Macrophage inflammatory protein 1alpha inhibits postentry steps of human immunodeficiency virus type 1 infection via suppression of intracellular cyclic AMP

Reduced CCR5 Expression and Immune Quiescence in Black South African HIV-1 Controllers

Unique Individuals who exhibit either suppressive HIV-1 control, or the ability to maintain low viral load set-points and preserve their CD4+ T cell counts for extended time periods in the absence of antiretroviral therapy, are broadly termed HIV-1 controllers. We assessed the extent to which black South African controllers (n=9), differ from uninfected healthy controls (HCs, n=22) in terms of lymphocyte and monocyte CCR5 expression (density and frequency of CCR5-expressing cells), immune activation as well as peripheral blood mononuclear cell (PBMC) mitogen-induced chemokine/cytokine production. In addition, relative CD4+ T cell CCR5 mRNA expression was assessed in a larger group of controllers (n=20) compared to HCs (n=10) and HIV-1 progressors (n=12). Despite controllers having significantly higher frequencies of activated CD4+ and CD8+ T cells (HLA-DR+) compared to HCs, CCR5 density was significantly lower in these T cell populations (P=0.039 and P=0.064, respectively). This lower CCR5 density was largely attributable to controllers with higher VLs (>400 RNA copies/ml). Significantly lower CD4+ T cell CCR5 density in controllers was maintained (P=0.036) when HCs (n=12) and controllers (n=9) were matched for age. CD4+ T cell CCR5 mRNA expression was significantly less in controllers compared to HCs (P=0.007) and progressors (P=0.002), whereas HCs and progressors were similar (P=0.223). The levels of soluble CD14 in plasma did not differ between controllers and HCs, suggesting no demonstrable monocyte activation. While controllers had lower monocyte CCR5 density compared to the HCs (P=0.02), significance was lost when groups were age-matched (P=0.804). However, when groups were matched for both CCR5 promoter haplotype and age (n=6 for both) reduced CCR5 density on monocytes in controllers relative to HCs was highly significant (P=0.009). Phytohemagglutinin-stimulated PBMCs from the controllers produced significantly less CCL3 (P=0.029), CCL4 (P=0.008) and IL-10 (P=0.028) compared to the HCs, which was largely attributable to the controllers with lower VLs (<400 RNA copies/ml). Our findings support a hypothesis of an inherent (genetic) predisposition to lower CCR5 expression in individuals who naturally control HIV-1, as has been suggested for Caucasian controllers, and thus, likely involves a mechanism shared between ethnically divergent population groups.

Macrophage Inflammatory Protein-1 Beta and Interferon Gamma Responses in Ugandans with HIV-1 Acute/Early Infections

Control of HIV replication through CD4(+) and CD8(+) T cells might be possible, but the functional and phenotypic characteristics of such cells are not defined. Among cytokines produced by T cells, CCR5 ligands, including macrophage inflammatory protein-1 beta (MIP-1β), compete for the CCR5 coreceptor with HIV, promoting CCR5 internalization and decreasing its availability for virus binding. Interferon (IFN)-γ also has some antiviral activity and has been used as a read-out for T cell immunogenicity. We used cultured ELISpot assays to compare the relative contribution of MIP-1β and IFN-γ to HIV-specific responses. The magnitude of responses was 1.36 times higher for MIP-1β compared to IFN-γ. The breadth of the MIP-1β response (45.41%) was significantly higher than IFN-γ (36.88%), with considerable overlap between the peptide pools that stimulated both MIP-1β and IFN-γ production. Subtype A and D cross-reactive responses were observed both at stimulation and test level, but MIP-1β and IFN-γ responses displayed different effect patterns. We conclude that the MIP-1β ELISpot would be a useful complement to the evaluation of the immunogenicity of HIV vaccines and the activity of adjuvants.

Information theoretic approach to complex biological network reconstruction: application to cytokine release in RAW 264.7 macrophages

BACKGROUND

High-throughput methods for biological measurements generate vast amounts of quantitative data, which necessitate the development of advanced approaches to data analysis to help understand the underlying mechanisms and networks. Reconstruction of biological networks from measured data of different components is a significant challenge in systems biology.

