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The prevalence and type diversity of human astroviruses (HAstV) in children with symptomatic and asymptomatic infections were determined in five localities of Mexico. HAstV were detected in 4.6 (24 of 522) and 2.6% (11 of 428) of children with and without diarrhea, respectively. Genotyping of the detected strains showed that at least seven (types 1 to 4 and 6 to 8) of the eight known HAstV types circulated in Mexico between October 1994 and March 1995. HAstV types 1 and 3 were the most prevalent in children with diarrhea, although they were not found in all localities studied. HAstV type 8 was found in Mexico City, Monterrey, and Mérida; in the last it was as prevalent (40%) as type 1 viruses, indicating that this astrovirus type is more common than previously recognized. A correlation between the HAstV infecting type and the presence or absence of diarrheic symptoms was not observed. Enteric adenoviruses were also studied, and they were found to be present in 2.3 (12 of 522) and 1.4% (6 of 428) of symptomatic and asymptomatic children, respectively.

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In Mexican children, rotavirus infection was not associated to IS; whereas a significant association was observed between adenovirus and IS. Also there was no increase in IS cases during the sharply defined fall-winter rotavirus outbreak. Observations from this controlled study suggest that natural rotavirus infection is not a risk factor for IS. This information may have implications for development of a safer and effective rotavirus vaccine.

This report is of a community-based case control study to assess whether the severity of acute diarrhea by rotavirus (RV) in young children is associated with a particular VP7 (G) or VP4 (P) RV serotype. Five hundred twenty children younger than 2 years of age with diarrhea lasting less than 3 days were age and gender matched with 520 children with no diarrhea. The G and P serotypes were determined with specific monoclonal antibodies, and the VP4 serotype specificity in a subgroup was confirmed by genotyping. Infection with a G3 serotype led to a higher risk of diarrhea than infection with a G1 serotype. Infection with a G3-nontypeable-P serotype was associated with more severe gastroenteritis than infection with a G3 (or G1) P1A[8] serotype. A child with diarrhea-associated dehydration was almost five times more likely to be infected with a G3-nontypeable-P serotype than a child without dehydration (P < 0.001). Moreover, the two predominant monotypes within serotype P1A[8] had significantly different clinical manifestations. In this study, the severity of RV-associated diarrhea was related to different P serotypes rather than to G serotypes. The relationship between serotype and clinical outcomes seems to be complex and to vary among different geographic areas.Group A rotaviruses (RVs) are the leading cause of acute diarrhea with severe dehydration, which endangers the lives of children under 2 years of age (14). An effective vaccine could prevent the death of 800,000 children per year (7,20).Antibody specificity to neutralize different RV strains has been used to classify them into serotypes, and both of the viral surface proteins, VP4 and VP7, induce neutralizing antibodies; hence, the RV serotype is dual and has been named G and P for VP7 and VP4, respectively (15,18,19). Based on VP7, 15 different RV serotypes have been classified in group A (19). Ten of these serotypes (G1 to G6, G8 to G10, and G12) infect humans, although five of them (G1 to G4 and, more recently, G9) seem to be responsible for most infections (19,24,29,35), while serotype G5 is emerging as epidemiologically important in Brazil (16,22). At least 21 different types of VP4, P [1] to P [21], have been defined by genomic analysis (hybridization and sequencing) (19). Ten of these P types have been found among human RV strains and correspond to specific serotypes or subtypes of VP4, as was determined by neutralization assays with monospecific hyperimmune sera directed against this protein (19). Two of these serotypes (subtypes A and B of serotype P1 and subtype A of serotype P2) are the most frequent among human RV strains (11,26). Recently, two research groups reported the isolation of the first specific monoclonal antibodies (MAbs) that recognize different reference strains of serotypes P1A, P1B, and P2A (5, 25). Coulson (4) introduced the term "monotype" to define the intraserotypic RV variants, which differ in their reactivities with a given MAb. Thus, a previous study identified five monotypes of serotype P1A [8] according to their reactiv...

In the present investigation we characterized the antigenic diversity of the VP4 and VP7 proteins in 309 and 261 human rotavirus strains isolated during two consecutive epidemic seasons, respectively, in three different regions of Mexico. G3 was found to be the prevalent VP7 serotype during the first year, being superseded by serotype G1 strains during the second season. To antigenically characterize the VP4 protein of the strains isolated, we used five neutralizing monoclonal antibodies (MAbs) which showed specificity for VP4 serotypes P1A, P1B, and P2 in earlier studies. Eight different patterns of reactivity with these MAbs were found, and the prevalence of three of these patterns varied from one season to the next. The P genotype of a subset of 52 samples was determined by PCR. Among the strains characterized as genotype P[4] and P[8] there were three and five different VP4 MAb reactivity patterns, respectively, indicating that the diversity of neutralization epitopes in VP4 is greater than that previously appreciated by the genomic typing methods.

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