V. M. Larson

Interruption of SV40 Virus Tumorigenesis Using Irradiated Homologous Tumor Antigen.

Summary X-irradiated SV40 transplant tumor or cell culture antigens were highly effective in preventing occurrence of homologous tumor in hamsters inoculated with SV40 virus when newborn. The X-irradiated immunizing tumor antigen was effective when given in a single dose as early as 34 days or as late as 76 days after SV40 virus was administered. The immunizing antigen was retained in tumor transplants in hamster for at least 20 passages and in cell culture of tumor for at least 38 passages. The significance of the findings in relation to protection against the hypothetical virus-induced tumor in man is discussed.

Studies of Oncogenicity of Adenovirus Type 7 Viruses in Hamsters.

Summary All of 3 strains of type 7 ade-novirus isolated in primary human embryonic kidney cell cultures from respiratory secretions of human subjects with acute respiratory illness proved oncogenic for newborn hamsters. The type 7 viruses were isolated and propagated in human embryonic cell cultures and were free of extraneous agents. Detailed information relative to the virology, oncology, pathology and immunology of the type 7 adenovirus-hamster tumor system is presented. The tumors appeared after a long latent period, were highly malignant, were readily transplantable and were free of detectable infectious virus. The cells in most of the tumors were sufficiently differentiated to permit a pathologic diagnosis of malignant lymphoma, or lymphosarcoma when evidence of invasiveness was present. A majority of tumors induced by the virus presented a specific complement-fixing antigen which reacted with sera from hamsters bearing homologous tumor. The authors are indebted to T. Beddow, W. Clark, P. Gosnell, B. Keech and W. Raupp for technical assistance.

Influence of synthetic double-stranded ribonucleic acid, poly i,c, on friend leukemia in mice.

Summary Studies were carried out to measure the effect on Friend leukemia in BALB/c mice of synthetic double-stranded RNA, Poly I:C (rI:rC), given in different prophylactic and therapeutic regimens. The effect of Poly I:C was strongly influenced by the time of initiating treatment, the amount of drug given, and the number and frequency of doses administered. Necrosis and hemorrhage of the spleen were among the principal pathologic effects of Friend leukemia in mice and these were markedly reduced in those instances in which drug treatment decreased splenomegaly. When administered prior to virus, cortisone greatly increased splenomegaly in Friend leukemia both alone and in combination with Poly I:C. The effect of Poly I:C administration before virus was strongly dose-related and a significant beneficial effect was obtained when the amount of drug was reduced to 4 μg. In toto, Poly I:C was not strikingly beneficial in altering the events in experimental Friend leukemia. The complex and multifaceted relationships between virus and drug and their administration will require detailed examination before an optimal prophylactic or therapeutic regimen can be derived.

Influence of synthetic (poly I:C) and viral double-stranded ribonucleic acids on adenovirus 12 oncogenesis in hamsters.

Summary Synthetic double-stranded ribonucleic acid (Poly I:C) and replicative form RNA from MU9 coliphage reduced the occurrence of internal but not subcutaneous tumor after injection of adenovirus 12 subcutaneously into newborn hamsters. The effect was more evident in female than in male animals. Poly I:C treatment was consistently effective only when started prior to virus. The single homopolymers Poly I and Poly C were also protective even though they exert little, if any, interferon-inducing capacity. The action of the ribonucleotides might have been related both to interferon and to ordinary immune mechanisms. The greater activity in females as compared with male animals and the fact that the single-stranded Poly I and Poly C homopolymers were active favors the latter possibility. Pyran copolymer and endotoxin showed a minor reduction in internal but not subcutaneous tumor when given prior to and after adenovirus.

Influence of synthetic double-stranded ribonucleic acid (poly I:C) on SV40 viral oncogenesis and transplant tumor in hamsters.

Summary Studies were carried out to measure the effect of a synthetic double-stranded RNA, poly I:C, on SV40 transplant tumor growth and SV40 viral oncogenesis in hamsters. Single or multiple doses of poly I:C given intraperitoneally before and/or after subcutaneous inoculation of SV40 virus into newborn hamsters had little or no effect on the percentage of animals developing subcutaneous tumors later in life. Likewise, single or multiple doses of varying amounts of poly I:C administered intraperitoneally before and /or after subcutaneous inoculation of 1000 to 500,000 virus-free SV40 tumor cells had little or no effect on the rate of tumor appearance in adult male hamsters. The authors are indebted to W. R. Clark, W. S. Collom, and T. A. Napier for technical assistance. Statistical computations were done by A. McLean.

Prevention of SV40 Virus Tumorigenesis by Irradiated, Disrupted and Iododeoxyuridine Treated Tumor Cell Antigens.

