Myeloid-derived suppressor cells in murine AIDS inhibit B-cell responses in part via soluble mediators including reactive oxygen and nitrogen species, and TGF-β

Monocytic myeloid-derived suppressor cells (M-MDSCs) were increased during LP-BM5 retroviral infection, and were capable of suppressing not only T-cell, but also B-cell responses. In addition to previously demonstrating iNOS- and VISTA-dependent M-MDSC mechanisms, in this paper, we detail how M-MDSCs utilized soluble mediators, including the reactive oxygen and nitrogen species superoxide, peroxynitrite, and nitric oxide, and TGF-β, to suppress B cells in a predominantly contact-independent manner. Suppression was independent of cysteine-depletion and hydrogen peroxide production. When two major mechanisms of suppression (iNOS and VISTA) were eliminated in double knockout mice, M-MDSCs from LP-BM5-infected mice were able to compensate using other, soluble mechanisms in order to maintain suppression of B cells. The IL-10 producing regulatory B-cell compartment was among the targets of M-MDSC-mediated suppression.

Morphine increases hippocampal viral load and suppresses frontal lobe CCL5 expression in the LP-BM5 AIDS model

Chronic opiate abuse accelerates the development of cognitive deficits in human immunodeficiency virus (HIV)-1 patients. To investigate morphine's effects on viral infection of the central nervous system, we applied chronic morphine treatment to the LP-BM5 murine acquired immunodeficiency syndrome (MAIDS) model. LP-BM5 infection induces proinflammatory cytokine/chemokine production, correlating to increased blood-brain barrier permeability. Morphine treatment significantly increased LP-BM5 viral load in the hippocampus, but not in the frontal lobe. Morphine reduced the chemokine CCL5 to non-infected levels in the frontal lobe, but not in the hippocampus. These data indicate a region-specific mechanism for morphine's effects on virally-induced neurocognitive deficits.

Blockade of interferon-?-inducible protein-10 attenuates chronic experimental colitis by blocking cellular trafficking and protecting intestinal epithelial cells

The role of chemokines, especially CXCL10/interferon-gamma-inducible protein 10 kDa (IP-10), a chemokine to attract CXCR3(+) T-helper 1-type CD4(+) T cells, is largely unknown in the pathophysiology of inflammatory bowel disease; ulcerative colitis and Crohn's disease. The authors have earlier shown that IP-10 neutralization protected mice from acute colitis by protecting crypt epithelial cells of the colon. To investigate the therapeutic effect of neutralization of IP-10 on chronic colitis, an anti-IP-10 antibody was injected into mice with newly established murine AIDS (MAIDS) colitis. Anti-IP-10 antibody treatment reduced the number of colon infiltrating cells when compared to those mice given a control antibody. The treatment made the length of the crypt of the colon greater than control antibody. The number of Ki67(+) proliferating epithelial cells was increased by the anti-IP-10 antibody treatment. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)(+) apoptotic cells were observed in the epithelial cells of the luminal tops of crypts in control MAIDS colitis, whereas TUNEL(+) apoptotic epithelial cells were rarely observed with anti-IP-10 antibody treatment. In conclusion, blockade of IP-10 attenuated MAIDS colitis through blocking cellular trafficking and protecting intestinal epithelial cells, suggesting that IP-10 plays a key role in the development of inflammatory bowel disease as well as in chronic experimental colitis.

Cyclo-oxygenase type 2-dependent prostaglandin E2 secretion is involved in retrovirus-induced T-cell dysfunction in mice

MAIDS (murine AIDS) is caused by infection with the murine leukaemia retrovirus RadLV-Rs and is characterized by a severe immunodeficiency and T-cell anergy combined with a lymphoproliferative disease affecting both B- and T-cells. Hyperactivation of the cAMP-protein kinase A pathway is involved in the T-cell dysfunction of MAIDS and HIV by inhibiting T-cell activation through the T-cell receptor. In the present study, we show that MAIDS involves a strong and selective up-regulation of cyclo-oxygenase type 2 in the CD11b+ subpopulation of T- and B-cells of the lymph nodes, leading to increased levels of PGE2 (prostaglandin E2). PGE2 activates the cAMP pathway through G-protein-coupled receptors. Treatment with cyclo-oxygenase type 2 inhibitors reduces the level of PGE2 and thereby reverses the T-cell anergy, restores the T-cell immune function and ameliorates the lymphoproliferative disease.

Dilated cardiomyopathy in retrovirally infected mice: a novel model for silent viral DCM?

Dilated cardiomyopathy (DCM) is a clinically relevant disease that can occur independently or secondary to other diseases such as HIV infection and AIDS. To study this latter process, we used a model in which mice are infected with the LP-BM5 murine AIDS (MAIDS) retrovirus. Cardiac function of control and infected mice was determined through the in vivo analysis of left ventricular pressure-volume loops. Furthermore, the role of myocarditis was investigated through immunohistochemistry for T-cell, B-cell, and macrophage cardiac infiltrates and Northern blot analysis for tumor necrosis factor (TNF)-alpha and inducible nitric oxide synthase (iNOS). End-systolic and end-diastolic volumes were significantly increased and ventricular stiffness was significantly decreased in infected mice, consistent with DCM; however, no staining for inflammatory cellular infiltrates or TNF-alpha and iNOS was seen. These data support the conclusion that the LP-BM5 HIV model virus causes DCM in the absence of chronic cardiac inflammation. These findings support MAIDS retroviral infection as a new model of idiopathic DCM in which myo-carditis does not occur.

Murine retrovirus infection and the effect of chronic alcohol consumption: proteomic analysis of cardiac protein expression

AIMS

The cardiovascular complications of acquired immunodeficiency syndrome (AIDS) are serious, including the occurrence of pathological heart conditions such as cardiomyopathy. Chronic alcohol consumption accentuates the severity of AIDS and may contribute to the development of cardiomyopathy. The aim of this work was to use a proteomics approach to investigate global alterations in protein expression in a mouse model of AIDS in the presence or absence of chronic alcohol consumption.

METHODS

Cardiac proteins were separated by two-dimensional polyacrylamide gel electrophoresis and quantitative computer analysis was used to evaluate the resulting two-dimensional protein profiles. Proteins that were differentially expressed in the hearts of mice from the different experimental groups were identified by peptide mass finger-printing by matrix-assisted laser desorption/ionization mass spectrometry.

