Hybrids of Small-Molecule CD4 Mimics with Polyethylene Glycol Units as HIV Entry Inhibitors.

CD4 mimics are small molecules that inhibit the interaction of gp120 with CD4. We have developed several CD4 mimics. Herein, hybrid molecules consisting of CD4 mimics with a long alkyl chain or a PEG unit attached through a self-cleavable linker were synthesized. In anti-HIV activity, modification with a PEG unit appeared to be more suitable than modification with a long alkyl chain. Thus, hybrid molecules of CD4 mimics, with PEG units attached through an uncleavable linker, were developed and showed high anti-HIV activity and low cytotoxicity. In investigation of pharmacokinetics in a rhesus macaque, a hybrid compound had a more effective PK profile than that of the parent compound, and intramuscular injection was a more useful administration route to maintain the high blood concentration of the CD4 mimic than intravenous injection. The presented hybrid molecules of CD4 mimics with a PEG unit would be practically useful when combined with a neutralizing antibody.

Design, synthesis, and antiviral activity of a series of CD4-mimetic small-molecule HIV-1 entry inhibitors.

We presented our continuing stride to optimize the second-generation NBD entry antagonist targeted to the Phe43 cavity of HIV-1 gp120. We have synthesized thirty-eight new and novel analogs of NBD-14136, earlier designed based on a CH2OH "positional switch" hypothesis, and derived a comprehensive SAR. The antiviral data confirmed that the linear alcohol towards the "N" (C4) of the thiazole ring yielded more active inhibitors than those towards the "S" (C5) of the thiazole ring. The best inhibitor, NBD-14273 (compound 13), showed both improved antiviral activity and selectivity index (SI) against HIV-1HXB2 compared to NBD-14136. We also tested NBD-14273 against a large panel of 50 HIV-1 Env-pseudotyped viruses representing clinical isolates of diverse subtypes. The overall mean data indicate that antiviral potency against these isolates improved by ~3-fold, and SI also improved ~3-fold compared to NBD-14136. This new and novel inhibitor is expected to pave the way for further optimization to a more potent and clinically relevant inhibitor against HIV-1.

Long-Acting BMS-378806 Analogues Stabilize the State-1 Conformation of the Human Immunodeficiency Virus Type 1 Envelope Glycoproteins.

During human immunodeficiency virus type 1 (HIV-1) entry into cells, the viral envelope glycoprotein (Env) trimer [(gp120/gp41)3] binds the receptors CD4 and CCR5 and fuses the viral and cell membranes. CD4 binding changes Env from a pretriggered (state-1) conformation to more open downstream conformations. BMS-378806 (here called BMS-806) blocks CD4-induced conformational changes in Env important for entry and is hypothesized to stabilize a state-1-like Env conformation, a key vaccine target. Here, we evaluated the effects of BMS-806 on the conformation of Env on the surface of cells and virus-like particles. BMS-806 strengthened the labile, noncovalent interaction of gp120 with the Env trimer, enhanced or maintained the binding of most broadly neutralizing antibodies, and decreased the binding of poorly neutralizing antibodies. Thus, in the presence of BMS-806, the cleaved Env on the surface of cells and virus-like particles exhibits an antigenic profile consistent with a state-1 conformation. We designed novel BMS-806 analogues that stabilized the Env conformation for several weeks after a single application. These long-acting BMS-806 analogues may facilitate enrichment of the metastable state-1 Env conformation for structural characterization and presentation to the immune system.IMPORTANCE The envelope glycoprotein (Env) spike on the surface of human immunodeficiency virus type 1 (HIV-1) mediates the entry of the virus into host cells and is also the target for antibodies. During virus entry, Env needs to change shape. Env flexibility also contributes to the ability of HIV-1 to evade the host immune response; many shapes of Env raise antibodies that cannot recognize the functional Env and therefore do not block virus infection. We found that an HIV-1 entry inhibitor, BMS-806, stabilizes the functional shape of Env. We developed new variants of BMS-806 that stabilize Env in its natural state for long periods of time. The availability of such long-acting stabilizers of Env shape will allow the natural Env conformation to be characterized and tested for efficacy as a vaccine.

HbAHP-25 attenuates HIV-1 gp120 mediated inflammation and barrier dysfunction.