Summary Hamster SV40 tumor cells rendered nonproliferative by exposure to gamma rays or by propagation in the presence of iododeoxyuridine were highly effective when used as immunizing antigens for preventing the appearance of tumors in hamsters which had received SV40 virus when newborn. Only a single injection of immunizing antigen was employed. Disruption of tumor cell preparations by freeze-thaw or by treatment in a French pressure cell for purpose of fractionation resulted in total or near total loss of immunizing capability, even when incorporated into alum adjuvant. Possible mechanisms for loss of potency are discussed. Addendum: Since the time the present manuscript was in press, it was found in further experiments employing the same techniques that the loss of RNA and protein following cell disruption was considerably less than noted above.

Further Tests in Hamsters for Oncogenic Quality of Ordinary Viruses and Mycoplasma, with Correlative Review.

Summary Previous and present findings demonstrated the failure of tumor induction in newborn hamsters by adenovirus 1, 2, 3 (tentative), 4, 5, and 6 (tentative), vaccinia, herpes simplex, varicella, cytomegalo-virus, reovirus 1 (tentative), poliovirus 1 and 3, ECHO 25, Coxsackie A10 and A21, rhino virus 11, 23 and 30, encephalo-myocarditis, chikungunya, Hawaiian dengue, Marituba, Sicilian sandfly, influenza A2, parainfluenza 1, 2 and 3, respiratory syn-cytial, mumps, measles (virulent and attenuated), rubella, rabies, visceral lymphomatosis (including RPL-12 and RIF agent), pneumonia virus of mice and lymphocytic chorio-meningitis viruses and two Mycoplasma species including Eaton agent. Adenovirus 7 was moderately and adenovirus 12 and 18 were highly oncogenic. Tumors occurred in 2 animals which Received Bryan strain Rous sarcoma. The findings are discussed in relation to the familial, biophysical, biochemical and structural properties of the viruses studied and with respect to the evidences which suggest a possible role of virus in human neo-plasia. The authors are indebted to W. Raupp, T. Bed-dow, R. Grady and W. Clark for valuable technical assistance.

Immunologic Responses in Hamsters to Homologous Tumor Antigens Measured in vivo and in vitro

Summary Cell mediated immunity against homologous SV40 tumor cells was demonstrable in the homologous in vivo hamster system but not in cell culture. The effectiveness of exudate cells from immunized hamsters was clearly influenced by the ratio of target cells to immune cells and by the age of test hamsters used with protective effect demonstrable in adult but not in 1 week-old hamsters. High levels of immunity against homologous tumor were also demonstrable by direct subcutaneous challenge. The latter system was desirable for assay of vaccine potency because of simplicity and rapidity of obtaining results. The authors are indebted to W. Clark and E. Glenn for technical assistance. The irradiation was carried out at Albert Einstein Medical Center, Philadelphia, through the courtesy of Dr. Jacob Gershon-Cohen with the kind assistance of Dr. David Sklaroff.

Prevention of Viral and Transplant Tumors in Hamsters Employing Killed and Fragmented Homologous Tumor Cell Vaccines

Summary Studies were continued in SV40 and adenovirus 7 hamster tumor systems to develop means for isolating tumor-specific transplant antigen, essentially free of normal tissue antigens, preparatory to consideration for vaccination experiments employing autochthonous tumor vaccines in man. Consistent with previous experiments, SV40 virus-induced tumor cells lost their immunizing ability for the host when treated with formalin or disrupted by a French pressure cell or nitrogen decompression. By contrast, adenovirus 7 tumor cells treated with formalin or disrupted by freeze-thaw, by use of a French pressure cell, or by nitrogen decompression retained the ability to immunize against the same cell tumor challenge. The latter findings are regarded as a significant step toward eventual development of tumor cell vaccines employing fractionated and purified antigens.

Complement-fixation reaction of human neoplastic tissue with sera from hamsters bearing virus-induced tumors.

Summary A total of 123 extracts of tissues from 111 cases of human cancer of diverse type and 22 extracts of tissues from 20 cases of non-neoplastic disease of man were examined for presence of antigens fixing complement with sera from hamsters bearing adenovirus 7, 12 and 18, SV40, or Rous sarcoma tumor. Thirteen tissues from cases of cancer and 4 tissues from non-neoplastic disease gave positive CF reactions with adenovirus type 12 and sometimes with type 7 tumor antisera but not with the other tumor antisera. Interpretation was complicated in some instances by apparent isoantigen-anti-body reactions between human and hamster tissues. No evidence for etiologic role of adenovirus 18, SV40 or Rous sarcoma virus in human tumor was obtained and if a virus related to 7 and 12 plays a role in human neoplasia, it would appear to be relatively infrequent. Without substantial improvement in specificity and sensitivity, tests for T antigen in human neoplastic tissues would not appear worthy of further emphasis.