The etiology of cancer resembles that of many other diseases in that multiple factors may be required. Because of this, the role or viruses in the etiology of human cancers is especially difficult to assess. When animal tumor systems were used as models, the roles of various predisposing characteristics in virus on‐cogenesis were elucidated. Extrapolation of these findings to the human diseases suggests the importance of genetics, age, hormones, immune competence, and stress in determining susceptibility to tumor development in individuals infected with an oncogenic virus. The importance of cofactors in induction of those human tumors most strongly associated with virus infection, including Burkitt's lymphoma, nasopharyngeal carcinoma, cervical carcinoma, acute myelogenous leukemia, and breast cancer, is reviewed. Understanding of the role of these cofactors in virus carcinogenesis may lead to disease prevention through elimination of one or more of the cofactors. Cancer 40:419–429, 1977.
A virion-associated antigen, CP-1, was detected on the surface of hamster cells after transformation by inactivated herpes simplex virus type 1. Presence of the CP-1 antigen on the cells correlates with the synthesis of antibody by tumorbearing hamsters capable of neutralizing both herpes simplex virus types 1 and 2.
The interaction of endogenous type C viruses with superinfecting herpes simplex virus type 2 (HSV-2) was investigated in two murine cell lines. Replication of HSV-2 was suboptimal in random-bred Swiss/3T3A cells and, in initial experiments, infection with a low virus-to-cell ratio resulted in carrier cultures with enhanced murine leukemia virus (MuLV) p30 expression. Immunofluorescence tests with Swiss/3T3A cells productively infected with HSV-2 also showed HSV-associated cytoplasmic antigens and enhanced MuLV p30 expression when compared with uninfected controls. Inactivation of HSV-2 with UV light did not abolish this reaction, although the number of cells expressing p30 was reduced. HSV-2 replicated more efficiently in a line of NIH Swiss cells (N cl A cl 10). These cells are not readily inducible for type C expression by conventional methods; however, untreated and UV-inactivated HSV-2 induced both HSV-2associated antigens and MuLV p30 in these cells. Although the Birch strain of human cytomegalovirus induced MuLV p30, neither mouse cytomegalovirus nor vesicular stomatitis virus induced MuLV p30 in either cell line.
Mouse cells (line N cIA cl10) contain 1.2-2.5 ng murine leukaemia virus (MuLV) p30 antigen/mg of protein; this amount of antigen is measurable by competition radioimmunoassay (RIA) but is not detectable by indirect immunofluorescence (IF). Infection of N cIA cl10 cells with herpes simplex virus type 2 (HSV-2) induces expression of MuLV p30. Induction by HSV-2 does not require either cell or virus DNA synthesis and is optimal 8 h post infection when cells at 50-70% confluence are infected at a multiplicity of infection (MOI) of 5-8 PFU/cell. At an MOI of 2.5, 70-80% of the cells express HSV antigens while none of the cells express p30; at an MOI of 5.0, 70-80% of the cells express HSV antigens but 55% of the cells express p30. Using the conditions reported in this paper for preparation of competing antigen, induction of p30 by HSV-2 (strain 333) infection is not measurable by competition RIA.
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