Retrovirus-induced lymphoproliferation as a model for developing diagnostic criteria for malignant lymphoma in mice

Several methods for evaluating lymphoproliferative lesions in mice were compared. The model systems included spontaneous lymphomas arising in CWD mice and NFS mice congenic for ecotropic murine leukemia virus (MuLV) induction loci and a series of transplants in mice with severe combined immunodeficiency disease mutation of cells derived from mice infected with LP-BM5 MuLV. Primary lymphomas and donor tissues and transplants were examined using histopathology, flow cytometry, and Southern blot analysis of DNA for rearrangements of immunoglobulin and T-cell receptor genes and for viral integrations. The use of flow cytometric analysis, to establish cell lineage and define population size, and DNA analysis, for cell lineage and clonality determination, allowed the identification of malignant lymphoproliferations. Histologic evaluation did not define clonal populations of particular lineage but did provide other indications of malignancy such as invasiveness and presence of a dominant morphologic cell type. Thus, the precision of diagnosis of mouse lymphomas can be considerably enhanced by augmenting histopathologic examination with antigenic and molecular characterizations that can define malignant populations.

Early divergence of erythroid lineage suggested by gene rearrangements in mouse hematopoietic neoplasms

A total of 113 primary murine hematopoietic neoplasms, including those of erythroid, granulocytic, and T and B lymphoid lineages, were examined for rearrangement of immunoglobulin heavy (IgH) and kappa light chain (IgK) and T cell receptor beta and gamma (TcR-beta and TcR-gamma) genes. There was a total absence of Ig or TcR gene rearrangements in erythroid leukemias. In contrast, overlaps of IgH rearrangements were observed in myeloid and T cell as well as B cell neoplasms. In a minority of B cell lymphomas, rearrangements of TcR-beta or TcR-gamma genes were detected. This evidence of shared recombinase activity for myeloid, T cell, and B cell-lineage tumors and the absence of such activity in erythroid tumors suggest early divergence of the erythroid pathway.

Thrombocytopenia in a retrovirally-induced murine erythroleukemia

A variant strain of Rauscher leukemia virus (RLV-A) obtained from a transplantable murine monomyelocytic leukemia causes a disease characterized by frank anemia, wasting, hepatosplenomegaly and erythroblastosis. The involvement of platelets in this disease are reported here. The RLV-A induced a severe thrombocytopenia (25 percent of control level) at the terminal stage of disease. This thrombocytopenia was not associated with disseminated intravascular coagulopathy since the prothrombin times were always within normal limits. The partial thromboplastin time was elevated in the terminal stages of disease and was found to be associated with factor deficiencies, possibly owing to the presence of anti-factor antibodies, in the intrinsic coagulation pathway, especially factor VIII. Further, splenectomy did not abolish the thrombocytopenia, since splenectomized, virally infected animals also developed severe thrombocytopenia (29 percent of control levels). The ensuing splenomegaly during progression of disease was not the cause of the thrombocytopenia. A physiological response to the severe thrombocytopenia was the production of larger size platelets. At terminal stages of the disease, platelet volume increased to 4.2 mu 3 (normal is 3.0 mu 3). An increase in platelet volume was also observed in splenectomized, virally infected animals. Electron microscopy indicated that these circulating platelets contained c-type viral particles. Viral infection was associated with decreased life span of circulating platelets, as measured by 75Se-methionine at mid and terminal stages of the disease. Our results suggest that direct viral infection of platelets and/or megakaryocytes with subsequent cell lysis is a possible cause of the observed thrombocytopenia observed in RLVA-induced disease and may also occur in other retrovirally-induced diseases.

