The specificity of H‐2‐restricted cytotoxic T lymphocytes directed to AKR/Gross leukemia virus‐induced tumors II. Altered gp70 display and production of noninfectious virus particles by an insusceptible variant tumor

Abstract

Derived from the susceptible AKR.H-2bSL1 tumor cell line, a variant tumor subclone, cl.18-5, was selectively insusceptible to H-2-restricted anti-AKR/Gross virus cytotoxic T lymphocytes (CTL) due to its failure to be recognized. In this study, the expression of virus-related products by variant cl.18-5 cells was compared to that of AKR.H-2bSL1 cells and a susceptible clone, as an approach towards defining the virus-associated antigens recognized by anti-AKR/Gross virus CTL. Despite the type specificity of the CTL, cl.18-5 displayed normal levels of the group-specific antigen (gag) encoded proteins p30, p15, p12 and p10, and the gag-associated Gross cell surface antigen. These results were confirmed by fluorescence-activated cell sorter analysis employing monoclonal antibodies specific for either AKR p12 or the cell surface glycosylated form of AKR ecotropic gag product. In contrast, cl.18-5 was variably less sensitive than AKR.H-2bSL1 to the action of complement and xenogeneic antisera directed against the envelope (env) product gp70. In addition, a panel of five monoclonal antibodies to gp70, which detect distinct endogenous ecotropic viral determinants, lysed AKR.H-2bSL1, but not cl.18-5 cells. However, absorption experiments indicated that cl.18-5 did express near normal levels of these specificities, suggesting an alteration in the orientation or topographical distribution of these determinants. Consistent with an inappropriate display of env products, cl.18-5 was found to be deficient in the production of infectious ecotropic leukemia virus. The particulate fraction of the cell-free supernatant of cl.18-5 contained normal levels of reverse transcriptase activity, indicating that noninfectious viral particles were being produced. Collectively, these results point to an association between recognition by anti-AKR/Gross virus CTL and the expression of ecotropic gp70 required for infectivity of virus.

Evidence for H-2-linked control of retrovirus production in Friend virus-induced tumor cell lines

“…There are several ways in which altered expression of the exogenous retrovirus by the host cell could potentially affect processes which are thought to be involved in leukemogenesis. (i) Immune responses have been shown to be affected by the presence of virus particles (6, 47) and by alteration of viral proteins on the cell surface (25). Viral protein alterations have been observed in all nonproducer tumor cell lines examined (Fig.…”

Primary virus-induced lymphomas evade T cell immunity by failure to express viral antigens.

“…Other reports of MuLV induced tumors, which lack viral antigen expression, indicate various immunorelevant target molecules (20,(52)(53)(54) . It should be stressed that our observations concerning viral antigen and MHC expression on lymphomas were made on fresh or cryopreserved viable cell suspensions from primary lymphomas that arose in vivo in nonmanipulated animals.…”

“…It should be stressed that our observations concerning viral antigen and MHC expression on lymphomas were made on fresh or cryopreserved viable cell suspensions from primary lymphomas that arose in vivo in nonmanipulated animals. The few previous observations ofabsent viral antigen expression on retrovirus-induced lymphomas were made with in vitro tumor lines (52)(53)(54), or after artificial immunoselective pressure (20) . Green and Manjunath and colleagues (52,53) described two variant subclones of a tumor cell line, derived from an AKR virus-induced lymphoma in AKR (H-2k) mice, that were resistant to lysis by virus-specific Tc.…”

“…The few previous observations ofabsent viral antigen expression on retrovirus-induced lymphomas were made with in vitro tumor lines (52)(53)(54), or after artificial immunoselective pressure (20) . Green and Manjunath and colleagues (52,53) described two variant subclones of a tumor cell line, derived from an AKR virus-induced lymphoma in AKR (H-2k) mice, that were resistant to lysis by virus-specific Tc. These variants showed strongly reduced gp70 ena viral antigen expression as detected by the gp70-specific mAb panel, also used here.…”

Differential induction of H-2K versus H-2D class I major histocompatibility antigens by recombinant gamma interferon. Lack of Kk augmentation in a leukemia virus-induced tumor is due to a cis-dominant effect.

“…We have been interested in the interaction of specific antiviral CTL with tumors induced by AKR/Gross murine leukemia viruses (MuLV)' with respect to the recognition of both viral antigens and the H-2K class I-restricting element used in this system (1)(2)(3)(4). Recently, we identified two MuLV+ tumors of the high leukemia incidence H-2k haplotype that showed an unusual phenotype with regard to class I expression after IFN-y treatment.…”