Immunologic studies with mouse mammary tumor viruses: comparative studies with spontaneous mammary tumor cell vaccines from five inbred mouse strains.

Vaccines were prepared from cells of primary spontaneous mammary tumors (MT) of RIII/Imr, GR/Imr, C3H/Imr, A/Imr, and C3HfC57BL/Imr mice. Each vaccine was used to immunize "murine mammary tumor virus (MuMTV)-free" BALB/c/Imr and C57BL/Imr mice before challenge with infectious RIII-MuMTV, GR-MuMTV, C3H-MuMTV, and A-MuMTV. RIII-MT and C3H-MT cells protected mice against tumorigenesis by all four MuMTV's; GR-MT cells protected against all but the RIII-MuMTV challenge; A-MT cells were ineffective against challenge by all four MuMTV's and significantly enhanced development of A-MuMTV-induced tumors. The activity of the C3H-MT cells was not seen when C3HfC57BL cells, free of the standard C3H-MuMTV, were used. The same cell vaccines were inoculated into the five donor strains of mice in attempts to prevent spontaneous MT in these high-incidence strains, which are naturally infected with MuMTV at birth. None of the vaccines prevented tumorigenesis in these mouse strains although delays in the appearance of tumors were observed in RIII and GR mice inoculated with either isologous MT cells or C3Hf-MT cells. The role of viral antigens acting alone or in concert with cellular antigens is discussed.

Serologic responses to murine mammary tumor virus (MuMTV) in MuMTV-exposed laboratory personnel.

A retrospective study was conducted to determine whether exposure to murine mammary tumor virus (MuMTV) induced MuMTV-specific serologic responses among intramural laboratory personnel. Results obtained with a panel of five purified structural proteins of the RIII mouse strain milk-derived MuMTV (gp55, gp34, p28, p18, and p12), by means of the enzyme-linked immunosorbent assay to assess antibody binding, established that MuMTV exposure resulted in highly significant increases in serologic responses to these test antigens as compared to age- and gender-matched controls without overt contact with MuMTV. Furthermore, immunoreactions to gp55 and gp34 were found not to be directed to the carbohydrate moieties of these glycoproteins. Similar results were obtained by assays of human immunoglobulin binding to Western blots of MuMTV proteins. These increased MuMTV-specific immunoreactivities, in general, were found to be related to degree and length of exposure to this virus. These results with MuMTV suggest the possibility of important human immune response differences between exposure to type B (MuMTV) and animal type C (leukemia-sarcoma) RNA tumor viruses, perhaps reflective of sensitivity to antibody dependence of complement-induced virolysis.

Comparative studies of purified subviral component vaccines and formalin-treated mammary tumor viruses from four inbred strains of mice.

Formalin-treated virus vaccines were prepared from purified murine mammary tumor viruses (MuMTV) from 4 inbred strains of mice: RIII/Imr, GR/Imr, C3H/Imr, and A/Imr. In addition, subviral components were isolated from these 4 strains and purified to homogeneity. The inactivated viruses, their major envelope glycoproteins (gp50-gp55), and their major internal core protein (p28) were emulsified in complete Freund's adjuvant and used as vaccines for prevention of mammary tumors in mice. All 4 Formalin-treated virus vaccines reduced significantly the incidence of mammary tumors in "virus-free" C57BL and BALB/c mice when inoculated prior to challenge with live MuMTV. The RIII-, GR-, and A-MuMTV strains showed extensive heterologous cross-protection, whereas the C3H-MuMTV strain showed significant protection only against C3H- and A-MuMTV challenge. The major viral glycoproteins gp50-gp55 reduced significantly the tumor incidence when mice were challenged with isologous infectious virus after immunization, although these glycoproteins showed different degrees of cross-protection than did the same virus strains used as "intact" but Formalin-treated preparations. RIII-gp55 and GR-gp55 cross-protected against each other but not against challenge with C3H- and A-MuMTV strains; the A-gp50 protected against challenge with A- and RIII-MuMTV strains; C3H-gp55 demonstrated limited activity against C3H-MuMTV challenge only. The internal viral core proteins (p28) were ineffective in all systems studied. The same vaccines were tested in MuMTV-positive, high-tumor-incidence strains from which they were derived. At best, the appearance of spontaneous tumors was delayed in a few experimental sets; eventually, all mice developed mammary tumors. The foster-nursed C3HfC57BL strain of mice, which is not exposed to exogenous MuMTV during suckling and which develops mammary tumors after activation of the endogenous virus genome later in life, was responsive only when the heterologous GR-MuMTV Formalin-treated vaccine was used. The association between the ability of virus vaccines to protect a mouse strain and the degree of natural virus expression in that strain is discussed.

Responses of serum from breast cancer patients to murine mammary tumor virus: fact or artifact?

For determination of whether breast cancer patients possessed specific serological responses to murine mammary tumor virus (MuMTV), IgG-binding levels were monitored by antibody binding to electrophoretically separated viral proteins (Western blotting and immunodetection) and by the enzyme-linked immunosorbent assay (ELISA) against a panel of five structural proteins (gp55, gp34, p28, p18, and p12) purified from milk-borne MuMTV of the RIII isogeneic mouse strain. No significant antibody reactions were found for sera from 30 cancer patients by the immunoblotting assay, and comparative ELISA studies of 111 patients with malignant mastopathies and 122 healthy, age-matched women revealed no significantly increased mean antibody responses against gp55, gp34, p28, or p12 in breast cancer patients as compared to the responses in the control group. Only for p18 was there a significant increase in mean IgG-binding levels in cancer patients. Additional assays of antibody binding to viral antigens were performed by the cellular immunofluorescence test on MuMTV-expressing cells. These studies also failed to demonstrate greater immunoreactivity of sera from patients as opposed to the immunoreactivity of sera from healthy controls.

