High frequency of transmission of murine AIDS virus in C57BL/10 mice via mother''s milk.

Maternal transmission of a murine leukemia virus (MuLV) mixture named LP-BM5 MuLV, which is knwon to induce murine AIDS (MAIDS), was investigated. Adult female C57BL/10 mice were inoculated intraperitoneally with LP-BM5 MuLV. When the virus-inoculated female mice developed splenomegaly or lymphadenopathy, they were mated with normal C57BL/10 male mice. Of 56 offspring born to MAIDS mothers, 14 appeared to develop MAIDS, as assessed by the occurrence of splenomegaly or lymphadenopathy as well as the mitogen response of spleen cells. The occurrence of MAIDS in offspring was found to be accompanied by the maternal transmission and expansion of a defective virus genome from which almost the entire pol and env regions are deleted. On the other hand, the ecotropic helper virus genome was detected in all offspring regardless of the occurrence of MAIDS. To examine the mode of maternal transmission of LP-BM5 MuLV, foster-nursing experiments were conducted. The ecotropic helper viruses were found in all normal offspring nursed by a MAIDS mother, and some of them developed MAIDS. In contrast, none of offspring born to a MAIDS mother that were nursed by an uninfected foster mother either carried the LP-BM5 MuLV or developed MAIDS. Finally, both the defective and the ecotropic helper viruses were detected in LP-BM5 MuLV-infected mother's milk. These results indicated that maternal transmission of LP-BM5 MuLV occurs with a high frequency and is mediated by mother's milk.     

Analysis of role of CD8+ T cells in resistance to murine AIDS in A/J mice.

The mixture of retroviruses termed LP-BM5 murine leukemia virus (MuLV) contains a replication-defective genome (BM5def), the crucial element for induction of murine AIDS (MAIDS), as well as helper B-tropic ecotropic and mink cell focus-forming MuLV. Among Fv-1b mouse strains, C57BL mice are sensitive to infection by these viruses and to development of MAIDS, but A/J mice are highly resistant to all viral components and to induction of disease. Inasmuch as previous genetic studies indicated a major role in susceptibility for the H-2D locus within the MHC, the effect of CD8+ T cells in A/J resistance to MAIDS was analyzed by depletion of this subset using mAb. A/J mice treated with anti-CD8 mAb beginning soon after inoculation with LP-BM5 MuLV developed disease within 5 wk after virus inoculation. Histopathologic and flow cytometry alteration of tissues and cells from the mAb-treated mice were identical to those seen in virus-infected MAIDS-sensitive strains, and assays for MuLV demonstrated high-level expression of ecotropic MuLV and integration of BM5def. Parallel studies of A/J mice treated with anti-CD4 mAb after infection revealed enhanced expression of ecotropic MuLV but no integration of BM5def, and no signs of MAIDS were detected. These observations indicate that CD8+ T cells are critical in the resistance of A/J mice to LP-BM5 MuLV replication and development of disease and suggest that CD4+ T cells play a role in regulation of ecotropic virus replication.     

Expression of defective virus and cytokine genes in murine AIDS.

A syndrome characterized by severe immunodeficiency and lymphoproliferation develops in susceptible strains of mice infected with a mixture of murine leukemia viruses (MuLVs) designated LP-BM5 MuLV. The etiologic agent in this mixture has been shown to be a replication-defective virus (BM5d) with a 4.8-kb genome that required replication-competent helper viruses, primarily ecotropic (BM5e), for cell-to-cell spread in the host. In the present study, we studied the expression of BM5d and BM5e in tissues of infected mice at various times after inoculation in relation to the expression of cytokine genes that may contribute to the pathogenesis of this disorder. Northern (RNA) analysis of total RNA showed that BM5d was expressed at significant levels in lymphoid tissues within 1 week of infection and that the levels of expression increased with time after inoculation. By 16 weeks postinfection, BM5d was expressed in all tissues examined. Expression of BM5e was relatively more restricted to lymphoid tissues and was detected at lower levels than expression of BM5d at early times after infection, but this virus was expressed in all tissues by 16 weeks. Infection with the virus mixture was associated with constitutive expression of tumor necrosis factor in all tissues examined and of interleukin-1 (IL-1) in lymphoid tissues within 1 week of infection, and at later times with widespread expression of these cytokines and gamma interferon. Also, the levels of interferon regulatory factor 1 mRNA were significantly increased in all infected tissues during the infection. In contrast, expression of IL-3, IL-4, IL-5, and IL-6 was not detectable by Northern analysis of the respective mRNAs in any infected tissue at early or late times postinfection.     