RESULTS

We use an information theoretic approach to reconstruct phosphoprotein-cytokine networks in RAW 264.7 macrophage cells. Cytokines are secreted upon activation of a wide range of regulatory signals transduced by the phosphoprotein network. Identifying these components can help identify regulatory modules responsible for the inflammatory phenotype. The information theoretic approach is based on estimation of mutual information of interactions by using kernel density estimators. Mutual information provides a measure of statistical dependencies between interacting components. Using the topology of the network derived, we develop a data-driven parsimonious input-output model of the phosphoprotein-cytokine network.

CONCLUSIONS

We demonstrate the applicability of our information theoretic approach to reconstruction of biological networks. For the phosphoprotein-cytokine network, this approach not only captures most of the known signaling components involved in cytokine release but also predicts new signaling components involved in the release of cytokines. The results of this study are important for gaining a clear understanding of macrophage activation during the inflammation process.

Induction of Potent and Long-Lived Antibody and Cellular Immune Responses in the Genitorectal Mucosa Could be the Critical Determinant of HIV Vaccine Efficacy

The field of HIV prevention has indeed progressed in leaps and bounds, but with major limitations of the current prevention and treatment options, the world remains desperate for an HIV vaccine. Sadly, this continues to be elusive, because more than 30 years since its discovery there is no licensed HIV vaccine. Research aiming to define immunological biomarkers to accurately predict vaccine efficacy have focused mainly on systemic immune responses, and as such, studies defining correlates of protection in the genitorectal mucosa, the primary target site for HIV entry and seeding are sparse. Clearly, difficulties in sampling and analysis of mucosal specimens, as well as their limited size have been a major deterrent in characterizing the type (mucosal antibodies, cytokines, chemokines, or CTL), threshold (magnitude, depth, and breadth) and viral inhibitory capacity of HIV-1-specific immune responses in the genitorectal mucosa, where they are needed to immediately block HIV acquisition and arrest subsequent virus dissemination. Nevertheless, a few studies document the existence of HIV-specific immune responses in the genitorectal mucosa of HIV-infected aviremic and viremic controllers, as well as in highly exposed persistently seronegative (HEPS) individuals with natural resistance to HIV-1. Some of these responses strongly correlate with protection from HIV acquisition and/or disease progression, thus providing significant clues of the ideal components of an efficacious HIV vaccine. In this study, we provide an overview of the key features of protective immune responses found in HEPS, elite and viremic controllers, and discuss how these can be achieved through mucosal immunization. Inevitably, HIV vaccine development research will have to consider strategies that elicit potent antibody and cellular immune responses within the genitorectal mucosa or induction of systemic immune cells with an inherent potential to home and persist at mucosal sites of HIV entry.

HIV-1-associated PKA acts as a cofactor for genome reverse transcription

Background

Host cell proteins, including cellular kinases, are embarked into intact HIV-1 particles. We have previously shown that the Cα catalytic subunit of cAMP-dependent protein kinase is packaged within HIV-1 virions as an enzymatically active form able to phosphorylate a synthetic substrate in vitro (Cartier et al. J. Biol. Chem. 278:35211 (2003)). The present study was conceived to investigate the contribution of HIV-1-associated PKA to the retroviral life cycle.

Results

NL4.3 viruses were produced from cells cultured in the presence of PKA inhibitors H89 (H89-NL4.3) or Myr-PKI (PKI-NL4.3) and analyzed for viral replication. Despite being mature and normally assembled, and containing expected levels of genomic RNA and RT enzymatic activity, such viruses showed poor infectivity. Indeed, infection generated reduced amounts of strong-strop minus strand DNA, while incoming RNA levels in target cells were unaffected. Decreased cDNA synthesis was also evidenced in intact H89-NL4.3 and PKI-NL4.3 cell free particles using endogenous reverse transcription (ERT) experiments. Moreover, similar defects were reproduced when wild type NL4.3 particles preincubated with PKA inhibitors were subjected to ERT reactions.

Conclusions

Altogether, our results indicate that HIV-1-associated PKA is required for early reverse transcription of the retroviral genome both in cell free intact viruses and in target cells. Accordingly, virus-associated PKA behaves as a cofactor of an intraviral process required for optimal reverse transcription and for early post-entry events.

