Lymphocyte transformation for the detection of herpesvirus-induced tumor-associated antigens.

Cell-mediated immunity to fibroblasts transformed by herpes simplex virus type 2 was investigated with a lymphocyte assay system. The assay system was first standardized with phytohemagglutinin, a nonspecific stimulator of blastogenesis. Hamster splenic and blood lymphocytes reacted to phytohemagglutinin with a dose-response curve similar to that reported for other rodent species. Splenic lymphocytes from hamsters bearing isografts, induced by herpes simplex virus type 2, were transformed by cell-free virus-induced tumor antigens. The reactions with cell-free tumor antigens were dose-dependent and paralleled the findings with phytohemagglutinin. The initial transformation response of immune lymphocytes to homologous tumor antigens occurred after 72 hr incubation with antigen. Immune splenic lymphocytes from hamsters were also significantly stimulated with antigens obtained from cells productively infected with herpes simplex virus type 2. Immune lymphocytes were not stimulated with heterologous antigens from simian virus 40-transformed mouse or hamster cells. Likewise, lymphocytes from hamsters sensitized to cells transformed by simian virus 40 reacted with both simian virus 40-transformed mouse and hamster cells but did not react with cells transformed by a heterologous virus. The results suggest that under defined conditions a lymphocyte transformation assay may be useful for the specific detection of common viral-induced antigens on tumor cells.     

Characterization of rat embryo cells transformed by ts mutants and sheared DNA of herpes simplex virus types 1 and 2 and a derived tumor cell line

Four independent isolated lines transformed by ts mutant or sheared DNA of herpes simplex virus types 1 and 2 and one tumor cell line were characterized according to their behavior in assays of aggregation, growth in low serum, doubling times, saturation density, agglutination by lectins, uptake of metabolites, and production of plasminogen activator. The criteria used to select the transformed cells used in this study were the formation of altered foci of cells followed by the formation of a continuous cell line, the continuing expression of herpes simplex virus-specific antigens, and the tumorigenicity of the transformed cell lines. The results indicate that, whereas the one herpes simplex virus type 2-transformed cell line investigated showed many of the transformation parameters accepted as typical of cells transformed by the papovaviruses, the three herpes simplex virus type 1-transformed cell lines do not share or express many of these transformation parameters.     

Production of plasminogen activator by cells transformed by herpesviruses.

Plasminogen activator is produced by hamster cells transformed by human herpesviruses. These cell lines have previously been shown to be oncogenic when injected s.c. into newborn syngeneic hamsters. Lysis of fibrin overlays by these cell lines was plasminogen dependent. Normal hamster embryo fibroblasts and a hamster cell line transformed by PARA-7 (an adenovirus-SV 40 hybrid) failed to produced lysis. In separate experiments fibrin overlay of lytically infected secondary rabbit kidney cells did not show induction of this activity during the normal course of productive infection. The human cell line TE-85 clone F-5, a clonal cell line from a human osteogenic sarcoma, failed to produce plasminogen activator, but two separate clones of these cells that were morphologically transformed after exposure to UV-inactivated herpes simplex virus type 2 produced rapid lysis of the fibrin overlay. Clonal variation was observed in herpes simplex virus types 1 and 2-transformed hamster lines and is under investigation. It is suggested that plasminogen activator detection may serve as a convenient assay system for transformation of normal cells by herpesviruses.     

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.     

Reaction of antigens isolated from herpes simplex virus-transformed cells with sera of squamous cell carcinoma patients.

Antigens isolated from herpes simplex virus type 1, herpes simplex virus type 2, or cytomegalovirus-transformed hamster cells were tested against 66 sera from non-cancer individuals or patients with different types of cancer. By use of the microcomplement fixation procedure to quantify all antigen-antibody interactions, it was observed that 94% (p less than 0.001) of all sera from patients with squamous cell carcinoma reacted with antigens from herpes simplex virus type 1-transformed cells, while 84% (p less than 0.001) of the same sera reacted with antigen preparations from herpes simplex virus type 2-transformed cells. When sera from patients with adenocarcinoma, sarcoma, liposarcoma, and melanoma were tested against these antigens, there was no significant difference in their reactivity from sera of noncancer patients. When sera from all individuals (normal and cancer) were tested against antigens from cytomegalovirus-transformed cells, no significant reaction pattern developed. These studies are the first to describe the isolation of a reactive tumor-associated protein from herpes simplex virus-transformed cells.     

Specific non-immunoglobulin G antibodies and cell-mediated response to herpes simplex virus antigens in women with cervical carcinoma.

