Inhibition of HIV-1 virus replication using small soluble Tat peptides

Cyclin-Dependent Kinase 2 Inhibitors in Cancer Therapy: An Update

Cyclin-dependent kinase 2 (CDK2) drives the progression of cells into the S- and M-phases of the cell cycle. CDK2 activity is largely dispensable for normal development, but it is critically associated with tumor growth in multiple cancer types. Although the role of CDK2 in tumorigenesis has been controversial, emerging evidence proposes that selective CDK2 inhibition may provide a therapeutic benefit against certain tumors, and it continues to appeal as a strategy to exploit in anticancer drug development. Several small-molecule CDK2 inhibitors have progressed to the clinical trials. However, a CDK2-selective inhibitor is yet to be discovered. Here, we discuss the latest understandings of the role of CDK2 in normal and cancer cells, review the core pharmacophores used to target CDK2, and outline strategies for the rational design of CDK2 inhibitors. We attempt to provide an outlook on how CDK2-selective inhibitors may open new avenues for cancer therapy.

HIV-1 Proteins Influence Novelty-Seeking Behavior and Alter Region-Specific Transcriptional Responses to Chronic Nicotine Treatment in HIV-1Tg Rats

INTRODUCTION

Clinical studies suggest that HIV-1-infected patients are more likely to use or abuse addictive drugs than is the general population. We hypothesized that HIV-1 proteins impact novelty-seeking behavior and enhance the transcriptional response to nicotine in genes implicated in both novelty-seeking behavior and drug addiction.

METHODS

We assessed the effects of HIV-1 proteins on novelty-seeking behavior by comparing baseline activity differences of HIV-1Tg and F344 control rats in the open-field test. One day after behavioral testing, all rats began daily subcutaneous injections of either nicotine (0.4 mg/kg, base) or saline (the same for each rat) for 27 days. At the end of treatment, the prefrontal cortex, nucleus accumbens, and ventral tegmental area were collected for RNA expression analysis of genes in the receptor families for dopamine, GABA, glutamate, and serotonin.

RESULTS

Significant strain difference was detected in the distance moved in the center, such that HIV-1Tg rats traveled greater distance in the center of the arena than did F344 rats. Quantitative RT-PCR analysis showed that mRNA from Drd3 and Grm2 in the prefrontal cortex and Drd5 and Gabra6 in the ventral tegmental area was significantly upregulated, whereas that of Drd5 in the nucleus accumbens was downregulated in HIV-1Tg rats compared with F344 rats. Further, more addiction-related genes were significantly modulated by nicotine in each brain region in the HIV-1Tg rats than in the control animals.

CONCLUSIONS

HIV-1 proteins may affect novelty-seeking behavior and modulate the expression of genes related to drug addiction and novelty-seeking behavior.

IMPLICATIONS

HIV-1 viral proteins and chronic nicotine treatment impact the expression of genes involved in novelty-seeking behavior and addiction in three brain regions of the HIV-1 transgenic rat. These findings implicate that HIV-1 proteins may be involved in novelty-seeking behavior and in modulating the expression of genes related to drug addiction and novelty seeking.

Recent advances in the identification of Tat-mediated transactivation inhibitors: progressing toward a functional cure of HIV

The current anti-HIV combination therapy does not eradicate the virus that persists mainly in quiescent infected CD4(+) T cells as a latent integrated provirus that resumes after therapy interruption. The Tat-mediated transactivation (TMT) is a critical step in the HIV replication cycle that could give the opportunity to reduce the size of latent reservoirs. More than two decades of research led to the identification of various TMT inhibitors. While none of them met the criteria to reach the market, the search for a suitable TMT inhibitor is still actively pursued. Really promising compounds, including one in a Phase III clinical trial, have been recently identified, thus warranting an update.

Conditional Tat protein brain expression in the GT-tg bigenic mouse induces cerebral fractional anisotropy abnormalities

Cerebral white matter changes including tissue water diffusion abnormalities detected with diffusion tensor magnetic resonance imaging (DTI) are commonly found in humans with Human Immunodeficiency Virus (HIV) infection, as well as in animal models of the disorder. The severities of some of these abnormalities have been reported to correlate with measures of disease progression or severity, or with the degree of cognitive dysfunction. Accordingly, DTI may be a useful translational biomarker. HIV-Tat protein appears to be an important factor in the viral pathogenesis of HIV-associated neurotoxicity. We previously reported cerebral gray matter density reductions in the GT-tg bigenic mouse treated with doxycycline (Dox) to conditionally induce Tat protein expression. Presently, we administered intraperitoneal (i.p.) Dox (100 mg/kg/day) for 7 days to GT-tg mice to determine whether induction of conditional Tat expression led to the development of cerebral DTI abnormalities. Perfused and fixed brains from eight GT-tg mice administered Dox and eight control mice administered saline i.p. were extracted and underwent DTI scans on a 9.4 Tesla scanner. A whole brain analysis detected fractional anisotropy (FA) reductions in several areas including insular and endopiriform regions, as well as within the dorsal striatum. These findings suggest that exposure to Tat protein is sufficient to induce FA abnormalities, and further support the use of the GT-tg mouse to model some effects of HIV.