RESULTS

A number of specific proteins were observed to be differentially expressed in the mouse heart due to the effect of ethanol feeding alone. Differentially expressed proteins were also observed that were due to viral infection alone. Ethanol feeding and viral infection appeared to have similar effects on the expression of a number of proteins. A total of 24 proteins were altered by infection alone. Of these 24 proteins, eight were affected by alcohol, with six alterations being ameliorated and two being exacerbated by alcohol. Two of these proteins have been identified as the 27 kDa heat-shock protein and mitochondrial long-chain acyl-CoA thioesterase 1.

CONCLUSIONS

These results suggest that chronic alcohol consumption may exacerbate the effects of viral infection on the heart by lowering the stress response leading to de-protection and further cytotoxic effects.

Murine cytomegalovirus retinitis during MAIDS: Susceptibility correlates with elevated intraocular levels of interleukin-4 mRNA

PURPOSE

To determine if murine cytomegalovirus (MCMV)-infected eyes of mice with murine acquired immunodeficiency syndrome (MAIDS) that are destined to develop MCMV retinitis display elevated intraocular levels of interleukin-4 (IL-4) mRNA when compared with uninfected eyes of mice with MAIDS and unmanipulated, uninfected, eyes of normal healthy mice.

METHODS

Groups of C57BL/6 mice with MAIDS and normal C57BL/6 mice were infected uniocularly with MCMV by subretinal MCMV injection. IL-4 levels in individual spleens collected five days later from groups of MAIDS mice and normal mice were assessed by quantitative ELISA. MCMV-infected eyes and uninfected contralateral eyes from another group of mice with MAIDS were also collected at five days postinfection and individually subjected to competitive RT-PCR assay and real-time RT-PCR assay for detection and quantification of IL-4 mRNA. Unmanipulated eyes from normal C57BL/6 mice served as controls.

RESULTS

IL-4 mRNA was detected at a level of 9.7 +/- 3.4 pg mRNA per 1000 ng total RNA in 100% of MCMV-infected eyes of mice with MAIDS by competitive RT-PCR assay, but could not be detected in any of the uninfected eyes of MAIDS mice. In comparison, the more sensitive technique of real-time RT-PCR assay detected copies of IL-4 cDNA in both MCMV-infected eyes and uninfected eyes of MAIDS mice. MCMV-infected eyes showed a 16-fold increase in the number of IL-4 cDNA copies when compared with uninfected eyes. Neither technique detected IL-4 mRNA in unmanipulated eyes of normal mice. As expected, spleen cells from mice with MAIDS expressed significantly greater levels of IL-4 when compared with spleen cells from normal mice.

CONCLUSIONS

MCMV-infected mice with MAIDS exhibited an expected preferential activation of Th2 cells as determined by increased levels of IL-4 in spleen cells when compared with spleen cells of normal mice. MCMV-infected eyes destined to develop retinitis during MAIDS also showed increased levels of detectable IL-4 mRNA when compared with uninfected eyes of mice with MAIDS. It is therefore possible that IL-4 synthesis by Th2 CD4+ T cells during retrovirus-induced immunosuppression serves to inhibit the perforin cytotoxic pathway that subsequently allows susceptibility to MCMV retinitis during MAIDS.

Induction of CD4 T cell changes in murine AIDS is dependent on costimulation and involves a dysregulation of homeostasis

Strong CD4 T cell activation and proliferation are seen in susceptible mice infected with the murine retroviral inoculum, LP-BM5, which produces an immunodeficiency syndrome called murine AIDS (MAIDS). We developed a short term adoptive transfer model of MAIDS to examine the requirements for the CD4 T cell response. Naive CD4 T cells from uninfected donors responded quickly after adoptive transfer into MAIDS-infected hosts, becoming activated and proliferating within several days. Using blocking mAbs to costimulatory ligands and CD4 T cells deficient in expression of their receptors, we found that the CD4 T cell response requires CD28:B7.1/B7.2 interactions, but not CTLA4 or CD40-CD40 ligand interactions. Naive CD4 T cells did not respond in H-2M-deficient mice with MAIDS, suggesting that disease requires recognition of self peptide-MHC complexes. The self MHC-dependent division and accumulation of large numbers of CD4 T cells suggest that MAIDS involves a disruption of the balance of homeostatic signals. Supporting this hypothesis, CD4 T cells from mice with MAIDS failed to regulate the homeostatic division of naive CD4 T cells in a cotransfer model. Thus, a combination of up-regulation of costimulatory ligands and disruption of homeostatic control may be responsible for CD4 lymphoproliferation in MAIDS.

Role of virus replication in a murine model of AIDS-associated interstitial pneumonitis

One of the major complications of HIV infection is the development of interstitial pneumonitis (IP). IP is characterized by lymphocytic infiltration of the lung and may lead to respiratory failure in some cases. The etiology of IP is unknown although it is likely the result of an antiviral or autoimmune response occurring in the lung. To determine the role of viral replication in the development of IP, AZT was evaluated for the ability to inhibit development of lung inflammation in a murine model of retrovirus-associated IP. Mice were infected with LP-BM5 retrovirus, which induces murine AIDS. Infected mice develop IP by 4 weeks postinfection characterized by infiltration of the lung with activated T cells, B cells, and macrophages. Virus could be detected in the lungs of these mice by 2 weeks postinfection and persisted throughout the course of disease. To determine if reduction in viral load affected the disease process, infected mice were treated with AZT for varying periods postinfection and analyzed for the development of IP. Treatment with AZT resulted in a treatment time-dependent reduction of viral RNA in the lungs of infected mice compared to untreated infected mice. The reduction of viral burden in the lungs correlated with a reduction in the severity of IP and decreased production of the proinflammatory cytokines interleukin (IL)-1 beta and interferon (IFN)-gamma. These results suggest that continuous viral replication in the lung contributes to the pathogenesis of IP.

