The inhibitor of apoptosis proteins antagonist Debio 1143 promotes the PD-1 blockade-mediated HIV load reduction in blood and tissues of humanized mice.

The immune checkpoint programmed cell death protein 1 (PD-1) plays a major role in T cell exhaustion in cancer and chronic HIV infection. The inhibitor of apoptosis protein antagonist Debio 1143 (D1143) enhances tumor cell death and synergizes with anti-PD-1 agents to promote tumor immunity and displayed HIV latency reversal activity in vitro. We asked in this study whether D1143 would stimulate the potency of an anti-human PD-1 monoclonal antibody (mAb) to reduce HIV loads in humanized mice. Anti-PD-1 mAb treatment decreased PD-1+ CD8+ cell population by 32.3% after interruption of four weeks treatment, and D1143 co-treatment further reduced it from 32.3 to 73%. Anti-PD-1 mAb administration reduced HIV load in blood by 94%, and addition of D1143 further enhanced this reduction from 94 to 97%. D1143 also more profoundly promoted with the anti-PD-1-mediated reduction of HIV loads in all tissues analyzed including spleen (71 to 96.4%), lymph nodes (64.3 to 80%), liver (64.2 to 94.4), lung (64.3 to 80.1%) and thymic organoid (78.2 to 98.2%), achieving a >5 log reduction of HIV loads in CD4+ cells isolated from tissues 2 weeks after drug treatment interruption. Ex vivo anti-CD3/CD28 stimulation increased the ability to activate exhausted CD8+ T cells in infected mice having received in vivo anti-PD-1 treatment by 7.9-fold (5 to 39.6%), and an additional increase by 1.7-fold upon D1143 co-treatment (39.6 to 67.3%). These findings demonstrate for the first time that an inhibitor of apoptosis protein antagonist enhances in a statistically manner the effects of an immune check point inhibitor on antiviral immunity and on HIV load reduction in tissues of humanized mice, suggesting that the combination of two distinct classes of immunomodulatory agents constitutes a promising anti-HIV immunotherapeutic approach.

A Pan-Cyclophilin Inhibitor, CRV431, Decreases Fibrosis and Tumor Development in Chronic Liver Disease Models.

Previous studies show that cyclophilins contribute to many pathologic processes, and cyclophilin inhibitors demonstrate therapeutic activities in many experimental models. However, no drug with cyclophilin inhibition as the primary mode of action has advanced completely through clinical development to market. In this study, we present findings on the cyclophilin inhibitor, CRV431, that highlight its potential as a drug candidate for chronic liver diseases. CRV431 was found to potently inhibit all cyclophilin isoforms tested-A, B, D, and G. Inhibitory constant or IC50 values ranged from 1 to 7 nM, which was up to 13 times more potent than the parent compound, cyclosporine A (CsA), from which CRV431 was derived. Other CRV431 advantages over CsA as a nontransplant drug candidate were significantly diminished immunosuppressive activity, less drug transporter inhibition, and reduced cytotoxicity potential. Oral dosing to mice and rats led to good blood exposures and a 5- to 15-fold accumulation of CRV431 in liver compared with blood concentrations across a wide range of CRV431 dosing levels. Most importantly, CRV431 decreased liver fibrosis in a 6-week carbon tetrachloride model and in a mouse model of nonalcoholic steatohepatitis (NASH). Additionally, CRV431 administration during a late, oncogenic stage of the NASH disease model resulted in a 50% reduction in the number and size of liver tumors. These findings are consistent with CRV431 targeting fibrosis and cancer through multiple, cyclophilin-mediated mechanisms and support the development of CRV431 as a safe and effective drug candidate for liver diseases. SIGNIFICANCE STATEMENT: Cyclophilin inhibitors have demonstrated therapeutic activities in many disease models, but no drug candidates have yet advanced completely through development to market. In this study, CRV431 is shown to potently inhibit multiple cyclophilin isoforms, possess several optimized pharmacological properties, and decrease liver fibrosis and tumors in mouse models of chronic liver disease, which highlights its potential to be the first approved drug primarily targeting cyclophilin isomerases.

