Death Of CD4 Research Articles

DRAM Triggers Lysosomal Membrane Permeabilization and Cell Death in CD4+ T Cells Infected with HIV

Productive HIV infection of CD4+ T cells leads to a caspase-independent cell death pathway associated with lysosomal membrane permeabilization (LMP) and cathepsin release, resulting in mitochondrial outer membrane permeabilization (MOMP). Herein, we demonstrate that HIV infection induces damage-regulated autophagy modulator (DRAM) expression in a p53-dependent manner. Knocking down the expression of DRAM and p53 genes with specific siRNAs inhibited autophagy and LMP. However, inhibition of Atg5 and Beclin genes that prevents autophagy had a minor effect on LMP and cell death. The knock down of DRAM gene inhibited cytochrome C release, MOMP and cell death. However, knocking down DRAM, we increased viral infection and production. Our study shows for the first time the involvement of DRAM in host-pathogen interactions, which may represent a mechanism of defense via the elimination of infected cells.

Abstract B90: Eribulin mesylate alters immune homeostasis in mice bearing syngeneic tumors.

Abstract Numerous studies indicate that certain tumor-infiltrating macrophage subsets can support neoplastic growth. Recent reports showed that spleen can serve as an important reservoir for macrophages and neutrophils that replicate in situ, then migrate to support tumor growth. Eribulin mesylate (Halaven®) is a microtubule-dynamics inhibitor approved for third line clinical use in patients with heavily pretreated metastatic breast cancer based upon statistically significant increase in median overall survival (OS) compared to treatment of physician's choice. In an effort to understand whether eribulin has additional effects beyond its anti-mitotic activity, the current study addressed the effects of eribulin mesylate on immune cells. Using the subcutaneous syngeneic murine tumor model Lewis lung carcinoma (LLC), we found that the tumor shrinking effect of eribulin correlated with increased extramedullary hematopoiesis observed in the spleens of treated mice. Eribulin was also found to inhibit the proliferation of M2 tumor-associated macrophages (TAMs) in the spleens of LLC-bearing mice. Early effects of eribulin were studied using the CT-26 colon tumor isograft model and included increased differentiation and death of CD4+ and CD8+ effector T cells. Furthermore, eribulin caused increased CD25 expression on CD4+ Foxp3- T cells but not on CD4+ Foxp3+ T regulatory cells. Finally, frequencies of exhausted CD8+ T cells were reduced following eribulin treatment. Taken together, these results suggest that eribulin-mediated modulation of immune homeostasis especially in the spleen, may contribute to its anti-tumor effect. Citation Format: Diana I. Albu, Namita Kumar, Galina Kusnetzov, Shanqin Xu, Bruce Littlefield, Mary Woodall-Jappe. Eribulin mesylate alters immune homeostasis in mice bearing syngeneic tumors. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology: Multidisciplinary Science Driving Basic and Clinical Advances; Dec 2-5, 2012; Miami, FL. Philadelphia (PA): AACR; Cancer Res 2013;73(1 Suppl):Abstract nr B90.

Modulation of LPS-Induced CD4+ T-Cell Activation and Apoptosis by Antioxidants in Untreated Asymptomatic HIV Infected Participants: AnIn VitroStudy

Persistent immune activation characterises HIV infection and is associated with depletion of CD4+ T-cells and increased risk of disease progression. Early loss of gut mucosal integrity results in the translocation of microbial products such as lipopolysaccharide (LPS) into the systemic circulation. This is an important source of on-going immune stimulation. The purpose of this study was to determine levels of CD4+ T-cell activation (%CD25 expression) and apoptosis (% annexin V/7-AAD) in asymptomatic, untreated HIV infection at baseline and after stimulation with LPS and incubation with or without vitamin C and N-acetylcysteine. LPS induced a significant (P < 0.03) increase in %CD25 expression, annexin V, and 7-AAD in HIV positive individuals. NAC in combination with vitamin C, significantly (P = 0.0018) reduced activation and early apoptosis of CD4+ T-cells to a greater degree than with either antioxidant alone. Certain combinations of antioxidants could be important in reducing the harmful effects of chronic immune activation and thereby limit CD4+ T-cell depletion. Importantly, we showed that CD4+ T-cells of the HIV positive group responded better to a combination of the antioxidants at this stage than those of the controls. Therefore, appropriate intervention at this asymptomatic stage could rescue the cells before repetitive activation results in the death of CD4+ T-cells.

