Identification of an immunodominant CD4+ T cell epitope in the VP6 protein of rotavirus following intranasal immunization of BALB/c mice.

The only lymphocytes required for protection against fecal rotavirus shedding after intranasal immunization of BALB/c (H-2(d)) mice with a chimeric rotavirus VP6 protein (MBPColon, two colonsVP6) and the mucosal adjuvant LT(R192G) are CD4(+) T cells. The purpose of this study was to identify CD4(+) T cell epitopes within VP6 that might be responsible for this protection. To make this determination, spleen cells obtained from BALB/c mice following intranasal immunization with MBPColon, two colonsVP6/LT(R192G) were stimulated in vitro with either MBPColon, two colonsVP6 or overlapping VP6 peptides containing <or=30 amino acids (AA). The numbers of memory (CD44(high)) CD4(+) T cells stimulated to produce T(H)1 and T(H)17 cytokines (IFNgamma and IL-17), as well as the quantities of these cytokines released into the cell supernatants, were then measured relative to those produced in mock-stimulated cells from the same animals. One epitope expected to be found was the VP6 14-mer AA(289-302), previously identified as a CD4(+) T cell epitope in H-2(d) mice. This was not observed but instead the only VP6 epitope identified was AA(242-259), the dominant CD4(+) T cell epitope previously reported after oral, live rotavirus immunization.