Non-immunoglobulin G-neutralizing antibodies to herpes simplex virus (HSV) type 2 were assayed in sera adsorbed with Staphylococcus aureus Cowan I. They were present in 8% of women with normal cervical smear and in 20, 41, and 74% of women with atypia, dysplasia, and cervical carcinoma, respectively. Lymphocytes of the patients were tested for in vitro transformation by killed HSV type 1 and HSV type 2 (HSV-2), as well as by mitomycin C-treated hamster cells transformed by HSV or other viruses or not transformed. Specific stimulation by the HSV-transformed cells occurred in 2, 22, and 40% of women with normal cervical smear, dysplasia, and carcinoma of the cervix, respectively. This frequency rose to 82% during treatment with irradiation and decreased to 0% after surgery. When HSV-2 virions were used as antigens to stimulate the lymphocytes, similar differences were found between the various groups, but they were less clear-cut, since 16% of the control women had lymphocytes responding to HSV. Non-immunoglobulin G antibodies to HSV-2 were not present in blood at the same time as cell response to HSV-2-transformed cells. There was also a negative correlation between neutralizing activities of the sera and the indices of lymphocyte stimulation, indicating a regulation between humoral and cell-mediated responses.     

Enhanced plating efficiency of herpesvirus DNA on herpes simplex virus type 1 DNA-transformed cells.

Partial resistance of hamster cells transformed by sheared herpes simplex virus (HSV) DNA to superinfection by intact HSV could be overcome by transfection with viral DNA's. HSV DNA plated more efficiently on HSV type 1 DNA-transformed hamster cells than on spontaneously transformed hamster or rabbit cells or on hamster cells transformed by other DNA viruses.     

Herpes-related polypeptides from a human cervical carcinoma cell line

Using antiserum against herpes simplex virus type 2 (HSV-2) infected cells, eight polypeptides with similar molecular weights could be immunoprecipitated from the nearly diploid, human cervical carcinoma cell line C4II and from HSV-2 transformed hamster and mouse cells. Only two of these polypeptides corresponded to those from HSV-2 infected cells, including the putative HSV-2 transformation-related 35K protein. Partial proteolytic cleavage products of the immunoprecipitated 35K polypeptides from C4II and HSV transformed hamster and infected cells were indistinguishable; however, viral DNA and mRNA corresponding to the 35K polypeptide could not be detected in C4II or in transformed hamster or mouse cells by dot blot hybridization. A similar mechanism of transformation for the human cervical carcinoma cell line and HSV-2 transformed cells is proposed.     

Tumor virus induction and host cell capacity inactivation: possible in vitro tests for photosensitizing chemicals

The responses of two in vitro mammalian virus-host cell systems to the photosensitizing chemicals proflavine sulfate and 8-methoxypsoralen (8-MOP) in the presence of light are described. Infectious simian virus 40 (SV40) could be induced from SV40-transformed hamster cells by treatment with proflavine plus visible light or 8-MOP plus near UV radiation. The same photosensitizing treatments inactivated the capacity of monkey cells to support the growth of herpes simplex virus. SV40 induction and inactivation of host cell capacity for herpesvirus growth might be useful as screening systems for testing the photosensitizing potential of chemicals. Advantages and disadvantages associated with each system are discussed.     

Detection of specific surface antigens by colony inhibition in cells transformed by papovavirus SV40

Specific antigens at the surface of SV40-transformed hamster cells were demonstrated by the in vitro colony inhibition and immunofluorescence tests. Antisera were prepared by inoculating hamsters either with purified SV40 or with human or marmoset SV40-transformed cells. The inhibition of colony formation by the transformed cells ranged from 46 to 100% in the presence of specific antibody and complement. Nontransformed hamster cells were not inhibited by the immune sera. Of the 22 sera tested, 12 were positive in the colony inhibition test and 14 were positive in the immunofluorescence test. Eleven of the 22 sera tested were positive in both tests. This positive correlation between the colony inhibition and immunofluorescence tests suggests that the two tests are detecting the same or similar antigens.     

Transformation of mouse cells after infection with ultraviolet irradiation-inactivated herpes simplex virus type 2.

A transformed mouse cell line (H238) was obtained following the infection of 238 mouse cells with ultraviolet (UV) irradiation-inactivated herpes simplex virus type 2 (HSV-2). The transformed cells produced tumors with a 100% incidence within 8 weeks in 6-week-old syngeneic BALB/c mice at an inoculum of 1 times 10(6). Indirect immunofluorescence (IF) tests revealed the presence of HSV antigens in the transformed cells. Antibodies to HSV-2 were found in the sera of tumor-bearing animals by neutralization and IF techniques. Neither HSV-2 infectious virus nor viral antigens could be detected by the transfer of transformed-cell DNA into permissive cells.     