OBJECTIVES: Development of HbAHP-25, a peptide that prevents HIV-1 entry into cells by blocking gp120-CD4 interaction, as a topical anti-HIV drug, necessitates that it is first tested for toxic or abrasive effects on genital epithelial cells and also on the vaginal microbiome. The present study was, therefore, undertaken to investigate whether: (1) HbAHP-25 has any adverse effect on growth and membrane integrity of various cell lines, and (2) HbAHP-25 neutralizes gp120 mediated insults on genital epithelial cells. METHODS: MTT and trans-epithelial resistance (TER) assays were performed to assess the viability and integrity of epithelial cells. Real-time PCR and Immunofluorescence/Western blotting were used to decipher the expression of tight junction proteins, at the mRNA and protein levels, respectively. A multiplex cytokine assay was performed to quantify the cytokines. RESULTS: HbAHP-25 had no adverse effect on the viability of VK2/E6E7, End1/E6E7, Ect1/E6E7 and HEC-1A cells, and also on growth of lactobacilli. The barrier integrity of HbAHP-25-treated cells remained unaltered. Expression of tight junction proteins, Claudin-1 and ZO-1, at transcript and protein levels, remained unaltered in HbAHP-25-treated HEC-1A cells. Interestingly, HbAHP-25 treatment prevented the breach of barrier integrity caused by gp120. Further, HbAHP-25 did not elicit the expression of inflammatory cytokines. Instead, the in vitro induction of inflammatory cytokines by gp120 was also abrogated in the presence of HbAHP-25. CONCLUSION: HbAHP-25 is exceedingly safe to genital epithelial cells and attenuates HIV-1 gp120-mediated barrier dysfunction by limiting excessive inflammation. This study provides significant evidences in the favor of HbAHP-25's potential as a topical anti-HIV agent.

Effects of nanoparticle-encapsulated curcumin on HIV-gp120-associated neuropathic pain induced by the P2X3 receptor in dorsal root ganglia.

HIV-1 envelope glycoprotein (Glycoprotein 120, gp120) can directly stimulate primary sensory afferent neurons and cause chronic neuropathic pain. The P2X3 receptor in the dorsal root ganglia (DRG) is associated with the transmission of neuropathic pain. Curcumin isolated from the herb Curcuma rhizome has anti-inflammatory and anti-tumor effects. The water solubility, targeting and bioavailability of curcumin can be improved by nanoparticle encapsulation. In this study, we sought to explore the effects of nanoparticle-encapsulated curcumin (nano curcumin) on HIV-gp120-induced neuropathic pain mediated by the P2X3 receptor in DRG neurons. The results showed that mechanical and thermal hyperalgesia in rats treated with gp120 were increased compared to those in the control group. The expression levels of P2X3 mRNA and protein in rats treated with gp120 were higher than those in the control group. Nano curcumin treatment decreased mechanical hyperalgesia and thermal hyperalgesia and upregulated the expression levels of P2X3 mRNA and protein in rats treated with gp120. Nano curcumin treatment also reduced the ERK1/2 phosphorylation levels in gp120-treated rat DRG. In addition, P2X3 agonist α,ß-methylene ATP (α,ß-meATP)-induced currents in DRG neurons cultured with gp120 significantly decreased after co-treatment with nano curcumin. Therefore, nano curcumin treatment may inhibit P2X3 activation, decrease the sensitizing DRG primary afferents and relieve mechanical hyperalgesia and thermal hyperalgesia in gp120-treated rats.

Alpha-1-antitrypsin interacts with gp41 to block HIV-1 entry into CD4+ T lymphocytes.

BACKGROUND: Study of a clinic case reveals that alpha-1-antitrypsin (AAT) deficiency is related to CD4+ T cell count decline and AIDS progression, suggesting that AAT might be an endogenous inhibitor of HIV/AIDS. Previous study shows that AAT inhibits HIV-1 replication in infected host cells and the C-terminus fragment of AAT, VIRIP, interferes with HIV-1 infection. However, it is still unclear whether and how intact AAT inhibits HIV-1 infection. It is also unknown what the mechanism of AAT is and which critical step(s) are involved. RESULTS: In the present study, the C-terminus of AAT (C) was synthesized. C terminus-truncated AAT (ΔAAT) was also prepared by digesting AAT with metalloproteinase. Primary CD4+ T cells were then co-cultured with HIV-1 with the presence or absence of AAT/C/ΔAAT to detect cis-infection of HIV-1. The interaction between AAT/C/ΔAAT and gp120/gp41 was also measured. Meanwhile, HIV-1 reverse transcriptase activity and viral DNA integration were also detected in these lymphocytes. The results demonstrated that AAT and C, not ΔAAT, inhibited HIV-1 entry by directly interacting with gp41. Meanwhile, AAT, C and ΔAAT could not directly interfere with the steps of viral RNA reverse transcription and viral DNA integration. CONCLUSION: AAT inhibits HIV-1 entry by directly interacting with gp41 through its C-terminus and thereby inhibits HIV-1 infection.

