Changes in lipid composition of human peripheral blood lymphocytes infected by HIV

Carnitine in Human Immunodeficiency Virus Type 1 Infection/Acquired Immune Deficiency Syndrome

There is an increasing body of evidence that subgroups of patients infected with human immunodeficiency virus type 1 possess carnitine deficiency. Secondary carnitine deficiencies in these individuals may result from nutritional deficiencies, gastrointestinal disturbances, renal losses, or shifts in metabolic pathways. However, tissue depletion precipitated by drug toxicities, particularly zidovudine, is a major etiology and concern. Carnitine deficiency may impact on energy and lipid metabolism, causing mitochondrial and immune dysfunction. There are convincing laboratory data showing the in vitro ameliorative effects of L-carnitine supplementation on zidovudine-induced myopathies and lymphocyte function. Studies measuring the impact of L-carnitine supplementation on clinical characteristics are ongoing. (J Child Neurol 1995; 10(Suppl):2540-2544).

Inhibition of human immunodeficiency virus type-1 (HIV-1) glycoprotein-mediated cell-cell fusion by immunor (IM28)

Background

Immunor (IM28), an analog of dehydroepiandrosterone (DHEA), inhibits human immunodeficiency virus type-1 (HIV-1) by inhibiting reverse transcriptase. We assessed the ability of IM28 to inhibit the cell-cell fusion mediated by HIV envelope glycoprotein in an in vitro system. For this purpose, we co-cultured TF228.1.16, a T-cell line expressing stably HIV-1 glycoprotein envelopes, with an equal number of 293/CD4+, another T cell line expressing CD4, and with the SupT1 cell line with or without IM28.

Results

In the absence of IM28, TF228.1.16 fused with 293/CD4+, inducing numerous large syncytia. Syncytia appeared more rapidly when TF228.1.16 was co-cultured with SupT1 cells than when it was co-cultured with the 293/CD4+ cell line. IM28 (1.6 – 45 μg/ml) completely inhibits cell-cell fusion. IM28 also prevented the development of new syncytia in infected cells and protected naive SupT1 cells from HIV-1 infection. Evaluation of 50% inhibitory dose (IC50) of IM28 revealed a decrease in HIV-1 replication with an IC50 of 22 mM and 50% cytotoxicity dose (CC50) as determined on MT2 cells was 75 mM giving a selectivity index of 3.4

Conclusions

These findings suggest that IM28 exerts an inhibitory action on the env proteins that mediate cell-cell fusion between infected and healthy cells. They also suggest that IM28 interferes with biochemical processes to stop the progression of existing syncytia. This property may lead to the development of a new class of therapeutic drug.

Hepatitis B virus enhances transduction of human hepatocytes by SV40-based vectors

BACKGROUND/AIMS

Chronic HBV infection, a world-wide epidemic, can lead to chronic hepatitis and eventually to cirrhosis and hepatocellular carcinoma. The liver poses obstacles for many available gene-transfer vectors. SV40-based vectors can transduce human hepatic and hematopoietic cells. We studied the effect of HBV on the transduction - efficiency of human hepatic cells by SV40 - based vectors.

METHODS

A SV40-vector carrying the luciferase gene, and wild-type SV40, were used to assess transduction efficiency of human HBV-positive and HBV-negative hepatic cells. Transduction efficiency was measured as luciferase activity or by T-antigen staining. To evaluate whether differences in transduction efficiency are due to cell recognition and/or nuclear transport, MHC-I receptors were measured by FACS analysis and SV40-DNA was extracted from the nuclei of transduced cells and quantified.

RESULTS

Two HBV-positive cell-lines, HepG2.2.2.15 and FLC4-A10II, were transduced significantly more efficiently than their parental HBV-negative cell-lines. Transient transfection of HuH-7 cells with the HBV genome also increased transduction efficiency. The level of MHC-I, the cellular receptor for SV40, was comparable in all the cell-lines studied. However, soon after infection with SV40, the nuclei of HepG2.2.2.15 contained >6-fold more SV40-DNA than HepG2.

CONCLUSIONS

HBV increases transduction by SV40-vectors. This is due to enhanced vector entry and/or transport into the nucleus. SV40-vectors appear to have a potential for gene therapy for the treatment of HBV infections.

Singlet oxygen (1O2)-oxidazable lipids in the HIV membrane, new targets for AIDS therapy?

