A herpes simplex virus type 2 (HSV-2 ) type-specific monoclonal antibody (MAb), CH-A9, precipitated a gly-coprotein with an M;of approixmately 30 000 (g30K) from extracts of HSV-2-infectal BHK cells labelled with [;H]leucine, [;C] fructose or [;H] glucosamne. The M;of this glycoprotein is lower than those of other HSV glyco-proteins. Immunoassays of BHK cells infectal with HSV-1-HSV-2 intertypic recombinants localized the gene enco-ding the target antigen of MAb CH-A9 to the unique long (U;) region at map units 0.490 to 0.564. Tunicamycin