IDENTIFICATION OF A T-HELPER CELL EPITOPE ON THE ROTAVIRUS VP6 PROTEIN

In this work, we have studied the T-helper (Th)-cell response against rotavirus, in a mouse model. Adult BALB/c mice were inoculated parente rally with porcine rotavirus YM, and the Th-cell response from spleen cells against the virus and two overlapping fragments of the major cap sid protein VP6 (VP6(1-192) and VP6(171-397)) were evaluated in vitro. The Th cells recognized the YM virus and the two protein fragments, s uggesting that there are at least two Th-cell epitopes on the VP6 mole cule. To study the specificity of Th cells against VP6 at the clonal l evel, we established two Th-cell hybridomas cross-reactive for the VP6 protein of rotavirus strains YM and SA11. Both hybridomas recognized the VP6(171-397) polypeptide, and a synthetic peptide comprising the a mino acids 289 to 302 (RLSFQLVRPPNMTP) of YM VP6 in the context of the major histocompatibility complex class II IE(d) molecule. The Th-cell hybridomas recognized rotavirus VP6 in a highly cross-reactive fashio n, since they could be stimulated by eight different strains of rotavi rus, including the murine rotavirus EDIM, that represent five G seroty pes and at least two subgroups. The amino acid sequence of the VP6 epi tope is highly conserved in most group A rotavirus strains sequenced s o far. On the other hand, it was found that Th cells specific for the VP6 epitope may constitute an important proportion of the total polycl onal Th-cell response against rotavirus YM in spleen cells. These resu lts demonstrate that VP6 can be a target for highly cross-reactive Th cells.