Supplementation with Lactobacillus reuteri or L. acidophilus reduced intestinal shedding of cryptosporidium parvum oocysts in immunodeficient C57BL/6 mice

The effect of L. acidophilus supplementation to reduce fecal shedding of Cryptosporidium parvum oocysts was compared to L. reuteri using C57BL/6 female mice immunosuppressed by murine leukemia virus (strain LP-BM5) inoculation. After 12 weeks post LP-BM5 inoculation, 15 immunosuppressed mice each were randomly assinged to one of the following treatment groups: historical control (group A), LP-BM5 control (group B), C. parvum (group C), L. reuteri plus C. parvum (group D) or L. acidophilus plus C. parvum (group E). Mice were pre-fed the L. reuteri or L. acidophilus bacteria strains daily for 13 days, challenged with C. parvum oocysts and thereafter fed the specified Lactobacillus regimens daily during the experimental period. Animals supplemented with L. reuteri shed fewer (p<0.05) oocysts on day-7 post C. parvum challenge compared to controls. Mice supplemented with L. acidophilus also shed fewer (p<0.05) oocysts on days 7 and 14 post-challenge compared to controls. Overall, Lactobacillus supplementation reduced C. parvum shedding in the feces but failed to suppress the production of T-helper type 2 cytokines [interleukin-4 (IL-4), IL-8)] which are associated with immunosuppression. Additionally, Lactobacillus supplementation did not restore T-helper type 1 cytokines (interleukin-2 (IL-2) and gamma interferon (IFN-gamma), which are required for recovery from parasitic infections. Altered T-helper types 1 and 2 cytokine production as a consequence of immunodysfunction permitted the development of persistent cryptosporidiosis while mice with intact immune system were refractory to infection with C. parvum. Reduction in shedding of oocysts observed in the Lactobacillus supplemented mice during deminished IL-2 and IFN-gamma production may be mediated by factors released into the intestinal lumen by the Lactobacillus and possibly other host cellular mechanisms. These observations suggest that L. reuteri or L. acidophilus can reduce C. parvum parasite burdens in the intestinal epithelium during cryptosporidiosis and may serve potential benefits as probiotics for host resistance to intestinal parasitic infections. L. acidophilus was more efficacious in reducing fecal shedding than L. reuteri and therefore may also have implication in the therapy of cryptosporidiosis during immunosuppressive states including human AIDS.

Activation of the ubiquitin proteolytic system in murine acquired immunodeficiency syndrome affects IkappaBalpha turnover

Murine acquired immunodeficiency syndrome (MAIDS) is a complex immunopathology caused by a defective murine leukemia virus (LP-BM5) that mainly targets B-lymphocytes. Lymphadenophathy, splenomegaly, hypergammaglobulinemia and progressive immunodeficiency are prominent features of MAIDS. Previously, we showed that the ubiquitin proteolytic system was upregulated in infected lymph nodes [Crinelli, R., Fraternale, A., Casabianca, A. & Magnani, M. (1997) Eur. J. Biochem. 247, 91-97]. In this report, we demonstrate that increased 26S proteasome activity is responsible for accelerated turnover of the IkappaBalpha inhibitor in lymph node extracts derived from animals with MAIDS. The molecular mechanisms mediating IkappaBalpha proteolysis involved constitutive phosphorylation of IkappaBalpha at Ser32 and Ser36 and subsequent ubiquitination, suggesting persistent activation of an NF-kappaB inducing pathway. Interestingly, enhanced IkappaBalpha degradation did not result in enhanced NF-kappaB DNA binding activity, but rather in a different subunit composition. The modulation of NF-kappaB/IkappaB system may affect multiple immunoregulatory pathways and may in part explain the mechanisms leading to the profound immune dysregulation involved in MAIDS pathogenesis.

Extracellular glutamate levels are chronically elevated in the brains of LP-BM5-infected mice: a mechanism of retrovirus-induced encephalopathy

Mice infected with the LP-BM5 leukemia retrovirus mixture develop a progressive immunodeficiency with associated behavioral, histological, and neurochemical alterations consistent with glutamatergic hyperactivation. To gain insight into the contribution of excitatory amino acids to the neurodegeneration observed in these mice, their concentrations were measured in the CSF and striatal microdialysates. Glutamate concentrations were significantly elevated in CSF but not plasma as early as 4 weeks postinoculation. Steady-state glutamate levels in striatal microdialysates were increased threefold and could be reduced 40% by application of L-alpha-aminoadipate, an inhibitor of microglial glutamate transport. Stimulation of infected mice with KCl/L-trans-2,4-pyrrolidine dicarboxylate further increased glutamate levels 170-270% above those evoked in control mice. Tetrodotoxin suppressed the depolarization-evoked increase in glutamate by 88% in control mice, but it had only negligible effects in 40% of infected mice. Analysis of glutamate transport and catabolism suggests that abnormal astrocytic function does not contribute to the increase in basal extracellular glutamate levels. These findings are the first direct evidence that infection with an immunodeficiency-inducing retrovirus leads to a chronic elevation of extracellular free glutamate levels in the brain, which contributes to the neurodegenerative and cognitive deficits observed in these mice.

Reciprocal regulation of protein tyrosine kinases p56lck and p59fyn, and altered tyrosine phosphorylation in murine AIDS

Murine AIDS (MAIDS), caused by a defective murine leukemia virus, is a severe lymphoproliferative disease associated with profound immunodeficiency and increased susceptibility to opportunistic infections. Most subsets of lymphocytes, including CD4+ and CD8+ T cells, are refractory to mitogen stimulation. As a first step to examine proximal signal transduction in the infected mice, Western and Northern blot analyses were performed, and showed that p56lck is dramatically decreased at the protein as well as the mRNA level in the lymph nodes (LN). In contrast, p59(fyn) and its mRNA were slightly increased in the LN of the same mice. Similar results were obtained with purified T cells. Interestingly, the thymus of the infected animals did not show any abnormality regarding p56(lck) or p59(fyn). Tyrosine phosphorylation was constitutively increased in the infected mice and was barely amplified by anti-CD3 mAb stimulation. A similar pattern was observed when tyrosine phosphorylation was selectively examined at the level of ZAP-70. Our results suggest that a reciprocal regulation of p56(lck) and p59(fyn) protein tyrosine kinases, previously described in various models of anergy, could also be involved in the pathogenesis of MAIDS.

Decreased protein levels of the c-Cbl protooncogene in murine AIDS

Murine acquired immunodeficiency syndrome (MAIDS) can be viewed as a lymphoproliferative disease which involves B cells as well as T cells from spleen and lymph nodes while thymus and Peyer's patches do not participate in the process. The 120-kDa protooncogene product c-Cbl was initially cloned from the murine Cas NS-1 B cell lymphoma. It is a main target of immunoreceptor (TCR and BCR)-mediated protein tyrosine kinase activity. Moreover, recent data suggest that c-Cbl might play a crucial role in the regulation of cell proliferation through regulation of GTP-binding proteins. Therefore, the involvement of c-Cbl was evaluated in the lymphoproliferative disease induced by the MAIDS virus. The expression of the c-Cbl protein was dramatically reduced in the lymph node of infected mice while it remained normal in the thymus. In contrast, the expression of actin, TCR-zeta chain, ZAP-70, and p59(fyn) remained similar in controls and infected mice. Identical results were obtained with sorted B cells and T cells. Surprisingly, a B cell lymphoma line derived from late stage MAIDS mice displayed a normal level of c-Cbl.