The inhibitor apoptosis protein antagonist Debio 1143 Is an attractive HIV-1 latency reversal candidate.

Antiretroviral therapy (ART) suppresses HIV replication, but does not cure the infection because replication-competent virus persists within latently infected CD4+ T cells throughout years of therapy. These reservoirs contain integrated HIV-1 genomes and can resupply active virus. Thus, the development of strategies to eliminate the reservoir of latently infected cells is a research priority of global significance. In this study, we tested efficacy of a new inhibitor of apoptosis protein antagonist (IAPa) called Debio 1143 at reversing HIV latency and investigated its mechanisms of action. Debio 1143 activates HIV transcription via NF-kB signaling by degrading the ubiquitin ligase baculoviral IAP repeat-containing 2 (BIRC2), a repressor of the non-canonical NF-kB pathway. Debio 1143-induced BIRC2 degradation results in the accumulation of NF-κB-inducing kinase (NIK) and proteolytic cleavage of p100 into p52, leading to nuclear translocation of p52 and RELB. Debio 1143 greatly enhances the binding of RELB to the HIV-1 LTR. These data indicate that Debio 1143 activates the non-canonical NF-kB signaling pathway by promoting the binding of RELB:p52 complexes to the HIV-1 LTR, resulting in the activation of the LTR-dependent HIV-1 transcription. Importantly, Debio 1143 reverses viral latency in HIV-1 latent T cell lines. Using knockdown (siRNA BIRC2), knockout (CRIPSR NIK) and proteasome machinery neutralization (MG132) approaches, we found that Debio 1143-mediated HIV latency reversal is BIRC2 degradation- and NIK stabilization-dependent. Debio 1143 also reverses HIV-1 latency in resting CD4+ T cells derived from ART-treated patients or HIV-1-infected humanized mice under ART. Interestingly, daily oral administration of Debio 1143 in cancer patients at well-tolerated doses elicited BIRC2 target engagement in PBMCs and induced a moderate increase in cytokines and chemokines mechanistically related to NF-kB signaling. In conclusion, we provide strong evidences that the IAPa Debio 1143, by initially activating the non-canonical NF-kB signaling and subsequently reactivating HIV-1 transcription, represents a new attractive viral latency reversal agent (LRA).

Cyclophilin Inhibitors Remodel the Endoplasmic Reticulum of HCV-Infected Cells in a Unique Pattern Rendering Cells Impervious to a Reinfection.

The mechanisms of action by which cyclophilin inhibitors (CypI) interfere with the HCV life cycle remain poorly understood. We reported that CypI and NS5A inhibitors (NS5Ai), but not other classes of anti-HCV agents, prevent assembly of double membrane vesicles (DMVs), which protect replication complexes. We demonstrated that both NS5A and the isomerase cyclophilin A (CypA) are required for DMV formation. Here, we examined whether CypI mediate an additional antiviral effect that could further explain the high efficacy of CypI. We identified a unique action of CypI. CypI remodel the organization of the endoplasmic reticulum (ER) of HCV-infected cells, but not of uninfected cells. This effect is specific since it was not observed for other classes of anti-HCV agents including NS5Ai, and has no effect on the viability of CypI-treated cells. Since ER serves as platform for the establishment of HCV replication complexes, we asked whether the ER reorganization by CypI would prevent cells from being newly infected. Remarkably, CypI-treated HCV-pre-infected cells remain totally impervious to a reinfection, suggesting that the CypI-mediated ER reorganization prevents a reinfection. This block is not due to residual CypI since CypI-resistant HCV variants also fail to infect these cells. The ER reorganization by CypI is rapid and reversible. This study provides the first evidence that CypI trigger a unique ER reorganization of infected cells, rendering cells transiently impervious to a reinfection. This study further suggests that the HCV-induced ER rearrangement represents a key target for the development of new therapies.

