Two cases of aseptic meningitis epidemic were observed at Toyama City and Fuchu Town from July to September, 1964. Many Japanese reports described this disease at that time indicated that similar epidemics of aseptic meningitis have been found in many districts of Japan in 1964 and 1965. We examined above our cases by the epidemiological and virological procedures. Results obtained are summarized as follows: 1) The peak of outbreaks in Toyama City case, total 29 patients, lasted for 2 months was not clear, but it was found on the fifth week of July or on the first week of August in Fuchu Town case, total 41 patients, similarly retained for 2 months. 2) The age distribution of patients, in which 67.1 per cent was shown to be accumulated in 5 to 9 years old, ranged from 12 months to 13 years old. 3) In 25 cases out of 51 patients tested in both epidemics the ECHO-4 virus was recovered, including 3 cases, from those spinal fluids viruses were isolated. 4) The neutralizing antibody responses in paired sera of 26 patients tested against ECHO-4 virus were proved to be significant using DuToit strain of virus and continuous GMK cell line, though the acute phase sera of 3 cases had already shown positive antibody titers in 1:16. 5) Serological investigations on possible occurrence of ECHO-4 virus infection at Toyama area were performed by the similar procedures to those as in 4). Human sera collected voluntarily at Horioka Town for such purpose were grouped as each 70 samples obtained before and after aseptic meningitis outbreaks in 1964. The antibody possessing ratio in the sera of children under 9 years old was only 3 per cent in the grouped sera collected in 1963 before epidemics of aseptic meningitis. Contrary to this low ratio, higher positive ratio of more than 50 per cent, was observed in the sera of the same ages group taken in 1964 after outbreaks of this disease. 6) From these serological results considering antibody almost negative age group under 9 years old it may be assumed that the aseptic meningitis epidemics caused by ECHO-4 virus had not occurred in infants or children at Toyama area during past 9 years up to 1963.
Polioviruses of various types isolated in Hokkaido from paralytic poliomyelitis patients, familial contacts and healthy children at epidemic and non-epidemic periods during the 5 years from 1956 to 1960 were tested for the reproductive capacity at 40°C; (rct/40). The relationship between the rct/40 character of the viruses and their sources of isolation was investigated from epidemiological viewpoint. 1) All the type 1 polioviruses isolated at non-epidemic and pre-epidemic periods were the characters of either rct/40± or rct/40- regardless of the source of virus isolates. With the progress of the 196 epidemic, however, the virus of rct/40- disappeared while that of rct/40+ increased rapidly in the number. 2) All the type 1 viruses obtained from feces and the CNS of fatal cases at the acme of the epidemic were highly positive in the character. However, the rct/40 characters of viruses from both the paralytic cases and familial contacts were not always the same. 3) The type 2 polioviruses isolated from paralytic cases at the sporadic were mostly rct/40+ while those of the same type from healthy children were invariably rct/40±. In contrast, most of the type 3 polioviruses isolated from paralytic cases at the sporadic showed greater EOG than that of the type 3 Sabin strain at the temperatures over 40°C.
Factors influencing the rct character of poliovirus were studied in-vitro to elucidate the mechanisms of change in the character of type 1 wild polioviruses isolated at the 1960 epidemic. The results were following: 1) It was demonstrated that the wild poliovirus strains were usually consisted of viral particles different in the rct character. Additional evidence were obtained suggesting that the proportion in the number of rct/40+ and rct/40- particles included in each strains might determine the character of the strain as a whole. 2) The wild strains of rct/40- did not change the character after 5 passages in MK cell cultures at 37°C. In contrast, most of the virus strains did change the character after serial passages in cell cultures at 40°C. These results are suggesting that the change in the character of wild polioviruses obtained at the epidemic may be due to the selection of rct/40+ particles by sequential passages of the viruses in the body of febrile patients. 3) The stability of the rct character of attenuated polioviruses (Sabin strains) after human passage differed by the virus type. The type 2 virus was much more stable than type 1, while the type 3 virus was markedly unstable.
Penetration of measles virus (Toyoshima strain) in African Green monkey kidney-derived Vero cells was studied in detail. Treatment of cell-virus complex with pH 3.0, 5 minutes' pulse was found effective to exterminate viral infectivity without leaving any disturbance on viabilities of cell and infective center. Hyperimmune antiserum of guinea pig against measles virus was not potent enough in eliminating free and cell-attached viruses from reaction mixture in a short time. Therefore, ‘penetrated virus’ is defined in this paper as a survived infective center after the low pH treatment. Penetration, thus determined, followed the first order kinetics, and its initial velocity was enhanced by centrifugal force applied to the cell-virus complex. This process was found being dependent on reaction temperature, nutritional condition of the cell, inhibited by added monoiodoacetate and sodium fluoride, not by potassium cyanide or sodium malonate. Anticellular guinea pig serum, when treated prior to viral adsorption, suppressed the penetration markedly. These findings strongly suggested the identity of the most part of this process to the well-established phagocytotic activity of cells. Trials to locate the site where specificity of viral infection being regulated are now underway.