No abstract

We developed a dot-blot hybridization assay to detect rotaviral RNA sequences in tissue culture or in clinical samples. 32P-labeled cloned cDNA probes of the simian rotavirus SA11 specifically detected rotaviral RNA sequences and were more sensitive for detecting SA11 than was the commercial enzyme-linked immunosorbent assay Rotazyme test. A full-length probe of SA11 gene 6 detected 2.5 X 10(5) SA11 particles or approximately 0.27 ng of purified SA11 dsRNA. Combined probes from genes 6 and 9 detected 0.135 ng of purified SA11 dsRNA. The assay detected group A rotaviruses from different subgroups and serotypes, but the sensitivity of RNA detection varied from 0.5 to 31 ng when RNA from heterologous strains of virus was analyzed. An analysis of coded stool samples correctly identified 31 (91%) of 34 samples positive for rotavirus by electron microscopy and 100% of 26 samples negative for rotavirus by electron microscopy. Preliminary experiments also showed the assay has potential to directly characterize (subgroup and serotype) rotaviral isolates.

Antigenically distinct rotaviruses, i.e., viruses morphologically identical to conventional rotaviruses by electron microscopy, yet lacking the common group antigen(s) detected by an enzyme-linked immunosorbent assay, were found in 2 of 51 fecal samples from Bulgarian infants with rotavirus gastroenteritis. These antigenically distinct viruses contained 11 segments of double-stranded RNA, but they demonstrated a unique RNA migration profile after electrophoresis of the genome RNA in polyacrylamide gels. This report confirms the presence of a new group of rotaviruses in humans. The significance of these viruses is currently unknown, and specific diagnostic tests must be developed for epidemiological studies to determine their role as human and veterinary pathogens and to evaluate their impact on proposed vaccine development programs.

Baculovirus recombinant-expressed antigens of Norwalk viruses (rNV) and a Mexico strain (rMX) of the Snow Mountain serogroup of human caliciviruses (HuCVs) were used in enzyme immunoassays to study the antibody prevalence among the Kuwaiti population and foreign workers employed in Kuwait. The antibody titers in 16 different age groups which ranged from neonates to centenarians were investigated by testing eight different dilutions of each serum (1:200-1:25,600). The results indicate that NV infection is widespread in Kuwait and affects all age groups Ninety-eight percent of the 433 serum samples tested had antibodies to rNV. In the 50-79-year, old age group, the antibody levels to rNV were higher and significantly different from those in children 0-7 years old. In infants, the rNV antibodies did not diminish by 4 months of age and their titer steadily increased with age. When 414 of these sera samples were tested for antibodies to rMX, 96% positive serological responses were observed. Antibody titers to rMX were reduced in infants from 4 to 11 months; however, 95% of the samples were positive. These data indicate that children born in Kuwait are infected with Norwalk-like viruses at a very early age. Finally, antibodies to rNV and rMX were found in 98% of 151 and in 95% of 148 foreign workers, respectively.