Human Immunodeficiency Virus Isolates Research Articles

Top three reasons to come to Kobe for the 14th International Congress of Immunology

Top three reasons to come to Kobe for the 14th International Congress of Immunology

A Novel Yeast-Based Recombination Method to Clone and Propagate Diverse HIV-1 Isolates

Replication studies on human immunodeficiency virus 1 (HIV-1) rely on a few laboratory strains that are divergent from dominant HIV-1 subtypes in the epidemic. Several phenotypic differences between diverse HIV-1 isolates and subtypes could affect vaccine development and treatment, but this research field lacks robust cloning/virus production systems to study drug sensitivity, replication kinetics, or to develop personalized vaccines. Extreme HIV-1 heterogeneity leaves few restriction enzyme sites for bacterial cloning strategies. In this study, we describe an alternative approach that involves direct introduction of any HIV-1 coding regions (e.g., any gene from a patient sample) into an HIV-1 DNA vector using yeast recombination. This technique uses positive and negative selectable markers in yeast and avoids the need for purification and screening of the DNA substrates and cloning products. Replication-competent virus is then produced from a modified mammalian 293T packaging cell line transfected with this yeast-derived HIV-1 vector. Although HIV-1 served as the prototype, this cloning strategy is now being developed for other diverse virus species such as hepatitis C virus and influenza virus.

HIV Diversity in Venezuela: Predominance of HIV Type 1 Subtype B and Genomic Characterization of Non-B Variants

The aim of this study was the analysis of human immunodeficiency virus (HIV) diversity in Venezuela, and the characterization of variants other than subtype B. A total of 425 HIV isolates, collected between 2003 and 2008, were analyzed. The sequence of at least one genomic region (Pol, Env, Vif, or Nef ) was available for all of them and at least two genomic regions were analyzed in 46% of them. From the 425 HIV isolates analyzed, 421 (99.1%) were classified as HIV-1 subtype B. The four non-subtype B isolates correspond to one subtype C, one recombinant AG, and two HIV-2 isolates. This study shows that HIV-1 subtype B is still highly predominant in Venezuela. Whereas some sporadic cases of other HIV types can be found, they do not seem to have disseminated to the present.

On Viruses, Discovery, and Recognition

This year's Nobel Prize in Physiology or Medicine rewards the discoverers of two viruses that cause major afflictions of humankind. Identifying human papilloma virus (HPV) and human immunodeficiency virus (HIV) might now appear to have been simple, but the way forward was far from obvious at the time.

The early days of the HIV-AIDS epidemic in the USA

The work of epidemiologists before the isolation of human immunodeficiency virus 25 years ago demonstrates the power of the epidemiological method to gain an understanding of disease pathogenesis.

The Antiherpetic Drug Acyclovir Inhibits HIV Replication and Selects the V75I Reverse Transcriptase Multidrug Resistance Mutation

The antiviral drug acyclovir is a guanosine nucleoside analog that potently inhibits herpes simplex virus (HSV) replication. Acyclovir treatment in patients coinfected with HSV and human immunodeficiency virus (HIV) has been observed to alter disease course and decrease HIV viral load, a finding that has been attributed to indirect effects of HSV suppression on HIV replication. Based on this hypothesis, several clinical studies have recently investigated the use of acyclovir for treatment of patients coinfected with HSV and HIV or for prophylaxis against HIV transmission. In this report, we use a single round HIV infectivity assay to show that acyclovir directly inhibits HIV infection with an IC50 of approximately 5 microm. The target of acyclovir in HIV-infected cells is validated as HIV reverse transcriptase (RT) by the emergence of the RT variant V75I under the selective pressure of acyclovir. The V75I mutation is part of the multidrug resistance pathway that enhances viral resistance to many of the best RT inhibitors approved for the treatment of HIV. Biochemical analyses demonstrate that acyclovir triphosphate is a chain terminator substrate for HIV RT and can compete with dGTP for incorporation into DNA. Although acyclovir may prove a useful lead for development of new HIV treatments, the selection of resistant mutants raises a cautionary note to the use of acyclovir monotherapy in patients coinfected with HSV and HIV.

