Distribution of indigenous lactobacilli in the gastrointestinal tracts of rats was investigated at the species level. The indigenous lactobacilli isolated from conventional rats were divided into three groups, Lactobacillus acidophilus and its related strains, L. fermentum, and L. murini. Localization of the Lactobacillus groups in the gastrointestinal tracts could be distinguished clearly based on arabinose and glucose fermentation reaction of isolates from each part of the gastrointestinal tract. Group I (L. acidophilus and the related strains) and Group II (L. fermentum) were the major populations of lactobacilli on the walls of the non-glandular part and in the contents of the stomachs of both conventional and gnotobiotic rats. Group I predominated in all the parts of the digestive tract of conventional rats, whereas Group II was in the minority in the lower part of the gastrointestinal tracts of both groups of rats. Group III (L. murini) was the predominant population of Lactobacillus in the lower part of small intestine of conventional rats and in all parts of the gastrointestinal tracts of gnotobiotic rats except for the wall of the non-glandular part of the stomach.

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Isolation of a cytopathic agent causing formation of syncytial giant cells in co-cultivated Vero cells from the brain of an autopsied case of subacute sclerosing panencephalitis (SSPE) is reported. The syncytia usually autolyzed from the center after growing to 1 to 2 mm in diameter and then detached from the culture vessels, and finally made macroscopically recognizable round plaques on the monolayer under liquid overlay. The agent was identified serologically as an agent related to measles virus, by both immunofluorescent tests and plaque reduction tests using anti-measles sera. However, the infected cells did not produce either virions or hemagglutinin, and failed to show hemadsorption and hemolysis of African green monkey red cells even after the 55th passage through Vero cells. Newborn mice, adult mice and hamsters showed neurologic signs after intracerebral inoculations of the infected cells, and most of them died from acute encephalitis. Guinea pigs were unsusceptible. From the brain of the animals with neurologic signs, a similar agent to the inoculated one was recovered.
The new isolate appears to be a strain closely related to measles virus on the basis of serology, and was designated as SSPE- “Kitaken-l” strain.

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The virus strains isolated from clinical cases in an epidemic of hand-foot-and-mouth disease in Matsue in 1973 were characterized and its properties were compared with those of the Coxsackievirus group A type 16 (CA 16) prototype strain. The virus isolated in 1973 was similar to CA16 prototype virus with respect to morphology in electron microscopy, resistance to ether and capability to replicate in medium containing fluorodeoxyuridine. Cross neutralization tests using guinea-pig and horse antisera revealed that there was little or no detectable common antigen between the two viruses. The two viruses also differed in heat stability of virion infectivity : the 1973-viruses were much more resistant to heat than the prototype virus. Under one-step growth conditions in Vero cell cultures, growth rate and virus yield of the 1973-viruses were lower than those of CA 16, but this property was independent of incubation temperatures, pH of culture medium and other culture conditions. Several other differences in property between the 2 strains are also described. It is concluded that the epidemic in 1973 was caused by a virus whose properties differed greatly from those of the CA16 prototype.

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Attempts were made to improve the rate of isolation of herpes simplex virus (HSV) from clinical specimens by minimizing loss of virus infectivity during transportation and employing the most sensitive cells for isolation. Basical analyses using standard strains of type 1 and type 2 HSV indicated that virus titer decrease was marked even at low temperatures in environments free of proteinous stabilizer such as normal serum or tissue extract, negating the generally held concept that HSV is stable in distilled water. YLE (Earle-lactalbumin hydrolysate-yeast extract) medium containing 20% inactivated calf serum was determined to be a transport medium of choice, because degradation of suspended virus during storage and freeze-thawing was negligible and loss of virus during Millipore filtration was minimal. Special coating of the membrane could also be obviated by the use of this solution. In a cell susceptibility test using clinical specimens, secondary rabbit kidney (SRK) cells were the most sensitive, showing a quick development of cytopathic effect. Vero and RK-13 cells were the second best, whereas monkey kidney, HeLa and L cells were far less sensitive. A total of 136 specimens from suspected cases, sent by dermatologists, were tested using SRK cells, and 99 strains of type 1 and 15 strains of type 2 HSV were isolated. Excluding one case from which vaccinia virus was isolated, the isolation rate of HSV was 84.4%.

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Early and late IgG of rabbits immunized with herpes virus showed, respectively, 8-fold and 2-fold enhancement of neutralization endpoint in the presence of complement (C). Kinetic curve experiments employing an appropriate amount of virus revealed that both neutralization and sensitization followed first-order reaction, and each IgG possessed a certain range of concentration where neutralization was negligible while sensitization was marked. Dose responses of neutralization and sensitization velocities demonstrated that the C enhancement of late IgG was about 7-fold and that of early IgG more than 20-fold. These facts suggested that the IgGs contained two different entities of complement-requiring (CRN) and non-requiring neutralizing (N) antibodies at different proportions, only the former being responsible for sensitization. The different CRN : N ratios obtained by the endpoint and kinetic methods may mean either that the two anti-bodies differ in avidity for the virus or that the number of critical sites per virion for CRN antibody is greater than that for N antibody. In this interpretation, sensitization by CRN antibody as well as neutralization by N antibody is thought to result from attachment of a single antibody molecule to the viral critical site. Alternative explanations, ascribing the mechanism of neutralization to steric hindrance of critical sites or to multiple hit of those sites by antibody, were denied by analyses of the present data.

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