Opportunistic infections and retrovirus-induced immunodeficiency: studies of acute and chronic infections with Toxoplasma gondii in mice infected with LP-BM5 murine leukemia viruses

Mice infected with LP-BM5 murine leukemia viruses develop a syndrome, termed mouse AIDS (MAIDS), characterized by increasingly severe immunodeficiency and progressive lymphoproliferation. Virus-infected mice were examined for the ability to resist acute infection and to control chronic infection with the protozoan Toxoplasma gondii, a major opportunistic pathogen of individuals infected with human immunodeficiency virus. Mice infected with the retroviruses for 2 or 4 weeks responded normally to challenge with the parasite, but mice inoculated with the protozoan 8 or 12 weeks after viral infection died with acute disease due to T. gondii. Increased sensitivity to acute infection was associated with a reduced ability to produce gamma interferon (IFN-gamma) and with established changes in CD4+ T-cell function. Mice latently infected with T. gondii and then inoculated with the retrovirus mixture were found to reactivate the parasite infection, with 30 to 40% of dually infected animals dying between 5 and 16 weeks after viral infection. Reactivation was associated with reduced proliferation and impaired production of IFN-gamma in response to stimulation with soluble T. gondii antigens or to concanavalin A. Continuing resistance to lethal reactivation in the remaining mice was shown to require CD8+ T cells and expression of IFN-gamma. In addition, it was found that chronic infection with T. gondii altered the course of MAIDS by inhibiting the progression of splenomegaly and immunodeficiency and reducing the expression of both the helper and etiologic defective viruses. These results support previous studies which indicate that infection with T. gondii is controlled by synergistic interactions between CD4+ and CD8+ T cells, the functions of which are progressively impaired during the course of MAIDS.

Acute inflammatory response to cowpox virus infection of the chorioallantoic membrane of the chick embryo

The chick embryo chorioallantoic membrane was used to study the acute inflammatory response in the absence of contributions from the immune system. In preliminary experiments, lesions of wild-type cowpox virus strain Brighton (CPV-BR) and a 38K gene deletion mutant of CPV-BR (CPV-BR.D1) were compared with vaccinia virus (strains WR and Copenhagen), fowlpox virus, laryngotracheitis virus, and infectious tenosynovitis virus, and were ranked for degree of induced inflammation. The maximal and minimal inflammatory responses were observed with CPV-BR.D1 and CPV-BR viruses, respectively. CPV-BR.D1 lacks a 38K gene which encodes an anti-inflammatory 38-kDa protein that has homology to SERPINs. The kinetics and character of the inflammatory response were examined further in the wild-type CPV-BR and mutant CPV-BR.D1 infections using cell counts, electron microscopy, and assays for inflammatory cell activation. CPV-BR virus infection rapidly spread through the ectoderm, uniformly infecting all cells with the production of large amounts of virions and viral-induced cytopathic effect, but evoking little or no inflammatory response until 144 hr p.i. The CPV-BR.D1 infection, on the other hand, was rapidly contained by a dexamethasone-sensitive inflammatory response mainly of activated heterophils which was advanced by 36 hr p.i. Both infections resulted in disseminated disease with similar numbers of liver lesions and only a slight difference in the LD50, with the CPV-BR.D1 values being higher than that for CPV-BR virus. In this model, the acute inflammatory response alone is unable to prevent disseminated disease and associated mortality.

Effect of 3'azidothymidine administered in drinking water or by continuous infusion on the development of MAIDS

LP-BM5 MuLV infection of C57BL/6 mice induces a well characterized, lymphoproliferative, immunodeficiency disease (MAIDS), which is useful for evaluation of potential antiviral agents, because of the reproducibility of virological and clinical endpoints. This MAIDS retrovirus model was used to evaluate 3'azido-2,3'dideoxythymidine (AZT), using different doses, methods of administration and timing for initiation and continuation of therapy. AZT therapy 1 mg/ml in the drinking water given 30 days prior to virus challenge, and continued for 16 weeks, prevented LP-BM5 MuLV dissemination and disease in 13 of 15 treated mice. Efficacy was dose dependent for AZT concentrations of 1, 0.5, and 0.1 mg/ml in drinking water. One mg/ml AZT was most effective in preventing infection if therapy was begun within days prior to virus challenge or within the first four hours after virus inoculation. If treatment was initiated later, disease was delayed. Continuous infusion of AZT, 25 micrograms/h, was effective since virus was not detected in spleens of any mice during the 21 days of AZT treatment. However, after treatment was stopped treated mice became virus positive and disease progressed. Likewise, AZT administration at 1 mg/ml in the drinking water for only 21 days post virus inoculation (p.i.), was not sufficient to prevent virus dissemination or disease.