Absence of involvement of nitric oxide in LP-BM5-induced immunodeficiency syndrome

Abstract To examine the role of nitric oxide (NO) in murine AIDS (MAIDS) pathogenesis, we determined NO production and inducible NOS (iNOS) mRNA expression in the macrophages of LP-BM5-infected mice, together with the in vivo effects of l -NAME, a competitive inhibitor of NO synthase. LP-BM5 infection induced neither spontaneous nitrite production nor iNOS mRNA expression. No differences in IFNγ + LPS-induced nitrite production or iNOS mRNA expression were observed in macrophages from non-infected or infected mice. Spleen weight, ecotropic MuLV replication, the blood lymphocyte phenotype and proliferative response of splenocytes were not modified by l -NAME. LP-BM5 infection did not increase macrophage NO production and NO production did not appear to protect against LP-BM5-induced immunodeficiency.     

Profound amplification of pathogenic murine polytropic retrovirus release from coinfected cells

Previous studies indicate that mice infected with mixtures of mouse retroviruses (murine leukemia viruses [MuLVs]) exhibit dramatically altered pathology compared to mice infected with individual viruses of the mixture. Coinoculation of the ecotropic virus Friend MuLV (F-MuLV) with Fr98, a polytropic MuLV, induced a rapidly fatal neurological disease that was not observed in infections with either virus alone. The polytropic virus load in coinoculated mice was markedly enhanced, while the ecotropic F-MuLV load was unchanged. Furthermore, pseudotyping of the polytropic MuLV genome within ecotropic virions was nearly complete in coinoculated mice. In an effort to better understand these phenomena, we examined mixed retrovirus infections by utilizing in vitro cell lines. Similar to in vivo mixed infections, the polytropic MuLV genome was extensively pseudotyped within ecotropic virions; polytropic virus release was profoundly elevated in coinfected cells, and the ecotropic virus release was unchanged. A reduced level of polytropic SU protein on the surfaces of coinfected cells was observed and correlated with a reduced level of nonpseudotyped polytropic virion release. Marked amplification and pseudotyping of the polytropic MuLV were also observed in mixed Fr98-F-MuLV infections of cell lines derived from the central nervous system (CNS), the target for Fr98 pathogenesis. Additional experiments indicated that pseudotyping contributed to the elevated polytropic virus titer by increasing the efficiency of packaging and release of the polytropic genomes within ecotropic virions. Mixed infections are the rule rather than the exception in retroviral infection, and the ability to examine them in vitro should facilitate a more thorough understanding of retroviral interactions in general.     

Tissue-specific replication of Friend and Moloney murine leukemia viruses in infected mice.

We have studied the replication of ecotropic murine leukemia viruses (MuLV) in the spleens and thymuses of mice infected with the lymphocytic leukemia-inducing virus Moloney MuLV (M-MuLV), with the erythroleukemia-inducing virus Friend MuLV (F-MuLV), or with in vitro-constructed recombinants between these viruses in which the long terminal repeat (LTR) sequences have been exchanged. At 1 week after infection both the parents and the LTR recombinants replicated predominantly in the spleens with only low levels of replication in the thymus. At 2 weeks after infection, the patterns of replication in the spleens and thymuses were strongly influenced by the type of LTR. Viruses containing the M-MuLV LTR exhibited a remarkable elevation in thymus titers which frequently exceeded the spleen titers, whereas viruses containing the F-MuLV LTR replicated predominantly in the spleen. In older preleukemic mice (5 to 8 weeks of age) the structural genes of M-MuLV or F-MuLV predominantly influenced the patterns of replication. Viruses containing the structural genes of M-MuLV replicated efficiently in both the spleen and thymus, whereas viruses containing the structural genes of F-MuLV replicated predominantly in the spleen. In leukemic mice infected with the recombinant containing F-MuLV structural genes and the M-MuLV LTR, high levels of virus replication were observed in splenic tumors but not in thymic tumors. This phenotypic difference suggested that tumors of the spleen and thymus may have originated by the independent transformation of different cell types. Quantification of polytropic MulVs in late-preleukemic mice infected with each of the ecotropic MuLVs indicated that the level of polytropic MuLV replication closely paralleled the level of replication of the ecotropic MuLVs in all instances. These studies indicated that determinants of tissue tropism are contained in both the LTR and structural gene sequences of F-MuLV and M-MuLV and that high levels of ecotropic or polytropic MuLV replication, per se, are not sufficient for leukemia induction. Our results further suggested that leukemia induction requires a high level of virus replication in the target organ only transiently during an early preleukemic stage of disease.     

