Rotavirus-specific B cells induced by recent infection in adults and children predominantly express the intestinal homing receptor α4β7

In vivo replication of rotaviruses is generally limited to enterocytes. Because of this restriction, most blood circulating rotavirus-specific B cells are hypothesized to originate in Peyer's patches and should express the intestinal homing receptor α4β7. To test this hypothesis in humans, we used a flow cytometry assay that identifies antigen-activated (IgD-) B cells (CD19⁺) that express surface rotavirus-specific immunoglobulin. With this assay we could detect rotavirus-specific B cells in both children and adults with an acute rotavirus (RV) infection. Staining with an anti-α4β7 monoclonal antibody, we could determine that B cells that express rotavirus-specific surface immunoglobulin predominantly express α4β7. The response of rotavirus-specific antibody-secreting cells in the peripheral blood of children and adults with acute rotavirus infection was also studied by ELISPOT. The antibody-secreting cells of children were mainly of the IgM isotype, while the antibody-secreting cells of adults were predominantly of the IgA and IgG isotype. α4β7 + and α4β7- subsets of peripheral blood mononuclear cells were purified using paramagnetic beads and then tested in the ELISPOT assay. Rotavirus-specific antibody-secreting cells were predominantly present in the α4β7+ subpopulation. The flow cytometry assay we have described will permit future studies to characterize the phenotype of virus-specific B cells and could be useful in the study of the immunogenicity and protective efficacy of RV vaccines and the identification of markers of protective immunity.