Host factors and the pathogenesis of HIV-induced disease

Genotypic characterization and comparison of full-length envelope glycoproteins from South African HIV type 1 subtype C primary isolates that utilize CCR5 and/or CXCR4

CCR5 has preferentially been used by all circulating HIV-1 subtype C viruses for cell entry. Recently, we reported the highest proportion of CXCR4-utilizing primary isolates among a cohort of 20 South African AIDS patients. This study describes and compares the Env genotypic characteristics from these 20 HIV-1 subtype C (and unique CD recombinant) primary isolates. Fourteen primary isolates utilized CCR5, four (including the CD recombinant) used CXCR4, and two were dual tropic. Extensive analysis and comparison of important structural motifs such as the N-linked glycosylation sites, signal sequences, CD4-binding sites, variable loops, cleavage sites, known neutralizing antibody and small molecule inhibitor binding sites confirmed that other than the expected differences in the V3 loop, no sequence motifs distinguished between R5 and X4 tropism. Further correlation of the env genotype to functionally relevant motifs is necessary to elucidate the relationship between biologically and immunologically relevant sites and aid vaccine and novel drug design.

Disruption of the gamma c cytokine network in T cells during HIV infection

The common gamma chain (gammac)-sharing cytokines (IL's-2, 4, 7, 9, 15, and 21) play a vital role in the survival, proliferation, differentiation and function of T lymphocytes. As such, disruption of their signaling pathways would be expected to have severe consequences on the integrity of the immune system. Indeed, it appears that the signaling network of these cytokines is both disrupted and exploited by HIV at various stages of infection. IL-2 secretion and signaling downstream of its receptor are impaired in T cells from chronically-infected HIV+ patients. Elevated plasma IL-7 levels and decreased IL-7Ralpha expression in patient T cells results in significantly decreased responsiveness to this critical cytokine. Interestingly, IL-2 and IL-15 are also able to render CD4+ T cells permissive to HIV infection through their influence on the activity of the APOBEC3G deaminase enzyme. Herein, we describe the current state of knowledge on how the gammac cytokine network is affected during HIV infection, with a focus on how this impairs CD4+ and CD8+ T cell function while also benefiting the virus itself. We also address the use of cytokines as adjuncts to highly active antiretroviral therapy to bolster immune reconstitution in infected patients.

Analysis of the immune responses in chimpanzees infected with HIV type 1 isolates

The mechanisms of resistance to AIDS development in HIV-1-infected chimpanzees have remained elusive. Unique among chimpanzees naturally or experimentally infected with HIV, several animals of the Yerkes cohort have progressed to clinical AIDS with selection of isolates showing increased pathogenicity for chimpanzees. We compared progressors vs. nonprogressors among the HIV-infected chimpanzees that made up this cohort, eight of which have been infected with HIV-1 for over 14 years. The additional two progressors were infected de novo with chimpanzee-pathogenic HIV, rapidly leading to a progressor status. Nonprogressors were characterized by normal CD4(+) T cell counts and the absence of detectable viremia. In contrast, progressor chimpanzees had relatively high plasma viral loads associated with a dramatic loss of CD4(+) T cells. The analysis of immune responses showed a similar amplitude and breadth of ELISPOT T cell responses in both groups. HIV-specific proliferative responses were, however, absent in the progressor animals, which also exhibited increased levels of immune activation characterized by elevated levels of the circulating chemokines IP-10 and MCP-1. Of interest was the conservation of potent NK cell activity in all animals, potentially contributing to the extended symptom-free survival of progressor animals. Modest anti-HIV antibody titers were detectable in the nonprogressor group, but these antibodies exhibited good neutralizing activity. In progressors, however, two sets of data were noted: in animals that gradually selected for pathogenic isolates, or that were superinfected, very high neutralizing antibody titers were observed, although none to the pathogenic HIV. In contrast, two animals infected de novo with chimpanzee pathogenic HIV failed to mount an extensive humoral response and both failed to develop neutralizing antibodies to the virus. Taken together, pathogenic HIV infection in chimpanzees is associated with rapid loss of CD4(+) T cells and proliferative responses as well as higher levels of immune activation.

Antigenic stimulation in the simian model of HIV infection yields dilated cardiomyopathy through effects of TNFalpha

OBJECTIVE

To investigate a role for endogenous myocardial cytokine production in the development of HIV-associated cardiomyopathy.

DESIGN

Cardiomyopathy is a late-stage sequela of HIV infection. Although pathogenesis of this condition in HIV infection is poorly defined, inflammatory cytokines are recognized for their detrimental effects on myocardial structure and function. HIV infection is characterized by chronic immune activation and inflammatory cytokine dysregulation. As the myocardium itself is a rich potential source of inflammatory cytokines, HIV-mediated cytokine dysregulation may be an important contributor to development of HIV cardiomyopathy. An antigenic stimulation protocol conducted in the simian immunodeficiency virus (SIV) model of HIV infection was used to study the effects of endogenous cytokine production on myocardial structure and function.

METHODS

Twenty-six rhesus monkeys were assigned to treatment groups for a 35-day study. Animals were SIV-infected; SIV-infected and treated with killed Mycobacterium avium complex bacteria (MAC); SIV-infected, MAC-treated, and given the TNFalpha antagonist etanercept; or uninfected and MAC-treated. All animals were subjected to weekly echocardiographic studies. Hearts were collected for further evaluation at euthanasia.

RESULTS

SIV-infected, MAC-treated animals developed significant systolic dysfunction [left ventricular ejection fraction (LVEF) decline of 19 +/- 2%] and ventricular chamber dilatation [left ventricular end-diastolic diameter (LVEDD) increase of 26 +/- 6%] not seen in other groups. Concurrent treatment with etanercept prevented development of these changes, implicating a causative role of myocardial TNFalpha.

CONCLUSIONS

SIV-infected animals develop exaggerated myocardial pathology on stimulation with the ubiquitous environmental agent MAC. These responses are TNFalpha-dependent and may play a significant role in the development of cardiomyopathy in HIV infection.

The association of bone mineral density with HIV infection and antiretroviral treatment in women

BACKGROUND

Low bone mineral density (BMD) has been reported in HIV-infected women and men.

METHODS

We analysed cross-sectional BMD measured by regional dual X-ray absorptiometry at the lumbar spine (LS) and femoral neck (FN) in 152 HIV-negative and 274 HIV-positive (HIV+) women, adjusted for traditional low BMD risk factors.