Characteristics and contributions of defective, ecotropic, and mink cell focus-inducing viruses involved in a retrovirus-induced immunodeficiency syndrome of mice

LP-BM5 murine leukemia virus, a derivative of Duplan-Laterjet virus, contains a mixture of replication-competent B-tropic ecotropic and mink cell focus-inducing (MCF) viruses and a defective genome that is the proximal cause of a syndrome, murine AIDS (MAIDS), characterized by lymphoproliferation and immunodeficiency. The defective (BM5d) and ecotropic components of this mixture were molecularly cloned, and complete (BM5d) or partial (ecotropic) nucleotide sequences were determined. BM5d closely resembled the Du5H genome cloned from the Duplan virus, featuring a highly divergent p12 sequence in the gag open reading frame. In MAIDS-sensitive C57BL/6 mice, BM5d was detected in tissues within 2 weeks of infection but was absent from tissues of the MAIDS-resistant strain, A/J, 12 weeks after infection. B-cell-lineage tumors from mice with MAIDS contained and expressed BM5d, and clonal integrations of this genome were variably associated with clonal expansions of B cells in infected mice. Finally, mRNA crosshybridizing with a probe for BM5d was present in spleen but not kidney cells of uninfected B6 mice.

Effects of non-MHC loci on resistance to retrovirus-induced immunodeficiency in mice

Mice of certain strains are highly sensitive to development of a severe immunodeficiency disease following inoculation as adults with LP-BM5 murine leukemia viruses (MuLV) whereas others are extremely resistant. These strain-dependent differences in response to infection have been shown to be genetically determined with resistance to disease being, in general, associated with homozygosity for Fv-1n and H-2 haplotypes a and d and sensitivity with homozygosity for Fv-1b and other H-2 haplotypes including b, s, and q. The Fv-1b, H-2r strain RIIIS/J (RIIIS) was found to be highly resistant to disease even though B10.RIII(71NS)/J (B10.RIII), also H-2r, was very sensitive, thus excluding a role for H-2 in the resistance of RIIIS. The characteristics of RIIIS resistance were evaluated in studies of infected (B10.RIII x RIIIS) F1, F2 and reciprocal backcross mice. Resistance to disease was shown to be semidominant and determined by more than one gene, although a preponderant influence of a single gene was suggested. Studies of segregating populations showed that resistance was not associated with or linked to polymorphisms of the V beta complex or genes in proximity to the Emv-2 locus on chromosome 8. However, there was almost complete concordance between absence of disease in infected mice and inhibition of ecotropic virus spread. These results demonstrate that genes other than Fv-1 or H-2 can profoundly influence the development of retrovirus-induced immunodeficiency and replication of ecotropic viruses.

H-2-associated and background genes influence the development of a murine retrovirus-induced immunodeficiency syndrome

Host genetic determinants of resistance or susceptibility to a retrovirus-induced immunodeficiency syndrome, termed MAIDS, were evaluated in Fv-1b mice infected with the mixture of ecotropic, MCF, and defective murine leukemia viruses designated LP-BM5 murine leukemia viruses. Genes of the MHC were shown to exert a major influence on the development of disease and the extent of virus spread in mice infected as adults. Strains bearing the b, f, k, q, r, and s haplotypes were moderately to highly susceptible to MAIDS whereas mice of the d haplotype were the most resistant. Resistance to disease was strongly associated with inhibition of mink cell focus-inducing virus spread and, to a lesser extent, with inhibition of ecotropic virus expression. Mapping studies localizing resistance associated with the d haplotype to H-2Dd were confirmed by the demonstration that B6 mice carrying this gene as a transgene or by recombination were resistant to disease. Penetrance of resistance to disease associated with expression of H-2Dd was markedly influenced by MHC genes mapping to the left of H-2D and by non-MHC loci such that some strains bearing this gene were highly susceptible to MAIDS. The combined effects of MHC and background genes among 40 strains examined yielded a remarkably wide spectrum of disease phenotypes with the onset of advanced disease ranging from 10 wk to 72 wk postinfection. Resistance to disease in moderately to highly resistant strains was shown to develop with age. Unexpectedly, the disease resistant phenotype was found to be a recessive trait.