Candidate Microbicide PPCM Blocks Human Immunodeficiency Virus Type 1 Infection in Cell and Tissue Cultures and Prevents Genital Herpes in a Murine Model

A structurally novel candidate microbicide, PPCM, which is formed from the reaction of D,L-mandelic acid with sulfuric acid, provides activity against human immunodeficiency virus (HIV) and herpes simplex virus (HSV) and is not cytotoxic. The objectives of the current studies were to comprehensively evaluate the activity of PPCM in cell and explant cultures, explore the possibility of combining PPCM with HIV-specific reverse transcriptase inhibitors, and evaluate the efficacy of a formulated gel against genital herpes in a murine model. PPCM inhibited infection by laboratory and clinical R5 and X4 clade B and clade C HIV strains in cell culture. Ectocervical and endocervical tissue explants exposed to HIV-1(BaL) in the presence of PPCM were protected (50% inhibitory concentrations [IC(50)] of 3.9 microg/ml for ectocervix and 3.1 microg/ml for endocervix), and transfer of virus to target T cells via migratory cells was significantly impaired (IC(50) of 35.7 microg/ml for ectocervix and 54.6 microg/ml for endocervix). The drug also blocked infection by cell-associated virus. Combinations of PPCM with UC-781 or PMPA in vitro exhibited additive anti-HIV activity. PPCM was incorporated into stable, low-pH gel formulations at concentrations of 0.4% and 4%. Both gels prevented genital herpesvirus infection in mice, even when virus was introduced in human seminal plasma. The abilities of PPCM to inhibit primary HIV isolates, reduce infection by cell-associated virus, and transfer of HIV from migratory to T cells, combined with the complete protection provided by formulated gel against genital herpes, indicate that this drug is an excellent candidate for inclusion in a combination microbicide and would provide protection against both HIV and HSV.

Sulfated β-Glucan Derived from Oat Bran with Potent Anti-HIV Activity

China is a major producer of oats; the annual harvested area of 350,000 ha yields approximately 465,000 tons, giving an average yield of 1.33 tons/ha. The bran is not used for animal feed as it is of poor digestibility and low nutritive content and is considered a waste byproduct. Therefore, it is advantageous to produce a value-added product from the bran. We extracted the native polysaccharide, a linear (1-3)-, (1-4)-linked beta-glucan (OBG) from the oat bran and synthesized a sulfated derivative OBGS containing 36.5% sulfate. OBGS had potent activity against a primary isolate of human immunodeficiency virus (HIV-1) in peripheral blood mononuclear cells at a concentration (EC(50)=5.98 x 10(-4) microM) approximately 15,000 times below its cytotoxic concentration. OBGS was also active postinfection (EC(50)=5.3 x 10(-4) microM) and protected pretreated peripheral mononuclear cells (EC(50)=5.2 x 10(-2) microM) washed free of the compounds prior to infection. Thus, OBGS has potential as a vaginal microbicide and is the first such report for oat bran derived sulfated beta-glucan.

Infection of Macrophages and Dendritic Cells with Primary R5-Tropic Human Immunodeficiency Virus Type 1 Inhibited by Natural Polyreactive Anti-CCR5 Antibodies Purified from Cervicovaginal Secretions

Heterosexual contact is the primary mode of human immunodeficiency virus (HIV) type 1 (HIV-1) transmission worldwide. The chemokine receptor CCR5 is the major coreceptor that is associated with the mucosal transmission of R5-tropic HIV-1 during sexual intercourse. The CCR5 molecule is thus a target for antibody-based therapeutic strategies aimed at blocking HIV-1 entry into cells. We have previously demonstrated that polyreactive natural antibodies (NAbs) from therapeutic preparations of immunoglobulin G and from human breast milk contain NAbs directed against CCR5. Such antibodies inhibit the infection of human macrophages and T lymphocytes by R5-tropic isolates of HIV in vitro. In the present study, we demonstrate that human immunoglobulins from the cervicovaginal secretions of HIV-seronegative or HIV-seropositive women contain NAbs directed against the HIV-1 coreceptor CCR5. Natural affinity-purified anti-CCR5 antibodies bound to CCR5 expressed on macrophages and dendritic cells and further inhibited the infection of macrophages and dendritic cells with primary and laboratory-adapted R5-tropic HIV but not with X4-tropic HIV. Natural anti-CCR5 antibodies moderately inhibited R5-tropic HIV transfer from monocyte-derived dendritic cells to autologous T cells. Our results suggest that mucosal anti-CCR5 antibodies from healthy immunocompetent donors may hamper the penetration of HIV and may be suitable for use in the development of novel passive immunotherapy regimens in specific clinical settings of HIV infection.

