Characterization of neutralizing antibodies to Far Eastern of tick-borne encephalitis virus subtype and the antibody avidity for four tick-borne encephalitis vaccines in human

We assessed the humoral immunity of 290 vaccinated persons against tick-borne encephalitis (TBE). During the first year and 2 years after the primary three vaccinations the antibodies to the Far Eastern subtype tick-borne encephalitis virus Strain P-73 were detected by neutralization test after immunization with FSME-Immune Inject vaccine (Baxter Vaccine AG, Austria) in 88.2% and 78.1% vaccinated persons. respectively: with Encepur (R) Adult vaccine (Novartis Vaccines, Germany), in 100% and 100%: with the vaccine of the Chumakov Institute of Poliomyelitis and Viral Encephalitides RAMSci (Russia), in 100% and 94.1%: with EnceVir vaccine (Russia), in 88.2% and 83.9%; and after combined vaccination, in 100% and 92.7%. The dynamics of the decrease in IgG avidity index correlated with the changes of antibody titers determined by neutralization test. After the primary vaccination course, the titers of virus-neutralizing antibodies were high (6.3-7.4 log(2)) when the avidity index of IgG antibodies were 31% and more: thus, this level call be considered immunologically significant. Two years after the primary vaccination course, the IgG avidity indexes of 60% and incite call be regarded as significant on the background of the GMT decrease of virus-neutralizing antibodies. These results allow us to recommend all four vaccines for mass vaccination and all assay of IgG avidity, along with neutralization test, for a more adequate assessment of the level of postvaccination immune response. (c) 2009 Elsevier Ltd. All rights reserved.