Human Immunodeficiency Virus Type 1 Clade Research Articles

Identification of a novel first-generation HIV-1 circulating recombinant form (CRF152_DG) among people living with HIV in Karachi, Pakistan.

In Pakistan, the genetic diversity of human immunodeficiency virus type 1 (HIV-1) is becoming increasingly complex, compared to the early years of the epidemic that started after the detection of the first cases of HIV-1 in 1987 in Karachi. Based on the available molecular studies, two dominant HIV-1 clades, sub-subtype A1 and CRF02_AG, have been found to co-circulate with other clades, namely B, C, D, G, CRF01_AE, CRF35_A1D, and CRF56_cpx, in various urban areas of Pakistan. Several novel recombinant forms have also been detected. This first report of CRF152_DG highlights the complex nature of the HIV epidemic in Pakistan and emphasizes the importance of continual molecular surveillance (ideally based on whole-genome sequences) of HIV.

Glycan Profiles of gp120 Protein Vaccines from Four Major HIV-1 Subtypes Produced from Different Host Cell Lines under Non-GMP or GMP Conditions.

Envelope (Env) glycoprotein of human immunodeficiency virus type 1 (HIV-1) is an important target for the development of an HIV vaccine. Extensive glycosylation of Env is an important feature that both protects the virus from antibody responses and serves as a target for some highly potent broadly neutralizing antibodies. Therefore, analysis of glycans on recombinant Env proteins is highly significant. Here, we present glycosylation profiles of recombinant gp120 proteins from four major clades of HIV-1 (A, B, C, and AE), produced either as research-grade material in 293 and CHO cells or as two independent lots of clinical material under good manufacturing practice (GMP) conditions. Almost all potential N-linked glycosylation sites were at least partially occupied in all proteins. The occupancy rates were largely consistent among proteins produced under different conditions, although a few sites showed substantial variability even between the two GMP lots. Our data confirmed previous studies in the field, showing an abundance of oligomannose on Env protein, with 40 to 50% of glycans being Man5 to Man9 on all four proteins under all production conditions. Overall, the differences in occupancy and glycan forms among different Env subtypes produced under different conditions were less dramatic than anticipated, and antigenicity analysis with a panel of six monoclonal antibodies, including antibodies that recognize glycan forms, showed that all four gp120s maintained their antibody-binding profiles. Such findings have major implications for the final production of a clinical HIV vaccine with Env glycoprotein components.IMPORTANCE HIV-1 Env protein is a major target for the development of an HIV-1 vaccine. Env is covered with a large number of sugar-based glycan forms; about 50% of the Env molecular weight is composed of glycans. Glycan analysis of recombinant Env is important for understanding its roles in viral pathogenesis and immune responses. The current report presents the first extensive comparison of glycosylation patterns of recombinant gp120 proteins from four major clades of HIV-1 produced in two different cell lines, grown either under laboratory conditions or at 50-liter GMP scale in different lots. Information learned in this study is valuable for the further design and production of HIV-1 Env proteins as the critical components of HIV-1 vaccine formulations.

Alkyl Amine Bevirimat Derivatives Are Potent and Broadly Active HIV-1 Maturation Inhibitors.

Concomitant with the release of human immunodeficiency virus type 1 (HIV-1) particles from the infected cell, the viral protease cleaves the Gag polyprotein precursor at a number of sites to trigger virus maturation. We previously reported that a betulinic acid-derived compound, bevirimat (BVM), blocks HIV-1 maturation by disrupting a late step in protease-mediated Gag processing: the cleavage of the capsid-spacer peptide 1 (CA-SP1) intermediate to mature CA. BVM was shown in multiple clinical trials to be safe and effective in reducing viral loads in HIV-1-infected patients. However, naturally occurring polymorphisms in the SP1 region of Gag (e.g., SP1-V7A) led to a variable response in some BVM-treated patients. The reduced susceptibility of SP1-polymorphic HIV-1 to BVM resulted in the discontinuation of its clinical development. To overcome the loss of BVM activity induced by polymorphisms in SP1, we carried out an extensive medicinal chemistry campaign to develop novel maturation inhibitors. In this study, we focused on alkyl amine derivatives modified at the C-28 position of the BVM scaffold. We identified a set of derivatives that are markedly more potent than BVM against an HIV-1 clade B clone (NL4-3) and show robust antiviral activity against a variant of NL4-3 containing the V7A polymorphism in SP1. One of the most potent of these compounds also strongly inhibited a multiclade panel of primary HIV-1 isolates. These data demonstrate that C-28 alkyl amine derivatives of BVM can, to a large extent, overcome the loss of susceptibility imposed by polymorphisms in SP1.

