTI diagnostics in infants and young children.

Russian Journal of Infection and Immunity. 2022;12(2):339-346
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Gene polymorphism in blood coagulation system and folate cycle affecting heart condition in patients with hemorrhagic fever and renal syndrome

Manakhov K.M., Sarksyan D.S., Dudarev M.V., Chernobrovkina M.S., Pribytkova P.Y., Filimonova S.V.


One of the typical manifestations of hemorrhagic fever with renal syndrome (HFRS) is a damage to the cardiovascular system. The most promising direction of studying the causes of cardiac complications in HFRS should be considered the genetic patient characteristics, particularly taking into account the disease pathogenesis, study of polymorphism of the genes in the blood coagulation system and the folate cycle. The aim of the study was to find out an effect of polymorphism of the blood coagulation system and folate cycle genes on heart damage in hemorrhagic fever with renal syndrome. A case-control study was conducted by enrolling 19 patients in the 2019 summer–autumn period at the Republican Clinical Infectious Hospital in the City of Izhevsk. The study of polymorphism of the blood coagulation system and folate cycle genes was performed by using a set of reagents RealBest-Genetics Hemostasis (12) on the CFX96 amplifier (Bio-Rad, USA). DNA was extracted from peripheral blood leukocytes with reagents RealBest Extraction 100. Transthoracic echocardiography was performed on a Vivid 7 Dimension ultrasound scanner (GE Healthcare, USA) with a matrix sector sensor M4S with a phased array at scanning frequency of 1.5–4.3 MHz. Statistical analysis was performed using Statistica 12, IBM SPSS 22. The group parameters were calculated and depicted as median and interquartile range (ME [Q25; Q75]). Comparison of such parameters was carried out by using the Mann–Whitney criterion. Comparison of the frequency distribution for genotypes and alleles in the study groups was carried out using the criterion χ2. The association of alleles/genotypes with a predisposition to detectable changes was assessed by the risk ratio (OR) additionally calculating 95% confidence interval (CI). The p ≤ 0.05 was considered as statistically significant. During the study, 7 patients were found to have floating echoes on the aortic valve in the outlet of the left ventricle — signs of thrombotic endocarditis. In the group of patients with signs of thrombotic endocarditis, there was revealed a higher frequency of the allele A for the F7:10976 G/A gene compared to patients lacking signs of thrombotic endocarditis (p = 0.0357). All study patients had a normal left ventricular ejection fraction (more than 50%), but during the speckle-tracking study assessing the index of averaged peak longitudinal contractility (GLPS AVG), 11 patients with impaired myocardial contractility were identified. In patients with decreased GLPS AVG, the genotype G/G of the FGB:-455 G/A gene was detected more often compared to patients with preserved myocardial contractility (p = 0.0397). In 8 patients, signs of grade 1 diastolic left ventricular dysfunction were revealed, the prognostic importance of the gene polymorphism related to the blood coagulation system and folate cycle in developing this complication has not been determined.

Russian Journal of Infection and Immunity. 2022;12(2):347-356
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Crimean-Congo hemorrhagic fever in the North Caucasian Federal District: overview of the epidemiological situation and improvement of morbidity forecasting method

Prislegina D.A., Maletskaya O.V., Dubyanskiy V.M., Platonov A.E.