RESULTS

BMD was significantly lower in protease inhibitor (PI) users than in all other groups, and highest in HIV-negative women. In multivariate analyses the prevalence of T-score < -1.0 was significantly higher in the HIV+ women naive to antiretroviral therapy (ART; odds ratio [OR] 4.36, 95% confidence interval [CI] 1.61, 11.8) and the women receiving PI-containing HAART (OR 3.72, CI 1.43, 9.68), with a non-significant difference in non-PI HAART users (OR 2.43, CI 0.92, 6.45), compared with HIV-negative women. In pair-wise adjusted comparisons, BMD was lower in ART-naive than in HIV-negative women (1.22 versus 1.30 g/cm2 at LS; P = 0.004), in PI compared with non-PI HAART users (1.00 versus 1.05 g/cm2 at FN; P = 0.014) and with those ART-naive (1.00 versus 1.03 g/cm2 at FN; P = 0.146). Potential confounders, including duration of ART, prior treatment regimens and traditional risk factors for low BMD did not explain these differences. Longer lopinavir use was significantly correlated with lower BMD (r2 = -0.39, P = 0.024 and r2 = -0.46, P = 0.006 at LS and FN, respectively) and longer efavirenz use with higher BMD (r2 = +0.32, P = 0.004 at FN).

CONCLUSIONS

HIV infection was associated with lower BMD in women, independent of the traditional risk factors for low BMD. PI-containing HAART compared with non-PI-containing HAART, and longer lopinavir use, were both associated with lower BMD, and efavirenz use was associated with higher BMD.

Nef-mediated enhancement of virion infectivity and stimulation of viral replication are fundamental properties of primate lentiviruses

Nef is a multifunctional accessory protein of primate lentiviruses. Recently, it has been shown that the ability of Nef to downmodulate CD4, CD28, and class I major histocompatibility complex is highly conserved between most or all primate lentiviruses, whereas Nef-mediated downregulation of T-cell receptor-CD3 was lost in the lineage that gave rise to human immunodeficiency virus type 1 (HIV-1). Whether or not other Nef activities are preserved between different groups of primate lentiviruses remained to be determined. Here, we show that nef genes from a large variety of HIVs and simian immunodeficiency viruses (SIVs) enhance virion infectivity and stimulate viral replication in human cells and/or in ex vivo infected human lymphoid tissue (HLT). Notably, nef alleles from unpassaged SIVcpz and SIVsmm enhanced viral infectivity, replication, and cytopathicity in cell culture and in ex vivo infected HLT as efficiently as those from HIV-1 and HIV-2, their human counterparts. Furthermore, nef genes from several highly divergent SIVs that have not been found in humans were also highly active in human cells and/or tissues. Thus, most primate lentiviral Nefs enhance virion infectivity and stimulate viral replication. Moreover, our data show that SIVcpz and SIVsmm Nefs do not require adaptive changes to perform these functions in human cells or tissues and support the idea that nef alleles from other primate lentiviruses would also be capable of promoting efficient virus spread in humans.

Production of the HIV-suppressive chemokines CCL3/MIP-1alpha and CCL22/MDC is associated with more effective antiretroviral therapy in HIV-infected children

BACKGROUND

Certain CC chemokines including ligands for the HIV-1 coreceptor CCR5 are associated with suppression of HIV-1 infection. Whether the release of these chemokines from lymphocytes influences treatment outcome in children receiving antiretroviral therapy is not known.

METHODS

A study of 175 HIV-infected children in Rio de Janeiro, Brazil was conducted to compare clinical measures and HIV-suppressive chemokine release. Clinical measures including %CD4 T cells, viral loads, and antiretroviral drug-resistant mutations were obtained. Chemokine release was measured in cultures of peripheral blood mononuclear cells collected from 135 children before or after receiving therapy. Chemokine levels were compared between subject groups stratified according to clinical measures and treatment regimen (1-2, 3-4, or no antiretrovirals) extant at the time of cell sample collection.

RESULTS

Mean viral loads did not vary significantly between treatment groups although there were significant differences in %CD4 T cells. Virus from children taking 3-4 antiretrovirals had significantly more drug-resistant mutations than did virus from those receiving 1-2 drugs. Among antiretroviral-treated children, there was a significant direct relationship between %CD4 T cells and MIP-1alpha/CCL3 and macrophage-derived chemokine/CCL22 production. In addition, there was a significant inverse relationship between viral load and MIP-1alpha production in patients receiving 3-4 antiretrovirals. Greater recovery of %CD4 T cells after therapy was associated with higher MIP-1alpha and macrophage-derived chemokine production at baseline.

CONCLUSIONS

The production of HIV-suppressive chemokines is associated with better outcome in children receiving antiretroviral regimens in settings where drug-resistant mutations are prevalent. Such information may provide insights for the design of treatment strategies for pediatric HIV infection under similar circumstances.

Depo-Provera abrogates attenuated lentivirus-induced protection in male rhesus macaques challenged intravenously with pathogenic SIVmac239

BACKGROUND

Progesterone administration prior to intravaginal challenge with pathogenic SIVmac239 decreases the protective efficacy of live attenuated vaccines in rhesus macaques.

METHODS

To determine if progesterone alters the efficacy of live attenuated vaccines through local or systemic effects, seven male rhesus macaques were immunized with SHIV89.6 and then challenged intravenously with SIVmac239. Three of these animals were treated with Depo-Provera 30 days prior to the SIV challenge.

RESULTS

The SHIV animals had significantly lower plasma viral RNA levels than the unimmunized control monkeys, but the Depo-Provera treated, SHIV-immunized animals did not. Despite the lack of protection, the Depo-Provera SHIV animals had strong SIV specific T-cell responses. However, altered patterns of NK frequency and CD38 T-cell expression prior to SIV challenge were observed in Depo-Provera SHIV animals.

CONCLUSIONS

Depo-Provera eliminates live-attenuated lentivirus vaccine efficacy in male rhesus monkeys through systemic effects on antiviral immunity and/or viral replication.

Interleukin-10-secreting CD4 cells from aged patients with AIDS decrease in-vitro HIV replication and tumour necrosis factor alpha production

OBJECTIVE

To evaluate the impact of age on the proliferative response, cytokine profile and viral kinetics in AIDS patients treated successfully with antiretroviral drugs.

METHODS

Peripheral blood mononuclear cells (PBMC), CD4 cell-depleted PBMC or CD4 T cells from young adult and aged HIV-1-infected patients were activated in vitro with anti-CD3 with or without interleukin (IL)-2. Lymphoproliferation and cytokines were measured after 3 days and in-vitro HIV-1 replication after 7 days.

RESULTS

Both lymphoproliferation and cytokine [IL-1beta, tumour necrosis factor alpha (TNF-alpha) and interferon gamma (IFN-gamma)] secretion were higher in younger than in older AIDS patients. In cultures of cells derived from aged patients and activated by anti-CD3, IFN-gamma production was severely damage and IL-10 production was much higher. Although IL-2 addition to activated PBMC elevated IFN-gamma secretion, IL-10 production remained elevated in the aged group. The depletion of CD4 T lymphocytes from these cultures dramatically reduced released IL-10 in the older group but did not alter significantly IFN-gamma production. Interestingly, higher IL-10 levels produced by CD4 T cells were related to lower in-vitro HIV-1 replication, and the blockade of this cytokine by anti-IL-10 monoclonal antibody enhanced virus replication. This effect may be correlated with elevated TNF-alpha secretion. Finally, impaired IFN-gamma secretion detected in activated CD4 T cells obtained from aged patients was not directly correlated with high IL-10 production.

