Antigenic and genomic diversity of human rotavirus VP4 in two consecutive epidemic seasons in Mexico.

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 G3 was found to be the prevalent VP7 serotype during the first year, being superseded by serotype G1 strains during the second season.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.

Heterogeneity of VP4 neutralization epitopes among serotype P1A human rotavirus strains.

We have used serotype-specific VP4 and VP7 neutralizing monoclonal antibodies (Nt-MAbs), as well as subgroup (SG)-specific MAbs, to characterize by enzyme immunoassay rotavirus strains isolated from diarrheic infants in the city of Monterrey, Mexico, from July 1993 to March 1994. Of a total of 465 children studied, 140 were rotavirus positive, including 3 patients infected with non-group A rotaviruses. The SG and VP7 (G) serotype specificities could be determined for 118 (84%) of the 140 rotavirus-positive stool specimens; 4 rotavirus strains were serotype 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 the strains was serotype G4. Fifty-eight specimens, representing the 13 different group A rotavirus electropherotypes detected, were chosen for VP4 (P) serotyping. Of these, 48 (83%) strains reacted with the P1A serotype-specific Nt-MAb 1A10. None of the strains reacted with the serotype P2-specific Nt-MAbs tested. Not all viruses that reacted with Nt-MAb 1A10 were recognized by Nt-MAbs 2A3 and 2G1, which also recognize P1A strains, indicating heterogeneity of neutralization epitopes among serotype P1A human rotaviruses. This heterogeneity could be relevant for the specificity of the VP4-mediated neutralizing antibody immune response and indicates the need for antigenic characterization, in addition to genomic typing, of the VP4 proteins of circulating human rotavirus field strains.

Diversity of rotavirus serotypes in Mexican infants with gastroenteritis.

One hundred thirty-two stool specimens from infants with rotavirus gastroenteritis hospitalized in two Mexican cities (Mexico City and Mérida) were examined by serotype- and subgroup-specific enzyme immunoassays. Among them, 38 (29%) were serotype 1, 15 (11%) were serotype 2, 13 (10%) were serotype 3, 22 (17%) were serotype 4, none was serotype 5 or 6, and 44 (33%) could not be serotyped. By subgrouping, 121 specimens were characterized as follows: 24 (18%) were subgroup 1, 97 (74%) were subgroup 2, and none had both subgroup specificities. While serotype 1 rotavirus predominated in the Mexico City area for 4 consecutive years (1984 to 1987), serotype 4 predominated in Mérida during the single epidemic season studied (1985). These data demonstrate that all four primary human rotavirus serotypes circulated in Mexico, with serotype 1 being the most prevalent. The seroneutralization responses of 14 of the 22 patients infected with serotype 4 strains had been previously studied. Of these 14 infants, 11 appeared to have primary infections, as indicated by absence of neutralizing antibodies in the acute-phase sera and their young age (8 months on average) at the time of illness. Seven patients seroresponded to serotypes 1 and 4; two seroresponded to serotypes 1, 3, and 4; three seroresponded to serotype 1; and two had low-level seroresponses to serotype 3 or 4. These data indicate that heterotypic neutralizing antibody responses occur frequently following infection with serotype 4 rotaviruses.

Reactogenicity and antigenicity of rhesus rotavirus vaccine (MMU-18006) in newborn infants in Venezuela.

The reactogenicity and antigenicity of the rhesus rotavirus vaccine, strain MMU18006, developed at the Laboratory of Infectious Diseases (National Institute of Allergy and Infectious Diseases, National Institutes of Health) were examined in a double blind, placebo-controlled study of 40 newborn infants in Caracas, Venezuela. The children were observed for the first few days after birth in the hospital nursery and by home visits for 10 days after vaccination to detect any adverse reactions. No reactions could be attributed to the vaccine. Serologic responses to the vaccine were evaluated in paired sera obtained at birth (cord blood) and 4 weeks after vaccination. Serologic responses to the vaccine were not observed by complement fixation, neutralization or a rhesus rotavirus VP7 epitope-specific competition assay. However, such responses were found in 9 of 14 tested infants by an immunoglobulin A-specific enzyme-linked immunosorbent assay. Seventeen of the 20 vaccinees also shed rhesus rotavirus vaccine in stool during the postvaccination period.

