Rubella precipitin response in natural infection and in vaccination.

Abstract

The present investigation was directed towards determination of the significance of thetheta andiota precipitins in humoral immunity to rubella. Acutely infected cell cultures with rubella virus strains were found to be inadequate for production oftheta andiota antigens, requiring at least 800 × concentration of infected tissue culture fluids to obtain weakly reactingtheta andiota antigens in gel diffusion. To improve the antigen yield the rubella virus strains were adapted to a porcine stable cell line as a “chronically” infected culture. Three vaccine and three wild rubella virus strains, once established as chronically infected cultures, yielded equally well both thetheta and theiota antigens. Examination of sera from cases of natural infection by gel diffusion revealed that thetheta precipitin was present in all the sera with HAI titres of 1∶64 and higher. This precipitin was first detectable about seven days after the appearance of the HAI antibody. The concentration oftheta precipitin increased in parallel with the increase of the HAI titre. Theiota precipitin was not detectable in any sera with HAI titres of less than 1∶256 and only in 32 per cent of sera with titres of 1∶256 or higher. Noiota precipitins were found in sera collected earlier than five weeks after the exposure. Examination of post-vaccination sera from adults and children revealed that all sera with HAI titres of 1∶64 or higher had detectable levels oftheta precipitin but none hadiota precipitin, even those that had HAI titres of 1∶256 or higher. Even 80 × concentration of these sera by immunoglobulin precipitation failed to reveal detectable levels ofiota precipitin. The suggestion by others that theiota precipitin plays a major role in humoral immunity is questioned. A test foriota precipitin may serve a useful purpose as a yardstick in evaluation of the efficacy of live rubella vaccine.