Origin and Population Dynamics of a Novel HIV-1 Subtype G Clade Circulating in Cape Verde and Portugal

The human immunodeficiency virus type 1 (HIV-1) subtype G is the most prevalent and second most prevalent HIV-1 clade in Cape Verde and Portugal, respectively; but there is no information about the origin and spatiotemporal dispersal pattern of this HIV-1 clade circulating in those countries. To this end, we used Maximum Likelihood and Bayesian coalescent-based methods to analyze a collection of 578 HIV-1 subtype G pol sequences sampled throughout Portugal, Cape Verde and 11 other countries from West and Central Africa over a period of 22 years (1992 to 2013). Our analyses indicate that most subtype G sequences from Cape Verde (80%) and Portugal (95%) branched together in a distinct monophyletic cluster (here called GCV-PT). The GCV-PT clade probably emerged after a single migration of the virus out of Central Africa into Cape Verde between the late 1970s and the middle 1980s, followed by a rapid dissemination to Portugal a couple of years later. Reconstruction of the demographic history of the GCV-PT clade circulating in Cape Verde and Portugal indicates that this viral clade displayed an initial phase of exponential growth during the 1980s and 1990s, followed by a decline in growth rate since the early 2000s. Our data also indicate that during the exponential growth phase the GCV-PT clade recombined with a preexisting subtype B viral strain circulating in Portugal, originating the CRF14_BG clade that was later disseminated to Spain and Cape Verde. Historical and recent human population movements between Angola, Cape Verde and Portugal probably played a key role in the origin and dispersal of the GCV-PT and CRF14_BG clades.

Spatiotemporal dynamics of the HIV-1 subtype G epidemic in West and Central Africa.

The human immunodeficiency virus type 1 (HIV-1) subtype G is the second most prevalent HIV-1 clade in West Africa, accounting for nearly 30% of infections in the region. There is no information about the spatiotemporal dynamics of dissemination of this HIV-1 clade in Africa. To this end, we analyzed a total of 305 HIV-1 subtype G pol sequences isolated from 11 different countries from West and Central Africa over a period of 20 years (1992 to 2011). Evolutionary, phylogeographic and demographic parameters were jointly estimated from sequence data using a Bayesian coalescent-based method. Our analyses indicate that subtype G most probably emerged in Central Africa in 1968 (1956–1976). From Central Africa, the virus was disseminated to West and West Central Africa at multiple times from the middle 1970s onwards. Two subtype G strains probably introduced into Nigeria and Togo between the middle and the late 1970s were disseminated locally and to neighboring countries, leading to the origin of two major western African clades (GWA-I and GWA-II). Subtype G clades circulating in western and central African regions displayed an initial phase of exponential growth followed by a decline in growth rate since the early/middle 1990s; but the mean epidemic growth rate of GWA-I (0.75 year−1) and GWA-II (0.95 year−1) clades was about two times higher than that estimated for central African lineages (0.47 year−1). Notably, the overall evolutionary and demographic history of GWA-I and GWA-II clades was very similar to that estimated for the CRF06_cpx clade circulating in the same region. These results support the notion that the spatiotemporal dissemination dynamics of major HIV-1 clades circulating in western Africa have probably been shaped by the same ecological factors.

Safety and Comparative Immunogenicity of an HIV-1 DNA Vaccine in Combination with Plasmid Interleukin 12 and Impact of Intramuscular Electroporation for Delivery