CONCLUSIONS

Elevated IL-10 production by aged AIDS patients contributed considerably to control of HIV replication and to inhibition of TNF-alpha secretion but not to the reduced IFN-gamma production.

Identification of a CCR5-expressing T cell subset that is resistant to R5-tropic HIV infection

Infection with HIV-1 perturbs homeostasis of human T cell subsets, leading to accelerated immunologic deterioration. While studying changes in CD4(+) memory and naïve T cells during HIV-1 infection, we found that a subset of CD4(+) effector memory T cells that are CCR7(-)CD45RO(-)CD45RA(+) (referred to as TEMRA cells), was significantly increased in some HIV-infected individuals. This T cell subset displayed a differentiated phenotype and skewed Th1-type cytokine production. Despite expressing high levels of CCR5, TEMRA cells were strikingly resistant to infection with CCR5 (R5)-tropic HIV-1, but remained highly susceptible to CXCR4 (X4)-tropic HIV-1. The resistance of TEMRA cells to R5-tropic viruses was determined to be post-entry of the virus and prior to early viral reverse transcription, suggesting a block at the uncoating stage. Remarkably, in a subset of the HIV-infected individuals, the relatively high proportion of TEMRA cells within effector T cells strongly correlated with higher CD4(+) T cell numbers. These data provide compelling evidence for selection of an HIV-1-resistant CD4(+) T cell population during the course of HIV-1 infection. Determining the host factors within TEMRA cells that restrict R5-tropic viruses and endow HIV-1-specific CD4(+) T cells with this ability may result in novel therapeutic strategies against HIV-1 infection.

Human immunodeficiency virus type 1 variants resistant to first- and second-version fusion inhibitors and cytopathic in ex vivo human lymphoid tissue

Human immunodeficiency virus type 1 (HIV-1) fusion inhibitors blocking viral entry by binding the gp41 heptad repeat 1 (HR1) region offer great promise for antiretroviral therapy, and the first of these inhibitors, T20 (Fuzeon; enfuvirtide), is successfully used in the clinic. It has been reported previously that changes in the 3-amino-acid GIV motif at positions 36 to 38 of gp41 HR1 mediate resistance to T20 but usually not to second-version fusion inhibitors, such as T1249, which target an overlapping but distinct region in HR1 including a conserved hydrophobic pocket (HP). Based on the common lack of cross-resistance and the difficulty of selecting T1249-resistant HIV-1 variants, it has been suggested that the determinants of resistance to first- and second-version fusion inhibitors may be different. To further assess HIV-1 resistance to fusion inhibitors and to analyze where changes in HR1 are tolerated, we randomized 16 codons in the HR1 region, including those making contact with HR2 codons and/or encoding residues in the GIV motif and the HP. We found that changes only at positions 37I, 38V, and 40Q near the N terminus of HR1 were tolerated. The propagation of randomly gp41-mutated HIV-1 variants in the presence of T1249 allowed the effective selection of highly resistant forms, all containing changes in the IV residues. Overall, the extent of T1249 resistance was inversely correlated to viral fitness and cytopathicity. Notably, one HIV-1 mutant showing approximately 10-fold-reduced susceptibility to T1249 inhibition replicated with wild type-like kinetics and caused substantial CD4+-T-cell depletion in ex vivo-infected human lymphoid tissue in the presence and absence of an inhibitor. Taken together, our results show that the GIV motif also plays a key role in resistance to second-version fusion inhibitors and suggest that some resistant HIV-1 variants may be pathogenic in vivo.

Safety and efficacy of a lentiviral vector containing three anti-HIV genes--CCR5 ribozyme, tat-rev siRNA, and TAR decoy--in SCID-hu mouse-derived T cells

Gene therapeutic strategies show promise in controlling human immunodeficiency virus (HIV) infection and in restoring immunological function. A number of efficacious anti-HIV gene constructs have been described so far, including small interfering RNAs (siRNAs), RNA decoys, transdominant proteins, and ribozymes, each with a different mode of action. However, as HIV is prone to generating escape mutants, the use of a single anti-HIV construct would not be adequate to afford long range-viral protection. On this basis, a combination of highly potent anti-HIV genes--namely, a short hairpin siRNA (shRNA) targeting rev and tat, a transactivation response (TAR) decoy, and a CCR5 ribozyme--have been inserted into a third-generation lentiviral vector. Our recent in vitro studies with this construct, Triple-R, established its efficacy in both T-cell lines and CD34 cell-derived macrophages. In this study, we have evaluated this combinatorial vector in vivo. Vector-transduced CD34 cells were injected into severe combined immunodeficiency (SCID)-hu mouse thy/liv grafts to determine their capacity to give rise to T cells. Our results show that phenotypically normal transgenic T cells are generated that are able to resist HIV-1 infection when challenged in vitro. These important attributes of this combinatorial vector show its promise as an excellent candidate for use in human clinical trials.

Phenotypic variation in myocardial macrophage populations suggests a role for macrophage activation in SIV-associated cardiac disease

Cardiac abnormalities are common in HIV-infected individuals, and have been especially well documented as contributors to mortality in HIV-infected children. Underlying pathogenetic mechanisms responsible for myocardial disease in HIV-infection remain imperfectly understood. SIV-infected rhesus monkeys develop a spectrum of cardiac lesions similar to those seen in HIV-infected people, providing an important model for pathogenesis studies. Retrospective analysis of cardiac tissue collected at necropsy from SIV-infected rhesus monkeys was performed to evaluate myocardial macrophage and dendritic cell populations as a function of previously quantitated lymphocytic inflammatory infiltrates and cardiomyocyte degeneration or necrosis. Variations in the size and phenotype of macrophage and dendritic cell populations were examined as possible contributors to the pathogenesis of SIV-associated inflammatory lesions. Macrophages labeling immunohistochemically for CD163 differed substantially from macrophages labeling for HAM56 in overall number, distribution across groups, involvement in inflammatory clusters, correlation with the DC-SIGN(+) subpopulation of macrophages, and correlation with numbers of SIV-infected cells. CD163(+) macrophages occurred in significantly higher numbers in uninflamed hearts from SIV-infected animals than in hearts from SIV-infected animals with myocarditis or uninfected controls (p < 0.01). Numbers of CD163(+) cells correlated positively with numbers of SIV-infected cells (p < 0.05) suggesting that the CD163(+) population was associated with decreased inflammatory infiltration and reduced control of virus within the heart. As CD163 has been associated with nonclassical macrophage activation and an antiinflammatory phenotype, these results suggest that a balance between classical and nonclassical activation may affect levels of inflammatory infiltration and of myocardial virus burden.

