Humoral immunity features in mumps patients

Mumps is an anthroponotic viral disease causing severe complications such as aseptic meningitis, orchitis, and viral encephalitis. The widespread introduction of a two-dose mumps vaccination schedule has dramatically reduced the incidence of this infection. However, in the last decade, there have been observed outbreaks of mumps emerging in twice-vaccinated individuals. In the latter, a loss of antibodies has been demonstrated 7-10 years following the second dose vaccine application. The study was aimed to investigate characteristics of the humoral immune response in patients with mumps. For this, paired serum samples collected 10-20 days apart from 147 patients diagnosed with mumps aged 1 to 63 years were analyzed by using enzyme-linked immunosorbent assays using the VectoParotit-IgM and VectoParotit-IgG kits. The data were processed by applying nonparametric statistics: (Me (Q25-Q75)), differences considered significant at p < 0.05. IgM antibodies can be detected in the first week after disease onset, but not in all unvaccinated patients. In 10.88% of patients, IgM antibodies emerged 2-3 weeks only after the onset, in 72.11% IgM antibodies were detected in both serum samples, whereas in 17.01% of patients, no anti-mumps IgM antibodies were found. Patients were divided into 3 groups while analyzing specific IgG antibody dynamics and. In group 1 (n=20), individuals with low IgG levels and ~30% antibody avidity level showed no change in the second sample, comprised individuals tested through contact or with asymptomatic boosting. In group 2, 28 individuals with low IgG antibody titers and a four-fold increase in the second sample, had significantly elevated IgM level and low avidity index referred to subjects with a primary immune response to the infection. In group 3, 37 individuals had high mumps antibody titers in the first sample and a four-fold increase in the second sample, with significantly increased avidity index, comprising subjects with a secondary immune response to mumps. The patterns identified should be taken into account while analyzing laboratory parameters of humoral immunity in patients with mumps and contacts from the site of infection.