Raltegravir intensification shows differing effects on CD8 and CD4 T cells in HIV-infected HAART-suppressed individuals with poor CD4 T-cell recovery

Immunodiscordant HIV-infected patients show viral suppression during antiretroviral therapy but fail to recover CD4 T cells. Immunodiscordance is characterized by partial CD4 T-cell immunodeficiency and increased inflammation, activation and immunosenescence in both CD4 and CD8 T cells. A randomized, controlled, 48-week intensification study to assess the effect of raltegravir on immunological parameters in immunodiscordant patients (CD4 cell counts <350 cells/μl; viral load <50 copies/ml for >2 years). Patients were randomized (2 : 1) to intensify therapy with raltegravir (intensified arm, n = 30) or continue with the same therapy (control arm, n = 14). Both groups showed similar immunological baseline characteristics. CD4 T-cell counts increased faster in the intensified arm (P = 0.01, week 12). However, no differences between groups were observed at week 48. Additionally, no changes in thymic output (CD45RA(+)CD31(+) cells), activation (HLA-DR(+)CD95(+) cells) or ex-vivo cell death were observed in CD4 T cells at any time point intergroups or intragroups. Conversely, intensified arm showed significant decreases in the expression of the CD8 T-cell activation marker CD38 at weeks 24-48, which were more evident in memory cells. Despite this, the levels of HLA-DR expression in CD8 T cells and plasma soluble CD14 remained stable in both arms overtime. Long-term (48-week) raltegravir intensification failed to counterbalance CD4 T-cell deficiency and its associated features: hyperactivation and death of CD4 T cells. However, raltegravir induced a specific reduction of CD38 expression in CD8 T cells, suggesting a beneficial effect on CD8 T-cell hyperactivation, which has been linked with HIV-associated comorbidities.

Anti-latency agents to purge HIV reservoirs

The persistence of latent HIV-infected cellular reservoirs represents the major hurdle to virus eradication with highly active anti-retroviral therapy (HAART), since latently infected cells remain a permanent source of viral reactivation. HIV establishes a persistent infection in CD4+ T lymphocytes (and to a lesser extent in macrophages as well), creating a persistent reservoir consisting mainly of latently infected resting memory CD4+ T cell. Although pre- and post-integration latencies have been described in HIV-1, the reservoir that appears to be the major barrier to eradication is composed of latently infected cells carrying an integrated provirus that is transcriptionally silent. It has been suggested that reactivation of the latent reservoirs could allow effective targeting and possible eradication of the virus. Immunoactivation therapy to reduce the latent pool of HIV by treatment with the anti-CD3 antibody OKT-3 alone or in combination with interleukin-2, substantially failed to significantly decrease the viral reservoir. Non-specific T-cell activation may induce high-level viral replication above a level that can be fully contained by ART, while increasing the susceptibility of uninfected cells. Selective targeting of HIV provirus via agents that induce the expression of quiescent HIV, but have limited effects on the uninfected host cell is an alternate approach to attack latent HIV. Activation from latency to completion of the replication cycle should result in lytic cell death of CD4+ T cells. Multiple mechanisms that contribute to the maintenance of proviral latency could be targeted to activate the latent virus. As examples of potentially useful agents, IL–7 can reactivate HIV–1 in latently infected cells in vitro through the induction of the Janus kinase–signal transducer and activator of transcription (JAK–STAT) signalling pathway. The use of different chemical compounds targeting the PKC signalling pathway (prostratin, bryostatin) has also been proposed as a means of reactivating viral reservoirs. Finally, HDAC blocking is an attractive potential means of inducing broad reactivation of HIV–1 reservoirs, and promising results have been achieved using the HDAC inhibitor vorinostat.

An Artificial Antigen-presenting Cell with Paracrine Delivery of IL-2 Impacts the Magnitude and Direction of the T Cell Response

Artificial antigen-presenting cells (aAPCs) are an emerging technology to induce therapeutic cellular immunity without the need for autologous antigen-presenting cells (APCs). To fully replace natural APCs, an optimized aAPC must present antigen (signal 1), provide costimulation (signal 2), and release cytokine (signal 3). Here we demonstrate that the spatial and temporal characteristics of paracrine release of IL-2 from biodegradable polymer aAPCs (now termed paAPCs) can significantly alter the balance in the activation and proliferation of CD8+ and CD4+ T cells. Paracrine delivery of IL-2 upon T cell contact with paAPCs induces significant IL-2 accumulation in the synaptic contact region. This accumulation increases CD25 (the inducible IL-2 Rα chain) on responding T cells and increases proliferation of CD8+ T cells in vitro to levels 10 times that observed with equivalent amounts of bulk IL-2. These CD8+ T cell responses critically depend upon close contact of T cells and the paAPCs and require sustained release of low levels of IL-2. The same conditions promote activation-induced cell death in CD4+ T cells. These findings provide insight into the response of T cell subsets to paracrine IL-2.