DNA vaccines have been very poorly immunogenic in humans but have been an effective priming modality in prime-boost regimens. Methods to increase the immunogenicity of DNA vaccines are needed. HIV Vaccine Trials Network (HVTN) studies 070 and 080 were multicenter, randomized, clinical trials. The human immunodeficiency virus type 1 (HIV-1) PENNVAX®-B DNA vaccine (PV) is a mixture of 3 expression plasmids encoding HIV-1 Clade B Env, Gag, and Pol. The interleukin 12 (IL-12) DNA plasmid expresses human IL-12 proteins p35 and p40. Study subjects were healthy HIV-1-uninfected adults 18-50 years old. Four intramuscular vaccinations were given in HVTN 070, and 3 intramuscular vaccinations were followed by electroporation in HVTN 080. Cellular immune responses were measured by intracellular cytokine staining after stimulation with HIV-1 peptide pools. Vaccination was safe and well tolerated. Administration of PV plus IL-12 with electroporation had a significant dose-sparing effect and provided immunogenicity superior to that observed in the trial without electroporation, despite fewer vaccinations. A total of 71.4% of individuals vaccinated with PV plus IL-12 plasmid with electroporation developed either a CD4(+) or CD8(+) T-cell response after the second vaccination, and 88.9% developed a CD4(+) or CD8(+) T-cell response after the third vaccination. Use of electroporation after PV administration provided superior immunogenicity than delivery without electroporation. This study illustrates the power of combined DNA approaches to generate impressive immune responses in humans.

Generation of Lineage-Related, Mucosally Transmissible Subtype C R5 Simian-Human Immunodeficiency Viruses Capable of AIDS Development, Induction of Neurological Disease, and Coreceptor Switching in Rhesus Macaques

Most human immunodeficiency virus (HIV) transmissions are initiated with CCR5 (R5)-using viruses across mucosal surfaces, with the majority in regions where HIV type 1 (HIV-1) clade C predominates. Mucosally transmissible, highly replication competent, pathogenic R5 simian-human immunodeficiency viruses (SHIVs) encoding biologically relevant clade C envelopes are therefore needed as challenge viruses in vaccine efficacy studies with nonhuman primates. Here we describe the generation of three lineage-related subtype C SHIVs through four successive rapid transfers in rhesus macaques of SHIVC109F.PB4, a molecular clone expressing the soluble-CD4 (sCD4)-sensitive CCR5-tropic clade C envelope of a recently infected subject in Zambia. The viruses differed in their monkey passage histories and neutralization sensitivities but remained R5 tropic. SHIVC109P3 and SHIVC109P3N were recovered from a passage-3 rapid-progressor animal during chronic infection (24 weeks postinfection [wpi]) and at end-stage disease (34 wpi), respectively, and are classified as tier 1B strains, whereas SHIVC109P4 was recovered from a passage-4 normal-progressor macaque at 22 wpi and is a tier 2 virus, more difficult to neutralize. All three viruses were transmitted efficiently via intrarectal inoculation, reaching peak viral loads of 10(7) to 10(9) RNA copies/ml plasma and establishing viremia at various set points. Notably, one of seven (GC98) and two of six (CL31, FI08) SHIVC109P3- and SHIVC109P3N-infected macaques, respectively, progressed to AIDS, with neuropathologies observed in GC98 and FI08, as well as coreceptor switching in the latter. These findings support the use of these new SHIVC109F.PB4-derived viruses to study the immunopathology of HIV-1 clade C infection and to evaluate envelope-based AIDS vaccines in nonhuman primates.

Identification of an HIV-1 Clade A Envelope That Exhibits Broad Antigenicity and Neutralization Sensitivity and Elicits Antibodies Targeting Three Distinct Epitopes

Broadly neutralizing antibodies (bNAbs) PG9 and PG16 were isolated from an International AIDS Vaccine Initiative (IAVI) Protocol G subject infected with human immunodeficiency virus type 1 (HIV-1) clade A. Both antibodies are highly potent and neutralize greater than 70% of viruses tested. We sought to begin immunogen design based on viral sequences from this patient; however, pseudoviruses prepared with 19 envelope sequences from this subject were resistant to neutralization by PG9 and PG16. Therefore, we used a bioinformatics approach to identify closely related viruses that were potentially sensitive to PG9 and PG16. A most-recent common ancestor (MRCA) sequence for the viral envelope (Env) was determined and aligned with 99 subtype A gp160 sequences from the Los Alamos HIV database. Virus BG505.W6M.ENV.C2 (BG505) was found to have the highest degree of homology (73%) to the MRCA sequence. Pseudoviruses prepared with this Env were sensitive to neutralization with a broad panel of bNAbs, including PG9 and PG16. When expressed by 293T cells as soluble gp120, the BG505 monomer bound well to both PG9 and PG16. We further showed that a point mutation (L111A) enabled more efficient production of a stable gp120 monomer that preserves the major neutralization epitopes. Finally, we showed that an adjuvanted formulation of this gp120 protein elicited neutralizing antibodies in rabbits (following a gp120 DNA vaccine prime) and that the antisera competed with bNAbs from 3 classes of nonoverlapping epitopes. Thus, the BG505 Env protein warrants further investigation as an HIV vaccine candidate, as a stand-alone protein, or as a component of a vaccine vector.

