Virus particles in normal prostate tissues of mice from ten strains, with special reference to type-B virus particles

Prostate tissues of a total of 61 normal mice from 10 different strains, including high (C3H/Dm, RIII/Dm, and A/Dm) and low (BALB/c/Dm, C3Hf/Bi/Dm, and C3Hf/He/TEX) mammary cancer, and high (AKR/Dm) and low (CBA/J/Cr, SJL/J/Cr, and C57/BL/6/TEX) leukemia strains were examined by electron microscopy for the presence of virus particles. These studies demonstrated that type-B virus particles were present in normal prostate tissues of some old mice from all the three high (C3H/Dm, RIII/Dm, and A/Dm) and one low (BALB/c/Dm) mammary cancer strains. They further demonstrated that varying number of type-C virus particles were present in prostate tissues of some young and old mice, including those from all the 10 strains, especially in a larger number in older mice, and that intracisternal type-A virus particles were observed in all the mice examined. Immunological characterization of type-B virus particles by fixed immunofluorescence tests and immunoelectron microscopy revealed that type-B virus particles in normal prostate tissues of old C3H/Dm and A/Dm mice are morphologically and immunologically similar to the mouse mammary tumor virus. Thus, prostate tissues of mice can be a potential source of horizontally transmitted mammary tumor virus in mice of at least some high mammary cancer strains.