Uninhibited growth and metastases of herpes simplex virus-transformed cells in virus-sensitized hosts.

Four established tumour lines of hamster cells transformed by herpes simplex virus (HSV) but not shedding the virus were examined for continued expression of virus-associated antigens. Hamster or rabbits, appropriately immunized to the tumour cells, produced virus-neutralizing antibody. The serum titres were invariably low, suggesting that only small quantities of virion antigen were present in the cells. Hamster sensitized to HSV and resistant to virulent virus challenge did not reject low numbers of tumour cells, nor was the incidence of lung metastases significantly reduced. Virus-sensitized lymph-node cells, readily cytotoxic for HSV-infected hamster embryo fibroblasts, did not lyse any of three transformed lines tested in an 18-h 51chromium release test. Animals that had their tumour excised demonstrated no or only modest resistance to tumour rechallenge. Thus, virus-specific transplantation rejection antigen could not be detected in the HSV tumour lines although low levels of virus structural antigens were present.     

Comparison of the immunogenicity of hamster cells transformed by adenovirus and Herpes simplex virus.

Hamsters vaccinated with adenovirus-transformed cells, modified by acetoacetylation or concanavalin A treatment, or with small numbers of living cells were partly or completely protected against challenge with 3 times 10-6 living cells. Treatment of vaccine cells with iodoacetate, Mitomycin C, neuraminidase plus Mitomycin C did not produce efficient vaccines. Herpes simplex virus-transformed cells treated by any of these procedures did not prevent, and frequently even enhanced, the growth of the homologous living cells; enhancement was often greater in female than in male hamsters. Protective and enhancing vaccines did not induce a different level of cell-mediated immunity, as detected by lymphocytotoxicity tests, which were positive for both homologous transformed cells and nontransformed hamster cells. In contrast, specific complement-dependent cytotoxic antibodies active only on adenovirus-transformed cells were induced by the protective acetoacetylated vaccine prepared from adenovirus-transformed cells; these antibodies were not present after nonprotective vaccinations. The appearance of herpes simplex virus tumors was delayed by treatment with the immunostimulant, Levamisole, or by preimmunization with Newcastle disease virus grown in SV40-transformed cells, but not by Newcastle disease virus grown in herpes simplex virus-transformed cells. Thus, only nonspecific treatments were able to impede herpes simplex virus tumor growth, while protection against adenovirus tumor was accompanied by specific cytotoxic antibodies.     

Detection of herpes simplex virus-related antigens in the nuclei and cytoplasm of biochemically transformed cells with peroxidase/anti-peroxidase immunological staining and indirect immunofluorescence.

Herpes simplex virus (HSV)-related antigens have been demonstrated in the nuclei and cytoplasm of human and mouse cells biochemically transformed by ultraviolet light-irradiated HSV. This was accomplished by using peroxidase/anti-peroxidase immunological staining and indirect immunofluorescence with rabbit antisera that had high neutralizing titers against the HSV-specific thymidine kinase activity and virus infectivity. HSV-1 antisera reacted with antigens in cells biochemically transformed by type 1 HSV, but not with those of cells biochemically transformed by type 2 HSV. Similarly, HSV-2 antisera reacted with antigens in cells biochemically transformed by HSV-2, but not with those in cells biochemically transformed by HSV-1. In contrast, herpes virus-related antigens were detected in cells cytolytically infected with HSV-1 and with HSV-2 by either type 1 or type 2 HSV antisera. These observations suggest that the antigens detected in the biochemically transformed cells were a type-specific subset of the HSV-related antigens synthesized in cells undergoing productive infection by HSV-1 and HSV-2.     

Characteristics of hamster cells transformed by the combined action of chemical and virus

Pretreatment of hamster cells with chemical carcinogen enhances transformation by a simian adenovirus, SA7. Such transformants were compared to cells transformed by SA7 alone for the presence of virus-specified antigens, and for the ability to clone in soft agar and to form progressively growing sarcomas in hamsters. The SA7 "T" antigen content and the relative cloning efficiencies in agar of cell lines of both groups were similar. Some cell lines obtained by pretreatment with chemical carcinogen, however, produced a higher incidence of tumors, suggesting that the chemical carcinogen was involved in the transformation of cells by virus. A further indication that these cells differed from cells transformed by virus alone was obtained with MCA-transformed fibroblast cell lines that were subsequently also transformed in vitro by SA7 to cuboidal (SA7 type) morphology. These MCA-SA7-transformed cells produced a higher incidence of sarcomas than cells transformed by virus alone, but a lower tumor incidence than the parental MCA line.     