Naturally occurring C-terminally truncated STAT5 is a negative regulator of HIV-1 expression

CD4(+) cells of most individuals infected with HIV-1 harbor a C-terminally truncated and constitutively activated form of signal transducer and activator of transcription-5 (STAT5 Delta). We report that the chronically HIV-infected U1 cell line expresses STAT5 Delta but not full-length STAT5. Granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulation of U1 cells promoted early activation of STAT5 Delta and of extracellular signal regulated kinases (ERKs), followed by later activation of activator protein 1 (AP-1) and HIV expression. Inhibition of ERK/AP-1 by PD98,059 abolished, whereas either tyrphostin AG490 or a STAT5 small interfering RNA (siRNA) enhanced, virion production in GM-CSF-stimulated U1 cells. Chromatin immunoprecipitation demonstrated the induction of STAT5 Delta binding to STAT consensus sequences in the HIV-1 promoter together with a decreased recruitment of RNA polymerase II after 1 hour of GM-CSF stimulation of U1 cells. Down-regulation of STAT5 Delta by siRNA resulted in the up-regulation of both HIV-1 gag-pol RNA and p24 Gag antigen expression in CD8-depleted leukocytes of several HIV-positive individuals cultivated ex vivo in the presence of interleukin-2 but not of interleukin-7. Thus, the constitutively activated STAT5 Delta present in the leukocytes of most HIV-positive individuals acts as a negative regulator of HIV expression.

IL-10 regulation by HIV-Tat in primary human monocytic cells: involvement of calmodulin/calmodulin-dependent protein kinase-activated p38 MAPK and Sp-1 and CREB-1 transcription factors

The anti-inflammatory cytokine, IL-10 plays an important role in HIV immunopathogenesis. The HIV accessory protein, Tat is not only critical for viral replication, but affects the host immune system by influencing cytokine production including IL-10. During HIV infection, IL-10 production by monocytic cells is up-regulated, representing a critical pathway by which HIV may induce immunodeficiency. Herein, we show that extracellular Tat-induced IL-10 expression in normal human monocytes. To understand the signaling pathways underlying HIV-Tat induced IL-10 transcription, we investigated the involvement of MAPK as well as calcium signaling and the downstream transcription factor(s). Our results suggest that Tat-induced calcium influx regulated IL-10 transcription in monocytic cells. The experiments designed to further understand the molecules involved in the calcium signaling suggested that calmodulin and calmodulin-dependent protein kinase-II (CaMK-II)-activated p38 MAPK played a role in extracellular Tat-induced IL-10 expression in primary human monocytes. Furthermore, Tat-induced IL-10 expression was regulated by p38 MAPK- and CaMK II-activated CREB-1 as well as Sp-1 transcription factors. Taken together, our results suggest that extracellular HIV-Tat induced IL-10 transcription in primary human monocytes is regulated by CREB-1 and Sp-1 transcription factors through the activation of calmodulin/CaMK-II-dependent p38 MAPK.

Primary human immunodeficiency virus type 1 nef alleles show major differences in pathogenicity in transgenic mice

We previously reported that the human immunodeficiency virus type 1 NL4-3 Nef is necessary and sufficient to induce a severe AIDS-like disease in transgenic (Tg) mice when the protein is expressed under the regulatory sequences of the human CD4 gene. We have now assayed additional Nef alleles (SF2, JR-CSF, YU10x, and NL4-3 [T71R] Nef alleles), including some from long-term nonprogressors (AD-93, 032an, and 039nm alleles) in the same Tg system and compared their pathogenicities. All these Nef alleles downregulated cell surface CD4 in human cells in vitro and also, with the exception of Nef(YU10x), in Tg CD4(+) T cells. Depletion of double-positive and single-positive thymocytes occurred with all alleles but was less pronounced in Nef(YU10x) Tg mice. A loss of peripheral CD4(+) T cells was observed with all alleles but was minimal in Nef(YU10x) Tg mice. In Nef(032an) and Nef(SF2) Tg mice, T-cell loss was severe despite lower levels of Tg expression, suggesting a higher virulence of these alleles. All Nef alleles except the Nef(YU10x) and Nef(NL4-3(T71R)) alleles induced an enhanced activated memory (CD25(+) CD69(+) CD44(high) CD45RB(low) CD62L(low)) and apoptotic phenotype. Also, all could interact with and/or activate PAK2 except the Nef(JR-CSF) allele. Organ (lung and kidney) diseases were present in Nef(NL4-3(T71R)), Nef(032an), Nef(039nm), and Nef(SF2) Tg mice, despite very low levels of Tg expression for the last strain. However, no organ disease or minimal organ disease developed in Nef(YU10x) and Nef(AD-93) Tg mice and Nef(JR-CSF) Tg mice, respectively, despite high levels of Tg expression. Our data show that important differences in the pathogenicities of various Nef alleles can be scored in Tg mice. Interestingly, our results also revealed that some phenotypes can segregate independently, such as CD4(+) T-cell depletion and activation, as well as severe depletion of thymic CD4(+) T cells and peripheral CD4(+) T cells. Therefore, expression of Nef alleles in Tg mice under the CD4C regulatory elements represents a novel assay for measuring their pathogenicity. Because of the very high similarity of this murine AIDS-like disease to human AIDS, this assay may have a predictive value regarding the behavior of Nef in infected humans.

CCR5 receptor antagonists: discovery and SAR of novel 4-hydroxypiperidine derivatives

The guanylhydrazone of 2-(4-chlorobenzyloxy)-5-bromobenzaldehyde, 1, with an IC(50) of 840 nM against the CCR5 receptor was identified using high-throughput screening. Optimization efforts led to the discovery of a novel piperidine series of CCR5 antagonists. In particular, the 4-hydroxypiperidine derivative, 6k, had improved potency against CCR5, and was a starting point for further optimization. SAR elaboration using parallel synthesis led to the identification of 10h, a potent CCR5 antagonist with an IC(50) of 11 nM.

Early depletion of proliferating B cells of germinal center in rapidly progressive simian immunodeficiency virus infection

Lack of virus specific antibody response is commonly observed in both HIV-1-infected humans and SIV-infected monkeys with rapid disease progression. However, the mechanisms underlying this important observation still remain unclear. In a titration study of a SIVmac239 viral stock, three out of six animals with viral inoculation rapidly progressed to AIDS within 5 months. Unexpectedly, there was no obvious depletion of CD4(+) T cells in both peripheral and lymph node (LN) compartments in these animals. Instead, progressive depletion of proliferating B cells and disruption of the follicular dendritic cell (FDC) network in germinal centers (GC) was evident in the samples collected at as early as 20 days after viral challenge. This coincided with undetectable, or weak and transient, virus-specific antibody responses over the course of infection. In situ hybridization of SIV RNA in the LN samples revealed a high frequency of SIV productively infected cells and large amounts of accumulated viral RNA in the GCs in these animals. Early severe depletion of GC proliferating B cells and disruption of the FDC network may thus result in an inability to mount a virus-specific antibody response in rapid progressors, which has been shown to contribute to accelerated disease progression of SIV infection.

