The serological relationship between vaccinia and ectromelia viruses

Abstract

1. Elementary body suspensions of vaccinia and ectromelia were obtained from rabbit skin and chick embryo or mouse liver and chick embryo respectively and used to immunize rabbits.2. Judged by the complement fixation and haemagglutination tests, the viruses from different hósts were very similar antigenically. Ectromelia and vaccinia appeared closely related, the heterologous virus titres being usually lower than the homologous.3. Elementary body suspension agglutination tests did not reveal a similar relationship between the two viruses, but were not satisfactory on account of the low antibody content of the antiectromelia sera.4. Highly active ectromelia antisera were not obtained and there was no evidence of multiplication of this virus in rabbits.5. Only slight neutralizing activity was demonstrated in the antisera.6. Elementary body suspensions of ectromelia virus prepared from mouse livers, as well as the crude liver extracts, were soon inactivated. Egg membrane preparations were relatively stable.