A Role for p120 RasGAP in Thymocyte Positive Selection and Survival of Naive T Cells

Activation of the Ras small GTP-binding protein is necessary for normal T cell development and function. However, it is unknown which Ras GTPase-activating proteins (RasGAPs) inactivate Ras in T cells. We used a T cell-specific RASA1-deficient mouse model to investigate the role of the p120 RasGAP (RASA1) in T cells. Death of CD4(+)CD8(+) double-positive thymocytes was increased in RASA1-deficient mice. Despite this finding, on an MHC class II-restricted TCR transgenic background, evidence was obtained for increased positive selection of thymocytes associated with augmented activation of the Ras-MAPK pathway. In the periphery, RASA1 was found to be dispensable as a regulator of Ras-MAPK activation and T cell functional responses induced by full agonist peptides. However, numbers of naive T cells were substantially reduced in RASA1-deficient mice. Loss of naive T cells in the absence of RASA1 could be attributed in part to impaired responsiveness to the IL-7 prosurvival cytokine. These findings reveal an important role for RASA1 as a regulator of double-positive survival and positive selection in the thymus as well as naive T cell survival in the periphery.

CD8+ T cell trafficking post primary Influenza A virus infection (102.26)

Abstract An important model for studying influenza A virus (IAV) infection is the acute antiviral immune responses. It is of a great interest to understand the growth and migration of virus-specific CD8+ T cells post IAV infection. However, the biological parameters that determine the kinetics of immune cells currently cannot be directly measured by experiments techniques. In this work, we developed mechanistic and semi-mechanistic mathematical models to infer the expansion, trafficking, and disappearance of CD8+ T cells in lymph node, spleen and lung from mice with primary influenza A infection. It was found that the spleen is a major contributor of effector CD8+ T cells to the lung in comparison with the lymph node. In addition, it is veryfied that the death of CD8+ T cells in lung follows a time-varying pattern. Tissues other than the lung and lymphatic organs notably contribute to the response in the lung, but not dominate the contributions from spleen. Our efforts provide a better understanding of the primary CD8+ T cell response to influenza infection.

2-Gy whole-body irradiation significantly alters the balance of CD4+ CD25- T effector cells and CD4+ CD25+ Foxp3+ T regulatory cells in mice.

CD4(+)CD25(+) T regulatory (Treg) cells are critical in inducing and maintaining immunological self-tolerance as well as transplant tolerance. The effect of low doses of whole-body irradiation (WBI) on CD4(+)CD25(+)Foxp3(+) Treg cells has not been determined. The proportion, phenotypes and function of CD4(+)CD25(+) Treg cells were investigated 0.5, 5 and 15 days after euthymic, thymectomized or allogeneic bone marrow transplanted C57BL/6 mice received 2-Gy γ-rays of WBI. The 2-Gy WBI significantly enhanced the ratios of CD4(+)CD25(+) Treg cells and CD4(+)CD25(+)Foxp3(+) Treg cells to CD4(+) T cells in peripheral blood, lymph nodes, spleens and thymi of mice. The CD4(+)CD25(+) Treg cells of the WBI-treated mice showed immunosuppressive activities on the immune response of CD4(+)CD25(-) T effector cells to alloantigens or mitogens as efficiently as the control mice. Furthermore, 2-Gy γ-ray WBI significantly increased the percentage of CD4(+)CD25(+)Foxp3(+) Treg cells in the periphery of either thymectomized mice or allogeneic bone marrow transplanted mice. The in vitro assay showed that ionizing irradiation induced less cell death in CD4(+)CD25(+)Foxp3(+) Treg cells than in CD4(+)CD25(-) T cells. Thus, a low dose of WBI could significantly enhance the level of functional CD4(+)CD25(+)Foxp3(+) Treg cells in the periphery of naive or immunized mice. The enhanced proportion of CD4(+)CD25(+)Foxp3(+) Treg cells in the periphery by a low dose of WBI may make hosts more susceptible to immune tolerance induction.