Human immunodeficiency virus (HIV) is a lipid enveloped virus. The lipid envelope differs significantly from the lipid membrane of normal human cells: it contains high amounts of cholesterol, that is of importance for the virus-cell interaction (for entry and exit of the virus) at so-called lipid rafts. Cholesterol, as a R-C=C-R compound possesses an oxidazable carbenic bond. The present work suggests the inactivation of HIV by oxidation of viral cholesterol and/or unsaturated fatty acids. For oxidation, the relatively mild oxidant singlet oxygen (1O(2)) might be used. 1O(2) is generated by redoxcyclers (e.g., of the quinone type, such as vitamin K) or by chloramines (e.g., taurine-chloramine). At the 1O(2) concentrations necessary to inactivate lipid enveloped virus in human blood the oxidation-sensible critical hemostasis parameters such as thrombocytes and fibrinogen are only partly inactivated. Therefore, it is proposed to consider generators of 1O(2) as a new form of AIDS therapy.

Virion-associated cholesterol is critical for the maintenance of HIV-1 structure and infectivity

OBJECTIVE

HIV-1 particles are enriched with cholesterol; however, the significance of this cholesterol enrichment is unknown. This study examines the structural and functional roles of cholesterol in HIV-1 replication.

METHODS

Using methyl-beta-cyclodextrin (CD) to remove cholesterol from the HIV-1 envelope, buoyant density and infectivity of the cholesterol-deficient HIV-1 particles were compared with the untreated control. The specificity and requirement of cholesterol as an HIV-1-associated lipid were investigated by replenishing cholesterol-deficient HIV-1 with cholesterol, cholestenone (a cholesterol structural analogue) or sphingomyelin (a structurally unrelated yet virion-associated lipid).

RESULTS

CD-mediated removal of virion cholesterol increased the buoyant density of virion particles and reduced HIV-1 infectivity. Trans-supplementation of exogenous cholesterol rescued the defects associated with CD-induced cholesterol depletion in HIV-1. However, the restoration of viral infectivity could not be achieved by trans-supplementation of either cholestenone or sphingomyelin.

CONCLUSION

This study provides the first direct evidence that HIV-1-associated cholesterol is important for the maintenance of virion structure and infectivity. While the buoyant density of cholesterol-defective HIV-1 can be restored by a cholesterol structural analogue, cholestenone, the requirement for cholesterol is essential for HIV-1 infectivity.

Lipid rafts and HIV-1: from viral entry to assembly of progeny virions

BACKGROUND

Lipid rafts are currently an intensely investigated topic of cell biology. In addition to a demonstrated role in signal transduction of the host cell, lipid rafts serve as entry and exit sites for microbial pathogens and toxins, such as FimH-expressing enterobacteria, influenza virus, measles virus and cholera toxin. Furthermore, caveolae, a specialised form of lipid raft, are required for the conversion of the non-pathogenic prion protein to the pathogenic scrapie isoform.

OBJECTIVES

A number of reports have shown, directly or indirectly, that lipid rafts are important at various stages of the human immunodeficiency virus type-1 (HIV-1) replication cycle. The purpose of this paper is to provide a brief overview of the role of membrane-associated lipid rafts in cell biology, and to evaluate how HIV-1 has hijacked this cellular component to support HIV-1 replication. Special sections are devoted to discussing the role of lipid rafts in (1) the entry of HIV-1, (2) signal transduction regulation in HIV-1-infected cells, (3) the trafficking of HIV-1 proteins via lipid rafts during HIV-1 assembly; and a further section discusses the role of cholesterol in mature HIV-1.

SUMMARY

Like a number of other pathogens, HIV-1 has evolved to rely on the host cell lipid rafts to support its propagation during multiple stages of the HIV-1 replication cycle. This review has highlighted the importance of lipid rafts in HIV-1 replication.

Overexpression of lymphocytic GD3 ganglioside and presence of anti-GD3 antibodies in patients with HIV infection