H-2-associated and background genes influence the development of a murine retrovirus-induced immunodeficiency syndrome

Host genetic determinants of resistance or susceptibility to a retrovirus-induced immunodeficiency syndrome, termed MAIDS, were evaluated in Fv-1b mice infected with the mixture of ecotropic, MCF, and defective murine leukemia viruses designated LP-BM5 murine leukemia viruses. Genes of the MHC were shown to exert a major influence on the development of disease and the extent of virus spread in mice infected as adults. Strains bearing the b, f, k, q, r, and s haplotypes were moderately to highly susceptible to MAIDS whereas mice of the d haplotype were the most resistant. Resistance to disease was strongly associated with inhibition of mink cell focus-inducing virus spread and, to a lesser extent, with inhibition of ecotropic virus expression. Mapping studies localizing resistance associated with the d haplotype to H-2Dd were confirmed by the demonstration that B6 mice carrying this gene as a transgene or by recombination were resistant to disease. Penetrance of resistance to disease associated with expression of H-2Dd was markedly influenced by MHC genes mapping to the left of H-2D and by non-MHC loci such that some strains bearing this gene were highly susceptible to MAIDS. The combined effects of MHC and background genes among 40 strains examined yielded a remarkably wide spectrum of disease phenotypes with the onset of advanced disease ranging from 10 wk to 72 wk postinfection. Resistance to disease in moderately to highly resistant strains was shown to develop with age. Unexpectedly, the disease resistant phenotype was found to be a recessive trait.

Mutation of the core or adjacent LVb elements of the Moloney murine leukemia virus enhancer alters disease specificity

Transcriptional enhancers of replication-competent mouse C-type retroviruses are potent determinants of the distinct disease-inducing phenotypes of different viral isolates and can also strongly influence the incidence and latent period of disease induction. To study the contribution of individual protein-binding sites to viral pathogenicity, we introduced mutations into each of the known nuclear factor-binding sites in the enhancer region of the Moloney murine leukemia virus and injected viruses with these mutations into newborn NFS mice. All viruses induced disease. Viruses with mutations in both copies of the leukemia virus factor a (LVa) site, leukemia virus factor c (LVc) site, or in just the promoter proximal copy of the glucocorticoid response element (GRE) had a latent period of disease onset and disease specificity indistinguishable from that of the wild-type Moloney virus. Viruses with mutations in two or three of the GREs, in both copies of the leukemia virus factor b (LVb) site, in two of the four nuclear factor 1 (NF1) consensus motifs, or in both copies of the conserved viral core element showed a significant delay in latent period of disease induction. Strikingly, viruses with mutations in the core element induced primarily erythroleukemias, and mutations in the LVb site also resulted in a significant incidence of erythroleukemias. These and other genetic and biochemical studies suggest models for how subtle alterations in the highly conserved structure of mouse C-type retrovirus enhancers can produce a dramatic effect on disease specificity.

Inhibition of an inflammatory response is mediated by a 38-kDa protein of cowpox virus

The Brighton Red (BR) strain of cowpox virus induces a flat, bright red pock on the chorioallantoic membrane (CAM) of the 12-day-old chick embryo. In contrast, mutants with a deleted 38K gene (which is located 31 to 32 kb from the right-hand end of the virus genome) induced a raised, white, and opaque pock. During the first 24-hr p.i., both CPV-BR and the 38K deletion mutants replicated similarly in the CAM of the chick embryo, as indicated by immunocytochemical detection of similar amounts of virus antigen. By 48 hr p.i., the pocks induced by the mutant and CPV-BR are strikingly different. The pocks induced by the 38K deletion mutants were infiltrated by large numbers of heterophils and macrophages, which correlated with a reduction in the levels of virus antigen and virus infectivity. The CPV-BR pock had an absence of inflammatory cells and increased levels of virus antigen and infectivity. By 72 hr p.i., many of the pocks induced by the mutant were undergoing resolution of the virus infection, as indicated by further decrease of virus antigen and visible signs of healing, whereas CPV-BR pocks continued to be a site of active viral replication. These data are consistent with a model where this 38-kDa protein directly or indirectly inhibits the generation of chemotactic molecules which are elicited during virus replication in the CAM or, alternatively, blocks the interaction of these molecules with cells of the host inflammatory response.