Effects of Tat proteins and Tat mutants of different human immunodeficiency virus type 1 clades on glial JC virus early and late gene transcription

Polyomavirus JC (JCV) is the aetiological agent of progressive multifocal leukoencephalopathy (PML), a frequently fatal infection of the brain afflicting nearly 4% of AIDS patients in the USA. Human immunodeficiency virus type 1 (HIV-1) Tat, acting together with cellular proteins at the JCV non-coding control region (NCCR), can stimulate JCV DNA transcription and replication. Tat in the brain is secreted by HIV-1-infected cells and incorporated by oligodendroglia, cells capable of infection by JCV. Thus far the effects of Tat on JCV have been studied primarily with protein encoded by the HIV-1 B clade most common in North America. Here, we determine the abilities of Tat from different HIV-1 clades to alter JCV early and late gene transcription and DNA replication initiated at the JCV origin. Tat from all clades tested stimulates both JCV early and late gene promoters, with clade B Tat being significantly most effective. Tat proteins from the HIV-1 clades display parallel patterns of differences in their effects on HIV-1 and JCV transcription, suggesting that Tat effects in both cases are mediated by the same cellular proteins. Clade B Tat is most effective at directing Smad mediators of tumour growth factor beta and cellular partner Purα to the NCCR. Tat proteins from all non-B clades inhibit initiation of JCV DNA replication. The effectiveness of HIV-1 clade B Tat at promoting JCV transcriptional and replicative processes highlights a need for further investigation to determine which molecular aspects of Tat from distinct HIV-1 substrains can contribute to the course of PML development in neuroAIDS.

Profiles of neutralizing antibody response in chronically human immunodeficiency virus type 1 clade B′-infected former plasma donors from China naïve to antiretroviral therapy

Broadly neutralizing antibodies (NAbs) such as those generated in chronic human immunodeficiency virus type 1 (HIV-1) infection are considered a key component for an effective HIV-1 vaccine. Here, we measured NAb responses using a panel of 25 Env-pseudotyped viruses, including clade B, C, A, CRF07_BC and CRF01_AE strains, against plasma samples from 103 subjects in a former plasma donor cohort in central China, who were infected with HIV-1 clade B' for at least 10 years and naïve to antiretroviral therapy at the time of sampling. We found that 64 % of samples (n = 66) neutralized at least half of the viruses tested and 2 % (n = 2) neutralized all of the viruses, while 5 % (n = 5) neutralized none of the viruses tested. Strikingly, 29 % of plasma samples (n = 30) neutralized >80 % of the viral strains tested, indicating the presence of broadly reactive NAbs in these patients. When the magnitude (geometric mean ID(50) titres, GMTs) or breadth of neutralization was assessed for correlation with CD4 count or plasma viral load, the only significant positive correlations were observed between viral load and neutralization magnitude (r = 0.2189, P = 0.0263) and between viral load and neutralization breadth (r = 0.1970, P = 0.0461). A moderate difference between progressors and long-term non-progressors was observed in both the breadth (P = 0.0316) and the potency (P = 0.0300). A significant difference was found in the GMTs between intra-clade and inter-clade strains (P<0.001). Heat-map analysis based on k-means clustering of plasma determined a statistically stable cluster of plasma with cross-reactive and potent neutralizing reactivity. These samples could provide physical biomaterials for further virological and serological studies from which useful insights into rational HIV-1 vaccine development and therapeutic design might be derived.

Preferential CTL targeting of Gag is associated with relative viral control in long-term surviving HIV-1 infected former plasma donors from China