Efficient induction of HIV-1 replication in latently infected cells through contact with CD4+ T cells: involvement of NF-kappaB activation

Reservoir cells latently infected with HIV-1 pose one of the major obstacles that hamper ultimate eradication of HIV-1 from infected patients. In this report, we showed that direct contact with MOLT-4 T cells induced HIV-1 replication in J(22)-HL-60 latently infected cells without any additional stimulus. Neutralization experiments revealed that pro-inflammatory cytokines, whose production was increased following cell-cell contact, were unlikely to be primarily involved in the induced HIV-1 replication. Cell-cell contact, but not soluble components in the culture supernatant, caused a rapid phosphorylation and degradation of IkappaBalpha, which led to elevated NF-kappaB DNA binding activity in J(22)-HL-60 cells. Furthermore, forced expression of a super-repressor form of IkappaBalpha or pretreatment with ritonavir efficiently blocked the activation of NF-kappaB and HIV-1 replication in J(22)-HL-60 cells co-cultured with MOLT-4 T cells. Moreover, either resting or PHA stimulated primary CD4(+) T cells induced HIV-1 replication in J(22)-HL-60 cells in a similar way with that of MOLT-4 cells. These results indicated that direct contact with CD4(+) T cells induced HIV-1 replication in latently infected cells and provide insight into the molecular mechanism of virus release from myeloid progenitor cells latently infected with HIV-1.

Citron kinase, a RhoA effector, enhances HIV-1 virion production by modulating exocytosis

RhoGTPases play important roles in the regulation of protein transport and membrane recycling. Little is known, however, about how RhoGTPases affect HIV-1 virion production, which is dependent on the endosomal sorting pathway. We report that ectopic expression of citron kinase (citron-K), a RhoA effector, preferentially enhances HIV-1 virion production. Depletion of endogenous citron-K inhibits HIV-1 virion production. Citron-N, which lacks the kinase domain, also enhances HIV-1 virion production. The leucine zipper, Rho-binding and zinc finger domains of citron-N are necessary for the enhancement activity. Citron-K also enhances murine leukemia virion production and the HIV-1 late domain is not required for the citron-K-mediated enhancement. Ectopic expression of citron-K leads to the formation of cytoplasmic structures containing citron-K and HIV-1 Gag proteins. HIV-1 and citron-K cooperatively enhance acidic endosome and lysosome compartments. Finally, citron-K promotes exocytosis of microvesicles or exosomes that co-purify with HIV-1 virions. We conclude that citron-K enhances HIV-1 virion production by stimulating the endosomal compartments and exocytosis.

Distinct patterns of cytokine regulation of APOBEC3G expression and activity in primary lymphocytes, macrophages, and dendritic cells

Human APOBEC3G (A3G), a deoxycytidine deaminase, is a broadly acting antiretroviral factor expressed in a variety of cells. Mitogen activation of CD4 T cells enhances A3G expression and leads to recruitment of low molecular mass (LMM) A3G, which functions as a post-entry human immunodeficiency virus (HIV) restriction factor, into enzymatically inactive, high molecular mass (HMM) RNA-protein complexes that include Staufen RNA-transporting granules. We now report that interleukin-2 (IL-2), IL-15 and, to a lesser extent, IL-7 enhance the expression of A3G in peripheral blood lymphocytes and that this effect is blocked by inhibitors of the JAK and MAPK signaling pathways. In mixed cultures of CD4+ T cells containing either HMM or LMM A3G, HIV preferentially infected cells containing HMM A3G. A3G shifted into a HMM complex when IL-2, -7, or -15 was added to resting T cells, likely explaining how cytokine treatment renders resting CD4+ T cells permissive to HIV infection. Similarly, poly(I:C)/tumor necrosis factor-alpha-induced maturation of dendritic cells was associated with a sharp increase in A3G expression; however, this induction led to the accumulation of LMM A3G. Together, these results highlight the distinct inductive effects of select cytokines on A3G gene expression and A3G complex assembly that occur in natural cellular targets of HIV infection.

Apoptosis induced in HIV-1-exposed, resting CD4+T cells subsequent to signaling through homing receptors is Fas/Fas ligand-mediated

The hallmark of HIV-1 disease is the gradual disappearance of CD4+ T cells from the blood. The mechanism of this depletion, however, is still unclear. Evidence suggests that lymphocytes die in lymph nodes, not in blood, and that uninfected bystander cells are the predominant cells dying. Our and others' previous studies showed that the lymph node homing receptor, CD62 ligand (CD62L), and Fas are up-regulated on resting CD4+ T cells after HIV-1 binding and that these cells home to lymph nodes at an enhanced rate. During the homing process, signals are induced through various homing receptors, which in turn, induced many of the cells to undergo apoptosis after they entered the lymph nodes. The purpose of this study was to determine how the homing process induces apoptosis in HIV-1-exposed, resting CD4+ T cells. We found that signaling through CD62L up-regulated FasL. This resulted in apoptosis of only HIV-1-presignaled, resting CD4+ T cells, not normal CD4+ T cells. This homing receptor-induced apoptosis could be blocked by anti-FasL antibodies or soluble Fas, demonstrating that the Fas-FasL interaction caused the apoptotic event.

Host chemokine (C-C motif) ligand-2 (CCL2) is differentially regulated in HIV type 1 (HIV-1)-infected individuals

Several cytokines and chemokines including chemokine (C-C motif) ligand-2 (CCL2) are induced in HIV-1 infection. However, the impact of HIV-1 viremia on CCL2 regulation is largely unknown. We utilized a DNA oligonucleotide microarray covering 110 inflammatory genes. Five genes were induced by at least 2-fold in PBMCs of HIV-1 viremic (>100,000 RNA copies ml(-1)) as compared with aviremic (<50 RNA copies ml(-1)) individuals. These genes were CCL2, CXC chemokine ligand-10, IFN-gamma, GTP-cyclohydrolase-1 and C-C chemokine receptor-1. In addition to microarray data verification by real-time PCR, analysis of independent patient samples revealed a similar expression pattern. CCL2 was the most strongly regulated gene at mRNA level and its serum concentration was significantly elevated in viremic compared with aviremic and HIV-1 seronegative controls, indicating a positive correlation between viremia and CCL2. Flow cytometric studies demonstrated a higher percentage of CCL2-expressing CD14(+) monocytes in viremic compared with aviremic individuals. These results suggest a highly restricted modulation of host inflammatory gene response by HIV. Genes up-regulated in the viremic state, in particular CCL2, presumably serve as potential enhancing factors in HIV-1 replication, represented by high viral load in HIV-1 viremic patients. Inhibition of increased CCL2 production could provide a new therapeutic intervention in HIV-1 infection.

Multifunctional transcription factor YY1: a therapeutic target in human cancer?

The multifunctional transcription factor Yin Yang 1 (YY1) is a complex protein that has been shown to play pivotal roles in development, differentiation, cellular proliferation and apoptosis. It can act as a transcriptional repressor, an activator, or an initiator element binding protein that directs and initiates transcription of numerous cellular and viral genes. Because the expression and function of YY1 are known to be intimately associated with cell-cycle progression, the physiological significance of YY1 activity has recently been applied to models of cancer biology. Several lines of evidence imply that YY1 expression and/or activation is associated with tumourigenesis, in addition to its regulatory roles in normal biological processes. However, controversial results also raised and indicated that further studies are still needed to piece all of the seemingly contradictory data into a complete picture. On the basis of YY1 regulations and functions, novel drugs and specific treatment strategies may be developed with new therapeutic applications for tumour patients in the future.