HIV-1 infected lymphoid organs upregulate expression and release of the cleaved form of uPAR that modulates chemotaxis and virus expression

Cell-associated receptor for urokinase plasminogen activator (uPAR) is released as both full-length soluble uPAR (suPAR) and cleaved (c-suPAR) form that maintain ability to bind to integrins and other receptors, thus triggering and modulating cell signaling responses. Concerning HIV-1 infection, plasma levels of suPAR have been correlated with the severity of disease, levels of immune activation and ineffective immune recovery also in individuals receiving combination anti-retroviral therapy (cART). However, it is unknown whether and which suPAR forms might contribute to HIV-1 induced pathogenesis and to the related state of immune activation. In this regard, lymphoid organs represent an import site of chronic immune activation and virus persistence even in individuals receiving cART. Lymphoid organs of HIV-1(+) individuals showed an enhanced number of follicular dendritic cells, macrophages and endothelial cells expressing the cell-associated uPAR in comparison to those of uninfected individuals. In order to investigate the potential role of suPAR forms in HIV-1 infection of secondary lymphoid organs, tonsil histocultures were established from HIV-1 seronegative individuals and infected ex vivo with CCR5- and CXCR4-dependent HIV-1 strains. The levels of suPAR and c-suPAR were significantly increased in HIV-infected tonsil histocultures supernatants in comparison to autologous uninfected histocultures. Supernatants from infected and uninfected cultures before and after immunodepletion of suPAR forms were incubated with the chronically infected promonocytic U1 cell line characterized by a state of proviral latency in unstimulated conditions. In the contest of HIV-conditioned supernatants we established that c-suPAR, but not suPAR, inhibited chemotaxis and induced virus expression in U1 cells. In conclusion, lymphoid organs are an important site of production and release of both suPAR and c-suPAR, this latter form being endowed with the capacity of inhibiting chemotaxis and inducing HIV-1 expression.

HIV-1 Nef impairs heterotrimeric G-protein signaling by targeting Gα(i2) for degradation through ubiquitination

The HIV Nef protein is an important pathogenic factor that modulates cell surface receptor trafficking and impairs cell motility, presumably by interfering at multiple steps with chemotactic receptor signaling. Here, we report that a dominant effect of Nef is to trigger AIP4 E3 ligase-mediated Gα(i2) ubiquitination, which leads to Gα(i2) endolysosomal sequestration and destruction. The loss of the Gα(i2) subunit was demonstrable in many cell types in the context of gene transfection, HIV infection, or Nef protein transduction. Nef directly interacts with Gα(i2) and ternary complexes containing AIP4, Nef, and Gα(i2) form. A substantial reversal of Gα(i2) loss and a partial recovery of impaired chemotaxis occurred following siRNA knockdown of AIP4 or NEDD4 or by inhibiting dynamin. The N-terminal myristoyl group, (62)EEEE(65) motif, and (72)PXXP(75) motif of Nef are critical for this effect to occur. Nef expression does not affect a Gq(i5) chimera where the five C-terminal residues of Gq are replaced with those of Gα(i2). Lysine at position 296 of Gα(i2) was identified as the critical determinant of Nef-induced degradation. By specifically degrading Gα(i2), Nef directly subverts leukocyte migration and homing. Impaired trafficking and homing of HIV Nef-expressing lymphocytes probably contributes to early immune dysfunction following HIV infection.

Mice with disrupted type I protein kinase A anchoring in T cells resist retrovirus-induced immunodeficiency

Type I protein kinase A (PKA) is targeted to the TCR-proximal signaling machinery by the A-kinase anchoring protein ezrin and negatively regulates T cell immune function through activation of the C-terminal Src kinase. RI anchoring disruptor (RIAD) is a high-affinity competitor peptide that specifically displaces type I PKA from A-kinase anchoring proteins. In this study, we disrupted type I PKA anchoring in peripheral T cells by expressing a soluble ezrin fragment with RIAD inserted in place of the endogenous A-kinase binding domain under the lck distal promoter in mice. Peripheral T cells from mice expressing the RIAD fusion protein (RIAD-transgenic mice) displayed augmented basal and TCR-activated signaling, enhanced T cell responsiveness assessed as IL-2 secretion, and reduced sensitivity to PGE(2)- and cAMP-mediated inhibition of T cell function. Hyperactivation of the cAMP-type I PKA pathway is involved in the T cell dysfunction of HIV infection, as well as murine AIDS, a disease model induced by infection of C57BL/6 mice with LP-BM5, a mixture of attenuated murine leukemia viruses. LP-BM5-infected RIAD-transgenic mice resist progression of murine AIDS and have improved viral control. This underscores the cAMP-type I PKA pathway in T cells as a putative target for therapeutic intervention in immunodeficiency diseases.