Cytolytic T lymphocytes specific for tumors and infected cells from mice with a retrovirus-induced immunodeficiency syndrome.

LP-BM5 retrovirus complex-infected C57BL/6 mice develop immunodeficiency, somewhat analogous to AIDS, termed murine AIDS (MAIDS). After secondary stimulation with syngeneic B-cell lymphomas from LP-BM5-infected mice, C57BL/6 mice produced vigorous CD8+ cytotoxic T lymphocytes specific for MAIDS-associated tumors. An anti-LP-BM5 specificity was suggested because spleen and lymph node cells from LP-BM5-infected mice served as target cells in competition assays, and cells from LP-BM5, but not ecotropic, virus-infected mice functioned as secondary in vitro stimulators to generate cytotoxic T lymphocytes to MAIDS tumors.     

Increased Brain Levels of Platelet-Activating Factor in a Murine Acquired Immune Deficiency Syndrome Are NMDA Receptor-Mediated

Abstract: Mice infected with the LP-BM5 murine leukemia virus (MuLV) develop an immunodeficiency syndrome (murine AIDS) and an encephalopathy characterized by impaired spatial learning and memory. Because platelet-activating factor (PAF) has been implicated in the pathogenesis of HIV-associated dementia complex, brain PAF levels were measured in LP-BM5 MuLV-infected mice. PAF levels in cerebral cortex and hippocampus were significantly increased at 6 and 12 weeks after LP-BM5 MuLV inoculation, whereas significant increases in striatal and cerebellar PAF levels were observed only at 12 weeks after inoculation. Administration of the NMDA antagonist MK-801 significantly reduced the increased PAF levels in the cerebral cortex and hippocampus of LP-BM5 MuLV-infected mice. These results indicate that the LP-BM5 MuLV-induced increases in brain PAF levels are the result of NMDA receptor activation and are consistent with the hypothesis that elevated CNS PAF levels contribute to the behavioral deficits observed in LP-BM5 MuLV-infected mice.     

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.     

In vivo interactions of ecotropic and polytropic murine leukemia viruses in mixed retrovirus infections

Mixed retrovirus infections are the rule rather than the exception in mice and other species, including humans. Interactions of retroviruses in mixed infections and their effects on disease induction are poorly understood. Upon infection of mice, ecotropic retroviruses recombine with endogenous proviruses to generate polytropic viruses that utilize different cellular receptors. Interactions among the retroviruses of this mixed infection facilitate disease induction. Using mice infected with defined mixtures of the ecotropic Friend murine leukemia virus (F-MuLV) and different polytropic viruses, we demonstrate several dramatic effects of mixed infections. Remarkably, inoculation of F-MuLV with polytropic MuLVs completely suppressed the generation of new recombinant viruses and dramatically altered disease induction. Co-inoculation of F-MuLV with one polytropic virus significantly lengthened survival times, while inoculation with another polytropic MuLV induced a rapid and severe neurological disease. In both instances, the level of the polytropic MuLV was increased 100- to 1,000-fold, whereas the ecotropic MuLV level remained unchanged. Surprisingly, nearly all of the polytropic MuLV genomes were packaged within F-MuLV virions (pseudotyped) very soon after infection. At this time, only a fractional percentage of cells in the mouse were infected by either virus, indicating that the co-inoculated viruses had infected the same small subpopulation of susceptible cells. The profound amplification of polytropic MuLVs in coinfected mice may be facilitated by pseudotyping or, alternatively, by transactivation of the polytropic virus in the coinfected cells. This study illustrates the complexity of the interactions between components of mixed retrovirus infections and the dramatic effects of these interactions on disease processes.     

