Prevalence of Antibodies in Human Sera against JC Virus, an Isolate from a Case of Progressive Multifocal Leukoencephalopathy

Sera from 406 people of various ages throughout the state of Wisconsin were assayed for antibodies against IC virus, a new human papova-like virus isolated from a patient with progressive multifocal leukoencephalopathy. The hemagglutination-inhibition (HAl) test was used after it was determined that a linear relationship existed between the titers of HAI and neutralizing antibodies in human sera. About 69% (191/277) of the adults tested had significant levels of antibodies against IC virus in their serum. The highest rate of conversion to seropositivity occurred during the first 14 years of life. No sex difference in the incidence of antibodies against IC virus was found.