The effects of lithium gamma-linolenic acid in reversing LPBM5 MuLV induced suppression of hematopoietic progenitor cells in vitro

Lithium gamma linolenic acid (Li-GLA), was evaluated for its possible role as an antiviral agent. Li-GLA 15 micrograms ml-1 was administered to both normal and LP-BM5 MuLV retroviral infected murine bone marrow cultures. After 2 weeks of treatment, numbers of progenitors being produced by infected/treated cultures were reduced to some 10% that of normal cultures. In the remaining 4 weeks, numbers of CFU-GM and BFU-E hematopoietic progenitors returned within normal range. The efficacy of Li-GLA in relieving retroviral hematopoietic bone marrow suppression correlates to a reduction in interleukin-4 (IL-4) secretion, normally elevated in association with LP-BMP5 infection. These data indicate that this reduction in bone marrow suppression of LP-BMP5 infected cells may be due to a killing of infected cells by the Li-GLA, rather than stimulating hematopoiesis as with other lithium compounds. To conclude this may indicate the possible dual effect of administration of LiGLA to virally infected individuals in reducing viral titre and to lower the toxicities associated with long term drug therapy.

Changes in 1,25-(OH)2D3 synthesis and its receptor expression in spleen cell subpopulations of mice infected with LPBM5 retrovirus

This study examines the influence of chronic retroviral infection of mice with a LPBM5 virus mixture on the paracrine system involving immune cells and 1,25-(OH)2D3 in the spleen. Plasma ionized calcium, 25-(OH)D and 1,25-(OH)2D of infected mice were unchanged. In contrast, the specific binding of 1,25-(OH)2D3 to spleen cytosol and the number of monocyte/macrophages expressing 1,25-(OH)2D3 receptors (VDR) were markedly increased. The retroviral infection also influenced the local production of 1,25-(OH)2D3 in the spleen. It did not alter this production in monocyte/macrophages but increased that in isolated T cells. Isolated B cells in control mice did not produce 1,25-(OH)2D3, but they increased the ability of isolated T cells to produce this metabolite during coculture incubations. Infection altered this cell interaction as 1,25-(OH)2D3 production in infected T cells decreased when these cells were cocultured with infected B cells. Thus, chronic retroviral infection alters both the local vitamin D metabolism and VDR expression by immune cells in mice. These findings suggest close local interactions between 1,25-(OH)2D3 and immune system activation during retroviral infection.

Cytokine dysregulation and increased oxidation is prevented by dehydroepiandrosterone in mice infected with murine leukemia retrovirus

The effects of murine leukemia retrovirus infection on production of cytokines was investigated in mice fed different doses of dehydroepiandrosterone (DHEA). Young C57BL/6 female mice were injected with LP-BM5 murine retrovirus or were kept as uninfected controls. Two weeks later, each group was divided into subgroups: fed unsupplemented AIN 93 diet as the control, or diets supplemented with 0.02% DHEA (0.9 mg/mouse/day) or 0.06% DHEA (2.7 mg/mouse/day). The uninfected mice supplemented with 0.06% DHEA showed a significant (P < 0.05) increase in interleukin-2 (IL-2) and gamma-interferon (IFN-gamma) production, and hepatic vitamin E levels. Retroviral infection induced severe oxidative stress that was reduced by DHEAS supplementation in retrovirally infected mice. DHEA supplementation prevented the retrovirus-induced loss of cytokines (IL-2 and IFN-gamma) secretion by mitogen stimulated spleen cells. DHEA also suppressed the production of cytokines interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) by T helper 2 (Th2) cells which were otherwise stimulated by retrovirus infection. Thus, immune dysfunction and increased oxidation induced by murine retrovirus infection were largely prevented by DHEA.

Up-regulation of the ubiquitin-conjugating and proteolytic systems in murine acquired immunodeficiency syndrome

Lymphoproliferation, chronic B-cell activation resulting in hypergammaglobulinemia, and profound immunodeficiency are prominent features of retrovirus-induced murine acquired immunodeficiency syndrome (murine AIDS). Here we demonstrate that in murine AIDS the ATP-dependent and ubiquitin-dependent proteolytic system is strongly affected, at least in the lymph nodes of infected mice. Solid-phase immunochemical assays show that the ubiquitin-conjugate pools increase by about threefold 10 weeks after infection, then decline slightly 15 weeks after infection to a twofold increase. Accumulation of ubiquitin conjugates is accompanied by induction of the ubiquitin-conjugating pathway, involving several carrier-protein isozymes (E2), mainly 14-kDa E2 and 17-kDa E2. Furthermore, accumulation of ubiquitin conjugates and induction of the conjugating system are coincident with an increase in the proteolytic activity supported by the 26S proteolytic complex. However, 15 weeks after infection, when the conjugation rate and levels of ubiquitin conjugates decrease, proteasome activity returns to values similar to those of the control, suggesting that a higher proteosomal activity is no longer needed. The concerted induction of the ubiquitin-conjugating and proteolytic systems in murine AIDS apparently does not involve the breakdown of viral products nor is it supported by virus-coded events, but probably arises as a cellular response to viral infection.

Pentoxifylline decreases brain levels of platelet activating factor in murine AIDS

Tumor necrosis factor-alpha (TNF-alpha) and platelet-activating factor (PAF) have been implicated in the pathogenesis of human immunodeficiency virus (HIV)-associated encephalopathy. The effects of pentoxifylline on brain PAF levels were examined in mice infected with the LP-BM5 murine leukemia virus (MuLV). Seven weeks after viral inoculation, significant increases in serum TNF-alpha and brain PAF levels were observed. One week of treatment with pentoxifylline initiated 6 weeks postinfection significantly reduced both serum TNF-alpha and brain PAF levels. A significant positive correlation was observed between the levels of these substances (r = 0.62; P < 0.01). This study demonstrates that pentoxifylline treatment was effective in decreasing the levels of TNF-alpha in the serum and PAF levels in the brain of mice infected with the LP-BM5 MuLV.