Susceptibility to raf and raf/myc retroviruses is governed by different genetic loci

The susceptibility to tumors induced by raf and raf/myc retroviruses was investigated in BALB/c, C57BL/6, (BALB/c x C57BL/6)F1 and (BALB/c x C57BL/6) backcross mice. Newborn mice were susceptible to neoplasms generated by both viruses, but resistance to raf-induced leukemia developed rapidly in all mice as they matured. Older C57BL/6 mice were also resistant to raf/myc lymphomas, whereas BALB/c mice remained susceptible to the virus at all ages, indicating that different genes control susceptibility to raf and raf/myc tumors. From these data and the susceptibility of C x B recombinant inbred strains, it appears that very few genes (perhaps even a single gene) may govern susceptibility to raf/myc lymphomas and that resistance is the dominant trait.

Retrovirus-induced murine acquired immunodeficiency syndrome: natural history of infection and differing susceptibility of inbred mouse strains

C57BL mice (Fv-1b) develop a severe immunodeficiency disease following inoculation as adults with LP-BM5 murine leukemia virus (MuLV), a derivative of Duplan-Laterjet virus which contains B-tropic ecotropic and mink cell focus-inducing MuLVs and a putative defective genome which may be the proximal cause of disease. The stages of development of this disease were defined for C57BL mice on the basis of lymphadenopathy and splenomegaly; histopathological changes consistent with B-cell activation; and alterations in expression of cell surface antigens affected by proliferation of T cells, B cells, and macrophages. By using this disease profile as a standard, the response of adult mice of various inbred strains and selected F1 hybrids was compared. We show that although the strains which are highly sensitive are of the Fv-1b genotype (i.e., permissive for B-tropic MuLVs), certain Fv-1b strains, e.g., BALB/c and A/J, are resistant to murine acquired immunodeficiency syndrome, whereas certain Fv-1n strains (permissive for N-tropic MuLVs but restrictive for B-tropic MuLVs), notably P/N, BDP, and AKR, show moderate sensitivity and (C57BL/6 x CBA/N)F1 mice (Fv-1n/b and thus dually restrictive) are of relatively high susceptibility. The results of virus recovery tests suggest that apparently anomalous sensitivity, based on predicted Fv-1 restriction, may reflect MuLV induction and/or mutation to provide a helper virus for which the host is permissive.

Distinct segments within the enhancer region collaborate to specify the type of leukemia induced by nondefective Friend and Moloney viruses

The nondefective Moloney and Friend murine leukemia viruses induce T-cell lymphomas and erythroleukemias, respectively, after being injected into newborn NFS mice. In previous studies, we showed that the distinct disease specificities of the two viruses could be switched by exchanging a small segment, about 200 nucleotides in length, encompassing their enhancer regions. This segment included the direct repeat sequence and an adjacent GC-rich region of about 20 nucleotides defined in studies of Moloney murine sarcoma virus enhancer-promoter function (L. A. Laimins, P. Gruss, R. Pozzatti, and G. Khoury, J. Virol. 49:183-189, 1984). The direct repeats of Friend and Moloney viruses are identical in a central core sequence of 32 nucleotides but have sequence differences on either side of this core as well as in their GC-rich segments. To determine whether disease specificity resides in part or in all of the direct repeat and GC-rich region, we constructed recombinants between Friend and Moloney viruses within this segment and tested them for their disease-inducing phenotypes. We found that disease specificity, in particular the ability of Friend virus sequence to confer erythroleukemogenicity on Moloney virus, is encoded throughout the region in at least three separable segments: the 5' and 3' halves of the direct repeat and the GC-rich segment. When just one of these segments (either both 5' halves of the direct repeat, both 3' halves, or just the GC-rich segment) from Friend virus was substituted into a Moloney virus genome, it conferred only a negligible or low incidence of erythroleukemia (less than or equal to 5% to between 10 and 15%). Any two segments together were considerably more potent (35 to 95% erythroleukemia), with the most effective pair being the two halves of the direct repeat. Individual segments and pairs of segments were considerably more potent determinants when they were matched with a genome of the same origin. Thus, although sequences outside the enhancer region are minor determinants of disease specificity when the enhancer is derived entirely from either Friend or Moloney virus, they can play a significant role when the enhancer is of mixed origin. Some recombinant enhancers conferred a long latent period of disease induction. This was particularly striking when the 5' halves of each copy of the direct repeat sequence were derived from Moloney virus and the 3' halves were derived from Friend virus.(ABSTRACT TRUNCATED AT 400 WORDS)