This article is dedicated to analyzing epidemiological situation of Crimean-Congo hemorrhagic fever in the subjects of the North Caucasian Federal District (from 2005 to 2021) and developing a new approach to improve epidemiological forecasting by using an in-progress «prognostic» model. The study is comprehensive, using epidemiological methods and mathematical statistics. The epidemiological analysis was carried out based on information from the databases on the incidence rate for Crimean-Congo hemorrhagic fever presented as a project and maps of infectious disease focus epidemiological examination. The «prognostic» morbidity model is developed based on Bayes’ theorem and Wald’s sequential statistical analysis. The factors information calculation was carried out by using the Kullback method. The value of climatic factors was retrieved from the database of the Center for Collective Use “IKI-monitoring” of the Space Research Institute of the Russian Academy of Sciences. The data obtained indicate that the majority of patients with Crimean-Congo hemorrhagic fever within the studied long-term period in the Stavropol Territory (629) and the Republic of Dagestan (46) were revealed. Isolated cases in the Kabardino-Balkarian Republic (2), the Karachay-Cherkess Republic (3) and the Republic of Ingushetia (2) were noted. Infection by the Crimean-Congo hemorrhagic fever causative agent via the transmission mechanism occurred mainly during the care after farm animals in 59.4%. The prevalence of moderate forms of Crimean-Congo hemorrhagic fever (79%) was noted, with hemorrhagic manifestations (over the last five years) observed almost in half of the patients. The proportion of correct preliminary diagnoses during patient hospitalization was 49%. While testing the «prognostic» model in 2021 particularly in the Stavropol Territory, a complete exact coincidence for predicted and the actual data was obtained for 11 districts (42.3%). False positive (38.5%) and overestimated (11.5%) data at this stage of the study do not significantly reduce the predictive value of the model, since they often reflect registered infection case that occurred at the patient’s place of residence in another administrative region, underdiagnoses of mild forms of Crimean-Congo hemorrhagic fever in medical institutions or high efficiency of preventive measures against ticks measures carried out before the beginning of the epidemic season in individual municipal districts. False negative results were 7.7%. Thus, the results of the analysis evidence about a need to improve the training of medical personnel for the timely detection of patients with Crimean-Congo hemorrhagic fever and to enhance the effectiveness of preventive measures against ticks. The results of testing the “prognostic” model confirm the feasibility and hold promise to continue the study.

Russian Journal of Infection and Immunity. 2022;12(2):357-365
pages 357-365 views

The epidemiological and clinical study of patients with clostridium difficile enterocolitis in Varna, Bulgaria

Lyutsova E.D., Gospodinova M.D.


Introduction. Clostridium difficile infections (CDI) remain a global health concern. Currently, no unified approach to the diagnostics and determining severity of these infections despite their high urgency throughout the world was proposed. The aim of the study is to identify risk factors for CDI, investigate clinical and epidemiological features of the disease course and potential for using the ATLAS scale to assess its severity. Materials and methods. 36 CDI patients hospitalized at the Infectious Disease Clinic of Varna were analyzed during the period from January 2018 until June 2019. Clinical and epidemiologic study was conducted. The diagnosis was made by using a rapid immunochromatographic test; CDI patient stratification was performed by ATLAS scoring system. Results and discussion. Within the aforementioned period, 1100 patients were hospitalized at the Infectious Disease Clinic of Varna, and CDIs were reported in 3,3% of cases. The most affected were elderly individuals (the mean age was 69,8±16,4 years old) most of whom were females (92%) with only 6% of males. The following risk factors were investigated: comorbidities — 32 patients (88,89%), recent hospitalization — 19 patients (52,78%), antibiotic use — 31 patients (86,11%). Twenty-four patients (66,67%, ATLAS score ≤ 4 points) had mild CDI, whereas moderate form of CDI was observed in 12 patients (33,33%). No severe CDI or death were observed. The characteristic clinical presentation included fever, diarrhea and abdominal cramping. The treatment was implemented according to the national and international recommendations by using oral Metronidazole for 11 patients (30,56%), Vancomycin — for 12 patients (33,33%), or both — for 13 patients (36,11%). Conclusion. Patients at risk with symptoms of enterocolitis and a history of antibiotic use or hospitalizations should be screened for the presence of toxin-forming strains of Clostridium difficile. According to the European Centre for Disease Prevention (ECDC) the diagnostic yield of CDI may be increased by using two-step protocol, whereas the ATLAS score system may be a useful tool for routine evaluation of patients with CDI.

Russian Journal of Infection and Immunity. 2022;12(2):366-372
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An association between low vitamin D status and childhood pneumonia severity in hospitalized bulgarian patients

Rimpova N., Valcheva V., Tsakova A., Shivachev H., Iliev D.