Active β-Catenin Signaling Is an Inhibitory Pathway for Human Immunodeficiency Virus Replication in Peripheral Blood Mononuclear Cells

The Wnt/beta-catenin pathway is involved in cell functions governing development and disease. In modeling postentry restriction of human immunodeficiency virus (HIV) replication in astrocytes, we reported that part of this natural resistance to productive replication of HIV in astrocytes involved expression of proteins of the Wnt/beta-catenin signaling pathway. We determined here whether induction of beta-catenin signaling in peripheral blood mononuclear cells (PBMCs) can modulate HIV replication. Given that lithium is an inducer of beta-catenin signaling, we used it as a tool to determine the impact of beta-catenin signaling on HIV replication in PBMCs. We demonstrated that lithium inhibited the replication of T-tropic and primary isolates of HIV by >90% and did so in noncytotoxic/noncytostatic concentrations and in a beta-catenin-dependent manner. Specifically, inhibiting beta-catenin signaling by transfection of dominant-negative mutant constructs to either T-cell factor 4, the downstream effector of Wnt signaling, or beta-catenin, the central mediator of this pathway, abrogated the ability of lithium to inhibit HIV replication. Moreover, when Wnt/beta-catenin signaling was inhibited, the level of HIV replication was enhanced by fourfold. To confirm the in vivo relevance of the beta-catenin pathway in repressing HIV replication, we evaluated HIV-positive antiretroviral therapy-naive patients who were on lithium therapy. These patients demonstrated a reduction in viral load, which increased as the dose of lithium was reduced. Collectively, these data indicate that beta-catenin signaling is an intrinsic molecular pathway restricting HIV replication in PBMCs.

A formylpeptide receptor, FPRL1, acts as an efficient coreceptor for primary isolates of human immunodeficiency virus

BackgroundMore than 10 members of seven-transmembrane G protein-coupled receptors (GPCRs) have been shown to work as coreceptors for human immunodeficiency virus type 1 (HIV-1), HIV type 2 (HIV-2), and simian immunodeficiency viruses (SIVs). As a common feature of HIV/SIV coreceptors, tyrosine residues are present with asparagines, aspartic acids or glutamic acids in the amino-terminal extracellular regions (NTRs).We noticed that a receptor for N-formylpeptides, FPRL1, also contains two tyrosine residues accompanied by glutamic acids in its NTR. It was reported that monocytes expressing CCR5 and FPRL1 in addition to CD4 are activated by treatment with ligands or agonists of FPRL1. Activated monocytes down-modulate CCR5 and become resistant to infection by HIV-1 strains. Thus, FPRL1 plays important roles in protection of monocyptes against HIV-1 infection. However, its own coreceptor activity has not been elucidated yet. In this study, we examined coreceptor activities of FPRL1 for HIV/SIV strains including primary HIV-1 isolates.ResultsA CD4-transduced human glioma cell line, NP-2/CD4, is strictly resistant to HIV/SIV infection. We have reported that when NP-2/CD4 cells are transduced with a GPCR having coreceptor activity, the cells become susceptible to HIV/SIV strains. When NP-2/CD4 cells were transduced with FPRL1, the resultant NP-2/CD4/FPRL1 cells became markedly susceptible to some laboratory-adapted HIV/SIV strains. We found that FPRL1 is also efficiently used as a coreceptor by primary HIV-1 isolates as well as CCR5 or CXCR4.Amino acid sequences linked to the FPRL1 use could not be detected in the V3 loop of the HIV-1 Env protein. Coreceptor activities of FPRL1 were partially blocked by the forymyl-Met-Leu-Phe (fMLF) peptide.ConclusionWe conclude that FPRL1 is a novel and efficient coreceptor for HIV/SIV strains. FPRL1 works as a bifunctional factor in HIV-1 infection. Namely, the role of FPRL1 in HIV-1 infection is protective and/or promotive in different conditions. FPRL1 has been reported to be abundantly expressed in the lung, spleen, testis, and neutrophils. We detected mRNA expression of FPRL1 in 293T (embryonal kidney cell line), C8166 (T cell line), HOS (osteosarcoma cell line), Molt4#8 (T cell line), U251MG (astrocytoma cell line), U87/CD4 (CD4-transduced glioma cell line), and peripheral blood lymphocytes. Roles of FPRL1 in HIV-1 infection in vivo should be further investigated.

Blind spots in the epidemiology of HIV in black Americans.