The Low-Cost Compound Lignosulfonic Acid (LA) Exhibits Broad-Spectrum Anti-HIV and Anti-HSV Activity and Has Potential for Microbicidal Applications.

OBJECTIVES: Lignosulfonic acid (LA), a low-cost lignin-derived polyanionic macromolecule, was extensively studied for its anti-HIV and anti-HSV activity in various cellular assays, its mechanism of viral inhibition and safety profile as potential microbicide. RESULTS: LA demonstrated potent inhibitory activity of HIV replication against a wide range of R5 and X4 HIV strains and prevented the uptake of HIV by bystander CD4+ T cells from persistently infected T cells in vitro (IC50: 0.07 - 0.34 µM). LA also inhibited HSV-2 replication in vitro in different cell types (IC50: 0.42 - 1.1 µM) and in rodents in vivo. Furthermore, LA neutralized the HIV-1 and HSV-2 DC-SIGN-mediated viral transfer to CD4+ T cells (IC50: ~1 µM). In addition, dual HIV-1/HSV-2 infection in T cells was potently blocked by LA (IC50: 0.71 µM). No antiviral activity was observed against the non-enveloped viruses Coxsackie type B4 and Reovirus type 1. LA is defined as a HIV entry inhibitor since it interfered with gp120 binding to the cell surface of T cells. Pretreatment of PBMCs with LA neither increased expression levels of cellular activation markers (CD69, CD25 and HLA-DR), nor enhanced HIV-1 replication. Furthermore, we found that LA had non-antagonistic effects with acyclovir, PRO2000 or LabyA1 (combination index (CI): 0.46 - 1.03) in its anti-HSV-2 activity and synergized with tenofovir (CI: 0.59) in its anti-HIV-1 activity. To identify mechanisms of LA resistance, we generated in vitro a mutant HIV-1 NL4.3LAresistant virus, which acquired seven mutations in the HIV-1 envelope glycoproteins: S160N, V170N, Q280H and R389T in gp120 and K77Q, N113D and H132Y in gp41. Additionally, HIV-1 NL4.3LAresistant virus showed cross-resistance with feglymycin, enfuvirtide, PRO2000 and mAb b12, four well-described HIV binding/fusion inhibitors. Importantly, LA did not affect the growth of vaginal Lactobacilli strains. CONCLUSION: Overall, these data highlight LA as a potential and unique low-cost microbicide displaying broad anti-HIV and anti-HSV activity.

DNA vaccine molecular adjuvants SP-D-BAFF and SP-D-APRIL enhance anti-gp120 immune response and increase HIV-1 neutralizing antibody titers.

UNLABELLED: Broadly neutralizing antibodies (bNAbs) specific for conserved epitopes on the HIV-1 envelope (Env) are believed to be essential for protection against multiple HIV-1 clades. However, vaccines capable of stimulating the production of bNAbs remain a major challenge. Given that polyreactivity and autoreactivity are considered important characteristics of anti-HIV bNAbs, we designed an HIV vaccine incorporating the molecular adjuvants BAFF (B cell activating factor) and APRIL (a proliferation-inducing ligand) with the potential to facilitate the maturation of polyreactive and autoreactive B cells as well as to enhance the affinity and/or avidity of Env-specific antibodies. We designed recombinant DNA plasmids encoding soluble multitrimers of BAFF and APRIL using surfactant protein D as a scaffold, and we vaccinated mice with these molecular adjuvants using DNA and DNA-protein vaccination strategies. We found that immunization of mice with a DNA vaccine encoding BAFF or APRIL multitrimers, together with interleukin 12 (IL-12) and membrane-bound HIV-1 Env gp140, induced neutralizing antibodies against tier 1 and tier 2 (vaccine strain) viruses. The APRIL-containing vaccine was particularly effective at generating tier 2 neutralizing antibodies following a protein boost. These BAFF and APRIL effects coincided with an enhanced germinal center (GC) reaction, increased anti-gp120 antibody-secreting cells, and increased anti-gp120 functional avidity. Notably, BAFF and APRIL did not cause indiscriminate B cell expansion or an increase in total IgG. We propose that BAFF and APRIL multitrimers are promising molecular adjuvants for vaccines designed to induce bNAbs against HIV-1. IMPORTANCE: Recent identification of antibodies that neutralize most HIV-1 strains has revived hopes and efforts to create novel vaccines that can effectively stimulate HIV-1 neutralizing antibodies. However, the multiple immune evasion properties of HIV have hampered these efforts. These include the instability of the gp120 trimer, the inaccessibility of the conserved sequences, highly variable protein sequences, and the loss of HIV-1-specific antibody-producing cells during development. We have shown previously that tumor necrosis factor (TNF) superfamily ligands, including BAFF and APRIL, can be multitrimerized using the lung protein SP-D (surfactant protein D), enhancing immune responses. Here we show that DNA or DNA-protein vaccines encoding BAFF or APRIL multitrimers, IL-12p70, and membrane-bound HIV-1 Env gp140 induced tier 1 and tier 2 neutralizing antibodies in a mouse model. BAFF and APRIL enhanced the immune reaction, improved antibody binding, and increased the numbers of anti-HIV-1 antibody-secreting cells. Adaptation of this vaccine design may prove useful in designing preventive HIV-1 vaccines for humans.