Abrogation of resistance to severe mousepox in C57BL/6 mice infected with LP-BM5 murine leukemia viruses.

Strain C57BL/6 (B6) mice infected with LP-BM5 murine leukemia virus (MuLV) develop a disease which combines abnormal lymphoproliferation with profound immunosuppression and has many features in common with human acquired immunodeficiency syndrome induced by HTLV-III/LAV retroviruses. To determine whether this LP-BM5 MuLV infection would affect the innate resistance of B6 mice to a naturally occurring, highly virulent murine pathogen, mice were exposed to ectromelia virus at various times after treatment with LP-BM5 viruses. At week 4 after infection with LP-BM5, mice challenged with ectromelia virus were unable to generate a humoral immune response to this virus, and between weeks 8 and 10 after infection, challenged mice lost the ability to generate an ectromelia virus-specific cytotoxic-T-cell response. Loss of the cellular immune responses to ectromelia virus was associated with an increased susceptibility to the lethal effects of the virus.     

Enhanced survival by vitamin A supplementation during a retrovirus infection causing murine AIDS

Infection by LP-BM5 murine leukemia virus (MuLV) produces an AIDS-like condition in mice. The viral infection suppressed the percentage of peripheral blood cells showing surface markers for macrophages, activated macrophages, T lymphocytes and activated lymphoid cells. High dietary vitamin A (retinyl palmitate) caused increased numbers of activated macrophages. It also increased the percentage of cells with markers for Ia+ cells and macrophages in the retrovirally infected mice compared to infected controls. In uninfected mice retinyl palmitate stimulated the percentage of cells with activated lymphocytes bearing IL-2R, and T cytotoxic cells. These were associated with a retarded death rate during infection with LP-BM5 murine leukemia in C57BL/6 mice. By 25 weeks of infection and 20 weeks of retinyl palmitate supplementation 71.3% survived, while 45.0% virally infected controls survived. The mice also had elevated numbers of B cells measured in the blood after 4 and 8 weeks of dietary treatment. Vitamin A stimulation may play a role in the slower death rate for retrovirally infected mice.     

Aberrant expression of cytokine genes in peritoneal macrophages from mice infected with LP-BM5 MuLV, a murine model of AIDS.

Mice infected with LP-BM5 murine leukemia virus (MuLV) develop a syndrome denoted as murine AIDS. Macrophages harvested from the peritoneal cavities of these mice at 4 or 9 wk postinoculation with LP-BM5 MuLV were analyzed by Northern hybridization for the presence of the defective LP-BM5 virus and their ability to synthesize various cytokines upon induction with Newcastle disease virus (NDV) or (LPS). Neither IFN-alpha or IFN-beta was found to be constitutively expressed in LP-BM5-infected macrophages and in NDV induction studies, and the levels of biologically active IFN-alpha and its mRNA were found to be lower in LP-BM5 MuLV-infected macrophages than in the macrophages from uninfected controls. Similarly, after NDV or LPS induction, the levels of TNF mRNA and TNF protein were significantly lower in LP-BM5-infected macrophages than in macrophages from uninfected mice. The LP-BM5 MuLV-infected macrophages constitutively expressed low levels of IL-1 beta, and when induced with LPS, the relative levels of IL-1 beta were significantly higher in infected than in uninfected macrophages. Although no constitutive expression of IL-6 was detected, the levels of IL-6 mRNA induced with NDV were higher in LP-BM5 MuLV-infected macrophages than in controls. Thus, we found alterations in the expression of selected cytokines in macrophages from mice inoculated with LP-BM5 MuLV rather than a general deregulation of all cytokine expression. These results show that macrophages infected with the defective LP-BM5 virus respond differently to NDV- or LPS-stimulation and suggest that aberrant expression of certain cytokine genes may play a role in the immunopathologic condition in mice with murine AIDS.     

Dissociation between lymphoproliferative responses and virus replication in mice with different sensitivities to retrovirus-induced immunodeficiency.

