Transformation By Polyoma Virus And Simian Virus 40

Transformation of ultraviolet-irradiated human fibroblasts by simian virus 40 is enhanced by cellular DNA repair functions

Human fibroblasts irradiated with ultraviolet light were either tested for survival (colony formation) or infected with simian virus 40 and examined for transformation (foci formation). For normal cell cultures, the fractions of surviving colonies which were also transformed increased with increasing irradiation dose. In contrast, little increase in the transformation of ultraviolet-irradiated repair-deficient (xeroderma pigmentosum and xeroderma pigmentosum variant) cells was observed. Similar experiments with xeroderma pigmentosum variant cells treated with caffeine following irradiation indicated that, under these conditions, the deficient cells produced more transformants among the survivors of ultraviolet irradiation than did unirradiated cells. These results suggest (1) that DNA repair functions, not DNA damage per se, are required for enhanced viral transformation in normal cells; (2) that functions involved in excision repair and functions needed for replication of ultraviolet-damaged DNA appear necessary for this stimulation; and (3) that blocking DNA replication in ultraviolet-irradiated xeroderma pigmentosum variant cells by caffeine enhances viral transformation.

Some aspects of the role of viruses in cancer

The cells of tumours induced by many oncogenic DNA viruses, or cells transformed in vitro, contain virus-specific T and transplantation antigens; these have been described for SV40 virus, polyoma virus and adenoviruses. The investigation of viruses as causes of malignant disease in man has sought to establish whether tumour cells possess these virus-specific proteins; however, to date and with the limitations of present techniques, this enquiry has not demonstrated the above viruses as causal of human cancer. More recent studies with herpesvirus type 2 (HSV-2) have shown this virus to transform animal and human cells in culture, and induce cancer in experimental animals: for these reasons, many researchers have suggested that this agent may be an agent of some forms of cancer, in particular carcinoma of the cervix. The possible association of HSV-2 with human malignant disease is discussed.

Detection of SV40 T antigen with labelled antibodies: radioimmunoassay and autoradiography

SV40 T antigen, partially purified from SV80, a human cell line, has been used to develop a sensitive solid phase radioimmunoassay. In this assay SV40 T antigen was immobilized on microtiter plates, reacted with hamster anti-SV40 T antibody and subsequently with 14C-labelled anti-hamster IgG. The test detected approximately 20 ng of partially purified SV40 T antigen and is rapid and more convenient than the complement fixing reaction. An immunoautoradiographic method which permits the determination of the cellular localization of SV40 T antigen and which is possibly more sensitive than the indirect immunofluorescence method is also described.

SV40 induced polypeptides in infected and transformed cells

5 structural (VP) and 3 non-structural (NSVP) SV40 induced polypeptides which display two kinetic patterns of synthesis are identified in infected cells. NSVP 1 and 2 are "early" functions of which only NSVP 1 is present in transformed cells; NSVP 3 is "late" function which is also present in a line (T-22) of transformed AGMK.

Regression of warts. An immunological study

Altogether 173 patients with warts were under observation for at least 3 and in most cases 6 months. In 80% of the patients wart-virus antibodies were present and could be measured by immunodiffusion (I.D.) and in 20% also by complement-fixation (C.F.) techniques. The mean duration of the warts in patients with C.F. antibodies was 0-6 years and in the others 1-9 years. The occurence of C.F. antibodies (IgG) was associated with rapid healing; 75% of these patients were cured during the first 2 months of the observation period. In contrast, of the patients with antibodies measurable only by the I.D. technique (IgM and/or low titres of IgG), only 16% were cured during the first 2 months and they had a fairly constant cure-rate (approximately 9% per month) during the 6 months' observation period. The results indicate that the cure of warts is partly connected with immunological phenomena, especially with the presence of C.F. antibodies. In other cases wart regression may be mainly a non-immune process, perhaps due to a limited lifespan of wart cells.

Demonstration of oncogenic potential of mammalian cells transformed by DNA-containing viruses following photodynamic inactivation

The oncogenic properties of hamster embryo cells transformed by herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) and SV40 virus following photodynamic inactivation using neutral red were determined by subcutaneous inoculation into newborn Syrian hamsters. Cells transformed by all three viruses produced palpable tumors after different latent periods. Histopathological examination showed that HSV-2 tumors were fibrosarcomas and metastases were often seen in the lungs. HSV-2 primary tumors were reinoculated subcutaneously into weanling hamsters; they developed palpable tumors within 2 weeks. HSV-specific antigens were detected in the cytoplasm and/or on the surface of both the HSV-1 and HSV-2 tumor-cell cultures by the indirect immunofluorescence technique. The same method revealed SV40 tumor antigen in the nuclei of the SV40 tumor cells. Sera from HSV or SV40 tumor-bearing hamsters gave positive reactions when tested against HSV-infected hamster cells or SV40-infected monkey cells, respectively. These results demonstrate that herpes simplex virus and SV40, whose infectivity was lost following photodynamic inactivation, retained the virus genetic information necessary for transformation of normal cells to an oncogenic phenotype.

Transcription of simian virus 40. II. Hybridization of RNA extracted from different lines of transformed cells to the separated strands of simian virus 40 DNA

The amount of simian virus 40 (SV40) DNA present in various SV40-transformed mouse cell lines and "revertants" isolated from them was determined. The number of viral DNA copies in the different cell lines ranged from 1.35 to 8.75 copies per diploid quantity of mouse cell DNA and from 2.2 to 14 copies per cell. The revertants had the same number of viral DNA copies per diploid quantity of mouse cell DNA as their parental cell lines. (However, they showed an increased number of viral DNA copies per cell due to their increased amount of DNA.) By using separated strands of SV40 DNA, the extent of each DNA strand transcribed into stable RNA species was determined for the transformed and "revertant" cell lines. From 30 to 80% of the "early" strand and from 0 to 20% of the "late" strand was present as stable RNA species in the cell lines tested. There was no alteration in the pattern of the stable viral RNA species present in three concanavalin A-selected revertants, whereas in a fluorodeoxyuridine-selected revertant there appeared to be less viral-specific RNA present in the cells.