Abstract
► Antibody CD4 T and B cells response to 2009 A/H1N1 pandemic vaccination in adults. ► Comparable day 0 frequency of CD4 T and memory B cells reactive to pandemic/seasonal H1N1. ► Vaccination expand pandemic- and seasonal-specific CD4+ T cells and memory B cells. ► Antibodies and plasmablasts accumulating by day 8 are IgG-switched. ► By day 8 in antibodies inhibiting hemagglutination and infection rose up to 8-fold.
Protective antibody responses to a single dose of 2009 pandemic vaccines have been observed in the majority of healthy subjects aged more than 3 years. These findings suggest that immune memory lymphocytes primed by previous exposure to seasonal influenza antigens are recruited in the response to A/H1N1 pandemic vaccines and allow rapid seroconversion. However, a clear dissection of the immune memory components favoring a fast response to pandemic vaccination is still lacking. Here we report the results from a clinical study where antibody, CD4+ T cell, plasmablast and memory B cell responses to one dose of an MF59-adjuvanted A/H1N1 pandemic vaccine were analyzed in healthy adults. While confirming the rapid appearance of antibodies neutralizing the A/H1N1 pandemic virus, we show here that the response is dominated by IgG-switched antibodies already in the first week after vaccination. In addition, we found that vaccination induces the rapid expansion of pre-existing CD4+ T cells and IgG-memory B lymphocytes cross-reactive to seasonal and pandemic A/H1N1 antigens. These data shed light on the different components of the immune response to the 2009 H1N1 pandemic influenza vaccination and may have implications in the design of vaccination strategies against future influenza pandemics.