Intracellular HIV-Tat expression induces IL-10 synthesis by the CREB-1 transcription factor through Ser133 phosphorylation and its regulation by the ERK1/2 MAPK in human monocytic cells

Human immunodeficiency virus (HIV)-Tat plays an important role in virus replication and in various aspects of host immune responses, including dysregulation of cytokine production. IL-10, an anti-inflammatory cytokine, is up-regulated during the course of HIV infection representing an important pathway by which HIV may induce immunodeficiency. Here we show that extracellular as well as intracellular Tat induced IL-10 expression in normal human monocytes and promonocytic THP-1 cells. The signaling pathways involved in the regulation of IL-10 production by endogenous Tat remain unknown. To understand the molecular mechanism underlying intracellular Tat-induced IL-10 transcription, we employed a retroviral expression system to investigate the role of MAPKs and the transcription factor(s) involved. Our results suggest that an inhibitor specific for the ERK1/2, PD98059, selectively blocked intracellular Tat-induced IL-10 expression in THP-1 cells. Furthermore, intracellular Tat activated the CREB-1 transcription factor through Ser(133) phosphorylation that was regulated by ERK MAPK as determined by IL-10 promoter analysis and gel shift assays. Overall, our results suggest that intracellular HIV-Tat induces IL-10 transcription by ERK MAPK-dependent CREB-1 transcription factor activation through Ser(133) phosphorylation.

Cohort- and time-specific associations of CTLA4 genotypes with HIV-1 disease progression

BACKGROUND

CTLA4 in the chromosome 2q33 region encodes cytotoxic T-lymphocyte (CTL) associated antigen 4, which downregulates CTL responses. We examined the relationships between common CTLA4 variants and several outcomes of HIV-1 infection in adults and adolescents.

METHODS

We studied 765 HIV-1-infected persons: 558 Caucasian seroconverters from three cohorts (MACS, ACS, and DCG) and 207 infected adolescents (mostly female) from another cohort (REACH) of mixed ethnicity. Single nucleotide polymorphisms in CTLA4 promoter (-1147C/T, -658C/T, -318C/T), coding sequence (49A/G) and the 3' untranslated region (CT60A/G) were resolved by PCR-based techniques. Repeated measures and survival analyses were used to test allelic and haplotypic associations with HIV-1 viral load (VL) and time to AIDS, respectively.

RESULTS

Individuals carrying -318T or the (-1147) T-(-318) T haplotype had elevated HIV-1 VL in MACS and REACH but reduced VL in DCG and ACS participants. Time-dependent associations of CTLA4-318T with VL were observed in MACS and REACH (P = 0.03-0.09). In Cox regression models adjusted for age and established contributory markers in CCR5 and HLA class I genes, CTLA4-318T was associated with rapid progression to AIDS in MACS (relative hazard 1.69; 95% confidence interval, 1.15-2.49; P < 0.01) as opposed to a non-significant slower disease progression in ACS and no appreciable association in DCG.

CONCLUSIONS

Association of CTLA4 genotypes with clinical and virological outcomes following HIV-1 infection appeared to vary with time and among the cohorts. Further analyses in conjunction with other biologically and positionally related genes, such as CD28 and ICOS, may help explain the disparate findings.

Membrane-derived microvesicles: important and underappreciated mediators of cell-to-cell communication

Normal and malignant cells shed from their surface membranes as well as secrete from the endosomal membrane compartment circular membrane fragments called microvesicles (MV). MV that are released from viable cells are usually smaller in size compared to the apoptotic bodies derived from damaged cells and unlike them do not contain fragmented DNA. Growing experimental evidence indicates that MV are an underappreciated component of the cell environment and play an important pleiotropic role in many biological processes. Generally, MV are enriched in various bioactive molecules and may (i) directly stimulate cells as a kind of 'signaling complex', (ii) transfer membrane receptors, proteins, mRNA and organelles (e.g., mitochondria) between cells and finally (iii) deliver infectious agents into cells (e.g., human immuno deficiency virus, prions). In this review, we discuss the pleiotropic effects of MV that are important for communication between cells, as well as the role of MV in carcinogenesis, coagulation, immune responses and modulation of susceptibility/infectability of cells to retroviruses or prions.

Kaposi's sarcoma-associated herpesvirus immune modulation: an overview

Kaposi's sarcoma-associated herpesvirus (KSHV) is the most recently discovered human herpesvirus. It is the aetiological agent of Kaposi's sarcoma (KS), a tumour frequently affecting AIDS patients not receiving treatment. KSHV is also a likely cause of two lymphoproliferative diseases: multicentric Castleman's disease and primary effusion lymphoma. The study of KSHV offers exciting challenges for understanding the mechanisms of virus pathogenesis, including those involved in establishing infection and dissemination in the host. To facilitate these processes, approximately one-quarter of KSHV genes encode cellular homologues or unique proteins that have immunomodulatory roles in cytokine production, apoptosis, cell signalling and the immunological synapse. The activities of these molecules are considered in the present review and the positions of their genes are mapped from a complete KSHV genome sequence derived from a KS biopsy. The understanding gained enables the significance of different components of the immune response in protection against KSHV infection to be evaluated. It also helps to unravel the complexities of cellular and immunological pathways and offers the potential for exploiting viral immunomodulators and derivatives in disease therapy.

Discovery of a piperidine-4-carboxamide CCR5 antagonist (TAK-220) with highly potent Anti-HIV-1 activity

We incorporated various polar groups into previously described piperidine-4-carboxamide CCR5 antagonists to improve their metabolic stability in human hepatic microsomes. Introducing a carbamoyl group into the phenyl ring of the 4-benzylpiperidine moiety afforded the less lipophilic compound 5f, which possessed both high metabolic stability and good inhibitory activity of HIV-1 envelope-mediated membrane fusion (IC(50) = 5.8 nM). Further optimization to increase potency led to the discovery of 1-acetyl-N-{3-[4-(4-carbamoylbenzyl)piperidin-1-yl]propyl}-N-(3-chloro-4-methylphenyl)piperidine-4-carboxamide (5m, TAK-220), which showed high CCR5 binding affinity (IC(50) = 3.5 nM) and potent inhibition of membrane fusion (IC(50) = 0.42 nM), as well as good metabolic stability. Compound 5m strongly inhibited the replication of CCR5-using HIV-1 clinical isolates in human peripheral blood mononuclear cells (mean EC(50) = 1.1 nM, EC(90) = 13 nM) and exhibited a good pharmacokinetic profile in monkeys (BA = 29%). This compound has been chosen as a clinical candidate for further development.

