The neutralization of pox viruses II. Relationships betweenvaccinia, rabbitpox, cowpox and ectromelia

Plaque neutralization on HEp 2 cells was used to determine the relationship between vaccinia, rabbitpox, cowpox and ectromelia using both 7 S and 19 S antibody. It was shown that for the strains of virus used vaccinia and rabbitpox were very similar but cowpox and particularly ectromelia were clearly distinguishable. The cross-titration relationships were the same for 7 S and 19 S antibody. The titration slopes and kinetics of cross-neutralizations were interpreted on the basis of a hypothesis of antibody competition put forward in the preceding paper. It was tentatively concluded that these four viruses share a common critical antigen for neutralization and that differences in the structure or presentation of neighbouring antigens could give rise to some of the observed effects.