Epidemiological features of rotavirus infection in Caracas, Venezuela: implications for rotavirus immunization programs.

The epidemiological features of rotavirus infection may be quite relevant for evaluation of the performance of a rotavirus vaccine in different settings, as well as for monitoring its impact during vaccination under routine conditions. This article describes some important issues regarding rotavirus epidemiology in Venezuela, where major field trials of rotavirus vaccine have been carried out. Rotaviruses was significantly more frequently observed in inpatient (43%) than in outpatient (21%) consultations for diarrhea in infants and young children. There was a high prevalence of rotavirus illness, regardless of socioeconomic conditions, but the risk of dehydration was greater among the lower socioeconomic groups. Rotavirus disease occurs year-round, with a slight seasonal pattern. Eighty-five percent of rotavirus-positive diarrheal episodes, as well as 86% of cases of dehydration due to rotavirus, occurred during the first year of life. However, rotavirus illnesses occur less commonly during the first months of life (0-2 months), which may be a result of protection by transplacental antibodies. The pattern of acquisition of rotavirus antibody was consistent with this age distribution of disease and with optimal age for vaccination. Thus, regional epidemiological characteristics of rotavirus infection may affect optimal performance of rotavirus vaccine.

Immune response to three doses of quadrivalent rotavirus vaccine: 1-year follow-up.

Twenty-eight children who received three doses of the quadrivalent rotavirus vaccine with 4 x 10(5) plaque-forming units (p.f.u.) were followed during a year after vaccination. Serum samples were obtained and evaluated for rotavirus IgA and neutralizing antibodies against vaccine and human rotavirus strains. At the end of the study, up to 61% of the children showed an increase in circulating IgA antibody levels. Nearly all of the vaccinated children increased their neutralizing antibody titres against the vaccine strains, and 25-54% against human rotavirus serotypes. After comparing the vaccinees with a population of children naturally infected with serotype G1 in the same study area, we conclude that three doses of 4 x 10(5) p.f.u. of the quadrivalent vaccine should prepare the child against future severe rotavirus diarrhea.

Homotypic immune response to primary infection with rotavirus serotype G1.

Some aspects of rotavirus humoral immunity were assessed on the basis of distinguishing serotype-specific specificities (VP4/VP7) by using rotavirus reassortants, human and animal strains in neutralization assays in serum samples obtained during the acute phase, and 1, 6 and 12 months after primary natural infection. In this study, all the infecting virus strains were characterized as G type and some also as P type. Primary natural infection induces a significantly greater homotypic neutralization response than heterotypic response. In addition, there was no significant difference in the number of homotypic or heterotypic responses following reinfection. Transplacentally acquired homotypic antibodies were associated with protection against dehydration during rotavirus gastroenteritis.

Enumeration of selected leukocytes in the small intestine of BALB/c mice infected with Cryptosporidium parvum.

Neonatal, suckling BALB/c mice inoculated with Cryptosporidium parvum produce an infection characterized by continuous shedding of oocysts that spontaneously clears by the time the animals are three weeks of age. Neonatal mice were used to characterize the leukocyte subgroups present in Peyer's patches from the ileum and jejunum of Cryptosporidium-infected and healthy mice. After infection, ileal Peyer's patches showed a predominant CD8+ response, with abundant monocytes-macrophages (MOMA-2+) and nonlymphoid dendritic cells (NLDC-145+ cells). In contrast, jejunal Peyer's patches showed more T lymphocytes than ileal patches, with a predominance of CD4+ cells and many dendritic NLDC-145+ cells and MOMA-2+ cells. The present results showed that ileal and jejunal Peyer's patches are functionally different in response to Cryptosporidium parasites. These findings suggest a preferential involvement of jejunal Peyer's patches in T cell-dependent immunity against the parasite, whereas ileal patches may be associated with B cell expansion and maturation.

Temporal distribution of human rotavirus serotypes 1,2,3, and 4 in Venezuelan children with gastroenteritis during 1979-1989.

The temporal distribution and clinical severity of rotavirus VP7 serotypes 1, 2, 3, and 4 recovered from 427 Venezuelan children with acute gastroenteritis over a period of 11 years were studied. Rotavirus VP7 serotype was established by ELISA serotyping in 298 (69.78%) of the specimens while the serotype of the remaining 129 (30.21%) samples could not be determined. Of the specimens typed, 85 (19.90% of the total) were serotype 1, 43 (10.07%) were serotype 2, 105 (24.59%) were serotype 3, and 65 (15.22%) were serotype 4. Yearly changes in the frequency of individual serotypes were observed. The predominance of a single serotype with minor contribution from others was noted every year. In this study, serotype 1 appears to induce a less severe illness in comparison with serotypes 2, 3, and 4. No apparent association between the proportion of each serotype and the children's age were found.

Cryptosporidiosis in Venezuelan children with acute diarrhea.

Thirteen of 120 Venezuelan children with acute diarrhea were found to be excreting Cryptosporidium oocysts in their stools. This confirms that Cryptosporidium can infect immunocompetent children, and the relatively high frequency found suggests that this protozoan may be an important cause of diarrhea in Venezuela.