Integrative Characterization of Human Cellular and Serological Antibody Repertoires Elicited by Seasonal Influenza Vaccine

Vaccines convey protection by stimulating B cells to produce a diverse repertoire of antigen-specific antibody proteins for an extended period of time. While next-generation sequencing has become an invaluable tool for investigating the cellular response to influenza vaccination, a comprehensive delineation also requires an understanding of the serological repertoire through the proteomic determination of the monoclonal antibodies (mAbs) comprising the vaccine serum response. By integrating transcript- and protein-level repertoire analyses using methodologies recently developed by our laboratory (Lavinder et al., PNAS 2014; DeKosky et al., NBT 2013), we have characterized the mAbs that constitute polyclonal responses following the trivalent-inactivated 2011-2012 seasonal influenza vaccination (FluZone) in four healthy donors. Specifically, the cellular and serological IgG repertoire to each HA from three virus strains comprising the vaccine (H1, H3 and B) was determined at days 0, 28 and 180 following vaccination. Select key findings include: (1) Clonotypic diversity of B repertoires was significantly larger than H1 and H3 repertoires. (2) A significant portion of the serological response to H1 (ranging from 40% to 63%) also displays binding to H3. Recombinant expression and analysis of cross-reactive antibodies identified by the proteomic analysis of the serum revealed that such antibodies generally display high affinity (nanomolar) for both components. (3) The serum antibody repertoire to the B HA displays a great degree of polarization with the top 5% highest frequency antibody clonotypes comprising majority (59-87%) of the repertoires both at days 28 and 180. (4) Pre-existing antibodies are much more likely to be cross-reactive, while new clonotypes emerging as a result of the vaccination tend to be more strain-specific. A number of serum antibodies were expressed recombinantly and analyzed for antigen specificity, HA inhibition and virus neutralization. The prevalence and relative abundance of neutralizing antibodies as a function of the magnitude and clonal diversity of the polyclonal response to the vaccine components will be presented.