CROSSREACTIVE ANTIBODIES AND MEMORY T CELLS TO HUMAN AND ZOONOTIC INFLUENZA A VIRUSES IN VOLUNTEERS

There exists a real hazard of transferring zoonotic influenza A viruses, either swine, or avian, into human population. In such case, severity of such pandemics depends on the pathogen-specific immunity in the population. Virtual absence of such immunity in humans was declared in the literature. In this work, we assessed systemic, local, and T-cell immunity to potentially pandemic H3N2sw, H5N1, H5N2, H7N3, H7N9 and H2N2 influenza A viruses in a group of healthy adults of different age. Our results indicate that these subjects develop the following immune reactions: (i) local (i.e., nasal IgA) and cellular (CD4+ and CD8v memory T cells) heterosubtypic immunity, in absence of detectable virus-specific serum antibodies to avian influenza A viruses; (ii) Local immune responses (as nasal IgA) to human A (H2N2) virus which circulated in 1957-1968 were detected both in subjects who could be primed at that time, but also in subjects born after 1968; (iii) full-scale systemic and local immunity to potentially pandemic А (H3N2sw) swine virus was found in the group. Conclusion. In order of proper epidemiological forecasts and planning appropriate preventive measures for potentially pandemic Influenza A viruses, a regular monitoring of collective immunity should be performed using different adaptive markers. In this respect, any conclusion based on molecular analysis only could lead to considerable mistakes, and should be accomplished by the mentioned immunological studies

APPLICATION OF METHOD BASED ON IN VITRO ANTIBODY QUANTIFICATION IN PBMC SUPERNATANT SAMPLES FOR IMMUNOGENICITY EVALUATION OF A (H5N1) AND A (H5N2) POTENTIALLY PANDEMIC INFLUENZA VACCINES IN CLINICAL TRIALS

There are many data worldwide which suggest that the methods for evaluation of influenza vaccines immunogenicity should be improved. The only method validated in Russia is a HAI (haemagglutination inhibition) assay with serum samples from vaccinated volunteers. This assay does not, however, completely reflect the vaccine-induced immunological changes. In this study, we evaluated antibody immune responses to A (H5N1) inactivated influenza vaccine boosting in healthy volunteers previously primed with A (H5N2) live attenuated influenza vaccine. We compared three methods of antibody detection: (i) HAI assay with serum samples; (ii) ELISA with serum samples; (iii) ELISA with PBMC (peripheral blood mononuclear cells) culture supernates, i.e., an alternative test based on quantification of antibodies secreted by PBMC in vitro. The latter test was shown to have an advantage over other techniques in IgA and IgG antibody detection at early timepoints (day 7) after vaccination. The first two methods allowed immunogenicity assessment at day 28 after vaccination.Thus, a test based on antibody quantification in PBMC supernatant samples can be used as an alternative method for evaluation of influenza vaccines immunogenicity. This method also exhibits a better strainspecificity

INDUCTION OF LONG-TERM T AND B CELL MEMORY IMMUNITY TO INFLUENZA A VIRUS (H5N1) IN PERSONS VACCINATED WITH LIVE INFLUENZA A VACCINE (H5N2)

Over last years, a novel strategy for vaccination of people against potentially pandemic influenza A viruses is actively developed worldwide, i.e., a combined (prime-boost) vaccination. It provides  amplification (boosting) of immune response  for a vaccine  be means  of pre-vaccination (priming) with another vaccine.  We have first studied an issue of immunological consequences for people after priming  by live attenuated influenza H5N2 vaccine (LAIV), followed by a boost with inactivated influenza H5N1 vaccine (IIV) 1.5 years later. Unlike non-primed volunteers, the primed persons developed more rapid and high production of serum antibodies (of HAI-, MN-, ELISA-types) after a single vaccination with H5N1 IIV. That concerned induction of antibodies to the H5N1 vaccinal strain A, and other heterologous strains containing H5 haemagglutinin. In primed persons, the antibodies showed  higher  avidity as compared to non-primed individuals. Before inoculation with H5N1 IIV, the  IgG-antibody titers  to A virus (H5N1), and  the  levels of specific  CD4+  and  CD8+   memory T-cells proved  to be higher  in primed subjects  than  in non-primed persons.  The  boosting  effect  of H5N1 IIV did not correlate with HAI-and MN-based data on immunogenicity of priming  H5N2 live attenuated vaccine.  In general, the results obtained justify a new direction in applications of LAIVs for protection against potentially pandemic influenza virus A

