Inability to predict mammary tumorigenesis in strain A mice from presence of mammary tumor virus or antigen in the milk

Strain A females were milked and their milk was tested for mammary tumor virus (MTV) by the hyperplastic alveolar nodule test and for MTV antigen by microimmunodiffusion. An attempt was made to correlate these results with later occurrence of mammary tumors in the females. There was not full agreement between the results of the test for the presence of the MTV and those of the test for MTV antigen, and from these results it was impossible to predict accurately whether a specific female would later develop a tumor. It is concluded that, in this strain, factors other than the MTV can be the determinant in whether the individual female will develop a tumor.

Genetic transmission of viruses that incite mammary tumor in mice

Electron microscopy, immunofluorescence, and bioassay demonstrated the presence of a mammary tumor inciting virus in untreated mice of three different inbred strains, and in irradiated or urethan-treated mice of two other mouse strains, indicating the ubiquitous nature of this group of viruses. In general these viruses are transmitted vertically by the gametes of the mouse strain in which they naturally occur. The virus is present in every cell, although often in an incomplete form. If a mammary tumor inciting virus is introduced into a different mouse strain, only milkborne transmission will take place, after which the virus is found in a limited number of tissues. It has been speculated that mammary tumor inciting viruses are transmitted as genetic factors of the host strain to which they belong. There is some evidence that a repressor, produced by a regulator gene, controls the rate of release of such a genetically transferred virus. Repression can be abrogated by a carcinogenic treatment. The repressor would also cause resistance to a superinfecting mammary tumor inciting virus by interference with its replication.

Mammary tumor virus antigen: sensitive immunoassay

A rapid, sensitive immuno-assay for mammary tumor virus antigen based on inhibition of passive hemagglutination has been developed. The method permits measurement of this antigen in mouse milk from which the fat has been removed.

Isolation of the nucleic acid of mouse mammary tumor virus (MTV)

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Immunology of the mouse mammary tumor virus: comparison of mammary tumor virus with the agent found in C3Hf/Crgl mice

C3Hf/Crgl mice, containing no biologically active mammary tumor virus, nonetheless possess both type-B virus particles and a component which cross-reacts serologically with the mammary tumor virus. Neutralization studies and the immunodiffusion assay for measuring the antigenicity of the mammary tumor virus indicate that transfer of the virus particles from C3Hf to BALB/cCrgl mice is accompanied by transfer of the cross-reacting antigenic component.