Kenneth S. S. Chang

Properties of RBL-5 Leukemia Cells Cultivated In Vitro

RBL-5 leukemia induced by Rauscher murine leukemia virus (R-MuLV) carried in the ascites form in C57BL/6 mice was cultivated in vitro and passaged continuously. Both low- and high-passage cells released the same level of murine leukemia virus, as detected by the XC plaque assay. Membrane antigens of the cultivated cells were also detected by the indirect immunofluorescence assay. Both low- and high-passage cells showed the same activity of antigen detectable by anti-R-MuLV serum, whereas only the high-passage cells reacted strongly against a syngeneic antiserum to RBL-5 crude membrane (CM). The oncogenicity of the low and high passages of the cultivated cells was compared with the ascites cells. The results indicated that the oncogenic potential of the cells gradually decreased during in vitro passage. The accumulation or retention of CM antigen on the membrane of the high-passage cells suggested that their decreased oncogenic potential might be due to increased immunogenicity and/or immunosensitivity. This strengthened the hypothesis that the cellular transplantation antigens are not identical to type C viral antigens, since the R-MuLV antigens were not altered during passage in vitro.

Production of antibodies against feline leukemia and sarcoma viruses and the feline oncovirus-associated cell membrane antigen in strain 2 guinea pigs

Abstract Cloned cell lines of guinea pig tumor induced by the Snyder-Theilen strain of feline sarcoma virus with feline leukemia virus subgroup C as helper, ST-FeSV (FeLV-C), have been established. The cell line releases high titers of ST-FeSV (FeLV-C) (10 3 −10 4 FFU/0.2 ml) and 1 log excess of FeLV-C. In vivo studies of one of the cell lines, GPTC C1 1 , showed that as little as 100 cells could induce tumors in weanling guinea pigs. The tumors progressively grew and eventually killed the animals within 23 days. Sera from guinea pigs carrying tumors contain antibodies to FeLV group-specific antigen, FeLV-C virus envelope antigen, and feline oncovirus-associated cell membrane antigen (FOCMA). The three groups of antibodies seem to be distinct as demonstrated in the absorption tests with appropriate antigens.

Immunogenic properties of a nonproducer malignant tumor induced by murine sarcoma virus.

Summary A cloned cell line H-11 (HP) derived from an MSV-induced neoplasm (a hemangiosarcoma) was found to possess virus-specific tumor rejection antigen(s). The specific nature of the immune response was established through the use of a polyoma virus-induced neoplasm #89 both in cross immunization and cross challenge experiments. Virus antigens or surface antigens associated with virus production are not responsible for tumor rejection since virus production could not be detected, nor were any viral fingerprints of MSV found by the several assays used.