Lower respiratory tract infections are among the most important causes of morbidity and mortality in the pediatric population worldwide. Despite advances in treatment and prevention, childhood pneumonia is the major reason for hospital admissions and remains a leading cause of death claiming an estimated 800 000 children’s lives in 2018. Globally, over 1.23 million children died of pneumonia before reaching their 5th birthday — the equivalent of over 3400 deaths per day worldwide. There is growing evidence that vitamin D plays an important role in the immune system by modulating both innate and adaptive immunity. Vitamin D is an additional factor in the inflammatory response regulation. Its action is mediated via the vitamin D receptor (VDR), which is present in almost all types of immune cells, including activated CD4+ and CD8+ cells, B cells, macrophages, neutrophils and dendritic cells. Vitamin D deficiency is associated with decreased host defenses against infections. Therefore, our aim was to investigate whether low vitamin D status was a risk factor for pneumonia complications, usage of multiple antibiotics and prolonged hospital stay among hospitalized pediatric patients with community-aquired pneumonia. Total of 200 children (102 healthy controls and 98 with severe pneumonia) from 11 days to 17 years old were included in the study. Cases with severe pneumonia were subdivided into groups with and without complications (36 and 62, respectively). Electrochemiluminescence immunoassay was used to measure the serum 25-hydroxyvitamin D levels. The control group showed lower values than the study group. Cases with complicated pneumonia had significantly lower levels whitin the range of 29.7–68.0 nmol/l, compared with 49.1–88.6 nmol/l in cases without complications. A significant negative correlation was found between vitamin D concentrations and duration of hospital stay, the number of antibiotics used for treatment, and serum levels of inflammatory markers. The low status of vitamin D is related to the severity of the disease but has not been associated with the incidence/frequency of the disease. Children with low vitamin D levels may be at higher risk of developing life-threatening complications, intensive care admissions and a higher inflammatory response.

Russian Journal of Infection and Immunity. 2022;12(2):373-380
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Impact of Candida spp. metabolites on human skin fibroblasts

Ignatova N.I., Zaslavskaya M.I., Alexandrova N.A., Orlova O.E., Melnikov V.G.


Micromycetes spp. have been increasingly involved in the etiology of infectious diseases guiding to consider them not as important as bacterial and viral pathogens. Nowadays, a lot of severe forms of candidiasis are caused by C. auris, C. albicans, whereas C. glabrata and C. krusei are of similar importance. Members of these species were selected to investigate related metabolite action on human skin fibroblasts. Candida spp. being continuously found on the epithelium and mucosal membranes resulting in to sustained interaction between microbiota and human cells. Potential to produce metabolites containing pathogenicity factors is one of the crucial events for transition to invasive candidiasis, wherein human epithelial cells build up the front line of defense barrier preventing Candida spp. invasion into deeper host tissues. The study was aimed at assessing data on metabolite effects derived from epidemiologically relevant Candida spp. on primary human skin fibroblast culture in vitro. In particular, there were analyzed Candida spp. metabolites acting on fibroblast monolayer integrity and viability in cell suspension. It was found that Candida spp. metabolites might directly cause fibroblast death so that biocidal activity was exhibited as a strain-specific feature. A direct biocidity against dermal cells was more typical for strains C. glabrata и C. krusei, less pronounced for C. albicans and very weak for C. auris. In addition, a mechanism for secretory product-related biocidal activity derived from various Candida spp. on dermal fibroblasts in vitro revealed that it resulted in fibroblasts death 1 hour after exposure that peaked at 3 hrs. Cell death was equally proceeded via apoptosis and necrosis. Of note, biocidal effect of fungal metabolites showed no correlation with Candida-related potential to cleave intercellular junctions. It was found that C. auris metabolites showing weak biocidity against some fibroblasts simultaneously resulted in more marked disruption of cell monolayer compared to other Candida spp. Perhaps, it is just a feature of C. auris that might account for its higher invasiveness potential allowing to destroy tight human tissues more effectively compared to other Candida spp.

Russian Journal of Infection and Immunity. 2022;12(2):381-385
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Species diversity among the genus Streptomyces members isolated from clinical material

Lyamin A.V., Tereshchenko V.S., Zhestkov A.V., Ismatullin D.D.


