Suppression of murine type-C RNA virogenes by type-specific oncornavirus vaccines: prospects for prevention of cancer.
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Immunization of crossbred and F1 mice with combined killed and live Gross leukemia virus AKR type-C viral vaccines suppressed endogeneous N-type AKR virus up to 10,000-fold for significant periods during early life. Since several previous studies in the same and similar crossbred systems revealed direct correlations between low and high levels of type-C virus early in life with low and high incidences of leukemia and other cancers later in life, we believe that prospects for suppression of spontaneous neoplasms are good; however, 8-14 months will be required to achieve the final results. Should cancers be prevented by serotype-specific vaccines, such evidence would provide conclusive proof of endogenous viral etiology. (+info)
Characterization of the type and group specificities of the immune response in mice to murine leukemia viruses.
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Normal sera from a variety of strains of inbred mice have precipitating antibodies to murine type C viruses that are detected by radioimmune precipitation assays. The results demonostrate that this humoral immune response is primarily directed against the AKR strain of murine leukemia virus (MuLV) proteins gp71, gp43, and p15(E). These sera also react with Friend- or Rauscher-MuLV in radioimmune precipitation assays. This reaction is not due to a separate immune response, but rather is primarily a consequence of the cross-reactivity of antibodies to the AKR strain of MuLV p15(E) with the p15(E) of these viruses. These data, using autogenous immune sera, emphasize the serological differences of the virion glycoproteins and the serological similarity of the p15(E) virion component of the viruses. Furthermore, based on the serological reactivities to the glycoproteins, the results suggest that the AKR strain of MuLV is endogenous to and expressed in mice, but that the Friend-Moloney-Rauscher virus group is not. (+info)
Autologous immune responses to the major oncornavirus polypeptides in unmanipulated AKR/J mice.
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The autologous immune response of AKR/J mice to the structural proteins of murine leukemia virus (MuLV) was examined. Immunoglobulins from the renal glomeruli were chemically eluted, separated from antigens, recovered, and tested for immunological reactivity against MuLV structural proteins. Analyzing immune precipitates obtained after mixing radiolabeled Tween-disrupted MuLV preparations with eluates from AKR/J mice on sodium dodecyl sulfategel electrophoresis, we found evidence of antibodies to the major classes of MuLV structural components: gp70, gp45, p30, and one or more proteins in the 10,000- to 15,000-dalton class. Using rate zonal centrifugation we confirmed that the eluates from AKR/J glomeruli contained antibody(s) that bound specifically to p30. These results indicate that AKR/J mice spontaneously mount immune responses against the major oncornavirus polypeptide antigens. (+info)
Virion interaction in mouse lymphomas.
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Virion expression in filtrates of lymphomas in AKR/J or C3H/HeJ mice was assayed by two techniques: (a) in vitro infectivity (XC assay), or (b) acceleration of oncogenicity in vivo (O assay). The two assays appeared to detect different virus populations or activities. This was shown when the same filtrates were tested in parallel by the XC and O tests and opposite results were obtained on the two assays, e.g., XC+ 0- or XC- O+. It was postulated that two viruses, termed "XC+" and "O" to correspond to the assays used to detect them, were involved in oncogenesis. When lymphomas originally virus induced were passaged by cells in 2- to 3-month-old syngeneic AKR or C3H mice, oncogenic activity of filtrates of these transplanted lymphomas decreased as cell passages increased. These filtrates from C3H lymphomas also had decreased XC activity as cell passages increased. Normal lymphoid tissue from 1- to 5-month-old AKR mice was XC+ O-, while from C3H mice it was XC- O-. Thus, the two strains modified activities lacking in their normal tissues. Filtrates highly oncogenic in XC+ newborn AKR mice were oncogenic in C3H newborn mice only when sufficient XC+ virus was in the inoculum received by the XC- C3H mice. Thus the XC+ virus appeared to play a synergistic role with a postulated O virus in oncogenesis. (+info)
Increase of AKR-specific sequences in tumor tissues of leukemic AKR mice.
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AKR mice produce, from shortly after birth, high titers of their endogenous Gross type murine leukemia virus, and develop a thymus-derived leukemia at 7-9 months of age. We show that this oncogenesis is accompanied by an increase in the number of AKR-specific DNA sequences in the tumor tissues, whereas the "non-target" organs are not affected. Sequence increase was determined by kinetic analysis of DNA reassociation using an AKR-murine leukemia virus (MuLV)-specific cDNA and also by hybridization with excess AKR cDNA. The AKR cDNA was selected to recognize AKR sequences without significant crossreaction with DNA sequences of other endogenous viruses. The results show that during the development of the leukemia, the number of AKR-MuLV-specific genes increases in tumor tissues by a factor of 1 1/2 to 2. (+info)
Various facts are now known about the relative lymphoma resistance of a group of tetraparental AKR reversible CBA/H-T6 chimaeras derived by early embryo aggregation. Firstly, their tumour resistance is not due to the lack of the lymphomaprone AKR cells. Secondly, results showing titres of MuLV-gs antigen comparable with, and occasionally in excess of, those in the AKR suggest that the tumour resistance of the chimaeras is unlikely to be due to a lack of oncogenic leukaemia virus. However, in marked contrast to the AKR, antibody-viral antigen renal complexes in the chimaeras were minimal. Lack of viral antigens could not explain the relative lack of renal complexes. Absence of the corresponding anti-viral antibody is the most likely explanation and this has to be attributed to the CBA component of the tetraparental AKR reversible CBA/H-T6 chimaeras. We suggest that with tolerance to the leukaemia virus being maintained and in the absence of anti-viral antigenic complexes, tumour-specific sites can be recognized and thus tumours are eliminated. This hypothesis remains to be proven. (+info)
Natural immunity in mice to structural polypeptides of endogenous type C RNA viruses.
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The immunological responses of inbred mice to structural components of one class of endogenous virus were investigated by means of radioimmunoassays utilizing highly purified viral proteins. Naturally occurring antiviral antibodies were demonstrated only in those strains possessing information for induction of a mouse cell-tropic endogenous virus. Moreover, these antibodies invariably appeared subsequent to the detection of spontaneous replication of this virus in the same animal. The immune responses elicited were much stronger against endogenous viral gp70 than p30, consistent with previous findings of tolerance in the mouse to the major structural antigen of its endogenous virus. However, the demonstration of an immune response to p30 under conditions of both natural and experimental immunization establishes that tolerance to this viral antigen can be overcome. (+info)
Mouse strain resistant to N-, B-, and NB-tropic murine leukemia viruses.
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Mouse strain G was studied for its susceptibility to various strains of murine leukemia and sarcoma viruses. Both N- and NB-tropic Friend leukemia viruses neither induced splenomegaly nor grew efficiently in strain G mice. Using the XC test, cultured embryo cells were found to be resistant, but not absolutely, to all the tested viruses, N-tropic AKR virus, N- and NB-tropic Friend leukemia viruses, NB-tropic Rauscher leukemia virus, B-tropic WN1802B virus, NB-tropic Moloney leukemia and sarcoma viruses, and N-tropic Kirsten sarcoma virus, although the resistance to Moloney leukemia and sarcoma viruses is sometimes not as strong as that for other viruses. Thus, the strain G mice are unique among mouse strains because they show resistance that is not related to the N-B tropism of murine leukemia viruses. (+info)