CD4 T-cell hyperactivation and susceptibility to cell death determine poor CD4 T-cell recovery during suppressive HAART

The failure to increase CD4 T-cell counts in some HAART-treated HIV-infected patients with satisfactory virological responses has been related to low CD4 T-cell production, high turnover and death. However, the relative contribution of these factors is still unclear, strongly limiting the definition of appropriate therapeutic strategies for these patients. A cross-sectional study was designed to evaluate the contribution of thymic activity, microbial translocation, cellular activation and death to CD4 T-cell recovery. We included 230 HIV-infected individuals on suppressive HAART (>2 years); 95 of them were considered 'discordant' (CD4 T-cell count <350 cells/mul) and 135 were considered 'concordant'. Comparative and logistic regression analyses were performed. Discordant patients showed higher levels of activated [human leukocyte antigen (HLA)-DRCD95 and CD38CD45RA] cells in both the CD8 and CD4 T-cell compartments. Notably, the most significant differences were observed in CD4 T cells. Discordant patients showed lower naive CD4 T-cell production (CD45RACD31 cells), higher spontaneous ex-vivo CD4 T-cell death and higher plasma levels of soluble CD14. Multivariate analysis showed that activation and death of CD4 T cells, along with nadir CD4 T-cell counts, were the only predictive factors for poor immune recovery. Moreover, the low correlations found between CD4 T-cell activation or death with thymic output and bacterial translocation suggest that additional factors modulate cellular activation and death and, in turn, CD4 T-cell recovery. CD4 T-cell repopulation during HAART is determined by CD4 T-cell activation and death. Therefore, strategies aimed to reduce these parameters should be envisaged to treat discordant patients.

GITR expression onT-cell receptor-stimulated human CD8+T cell in a JNK-dependent pathway

Glucocorticoid-induced tumor necrosis factor receptor (TNFR) (GITR) family-related gene is a member of the TNFR super family. GITR works as one of the immunoregulatory molecule on CD4+ regulatory T cells and has an important role on cell survival or cell death in CD4+ T cells. Little is known about the expression of GITR on human CD8+ T cells on antigen-specific and non-specific activation. Here, we report that expression of GITR on human CD8+ T cells on T-cell receptor (TCR) (anti-CD3)-mediated stimulation is dependent on the JNK pathway. The activation of CD8+ T cells was measured by the expression of IL-2 receptor-α (CD25), GITR and by IFN-γ production upon re-stimulation with anti-CD3 antibody. We studied the signaling pathway of such inducible expression of GITR on CD8+ T cells. We found that a known JNK-specific inhibitor, SP600125, significantly down-regulates GITR expression on anti-CD3 antibody-mediated activated CD8+ T cells by limiting JNK phosphorylation. Subsequently, after stimulation of the CD8+ cells, we tested for the production of IFN-γ by the activated cells following restimulation with the same stimulus. It appears that the expression of GITR on activated human CD8+ T cells might also be regulated through the JNK pathway when the activation is through TCR stimulation. Therefore, GITR serves as an activation marker on activated CD8+ cells and interference with JNK phosphorylation, partially or completely, by varying the doses of SP600125 might have implications in CD8+ cytotoxic T cell response in translational research.

Sanctuaire du virus de l’immunodéficience humaine et mécanismes d’échappement

The identification of human immunodeficiency virus type 1 (HIV-1) reservoir has been the center of extensive research for 25 years. In a recent work published in Cell Death and Differentiation, we show that mesenteric lymph nodes which drain intestine could represent the main reservoir for the virus. This concept has been established in a rhesus macaque model. Moreover, among the mechanisms associated with the lack of viral control, we suggest a major role of apoptosis in the death of CD8 T cells. This programmed cell death is associated with increased expression of immunosuppressive factors in lymph nodes such as TGF-b and two molecules regulating lymphocyte metabolism, IDO and PD-1. In this context, the virus benefits from the immune suppression which prevails within this "sanctuary", which offers optimal conditions for its persistence.

Telomerase Is Involved in IL-7-Mediated Differential Survival of Naive and Memory CD4+ T Cells

IL-7 plays an essential role in T cell maintenance and survival. The survival effect of IL-7 is thought to be mediated through regulation of Bcl2 family proteins. After a comparative analysis of IL-7-induced growth and cell death of human naive and memory CD4(+) T cells, we observed that more memory CD4(+) T cells underwent cell division and proceeded to apoptosis than naive cells in response to IL-7. However, IL-7-induced expressions of Bcl2 family members (Bcl2, Bcl-x(L), Bax, and Bad) were similar between naive and memory cells. Instead, we found that IL-7 induced higher levels of telomerase activity in naive cells than in memory cells, and the levels of IL-7-induced telomerase activity had a significant inverse correlation with cell death in CD4(+) T cells. Furthermore, we showed that reducing expression of telomerase reverse transcriptase and telomerase activity significantly increased cell death of IL-7-cultured CD4(+) T cells. Together, these findings demonstrate that telomerase is involved in IL-7-mediated differential survival of naive and memory CD4(+) T cells.