Mechanisms of apoptosis induction by the HIV-1 envelope

The envelope glycoprotein complex (Env) of human immunodeficiency virus-1 (HIV-1) can induce apoptosis by a cornucopia of distinct mechanisms. A soluble Env derivative, gp120, can kill cells through signals that are transmitted by chemokine receptors such as CXCR4. Cell surface-bound Env (gp120/gp41), as present on the plasma membrane of HIV-1-infected cells, can kill uninfected bystander cells expressing CD4 and CXCR4 (or similar chemokine receptors, depending on the Env variant) by at least three different mechanisms. First, a transient interaction involving the exchange of lipids between the two interacting cells ('the kiss of death') may lead to the selective death of single CD4-expressing target cells. Second, fusion of the interacting cells may lead to the formation of syncytia which then succumb to apoptosis in a complex pathway involving the activation of several kinases (cyclin-dependent kinase-1, Cdk1; checkpoint kinase-2, Chk2; mammalian target of rapamycin, mTOR; p38 mitogen-activated protein kinase, p38 MAPK; inhibitor of NF-kappaB kinase, IKK), as well as the activation of several transcription factors (NF-kappaB, p53), finally resulting in the activation of the mitochondrial pathway of apoptosis. Third, if the Env-expressing cell is at an early stage of imminent apoptosis, its fusion with a CD4-expressing target cell can precipitate the death of both cells, through a process that may be considered as contagious apoptosis and which does not involve Cdk1, mTOR, p38 nor p53, yet does involve mitochondria. Activation of some of the above- mentioned lethal signal transducers have been detected in patients' tissues, suggesting that HIV-1 may indeed trigger apoptosis through molecules whose implication in Env-induced killing has initially been discovered in vitro.

IL-18 gene promoter polymorphism is involved in HIV-1 infection in a Brazilian pediatric population

In our study, we identified a polymorphism (C-607A) in the promoter region of the IL-18 gene that shows different frequencies between human immunodeficiency virus (HIV)-1-infected children and healthy controls in a pediatric Brazilian population. The presence of the -607 C allele correlates to HIV-1 infection and confers an increased risk of infection in subjects carrying the single nucleotide polymorphism.

Hexapeptides that interfere with HIV-1 fusion peptide activity in liposomes block GP41-mediated membrane fusion

Upon receptor-mediated activation, the gp41 hydrophobic, conserved fusion peptide inserts into the target membrane and promotes the kind of perturbations required for the progression of the HIV-cell fusion reaction. Using a synthetic combinatorial library we have identified all d-amino acid hexapeptide sequences that inhibited the fusion peptide capacity of perturbing model membranes. Two hexapeptides that effectively inhibited the fusion peptide in these systems were subsequently shown to inhibit cell-cell fusion promoted by gp41 expressed at cell surfaces. These observations might be of importance for understanding the mechanisms underlying fusion peptide activity and suggest new strategies for screening compounds that target these viral sequences.

The Safety and Tolerability of Z-100 in Patients Infected with HIV-1

Z-100 is an extract of the Mycobacterium tuberculosis strain Aoyama B, which contains various polysaccharides. Aoyama B has previously been shown to induce a T helper 1-type cytokine response in various murine oncological models and has also demonstrated inhibitory activity against HIV-1 in vitro. This multicentre study primarily determined the safety of Z-100 in early HIV-1-infected patients who were treatment naive; were treatment experienced, but had elected to discontinue highly active antiretroviral therapy (HAART) 8 weeks or longer before the study; or were stable on their first or second HAART regimen for at least 12 weeks before the study. Thirty-two individuals participated in this study and self-injected either placebo, 20 μg or 40 μg Z-100 twice a week for 8 weeks. Z-100 was well tolerated and the safety profiles of the Z-100 treatment groups were not meaningfully different compared with the placebo group. Plasma levels of HIV-1 RNA were not statistically significantly different in any treatment group at the end of the treatment period. There were no statistically significant differences among the treatment groups in the change from baseline to week 8 for any of the biological endpoints including plasma levels of HIV-1 RNA; CD4+ and CD8+ T-cell counts; levels of macrophage inflammatory protein 1; soluble tumour necrosis factor receptor 1; C-reactive protein; interleukin-6; and granulocyte colony stimulating factor. Consequently, this trial demonstrates the safety of Z-100 in HIV-1 infected patients without evidence of any activity at the doses administered.

HIV-1 gp120-mediated apoptosis of T cells is regulated by the membrane tyrosine phosphatase CD45

The molecular mechanism of the human immunodeficiency virus type 1 (HIV-1) gp120-induced apoptosis of bystander T cells is not well defined. Here, we demonstrate that CD45, a key component of the T cell receptor pathway, plays a crucial role in apoptosis induced by HIV-1 gp120. We observed that HIV-1 gp120-induced apoptosis was significantly reduced in a CD45-deficient cell line and that reconstitution of CD45 in these cells restored gp120-induced apoptosis. However, expression of a chimeric protein containing only the intracellular phosphatase domain was not able to restore the apoptotic function in the CD45-negative clone, indicating an important role for the extracellular domain of CD45 in this function. The role of CD45 in gp120-induced apoptosis was further confirmed in T cell lines and peripheral blood mononuclear cells using a selective CD45 inhibitor as well as CD45-specific small interfering RNA. We also observed that gp120 treatment induced CD45 association with the HIV coreceptor CXCR4. Further elucidation of downstream signaling events revealed that CD45 modulates HIV-1 gp120-induced apoptosis by regulating Fas ligand induction and activation of the phosphoinositide 3-kinase/Akt pathway. These results suggest a novel CD45-mediated mechanism for the HIV envelope-induced apoptosis of T cells.

Appearance of immature/transitional B cells in HIV-infected individuals with advanced disease: correlation with increased IL-7

Progression of HIV disease is associated with the appearance of numerous B cell defects. We describe herein a population of immature/transitional B cells that is overly represented in the peripheral blood of individuals with advancing HIV disease. These B cells, identified by the expression of CD10, were unresponsive by proliferation to B cell receptor triggering and possessed a phenotype and an Ig diversity profile that confirmed their immature/transitional stage of differentiation. Consistent with an immature status, their lack of proliferation to B cell receptor triggering was reversed with CD40 ligand, but not B cell activation factor. Finally, levels of CD10 expression on B cells were directly correlated with serum levels of IL-7, suggesting that increased levels of IL-7 modulate human B cell maturation either directly or indirectly by means of a homeostatic effect on lymphopenia. Taken together, these data offer insight into human B cell development as well as B cell dysfunction in advanced HIV disease that may be linked to IL-7-dependent homeostatic events.

Virologic and host characteristics of human immunodeficiency virus type 1-infected pediatric long term survivors

BACKGROUND

There are limited data concerning determinants of varying clinical progression rates in human immunodeficiency virus type 1 (HIV-1)-infected children. Therefore, we sought to determine whether viral or host factors associated with nonprogressive HIV-1 infection in adults play a role in limiting progression of infection in 5 vertically infected youths, ages 12-18 years, who have displayed no signs of advanced HIV-1 disease or acquired immunodeficiency syndrome despite having received minimal treatment with antiretroviral drugs.

