AVIDITY EVALUATION OF LOCAL IgA ANTIBODIES IN PERSONS IMMUNIZED WITH LIVE INFLUENZA VACCINE

At present, immunogenicity evaluation of influenza vaccines is performed by quantitative assessment of increased serum antibodies. It was, however, shown that the degree of human defense against influenza is mostly related to their qualitative characteristics, i.e., avidity (functional activity). Leading role of local immunity is demonstrated in protection against influenza. Such immunity is mediated by IgA antibodies from mucosal airways. Meanwhile, the avidity issues for local antibodies still remain open.In present study, an attempt was undertaken to evaluate post-vaccination local immunological memory for influenza A virus, according to IgA antibodies from upper respiratory secretions. Two techniques were used to evaluate antibody avidity, that were previously applied for studying this phenomenon with serum imunoglobulins, i.e., a dynamic test (measurement of antigen-antibody reaction rates), and a test with urea, a chaotropic agent (avidity is determined as a strength of antigen-antibody complex). A total of 202 persons (18 to 20 years old) were enrolled into the study.With both tests, a broad range of individual avidity values was observed for the antibodies. A significant cohort (up to 30 per cent) of persons immunized with live influenza vaccine, showed sharply increased avidity of secretory IgA antibodies by both methods, along with accumulation of these immunoglobulins after vaccination. A reverse relationship is revealed between avidity levels of these antibodies before vaccination, and increase of this parameter post-immunization. The data present convincing arguments for specific renewal of local humoral immunological memory, as induced by live influenza vaccine. The study substantiates a necessity for application of the both tests in parallel, when determining avidity of secretory IgA antibodies. (Med. Immunol., vol. 10, N 4-5, pp 423-430).