B-cell subsets and their surface immune globulins were investigated by flow cytometry. For class-switch assays, isolated splenic B cells were stimulated in vitro with lipopolysaccharide and interleukin-4 and antibody secretion was quantified via LEGENDplex. To study PCV13-specific responses, mice were immunized and serum antibody titers (immunoglobulin M, immunoglobulins IgG , IgG , and IgG ) were examined by enzyme-linked immunosorbent assay. Survival rates of mice were assessed within 7 days upon intranasal challenge with S. pneumoniae.
Our data demonstrate impaired IgG and IgG antibody responses towards the pneumococcal conjugate-vaccine PCV13 in SLy2-overexpressing mice. This was accompanied by reduced frequencies and numbers of BM-resident plasmablasts. In addition, we found drastically reduced counts of B-cell precursors in the BM of SLy2-Tg mice. The survival rate upon intranasal challenge with S. pneumoniae was mostly comparable between the genotypes.
Our findings demonstrate an important role of the adapter protein SLy2 in the context of adaptive antibody responses against pneumococcal conjugate-vaccine. Interestingly, deficits in humoral immunity seemed to be compensated by cellular immune effectors upon bacterial challenge. Our study further shows a novel relevance of SLy2 for plasmablasts and B-cell progenitors in the BM.