This study was undertaken to analyze the role of disialoganglioside GD3 in HIV infection and disease progression. We report here the results obtained by both ex vivo and in vitro experiments on (1) surface and cytoplasmic expression and distribution of GD3 in HIV-infected cells, (2) the presence of anti-GD3 antibodies in sera of patients with HIV infection in various stages of the disease, and (3) the association of GD3 expression with HIV-related apoptotic events. GD3 expression was determined by high-performance thin-layer chromatography (HPTLC) and lipid-bound sialic acid and by static and flow cytometric analyses in peripheral blood lymphocytes from 22 AIDS patients, 20 anti-HIV Ab(+) asymptomatic subjects, and 25 healthy donors. Results obtained clearly indicated a significantly higher expression of plasma membrane GD3 content in lymphocytes from HIV-infected patients with respect to healthy controls. These HIV-induced perturbations of glycosphingolipid metabolism could be detected in all stages of the disease, including asymptomatic individuals. In addition, a significant percentage of patients showing disease progression displayed in serum samples an increased presence of anti-GD3 antibodies. Interestingly, ex vivo studies of lymphocytes from patients with HIV infection also indicated that GD3 expression is strictly associated with annexin V binding, an early marker of apoptosis. Moreover, cytofluorimetric analysis showed that virtually all anti-p24 Ab-positive cells were also immunolabeled with anti-GD3 antibodies. Accordingly, in vitro studies showed a significant redistribution and increase in GD3 expression in cultured U937 cells chronically infected with HIV-1 with respect to uninfected counterparts. In conclusion, our data clearly indicate that a significant increase in GD3 content in HIV-infected lymphocytes can occur and that this GD3 overexpression is paralleled by the presence of anti-GD3 antibodies in the plasma of patients. This is the first demonstration that disialoganglioside GD3, independent of the therapeutic schedule employed, can be considered as one of the early markers of HIV infection and can contribute to the early events leading to T cell depletion by apoptosis.

Oxysterols, but not cholesterol, inhibit human immunodeficiency virus replication in vitro

Oxysterols, oxygenated derivatives of cholesterol selected for their cytostatic activity and their inhibitory effect on cholesterol synthesis, have been investigated for their anti-human immunodeficiency virus (HIV) activity in vitro. The three oxysterols tested, 7 beta-hydroxycholesterol (7 beta-OHC), 25-hydroxycholesterol (25-OHC) and 7 beta, 25-dihydroxycholesterol (7,25-OHC), inhibit viral replication at micromolar concentrations. The selectivity indexes for 7 beta-OHC and 25-OHC are quite modest (2 to 8) but reproducible; the dihydroxycholesterol 7,25-OHC exhibited antiviral properties at concentrations 13- to 25-fold lower than the highest concentration tested at which no toxicity was measurable. Oxysterols are naturally occurring compounds, and we speculate on their physiological relevance in HIV-infected individuals.

HIV-1-induced perturbations of glycosphingolipid metabolism are cell-specific and can be detected at early stages of HIV-1 infection

The metabolism of glycosphingolipids (GSL) has been investigated in peripheral blood mononuclear cells (PBMC) from 8 patients at an early stage of HIV-1 infection. Following metabolic labeling of these cells with [14C]galactose, the GSL were purified and the radioactivity incorporated into each individual GSL quantitated by phosphoimaging. Compared with PBMC from seronegative donors, the GSL metabolism in PBMC from HIV-1-infected individuals was characterized by an increased synthesis of two GSL: the B-lymphocyte differentiation antigen globotriaosylceramide (Gb3, also referred to as CD77), and the monosialoganglioside GM3, a marker of T-lymphocytes and macrophages. The accumulation of Gb3 and GM3 in PBMC from HIV-1-infected patients was associated with the appearance of anti-Gb3 and anti-GM3 antibodies. Because these GSL are involved in the control of cell proliferation and signal transduction, such anti-GSL autoantibodies may contribute to the immune suppression during the course of HIV-1 infection. Studies on purified cell populations showed that GM3 accumulation occurred preferentially in HIV-1-infected monocytes/macrophages, whereas the synthesis glucosylceramide, the common precursor of complex GSL, was enhanced in both macrophages and CD4+ lymphocytes. Taken together, our data suggest that the dysregulation of GSL metabolism is an early event of HIV-1 pathogenesis that can induce important effects on immune cells homeostasis.

Restoration of immune response by a cationic amphiphilic drug (AY 9944) in vitro: a new approach To chemotherapy against human immunodeficiency virus type 1

AY 9944 [AY; trans-1,4-bis(chlorobenzylaminomethyl)-cyclohexane dihydrochloride], an inhibitor of sterol synthesis, was found to help restore the normal mitogenic responses and cytokine profiles of peripheral mononuclear cells (PBMCs) from AIDS patients in vitro. Compared to untreated cells, the human immunodeficiency virus type 1 (HIV-1)-infected PBMCs precultured in the presence of AY exhibited a normal rate of either mitogen-induced or recall- and superantigen-induced proliferation. After 2 weeks in the presence of the drug, the percentage of dead CD4(+) cells in HIV-1-infected cultures was comparable to that observed in uninfected cultures, while over the same time interval it increased by three- to fivefold in HIV-1-infected cultures maintained in the absence of AY. AY also stimulated by 2- to 12-fold interleukin-12 (IL-12) and (gamma interferon production. For IL-12, this effect appears to be related to an increase in corresponding IL-12 p35 and IL-12 p40 mRNA levels. Moreover, AY restored the expression of the IL-2 receptor, which was severely impaired in HIV-1-infected PBMCs. Although the drug has no direct antiviral effect (it does not significantly inhibit reverse transcriptase activity measured in vitro), it might be considered a potential therapeutic agent for HIV-infected patients, in that it may correct viral infection-related immune system defects by indirectly enhancing the level of resistance to HIV and opportunistic infections.

