Journal of the Japanese Association for Infectious Diseases

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At present, the procedure of neutralization test of Japanese encephalitis is mostly done by virus-dilution technique, not by serum-dilution technique. On the other hand, hemagglutination inhibition (HI) test is done by serum-dilution technique.
We attempted to do neutralization test by serum-dilution technique using plaque reducto method in bottle cultured chick fibroblasts and planned to find out some relationship between neutralizing index and HI antibody titer.
One hundred and thirteen human sera with various titers. of HI antibody, were tested against Japanese encephalitis virus (Nakayama strain).
The results obtained are summarized as follows;
(1) In case of Japanese encephalitis, serum dilution titer which exhibits 50% plaque reduction is able to be expressed as the neutralizing index.
(2) The neutralizing indexes of human sera were significantly correlated with HI antibody titers.
(3) Neutralizing antibodies were detected in about half the number of human sera without HI antibody, therefore this plaque reduction method is an extremely sensitive method to detect serum antibody.

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Leptospira icterohemorrhagiae weil was demonstrated in blood, urine and organs of experimentally infected guinea pig by means of Fluorescentantibody.
L. icterohemorrhagiae in blood, urine and organs was clearly fluorescent, even if the organisms were few in number. In addition, it was found that irregular type of the organisms were detected in liver and kidney.
A technic for the use of fluorescein labeled antiglobulin as an indicator of Leptospiral antibody is described.

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