Role of cations in the interaction of pradimicins with HIV-1 envelope gp120.

Pradimicins (PRM) are a unique class of nonpeptidic carbohydrate-binding agents that inhibit HIV infection by efficiently binding to the HIV-1 envelope gp120 glycans in the obligatory presence of Ca(2+). Surface plasmon resonance (SPR) data revealed that addition of EDTA dose-dependently results in lower binding signals of PRM-A to immobilized gp120. Pradimicin derivatives that lack the free carboxylic acid group on the C-18 position failed to bind gp120 and were devoid of significant antiviral activity. Ca(2+) was much more efficient for PRM-A binding to gp120 than Cd(2+), Ba(2+) or Sr(2+). Instead, calcium could not be replaced by any other mono- (i.e. K(+)), di- (i.e. Cu(2+), Mg(2+), Mn(2+), Fe(2+), Zn(2+)) or trivalent (i.e. Al,(3+), Fe(3+)) cation without complete loss of gp120 binding. However, Zn(2+), Mg(2+) and Mn(2+) added to a Ca(2+)- pradimicin mixture, prevented pradimicin from efficient binding to gp120 glycans. These data suggest that these bivalent cations may bind to pradimicins but lead to pradimicin-cation complexes that are unable to further coordinate with the glycans of gp120. Thus, in order to afford antiviral activity, only a few cations can (i) bind to pradimicin to form a dimeric complex and (ii) subsequently coordinate the pradimicin/cation interaction with gp120 glycans.

Prediction of virological response and assessment of resistance emergence to the HIV-1 attachment inhibitor BMS-626529 during 8-day monotherapy with its prodrug BMS-663068.

BACKGROUND: BMS-663068 is the phosphonooxymethyl prodrug of BMS-626529, a small-molecule attachment inhibitor that targets the HIV-1 envelope glycoprotein gp120 preventing it from binding to CD4 T cells. In vitro investigations have demonstrated considerable variation in susceptibility of different HIV-1 isolates to BMS-626529. BMS-663068 monotherapy in HIV-1-infected subjects produced a mean maximum change from baseline of -1.64 log10 copies per milliliter, but the response was variable. METHODS: In this analysis, baseline and day 8 samples were analyzed for susceptibility to BMS-626529 and the presence of known HIV-1 attachment inhibitor resistance mutations. In addition, predictors of virological response (maximal HIV-1 RNA decline ≥1 log10 copies per milliliter) and resistance selection were investigated. RESULTS: The only factor associated with reduced virological response was low baseline susceptibility to BMS-626529. There was no apparent relationship between virological response and baseline treatment experience, coreceptor tropism, plasma HIV-1 RNA level, or CD4 T-cell count. Examination of all positions with known BMS-626529 resistance mutations based on in vitro selection studies showed that gp120 M426L was the primary substitution most clearly associated with nonresponse to BMS-663068. There was minimal change in susceptibility to BMS-626529 over the course of the study and no clear evidence of emergence of a known HIV-1 attachment inhibitor resistance mutation in the majority of subjects as measured by standard population-based phenotypic and genotypic approaches. CONCLUSIONS: Nonresponse to BMS-663068 was associated with low baseline susceptibility to BMS-626529 and the presence of M426L. In this short-term trial, there was minimal evidence of selection for BMS-626529 high-level resistance over 8 days of monotherapy with BMS-663068 by population-based approaches.