RESULTS

The 5 individuals, whom we characterize as long term survivors, have maintained low loads of HIV-1 RNA in plasma when compared to many of their peers, and have also maintained normal and stable CD4 T-lymphocyte numbers and percentages throughout their lives. Determination of their predominant HIV-1 sequences revealed that 4 of 5 patients harbor virus with markers of resistance to their therapy (one was never treated). Furthermore 2 harbored viral isolates that contained insertions in Gag or Vif that inhibit HIV-1 replication. Moreover, 2 were found to be heterozygous for the CCR2 polymorphism 64I, a genotype associated with slower progression to acquired immunodeficiency syndrome in adults. All 5 expressed the histocompatibility leukocyte antigen DQ1 and 2 had unusual DR/DQ1 phenotypes.

CONCLUSIONS

We believe that the limited antiretroviral therapy received by the long term survivors cannot solely account for their benign clinical status. Therefore, we conclude that other factors, including gene polymorphisms that affect viral replicative capacity, account for the long term survival in some, and deduce that, as in adults, no single factor (virologic or host) can account for this clinical phenotype in all cases.

Genomic approach of AIDS pathogenesis: exhaustive genotyping of the TNFR1 gene in a French AIDS cohort

Large-scale genomic studies in cohorts have been made possible for the last few years thanks to the progress of molecular biology and bioinformatics. This systematic approach allows a better understanding of the molecular mechanisms of disease development and as a consequence can contribute to the rational design of new diagnostic and therapeutic tools. We present here the exhaustive genotyping of a candidate gene, tumor necrosis factor receptor 1 (TNFR1), in the genetic of resistance to immunodeficiency virus (GRIV) AIDS cohort. This gene was chosen because it is likely to be involved in the apoptosis pathways of CD4+ and CD8+ T-cells during human immunodeficiency virus 1 (HIV-1) infection. Seven frequent polymorphisms were characterized in 319 HIV-1 seropositive patients from the GRIV cohort with extreme disease progression phenotypes, slow progression or rapid progression, and in 427 healthy controls. The TNFR1 gene locus does not appear to be part of any haploblock and contains only a small haploblock of two successive SNPs. One promoter SNP (TNFR1_17444594, position -581) and one intronic SNP (TNFR1_27223241, position +11511) gave weak positive signals of association (resp. P=0.03 and P=0.04) as well as two haplotypes. To our knowledge, this is the first genetic association study dealing with the TNFR1 gene in AIDS and the putative associations identified will need to be validated through other AIDS cohort analyses or by further biological experimentation.

On the Role of Interferon Regulatory Factors in HIV-1 Replication

Interferons (IFNs) are pleiotropic cytokines that possess several biological activities and play a central role in basic and applied research as mediators of antiviral and antigrowth responses, modulators of the immune system, and therapeutic agents against viral diseases and cancer. Interferon regulatory factors (IRFs) have been identified together with signal transducers and activators of transcription (STAT) from studies on the type I IFN as well as IFN-stimulated (ISG) gene regulation and signaling. IRFs constitute a family of transcriptional activators and repressors implicated in multiple biological processes including regulation of immune responses and host defence, cytokine signaling, cell growth regulation, and hematopoietic development. All members share a well-conserved DNA binding domain at the NH(2)-terminal region that recognizes similar DNA sequences, termed IRF element (IRF-E)/interferon-stimulated response element (ISRE), present on the promoter of target genes. Recently, a sequence homologous to the ISRE has been identified downstream from the 5' human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR). This sequence is a binding site for IRF-1 and IRF-2. Here we briefly summarize the role of IRFs in the regulation of HIV-1 LTR transcriptional activity and virus replication. The overall effect of IRFs on HIV-1 replication will also be discussed in the context of strategies carried out by the virus to counteract the IFN-mediated host defences both in active replication and during the establishment of viral latency.

The HIV infection and immune activation: "to fight and burn"

Immune activation, a normal immune reaction to pathogens, is now recognized as a major driving force of the CD4 T-cell depletion and immune disorders caused by HIV. By contrast, the natural hosts of its ancestor virus, simian immunodeficiency virus, have adapted to this virus by blocking immune activation and remaining healthy. This review will focus on evidence demonstrating how immune activation associated with HIV infection exhausts immune defenses to HIV as well as the immune system, thus leading to immunosenescence and immunodeficiency, and how treatment can disrupt this vicious and ultimately fatal circle.

HIV p17 reverses the anti-inflammatory activity of IL-4 on IL-15 stimulated monocytes and modulates their ability to secrete MIP-1 alpha

Monocytes play a central role in the immune system by producing and reacting to different soluble factors. Cytokine dysregulation is an hallmark in HIV-infected individuals and it is one of the most significant factors leading to impaired immunity in HIV/AIDS disease. This study investigates the possibility of modulation in the secretion of some inflammatory cytokines and chemokines induced by HIV p17 in monocytes. The results show that p17, while ineffective on resting monocytes, exerts an inflammatory action on IL-4 mediated inhibition of TNF-alpha and IFN-gamma production induced by IL-15 stimulation. In addition, p17 is able to reduce MIP-1alpha secretion, but unable to influence IL-6 production. The ability of HIV p17 to contribute to an altered pattern of secreted soluble factors might imply a key role for this viral protein in the development of AIDS pathogenesis.

Protective effects of IL4-589T and RANTES-28G on HIV-1 disease progression in infected Thai females

OBJECTIVE

To evaluate the effect of polymorphisms in interleukin-4 (IL4) and RANTES promoters on disease progression in HIV-1 infected Thais.

DESIGN

Antiretroviral (ARV) drug-free HIV-1 infected females from the prospective cohort.

METHODS

A total of 246 DNA samples were genotyped for IL4 and RANTES promoter polymorphisms by PCR-RFLP. Associations of genotype with HIV-1 disease progression were assessed with respect to baseline clinical data including plasma HIV-1 load, CD4 cell counts, and proportion of symptomatic/AIDS, and survival status during 3 years of follow-up.

RESULTS

Patients with homozygous IL4-589T allele showed a significantly lower HIV-1 viral load (P = 0.005) and a higher CD4 cell count (P = 0.003) than the other patients with heterozygous IL4-589C/T or homozygous IL4-589C allele. Kaplan-Meier analysis demonstrated an apparent but insignificant trend towards better survival in homozygous IL4-589T patients. On the other hand, patients with RANTES-28G allele showed a significantly better survival while those with RANTES In1.1C allele without RANTES-28G showed a significantly poorer survival compared with those who did not possess either RANTES In1.1C or RANTES-28G (P = 0.02), although those polymorphisms only weakly associated with baseline viral load and CD4 cell counts.

CONCLUSIONS

Our results implicate the significant protective effect of IL4-589T and RANTES-28G on HIV disease progression in Thais. In contrast, RANTES In1.1C without RANTES-28G had an accelerating effect on HIV disease progression.