In the USA, annual rates of new human immunodeficiency virus (HIV)/AIDS diagnoses are seven and 21 times higher in black men and women, respectively, than in whites. Epidemiological inquiry on this disparity has chiefly focused on contextual factors; such emphasis has eclipsed study of direct HIV vectors. The US Centers for Disease Control and Prevention recently announced its intention to curb HIV propagation in black communities, recommending culturally appropriate HIV/AIDS strategies. Contemplated societal interventions should be informed by data evaluating more direct (and under-assessed) HIV transmission vectors, specifically anal intercourse and unsuspected blood exposures. This recommendation involves tracing sexual and non-sexual contacts of recently infected persons and uninfected controls, coupled with DNA sequencing of HIV isolates. Public health authorities do not know the extent to which unmeasured yet plausible HIV transmission vectors can account for ethnic disparities. Appropriate prevention strategies depend critically on direct, rather than ecologic, evidence.

The First Hypervariable Region of the gp120 Env Glycoprotein Defines the Neutralizing Susceptibility of Heterologous Human Immunodeficiency Virus Type 1 Isolates to Neutralizing Antibodies Elicited by the SF162gp140 Immunogen

Current vaccine efforts to elicit cross-reactive neutralizing antibodies (NAbs) against human immunodeficiency virus (HIV) focus on the engineering of soluble mimetics of the trimeric HIV Env glycoprotein (commonly termed gp140 immunogens). Such immunogens are thought to be more effective than previously tested monomeric gp120 immunogens at eliciting cross-reactive NAbs. Still, the breadth of neutralizing antibody responses elicited by gp140 immunogens is narrow. Understanding why antibodies elicited by gp140 immunogens fail to neutralize a wide range of heterologous primary HIV isolates is necessary for improving the design of such immunogens. We previously reported that antibodies elicited in macaques by SF162 Env-derived gp140 immunogens fail to neutralize several heterologous "neutralization-resistant" primary HIV type 1 isolates, such as JRFL, ADA, and YU2. Here we show that by replacing the V1 region of Env on these heterologous viruses with that of SF162, we render them highly susceptible to neutralization by the SF162gp140-elicited antibodies. We observed that viral neutralization was mediated not only by vaccine-elicited anti-V1 but also by anti-V3 antibodies and antibodies directed against as yet unidentified Env regions, depending on the heterologous Env background. Our study indicates that common neutralization epitopes are differentially exposed on diverse primary HIV isolates and that the V1 loop contributes to this differential exposure. Therefore, the antibody responses elicited by soluble gp140 immunogens will have to overcome several distinct obstacles in order to neutralize diverse primary HIV isolates.

The minimal fusion peptide of simian immunodeficiency virus corresponds to the 11 first residues of gp32

We had previously predicted successfully the minimal fusion peptides (FPs) of the human immunodeficiency virus 1 (HIV-1) gp41 and the bovine leukemia virus (BLV) gp30 using an original approach based on the obliquity/fusogenicity relationship of tilted peptides. In this paper, we have used the same method to predict the shortest FP capable of inducing optimal fusion in vitro of the simian immunodeficiency virus (SIV) mac isolate and of other SIVs and human immunodeficiency virus (HIV-2) isolates. In each case, the 11-residue-long peptide was predicted as the minimal FP. For the SIV mac isolate, liposome lipid-mixing and leakage assays confirmed that this peptide is the shortest peptide inducing optimal fusion in vitro, being therefore the minimal FP. These results are another piece of evidence that the tilted properties of FPs are important for the fusion process and that our method can be used to predict the minimal FPs of other viruses.

Novel TRIM5 Isoforms Expressed byMacaca nemestrina

The TRIM5 family of proteins contains a RING domain, one or two B boxes, and a coiled-coil domain. The TRIM5alpha isoform also encodes a C-terminal B30.2(SPRY) domain, differences within which define the breadth and potency of TRIM5alpha-mediated retroviral restriction. Because Macaca nemestrina animals are susceptible to some human immunodeficiency virus (HIV) isolates, we sought to determine if differences exist in the TRIM5 gene and transcripts of these animals. We identified a two-nucleotide deletion (Delta2) in the transcript at the 5' terminus of exon 7 in all M. nemestrina TRIM5 cDNA clones examined. This frameshift results in a truncated protein of 300 amino acids lacking the B30.2(SPRY) domain, which we have named TRIM5theta. This deletion is likely due to a single nucleotide polymorphism that alters the 3' splice site between intron 6 and exon 7. In some clones, a deletion of the entire 27-nucleotide exon 7 (Deltaexon7) resulted in the restoration of the TRIM5 open reading frame and the generation of another novel isoform, TRIM5eta. There are 18 amino acid differences between M. nemestrina TRIM5eta and Macaca mulatta TRIM5alpha, some of which are at or near locations previously shown to affect the breadth and potency of TRIM5alpha-mediated restriction. Infectivity assays performed on permissive CrFK cells stably transduced with TRIM5eta or TRIM5theta show that these isoforms are incapable of restricting either HIV type 1 (HIV-1) or simian immunodeficiency virus infection. The expression of TRIM5 alleles incapable of restricting HIV-1 infection may contribute to the previously reported increased susceptibility of M. nemestrina to HIV-1 infection in vivo.

