Active HSV-1 immunization prevents the cocarcinogenic activity of HSV-1 in the oral cavity of hamsters.

Previous investigations have demonstrated that herpes simplex virus (HSV) increased the oral carcinogenic activity of 7,12-dimethylbenz[a]anthracene (DMBA) probably by enhancing the DMBA-induced amplification and overexpression of c-erb-B-1 proto-oncogene in hamster buccal pouch epithelium. The present study investigated the effect of active type 1 HSV (HSV-1) immunization on the development of oral cancer induced by HSV-1 and DMBA, alone or in combination, in the hamster buccal pouch. The results were similar to our previous report in that HSV-1 significantly enhanced the oncogenic effect of DMBA, and the numbers of pouches harboring tumor nodules and the numbers and sizes of tumors developed by topical DMBA were significantly increased by HSV-1 inoculation to the site of the DMBA application. Although HSV-1 immunization did not alter the carcinogenic activity of DMBA in animals receiving topical DMBA in combination with mock inoculation, it prevented the cocarcinogenic effect of HSV-1 in animals receiving topical DMBA in conjunction with HSV-1 inoculation. These data indicate that active HSV-1 immunization completely obstructs the co-oncogenic effect of HSV-1 in the oral cavity of hamsters.