Murine AIDS (MAIDS) is induced by a replication-defective virus (BM5d). In susceptible mice (C57BL/6J), inoculation with LP-BM5 murine leukemia virus, which consists of the BM5d virus and replication-competent B-tropic ecotropic (BM5e) and milk cell focus-inducing (BM5-MCF) helper viruses results in the polyclonal proliferation of T and B cells, immunodeficiency, and the expansion of B cells containing the BM5d provirus followed by the development of B-cell lymphomas. Several strains of mice that are resistant to LP-BM5-induced murine AIDS have been identified, and major histocompatibility complex genes as well as non-major histocompatibility complex genes were shown to play a role in this resistance. In the present study, we have examined and compared the replication of the BM5d and BM5e viruses after inoculation of LP-BM5 into sensitive (C57BL/6J) and resistant (C57BL/KSJ) mice. Using a specific polymerase chain reaction, we could detect the BM5d and BM5e proviruses as early as 1 week postinfection in the sensitive mice, and the levels of both viruses increased significantly with the progression of the disease. In contrast, in the resistant C57BL/KSJ mice, replication of BM5d and BM5e was restricted and no BM5d and only very low levels of the BM5e provirus could be detected either at early or late times postinoculation with the LP-BM5 virus mixture. Inoculation with LP-BM5 did not lead to the production of antibodies that could recognize the BM5d-encoded Pr60gag in either the sensitive or resistant mice; however, production of antibodies recognizing the env-related proteins of the helper virus was detected in the resistant but not in the sensitive mice at late times postinfection. Interestingly, inoculation with LP-BM5 increased polyclonal stimulation of spleen cells and decreased mitogen stimulation in both strains of mice. This stimulation of splenocytes persisted in the sensitive mice but decreased after a few weeks in the resistant mice. These results show an early block in BM5d and BM5e replication in the resistant C57BL/KSJ mice and indicate that resistance is a consequence of the inhibition of an onset of the BM5d virus infection and its expansion. However, initial responses to virus infection such as proliferation of spleen cells and response to mitogen are similar in both strains of mice and are therefore not necessarily related to the development of the disease.     

Expression of ecotropic murine leukemia virus in the brains of C58/M, DBA2/J, and in utero-infected CE/J mice.

In C58 and AKR mice, endogenous N-tropic, ecotropic murine leukemia virus (MuLV) proviruses become activated in rare cells during embryogenesis. Resultant replication-competent progeny viruses then actively infect a large number of cells throughout the fetus, including cells in the developing central nervous system. By in situ hybridization analyses, we have assessed the presence of ecotropic MuLV RNA in the brains of C58 mice as a function of age. Only a few ecotropic MuLV-positive cells were observed in weanling mice, but the number of positive cells in the brain increased progressively with increasing age of the mice. Throughout the lives of the mice, the ecotropic MuLV RNA-positive cells were primarily located in well-defined white-matter tracts of the brain (commissura anterior, corpus callosum, fimbria hippocampi, optical tract, and striatum) and of the spinal cord. Cells of the subventricular zone also expressed ecotropic MuLV RNA, and in older mice a small number of positive cells were present in the grey matter. Infection of endogenous ecotropic MuLV provirus-less CE/J mice in utero with ecotropic MuLV clone AKR-623 resulted in the extensive infection of brain cells. The regional distribution of ecotropic MuLV RNA-containing cells was the same as observed in the brains of C58 mice, in which cells became infected by endogenously activated virus, but the number of positive cells was higher.     

Identification of a spleen focus-forming virus in erythroleukemic mice infected with a wild-mouse ecotropic murine leukemia virus

An NFS/N mouse inoculated at birth with an ecotropic murine leukemia virus (MuLV) obtained from wild mice (Cas-Br-M MuLV) developed a lymphoma after 18 weeks. An extract prepared from the lymphomatous spleen was inoculated into newborn NFS/N mice, and these mice developed erythroleukemia within 9 weeks. Spleens from the erythroleukemic mice contained ecotropic and mink cell focus-inducing (MCF) MuLVs; however, when these viruses were biologically cloned and reinoculated into newborn NFS/N mice, no erythroleukemia was induced. In contrast, cell-free extracts prepared from the erythroleukemic spleens induced erythroleukemia within 5 weeks. Analysis of cell-free extracts prepared from the erythroleukemic spleens showed that they contained a viral species that induced splenomegaly and spleen focus formation in adult mice, with susceptibility controlled by alleles at the Fv-2 locus. The spleen focus-forming virus coded for a 50,000-dalton protein precipitated by antibodies specific to MCF virus gp70. RNA blot hybridization studies showed the genomic viral RNA to be 7.5 kilobases and to hybridize strongly to a xenotropic or MCF envelope-specific probe but not to hybridize with an ecotropic virus envelope-specific probe. The virus described here appears to be the fourth independent isolate of a MuLV with spleen focus-forming activity.     