Biologic and molecular genetic characteristics of a unique MCF virus that is highly leukemogenic in ecotropic virus-negative mice

California wild mouse-derived ecotropic virus Cas-Br-M induces a spongiform encephalopathy and a wide variety of hematopoietic neoplasms on inoculation of neonatal mice. We isolated a MCF virus [Ns-6(186) MCF] from a thymic T-cell lymphoma developing in a NFS mouse inoculated with Cas-Br-M virus. Biologically cloned NS-6(186) MCF virus, in contrast to previously studied MCF viruses, was found to induce thymic or nonthymic T-cell lymphomas with high efficiency in the absence of ecotropic helper virus. Comparison of the restriction endonuclease maps derived from Cas-Br-M and NS-6(186) MCF revealed differences only in the env region, between 5.8 and 7.8 kb from the 5' end. Two biologically active molecular clones of the NS-6(186) MCF (clone 15 with two LTRs and clone 19 with 1 LTR) were studied. Although both clones exhibited similar in vitro activities, clone 15-derived virus induced only T-cell lymphomas with short latency whereas clone 19-derived virus induced a wide variety of neoplasms with a significantly longer latency. Nucleotide sequence analysis established that the U3 region of each of the two LTRs of clone 15 has a 53-bp duplication which includes "enhancer elements," but that the single LTR of clone 19 has no such duplication.

CD4+ T cells are required for development of a murine retrovirus-induced immunodeficiency syndrome (MAIDS)

Mice depleted in vivo of CD4+ Th cells by treatment with mAb GK1.5 were found to be resistant to the lymphoproliferative/immunodeficiency disease (MAIDS) induced in intact mice by infection with the mixture of LP-BM5 murine leukemia viruses. Depleted mice did not develop lymphadenopathy or splenomegaly, had normal serum IgM levels, normal CTL responses to alloantigens, and were able to generate PFC responses to Th-independent antigens even though frequencies of virus-producing spleen cells were comparable in depleted and intact mice. Depletion of CD4+ Th cells after infection resulted in a reversal of many abnormalities exhibited by infected controls; spleen weights, serum IgM levels, and allogeneic CTL responses of treated mice were comparable to those of uninfected controls. These results demonstrate that dysfunction of CD4+ Th cells is central to the induction and progression of both T and B cell abnormalities in MAIDS.

Histogenesis and clonality of pancreatic tumors induced by v-myc and v-raf oncogenes in NFS/N mice

Newborn NFS/N mice were inoculated with pseudotypes of murine retroviruses containing murine v-raf, avian v-myc, or both v-raf and v-myc within a single construct. Foci of dysplastic acinar cells, similar to those observed in rats given chemical carcinogens, were induced in 77% of mice inoculated with the raf/myc construct with a latency as short as 15 days. However, all animals given this construct also developed fibrosarcomas, erythroblastosis, and lymphomas and died within 70 days of infection, before pancreatic acinar carcinomas developed. Dysplastic foci were also observed in mice infected with viruses containing v-raf or v-myc alone with latencies of 3-4 weeks, and carcinomas were seen after an average latency of 150 days in 31% of mice infected with either of two viruses expressing v-myc alone. Two primary carcinomas were transplanted in mice, and in vitro cell lines were developed from one of the transplants. DNA prepared from seven primary carcinomas, the two transplanted tumors, and the in vitro cell lines was hybridized with a v-myc probe. Each tumor had a unique pattern of proviral integrations that was retained, with the gain or loss of single sites, in the transplants and derivative cell lines. The clonal nature of the advanced pancreatic acinar carcinomas is discussed in relation to their histogenesis and the transforming potentials of the raf and myc oncogenes.