It is generally believed that CD8(+) cytotoxic T lymphocytes (CTLs) play a critical role in limiting the replication of human immunodeficiency virus type 1 (HIV-1) and in determining the outcome of the infection, and this effect may partly depend on which HIV product is preferentially targeted. To address the correlation between HIV-1-specific CTL responses and virus replication in a cohort of former plasma donors (FPDs), 143 antiretroviral therapy naive FPDs infected with HIV-1 clade B' strains were assessed for HIV-1-specific CTL responses with an IFN-γ Elispot assay at single peptide level by using overlapping peptides (OLPs) covering the whole consensus clade B proteome. By using a Spearman's rank correlation analysis, we found that the proportion of Gag-specific CTL responses among the total virus-specific CTL activity was inversely correlated with viral loads while being positively correlated to CD4 counts, as opposed to Pol- and Env-specific responses that were associated with increased viral loads and decreased CD4 counts. In addition, Vpr-specifc CTL responses showed a similar protective effect with Gag responses, but with a much lower frequency of recognition. Significantly, we also observed an association between HLA-A*30/B*13/Cw*06 haplotype and lower viral loads that was probably due to restricted Gag-specific CTL responses. Thus, our data demonstrate the prominent role of Gag-specific CTL responses in disease control. The advantage of HLA-A*30/B*13/Cw*06 haplotype in viral control may be associated with the contribution of Gag-specific CTL responses in the studied individuals.

The HIV-1 epidemic: low- to middle-income countries.

Low- to middle-income countries bear the overwhelming burden of the human immunodeficiency virus type 1 (HIV-1) epidemic in terms of the numbers of their citizens living with HIV/AIDS (acquired immunodeficiency syndrome), the high degrees of viral diversity often involving multiple HIV-1 clades circulating within their populations, and the social and economic factors that compromise current control measures. Distinct epidemics have emerged in different geographical areas. These epidemics differ in their severity, the population groups they affect, their associated risk behaviors, and the viral strains that drive them. In addition to inflicting great human cost, the high burden of HIV infection has a major impact on the social and economic development of many low- to middle-income countries. Furthermore, the high degrees of viral diversity associated with multiclade HIV epidemics impacts viral diagnosis and pathogenicity and treatment and poses daunting challenges for effective vaccine development.

HIV-1: From escapism to conservatism

HIV-1: From escapism to conservatism

Molecularly cloned SHIV-CN97001: a replication-competent, R5 simian/human immunodeficiency virus containing env of a primary Chinese HIV-1 clade C isolate

The increasing prevalence of human immunodeficiency virus type 1 (HIV-1) subtype C infection worldwide calls for efforts to develop a relevant animal model for evaluating AIDS candidate vaccines. In China, the prevalent HIV strains comprise a circulating recombinant form, BC (CRF07_BC), in which the envelope belongs to subtype C. To evaluate potential AIDS vaccines targeting Chinese viral strains in non-human primate models, we constructed a simian/human immunodeficiency virus (SHIV) carrying most of the envelope sequence of a primary HIV-1 clade C strain isolated from an HIV-positive intravenous drug user from YunNan province in China. Furthermore, to determine whether in vivo adaptation would enhance the infectivity of SHIV-CN97001, the parental infectious strain was serially passaged through eight Chinese rhesus macaques. Infection of six Chinese rhesus macaques with SHIV-CN97001 resulted in a low level of viremia and no significant alteration in CD4+ T-lymphocyte counts. However, the hallmarks of SHIV infectivity developed gradually, as shown by the increasingly elevated peak viremia with each passage. These findings establish that the R5-tropic SHIV-CN97001/Chinese rhesus macaque model should be very useful for the evaluation of HIV-1 subtype C vaccines in China.

An Adjuvanted Polyprotein HIV-1 Vaccine Induces Polyfunctional Cross-Reactive CD4+ T Cell Responses in Seronegative Volunteers

This phase I/II partially blinded, randomized, dose-ranging study assessed the safety and immunogenicity of a novel human immunodeficiency virus type 1 (HIV-1) vaccine candidate consisting of a recombinant fusion protein (F4) containing 4 HIV-1 clade B antigens (Gag p24, Pol reverse transcriptase, Nef, and Gag p17) adjuvanted with AS01 in HIV-seronegative volunteers. Methods. Two doses of the recombinant F4 protein (10, 30, or 90 μg/dose), adjuvanted with AS01 or reconstituted with water for injection, were administered 1 month apart to 180 healthy volunteers aged 18-40 years. F4-specific CD4(+) T cell responses were measured using intracellular cytokine staining after in vitro stimulation by overlapping peptide pools covering the 4 individual antigens. Results. Reactogenicity was higher during the 7-day period after each vaccine dose in the adjuvanted than in the nonadjuvanted groups. In the adjuvanted groups, the overall immune response rate was high after the second vaccine dose, with highest responder rates seen in the 10-μg F4/AS01 group (100% to 3 HIV-1 antigens and 80% to all 4 HIV-1 antigens). High and long-lasting CD4(+) T cell frequencies were observed (up to a median value of 1.2% F4-specific CD4(+) T cells at day 44), with strongest responses directed against reverse transcriptase. Antigen-specific CD4(+) T cells exhibited a polyfunctional phenotype, expressing at least CD40 ligand and interleukin 2, often in combination with tumor necrosis factor α and/or interferon γ. Vaccine-induced CD4(+) T cell responses were broadly cross-reactive to all 4 antigens derived from HIV-1 clades A and C. Conclusions. These results support further clinical investigation of this HIV-1 vaccine candidate both in a prophylactic setting (alone, in conjunction with an envelope-based antigen or in combination with other vaccine approaches in a heterologous prime-boost regimen) and as a potentially disease-modifying therapeutic vaccine in HIV-1-infected subjects. NCT00434512.

