Joint Action of West Nile Virus and Chemical Carcinogens in Production of Papillomas in Mice2

Abstract

Skin papillomas occurred with greater frequency in mice given West Nile virus intraperitoneally during a 10-day course of skin painting with 3-methyl-cholanthrene or henzo[a]pyrene than in mice given the chemical carcinogens alone. Carcinoma incidence was also increased, but only in proportion to the increased incidence of papillomas; the frequency with which carcinoma developed in papillomatous skin was not influenced by the virus infection. Papillomatosis was not increased when virus administration was delayed until after the course of methylcholanthrene applications. Ancillary studies provide evidence against the possibilities that virus-caused deaths eliminated papil-loma-resistant mice, or that mice most susceptible to papillomatosis are less susceptible to the virus infection. The virus was demonstrated in the skin of both control and carcinogen-treated mice at 3 and 4 days after intraperitoneal virus administration. Chi-square analysis indicates that the observed differences would rarely occur by chance.