Mouse Mammary Tumor Virus Infection Research Articles

Direct detection of exogenous mouse mammary tumor virus sequences in lymphoid cells of BALB/cfC3H female mice.

The presence of exogenous mouse mammary tumor virus (MMTV) (C3H) DNA sequences in lymphoid tissue (spleen, bone marrow, and thymus) and nonlymphoid tissue (liver and kidney) of BALB/cfC3H female mice was directly assessed by DNA hybridization methods. Lymphoid tissues were found positive for integrated MMTV(C3H) sequences in females as young as 4 weeks. In most samples, the level of splenic MMTV(C3H) infection was low (2 to 5%). Infection remained throughout the life of the animal. The percentage of spleen samples found positive for exogenous viral infection was significantly higher in females bearing mammary tumors, whether virgin or multiparous. Liver and kidney DNAs were negative for exogenous MMTV sequences, suggesting tissue type selectivity in MMTV infection.

Decrease in mammary tumour incidence in virgin C3H mice given interferon only while suckling.

A high proportion of females of the C3H strain of mice develop tumours of the mammary gland which are caused by mouse mammary tumour virus (MMTV) transmitted through the milk. We have examined whether administration of mouse interferon (IFN) to nursing mothers and/or their suckling offspring only during the period of nursing, can affect the incidence of tumours developing in these animals. In two separate experiments, animals receiving IFN by direct injection while suckling, and remaining virgin showed a marked and statistically significant decrease in tumour incidence. Mice receiving the same or a tenfold higher dose of IFN while lactating showed no such reduction in tumour incidence, even if they had also received IFN while suckling. The results suggest that IFN can affect the initial establishment of the MMTV infection in suckling mice sufficiently to delay tumour development provided the animals are not exposed to the hormonal stimulus of pregnancy and lactation.

Distribution of mouse mammary tumour virus antigens in RIII mice as detected by immunofluorescence on tissue sections and by immunoassays in sera and organ extracts.

Organs of RIII mice at various physiological stages were tested for mouse mammary tumour virus (MMTV) antigen expression. Indirect immunofluorescence was used with three monospecific antisera to localize one envelope glycoprotein, gp47, and two core proteins, p28 and p8. These virus-specific antigens gave characteristic fluorescent patterns in the mammary tissues and were also detected in thymus and salivary gland sections of some mice. The amounts of antigens gp47 and p28 were measured by immunoassay in sera and organ extracts of corresponding samples of mice. Sera of mice of both sexes contained virus antigens from the suckling age onwards. Although ingested virus could be traced in suckling mice, weanlings were characterized by the absence of virus expression except in lymph nodes. This location points to the possible role of lymphoid tissue in producing the antigens of the blood and in disseminating the infection. In adult animals, virus antigens were present in salivary glands, digestive tract, lymph nodes, male genital organs and female mammary glands. Antigen expression, even found in the mammary glands of virgin mice, was strikingly increased by pregnancy, lactation and (or) ageing, the highest values being found in mammary tumours. The results for milk-borne MMTV infection in RIII mice are compared with those obtained previously in Swiss albino mice.