C5A Protects Macaques from Vaginal Simian-Human Immunodeficiency Virus Challenge.

A safe and effective vaginal microbicide could decrease human immunodeficiency virus (HIV) transmission in women. Here, we evaluated the safety and microbicidal efficacy of a short amphipathic peptide, C5A, in a rhesus macaque model. We found that a vaginal application of C5A protects 89% of the macaques from a simian-human immunodeficiency virus (SHIV-162P3) challenge. We observed no signs of lesions or inflammation in animals vaginally treated with repeated C5A applications. With its noncellular cytotoxic activity and rare mechanism of action, C5A represents an attractive microbicidal candidate.

The Novel Cyclophilin Inhibitor CPI-431-32 Concurrently Blocks HCV and HIV-1 Infections via a Similar Mechanism of Action.

HCV-related liver disease is the main cause of morbidity and mortality of HCV/HIV-1 co-infected patients. Despite the recent advent of anti-HCV direct acting antivirals (DAAs), the treatment of HCV/HIV-1 co-infected patients remains a challenge, as these patients are refractory to most therapies and develop liver fibrosis, cirrhosis and liver cancer more often than HCV mono-infected patients. Until the present study, there was no suitable in vitro assay to test the inhibitory activity of drugs on HCV/HIV-1 co-infection. Here we developed a novel in vitro "co-infection" model where HCV and HIV-1 concurrently replicate in their respective main host target cells--human hepatocytes and CD4+ T-lymphocytes. Using this co-culture model, we demonstrate that cyclophilin inhibitors (CypI), including a novel cyclosporin A (CsA) analog, CPI-431-32, simultaneously inhibits replication of both HCV and HIV-1 when added pre- and post-infection. In contrast, the HIV-1 protease inhibitor nelfinavir or the HCV NS5A inhibitor daclatasvir only blocks the replication of a single virus in the "co-infection" system. CPI-431-32 efficiently inhibits HCV and HIV-1 variants, which are normally resistant to DAAs. CPI-431-32 is slightly, but consistently more efficacious than the most advanced clinically tested CypI--alisporivir (ALV)--at interrupting an established HCV/HIV-1 co-infection. The superior antiviral efficacy of CPI-431-32 over ALV correlates with its higher potency inhibition of cyclophilin A (CypA) isomerase activity and at preventing HCV NS5A-CypA and HIV-1 capsid-CypA interactions known to be vital for replication of the respective viruses. Moreover, we obtained evidence that CPI-431-32 prevents the cloaking of both the HIV-1 and HCV genomes from cellular sensors. Based on these results, CPI-431-32 has the potential, as a single agent or in combination with DAAs, to inhibit both HCV and HIV-1 infections.

Cyclophilin and NS5A inhibitors, but not other anti-hepatitis C virus (HCV) agents, preclude HCV-mediated formation of double-membrane-vesicle viral factories.

Although the mechanisms of action (MoA) of nonstructural protein 3 inhibitors (NS3i) and NS5B inhibitors (NS5Bi) are well understood, the MoA of cyclophilin inhibitors (CypI) and NS5A inhibitors (NS5Ai) are not fully defined. In this study, we examined whether CypI and NS5Ai interfere with hepatitis C virus (HCV) RNA synthesis of replication complexes (RCs) or with an earlier step of HCV RNA replication, the creation of double-membrane vesicles (DMVs) essential for HCV RNA replication. In contrast to NS5Bi, both CypI and NS5Ai do not block HCV RNA synthesis by way of RCs, suggesting that they exert their antiviral activity prior to the establishment of enzymatically active RCs. We found that viral replication is not a precondition for DMV formation, since the NS3-NS5B polyprotein or NS5A suffices to create DMVs. Importantly, only CypI and NS5Ai, but not NS5Bi, mir-122, or phosphatidylinositol-4 kinase IIIα (PI4KIIIα) inhibitors, prevent NS3-NS5B-mediated DMV formation. NS3-NS5B was unable to create DMVs in cyclophilin A (CypA) knockdown (KD) cells. We also found that the isomerase activity of CypA is absolutely required for DMV formation. This not only suggests that NS5A and CypA act in concert to build membranous viral factories but that CypI and NS5Ai mediate their early anti-HCV effects by preventing the formation of organelles, where HCV replication is normally initiated. This is the first investigation to examine the effect of a large panel of anti-HCV agents on DMV formation, and the results reveal that CypI and NS5Ai act at the same membranous web biogenesis step of HCV RNA replication, thus indicating a new therapeutic target of chronic hepatitis C.

