Distribution and phenotype of murine rotavirus-specific B cells induced by intranasal immunization with 2/6 virus-like particles.

Virus-like particles containing the rotavirus (RV) internal proteins VP2 and VP6 (2/6-VLP) have been shown to induce serum and fecal antibodies as well as protection in mice after intranasal administration with a mutant of E. coli toxin, LT-R192G. To better understand the origin of fecal IgA induced by this protocol, we studied the RV-specific B cell response in systemic and mucosal lymphoid tissues using a flow cytometry assay that allows quantification and phenotypic characterization of RV-specific B lymphocytes. We also assessed the RV-specific antibody-secreting cells in the spleen and intestinal lamina propria (ILP). A remarkably high frequency of RV-specific B cells was found in the respiratory lymphoid tissues and spleen, of which only a minority expressed the alpha4beta7 integrin (intestinal homing receptor). In contrast, but in accordance with alpha4beta7 expression at the induction site, a very low response was observed in intestinal lymphoid tissues (mesenteric lymph nodes and ILP), which did not increase after a second immunization. Thus, intranasal immunization with a nonreplicating antigen does not induce an important number of RV-specific B cells with an intestinal homing profile.