MAPPING THE SUBGROUP EPITOPES OF ROTAVIRUS PROTEIN VP6

VP6, the most abundant protein of rotaviruses, contains epitopes that allow the classification of these viruses into four subgroups (SG), de pending on the presence or absence of two epitopes called I and II. Th e subgroup-specific epitopes are conformational and appear to be prese nt on trimeric but not monomeric VP6. We have identified on VP6 some o f the amino acids that determine the reactivity of the subgroup-specif ic mAbs 255/60 and 631/9. A single amino acid mutation at positions 17 2 (Met to Ala) or 305 (Asn to Ala) was sufficient to change the subgro up specificity of the human rotavirus Wa VP6 protein from SGII to SGI/ II, since either of these mutations allowed the protein to be recogniz ed by the SGI mAb 255/ 60, while retaining its capacity to interact wi th the SGII mAb 631/9. In the case of the SGII epitope, the mutation o f two contiguous amino acids (Ala(305) Asn(306) to Asn(305) Ala(306)) in the porcine rotavirus YM VP6 protein (SGI) enabled the protein to b e efficiently recognized by the SGII mAb 631/9, while causing the YM V P6 protein to lose its capacity to interact with mAb 255/60. These res ults suggest that both subgroup mAbs interact with an antigenic domain in VP6 that is composed of at least two regions of the protein that, although distant in the linear sequence, might be in close proximity i n the structured VP6 trimer. (C) 1994 Academic Press, Inc.