Bioengineering and semisynthesis of an optimized cyclophilin inhibitor for treatment of chronic viral infection.

Inhibition of host-encoded targets, such as the cyclophilins, provides an opportunity to generate potent high barrier to resistance antivirals for the treatment of a broad range of viral diseases. However, many host-targeted agents are natural products, which can be difficult to optimize using synthetic chemistry alone. We describe the orthogonal combination of bioengineering and semisynthetic chemistry to optimize the drug-like properties of sanglifehrin A, a known cyclophilin inhibitor of mixed nonribosomal peptide/polyketide origin, to generate the drug candidate NVP018 (formerly BC556). NVP018 is a potent inhibitor of hepatitis B virus, hepatitis C virus (HCV), and HIV-1 replication, shows minimal inhibition of major drug transporters, and has a high barrier to generation of both HCV and HIV-1 resistance.

Alisporivir inhibition of hepatocyte cyclophilins reduces HBV replication and hepatitis B surface antigen production.

BACKGROUND & AIMS: Cyclophilins are host factors required for hepatitis C virus replication. Cyclophilin inhibitors such as alisporivir have shown strong anti-hepatitis C virus activity in vitro and in clinical studies. However, little is known about whether hepatocyte cyclophilins are involved in the hepatitis B virus (HBV) life cycle. We investigated the effects of 2 cyclophilin inhibitors (alisporivir and NIM811) on HBV replication and hepatitis B surface antigen (HBsAg) production in cell lines. METHODS: Liver-derived cell lines producing full-length HBV and HBsAg particles, owing to stable (HepG2215) or transient (HuH-7) transfection, or infected with HBV (HepaRG cells; Invitrogen [Carlsbad, CA]), were incubated with alisporivir or NIM811 alone, or alisporivir in combination with a direct antiviral (telbivudine). The roles of individual cyclophilins in drug response was evaluated by small interfering RNA knockdown of cyclophilin (CYP)A, CYPC, or CYPD in HepG2215 cells, or CYPA knockdown in HuH-7 cells. The kinetics of antiviral activity were assessed based on levels of HBV DNA and HBsAg and Southern blot analysis. RESULTS: In HepG2215, HuH-7, and HepaRG cells, alisporivir reduced intracellular and secreted HBV DNA, in a dose-dependent manner. Knockdown of CYPA, CYPC, or CYPD (reduced by 80%) significantly reduced levels of HBV DNA and secreted HBsAg. Knockdown of CYPA significantly reduced secretion of HBsAg, leading to accumulation of intracellular HBsAg; the addition of alisporivir greatly reduced levels of HBsAg in these cells. The combination of alisporivir and telbivudine had greater antiviral effects than those of telbivudine or alisporivir alone. CONCLUSIONS: Alisporivir inhibition of cyclophilins in hepatocyte cell lines reduces replication of HBV DNA and HBsAg production and secretion. These effects are potentiated in combination with direct antiviral agents that target HBV-DNA polymerase.

HCV core residues critical for infectivity are also involved in core-NS5A complex formation.

