A new variant of Rous sarcoma virus-33 nondefective, pathogenic for rats.

Rous sarcoma virus-33 (RSV-33) belongs to RSVs that have the least number of passages beyond its isolation from chicken tumor No. 1 among all current strains of RSV. Biological characterization indicated that it was pathogenic for rats. The results of the proviral restriction enzyme analysis showed that the established rat tumorigenic cell lines were the most likely infected by the same virus having a full-length genome.

Identification of transformation-specific proteins synthesized in cryptovirogenic mammalian cells.

The cryptovirogenic PR-RSH-19 (H-19) hamster cell line, derived originally from a tumour induced by the virus rescued from XC cells by transfection, was studied. The pp60v-src protein was detected by immunoprecipitation with sera from tumour-bearing rabbits (TBR sera) from lysates of H-19 cells. A closely related protein p60 was precipitated by antiserum obtained from hamsters with tumours induced by H-19 cells. The pp60v-src of H-19 cells possesses an associated kinase activity. These results are consistent with the notion that the detected pp60v-src protein is a product of the cryptic sequences in H-19 cells.

Partial characterization of rat cell lines infected by a Rous sarcoma virus-33.

Rous sarcoma virus-33 (RSV-33) was obtained from a sample of chicken Rous sarcoma which had been dried and stored in 1933. RSV-33, like the RSV-29, has the minimal number of passages beyond its isolation from chicken tumour No. 1. Our experiments demonstrated that the Rous sarcoma virus-33 was replication non-defective and was pathogenic for rats. Established rat tumorigenic cell lines express the viral genome. All three species of viral RNA were detected and v-src proteins and gag polyproteins were identified as well in cells of R9 and R74 lines. The virus can be rescued from cells of R9 and R74 lines, thus indicating that the cells are virogenic. The cells of a permanent tumorigenic line RT1 are infected but not transformed by RSV-33. Although they contain a complete proviral genome, they do not express detectable virus-specific RNA. The virus is not rescuable from RT1 cells under in vivo conditions. Proviral DNA analysis showed that the RSV-33 contained a full-length genome, including the env gene, in contrast to the RSV-29 which was found replication defective.

Monoclonal antibody to a human osteogenic sarcoma cell line.

Monoclonal antibodies against a human osteogenic sarcoma cell line were prepared by production of a somatic cell hybrids between the spleen cells from U-393OS--immunized mice and the mouse myeloma cells SP2/0. From 7 producing and well-growing clones only one--B-0S12--produced antibodies, reactive preferentially with osteosarcoma cells as identified by binding second antibodies and 125I-labeled Protein A. This antibody was tested against a panel of normal and tumor cell targets to determine the pattern of the antigen detected. The monoclonal antibody reacted strongly against U-3930S cells and another human sarcoma in vitro and more weakly against human fibroblasts, peripheral lymphocytes, red blood cells and was negative against mouse fibroblasts. When tested against a panel of unrelated human tumor cell lines, B-0S12 antibody was positive with melanoma cells and negative with cells from bladder, cervix and mammary carcinoma. These cross reactions suggested, that the antibody is reactive with a protein, expressed on different tumor types. This protein is not expressed on the cell surface and is probably associated with cytoskeleton, as revealed by immunofluorescence experiments. Western-blot analysis of a cytoskeletal preparation of U-3930S cells suggests, that B-0S12 antibody recognizes a protein with Mr 55 kD. Further studies are needed to characterize the molecules, carrying the epitope, identified by this monoclonal antibody.

Effects of prenatally administered cyclophosphamide on postnatal immunocompetence in mice.

The effect of prenatal exposure to cyclophosphamide on postnatal somatic development and the function of the immune system was studied in random-bred ICR mice. In a dose of 1.2 mg (i.e. an average of 23.5 mg/kg pregnant female body weight), cyclophosphamide administered on the 16th day of gestation (a vaginal plug = day 1) caused both prenatal and postnatal retardation of growth. In the 3rd, 5th and 8th postnatal week, increased proliferation of the splenocytes of the experimental mice was observed in vitro, with changes in the intensity of their activation by Concanavalin A and lipopolysaccharide. In the 3rd week their capacity for activation by lipopolysaccharide was markedly lower than their activation by Concanavalin A and phytohaemagglutinin. No differences were observed between proliferation and activation of the splenocytes of the offspring of the control and the experimental mice at the age of 16 weeks. After depression at three weeks, the delayed type hypersensitivity reaction showed a tendency to increase; in the offspring of the experimental mice the haemagglutinin titre against sheep RBC was raised during the whole period of the investigation. At 16 weeks, the activity of peritoneal macrophages was likewise elevated.