CROSSREACTIVE ANTIBODIES AND MEMORY T CELLS TO HUMAN AND ZOONOTIC INFLUENZA A VIRUSES IN VOLUNTEERS

There exists a real hazard of transferring zoonotic influenza A viruses, either swine, or avian, into human population. In such case, severity of such pandemics depends on the pathogen-specific immunity in the population. Virtual absence of such immunity in humans was declared in the literature. In this work, we assessed systemic, local, and T-cell immunity to potentially pandemic H3N2sw, H5N1, H5N2, H7N3, H7N9 and H2N2 influenza A viruses in a group of healthy adults of different age. Our results indicate that these subjects develop the following immune reactions: (i) local (i.e., nasal IgA) and cellular (CD4+ and CD8v memory T cells) heterosubtypic immunity, in absence of detectable virus-specific serum antibodies to avian influenza A viruses; (ii) Local immune responses (as nasal IgA) to human A (H2N2) virus which circulated in 1957-1968 were detected both in subjects who could be primed at that time, but also in subjects born after 1968; (iii) full-scale systemic and local immunity to potentially pandemic А (H3N2sw) swine virus was found in the group. Conclusion. In order of proper epidemiological forecasts and planning appropriate preventive measures for potentially pandemic Influenza A viruses, a regular monitoring of collective immunity should be performed using different adaptive markers. In this respect, any conclusion based on molecular analysis only could lead to considerable mistakes, and should be accomplished by the mentioned immunological studies

INDUCTION OF LONG-TERM T AND B CELL MEMORY IMMUNITY TO INFLUENZA A VIRUS (H5N1) IN PERSONS VACCINATED WITH LIVE INFLUENZA A VACCINE (H5N2)

Over last years, a novel strategy for vaccination of people against potentially pandemic influenza A viruses is actively developed worldwide, i.e., a combined (prime-boost) vaccination. It provides  amplification (boosting) of immune response  for a vaccine  be means  of pre-vaccination (priming) with another vaccine.  We have first studied an issue of immunological consequences for people after priming  by live attenuated influenza H5N2 vaccine (LAIV), followed by a boost with inactivated influenza H5N1 vaccine (IIV) 1.5 years later. Unlike non-primed volunteers, the primed persons developed more rapid and high production of serum antibodies (of HAI-, MN-, ELISA-types) after a single vaccination with H5N1 IIV. That concerned induction of antibodies to the H5N1 vaccinal strain A, and other heterologous strains containing H5 haemagglutinin. In primed persons, the antibodies showed  higher  avidity as compared to non-primed individuals. Before inoculation with H5N1 IIV, the  IgG-antibody titers  to A virus (H5N1), and  the  levels of specific  CD4+  and  CD8+   memory T-cells proved  to be higher  in primed subjects  than  in non-primed persons.  The  boosting  effect  of H5N1 IIV did not correlate with HAI-and MN-based data on immunogenicity of priming  H5N2 live attenuated vaccine.  In general, the results obtained justify a new direction in applications of LAIVs for protection against potentially pandemic influenza virus A

OMOLOGICAL AND HETEROLOGICAL ANTIBODY AND T CELL IMMUNE RESPONSES TO LIVE ATTENUATED INFLUENZA VACCINE A (H5N2) AND A (H7N3)

From the beginning of 21th century outbreaks of H5, H7 and H9 avian flu are registered from time to time. These viruses are considered as one of the possible causes of the next pandemia. The development of avian influenza vaccines is one of the WHO priorities. The aim of this work was to study antibody and cellular immune responses to avian A (H5N2) and A (H7N3) live attenuated influenza vaccines (LAIVs). We examined serum antibodies (HAI assay, microneutralization assay, ELISA), local antibodies (ELISA) and virus-specific CD4+ and CD8+ central memory and effector memory T cells. Two doses vaccination of healthy volunteers with A (H5N2) and A (H7N3) LAIVs induced homological antibody and cellular immune responses (i. e. serum and local antibody conversions, virus-specific memory T cell growth). These vaccines also stimulated heterological immunity (heterological serum and local antibodies and T cells). Heterological immune response intensity depended on antigenic structure of vaccine strain and heterological virus, particularly on HA type