C7 Anti-infective activity of immunomodulators

Infectious diseases continue to impact human morbidity and mortality. Every individual is vulnerable to microbial infections regardless of socioeconomic status, gender, age group or ethnic background. There has been an explosion of international air travel with an estimated 2 billion passengers travelling on commercial airlines every year. The rapid expansion of globalization and mass tourism has facilitated the spread of disease-causing pathogens from one continent to another at unprecedented rates.

Secretion of MIP-1β and MIP-1α by CD8(+) T-lymphocytes correlates with HIV-1 inhibition independent of coreceptor usage

CD8(+) T-lymphocytes can utilize noncytolytic mechanisms to suppress HIV-1 replication through the secretion of soluble factors. The secretion of MIP-1β, MIP-1α, IP-10, MIG, IL-1α, and interferon gamma correlated most strongly with soluble noncytolytic suppression (p<0.0001). Since the noncytolytic response is impaired by histone hyperacetylation, we examined the ability of histone hyperacetylation to alter the expression of immune-related genes. MIP-1α and IP-10 were also among the genes that were down-regulated by histone hyperacetylation. We define a multifactorial cytokine profile of CD8(+) T-lymphocytes capable of mediating noncytolytic suppression of CXCR4-tropic HIV-1 replication.

CCL20/MIP3alpha is a novel anti-HIV-1 molecule of the human female reproductive tract

PROBLEM

CCL20/MIP3alpha is a chemokine for immature dendritic cells as well as an antibacterial against gram-positive and gram-negative bacteria. The role of CCL20/MIP3alpha as an antiviral is unknown. In this study, we have examined the production of CCL20/MIP3alpha by epithelial cells from the upper female reproductive tract as well as its activity as an antiviral molecule.

METHOD OF STUDY

Primary uterine and Fallopian tube epithelial cells were treated with Poly(I:C) and CCL20/MIP3alpha mRNA and protein was measured by Realtime RT-PCR and ELISA assays. Anti-HIV activity was determined using an indicator cell line TZM-bl and quantified by using a luminometer.

RESULTS

Primary uterine and Fallopian tube epithelial cells produce CCL20/MIP3alpha constitutively and the production is enhanced following stimulation with viral double-stranded RNA mimic Poly(I:C). Recombinant CCL20/MIP3alpha was able to inhibit both T-cell-tropic X4/IIIB and macrophage-tropic R5/BaL HIV-1 when virus was directly incubated with CCL20/MIP3alpha but not when CCL20/MIP3alpha was added to cells either prior to infection or post-infection. This suggests that the mechanism of inhibition is likely to be a direct interaction between HIV-1 and CCL20/MIP3alpha.

CONCLUSION

This study demonstrates that CCL20/MIP3alpha is an important endogenous anti-HIV-1 microbicide of the female reproductive tract.

Trappin-2/Elafin: a novel innate anti-human immunodeficiency virus-1 molecule of the human female reproductive tract

Trappin-2/Elafin is a serine protease inhibitor that plays a major role as an anti-inflammatory mediator at mucosal surfaces. In addition, Trappin-2/Elafin has antibacterial activity against Gram-positive and Gram-negative bacterial and fungal pathogens. In this study we examined the production of Trappin-2/Elafin by epithelial cells from the human upper and lower female reproductive tract as well as its activity as an anti-human immunodeficiency virus (HIV)-1 molecule. We found that primary uterine, Fallopian tube, cervical and ectocervical epithelial cells produce Trappin-2/Elafin constitutively and that production of Trappin-2/Elafin is enhanced following stimulation with Poly(I:C), especially by the uterine cells. Given the presence of Trappin-2/Elafin in the reproductive tract, we tested the ability of recombinant Trappin-2/Elafin to inhibit HIV-1, an important sexually transmitted pathogen. We found that recombinant Trappin-2/Elafin was able to inhibit both T-cell-tropic X4/IIIB and macrophage-tropic R5/BaL HIV-1 in a dose-dependent manner. The inhibitory activity was observed when virus was incubated with Trappin-2/Elafin but not when Trappin-2/Elafin was added to cells either before infection or after infection. This suggests that the mechanism of inhibition is likely to be a direct interaction between HIV-1 and Trappin-2/Elafin. Additionally, we measured the levels of secreted Trappin-2/Elafin in cervico-vaginal lavages (CVL) from both HIV-positive and HIV-negative women and found that average levels of secreted Trappin-2/Elafin were higher in the CVL from HIV-negative women, although the values did not reach statistical significance. We also found that women at the secretory phase of the menstrual cycle produced more Trappin-2/Elafin in CVL relative to women at the proliferative phase of the menstrual cycle. Our data suggest that Trappin-2/Elafin might be an important endogenous microbicide of the female reproductive tract that is protective against HIV-1.