Impairment of CD1d-Restricted Natural Killer T Cells in Chronic HIV Type 1 Clade C Infection

Recent studies suggest that natural killer T (NKT) cells play a role in early antiviral pathogenesis and are rapidly depleted in chronic human immunodeficiency virus type 1 (HIV-1) clade B infection. We aimed to characterize the phenotypic and functional characteristics of NKT cells in HIV-1 clade C-infected Africans at different stages of HIV-1 disease. NKT cell frequencies, subsets, and ex vivo effector functions were assessed using multiparametric flow cytometry in a cross-sectional analysis of cryopreserved peripheral blood mononuclear cells from a cohort of 53 HIV-1 clade C chronically infected South African adults with CD4 T cell counts ranging from 94 to 839 cells/μl. We observed a significant decline of NKT cell numbers in advanced HIV-1 disease as well as activation and functional impairment of NKT cells in individuals with low CD4 T cell counts. The loss of NKT cells was largely driven by a reduction in the CD4(+) and CD4(-)CD8(-) NKT cell subsets in advanced disease. These findings demonstrate significant impairment of the NKT cell compartment in progressive HIV-1 clade C disease that might play an important role in the modulation of immune function in HIV-1 infection.

Association of variations of NAb 2F5 and 4E10 epitopes and disease progression in Chinese antiretroviral treatment-naïve patients infected with HIV-1 clade B'.

Studies on human immunodeficiency virus type 1 (HIV-1) vaccines have recently focused on targeting the conserved neutralizing epitopes 2F5 and 4E10, and hence it is important to understand the extent of mutations in these two viral epitopes. Here, we investigated the amino acid mutations in epitopes of 2F5 (ELDKWA, HIV-1 HXB2 env 662 - 667 aa) and 4E10 (NWFDIT, HIV-1 HXB2 env 671 - 676 aa) in the membrane proximal-external region of gp41 from clade B' HIV-1-infected individuals living in Henan province, China. We also examined the frequency of a mutation and its relation to disease progression. A cohort of 54 treatment-naïve HIV-1-infected individuals was recruited in this study, and 16 individuals were selected for a short-term longitudinal study on sequence evolution. The HIV-1 env gp41 gene was amplified, cloned, and sequenced, and predicted amino acid sequences were aligned for analysis. The mutations E662A and K665E on the 2F5 epitope and N671S and T676S on the 4E10 epitope were seen. Simultaneous RNA sequencing showed some discrepancies with proviral DNA sequences. In our longitudinal study, mutation levels of these two neutralizing epitopes were low but diverse and persistent. The frequencies of mutations within the 4E10 peptide NWFDIT in slow progressors were noticeably lower than those in AIDS patients (P < 0.05). Antigenic variation of the neutralizing epitopes 2F5 and 4E10 is limited in subtype B' infection, and that 4E10 peptide mutation is correlated with disease progression. Monitoring epitope mutations will offer useful data for development of the candidate 2F5-like and 4E10-like antibodies to prevent and treat AIDS.

