Immunostimulating effect of Yersinia enterocolitica-antigen conjugated gold nanoparticles

Yersinia enterocolitica is one of the most common causative agents of nosocomial infections and the causative agent of yersiniosis, an acute infectious disease of the gastrointestinal tract. Intestinal yersiniosis caused by Y. enterocolitica is a very pressing issue for clinical and veterinary medicine requiring use of sero- and immunodiagnostics to identify the causative agent in humans, animals and animal products. Gold nanoparticles represent one of the most popular antigen nanocarriers used for immunization and vaccination. The advantages of using gold nanoparticles as vaccine delivery vehicles are associated with their relatively small size promoting their tissue penetration, low toxicity and prolonged in vivo circulation, low cost, and reproducibility. Currently, the development of new gold nanoparticle-containing diagnostic tests and vaccines against viral, bacterial, parasitic infections, including bacteria of the genus Yersinia is underway. The aim of the study was to examine efficacy of 15 nm gold nanoparticles as an immunomodulator coupled to Y. enterocolitica-derived antigen for immunization and vaccination. Final conjugate construct was used to immunize laboratory animals. The methods of immunochemical analysis assessed sensitivity and specificity of the antibodies obtained. After that, protective effects were examined in animals vaccinated with antigen conjugates and comparison preparations. It was found that immunization with a Y. enterocolitica antigen-gold nanoparticle conjugate resulted in obtaining serum that specifically recognized yersiniosis ~35 and ~14 kDa proteins evaluated in Western blot analysis. It was shown that the specific sera cross-reacted with Y. pseudotuberculosis species, but not with intestinal group Escherichia coli, Salmonella enterica, Pseudomonas aeruginosa, Proteus vulgaris, suggesting the generic specificity of the antibodies obtained. To determine the protective effect, animals were vaccinated with antigen-gold nanoparticle conjugates and comparison preparations. Two weeks after the last vaccination, mice were challenged intraperitoneally with pathogenic strain Y. enterocolitica culture. The groups immunized with antigen-gold nanoparticle conjugate had 70—80% survival rate, whereas all control mice died. It was shown that Yersinia-derived antigen-gold nanoparticle conjugates possessed higher immunomodulating activity than unconjugated antigen. The antibodies obtained can be used for effective yersiniosis immunodiagnostics. Thus, Y. enterocolitica antigen-gold nanoparticle conjugates may serve as a basis for creating preventive vaccines.