Frequency of amino acid changes associated with resistance to attachment inhibitor BMS-626529 in R5- and X4-tropic HIV-1 subtype B.

OBJECTIVES: Resistance to attachment inhibitor BMS-626529, which inhibits the binding of HIV to CD4, involves mutations in the HIV-1 gp120 gene. There is a lack of information on the primary resistance of HIV-1 subtype B to attachment inhibitors, so we decided to investigate. METHODS: Sequences from 109 attachment-inhibitor-naive patients infected with HIV-1 subtype B were analysed for the presence of previously described in vivo resistance mutations associated with attachment inhibitor BMS-626529 and tropism determination. RESULTS: The M426L substitution associated with a reduced efficacy of the attachment inhibitor BMS-626529 was present at 7.3%. There was no difference in mutation distribution according to virus tropism (R5 or X4). CONCLUSIONS: The attachment inhibitor BMS-626529 is suitable for most patients infected with HIV-1 subtype B.

Early low-titer neutralizing antibodies impede HIV-1 replication and select for virus escape.

Single genome sequencing of early HIV-1 genomes provides a sensitive, dynamic assessment of virus evolution and insight into the earliest anti-viral immune responses in vivo. By using this approach, together with deep sequencing, site-directed mutagenesis, antibody adsorptions and virus-entry assays, we found evidence in three subjects of neutralizing antibody (Nab) responses as early as 2 weeks post-seroconversion, with Nab titers as low as 1∶20 to 1∶50 (IC(50)) selecting for virus escape. In each of the subjects, Nabs targeted different regions of the HIV-1 envelope (Env) in a strain-specific, conformationally sensitive manner. In subject CH40, virus escape was first mediated by mutations in the V1 region of the Env, followed by V3. HIV-1 specific monoclonal antibodies from this subject mapped to an immunodominant region at the base of V3 and exhibited neutralizing patterns indistinguishable from polyclonal antibody responses, indicating V1-V3 interactions within the Env trimer. In subject CH77, escape mutations mapped to the V2 region of Env, several of which selected for alterations of glycosylation. And in subject CH58, escape mutations mapped to the Env outer domain. In all three subjects, initial Nab recognition was followed by sequential rounds of virus escape and Nab elicitation, with Nab escape variants exhibiting variable costs to replication fitness. Although delayed in comparison with autologous CD8 T-cell responses, our findings show that Nabs appear earlier in HIV-1 infection than previously recognized, target diverse sites on HIV-1 Env, and impede virus replication at surprisingly low titers. The unexpected in vivo sensitivity of early transmitted/founder virus to Nabs raises the possibility that similarly low concentrations of vaccine-induced Nabs could impair virus acquisition in natural HIV-1 transmission, where the risk of infection is low and the number of viruses responsible for transmission and productive clinical infection is typically one.

HIV-1 gp120 and drugs of abuse: interactions in the central nervous system.

HIV-1 infection is a global public health problem with more than 34 million people living with HIV infection. Although great strides have been made in treating this epidemic with therapeutic agents, the increase in patient life span has been coincident with an increase in the prevalence of HIV-associated neurocognitive disorders (HAND). HAND is thought to result from the neurotoxic effects of viral proteins that are shed from HIV-infected microglial cells. One of the primary neurotoxins responsible for this effect is the HIV-1 glycoprotein gp120. Exposure of neurons to gp120 has been demonstrated to cause apoptosis in neurons, as well as numerous indirect effects such as an increase in inflammatory cytokines, an increase in oxidative stress, and an increase in permeability of the blood-brain barrier. In many patients, the use of drugs of abuse (DOA) exacerbates the neurotoxic effects of gp120. Cocaine, methamphetamine and morphine are three DOAs that are commonly used by those infected with HIV-1. All three of these DOAs have been demonstrated to increase oxidative stress in the CNS as well as to increase permeability of the blood-brain barrier. Numerous model systems have demonstrated that these DOAs have the capability of exacerbating the neurotoxic effects of gp120. This review will summarize the neurotoxic effects of gp120, the deleterious effects of cocaine, methamphetamine and morphine on the CNS, and the combined effects of gp120 in the context of these drugs.