Human immunodeficiency virus type 1 clade B and C Tat differentially induce indoleamine 2,3-dioxygenase and serotonin in immature dendritic cells: Implications for neuroAIDS

Human immunodeficiency virus type 1 (HIV-1) is commonly associated with immune dysfunctions and the suppression of antigen-presenting cells. This results in immune alterations, which could lead to impaired neuronal functions, such as neuroAIDS. The neurotoxic factor kynurenine (KYN), the rate-limiting enzyme indoleamine 2,3-dioxygenase (IDO), serotonin (5-HT), and serotonin transporter (5-HTT) may play a role in tryptophan deficiency and serotogenic dysfunction in neuroAIDS. HIV-1 transactivator regulatory protein (Tat) is known to play a major role in immune dysfunction. Previous studies suggest that HIV-1 B and C clades differentially manifest neuronal dysfunctions in the infected host. In the present study we examine the effect of HIV-1 B and C clade-derived Tat on IDO and 5-HTT gene and protein expressions by dendritic cells as studied by quantitative polymerase chain reaction (qPCR) and Western blot. In addition, the intracellular IDO expression, IDO enzyme activity, and the levels of 5-HT and KYN were also measured. Results indicate that HIV-1 clade B Tat up-regulates IDO and down-regulates 5-HTT gene and protein expressions. Further, HIV-1 clade B Tat caused a reduction of 5-HT with simultaneous increase in KYN levels as compared to HIV-1 clade C Tat. These studies suggest that HIV-1 clade B and C Tat proteins may play a differential role in the neuropathogenesis of HIV-associated dementia (HAD) or HIV-associated neurocognitive disorder (HAND).

Microvirin, a Novel α(1,2)-Mannose-specific Lectin Isolated from Microcystis aeruginosa, Has Anti-HIV-1 Activity Comparable with That of Cyanovirin-N but a Much Higher Safety Profile

Microvirin (MVN), a recently isolated lectin from the cyanobacterium Microcystis aeruginosa PCC7806, shares 33% identity with the potent anti-human immunodeficiency virus (HIV) protein cyanovirin-N (CV-N) isolated from Nostoc ellipsosporum, and both lectins bind to similar carbohydrate structures. MVN is able to inhibit infection by a wide variety of HIV-1 laboratory-adapted strains and clinical isolates of different tropisms and subtypes in peripheral blood mononuclear cells. MVN also inhibits syncytium formation between persistently HIV-1-infected T cells and uninfected CD4(+) T cells and inhibits DC-SIGN-mediated HIV-1 binding and transmission to CD4(+) T cells. Long term passaging of HIV-1 exposed to dose-escalating concentrations of MVN resulted in the selection of a mutant virus with four deleted high mannose-type glycans in the envelope gp120. The MVN-resistant virus was still highly sensitive to various other carbohydrate binding lectins (e.g. CV-N, HHA, GNA, and UDA) but not anymore to the carbohydrate-specific 2G12 monoclonal antibody. Importantly, MVN is more than 50-fold less cytotoxic than CV-N. Also in sharp contrast to CV-N, MVN did not increase the level of the activation markers CD25, CD69, and HLA-DR in CD4(+) T lymphocytes, and subsequently, MVN did not enhance viral replication in pretreated peripheral blood mononuclear cells. Therefore, MVN may qualify as a useful lectin for potential microbicidal use based on its broad and potent antiviral activity and virtual lack of any stimulatory properties and cellular toxicity.

Alterations in Natural Killer Cell Receptor Profiles During HIV Type 1 Disease Progression Among Chronically Infected South African Adults

Recent studies suggest that innate immune responses by natural killer (NK) cells play a significant role in restricting human immunodeficiency virus type-1 (HIV-1) pathogenesis. Our aim was to characterize changes in NK cells associated with HIV-1 clade C disease progression. Here we used multiparametric flow cytometry (LSRII) to quantify phenotype and function of NK cells in a cross-sectional analysis of cryopreserved blood samples from a cohort of 41 chronically HIV-1-infected, treatment-naive adult South Africans. These individuals ranged in disease severity from early (CD4 count >500) to advanced HIV-1 disease (CD4 count <50). We found that the frequency of NK cells expressing KIR2DL1, an inhibitory receptor, and/or KIR2DS1, an activating receptor, tended to decrease with increasing HIV-1 viral load. We also discovered a significant increase (p < 0.05) in overall NK cell degranulation with disease progression. We found that acutely activated NK cells (CD69(pos)) were deficient in NKp46 expression ex vivo. In conclusion, we observed that with viremia and advanced HIV-1 disease, activated NK cells lack NKp46 expression, and KIR2DS1(pos) and/ or KIR2DL1(pos) NK cells are reduced in frequency. These findings suggest that modulation of receptor expression on NK cells may play a role in HIV-1 pathogenesis, and provide new insights on immunological changes in advanced HIV-1 disease.