SummaryThree cytopathic rotavirus strains were isolated in MA104 cells from faecal specimens of pediatric patients with acute gastroenteritis. Pre-treatment of virus with trypsin and incorporation of a small amount of trypsin in maintenance medium were important for establishment of the strains in these cells. The isolates were antigenically closely related with strain Wa of human rotavirus and had some antigenic relationship with strain Lincoln of bovine rotavirus. , Numerous attempts to propagate human rotaviruses to high titer in cultured cells have failed (1--3, 7, 8, 1t). Recently, WYATT et al. (12) adapted type 2 human rotavirus (strain Wa) to grow to relatively high titer in primary cultures of African green monkey kidney cells after 11 passages in newborn gnotobiotic piglets. In the present study we isolated 3 strains of human rotavirus in cultures of MA 104 cells, a stable cell line derived from embryonic rhesus monkey kidney.Faecal specimens were obtained from pediatric patients who had whitish, watery diarrhea, vomiting and slight fever and recovered in 3 to 5 days. The faecal specimens were collected the day after the onset of the disease and stored at --80°C until use. All the specimens were shown by electron microscopy to contain rotavirus particles when examined by the method described previously (9).Cultures of MA104 cells were prepared in 110 × 10 m m tubes. The growth medium used was Eagle's minimum essential medium (MEM) containing 10 per cent tryptose phosphate broth (TPB) (Difco), 10 per cent calf serum, 100 units/ml penicillin, 100 ~g/ml streptomycin and t ~g/mI fungizone, and the maintenance medium (MM) was MEM containing 10 per cent TPB, 0.5 per cent sodium glut,-0304-8608/81/0069/0155/$ 01.20

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Four human group C rotaviruses were detected in Tokyo in 1987 and 1988 during a survey over 7 years. Among the four rotaviruses, two electrophoretic patterns were indicated by polyacrylamide gel electrophoretic (PAGE) analyses. Clinical symptoms, signs, family history, and patients' ages varied. Group C rotaviruses were found also in other parts of Japan in 1988. It was suspected that group C rotaviruses would continue to spread throughout Japan within the near future.

82/2,223 stool specimens, collected 1982-1988, from children with enteritis (3.7%) were found to contain adenoviruses; 17 adenovirus-positive samples were provided from other institutes. 89 adenoviruses were isolated in Graham 293 cells from these 99 specimens and were typed by DNA restriction enzyme analysis with Sma I. 37 strains were typed as adenovirus 40 (AD40), and 37 strains as adenovirus 41 (Ad41). Although most strains had the same DNA profiles, a few strains had 3 kinds of different electropherotypes generated by Sma I. Five strains were identified as adenovirus 31. The remaining 10 strains were adenovirus 1 (2 strains), adenovirus 2 (3 strains), adenovirus 3 (1 strain), adenovirus 5 (1 strain), and a non-classified adenovirus (3 strains). Ad40 and Ad41 infections were found throughout the year, but peaked between September and November. 80% of the children with adenovirus infections were less than or equal to 2 years of age. The highest incidence of diarrhea caused by Ad40 or Ad41 was in 6-11 months old children. 1982-1984, the rate of Ad40 infection was 91.7%, while the rate of Ad41 infection was only 8.3%. The prevalence of Ad40 infection gradually diminished from 1985. During 1987 and 1988 the reverse ratios, 20.6% and 79.4%, respectively, of Ad40 and Ad41 infections were observed. Thereafter, Ad41 infection became predominant.

A total of 322 single and paired serum samples from children (newborn to 10 years old), young adults (18 to 20 years old), pregnant women and their cord serum samples, and elderly people (more than 70 years old) was tested for antibodies to enteric adenovirus types 40 and 41 by neutralization test. Serum samples were also tested for antibody to the common antigen of adenovirus by enzyme immunoassay. The incidence of antibodies rose gradually through childhood. Antibodies were found in 20% of children between 1 and 6 months old and in 50% of those 37 to 48 months old. Of serum samples from young adults, 48% had antibodies. Antibodies were found in 10% of serum samples from the aged. Of patients with acute gastroenteritis, 19% showed a significant rise in antibody to adenovirus type 40 or 41 or both, and 42% of the same serum samples had a significant rise in antibody to rotavirus by enzyme immunoassay. None of the serum samples tested was negative to adenovirus common antigen. Noncultivatable adenoviruses have been demonstrated by electron microscopy in stool samples from children with diarrhea (5, 11, 13). On the basis of antigenic and DNA restriction pattern techniques, adenovirus types 40 and 41 (Ad40 and Ad4l, respectively) have been identified in stool specimens from patients with infantile gastroenteritis (4, 17, 20). Enteric adenoviruses are recognized as the second most commonly identified agent after rotavirus in stool samples of infants and young children with viral gastroenteritis (2, 10, 17). The seroepidemiology of enteric adenoviruses has been reported only by Kidd and his colleagues (9, 10). We report here the seroprevalence of neutralizing antibody to enteric adenoviruses in serum samples from various age groups in Japan.

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