Heterogeneity in Herpes simiae (B virus) and some antigenic relationships in the herpes group.

(B virus) grown in rabbit brain was passaged 9 times through the brains of suckling hamsters and treated with antiserum against virus at each passage. Its properties were compared with a control line passaged in the absence of antiserum. When measured in terms of the ratio of infectivity for suckling hamsters to infectivity for rabbits (both inoculated intracerebrally), the control line of virus showed a greater increase in infectivity for suckling hamsters than did the antibody selected line. The latter, dose for dose, killed suckling hamsters more quickly. Whereas the parent and control lines produced several kinds of cytopathic effect in cell cultures, the antibody selected line induced predominantly the formation of syncytia. Cross neutralization tests with antisera against various herpes viruses revealed that the antibody selected line differed antigenically from the control line. In these tests, serum from a patient who died of herpes encephalitis resembled antiserum against B virus rather than antiserum against virus.