Hepatitis C virus (HCV) infection is a major cause of liver disease. The molecular machinery of HCV assembly and particle release remains obscure. A better understanding of the assembly events might reveal new potential antiviral strategies. It was suggested that the nonstructural protein 5A (NS5A), an attractive recent drug target, participates in the production of infectious particles as a result of its interaction with the HCV core protein. However, prior to the present study, the NS5A-binding site in the viral core remained unknown. We found that the D1 domain of core contains the NS5A-binding site with the strongest interacting capacity in the basic P38-K74 cluster. We also demonstrated that the N-terminal basic residues of core at positions 50, 51, 59 and 62 were required for NS5A binding. Analysis of all substitution combinations of R50A, K51A, R59A, and R62A, in the context of the HCVcc system, showed that single, double, triple, and quadruple mutants were fully competent for viral RNA replication, but deficient in secretion of viral particles. Furthermore, we found that the extracellular and intracellular infectivity of all the mutants was abolished, suggesting a defect in the formation of infectious particles. Importantly, we showed that the interaction between the single and quadruple core mutants and NS5A was impaired in cells expressing full-length HCV genome. Interestingly, mutations of the four basic residues of core did not alter the association of core or NS5A with lipid droplets. This study showed for the first time that basic residues in the D1 domain of core that are critical for the formation of infectious extracellular and intracellular particles also play a role in core-NS5A interactions.

HCV NS5A and IRF9 compete for CypA binding.

BACKGROUND & AIMS: Cyclophilin A (CypA) is vital for HCV replication. Cyp inhibitors successfully decrease viral loads in HCV-infected patients. However, their mechanisms of action remain unknown. Since interferon (IFN) can also suppress HCV replication, we asked whether a link between CypA and the IFN response exists. METHODS: We used cellular and recombinant pulldown approaches to investigate the possibility of a specific association of CypA with host ligands. RESULTS: We found for the first time that CypA binds to a major component of the IFN response - the IFN regulatory factor 9 (IRF9). IRF9 is the DNA-binding component of the transcriptional IFN-stimulated gene factor 3 (ISGF3). CypA binds directly to IRF9 via its peptidyl-prolyl isomerase (PPIase) pocket. Cyp inhibitors such as cyclosporine A (CsA) or non-immunosuppressive derivates such as alisporivir and SCY-635, prevent IRF9-CypA complex formation. CypA binds to the C-terminal IRF-association-domain (IAD), but not to the DNA-binding or linker domains of IRF9. Remarkably, CypA associates with the multimeric ISGF3 complex. We also obtained evidence that CypA neutralization enhances IFN-induced transcription. Interestingly, the hepatitis C virus (HCV) non-structural 5A (NS5A) protein, which is known to modulate the IFN response, competes with IRF9 for CypA binding and can prevent the formation of IRF9-CypA complexes. CONCLUSIONS: This study demonstrates for the first time that CypA binds specifically to a component of the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway, IRF9. This study also reveals a novel opportunity of HCV to modulate the IFN response via NS5A.

Correlation between NS5A dimerization and hepatitis C virus replication.

Hepatitis C virus (HCV) is the main agent of acute and chronic liver diseases leading to cirrhosis and hepatocellular carcinoma. The current standard therapy has limited efficacy and serious side effects. Thus, the development of alternate therapies is of tremendous importance. HCV NS5A (nonstructural 5A protein) is a pleiotropic protein with key roles in HCV replication and cellular signaling pathways. Here we demonstrate that NS5A dimerization occurs through Domain I (amino acids 1-240). This interaction is not mediated by nucleic acids because benzonase, RNase, and DNase treatments do not prevent NS5A-NS5A interactions. Importantly, DTT abrogates NS5A-NS5A interactions but does not affect NS5A-cyclophilin A interactions. Other reducing agents such as tris(2-carboxyethyl)phosphine and 2-mercaptoethanol also abrogate NS5A-NS5A interactions, implying that disulfide bridges may play a role in this interaction. Cyclophilin inhibitors, cyclosporine A, and alisporivir and NS5A inhibitor BMS-790052 do not block NS5A dimerization, suggesting that their antiviral effects do not involve the disruption of NS5A-NS5A interactions. Four cysteines, Cys-39, Cys-57, Cys-59, and Cys-80, are critical for dimerization. Interestingly, the four cysteines have been proposed to form a zinc-binding motif. Supporting this notion, NS5A dimerization is greatly facilitated by Zn(2+) but not by Mg(2+) or Mn(2+). Importantly, the four cysteines are vital not only for viral replication but also critical for NS5A binding to RNA, revealing a correlation between NS5A dimerization, RNA binding, and HCV replication. Altogether our data suggest that NS5A-NS5A dimerization and/or multimerization could represent a novel target for the development of HCV therapies.

