HETEROGENEITY OF VP4 NEUTRALIZATION EPITOPES AMONG SEROTYPE P1A HUMANROTAVIRUS STRAINS

We have used serotype-specific VP4 and VP7 neutralizing monoclonal ant ibodies (Nt-MAbs), as well as subgroup (SG)-specific MAbs, to characte rize by enzyme immunoassay rotavirus strains isolated from diarrheic i nfants in the city of Monterrey, Mexico, from July 1993 to March 1994. Of a total of 465 children studied, 140 were rotavirus positive, incl uding 3 patients infected with non-group A rotaviruses. The SG and VP7 (G) serotype specificities could be determined for 118 (84%) of the 1 40 rotavirus-positive stool specimens; 4 rotavirus strains were seroty pe G1 and SGII; 1 strain was serotype G2 and SGI+II; 112 strains were serotype G3 and SGII; 1 strain was serotype G3 and SGI; and none of th e strains was serotype G4. Fifty-eight specimens, representing the 13 different group A rotavirus electropherotypes detected, were chosen fo r VP4 (P) serotyping. Of these, 48 (83%) strains reacted with the P1A serotype-specific Nt-MAb 1A10. None of the strains reacted with the se rotype P2-specific Nt-MAbs tested. Not all viruses that reacted with N t-MAb 1A10 were recognized by Nt-MAbs 2A3 and 2G1, which also recogniz e P1A strains, indicating heterogeneity of neutralization epitopes amo ng serotype P1A human rotaviruses. This heterogeneity could be relevan t for the specificity of the VP4-mediated neutralizing antibody immune response and indicates the need for antigenic characterization, in ad dition to genomic typing, of the VP4 proteins of circulating human rot avirus field strains.