HUMORAL IMMUNITY PATTERNS BASED ON ANTIBODY REACTIVITY TO ROTAVIRUS ANTIGENS IN BRAZILIAN CHILDREN UNDER 5 YEARS OF AGE

The age distribution of antibody to simian rotavirus (SA-11) was studi ed in serum specimens obtained from 399 children aged to 5 years and l iving in the city of Recife (PE), located in the north eastern region of Brazil. Sera were examined for group-specific rotavirus antibody us ing a blocking enzyme immunoassay (bELISA) and a hemagglutination inhi bition antibody (HIA) test, and for anti-VP2 anti-VP4 anti-VPG, and an ti-VP7 antibodies using an immunoblotting assay (IBA). Antibody preval ence was similar in all bELISA and HIA assays, showing a steep rise in the 6- to 17-month-old age groups. The results indicate early acquisi tion of antibody to rotavirus. The majority of children aged 2 to 4 ye ars had bELISA (50% to 60%) and HIA (70% to 81%) antibodies. There was an association in prevalence data obtained by HIA and bELISA with imm unoblotting (IBA), revealing four serologic profiles. Children with pr ofiles I and II (60%) respectively had HAI and ELISA antibody or HAI a ntibody alone and all had immunoprotective antibodies to VP4 and/or VP 7. These children were regarded as ''immune,'' resembling convalescent patients with a rotavirus infection. Children with profile III (4%) h ad no HIA antibody and only non-protective anti-VPG and/or VP7 antibod y, and were considered to be ''partially immune.'' Children with profi le IV (36%) had no delectable antibody and were classified as ''nonimm une.'' These children should be considered to be susceptible to rotavi rus infection, with the risk of developing clinically severe diarrhea. (C) 1996 Wiley-Liss, Inc.