Multiple mutations in hepatitis C virus NS5A domain II are required to confer a significant level of resistance to alisporivir.

Alisporivir is the most advanced host-targeting antiviral cyclophilin (Cyp) inhibitor in phase III studies and has demonstrated a great deal of promise in decreasing hepatitis C virus (HCV) viremia in infected patients. In an attempt to further elucidate the mechanism of action of alisporivir, HCV replicons resistant to the drug were selected. Interestingly, mutations constantly arose in domain II of NS5A. To demonstrate that these mutations are responsible for drug resistance, they were reintroduced into the parental HCV genome, and the resulting mutant viruses were tested for replication in the presence of alisporivir or in the absence of the alisporivir target, CypA. We also examined the effect of the mutations on NS5A binding to itself (oligomerization), CypA, RNA, and NS5B. Importantly, the mutations did not affect any of these interactions. Moreover, the mutations did not preserve NS5A-CypA interactions from alisporivir rupture. NS5A mutations alone render HCV only slightly resistant to alisporivir. In sharp contrast, when multiple NS5A mutations are combined, significant resistance was observed. The introduction of multiple mutations in NS5A significantly restored viral replication in CypA knockdown cells. Interestingly, the combination of NS5A mutations renders HCV resistant to all classes of Cyp inhibitors. This study suggests that a combination of multiple mutations in domain II of NS5A rather than a single mutation is required to render HCV significantly and universally resistant to Cyp inhibitors. This in accordance with in vivo data that suggest that alisporivir is associated with a low potential for development of viral resistance.

Sublimable C5A delivery provides sustained and prolonged anti-HIV microbicidal activities.

We have identified a short amphipathic helical peptide, called C5A, which exhibits potent microbicidal activities in vitro and which offers protection from vaginal HIV transmission in vivo in a humanized mouse model. However, there are many obstacles to overcome before C5A can be considered a true microbicidal candidate. First, it must be stabilized against enzymatic degradation in a continuously warm and moist environment. Second, it must be delivered in a controlled manner to achieve long-term and coitally independent efficacy. We demonstrate in this in vitro study that the combination of two matrices with different subliming properties ((hexamethylcyclotrisiloxane [HMCS] and cyclododecane [CDD]) containing 10% labile C5A yielded the best results in terms of controlled release and preserved anti-HIV activity of the peptide when pre-exposed to cell-free medium or cell culture at body temperature for up to 2 months.

HSV neutralization by the microbicidal candidate C5A.

Genital herpes is a major risk factor in acquiring human immunodeficiency virus type-1 (HIV-1) infection and is caused by both Herpes Simplex virus type 1 (HSV-1) and HSV-2. The amphipathic peptide C5A, derived from the non-structural hepatitis C virus (HCV) protein 5A, was shown to prevent HIV-1 infection but neither influenza nor vesicular stomatitis virus infections. Here we investigated the antiviral function of C5A on HSV infections. C5A efficiently inhibited both HSV-1 and HSV-2 infection in epithelial cells in vitro as well as in an ex vivo epidermal infection model. C5A destabilized the integrity of the viral HSV membrane. Furthermore, drug resistant HSV strains were inhibited by this peptide. Notably, C5A-mediated neutralization of HSV-1 prevented HIV-1 transmission. An in vitro HIV-1 transmigration assay was developed using primary genital epithelial cells and HSV infection increased HIV-1 transmigration. Treatment with C5A abolished HIV-1 transmigration by preventing HSV infection and by preserving the integrity of the genital epithelium that was severely compromised by HSV infection. In conclusion, this study demonstrates that C5A represents a multipurpose microbicide candidate, which neutralizes both HIV-1 and HSV, and which may interfere with HIV-1 transmission through the genital epithelium.

