Production and some properties of neutralizing antigens of herpes simplex virus

Human diploid cells (LEP) infected with herpes simplex virus (HSV) type 1 were extracted by treatment with Nonidet P-40. The content of antigens reactive with neutralizing antibody in the clarified extract was measured by the blocking test. Influence of various factors on the production of the blocking antigens (BA) was tested. Highest BA titres in LEP cells were achieved at a multiplicity of infection (m.o.i.) of 0.5 TCD50/cell, medium 199 and 22 to 29 hours incubation at 37 degrees C. The use of resting cultures or the presence of cytosine arabinoside in medium reduced the BA production. The activity of BA was reduced by repeated freezing and thawing. The antigen was stable at -20 and -70 degrees C. One hour heating at 60 degrees C resulted in a marked decrease of the antigen titre. BA was resistant to formalin; formalin treatment did not influence its thermosensitivity.