Natural killer (NK) cells are an important component of cellular antiviral immunity. Recent studies show that interferon (IFN) promotes the selective lysis of Ad2/5 infected cells by activating NK cells and protecting uninfected cells (IFN mediated cytoprotection or IFN MCP) but not Ad infected cells from NK cell mediated lysis. Expression of a single Ad gene, early region 1A (EIA), blocks IFN MCP. This offers the first opportunity to study the interference of IFN MCP by a single viral gene. Preliminary genetic analysis reveals that expression of sequences in the first exon of EIA is necessary for inhibition of IFN MCP. Expression of SV40 LT, which shares homologous sequences with the first exon of EIA, also inhibits IFN MCP. The homologous regions of EIA and SV40 LT have been recently shown to bind specific cellular proteins (e.g., p105 retinoblastoma (Rb) gene product; p107; p60, cyclin A) which has con-elated with some of the biological activities of these viral oncoproteins. Based on these studies, it appears that the inhibition of IFN MCP by SV40 LT and Ad EIA is mediated through the same cellular pathway, likely by interacting with specific, common cellular protein(s). The first specific aim of this proposal: To map, by mutational analysis, the genetic subregion(s) responsible for ElAs inhibition of IFN MCP and to determine if the ability of mutant EIA proteins to bind specific cellular proteins (p60 (cyclin A), p105 (Rb), pl07, p300) correlates with ElA mediated inhibition of IFN MCP. Human papillomavirus (HPV) early region 7 (E7), like SV40 LT, share homologous sequences with the first exon of ElA . However, preliminary studies show that HPV E7 expression in HeLa cells does not block IFN MCP. The second specific aim of this proposal: To determine if expression of HPV16 or 18 E7 gene products in other types of human cells inhibits IFN MCP. The following approaches will be used: a) Comparison of IFN MCP in SV40 LT or HPV16 E7 expressing keratinocyte and fibroblast cell lines. b) Determination of the significance of IFN-induced, downregulation of E7 expression in HPV16/18 transformed human cell lines in modulating the inhibition of IFN MCP. c) Determination of the relationship between level of E7 expression and IFN MCP.