RANTES modulates the release of glutamate in human neocortex

The effects of the recombinant chemokine human RANTES (hRANTES) on the release of glutamate from human neocortex glutamatergic nerve endings were investigated. hRANTES facilitated the spontaneous release of d [(3)H]D-aspartate ([(3)H]DASP-) by binding Pertussis toxin-sensitive G-protein-coupled receptors (GPCRs), whose activation caused Ca(2+) mobilization from inositol trisphosphate-sensitive stores and cytosolic tyrosine kinase-mediated phosphorylations. Facilitation of release switched to inhibition when the effects of hRANTES on the 12 mM K(+)-evoked [(3)H]D-ASP exocytosis were studied. Inhibition of exocytosis relied on activation of Pertussis toxin-sensitive GPCRs negatively coupled to adenylyl cyclase. Both hRANTES effects were prevented by met-RANTES, an antagonist at the chemokine receptors (CCRs) of the CCR1, CCR3, and CCR5 subtypes. Interestingly, human neocortex glutamatergic nerve endings seem to possess all three receptor subtypes. Blockade of CCR1 and CCR5 by antibodies against the extracellular domain of CCRs prevented both the hRANTES effect on [(3)H]D-ASP release, whereas blockade of CCR3 prevented inhibition, but not facilitation, of release. The effects of RANTES on the spontaneous and the evoked release of [(3)H]D-ASP were also observed in experiments with mouse cortical synaptosomes, which may therefore represent an appropriate animal model to study RANTES-induced effects on neurotransmission. It is concluded that glutamate transmission can be modulated in opposite directions by RANTES acting at distinct CCR receptor subtypes coupled to different transduction pathways, consistent with the multiple and sometimes contrasting effects of the chemokine.

CCL3L1-CCR5 genotype improves the assessment of AIDS Risk in HIV-1-infected individuals

BACKGROUND

Whether vexing clinical decision-making dilemmas can be partly addressed by recent advances in genomics is unclear. For example, when to initiate highly active antiretroviral therapy (HAART) during HIV-1 infection remains a clinical dilemma. This decision relies heavily on assessing AIDS risk based on the CD4+ T cell count and plasma viral load. However, the trajectories of these two laboratory markers are influenced, in part, by polymorphisms in CCR5, the major HIV coreceptor, and the gene copy number of CCL3L1, a potent CCR5 ligand and HIV-suppressive chemokine. Therefore, we determined whether accounting for both genetic and laboratory markers provided an improved means of assessing AIDS risk.

METHODS AND FINDINGS

In a prospective, single-site, ethnically-mixed cohort of 1,132 HIV-positive subjects, we determined the AIDS risk conveyed by the laboratory and genetic markers separately and in combination. Subjects were assigned to a low, moderate or high genetic risk group (GRG) based on variations in CCL3L1 and CCR5. The predictive value of the CCL3L1-CCR5 GRGs, as estimated by likelihood ratios, was equivalent to that of the laboratory markers. GRG status also predicted AIDS development when the laboratory markers conveyed a contrary risk. Additionally, in two separate and large groups of HIV+ subjects from a natural history cohort, the results from additive risk-scoring systems and classification and regression tree (CART) analysis revealed that the laboratory and CCL3L1-CCR5 genetic markers together provided more prognostic information than either marker alone. Furthermore, GRGs independently predicted the time interval from seroconversion to CD4+ cell count thresholds used to guide HAART initiation.

CONCLUSIONS

The combination of the laboratory and genetic markers captures a broader spectrum of AIDS risk than either marker alone. By tracking a unique aspect of AIDS risk distinct from that captured by the laboratory parameters, CCL3L1-CCR5 genotypes may have utility in HIV clinical management. These findings illustrate how genomic information might be applied to achieve practical benefits of personalized medicine.