Effect of selenium supplementation on mice infected with LP-BM5 MuLV, a murine AIDS model

LP-BM5 Murine leukemia virus (MuLV) infection of C57BL/6 mice develop a disease that has many features in common with human acquired immunodeficiency syndrome (AIDS), in particular abnormal lymphoproliferation and severe immunodeficiency. Thus, this MAIDS model may be useful for evaluation of potent antirival agents in vivo. Deficiency in antioxidant micronutrients such as selenium, zinc, and glutathione have been observed in AIDs and AIDS-related complex (ARC) patients. In the present study, the MAIDS model was used to evaluate immunological and oxidative effect of Se as sodium selenite. Results indicated that Se treatment 0.1 mg/kg/d (p.o.) inhibited splenomegaly and sera IgG elevation effectively. In addition to abnormal immunity, oxidative imbalance possibly existed in MAIDS model, as lipid peroxide increased significantly in spleen and whole blood glutathione peroxidase (GSH-Px) activity decreased markedly. Se supplementation had good protective effect.

Effect of hot water extract of Chlorella vulgaris on cytokine expression patterns in mice with murine acquired immunodeficiency syndrome after infection with Listeria monocytogenes

We have previously reported that oral administration of hot water extract of Chlorella vulgaris (CVE) enhances resistance to Listeria monocytogenes through augmentation of Listeria-specific cell-mediated immunity in normal mice and mice with murine acquired immunodeficiency syndrome (MAIDS) caused by murine leukemia virus (MuLV) LP-BM5. To elucidate the mechanisms whereby CVE augments the cell-mediated immunity, we examined the expression patterns of mRNA for cytokines in normal and MAIDS mice given CVE orally after L. monocytogenes infection. The expression levels of IL-1 alpha, IL-12, GM-CSF, MIP and TNF alpha genes were significantly augmented in the peritoneal adherent cells by oral administration of CVE for 2 weeks before Listeria infection. The expression levels of gamma IFN and IL-12 mRNA were significantly higher in the spleen after Listeria infection in CVE-treated mice than in normal mice, while the expression of IL-10 mRNA in the spleen was decreased by CVE administration. In MAIDS mice, oral administration of CVE also augmented the expression of gamma IFN and IL-12 mRNA in the spleen after Listeria infection, while it rather reduced the expression of IL-10 mRNA. These results suggest that CVE may preferentially augment THI responses against Listeria via activation of macrophages to produce IL-12 and enhance host defence against Listeria infection both in normal and MAIDS mice.

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

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 IFN gamma + 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.

TCR triggering of anergic CD4 T cells in murine AIDS induces apoptosis rather than cytokine synthesis and proliferation

Murine AIDS (MAIDS) induced by infection of C57BL/6 mice with a mixture of retroviruses known as LP-BM5 is characterized by lymphadenopathy, splenomegaly, and T and B cell dysfunction. By labeling with bromodeoxyuridine in vivo, we found vigorous CD4 T cell proliferation during the initial stages of infection, yet a loss in their ability to function both in vivo and in vitro. In addition, a significant fraction of the CD4 T cell population in infected mice undergoes spontaneous apoptosis in vivo. Upon in vitro stimulation with anti-CD3 plus PMA, anergic CD4 T cells from mice with MAIDS fail to progress through the cell cycle (G0/G1 arrest), and a fraction of the cells undergoes apoptosis. The addition of IL-2 along with TCR-mediated stimulation not only fails to rescue CD4 T cells from apoptosis, but enhances activation-induced cell death. To further understand the regulation of the suicide pathway(s) of anergic CD4 T cells vs the cytokine synthesis pathway(s) of normal CD4 T cells, we evaluated their expression of Bcl-2 protein. As infection progresses, the expression of Bcl-2 among CD4 T cells declines and drops further when CD4 T cells are restimulated through the TCR in vitro. These results suggest that this CD4 T cell immunodeficiency in MAIDS includes a TCR-induced program of activation-induced cell death and an uncoupling from cytokine synthesis pathways and proliferation of CD4 T cells. The decline in Bcl-2 expression may be in part responsible for this reprogramming.

Vitamin E deficiency and immune dysfunction in retrovirus-infected C57BL/6 mice are prevented by T-cell receptor peptide treatment

Female C57BL/6 mice were infected with LP-BM5 retrovirus, causing murine acquired immunodeficiency syndrome (AIDS), which is functionally similar to human AIDS. Retrovirus infection inhibited release of T-helper 1 cytokines, stimulated secretion of T-helper 2 cytokines and induced hepatic and cardiac vitamin E deficiency with increased lipid peroxides. We hypothesized that the immune dysfunction caused increased oxidation and loss of vitamin E. Because T-cell receptor (TCR) peptide treatment blocked the excessive stimulation of a T-cell subset by retroviral superantigens, we tested whether maintenance of normal immune function during infection prevented excessive oxidative damage. The TCR peptide treatments with doses > 100 microgram/mouse and administered 2-4 wk postinfection significantly inhibited the retrovirus-induced immune dysfunction, concomitantly reduced tissue oxidative damage and thereby largely maintained vitamin E concentration in the liver and heart. Reducing the dose of peptide or delaying administration until early murine AIDS had developed resulted in severe immune dysfunction that caused elevated tissue lipid peroxidation and loss of vitamin E. The TCR peptide treatment partially maintained production of interleukin-2 (IL-2) and prevented retrovirus-induced elevated production of IL-6 by splenocytes in vitro. In conclusion, TCR peptide treatment during murine retrovirus infection ameliorated immune dysfunction and thus prevented increases in tissue lipid peroxidation and vitamin E loss. T-cell immune dysfunction and its prevention by TCR peptide treatment is important in the therapy of vitamin E deficiency induced by retrovirus infection.

Curative effect of split low dosage total-body irradiation on murine AIDS induced by Friend virus: the results and the possible mechanism

Mice infected with Friend Leukemia Virus (FLV) rapidly develop erythroleukemia and severe immune deficiency which resembles human AIDS. We have reported that mice infected with a lethal dose of FLV can be 100% cured by 150 cGy total body irradiation (TBI). This curative effect was associated with restoration of cellular immunity which was compromised by the virus. This restoration may result from activation of the IFN-gamma system and IL-2 production. Our research work further demonstrated that no spleen focus-forming virus (SFFV) specific mRNAs, no 6.0kb SFFV fragments and SFFV envelope glycoproteins were detectable in FLV-infected mice treated with low dose TBI. Predicated on our report, del Regato has initiated clinical trials to treat AIDS patients with low dose TBI. The preliminary results are encouraging and the study is continuing. We have also studied the effects of low dose TBI on the expression of the P53 gene. The results show loss or inactivation of P53 tumor suppressor genes in FLV-infected mice, but P53 expression was restored in FLV-infected mice treated by low dose TBI. It is intriguing to speculate that in the curative effect of low dose TBI on mice infected with retrovirus, the P53 tumor suppressor gene may play an important role. It would be of interest to see if this type of treatment, which was well tolerated by mice, would be beneficial in other types of virally induced disease, including AIDS.