Suppression of neurocognitive damage in LP-BM5-infected mice with a targeted deletion of the TNF-alpha gene.

Brain levels of TNF-alpha increase in many inflammatory conditions, including HIV-1 infection, and may contribute to neurodegenerative processes. The paucity of agents that can selectively and potently block TNF-alpha processing or its receptors has led us to investigate the role of TNF-alpha in chronic neurodegeneration associated with retroviral infection using mice with targeted deletions of the TNF-alpha gene. Infection of wild-type C57BL/6 mice with the LP-BM5 murine leukemia retrovirus mixture leads to the development of a severe immunodeficiency as well as cognitive deficits and neuronal damage. TNF-alpha-(-/-) mice infected with LP-BM5 developed a systemic immunopathology indistinguishable in severity from that observed in contemporaneously infected wild-type mice. In contrast, the performance of infected TNF-alpha-(-/-) mice in the Y-maze and Morris water maze was not different from that of uninfected TNF-alpha-(-/-) mice. The extent of glial activation in the striatum, as indicated by the increase in density of peripheral benzodiazepine receptors, was equivalent in both groups of LP-BM5-infected mice. However, the decrease in striatal MAP-2 expression, a marker of neurodegeneration observed in infected wild-type mice, was not found in infected TNF-alpha-(-/-) mice. While the loss of TNF-alpha appeared to have no effect on the course or severity of the central or peripheral immunopathology resulting from LP-BM5 infection, the behavioral and biochemical manifestations were substantially curtailed in the TNF-alpha-(-/-) mice. These findings directly support a role for TNF-alpha in the neurodegenerative processes associated with viral infections such as HIV-1.     

Analysis of the ex vivo and in vivo antiretroviral activity of gemcitabine

Replication of retroviral and host genomes requires ribonucleotide reductase to convert rNTPs to dNTPs, which are then used as substrates for DNA synthesis. Inhibition of ribonucleotide reductase by hydroxyurea (HU) has been previously used to treat cancers as well as HIV. However, the use of HU as an antiretroviral is limited by its associated toxicities such as myelosuppression and hepatotoxicity. In this study, we examined the ribonucleotide reductase inhibitor, gemcitabine, both in cell culture and in C57Bl/6 mice infected with LP-BM5 murine leukemia virus (LP-BM5 MuLV, a murine AIDS model). Gemcitabine decreased infectivity of MuLV in cell culture with an EC50 in the low nanomolar range with no detectable cytotoxicity. Similarly, gemcitabine significantly decreased disease progression in mice infected with LP-BM5. Specifically, gemcitabine treatment decreased spleen size, plasma IgM, and provirus levels compared to LP-BM5 MuLV infected, untreated mice. Gemcitabine efficacy was observed at doses as low as 1 mg/kg/day in the absence of toxicity. Higher doses of gemcitabine (3 mg/kg/day and higher) were associated with toxicity as determined by a loss in body mass. In summary, our findings demonstrate that gemcitabine has antiretroviral activity ex vivo and in vivo in the LP-BM5 MuLV model. These observations together with a recent ex vivo study with HIV-1, suggest that gemcitabine has broad antiretroviral activity and could be particularly useful in vivo when used in combination drug therapy.     

Cofilin activation in peripheral CD4 T cells of HIV-1 infected patients: a pilot study

The mouse macrophage-like cell line RAW264.7, the most commonly used mouse macrophage cell line in medical research, was originally reported to be free of replication-competent murine leukemia virus (MuLV) despite its origin in a tumor induced by Abelson MuLV containing Moloney MuLV as helper virus. As currently available, however, we find that it produces significant levels of ecotropic MuLV with the biologic features of the Moloney isolate and also MuLV of the polytropic or MCF class. Newborn mice developed lymphoma following inoculation with the MuLV mixture expressed by these cells. These findings should be considered in interpretation of increasingly widespread use of these cells for propagation of other viruses, studies of biological responses to virus infection and use in RNA interference and cell signalling studies.