Evolution of B cell lineage lymphomas in mice with a retrovirus-induced immunodeficiency syndrome, MAIDS

Mice infected with LP-BM5 murine leukemia virus develop lymphadenopathy, splenomegaly, hypergammaglobulinemia, and profound immunosuppression associated with enhanced susceptibility to infection. In this study, molecular genetic analyses of spleen and lymph node cells from infected mice showed the early course of disease was associated with polyclonal proliferations of both B and T cells but that by 12 wk oligoclonal expansions of B or T cells could be detected. When near death, the mice were killed and almost all exhibited clonally restricted populations of B cells, and continuous cultures of B lineage cells were established from three of 19 mice. Histologically, lymph nodes with polyclonal lymphoproliferative lesions were indistinguishable from nodes with clonally restricted populations of cells. However, aggressive immunoblastic lymphomas of characteristic morphology were seen in nonlymphoid organs, particularly in the brain. The demonstration of terminal B cell lymphomas in murine AIDS extends the similarities between this syndrome and AIDS in humans.

Evolution of B cell lineage lymphomas in mice with a retrovirus-induced immunodeficiency syndrome, MAIDS

Mice infected with LP-BM5 murine leukemia virus develop lymphadenopathy, splenomegaly, hypergammaglobulinemia, and profound immunosuppression associated with enhanced susceptibility to infection. In this study, molecular genetic analyses of spleen and lymph node cells from infected mice showed the early course of disease was associated with polyclonal proliferations of both B and T cells but that by 12 wk oligoclonal expansions of B or T cells could be detected. When near death, the mice were killed and almost all exhibited clonally restricted populations of B cells, and continuous cultures of B lineage cells were established from three of 19 mice. Histologically, lymph nodes with polyclonal lymphoproliferative lesions were indistinguishable from nodes with clonally restricted populations of cells. However, aggressive immunoblastic lymphomas of characteristic morphology were seen in nonlymphoid organs, particularly in the brain. The demonstration of terminal B cell lymphomas in murine AIDS extends the similarities between this syndrome and AIDS in humans.

Phenylhydrazine stimulates lymphopoiesis and accelerates Abelson murine leukemia virus-induced pre-B cell lymphomas

Infection of bone marrow or fetal liver cells with Abelson murine leukemia virus (A-MuLV) results in the transformation of pre-B cells and the development of erythroid colonies, indicating that the abl oncogene can affect the growth characteristics of immature cells in both the B cell and erythroid lineages. By comparison, infection of mice with A-MuLV results primarily in the development of pre-B cell lymphomas. To determine whether A-MuLV could induce erythroid disease in vivo, NFS/N mice were pretreated with phenylhydrazine (PHZ) to stimulate erythropoiesis and increase the frequency of potential target cells for A-MuLV. No erythroleukemias developed in mice treated with PHZ. Instead, the latency for pre-B cell lymphomas was reduced by half. This acceleration of disease could be attributed to a marked increase in pre-B cells as targets for transformation by A-MuLV in the bone marrows but not the spleens of treated mice. Increases in the frequencies of T cells in bone marrow and spleen also followed treatment with PHZ. These results show that although PHZ-induced anemia stimulates the production of T and B cells as well as erythroid progenitors, PHZ-treated mice do not develop erythroleukemia or T cell lymphomas. It was also found that the genetically determined resistance of adult C57BL/6 mice to lymphoma induction by A-MuLV could not be overcome by pretreatment with PHZ even though the frequency of pre-B cells in bone marrow was greatly increased by this treatment.