Recently, both in Russia and around the world, the number of cases detecting acid-fast microbial members from the order Actinomycetales while developing human bacterial infections has been increased. The most important pathogens in this bacterial order are the members from the families Mycobacteriaceae, Nocardiaceae, Gordoniaceae, Tsukamurellaceae, Promicromonosporaceae, Brevibacteriaceae, Streptomycetaceae. This work is devoted to analyzing prevalence and species diversity of representatives of the family Streptomycetaceae from the genus Streptomyces isolated from clinical material upon examining for tuberculosis. There were examined 865 cultures of clinical material samples while examining for tuberculosis, in which signs of growth of contaminating microflora were revealed, as well as 316 cultures of clinical material samples obtained during examination for tuberculosis, in which signs of growth of non-tuberculosis mycobacteria (NTM) were detected. The material was collected from January 2016 to January 2019. Samples with signs of growth of contaminating microflora allowed to identify 1,093 strains, samples with signs of growth of NTM — 352 strains. Among them, the number of representatives of the genus Streptomyces comprised 39 strains. All Streptomyces strains were isolated from sputum. Variety of isolated Streptomyces: S. phaeochromogenes (13 strains), S. albus (1 train), S. avidinii (1 strain), S. badius (2 strains), S. chartreusis (2 strains), S. griseus (1 strain), S. hirsutus (2 strains), S. lavendulae (3 strains), S. violaceoruber (10 strains). Species identification was not possible for 4 strains. Analyzing the data obtained, it is possible to draw a conclusion about the moderate distribution of representatives of the genus Streptomyces in pattern of contaminating microflora while examining for tuberculosis. In pattern structure of isolated microorganisms, Streptomyces accounted for 3.3%. Among the microflora isolated from culture with signs of NTM growth, Streptomyces was presented by single strains. However, it should be noted that Streptomyces was the dominant group among acid-resistant actinomycetes in pattern of contaminating microflora and accounted for 38.3%. Taking into account the fact that a significant proportion of them were isolated as microbial associations, it can be concluded that Streptomyces turned out to be classical contaminants in this case. Nevertheless, we believe that the isolation of Streptomyces in association with clinically significant NTMs can be considered as an unfavorable factor due to the fact that antibiotic resistance genes are widespread among Streptomyces and may be transmitted to other types of microorganisms from the group of acid-resistant actinomycetes, including mycobacteria. Thus, the clinical material examining for tuberculosis is an interesting research object from which various representatives of acid-fast actinomycetes, including Streptomyces, can be isolated.

Russian Journal of Infection and Immunity. 2022;12(2):386-390
pages 386-390 views

Obtaining immunodiagnostic preparations from Toxocara canis antigens for serodiagnostics of toxocariasis in human

Kanina I.V., Novak A.I., Novak M.D., Evdokimova O.V.


Toxocariasis is a human helminthic invasion that has a wide range of hosts with epizootic distribution. The populational seropositivity in countries with a temperate climate comprises about 37%, whereas in regions with tropical climate — up to 92%. Almost all age groups of the population are at risk of invasion by toxocars. The immunological method currently retains diagnostic significance for toxocariasis, because the reaction of immune system against helminths is accompanied by developing sensitization, and techniques as well as methods of collecting clinical material to identify the migratory form of toxocarosis in humans are time-consuming and invasive. The purpose of this study is to develop an immunobiological preparation based on excretory-secretory antigens from Toxocara canis larvae for serodiagnostics of larva migrans syndrome in human by using enzyme-linked immunoassay (ELISA). Antigens were obtained from Toxocara canis larvae by culturing its eggs isolated from the uterus of female nematodes in the glutamine-supplemented medium. The preparation was purified from ballast substances by centrifugation at 8000 g for 20 minutes followed by filtration through microfiltration membrane with a pore diameter of 0,05–0,15 microns, type MFAS-P-1 (manufactured by CJSC STC Vladipor). Blood serum of student volunteers from countries with high incidence rate of toxocariasis were tested to detect T. canis-specific antibodies. ELISA with commercial antigens Toxocara-IgG-ELISA-BEST kit was used for selection of seropositive and seronegative sera also used as a control. Diagnostic antigenic preparations with different protein concentrations were prepared to examine seropositive sera for determining optimal dose of the antigenic drugs. Results. ELISA with standard test kit allowed to detect Toxocara-IgG antibodies in 20 sera (8%) from 250 samples, what indicates about antigenic stimulation of the immune system by helminths and suspected former disease. Analyzing experimental samples allowed to find the number of seropositive data correlated with antigenic protein concentration in preparations: at a concentration of 1,96 μg/ml 5,2% of positive results were detected, 1,71 μg/ml — 3.2%, 0.33 μg/ml — 0.8% (Pearson’s correlation coefficient 0,94). The number of positive sera detected with commercial antigen in ELISA kit was identical to that of positive sera detected by an experimental antigen sample with a protein concentration of 2,49 μg/ml. Thus, the immunodiagnostic preparations obtained by the experimental method based on the excretory-secretory antigens from Toxocara canis are characterized by high sensitivity and can be used to detect Toxocara-IgG antibodies in ELISA. The antigen preparation protein concentration of at least 2.49 μg/ml is optimal and correlates whit sensitivity of the commercial antigen of the standard ELISA.

Russian Journal of Infection and Immunity. 2022;12(2):391-396
pages 391-396 views

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