Induction of the Galpha(q) signaling cascade by the human immunodeficiency virus envelope is required for virus entry

Binding of human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein (Env) with the primary receptor CD4 and one of two coreceptors, CXCR4 or CCR5, activates a signaling cascade resulting in Rac-1 GTPase activation and stimulation of actin cytoskeletal reorganizations critical for HIV-1-mediated membrane fusion. The mechanism by which HIV-1 Env induces Rac-1 activation and subsequent actin cytoskeleton rearrangement is unknown. In this study, we show that Env-mediated Rac-1 activation is dependent on the activation of Galpha(q) and its downstream targets. Fusion and Rac-1 activation are mediated by Galpha(q) and phospholipase C (PLC), as shown by attenuation of fusion and Rac-1 activation in cells either expressing small interfering RNA (siRNA) targeting Galpha(q) or treated with the PLC inhibitor U73122. Rac-1 activation and fusion were also blocked by multiple protein kinase C inhibitors, by inhibitors of intracellular Ca2+ release, by Pyk2-targeted siRNA, and by the Ras inhibitor S-trans,trans-farnesylthiosalicylic acid (FTS). Fusion was blocked without altering cell viability or cell surface localization of CD4 and CCR5. Similar results were obtained when cell fusion was induced by Env expressed on viral and cellular membranes and when cell lines or primary cells were the target. Treatment with inhibitors and siRNA specific for Galpha(i) or Galpha(s) signaling mediators had no effect on Env-mediated Rac-1 activation or cell fusion, indicating that the Galpha(q) pathway alone is responsible. These results could provide a new focus for therapeutic intervention with drugs targeting host signaling mediators rather than viral molecules, a strategy which is less likely to result in resistance.

AKAP149 binds to HIV-1 reverse transcriptase and is involved in the reverse transcription

Like all retroviruses, human immunodeficiency virus type 1 (HIV-1) undergoes reverse transcription during its replication cycle. The cellular cofactors potentially involved in this process still remain to be identified. We show here that A-kinase anchoring protein 149 (AKAP149) interacts with HIV-1 reverse transcriptase (RT) in both the yeast two-hybrid system and human cells. The AKAP149 binding site has been mapped to the RNase H domain of HIV-1 RT. AKAP149 silencing by RNA interference in HIV-1-infected cells inhibited viral replication at the reverse transcription step. We selected single-point mutants of RT defective for AKAP149 binding and demonstrated that mutant G462R, despite retaining significant intrinsic RT activity in vitro, failed to carry out HIV-1 reverse transcription correctly in infected cells. This suggests that the interaction between RT and AKAP149 in infected cells may play an important role in HIV-1 reverse transcription.

Protein kinase A-dependent step(s) in hepatitis C virus entry and infectivity

Viruses exploit signaling pathways to their advantage during multiple stages of their life cycle. We demonstrate a role for protein kinase A (PKA) in the hepatitis C virus (HCV) life cycle. The inhibition of PKA with H89, cyclic AMP (cAMP) antagonists, or the protein kinase inhibitor peptide reduced HCV entry into Huh-7.5 hepatoma cells. Bioluminescence resonance energy transfer methodology allowed us to investigate the PKA isoform specificity of the cAMP antagonists in Huh-7.5 cells, suggesting a role for PKA type II in HCV internalization. Since viral entry is dependent on the host cell expression of CD81, scavenger receptor BI, and claudin-1 (CLDN1), we studied the role of PKA in regulating viral receptor localization by confocal imaging and fluorescence resonance energy transfer (FRET) analysis. Inhibiting PKA activity in Huh-7.5 cells induced a reorganization of CLDN1 from the plasma membrane to an intracellular vesicular location(s) and disrupted FRET between CLDN1 and CD81, demonstrating the importance of CLDN1 expression at the plasma membrane for viral receptor activity. Inhibiting PKA activity in Huh-7.5 cells reduced the infectivity of extracellular virus without modulating the level of cell-free HCV RNA, suggesting that particle secretion was not affected but that specific infectivity was reduced. Viral particles released from H89-treated cells displayed the same range of buoyant densities as did those from control cells, suggesting that viral protein association with lipoproteins is not regulated by PKA. HCV infection of Huh-7.5 cells increased cAMP levels and phosphorylated PKA substrates, supporting a model where infection activates PKA in a cAMP-dependent manner to promote virus release and transmission.