Bcl-xL is associated with the anti-apoptotic effect of IL-15 on the survival of CD56 dim natural killer cells

Human NK cells can be distinguished into CD56 bright and CD56 dim subsets based on cell surface CD56 density. It has been shown that IL-2 and IL-15 have opposing effects on life and death of CD8 + T cells. However, the roles of IL-2 and IL-15 in regulating these two NK cell subsets remain elusive. In this study, we comparatively analyzed the effects of IL-2 and IL-15 on two NK cell subsets. IL-15 improved the proliferation and activation of CD56 dim NK cells in long-term cord blood mononuclear cell culture, but IL-2 only maintained the survival of CD56 bright NK cells. The percentage of CD56 +Annexin V + NK cells cultured with IL-15 was lower than that with IL-2; moreover, most of Annexin V + NK cells were primarily in the CD56 dim NK cells. IL-15 cultured NK cells expressed higher level of Bcl-xL than IL-2 cultured cells. Furthermore, IL-15 more strongly upregulated CD25 expression and better maintained the expression of IL-15Rα than IL-2. These results suggest that CD56 dim NK cells undergo apoptosis when cultured with IL-2, but IL-15 inhibits their apoptosis and Bcl-xL is associated with the anti-apoptotic effect of IL-15. So IL-15 played a crucial role in sustaining long-lasting functions of CD56 dim NK cells.

Flying in the Face of Resistance: Antiviral-independent Benefit of HIV Protease Inhibitors on T-cell Survival

Human immunodeficiency virus (HIV) infection results in excessive apoptosis of infected and uninfected cells, mediated by host and viral factors present in plasma. As HIV protease inhibitors (PIs) have intrinsic antiapoptotic properties, we questioned whether HIV PIs could block HIV-induced CD4+ T-cell death independent of their effects on HIV replication. We demonstrate that HIV PIs block the death of CD4+ T cells induced by HIV glycoprotein 120 (gp120), Vpr, and Tat, as well as host signals Fas ligand, tumor necrosis factor, and tumor necrosis factor-related apoptosis-inducing ligand. Using gp120/CXCR4 as a model, we show that the HIV PIs specifically block mitochondrial apoptosis signaling. Furthermore, HIV PIs inhibit CD4+ T-cell death induced by viruses with high-level resistance to PIs (P<0.01) and apoptosis induced by serum of HIV patients with known resistance to HIV PIs (P=0.01). Together, these results show that HIV PIs block CD4+ T-cell death and have a beneficial effect on CD4+ T-cell survival despite PI resistance.

Death of CD4+ T Cells from Lymph Nodes during Primary SIVmac251 Infection Predicts the Rate of AIDS Progression

Immunological and virological events that occur during the earliest stages of SIV infection are now considered to have a major impact on subsequent disease progression. In the present study, we demonstrate a clear correlation between progression to AIDS and the rate of in vitro CD4+ (but not CD8+) T cell death in lymph nodes. The dying CD4+ T cells were effector memory T cells, which are critical for the immune response to pathogens. However, there was no correlation between the rate of the viral replication within lymph nodes and the extent of Fas ligand-mediated death, despite the increased sensitivity of CD4+ T cells to death in response to recombinant human Fas ligand. CD4+ T cell death was caspase and apoptosis-inducing factor independent but was clearly associated with mitochondrion damage. Interestingly, higher expression levels of the active form of Bak, a proapoptotic molecule involved in mitochondrial membrane permeabilization, were observed in SIV-infected macaques progressing more rapidly to AIDS. Finally, we demonstrated that the strain of SIV we used requires CCR5 and BOB/GRP15 molecules as coreceptors and caused death of unstimulated noncycling primary CD4+ T cells. Altogether, these results demonstrate that CD4+ T cell death occurring early after SIV infection is a crucial determinant of progression to AIDS and that it is mediated by the intrinsic death pathway.