Cocaine and HIV-1 interplay in CNS: cellular and molecular mechanisms.

Although antiretrovirals are the mainstay of therapy against HIV infection, neurological complications associated with the virus continue to hamper quality of life of the infected individuals. Drugs of abuse in the infected individuals further fuel the epidemic. Epidemiological studies have demonstrated that abuse of cocaine resulted in acceleration of HIV infection and the progression of NeuroAIDS. Cocaine has not only been shown to play a crucial role in promoting virus replication, but also has diverse but often deleterious effects on various cell types of the CNS. In the neuronal system, cocaine exposure results in neuronal toxicity and also potentiates gp120-induced neurotoxicity. In the astroglia and microglia, cocaine exposure leads to up-regulation of pro-inflammatory mediators such as cytokines and chemokines. These in turn, can lead to neuroinflammation and transmission of toxic responses to the neurons. Additionally, cocaine exposure can also lead to leakiness of the blood-brain barrier that manifests as enhanced transmigraiton of leukocytes/monocytes into the CNS. Both in vitro and in vivo studies have provided valuable tools in exploring the role of cocaine in mediating HIV-associated neuropathogenesis. This review summarizes previous studies on the mechanism(s) underlying the interplay of cocaine and HIV as it relates to the CNS.

Differential regulation of neurotoxin in HIV clades: role of cocaine and methamphetamine.

Studies have demonstrated that infection with HIV-1 (subtypes) clades might differentially contribute to HIV- 1-associated neuro cognitive disorder (HAND). Substance abuse and illicit drugs such as cocaine and methamphetamine (METH) are also known to play a role in neuronal impairments. Neurotoxin quinolinic acid (QUIN) and arachidonic acid (AA) metabolites are regulators of central nervous system (CNS) functions. These neurotoxins are dysregulated during HIV infection, and substance abuse exacerbates immune and neuronal dysfunctions, leading to dementia and neurocognitive impairments. Studies have demonstrated an association between HIV infection and substance abuse in terms of viral replication and disease progression in Neuro-AIDS. In this review, we briefly discuss the effect of cocaine and METH, and differential role of HIV-1 B and C induced indoleamine-2, 3-dioxygenase (IDO) and cyclooxygenase-2 (COX-2) mediated induction of neurotoxin QUIN and AA metabolites that implicate neuronal dysfunctions.

Effects of opiates and HIV proteins on neurons: the role of ferritin heavy chain and a potential for synergism.

Human immunodeficiency virus 1 (HIV-1) and its associated proteins can have a profound impact on the central nervous system. Co-morbid abuse of opiates, such as morphine and heroin, is often associated with rapid disease progression and greater neurological dysfunction. The mechanisms by which HIV proteins and opiates cause neuronal damage on their own and together are unclear. The emergence of ferritin heavy chain (FHC) as a negative regulator of the chemokine receptor CXCR4, a co-receptor for HIV, may prove to be important in elucidating the interaction between HIV proteins and opiates. This review summarizes our current knowledge of central nervous system damage inflicted by HIV and opiates, as well as the regulation of CXCR4 by opiate-induced changes in FHC protein levels. We propose that HIV proteins and opiates exhibit an additive or synergistic effect on FHC/CXCR4, thereby decreasing neuronal signaling and function.

Combinations of griffithsin with other carbohydrate-binding agents demonstrate superior activity against HIV Type 1, HIV Type 2, and selected carbohydrate-binding agent-resistant HIV Type 1 strains.

Carbohydrate-binding agents (CBAs) are potential HIV microbicidal agents with a high genetic barrier to resistance. We wanted to evaluate whether two mannose-specific CBAs, recognizing multiple and often distinct glycan structures on the HIV envelope gp120, can interact synergistically against HIV-1, HIV-2, and HIV-1 strains that were selected for resistance against particular CBAs [i.e., 2G12 mAb and microvirin (MVN)]. Paired CBA/CBA combinations mainly showed synergistic activity against both wild-type HIV-1 and HIV-2 but also 2G12 mAb- and MVN-resistant HIV-1 strains as based on the median effect principle with combination indices (CIs) ranging between 0.29 and 0.97. Upon combination, an increase in antiviral potency of griffithsin (GRFT) up to ∼12-fold (against HIV-1), ∼8-fold (against HIV-2), and ∼6-fold (against CBA-resistant HIV-1) was observed. In contrast, HHA/GNA combinations showed additive activity against wild-type HIV-1 and HIV-2 strains, but remarkable synergy with HHA and GNA was observed against 2G12 mAb- and MVN-resistant HIV-1 strains (CI, 0.64 and 0.49, respectively). Overall, combinations of GRFT and other CBAs showed synergistic activity against HIV-1, HIV-2, and even against certain CBA-resistant HIV-1 strains. The CBAs tested appear to have distinct binding patterns on the gp120 envelope and therefore do not necessarily compete with each other's glycan binding sites on gp120. As a result, there might be no steric hindrance between two different CBAs in their competition for glycan binding (except for the HHA/GNA combination). These data are encouraging for the use of paired CBA combinations in topical microbicide applications (e.g., creams, gels, or intravaginal rings) to prevent HIV transmission.