Preclinical characterization of naturally occurring polyketide cyclophilin inhibitors from the sanglifehrin family.

Cyclophilin inhibitors currently in clinical trials for hepatitis C virus (HCV) are all analogues of cyclosporine (CsA). Sanglifehrins are a group of naturally occurring cyclophilin binding polyketides that are structurally distinct from the cyclosporines and are produced by a microorganism amenable to biosynthetic engineering for lead optimization and large-scale production by fermentation. Preclinical characterization of the potential utility of this class of compounds for the treatment of HCV revealed that the natural sanglifehrins A to D are all more potent than CsA at disrupting formation of the NS5A-CypA, -CypB, and -CypD complexes and at inhibition of CypA, CypB, and CypD isomerase activity. In particular, sanglifehrin B (SfB) was 30- to 50-fold more potent at inhibiting the isomerase activity of all Cyps tested than CsA and was also shown to be a more potent inhibitor of the 1b subgenomic replicon (50% effective concentrations [EC50s] of 0.070 µM and 0.16 µM in Huh 5-2 and Huh 9-13 cells, respectively). Physicochemical and mouse pharmacokinetic analyses revealed low oral bioavailability (F<4%) and low solubility (<25 µM), although the half-lives (t1/2) of SfA and SfB in mouse blood after intravenous (i.v.) dosing were long (t1/2>5 h). These data demonstrate that naturally occurring sanglifehrins are suitable lead compounds for the development of novel analogues that are less immunosuppressive and that have improved metabolism and pharmacokinetic properties.

Syndecan-Fc hybrid molecule as a potent in vitro microbicidal anti-HIV-1 agent.

In the absence of a vaccine, there is an urgent need for the development of safe and effective topical microbicides to prevent the sexual transmission of human immunodeficiency virus type 1 (HIV-1). In this study, we proposed to develop a novel class of microbicides using syndecan as the antiviral agent. Specifically, we generated a soluble syndecan-Fc hybrid molecule by fusing the ectodomain of syndecan-1 to the Fc domain of a human IgG. We then tested the syndecan-Fc hybrid molecule for various in vitro microbicidal anti-HIV-1 properties. Remarkably, the syndecan-Fc hybrid molecule possesses multiple attractive microbicidal properties: (i) it blocks HIV-1 infection of primary targets including T cells, macrophages, and dendritic cells (DC); (ii) it exhibits a broad range of antiviral activity against primary HIV-1 isolates, multidrug resistant HIV-1 isolates, HIV-2, and simian immunodeficiency virus (SIV); (iii) it prevents transmigration of HIV-1 through human primary genital epithelial cells; (iv) it prevents HIV-1 transfer from dendritic cells to CD4(+) T cells; (v) it is potent when added 2 h prior to addition of HIV-1 to target cells; (vi) it is potent at a low pH; (vii) it blocks HIV-1 infectivity when diluted in genital fluids; and (viii) it prevents herpes simplex virus infection. The heparan sulfate chains of the syndecan-Fc hybrid molecule are absolutely required for HIV-1 neutralization. Several lines of evidence suggest that the highly conserved Arg298 in the V3 region of gp120 serves as the locus for the syndecan-Fc hybrid molecule neutralization. In conclusion, this study suggests that the syndecan-Fc hybrid molecule represents the prototype of a new generation of microbicidal agents that may have promise for HIV-1 prevention.