Cytogenetic changes induced in human diploid fibroblasts by tsA58 SV40 at permissive and restrictive temperatures.

Human diploid fibroblasts have been transformed by ts A58 SV40. At the permissive temperature, apparent chromosome and chromatic rearrangements were observed in a high percentage of cells and the frequency of SCE increased. If the transformed phenotype returned to normal at the restrictive temperature these alterations also returned to normal levels. Chromosome banding demonstrated many apparent chromosomal rearrangements in which diffuse staining material was joining intact chromosomes end-to-end and forming pseudostructural abnormalities. Homogeneously staining regions associated with gene amplification or virus-induced alterations in the coiling and stickiness of telomeric regions are possible mechanisms.

Assignment of the T-antigen gene of simian virus 40 to human chromosome C-7.

Hybrid cell clones between mouse cells deficient in thymidine kinase (EC 2.7.1.21) and two different human cell lines transformed by simian virus 40 (SV40) and deficient in hypoxanthine phosphoribosyltransferase (EC 2.4.2.8) were examined for SV40 tumor (T) antigen(s). Concordant segregation of the gene(s) for SV40 T antigen and human chromosome C-7 was observed in these hybrids. The human chromosome C-7 which contains the gene(s) for SV40 T antigen is preferentially retained by the majority of the hybrid clones tested. When hybrid clones positive and negative for SV40 T antigen, derived from the fusion of SV40-transformed Lesch-Nyhan fibroblasts with mouse cells, were fused with CV-1 permissive cells, SV40-specific V antigen was observed only in the cultures derived from fusion of the hybrid clones positive for T antigen. This result indicates a linkage relationship between human chromosome C-7, SV40 T-antigen gene(s), and SV40 genome(s) integrated in the human transformed cells.

Genetics of cell transformation by simian virus 40.

The results described in this paper indicate that the integration of the SV40 genome into human chromosome 7 results in the transformation of the human cells and in the expression of SV40-induced antigens. If integration of the SV40 genome in human chromosomes other than 7 ever occurs, it does not result in cell transformation and the expression of the virus-induced antigens. The expression of the SV40 T antigen in different monkey cells transformed by an adeno 7-SV40 hybrid is also related to a specific monkey chromosome. Somatic cell hybrids between normal nondividing mouse cells and SV40-transformed human cells behave as transformed cells and contain, without exception, the human chromosome 7 carrying the SV40 genome. Since no segregation into SV40 T antigen-negative hybrid clones was observed in these hybrids, it is inferred that the presence of the human chromosome 7 carrying the SV40 genome in the hybrids is mandatory for cell division.

A human protein related to the major envelope protein of murine mammary tumor virus: identification and characterization.

A human milk protein was isolated to apparent homogeneity and shown to be immunologically related to gp55, the major envelope glycoprotein of murine mammary tumor virus. Through the development of ultrasensitive protocols, which have wide applicability, immunological relatedness was corroborated by the demonstration of homologous protein sequences between the human and viral proteins.

Prevention of simian virus 40 tumors by hamster fetal tissue: influence of parity status of donor females on immunogenicity of fetal tissue and on immune cell cytotoxicity.

Fetal tissue from primiparous hamsters prevented simian virus 40 (SV40) tumorigenesis in male hamsters, whereas fetal tissue from multiparous hamsters did not. The parity status of normal (uninoculated) hamsters also influenced the cytotoxicity of their lymphoid cells against tumor cells. Lymph node cells from nonpregnant primiparous and multiparous animals were cytotoxic in microcytotoxicity tests against SV40, polyoma, and adenovirus 7 tumor cells, but were not active against control BHK cells. Lymph node cells from virgin female donors were inactive. Peritoneal exudate cells from these donors reacted in similar fashion against SV40 tumor cells in vitro and in adoptive transfer tests in vivo. However, the cytotoxicity of peritoneal exudate cells from multiparous hamsters was greatly reduced during pregnancy, a time when noncytotoxic humoral antibody reactive with surface antigen of SV40 tumor cells is present. This humoral antibody is not detected during first pregnancy, and peritoneal exudate cells obtained from pregnant primiparous hamsters demonstrated a high degree of cytotoxicity.

Defective repair of alkylated DNA by human tumour and SV40-transformed human cell strains.

We have identified a group of 8 (among 39) human tumour cell strains deficient in the ability to support the growth of adenovirus 5 preparations treated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), but able to support the growth of non-treated adenovirus normally. This deficient behaviour defines the Mer- phenotype. Strains having the Mer- phenotype were found to arise from tumours originating in four different organs. Relative to Mer+ strains, Mer- tumour strains showed greater sensitivity to MNNG-produced killing, greater MNNG-stimulated "DNA repair synthesis and a more rapid MNNG-produced decrease in semi-conservative DNA synthesis. Here we report that (1) Mer- strains are deficient in removing O6-methylguanine (O6-MeG) from their DNA after [Me-14C]MMNG treatment (Table 1); (2) Mer- tumour strains originate from tumours arising in patients having Mer+ normal fibroblasts (Fig. 1a, b); (3) SV40 transformation of (Mer+) human fibroblasts often converts them to Mer- strains (Fig. 1c, d); (4) MNNG produces more sister chromatid exchanges (SCEs) in Mer- than in Mer+ cell strains (Fig. 2).