HIV type 1 coreceptor tropism, CCR5 genotype, and integrase inhibitor resistance profiles in Vietnam: implications for the introduction of new antiretroviral regimens.

In Vietnam, where an estimated 280,000 people will be HIV-positive by 2012, recommended antiretroviral regimens do not include more recently developed therapeutics, such as Integrase inhibitors (INI) and coreceptor antagonists. This study examined HIV-1 coreceptor tropism and INI drug resistance profiles, in parallel with CCR5 genotypes, in a cohort of 60 HIV-positive individuals from different regions of Vietnam. No evidence of INI resistance was detected. Some 40% of individuals had X4-tropic HIV-1, making them unsuitable for treatment with CCR5 antagonists. We identified a novel CCR5 variant-S272P-along with other, previously reported variants: G106R, C178R, W153C, R223Q, and S336I. Interestingly, CCR5 variants known to affect HIV-1 infectivity were observed only in individuals harboring X4-tropic virus. Together, this study presents valuable baseline information on HIV-1 INI resistance, coreceptor tropism, and CCR5 variants in HIV-positive individuals in Vietnam. This should help inform policy on the future use of novel antiretrovirals in Vietnam.

Development of resistance to VIR-353 with cross-resistance to the natural HIV-1 entry virus inhibitory peptide (VIRIP).

OBJECTIVE: Virus-inhibitory peptide (VIRIP) has been identified as a component of human hemofiltrate that blocks HIV-1 gp41-dependent fusion by interacting with the fusion peptide. A VIRIP analogue (VIR-576) has been shown to be effective in a phase I/II clinical trial. We have evaluated the activity and mechanism of HIV-1 resistance to VIRIP and its analogue, VIR-353. METHODS: Anti-HIV activity and passage of HIV-1 strains in cell culture were used to generate and identify mutations that confer resistance to VIRIP and VIR-353. Recombinant viruses harboring the most relevant mutations were generated and characterized. RESULTS: VIRIP and VIR-353 showed anti-HIV-1 activity with EC(50) of 28 and 0.3 µmol/l, respectively, and were active against virus resistant to BMS-155, AMD3100, T20, TAK-779 or nevirapine. Time of addition experiments showed that VIR-353 targets a time/site of action corresponding to gp41-dependent fusion. VIR-353-resistant virus was generated after 450 days in cell culture, suggesting a high genetic barrier for resistance. The VIR-353-resistant virus was cross-resistant to VIRIP but remained sensitive to T20, AMD3100 or zidovudine. Recombination of gp41 into a wild-type backbone partially recovered the resistant phenotype, but both gp120 and gp41 from the resistant virus were necessary to restore resistance to VIRIP or VIR-353. Site-directed mutagenesis confirmed the role of specific mutations and identified a combination of three mutations (A433T/V489I/V570I) as the most relevant to VIRIP resistance. CONCLUSION: VIRIP may interact with a region of gp41 that is essential for fusion but not the fusion peptide. Our results highlight interactions between gp41 and gp120 that may be required during the fusion process.

3D visualization of HIV virions by cryoelectron tomography.

The structure of the human immunodeficiency virus (HIV) and some of its components have been difficult to study in three-dimensions (3D) primarily because of their intrinsic structural variability. Recent advances in cryoelectron tomography (cryo-ET) have provided a new approach for determining the 3D structures of the intact virus, the HIV capsid, and the envelope glycoproteins located on the viral surface. A number of cryo-ET procedures related to specimen preservation, data collection, and image processing are presented in this chapter. The techniques described herein are well suited for determining the ultrastructure of bacterial and viral pathogens and their associated molecular machines in situ at nanometer resolution.