Hepatitis C virus NS5A anchor peptide disrupts human immunodeficiency virus.

In the absence of an effective vaccine, there is an urgent need for safe and effective antiviral agents to prevent transmission of HIV. Here, we report that an amphipathic alpha-helical peptide derived from the hepatitis C virus NS5A anchor domain (designated C5A in this article) that has been shown to be virocidal for the hepatitis C virus (HCV) also has potent antiviral activity against HIV. C5A exhibits a broad range of antiviral activity against HIV isolates, and it prevents infection of the three in vivo targets of HIV: CD4(+) T lymphocytes, macrophages, and dendritic cells by disrupting the integrity of the viral membrane and capsid core while preserving the integrity of host membranes. C5A can interrupt an ongoing T cell infection, and it can prevent transmigration of HIV through primary genital epithelial cells, infection of mucosal target cells and transfer from dendritic cells to T cells ex vivo, justifying future experiments to determine whether C5A can prevent HIV transmission in vivo.

Cell-free human immunodeficiency virus type 1 transcytosis through primary genital epithelial cells.

Although the transport of human immunodeficiency virus type 1 (HIV-1) through the epithelium is critical for HIV-1 colonization, the mechanisms controlling this process remain obscure. In the present study, we investigated the transcellular migration of HIV-1 as a cell-free virus through primary genital epithelial cells (PGECs). The absence of CD4 on PGECs implicates an unusual entry pathway for HIV-1. We found that syndecans are abundantly expressed on PGECs and promote the initial attachment and subsequent entry of HIV-1 through PGECs. Although CXCR4 and CCR5 do not contribute to HIV-1 attachment, they enhance viral entry and transcytosis through PGECs. Importantly, HIV-1 exploits both syndecans and chemokine receptors to ensure successful cell-free transport through the genital epithelium. HIV-1-syndecan interactions rely on specific residues in the V3 of gp120 and specific sulfations within syndecans. We found no obvious correlation between coreceptor usage and the capacity of the virus to transcytose. Since viruses isolated after sexual transmission are mainly R5 viruses, this suggests that the properties conferring virus replication after transmission are distinct from those conferring cell-free virus transcytosis through the genital epithelium. Although we found that cell-free HIV-1 crosses PGECs as infectious particles, the efficiency of transcytosis is extremely poor (less than 0.02% of the initial inoculum). This demonstrates that the genital epithelium serves as a major barrier against HIV-1. Although one cannot exclude the possibility that limited passage of cell-free HIV-1 transcytosis through an intact genital epithelium occurs in vivo, it is likely that the establishment of infection via cell-free HIV-1 transmigration is a rare event.

Trim5alpha accelerates degradation of cytosolic capsid associated with productive HIV-1 entry.

The TRIM5alpha (tripartite motif 5alpha protein) has been linked to the cross-species restriction in human immunodeficiency virus type 1 (HIV-1) infection of non-human cells, but the mechanism by which this occurs remains to be fully elucidated. Here we demonstrate that the capsid (CA) protein of HIV-1 is more rapidly degraded in cells expressing monkey TRIM5alpha than in cells expressing human TRIM5alpha. Other proteins encoded by Gag and Pol are not subject to TRIM5alpha-mediated accelerated degradation. The accelerated CA degradation by TRIM5alpha apparently occurs via a nonproteosomal pathway. TRIM5alpha selectively accelerates degradation of the CA population, which reached the cytosol of restrictive cells, but not the CA population, which ended into the vesicular compartment. Given that cytosolic CA represents "productively" entered cores, whereas vesicular CA represents "nonproductively" entered cores, our findings suggest that TRIM5alpha interrupts the infectious pathway of HIV-1 by acting on the incoming cytosolic CA. The mode of viral entry does not influence the accelerated degradation of cytosolic CA by TRIM5alpha. Thus, this study reveals a correlation between TRIM5alpha-mediated HIV-1 restriction and a selective degradation of cytosolic CA normally associated with productive viral entry.