HIV management: emerging therapies in an evolving field

AbstractEfforts to combat the Human Immunodeficiency Virus (HIV) began in earnest in the late 1980s following the identification and isolation of HIV as the pathogen of the Acquired Immunodeficiency Syndrome (AIDS). Multiple‐drug therapy, known as highly active antiretroviral therapy (HAART), became available in the 1990s and has become the backbone of HIV medication treatment. Understanding of how to optimise its use and effectiveness continues to grow, and is reflected by the emergence of novel agents and new classes of drugs. Copyright © 2007 Wiley Interface Ltd

In Vitro Antiviral Activity of the Novel, Tyrosyl-Based Human Immunodeficiency Virus (HIV) Type 1 Protease Inhibitor Brecanavir (GW640385) in Combination with Other Antiretrovirals and against a Panel of Protease Inhibitor-Resistant HIV

Brecanavir, a novel tyrosyl-based arylsulfonamide, high-affinity, human immunodeficiency virus type 1 (HIV-1) protease inhibitor (PI), has been evaluated for anti-HIV activity in several in vitro assays. Preclinical assessment of brecanavir indicated that this compound potently inhibited HIV-1 in cell culture assays with 50% effective concentrations (EC(50)s) of 0.2 to 0.53 nM and was equally active against HIV strains utilizing either the CXCR4 or CCR5 coreceptor, as was found with other PIs. The presence of up to 40% human serum decreased the anti-HIV-1 activity of brecanavir by 5.2-fold, but under these conditions the compound retained single-digit nanomolar EC(50)s. When brecanavir was tested in combination with nucleoside reverse transcriptase inhibitors, the antiviral activity of brecanavir was synergistic with the effects of stavudine and additive to the effects of zidovudine, tenofovir, dideoxycytidine, didanosine, adefovir, abacavir, lamivudine, and emtricitabine. Brecanavir was synergistic with the nonnucleoside reverse transcriptase inhibitor nevirapine or delavirdine and was additive to the effects of efavirenz. In combination with other PIs, brecanavir was additive to the activities of indinavir, lopinavir, nelfinavir, ritonavir, amprenavir, saquinavir, and atazanavir. Clinical HIV isolates from PI-experienced patients were evaluated for sensitivity to brecanavir and other PIs in a recombinant virus assay. Brecanavir had a <5-fold increase in EC(50)s against 80% of patient isolates tested and had a greater mean in vitro potency than amprenavir, indinavir, lopinavir, atazanavir, tipranavir, and darunavir. Brecanavir is by a substantial margin the most potent and broadly active antiviral agent among the PIs tested in vitro.

Peptide mimotopes selected with HIV‐1‐blocking monoclonal antibodies against CCR5 represent motifs specific for HIV‐1 entry

CCR5 is a chemokine receptor that mediates entry of human immunodeficiency virus-1 (HIV-1). Two monoclonal antibodies (mAbs) that block HIV-1 entry, 3A9 and 5C7, were used to select peptide mimotopes of sequences on CCR5 from phage displayed peptide libraries. The selected mimotofpes comprised motifs at the N-terminus and on the first and third extracellular loops (ECL1 and ECL3) of CCR5. Amino acids in these motifs were exchanged for alanines by site-directed mutagenesis (sdm) in the cDNA for human CCR5. Ensuing effects on antibody binding to CCR5, cellular entry of HIV-1 and chemokine-induced signalling were analysed by transfection of mutant cDNAs into HEK293.CD4 cells. For both mAbs, fluorescence-activated cell sorting analysis was used to define overlapping conformational epitopes on CCR5 at the N-terminus, on ECL1 and ECL3. Mutation of the N-terminal motif 10YD11 prevented HIV-1 entry into transfected cells as judged by single round infection assays with R5 and R5X4 HIV-1 isolates, as did mutation of the motif 96FG97 in ECL1, whereas mutation of the motif 274RLD276 in ECL3 had only a minor effect. None of the motifs in CCR5 relevant to HIV-1 entry disrupted chemokine-induced signalling. Thus, peptide mimotopes of conformational contact sites of CCR5 with the paratope of mAbs 3A9 and 5C7 represent sites on CCR5 that are essential for HIV-1 entry. Structural knowledge of these mimotopes could help elucidate the nature of the interaction between CCR5 and HIV-1, and thus the derivation of specific inhibitors of entry of HIV-1 into susceptible cells without interference with chemokine signalling.