Localization of quinolinic acid in the murine AIDS model of retrovirus-induced immunodeficiency: implications for neurotoxicity and dendritic cell immunopathogenesis

OBJECTIVE AND DESIGN

Using murine AIDS (MAIDS) as a model of retrovirus-induced immunodeficiency, the aims of this study were (1) to determine the cellular source(s) of quinolinic acid (Quin) with regard to its significance as a potential neuroexcitotoxin in AIDS dementia complex, and (2) to characterize the relationship between dendritic cell Quin immunoreactivity and the histopathological changes associated with the progression of disease.

METHODS

Mice with MAIDS were sacrificed from 1 to 16 weeks post-infection. Temporal and spatial changes in the in vivo distribution of Quin at the cellular level were determined by carbodiimide-based immunohistochemical methods.

RESULTS

Cellular Quin immunoreactivity was chronically elevated in lymphoid tissues of mice with MAIDS. In contrast, no cellular Quin immunoreactivity was visible in the brain parenchyma at any timepoint studied.

CONCLUSION

These findings are consistent with the view that select immune cells in the peripheral lymphoid tissues may be the primary source of Quin, which may contribute to neurotoxic complications in retrovirus-induced immunodeficiency syndromes. The predominant Quin immunoreactive cell types changed with the progression of disease. A significant finding was the marked increase in the number of Quin immunoreactive dendritic cells in the early phase of MAIDS, suggesting a relationship between dendritic cells and Quin in retroviral infection.

Liver endogenous antioxidant defenses in mice fed AIN-76A diet and infected with murine AIDS

The effects of murine AIDS infection on endogenous antioxidant defenses in mice fed the AIN-76A liquid diet were investigated. C57BL/6 female mice were divided into 2 groups: one group was injected interperitoneally with LP-BM5 murine retrovirus (MAIDS) stock, and the other group served as the non-infected control. Two weeks after the infection, the mice were killed and livers were excised for biochemical analysis of the antioxidant defenses. Liver reduced glutathione (GSH) levels and activities of both cytosolic superoxide dismutase (SOD) and mitochondrial SOD were significantly depressed by MAIDS infection. Activities of glutathione reductase (GR) selenium (Se)-dependent glutathione peroxidase (GPx), catalase and glutathione-S-transferase (GST) toward 1-chloro-2,4-dinitrobenzene (CDNB) were not affected by MAIDS infection. A previous study by this laboratory using the Lieber-DeCarli (L-D) all purpose liquid diet caused a decline in total SOD activity and GPx activity, but not GSH levels. The results suggest that MAIDS infection depresses liver antioxidant defenses; however, MAIDS infection of mice fed the AID-76A liquid diet depresses different liver antioxidant defense parameters when compared to those of the mice fed the L-D all purpose liquid diet.

Quinolinic acid levels in a murine retrovirus-induced immunodeficiency syndrome

Mice infected with the retrovirus mixture designated LP-BM5 murine leukemia virus (MuLV) develop an immunosuppressive disease. Quinolinic acid (QUIN) is an endogenous neurotoxic N-methyl-D-aspartate agonist that may contribute to the pathogenesis of HIV-associated neurologic disease. In the present study, the levels of QUIN in brain and blood were measured in mice infected with LP-BM5 MuLV and compared with those in uninfected mice and mice infected with the nonpathogenic strain of ecotropic MuLV (helper component of LP-BM5 MuLV). Infection with LP-BM5 MuLV resulted in progressive increases in blood QUIN levels beginning 2 weeks after inoculation that peaked by 16 weeks postinfection. QUIN levels were also increased in cerebral cortex, hippocampus, and striatum. In systemic tissues, QUIN levels were increased in lung, liver, and spleen. In contrast, infection with the ecotropic viral component of the LP-BM5 MuLV mixture was not associated with any changes in brain, blood, or systemic tissue QUIN levels, even though helper virus burdens were comparable to those in mice infected with LP-BM5 MuLV. Treatment of LP-BM5 MuLV-infected mice with the antiretroviral agent zidovudine (azidothymidine) significantly reduced blood and brain QUIN levels in association with reductions in viral load in brain and spleen. These observations suggest that elevated QUIN production is not attributable to productive infection with retrovirus per se but occurs in response to an agent or agents, such as cytokines, that are produced by the host in response to virus infection.

Increased brain levels of platelet-activating factor in a murine acquired immune deficiency syndrome are NMDA receptor-mediated

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 results 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.

Apoptotic death of lymphocytes in murine acquired immunodeficiency syndrome: involvement of Fas-Fas ligand interaction

Murine acquired immunodeficiency syndrome (MAIDS) is caused by a defective murine leukemia virus. The disease is characterized by abnormal lymphoproliferation, impaired T and B cell function and aberrant regulation of cytokines. Both T and B lymphocytes show activated phenotypes, but undergo apoptotic death with characteristic DNA fragmentation. These results indicate the presence of a continuous activation death pathway of the lymphocytes in MAIDS. Overexpression of the bcl-2 transgene in lymphocytes showed no effect on the apoptotic cell death or on the development of the disease. In contrast, mice carrying mutations in either Fas or Fas ligand exhibited accelerated progression of the disease upon infection with MAIDS virus. These results suggest the involvement of Fas-Fas ligand system in the pathogenesis of MAIDS.

Effect of antiviral treatments on the bone marrow in murine aids

Blood cytopenia is a common feature in HIV infection, occurring in up to 70% of patients with AIDS. Since at present it is not clear to what extent this is intrinsic to HIV infection or due to opportunistic infections and antiretroviral agents we have investigated the long-term effects of conventional and new antiviral drugs on the bone marrow of normal and immunodeficient mice. The results show that azidothymidine (AZT), dideoxycytidine (DDC) and dideoxycytidine 5'-triphosphate (DDCTP) alone or in combination are all effective in inhibiting the expression of the retroviral protein Pr60gag in bone marrow cells. However, DDCTP was the most effective in preventing bone marrow cytopenia. Combined treatments of AZT plus DDCTP result in a reduction in erythroid precursors compared to that resulting from DDCTP administration, while DDC plus DDCTP results in a differential cell count similar to that found in uninfected mice. Thus, the bone marrow in murine AIDS may prove useful as a model for therapy of retroviral infections and for treating blood cytopenias.

