Jeffrey J. Collins

Characterization of the immune response to the major glycoprotein (gp71) of Friend leukemia virus. II. Response in C57BL/6 mice.

Abstract C57BL/6 mice responded to immunization with purified gp71 of Friend murine leukemia virus by mounting both humoral and cell-mediated responses. As measured by a number of tests, the responses were generally stronger than those obtained in BALB/c mice. However, in contrast to the BALB/c mice, immunization of C57BL/6 mice with gp71 did not result in the development of cytotoxic lymphocytes, although spleen lymphocytes were capable of undergoing blastogenesis when incubated with purified gp71. As in the BALB/c mice, the humoral response was type-specific. A unique feature of the response in gp71-immunized C57BL/6 mice was the accelerated activation of the endogenous virus as measured by the development of an immune response to its distinct envelope antigens. This resulted in the production of three distinguishable antibody populations: (1) type-specific antibodies to FLV gp71; (2) type-specific antibodies reacting with AKR gp71 (AKR virus being related to the endogenous virus of C57BL/6 mice); and (3) antibodies directed against p15 (E) which reacted both with AKR and Friend-Moloney-Rauscher viruses and are therefore considered group-specific in the murine system. The possible significance of the activation of the endogenous virus subsequent to gp71 immunization of C57BL/6 mice is discussed.

Characterization of the immune response to the major glycoprotein (gp71) of Friend leukemia virus. III. Influence on endogenous MuLV-mediated pathogenesis.

The response of AKR mice to immunization with purified gp71 of Friend murine leukemia virus (FLV)9 was characterized. A humoral response was detectable by radioimmune precipitation assay with FLV or radioimmunoassay with FLV gp71. In contrast, no reactivity with either the endogenous AKR virus or AKR gp71 was detectable. The humoral immune response to FLV gp71 was also detectable in complement-dependent cytotoxicity assays and again appeared type-specific for FLV-producing cell lines and could be specifically blocked by absorption with FLV gp71. In contrast, no specific neutralization of FLV was detectable with immune sera. Cell-mediated reactivity was examined by blastogenesis assays with FLV gp71 and in vitro cytotoxicity assays. Although no consistent cell-mediated cytotoxicity was demonstrable in vitro, speen cells from FLV gp71-immunized mice did undergo blastogensis when incubated with purified gp71. The ability of FLV gp71 immunization to protect AKR mice from spontaneous thymomas and irradiated C57B1/6 mice from radiation-induced thymomas was also examined. The results demonstrate that FLV gp71 immunization has no clear influence on induction of radiation thymomas in C57Bl/6 mice. In contrast, FLV gp71 immunization greatly increased the rate of mortality of AKR mice from thymic lymphomas without altering the time of onset of disease-related deaths. The possible mechanisms behind this enhancement of thymomas by FLV gp71 immunization, including the activation of the endogenous AKR virus, are considered.

Normal chicken cells (chf−) express a surface antigen which cross-reacts with determinants of the major envelope glycoprotein (gp85) of avian myeloblastosis virus☆

Abstract Using rabbit antisera raised against the purified major envelope glycoprotein (gp85) of avian myeloblastosis virus (AMV), we were unable to differentiate between normal chicken cells carrying the chicken-helper factor (chf+) from those lacking this endogenous virus information (chf−) in several serological assays, including competition radioimmunoassay and membrane immunofluorescence. Radioimmunoprecipitation analysis of the material recognized in uninfected chf(+) and chf(-) chicken cells by the rabbit anti-AMV gp85 antisera revealed the presence in immune precipitates of both cell types of a high molecular weight glycoprotein (∼125,000), while low amounts of gp85 were precipitated only from the chf(+) cells. In contrast, antisera raised against the gp85s of three other avian oncornaviruses did not recognize the 125,000-dalton molecule in either cell type, although gp85 was again precipitated from the chf(+) chicken cells. The high molecular weight glycoprotein (denoted NCG) appears to represent a normal chicken cell surface glycoprotein which is antigenically cross-reactive with unique determinants of AMV gp85, presumably dependent on the carbohydrate portion of the molecules. The significance of this cross-reactivity is discussed, as well as the interpretation of previous results obtained through the use of these rabbit anti-AMV gp85 antisera.

ALLOGENEIC REACTIVITY IN NORMAL MOUSE SERUM

Normal C57BL/6 (B6) mouse serum was tested in the direct cytotoxicity assay for specific reactivity against lipopolysaccharide (LPS)‐stimulated mouse spleen cells. Selective reactivity was found in weanling and adult serum against lymphoblasts from mice that express an antigen encoded by the H‐2Kk region of the major histocompatibility complex (MHC). Other strains, congenic with B6 at the MHC, did not exhibit the same alloreactivity. Serum from mice of a congenic strain being derived in our laboratory, which differs from B6 at two unlinked loci, Tla and nu, exhibited similar reactivity against the B6‐H‐2k LPS‐stimulated lymphoblasts, implying that a competent T cell compartment is not necessary for generation of this reactivity. Such reactivities may result from environmental stimulation of the immune system, from internal immuno‐regulatory controls, or from some combination of these immune stimuli

IMMUNOTHERAPY OF MURINE LEUKEMIA VI. DEVELOPMENT OF IMMUNOLOGIC MEMORY IN MICE PROTECTED AGAINST FRIEND LEUKEMIA VIRUS-INDUCED DISEASE BY PASSIVE SERUM THERAPY

The resistance of DBA/2 mice to infection with a leukemogenic dose of Friend leukemia virus (FLV) as a result of the passive administration of chimpanzee anti-FLV serum is maintained for at least six months after infection and is accompanied by the continued synthesis of mouse anti-viral antibodies analogous to that previously found to be associated with short-term protection (approx. 30 days). Furthermore, the induction of immunologic memory in serum-protected mice is demonstrated by their long-term resistance to rechallenge with FLV of FLV-infected leukemic spleen cells, although cells of an established transplantable syngeneic FLV-erythroleukemia (FLC-745) are not rejected. In the course of these studies, a serum prophylaxis effect was defined in DBA/2 mice treated with the chimpanzee anti-FLV serum before, rather than after FLV infection. The prophylaxis effect is highly dependent on the time period between the last serum inoculation and virus challenge. The results indicate that the long-term resistance of therapeutically protected mice to subsequent virus or leukemic cell challenge is not due to the short-term prophylactic effect of serum treatment alone.