Soluble MHC-Peptide Complexes Containing Long Rigid Linkers Abolish CTL-Mediated Cytotoxicity

Soluble MHC-peptide (pMHC) complexes induce intracellular calcium mobilization, diverse phosphorylation events, and death of CD8+ CTL, given that they are at least dimeric and co-engage CD8. By testing dimeric, tetrameric, and octameric pMHC complexes containing spacers of different lengths, we show that their ability to activate CTL decreases as the distance between their subunit MHC complexes increases. Remarkably, pMHC complexes containing long rigid polyproline spacers (> or =80 A) inhibit target cell killing by cloned S14 CTL in a dose- and valence-dependent manner. Long octameric pMHC complexes abolished target cell lysis, even very strong lysis, at nanomolar concentrations. By contrast, an altered peptide ligand antagonist was only weakly inhibitory and only at high concentrations. Long D(b)-gp33 complexes strongly and specifically inhibited the D(b)-restricted lymphocytic choriomeningitis virus CTL response in vitro and in vivo. We show that complications related to transfer of peptide from soluble to cell-associated MHC molecules can be circumvented by using covalent pMHC complexes. Long pMHC complexes efficiently inhibited CTL target cell conjugate formation by interfering with TCR-mediated activation of LFA-1. Such reagents provide a new and powerful means to inhibit Ag-specific CTL responses and hence should be useful to blunt autoimmune disorders such as diabetes type I.

Glutathione precursor prevents 4‐hydroxynonenal‐induced cytotoxicity in CD4 + T lympnocytes

4-Hydroxynonenal (HNE), an aldehydic product of lipid peroxidation, is an important component of disease pathogenesis involving oxidative stress, such as aging, alcoholic liver diseases, HIV/HCV infection, etc. HNE-induced immunosuppression can lead to the loss of CD4+ T lymphocytes. Previously, we found that HNE-induced apoptotic cell death in CD4+ T cells and involved intracellular glutathione (GSH) depletion. It has been demonstrated that formation of S-adenosyl-L-methionine (SAMe), catalyzed by SAMe synthetase (methionine adenosyltransferase II), is required for CD4+ T cell activation and proliferation. Also, SAMe is a precursor for GSH synthesis through the transsulfuration pathway. Thus, in the present work we investigated the effect of HNE on lymphocytic SAMe metabolism. We found that HNE inhibited MAT II activity and MAT2A mRNA and concomitantly depleted intracellular SAMe levels in a dose-dependent manner. Inhibition of MAT II and resultant decrease in SAMe levels induced caspase-3 dependent DNA fragmentation and apoptotic cell death. Also, HNE decreased c-Myb expression which is a critical transcription factor of MAT. Importantly, 2(RS)-n-propylthiazolidine-4(R)-carboxylic acids (PTCA), a GSH precursor, restored intracellular levels of SAMe and GSH as well as upregulated c-Myb expression, thus protected against the HNE-induced apoptotic cell death. These results suggest that MAT II activity, SAMe and GSH are critical for T cell survival and could be the molecular targets in immunosuppressive disorders involving CD4+ T cells loss and dysfunction. Additionally, these data strongly indicate that PTCA could potentially be a part of therapeutic interventions aimed at protecting CD4+ T cells and attenuating immunosuppression caused by oxidative stress.

The Vif and Vpr accessory proteins independently cause HIV-1-induced T cell cytopathicity and cell cycle arrest

HIV type I (HIV-1) can cause G(2) cell cycle arrest and death of CD4(+) T lymphocytes in vitro and inexorable depletion of these cells in vivo. However, the molecular mechanism of viral cytopathicity has not been satisfactorily elucidated. Previously, we showed that HIV-1 kills T cells by a necrotic form of cell death that requires high level expression of an integrated provirus but not the env or nef genes. To determine which viral protein(s) are required for cell death, we systematically mutated, alone and in combination, the ORFs of the NL4-3 strain of HIV-1. We found that the elimination of the viral functions encoded by gag-pol and vpu, tat, and rev did not mitigate cytopathicity. However, elimination of the vif and vpr accessory genes together, but not individually, renders the virus incapable of causing cell death and G(2) cell cycle blockade. We thus identify vif and vpr as necessary for T cell cytopathic effects induced by HIV-1. These findings may provide an important insight into the molecular mechanism of viral pathogenesis in AIDS.

Mechanisms Of 4-Hydroxynonenal-hne (Lipid Hydroperoxide) Induced Apoptotic Death In Cd4 T Lymphocytes: Relevance To Hiv And Hcv Pathogenesis

s: Ninth International Congress of Therapeutic Drug Monitoring and Clinical Toxicology: Louisville, Kentucky April 23-28, 2005