Impaired cytokine production by bone marrow stromal cells of immunodeficient mice

The aetiology of the bone marrow suppression in HIV-infected patients is unknown. We have demonstrated previously that the ability of bone marrow cells, derived from mice made immunodeficient by infection with the retrovirus LP-BM5, to establish long-term stromal cultures is impaired. In this study we determined the ability of bone marrow stromal cells from these immunodeficient mice to produce cytokines important in haemopoiesis. Neither SCF, IL-3, GM-CSF nor TNF alpha were found in conditioned media of long-term bone marrow cultures (LTBMC) of normal or MAIDS mice. We failed to detect mRNA for TNF or IL-1 alpha, by reverse transcription polymerase chain reaction (RT-PCR), in cultures derived from either normal or immunodeficient mice. Steady-state levels of transcripts for IL-6 were equal in cells from normal and MAIDS mice. Steady-state levels of mRNA for TGF beta 1, a known inhibitor of haemopoiesis, were decreased in cultures derived from MAIDS mice at late stages of infection. The mRNA level of the multipotent haemopoietic regulator stem cell factor was also decreased in MAIDS cultures as compared with normals. Transcripts encoding the transmembrane form of the growth factor were almost absent. Addition of soluble GM-CSF and SCF only transiently increased the production of CFUs (BFUE and CFU-G/M) in MAIDS LTBMC. These findings suggest that derangements in cytokine production in stromal cells of immunodeficient mice may contribute to the suppression of haemopoiesis observed in this disease. One mechanism of HIV-induced depression of haemopoiesis may be via alterations of the haemopoietic microenvironment.

Up-regulation of T helper 2 and down-regulation of T helper 1 cytokines during murine retrovirus-induced immunodeficiency syndrome enhances susceptibility of a resistant mouse strain to Leishmania amazonensis

Resistance to and recovery from leishmania infection is dependent on cell-mediated immunity. C57BL/6 mice are resistant to Leishmania amazonensis (La) infection but susceptible to LP-BM5 murine leukemia virus (MuLV) infection. MuLV infection leads to a state of immunodeficiency characterized by severe compromise of cell-mediated immunity. When infected with La alone, C57BL/6 mice developed a small transient lesion that evolved to spontaneous healing or a lesion with extremely slow growth. Lesions were predominantly comprised of a lympho-macrophagic infiltrate with few parasitized macrophages. When infected with La and, 4 weeks later, with MuLV (La-MuLV), the mice developed a large uncontrolled nonhealing lesion containing vacuolated and heavily parasitized macrophages. In contrast, mice infected with MuLV first and La 4 weeks later (MuLV-La) developed a small but persistent lesion, characterized histologically by a small number of heavily parasitized macrophages and few lymphocytes. Eight weeks after MuLV infection, both had similar immunological profiles with decreased lymphocyte proliferation, diminished production of interferon-gamma, and high production of interleukins 4 and 10. At the time of L. amazonensis infection, La-MuLV animals have a normal T cell function whereas in MuLV-La mice this function is already impaired; this may influence the recruitment of macrophages to the site of leishmania injection.

Mutational analysis of the murine AIDS-defective viral genome reveals a high reversion rate in vivo and a requirement for an intact Pr60gag protein for efficient induction of disease

Pr60gag appears to be the only protein encoded by the murine AIDS (MAIDS)-defective virus. To study the role of Pr60gag or some other sequences of the viral genome in the pathogenicity of the virus, we have generated mutants of the defective viral genome. These mutant defective viruses, prepared as helper-free stocks, were inoculated into susceptible C57BL/6 mice. Mutant Du5H-A virus, which had a stop codon within gag MA(p15), did not induce target cell proliferation or MAIDS. Mutants Du5H-B and -C encoded truncated Pr60gag proteins containing, respectively, MA(p15)-p12 or MA(p15)-p12 and part of CA(p30). These mutants showed a very limited capacity to induce early cell expansion and were poorly pathogenic. Only recombinant (revertant) viruses were recovered from organs of diseased mice inoculated with these two mutants. Mutant Du5H-D was generated by deleting 1.4 kbp of the 3'-end sequences, outside the gag coding region. The levels of RNA and proteins made by this mutant were low. This mutant also reverting frequently but was nevertheless able to induce MAIDS at a low efficiency without reverting. Our results indicate that the Pr60gag protein is necessary and sufficient to induce MAIDS. These data also suggest that the Pr60gag protein needs to be relatively intact to be fully pathogenic. In addition, our study shows a very high reversion rate of some mutants and emphasizes the need to check for the presence of revertant (recombinant) viruses in diseased organs when working with mutants of the MAIDS-defective virus.

Chronic ethanol consumption prior to retrovirus infection alters cytokine production by thymocytes during murine AIDS

Chronic ethanol (EtOH) consumption may be a cofactor in the development of acquired immune deficiency syndrome (AIDS). As the thymus is an unique site for T cell maturation, we investigated whether thymocytes from EtOH consuming mice were more predisposed to aberrant cytokine production due to retrovirus infection. Adult female C57BL/6 mice were fed 4.5% (v/v) in liquid diet or control liquid diet without EtOH for 10 weeks. All diets contained nutrients at only the recommended daily intake level for mice. Then all mice were infected LP-BM5 retrovirus and were fed control liquid diets without EtOH. The body and thymus weights were not affected by EtOH consumption. However, thymocyte number and proliferation, which had been reduced during murine AIDS, were significantly further reduced by EtOH use. The production of IL-2 and IL-6 by thymocytes, which was lessened during retrovirus infection, were significantly further suppressed by dietary EtOH at 6 weeks postinfection, whereas levels of IL-4 and IFN-gamma by thymocytes, which were elevated during retrovirus infection, were significantly and slightly further increased by EtOH-treated mice prior to retrovirus infection, respectively. These data suggest that dietary EtOH consumption can modulate cytokine production by thymocytes, adversely affecting T cell differentiation, especially during retrovirus infection. These results provide additional evidence that EtOH consumption should be a cofactor during development of AIDS via producing altered cytokine production and then disrupting T cell differentiation.