CD4/GP120mac251 interaction induces phospholipase A2 (PLA2) activation in cynomolgus monkey lymphocytes

Cynomolgus monkey are susceptible to infection with select simian immunodeficiency virus (SIV). We investigated the early interactions between SIV envelope glycoproteins (gp120mac251) and macaque lymphocytes. Our results demonstrate that the soluble viral glycoprotein induce a specific phospholipase A2 (PLA2) activation in lymphocytes through CD4. This PLA2 activation, induced after envelope glycoprotein-CD4 interaction, because of its locally destabilizing membrane effect, may have important implications for preparing the lymphocyte membrane for fusion with the viral particle. However, this effect is not sufficient to accomplish fusion. These data indicate that the specific step of fusion may be downstream from PLA2 activation.

HIV and SIV envelope glycoproteins induce phospholipase A2 activation in human and macaque lymphocytes

We investigated the early interactions between HIV-1, HIV-2, and simian immunodeficiency virus (SIV) envelope glycoproteins gp120(IIIB), gp105(ROD), and gp120(mac251), and human and macaque cells of the lymphocytic series. Our results demonstrate that the soluble viral glycoproteins induce a specific phospholipase A2 (PLA2) activation in lymphocytes through CD4. This PLA2 activation was induced after envelope glycoprotein-CD4 interaction and, because of its local membrane-destabilizing effect, may have important implications for preparing the lymphocyte membrane for fusion with the viral particle. However, this effect is not sufficient to accomplish fusion. These data indicate that the specific step of fusion may be downstream from PLA2 activation.

Overexpression of monosialoganglioside GM3 on lymphocyte plasma membrane in patients with HIV infection

SUMMARY

This study was undertaken to analyze both the GM3 expression on peripheral blood lymphocytes of HIV-infected patients and the relationship between ganglioside content and anti-GM3 reactivity. GM3 expression was determined as a percentage of lipid-bound sialic acid and by cytofluorimetric analysis in 25 AIDS patients, 20 anti-HIV+ asymptomatic subjects, 25 patients with different viral disease, and 25 healthy donors. GM3 distribution was analyzed by immunofluorescence and immunoelectron microscopy. A follow-up study to detect anti-lymphocytic GM3 antibodies was performed in progressive and nonprogressive anti-HIV+ subjects. Lymphocytes from HIV-infected patients showed a significant increase of plasma membrane GM3 content; no difference was found between CD4+ and CD8+ cells. Immunofluorescence and immunoelectron microscopic analysis showed that GM3 was distributed in large clusters over the cell plasma membrane. The follow-up study revealed that the occurrence of anti-lymphocytic GM3 antibodies was significantly higher in patients with progressive disease, compared with asymptomatic non-progressive subjects. These findings revealed that (1) the increased GM3 content in HIV-infected patients is detected at the plasma membrane level, (2) GM3 overexpression is able to induce an increased reactivity with anti-GM3 antibodies, and (3) the appearance of anti-lymphocytic GM3 antibodies in asymptomatic anti-HIV+ subjects could have prognostic relevance for the risk of developing AIDS.

Retrovirus budding may constitute a port of entry for drug carriers

This paper investigates the relation between viral infection and cell uptake of liposomes and nanoparticles. A defective virus was used to infect two types of cells: cells allowing virus budding (psi2neo cells) and cells bereft of a virus exit process (NIH 3T3 cells). This study has revealed that cell uptake of pH-sensitive-liposomes is highly dependent on the virus exit process, since it ensued only when virus budding occurred. This preferential uptake of pH-sensitive liposomes by infected cells was not carrier-specific because similar uptake was observed with non-biodegradable fluorescent nanoparticles using confocal microscopy. Also, inhibition of neo gene expression by oligonucleotide pH-sensitive-liposomes was only observed in the cell system (psi2neo) endowed with a virus exit process. Finally, increased membrane fluidity was noted in the infected cells, possibly reflecting membrane perturbation due to virus budding. We suggest that this membrane perturbation may be the key to the uptake of the different colloidal carriers. Infected cells could, thus, constitute a natural target for particulate drug carriers.

