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Four synthetic peptides which correspond to continuous antibody epitopes of herpes simplex virus (HSV) type 1 glycoprotein D (gD) within amino acid residues 1-23 (8-23), 268-287 and 340-356 were evaluated for in vitro stimulating activity on HSV-primed murine T lymphocytes. All peptides stimulated lymphoproliferative responses and interleukin 2 (IL2) production from draining lymph node (LN) cell populations taken 5 days after footpad immunization with live HSV. Similar responses were elicited from splenic memory T cells only if these T cells were restimulated with HSV in vitro and rested prior to peptide stimulation. Furthermore, peptide stimulated memory T cell populations released soluble factor(s) into the culture supernates which modulated the induced lymphoproliferative and cytotoxic T lymphocyte (CTL) activities of HSV-stimulated, HSV-immune splenocytes (indicator cultures). Memory T cell supernates suppressed lymphoproliferation of indicator cultures, while CTL activity of indicator cultures was either enhanced or suppressed, depending on the peptide and concentration. In contrast, supernates generated by peptide stimulation of draining LN cells had no effect on CTL activity of indicator cultures. However, the lymphoproliferative responses were augmented with three of the four peptides at the highest concentration of peptides tested. Our experiments indicate T helper (Th) and T suppressor (Ts) lymphocyte recognition of four synthetic peptides which encompass continuous antibody epitopes of HSV gD. Immunization with one of these peptides (1-23) induces virus neutralizing antibodies and protection against lethal viral challenge. Th lymphocyte recognition of this peptide in particular, together with its observed function in the induction of protection against HSV infection, indicates that this peptide is a promising candidate as a synthetic vaccine against HSV infection.

Human peripheral blood monocytes were placed on a discontinuous density gradient of bovine serum albumin and fractionated into five subpopulations. Cells from each subpopulation were assayed for spontaneous cytotoxic activity against K562 tumor cells. Immediately following fractionation, monocytes were not cytotoxic. Following incubation for at least 48 hr, monocytes from two layers of the gradients clearly exhibited greater spontaneous cytotoxic activity than all others. The degree of cytotoxicity expressed by cells of these layers was enhanced by the addition of indomethacin and inhibited by prostaglandin E2 (PGE2). Monocytes acquiring spontaneous cytotoxicity did not secrete measurable levels of PGE2 and had increased levels of purine nucleoside phosphorylase after 72 hs of culture in vitro. Surface markers HNK-1 and Mac-1 normally associated with cytotoxic function, were detected on these cells by indirect immunofluorescence at isolation and after culture. The fraction with the greatest cytotoxic activity showed an increase in the proportion of cells displaying reactivity to HNK-1 after culture compared to initial isolation.