CCR5-restricted HIV type 2 variants from long-term aviremic individuals are less sensitive to inhibition by beta-chemokines than low pathogenic HIV type 1 variants

Many HIV-2-infected individuals maintain low, often undetectable, viral loads for prolonged periods. Virus and/or host factors that contribute to this high level of virus control are largely unknown. Previously we demonstrated that HIV-2 variants from long-term aviremic individuals have relatively low replication kinetics in vitro in comparison to HIV-1 variants. We hypothesized that the relatively low replication rates of HIV-2 in vitro as well as the high level of virus control in vivo might be explained by HIV-2 replication being more sensitive to inhibitory host factors like beta-chemokines or other CD8+ T cell-derived factors than HIV-1 replication. To test this we determined the effect of exogenously added beta-chemokines and healthy donor CD8+ T cells on the in vitro virus production of HIV-2 and HIV-1 variants from long-term nonprogressors (LTNPs). Contrary to expectations, HIV-2 replication was inhibited less efficiently by RANTES and MIP-1alpha than HIV-1 replication. CD8+ T cells from 8 of 12 healthy donors reduced HIV replication minimally 2-fold. Interestingly, cells from five of these donors inhibited HIV-1 but hardly affected HIV-2 replication, while the reverse was observed for cells from one donor. For HIV-1, but not HIV-2, the magnitude of the antiviral effect of CD8+ T cells correlated with their effect on RANTES levels in culture supernatants. Our findings indicate that RANTES is a more important factor of CD8+ T cell-associated anti-HIV-1 activity than it is of HIV-2 activity and that the benign clinical course of HIV-2 infection is not due to enhanced beta-chemokine sensitivity of HIV-2 variants.

Expression of GB virus C NS5A protein from genotypes 1, 2, 3 and 5 and a 30 aa NS5A fragment inhibit human immunodeficiency virus type 1 replication in a CD4+ T-lymphocyte cell line

GB virus type C (GBV-C) is a common human flavivirus that has been associated with prolonged survival in HIV-positive individuals in several, though not all, epidemiological studies. There are five distinct GBV-C genotypes that are geographically localized, and it has been speculated that GBV-C genotypic differences may explain variable outcomes observed in different clinical studies. Expression of an 85 aa fragment of the GBV-C NS5A phosphoprotein (genotype 2) in a CD4+ T cell line (Jurkat) resulted in inhibition of HIV replication, mediated in part by decreased surface expression of the HIV coreceptor CXCR4 and upregulation of SDF-1. We expressed the NS5A protein from genotypes 1, 2, 3 and 5 in Jurkat cells, and demonstrated that all genotypes inhibited HIV replication. Further deletion mapping demonstrated that expression of a 30 aa fragment resulted in decreased CXCR4 surface expression, upregulation of SDF-1 and inhibition of HIV replication.

CCL3L1 and CCR5 influence cell-mediated immunity and affect HIV-AIDS pathogenesis via viral entry-independent mechanisms

Although host defense against human immunodeficiency virus 1 (HIV-1) relies mainly on cell-mediated immunity (CMI), the determinants of CMI in humans are poorly understood. Here we demonstrate that variations in the genes encoding the chemokine CCL3L1 and HIV coreceptor CCR5 influence CMI in both healthy and HIV-infected individuals. CCL3L1-CCR5 genotypes associated with altered CMI in healthy subjects were similar to those that influence the risk of HIV transmission, viral burden and disease progression. However, CCL3L1-CCR5 genotypes also modify HIV clinical course independently of their effects on viral load and CMI. These results identify CCL3L1 and CCR5 as major determinants of CMI and demonstrate that these host factors influence HIV pathogenesis through their effects on both CMI and other viral entry-independent mechanisms.

Inhibition of HIV replication: A powerful antiviral strategy by IFN-β gene delivery in CD4+ cells

In this study, we demonstrated the efficiency and feasibility of a gene therapy protocol against HIV infection using the antiviral effects of IFN-beta expression. Lentiviral vectors containing the human or the simian IFN-beta sequences under the influence of the murine moderate H2-kb promoter were constructed. To examine the capacity of IFN-beta to inhibit the replication of HIV in human CD4(+) cells, a transduction protocol permitting to efficiently transduce CD4(+) cells or PBMC (85+/-12% of CD4(+)-transduced cells) with a moderate expression of IFN-beta was developed. Results indicate that enforced expression of IFN-beta has no negative effects in terms of apoptosis and proliferation. In human CD4(+) cells, it drastically inhibits (up to 99.9%) replication after challenging with different strains of HIV-1. The expression of exogenous IFN-beta leads to an amplification of the CD4(+) cells (11-fold) and to a drastic decrease of the p24 protein. Micro-array analyses indicated that antiviral effect of IFN-beta could be due to a major regulation of the inflammatory response. These results are encouraging for the development of a clinical study of gene therapy against AIDS using IFN-beta.

