G12 rotavirus has not been detected anywhere in the world since the first detection of a human strain, L26 (G12, P1B[4]), in the Philippines in 1990. In this study, we isolated a human rotavirus (strain T152) with a VP7 of G12 specificity from the stool of an 11-month-old diarrheic patient in Thailand. The strain T152 exhibited a long RNA pattern and subgroup I specificity. In the comparison of the nucleotide and amino acid sequences of the VP7 gene of strain T152 with those of rotaviruses with different G type specificities, strain T152 showed the highest identity, 90.9 and 93.9%, respectively, to G12 prototype strain L26. In contrast, the VP4 gene of strain T152 showed the highest identity with P[9] specificity of human strains K8 and AU-1 and feline strains Cat2 and FRV-1, with homologies of 89.3 to 90.6% at the nucleotide level and 93.9 to 95.6% at the amino acid level. Thus, strain T152 was found to be a natural reassortant strain with G12 and P[9] specificities.Rotavirus is the major cause of acute gastroenteritis in infants of animals and humans. In developing countries, rotavirus infection results in high mortality, and an annual death rate of 800,000 persons has been estimated (6). Furthermore, in developed countries, rotavirus infection is a cause of high morbidity. However, to date no vaccine has been successful. Rotavirus VP7 and VP4 have independent serotype specificities of the G serotype and P serotype, respectively. A total of 14 G serotypes have been reported. Among them, 10 G serotypes have been detected in humans. G1 to G4 are the major G serotypes, and G5, G6, G8 to G10, and G12 are minor or unusual ones (2, 6). In contrast, 21 P genotypes have been recognized, and at least 10 P genotypes have been detected in humans. Recently, a number of strains with an unusual G or P type and a rare combination of G and P types have been detected in human rotaviruses worldwide (1, 3, 10-12, 16, 17, 25-27).G12 was first detected in stool specimens collected from diarrheic children under 2 years of age between December 1987 and February 1988 in the Philippines (20, 27). In 40 rotavirus-positive stool specimens, 20 samples showed subgroup I and long RNA profile (7). Four samples were adapted to cell culture, and at least two (L26 and L27) of them were found to have G12 and P1B[4] specificities by serological and sequence analyses of their VP4 and VP7 (20,27). Since then, however, no further report on the detection of G12 in humans or animals has been presented, although extensive surveys on the G serotype distribution worldwide have been conducted. In this study, we isolated a human rotavirus with G12 and P[9] specificities in Thailand. MATERIALS AND METHODSStool specimens. A total of 405 stool specimens were collected from diarrheic children in a hospital of the Queen Sirikit National Institute of Child Health, Thailand, between 1998 and 1999. An approximately 10% (wt/vol) stool suspension was prepared in phosphate-buffered saline. For virus isolation in MA-104 cells in roller tube culture, each stool extr...

The subgroup and serotype specificities of human, bovine, and porcine group A rotaviruses in stool specimens collected in Thailand were examined by an enzyme-linked immunosorbent assay by using subgroupand serotype-specific monoclonal antibodies. A clear yearly change was observed in the serotype distribution of human rotavirus. Between 1983 and 1984, serotype 4 was the most prevalent, while the highest frequency of serotype 2 was found between 1987 and 1988. All the bovine and porcine rotaviruses examined showed subgroup I specificities and long RNA patterns. It was of note that serotype 3 porcine rotaviruses were found at a high frequency.

A total of 557 fecal specimens collected from piglets with diarrhea in Thailand were examined for rotavirus RNA by polyacrylamide gel electrophoresis. Twenty-three, one, and two samples were positive for group A, group B, and group C rotaviruses, respectively. Two samples exhibited two segments found in picobirnavirus RNA. RNA electropherotyping of 23 group A rotaviruses showed that they were classified into five patterns. By serotyping by enzyme-linked immunosorbent assay and PCR, viruses in 3 and 14 specimens were found to be serotype G3 and serotype G10, respectively. For one specimen, containing a serotype G10 virus (strain P343), virus was isolated in MA-104 cells, and the nucleotide sequences of the VP7 and VP4 genes were determined. Comparative sequence analysis and cross-neutralization tests showed that strain P343 has B223-like G10 and UK-like P7 serotype (or VP4 genotype 5) specificities. Rotaviruses having such antigenic specificities have not been detected in piglets. Thus, the interspecies transmission of rotaviruses between cows and pigs was suggested.

SUMMARYA total of 241 group A rotavirus-positive stool samples collected from diarrhoeic patients in Thailand between July 1988 and June 1991 were characterized for their serotypes by enzyme-linked immunosorbent assay (ELISA) using serotype-specific monoclonal antibodies and by a polymerase chain reaction (PCR). In July 1988-June 1989, serotype 1 was the most prevalent (63-4%), followed by serotype 4 (1IO0%) and serotype 2 (8-5 %). In July 1989-June 1990, 59-8 % were serotype 1, 24-3 % were serotype 2, and 6 1 % were serotype 3. In contrast, in July 1990-June 1991, serotype 3 was detected in the highest frequency (40-5 %), 29-9 % were serotype 1, and 27-3 % were serotype 2. Thus, a distinct yearly change of serotype distribution of rotavirus in Thailand was observed in the three consecutive years. In particular, it was of note that the prevalence of serotype 3 greatly increased, in contrast to the previous studies in which almost no serotype 3 rotaviruses were detected in the years 1983-8 in Thailand.Rotavirus is a major cause of diarrhoea in infants and young children worldwide [1,2]. The mortality rate in rotavirus diarrhoea is high in areas where therapy for dehydration is not sufficiently available. Because of the importance of this disease as a major global health problem, the World Health Organization considers the development of an effective rotavirus vaccine to have a high public health priority. However, the antigenic complexity of rotavirus has hampered the development of an effective vaccine [1,3]. Epidemiological studies on distribution of human rotavirus serotypes provide the basis for interpreting the results of field trials of candidate vaccines.