Molecular Umbrellas: a Novel Class of Candidate Topical Microbicides To Prevent Human Immunodeficiency Virus and Herpes Simplex Virus Infections

Molecular umbrella compounds may function as novel topical microbicides to prevent human immunodeficiency virus (HIV) and herpes simplex virus (HSV) infections. In a preliminary structure-activity investigation, one umbrella compound, designated Spm8CHAS, was identified which inhibited both HIV and HSV infections with no cellular toxicity. The objectives of the current studies were to define its spectrum of antiviral activity, characterize its mechanism of action, and explore the possibility of combining Spm8CHAS with HIV-specific reverse transcriptase inhibitors. Spm8CHAS inhibited infections by laboratory and clinical R5 and X4 clade B and clade C HIV strains in cell culture. Ectocervical tissue explants exposed to HIV-1(BaL) in the presence of Spm8CHAS were completely protected (50% inhibitory concentration [IC(50)], 13.6 microg/ml), and transfer of virus to target T cells via migratory cells was abolished (IC(50), 3.8 microg/ml). Spm8CHAS inhibited HSV-2 infection of epithelial cells 10,000-fold if present throughout the infection. Notably, adding Spm8CHAS to cultures following HSV entry significantly reduced viral infection, indicating that the drug also acts postentry. Subsequent studies indicated that Spm8CHAS blocks cell-to-cell spread of HSV. Confocal microscopy using a fluorescently labeled analog of Spm8CHAS demonstrated that this conjugate crosses the plasma cell membrane and is transported to the nucleus. Combinations of Spm8CHAS with UC-781 or 9-[R-2-(phosphonylmethoxy)propyl] adenine monohydrate in vitro exhibited additive anti-HIV activity with preserved anti-HSV activity. The abilities of Spm8CHAS to inhibit primary isolates of HIV, block HSV infection postentry, and cross cell membranes support the development of a combination microbicide containing Spm8CHAS with an HIV-specific reverse transcriptase inhibitor to prevent both HIV and HSV infections by multiple mechanisms.

Activation of JNK-dependent Pathway Is Required for HIV Viral Protein R-induced Apoptosis in Human Monocytic Cells: INVOLVEMENT OF ANTIAPOPTOTIC BCL2 AND c-IAP1 GENES

Human immunodeficiency virus (HIV) accessory protein viral protein R (Vpr) plays a key role in virus replication and induces cell cycle arrest and apoptosis in various cell types including T cells and neuronal and tumor cells following infection with Vpr-expressing HIV isolates or exposure to the extracellular Vpr protein. The C-terminal Vpr peptide encompassing amino acids 52-96 (Vpr-(52-96)) is required for exerting the apoptotic effects, whereas the N-terminal Vpr-(1-45) peptide is responsible for virus transcription. We demonstrate that Vpr-(52-96) induced apoptosis in human promonocytic THP-1 cells and primary monocytes through the mitochondrial pathway in a caspase-dependent manner. To understand the regulation of Vpr-induced apoptosis, we investigated the signaling pathways, particularly the MAPKs, and the transcription factors involved. Although both Vpr-(52-96) and Vpr-(1-45) peptides induced phosphorylation of all the three members of the MAPKs, Vpr-(52-96)-activated JNK selectively induced apoptosis in monocytic cells through the mitochondrial pathway as determined by using JNK inhibitors SP60025, dexamethasone, curcumin, and JNK-specific small interfering RNAs. Furthermore Vpr-(52-96)-induced apoptosis was mediated by inhibition of downstream antiapoptotic Bcl2 and c-IAP1 genes whose expression could be restored following pretreatment with JNK-specific inhibitors. Overall the results suggest that Vpr-(52-96)-activated JNK plays a key role in inducing apoptosis through the down-regulation of antiapoptotic Bcl2 and c-IAP1 genes.