Transplacental Passage of Antibody to Western Equine and St. Louis Encephalitis Viruses

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  • Bureau of Acute Communicable Diseases and the Viral and Rickettsial Disease Laboratory, California State Department of Public Health, Berkeley 4, California
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Examinations for the presence of neutralizing antibody to the Western equine encephalitis (WEE) and St. Louis encephalitis (SLE) viruses were made of blood specimens from parturient mothers residing in an endemic area of Western equine and St. Louis encephalitis. It was found that 11 per cent of the mothers studied possessed neutralizing antibody to the WEE virus and 27 per cent possessed neutralizing antibody to the SLE virus; there also was evidence of a direct relationship between the length of residence in the area and the acquisition of such antibody.

It was found that both complement-fixing and neutralizing antibodies to these two viruses readily pass the placenta, but no evidence was obtained that the difference between the proportion of infants possessing antibody to the WEE virus and those possessing antibody to the SLE virus is responsible for the remarkable difference in the attack rates of these two agents for infants. The temporal persistence of passively acquired neutralizing antibody to the WEE and SLE viruses appeared to be no greater than that reported for antibodies to other viral agents.