The herpes simplex virus type 1 (HSV-1) a proteins ICP4, ICPO, and ICP27 are transacting proteins which affect HSV-1 gene expression. To investigate potential interactions between these a products and to determine the specificity of action of the a proteins in combination with each other compared with their activities individually, we performed a series of transient-expression assays. In these assays we used plasmids containing the a genes encoding ICP4, ICPO, and ICP27 either singly or in combination as effectors and HSV-1 genes of different kinetic classes and heterologous genes as targets. The HSV-1 targets consisted of promoter-regulatory domains from a (ICPO and ICP27), 0 (thymidine kinase and alkaline exonuclease), P-y (glycoprotein D, glycoprotein B, and VP5), and y (glycoprotein C) genes, each fused to the chloramphenicol acetyltransferase (CAT) gene. The heterologous target genes consisted of the simian virus 40 early promoter with enhancer and the Rous sarcoma virus long terminal repeat promoter and enhancer each fused to the CAT gene. Target

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Mononuclear phagocytes, including circulating monocytes and tissue macrophages, play a central role in resistance to viruses. This resistance can be expressed both non-specifically, and specifically in induction, regulation and amplification of humoral and cell mediated immune responses to viruses. These lead to the extrinsic effect of macrophages on other virus-infected cells or free virus, and the intrinsic effect on viruses within macrophages. While these interactions usually appear to be protective, immunopathologic consequences as well as macrophage dysfunctions have also been noted. The outcome of any given interaction (viral elimination, persistence, latency or transformation) varies markedly with the type of macrophage. The molecular mechanisms involved in these very diverse macrophage-virus interactions are currently under study.

The herpes simplex virus type 1 (HSV-1) alpha protein ICP0 trans-activates HSV-1 early genes in transient expression assays. To investigate the function of ICP0 during HSV-1 infection, we have lowered the level of ICP0 by use of a recombinant plasmid that has been engineered to express the antisense message. Cell lines were constructed which stably carry the antisense plasmid. Total protein profiles from infected antisense cell lines showed that the level of ICP0 was reduced to less than 10% of the wild type level in two of the cell lines. However, reducing the level of ICP0 did not have a significant effect on the expression of HSV-1 early or late genes. The polypeptide patterns for the remaining infected cell polypeptides were similar in that no bands were absent although there were some quantitative differences. The level of two early proteins, glycoprotein B and glycoprotein D was reduced in one of the cell lines, however, levels were nearly equivalent to the control infection for two other cell lines tested. Virus yields were the same for the antisense cell lines and for parent cells. Decreased ICP0 levels did not lead to more restrictive phenotypes for an alpha 4 or alpha 27 mutant as protein patterns were similar for these mutants in antisense and parent cells. Therefore, while ICP0 has been demonstrated to be a strong inducer of gene expression in transient expression assays, it does not appear to have a major role as an activator during the productive infection of tissue culture cells.