Inhibition of human immunodeficiency virus type 1 infection of human CD4+ T cells by microbial HSP70 and the peptide epitope 407-426

Human immunodeficiency virus type 1 (HIV-1) virions contain heat shock proteins (HSP), but these proteins have received limited attention. The objectives of this study were to establish if the microbial 70-kDa HSP exerts an inhibitory effect on the HIV-1 infection of human CD4+ T cells, to identify an inhibitory peptide epitope within the sequence of HSP70, and to evaluate the kinetic features of any inhibitory activity. The results of these studies suggest that microbial HSP70 exerts dose-dependent inhibition on CCR5 (R5) strains of clades B, C, and D of HIV-1 infecting human CD4+ T cells. The site of the HIV-1-inhibitory function was identified within the C-terminal peptide binding domain of HSP70, and the function is expressed by the peptide epitope comprising amino acids 407 to 426. The mechanism of inhibition of HIV-1 infectivity by HSP70 is blocking of the CCR5 coreceptors directly and indirectly by inducing CC chemokines and APOBEC3G. The inhibitory effect of HSP70, its C-terminal fragment, or peptide 407-426 may make HSP70 useful as a microbicidal agent. A potentiating noncognate inhibition of HIV-1 infectivity by combined treatment with HSP70 and monoclonal or polyclonal antibody to CCR5 was demonstrated. This novel strategy may be utilized in therapeutic immunization against HIV-1 infection.

An 85-aa segment of the GB virus type C NS5A phosphoprotein inhibits HIV-1 replication in CD4+ Jurkat T cells

GB virus type C (GBV-C) is an apparently nonpathogenic virus that replicates in T and B lymphocytes and is a common cause of persistent human infection. Among HIV-1-infected individuals, persistent coinfection with GBV-C is associated with prolonged survival, and infection of blood mononuclear cells or CD4+ T cells with GBV-C and HIV in vitro results in significantly reduced HIV-1 replication. To date, the viral protein(s) that lead to HIV inhibition have not been identified. The GBV-C nonstructural phosphoprotein (NS5A) is predicted to have pleotropic effects on cells, including interactions with the IFN-induced dsRNA-activated protein kinase (PKR). We studied GBV-C NS5A to determine whether it is involved in inhibition of HIV replication. GBV-C NS5A protein from an isolate that was cleared by IFN therapy did not inhibit PKR, whereas NS5A from an isolate that was not cleared by IFN-inhibited PKR function in a yeast genetic system. Both of these GBV-C NS5A proteins were expressed in a CD4+ T cell line (Jurkat), and both induced a potent, dose-dependent inhibition of HIV-1 replication, thus the effect was independent of PKR inhibition. NS5A induced the release of the chemokine SDF-1 and decreased surface expression of the HIV coreceptor CXCR4, potentially explaining the HIV inhibition. Deletion mapping of the NS5A protein found that an 85-aa region between amino acids 152 and 237 inhibits HIV-1 replication. Thus, GBV-C NS5A protein alters the cellular milieu necessary for HIV-1 replication and may provide a previously undescribed therapeutic approach for anti-HIV therapy.

The effect of capsid mutations on HIV-1 uncoating

Efficient uncoating requires not only an optimal cellular environment, but also some intrinsic properties of the viral capsid protein itself. Using an in vitro uncoating model, we demonstrated that substitution of each serine residue with alanine at the three major phosphorylation sites of HIV-1 capsid protein, i.e. Ser-109, Ser-149 and Ser-178, could significantly reduce uncoating activity of purified core particles. We also showed that the core stability of mutant viruses was lower than that of the wild-type virus so that the lack of efficient uncoating of each mutant could not be due to an increase in capsid physical stability. However, serine-to-aspartic acid mutation to mimic the negative charge of phosphor-serine could not restore either uncoating activity or infectivity, and treatment of purified core particles with a phosphatase did not alter the uncoating activity. Our data indicated that mutations at phosphoacceptor sites of capsid disturbed the uncoating mechanism, but the defect may not be directly caused by the lack of phosphate on the core particles undergoing uncoating.