The non-steroidal anti-inflammatory drug, indomethacin, as an inhibitor of HIV replication

Indomethacin, a common non-steroidal anti-inflammatory drug (NSAID), has been used to treat rheumatoid arthritis. Although indomethacin has also been used as an immunopotentiator and symptomatic NSAID in AIDS, its effect on HIV replication is unknown. MT-4 lymphocytes were inoculated with HIV in the presence of indomethacin and tested for p24 expression by ELISA. The 50% inhibition (IC50) was 10 microM, corresponding to plasma levels after administration of 50 mg oral indomethacin. The antiviral effect appears to be specific since no toxicity has been observed at the IC50 dose, and unrelated NSAIDs have not shown the activity at clinical doses. Indomethacin may, thus, represent a new class of anti-HIV drug.

Expression of alpha-fetoprotein and interleukin 2 receptors and impairment of membrane fluidity in peripheral blood mononuclear cells from AIDS and related syndromes

We have previously shown that the expression of alpha-fetoprotein (AFP) receptors is impaired in mitogen-activated peripheral blood mononuclear cells (PBMCs) from HIV+ individuals and that this novel abnormality reflects an unusual proliferation response of PBMCs to mitogenic stimuli. Here we comparatively analyze, in PBMCs from patients with AIDS and related syndromes, (1) changes in membrane fluidity, measured as the cholesterol/phospholipid ratio (CH/PL), and (2) changes in the expression of AFP receptors and of the alpha chain of IL-2 receptor (TAC antigen). Relative to normal cells, the expression of AFP and IL-2 receptors appeared considerably reduced in AIDS-related complex (ARC) and AIDS patients. In asymptomatic HIV+ individuals the amount of AFP receptors was within the normal range, whereas that of IL-2 receptors increased twice. CH/PL ratios were significantly lower in PHA-activated than in quiescent PBMCs from healthy donors, which implies a gain in membrane fluidity. For seropositive groups, no statistically significant changes in CH/PL ratios were appreciated on PHA activation. Nevertheless, in HIV+ asymptomatic individuals, the CH/PL ratio of quiescent PBMCs resembled that of PHA-activated PBMCs from healthy donors, suggesting that quiescent PBMCs are in a partially activated or "preactivated" status. With the worsening of the disease, toward ARC and AIDS stages, however, quiescent PBMCs from these groups showed a considerable loss in membrane fluidity, evidenced by elevated values of the CH/PL ratio. This radical change strongly suggest a severe alteration of the lipid metabolism in these cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Lovastatin inhibits HIV-1 expression in H9 human T lymphocytes cultured in cholesterol-poor medium

The effects of the HMG-Coenzyme A reductase inhibitor lovastatin on HIV-1 expression and sterol synthesis have been investigated in the human H9 lymphocytic cell line. To this purpose, sterol synthesis from 14C-acetate, cell multiplication and reverse transcriptase activity have been measured in parallel at various times after cell infection by HIV-1. It was found that nine days after viral loading, lovastatin inhibited both sterol synthesis and viral multiplication as assessed by the reverse transcriptase activity. Since HIV infection has been shown to induce alterations in membrane cholesterol content, suggesting that the virus cycle may be partially dependent upon cellular cholesterol, inhibitors of cholesterol synthesis could be an interesting way of research in order to slower HIV propagation.

High dose L-carnitine improves immunologic and metabolic parameters in AIDS patients

Several reports indicate that systemic carnitine deficiency could occur in acquired immunodeficiency disease syndrome (AIDS), and that primary and secondary carnitine deficiency leads to critical metabolic dysfunctions. L-carnitine supplementation to peripheral blood mononuclear cells (PBMCs) of AIDS patients resulted in significant enhancement of the phytohemagglutinin (PHA)-driven proliferative response. High dose L-carnitine administration (6 gr per day for two weeks) to AIDS patients treated with zidovudine also led to increased PBMCs proliferation and reduced blood levels of triglycerides. In addition, a reduction of beta 2-microglobulin serum levels as well as circulating tumor necrosis factor (TNF)-alpha, mostly in patients exhibiting highly elevated levels, were found at the end of the treatment period. Our data suggest that in vivo L-carnitine could prove useful in ameliorating both the immune response and lipid metabolism in patients with AIDS, irrespective of initial serum carnitines levels. The mechanism(s) accounting for the observed results are currently not clear. Further studies are needed to confirm the hypothesis that L-carnitine affects the expression of HIV-induced cytokine.

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.