Evidence of immunity induced by naturally acquired rotavirus and Norwalk virus infection on two remote Panamanian islands.

For better understanding of the role of humoral immunity in ameliorating infections with rotavirus (RV) and Norwalk virus (NW), 305 Cuna Indians living on two isolated islands located off Panama's Carribean coast were surveyed daily for diarrhea over a seven-month period. Nine (8%) of 108 persons with a baseline RV antibody titer of greater than 1:4 developed RV infection compared with 70 (46%) of 151 persons with a baseline RV antibody titer of less than 1:4 (P less than .001). Thirty-eight (25%) of 151 persons of all ages with baseline RV antibody titer of less than 1:4 had at least one episode of RV diarrhea compared with 6 (6%) of 108 persons who had baseline RV antibody titers of greater than 1:4 (P less than .001). Thirty-two (47%) of 68 persons of all ages who had a baseline NW antibody titer of less than 1:100 developed NW infection compared with 30 (13%) of 237 persons with a baseline NW titer of greater than 1:100 (P less than .001). The high NW and RV infection rates and the excellent levels of protection provided by specific preexisting humoral antibody to these agents should promote activities aimed at developing vaccines for preventing these infections.

Infectious disease patterns in the Waorani, an isolated Amerindian population.

The Waorani Indians of eastern Ecuador provide a unique opportunity for studying exposure of an isolated human population to various infectious disease agents. Using serologic tests to determine antibody prevalence, skin test data, and stool examination for parasites, we have been able to construct a profile of infectious diseases which are endemic, and others which have been introduced into the Waorani population. These findings are compared with similar data reported from elsewhere in the Amazon. Serologic studies demonstrating the presence of antibody to measles and poliovirus type 3 after vaccination indicate that the Waorani respond normally to viral challenge with these agents. The question of genetic inability among aboriginal Amerindians to respond to viral agents is discussed. Finally, general recommendations are made regarding the future health care of the Waorani.

Prevalence of antibody to the Norwalk virus in various countries.

Serum samples from children and adults from several countries were tested by radioimmunoassay for antibody to the Norwalk virus. Antibody was commonly found in adults from all the countries tested. Antibody appears to be acquired more rapidly in children from underdeveloped countries than in children from the United States.

Diarrhea associated with rotavirus in rural Guatemala: a longitudinal study of 24 infants and young children.

A population of 24 infants and young children followed prospectively during the first 3 years of life was studied for the occurrence of rotavirus infection by using enzyme-linked immunosorbent assay to detect virus in stools. Infection with rotavirus was associated with 26 (14.2%) of 183 selected diarrheal episodes. Twenty of the 24 infants and young children had diarrhea associated with rotavirus on at least one occasion and six had two such episodes. Rotavirus infection was documented in over 50% of the dehydrating episodes studied, thus further indicating the importance of rotavirus in this population.

Epidemiology of human rotavirus Types 1 and 2 as studied by enzyme-linked immunosorbent assay.

To determine the relative importance of two known serotypes of human rotavirus, we developed an enzyme-linked immunosorbent assay to differentiate serotype-specific rotavirus antigen and antibody. Using this technic, we studied the epidemiology of the two serotypes in acute gastroenteritis. Seventy-seven per cent of 414 rotavirus isolates were Type 2, and the remainder were Type 1. The serotype distribution was similar in specimens from children in Washington, D.C., and other parts of the world. Sero-epidemiologic studies revealed that most children living in the Washington, D.C., area acquired antibody to both types by the age of two years. An analysis of children who were reinfected indicated that sequential infections usually involved different serotypes and that illness caused by one serotype did not provide resistance to illness caused by the other serotype. These results suggest that, to be completely effective, a vaccine must provide resistance to both serotypes.