Alterations of hepatic drug metabolism in mice following infection with the murine retrovirus LP-BM5

Infection of mice with the murine retrovirus mixture LP-BM5 caused a retroviral infection with many similarities to human HIV infection. We have reported alterations in hepatic drug metabolism which progressed during the course of this infection. Hexobarbital-induced sleep time increased 1.5-2.2-fold above uninfected controls after 10 to 19 weeks post infection. Inhibition of spectral cytochrome P-450 levels by 25 to 30% was observed between 15 and 17 weeks post-infection, and there were changes in specific microsomal enzyme activities. The microsomal cocaine demethylase activity was reduced by 40%, whereas cytosolic enzyme activities were increased by 1.5-2.0-fold. These alterations may contribute to the altered metabolism of drugs of abuse reported in MAIDS mice. The mechanism for these alterations is not known, although the effects correspond temporally to reported infiltration of the liver with immunoblasts and plasma cells. This suggests a role for the immune system or for mediators released by cells of the immune system which could account for these observations. An understanding of the effects of infection on drug metabolism is important because of their impact on the efficacy and safety of drugs for use in AIDS patients).

Impaired calcium mobilization in CD4+ and CD8+ T cells in a retrovirus-induced immunodeficiency syndrome, murine AIDS

After infection with LP-BM5 murine leukemia viruses, susceptible strains of mice develop a severe and progressive immunodeficiency disease, termed murine AIDS (MAIDS), features of which include markedly impaired T cell response to mitogens or specific Ag stimulation and decreased production of IL-2. Since an elevation of intracellular calcium concentration resulting from binding of Ag to the TCR is associated with IL-2 production, T cells from mice either uninfected or infected with LP-BM5 murine leukemia viruses were examined by a calcium mobilization assay. Both CD4+ and CD8+ T cells from infected mice manifested impaired calcium mobilization responses upon in vitro stimulation with anti-CD3 mAb or Con A. The abnormalities appeared early after virus inoculation and showed no difference in time course between subsets of T cells. Frequencies of prestimulation calcium-positive cells among both CD4+ and CD8+ cells in mice with MAIDS were significantly higher than those for uninfected mice. These abnormalities were associated with presence of the MAIDS-inducing defective virus genome, but were not induced by infection of mice genetically resistant to development of MAIDS or with nonpathogenic helper murine leukemia virus, a virus component that induces high spontaneous proliferation of T cells, even in MAIDS-resistant mice.

Potential of diet therapy on murine AIDS

Recently, a murine retrovirus (LpBM5 MuLV), which induces immunodeficiency syndrome in mice, termed MAIDS, has been found to have several features similar to those seen in human acquired immunodeficiency syndrome (AIDS). The present study was undertaken to compare the effects of 40% energy restriction (R) and/or ad libitum (AL) diets with vegetable [corn oil, (CO) (n-6)] or marine oil [menhaden fish oil (FO), (n-3)] as a source of dietary fats on the immune function and survival rate of C57BL/6 mice injected with the LpBM5 MuLV virus. Weanling mice were fed, throughout the study, either a 5% CO-, 5% CO(R)-, 20% CO- or 20% FO-based diet and 8 wk later the mice were injected with the LpBM5 MuLV (5 x 10(5) plaque-forming units). The results revealed a significantly prolonged postinjected survival rate in the mice fed 20% FO and 5% CO(R) diets [5% CO = 131 +/- 7 d; 5% CO(R) = 161 +/- 13 d; 20% CO = 125 +/- 6 d; 20% FO = 164 +/- 14 d]. Immunological studies conducted 4 wk after injection revealed decline in both interleukin-2 production and proliferative response to mitogens in spleen cells of mice in all four dietary groups. However, this decline was less apparent in mice fed 5% CO(R) and 20% FO diets.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in hepatic lipid composition after infection by LP-BM5 murine leukemia virus causing murine AIDS

The severe hepatic disorders in patients with acquired immune deficiency syndrome (AIDS) is often attributed to a variety of other factors which could affect hepatic function. To evaluate the mechanism of liver damage in murine AIDS-induced immune-suppressed animal, a murine model of AIDS (MAIDS), caused by infection with LP-BM5 murine leukemia virus was used at a late stage of the disease. Retroviral infection significantly increased hepatic cholesterol, triacylgycerol and the cholesterol/phospholipid ratio. Similarly, the proportions of palmitic, palmitoleic, linoleic, ratios of linoleic to arachidonic and saturated to unsaturated fatty acids were significantly lower while the proportion of oleic, docosatetraenoic and docosahexenoic fatty acids were significantly increased in the retrovirus infected mice. Hepatic dysfunction as evidence by increased serum transaminase levels were also observed in the retrovirus infected animals. The data suggest that the liver damage in murine AIDS is induced by retroviral infection and the desaturase enzymes system necessary to maintain regular balance of the fatty acids in the cells may be affected during retroviral infection.

Modulation of tumor necrosis factor and gamma interferon production by cocaine and morphine in aging mice infected with LP-BM5, a murine retrovirus

The actions of retroviral infections, aging, and cocaine and morphine injection on cytokine production were investigated in C57BL/6 female mice. Retroviral infection with LP-BM5 murine leukemia virus was further developed as a model of murine acquired immunodeficiency syndrome (AIDS). The effects of cocaine and morphine on gamma-interferon (IFN) and tumor necrosis factor (TNF) production in vivo and with isolated spleen cells were measured by a sandwich enzyme-linked immunosorbent assay (ELISA) method. Serum IFN was generally not detected in any group except mice injected with saline and young mice infected with LP-BM5 virus. Splenocytes from mice with murine AIDS produced less IFN when stimulated in vitro by ConA. In aged mice, IFN production by spleen cells was severely suppressed by retroviral infection. Cocaine had a tendency to suppress IFN production by stimulated cells in vitro. Morphine tended to reduce IFN production by spleen cells from retrovirally infected animals. The serum TNF level in mice with murine AIDS was elevated creating higher levels in morphine and morphine plus cocaine treated uninfected mice while cocaine injection eliminated serum TNF. When stimulated in vitro by lipopolysaccharides (LPS), splenocytes from mice with murine AIDS also produced more TNF than uninfected controls. TNF production in vitro and in vivo was significantly increased by retroviral infection. Therefore, results indicate that cocaine and retroviral infection modulate TNF and IFN production.