HSV- and chemical carcinogen-induced amplification of SV40 DNA sequences in transformed cells is cell-line-dependent

Eleven simian virus 40-transformed cell lines from 5 different species were tested for their ability to amplify integrated simian virus 40 DNA upon infection with herpes simplex virus type I or treatment with various chemical carcinogens. Four cell lines were positive only for virus-induced gene amplification and two lines were positive for both carcinogen- and virus-induced gene amplification. Individual cell lines were assayed for the presence of an intact SV40 origin of replication, the expression of a functional SV40 T-antigen, and permissivity to herpes simplex virus replication. These parameters were found to be positive in all 6 amplification-competent cell lines. The ability of herpes simplex virus to amplify SV40 DNA sequences in transformed cells is greater than that of chemical carcinogens and can be suppressed by specific inhibitors of the herpes virus-encoded DNA polymerase.     

Spleen-cell cytotoxicity for cytomegalovirus-transformed cells. II. Inhibition by cytomegalovirus antiserum.

Serum from hamsters immunized repeatedly with cytomegalovirus (CMV) was able to block spleen-cell cytotoxicity for CMV-infected and CMV-transformed cells. Inhibition was observed regardless of whether spleen cells were obtained from hamsters sensitized to the virus or to isografts of the transformed cells (designated Cx-90-3B, T-2). Such serum did not significantly block effector cell response against transformed cells expressing herpes simplex virus or SV40-associated membrane antigens. The mechanism of blocking was investigated. It was found that the blocking activity could be adsorbed out with Cx-90-3B, T-2 cells but not by untransformed hamster embryo fibroblasts. Cx-90-3B, T-2 target cells treated with serum, and then washed, remained resistant to effector cell attack. On the other hand, if serum-treated attacker cells were washed their cytotoxic activity was not significantly impaired. These results suggest that the blocking factor in the serum is antibody-directed against cytomegalovirus-related membrane antigen. This conclusion is supported by the finding that the serum contained antibody specifically reactive with the transformed cell surface in isotopic antiglobulin tests.     

Wild type human p53 is antiproliferative in SV40-transformed hamster cells

The transformation related protein p53 has been implicated in the process of normal cell proliferation and neoplastic transformation. In this study, the influence of wild type human p53 on cell proliferation was examined. Plasmid constructs encoding the wild type human p53 and various mutant p53 cDNAs, driven by the mouse mammary tumor virus (MMTV) promoter linked to the dominant biochemical selection marker gpt, were used in a colony forming assay employing SV40 transformed HR8 hamster cells. Plasmids encoding wild type p53 drastically reduced the number of gpt+ colonies obtained after transfection, whereas the mutant forms of p53 had no effect. Stable clonal hamster cell lines that constitutively express wild type p53 were isolated and found to have altered growth characteristics (i.e. lower saturation densities, increased doubling times). These findings are consistent with the notion that wild type p53 protein could function as a growth suppressor. The potential role of p53 in the normal cell cycle and in the transformation process is discussed.     

Effect of adeno-associated virus on cancer expression by herpesvirus-transformed hamster cells.

Infection of herpes simplex virus type-2-transformed hamster tumor cells with adeno-associated virus type 1 before inoculation into hamsters specifically delayed the appearance of palpable tumors and increased the survival time of the animals. The data indicated that a defective virus of humans can influence cancer expression by a virus-transformed cell.     

Biochemical properties of media conditioned by simian virus 40-induced hamster tumor cells: correlation with distinct cell phenotypes but not with oncogenicity

Hamster cells, transformed in vitro by SV40, have been reported to secrete an unidentified factor(s) that inhibits thymidine uptake (TU) by various normal cell types, including activated lymphocytes. It has been postulated that this apparent antiproliferative effect may play an in vivo role in the high tumorigenic capacity of SV40-transformed hamster cells. In keeping with this hypothesis, Adenovirus type 2-transformed hamster cells, which are only weakly tumorigenic, do not inhibit TU by indicator cells in vitro. To study the biological relevance of this phenomenon, we assayed 11 cell lines derived from different fibrosarcomas, induced in Syrian hamsters by SV40, for their ability to inhibit TU by normal rabbit kidney indicator cells. In contrast to cells transformed in vitro by SV40, media conditioned by 6 of 11 tumor-derived cell lines did not inhibit TU. Our results do not support the hypothesis that an antiproliferative factor secreted by SV40-transformed cells promotes the tumor-inducing capacity of these cells. Furthermore, inhibition of TU does not appear to be due to the production of a specific antimitotic peptide, but rather to other biochemical properties of the media conditioned by transformed cells. Finally, these biochemical properties do appear to correlate with specific morphological and growth characteristics of the tumor cells, but probably as an effect and not a cause.