Autophagy restricts HIV-1 infection by selectively degrading Tat in CD4+ T lymphocytes

Autophagy is a ubiquitous mechanism involved in the lysosomal-mediated degradation of cellular components when they are engulfed in vacuoles called autophagosomes. Autophagy is also recognized as an important regulator of the innate and adaptive immune responses against numerous pathogens, which have, therefore, developed strategies to block or use the autophagy machinery to their own benefit. Upon human immunodeficiency virus type 1 (HIV-1) infection, viral envelope (Env) glycoproteins induce autophagy-dependent apoptosis of uninfected bystander CD4(+) T lymphocytes, a mechanism likely contributing to the loss of CD4(+) T cells. In contrast, in productively infected CD4(+) T cells, HIV-1 is able to block Env-induced autophagy in order to avoid its antiviral effect. To date, nothing is known about how autophagy restricts HIV-1 infection in CD4(+) T lymphocytes. Here, we report that autophagy selectively degrades the HIV-1 transactivator Tat, a protein essential for viral transcription and virion production. We demonstrated that this selective autophagy-mediated degradation of Tat relies on its ubiquitin-independent interaction with the p62/SQSTM1 adaptor. Taken together, our results provide evidence that the anti-HIV effect of autophagy is specifically due to the degradation of the viral transactivator Tat but that this process is rapidly counteracted by the virus to favor its replication and spread.

IMPORTANCE

Autophagy is recognized as one of the most ancient and conserved mechanisms of cellular defense against invading pathogens. Cross talk between HIV-1 and autophagy has been demonstrated depending on the virally challenged cell type, and HIV-1 has evolved strategies to block this process to replicate efficiently. However, the mechanisms by which autophagy restricts HIV-1 infection remain to be elucidated. Here, we report that the HIV-1 transactivator Tat, a protein essential for viral replication, is specifically degraded by autophagy in CD4(+) T lymphocytes. Both Tat present in infected cells and incoming Tat secreted from infected cells are targeted for autophagy degradation through a ubiquitin-independent interaction with the autophagy receptor p62/SQSTM1. This study is the first to demonstrate that selective autophagy can be an antiviral process by degrading a viral transactivator. In addition, the results could help in the design of new therapies against HIV-1 by specifically targeting this mechanism.

Break CDK2/Cyclin E1 interface allosterically with small peptides

Most inhibitors of Cyclin-dependent kinase 2 (CDK2) target its ATP-binding pocket. It is difficult, however, to use this pocket to design very specific inhibitors because this catalytic pocket is highly conserved in the protein family of CDKs. Here we report some short peptides targeting a noncatalytic pocket near the interface of the CDK2/Cyclin complex. Docking and molecular dynamics simulations were used to select the peptides, and detailed dynamical network analysis revealed that these peptides weaken the complex formation via allosteric interactions. Our experiments showed that upon binding to the noncatalytic pocket, these peptides break the CDK2/Cyclin complex partially and diminish its kinase activity in vitro. The binding affinity of these peptides measured by Surface Plasmon Resonance can reach as low as 0.5 µM.

Anxiety-like behavior of mice produced by conditional central expression of the HIV-1 regulatory protein, Tat

RATIONALE

Human immunodeficiency virus (HIV) infection is associated with substantial increases in generalized anxiety. The HIV regulatory protein, transactivator of transcription (Tat), has been implicated in the neuropathogenesis related to HIV-1 infection. However, direct examination of the effect of Tat on behavioral measures of anxiety has not been demonstrated.

OBJECTIVE

To identify whether expression of the Tat1-86 protein exerts dose-dependent and persistent anxiety-like effects in a whole animal model, the GT-tg bigenic mouse.

METHODS

GT-tg mice and C57BL/6J controls were administered doxycycline in a dose- (0, 50, 100, or 125 mg/kg, i.p., for 7 days) or duration- (100 mg/kg, i.p., for 0, 1, 3, 5, or 14 days) dependent manner to induce Tat1-86 in brain. Mice were assessed for anxiety-like behavior in an open field, social interaction, or marble burying task 0, 7, and/or 14 days later. Central expression of Tat1-86 protein was verified with Western blot analyses.

RESULTS

Doxycycline produced no effects on C57BL/6J controls that lacked the Tat1-86 transgene. Among GT-tg mice, doxycycline (100 mg/kg for 3, 5, or 7 days) significantly increased anxiety-like behavior in all tasks, commensurate with enhanced Western blot labeling of Tat1-86 protein in brain, displaying optimal effects with the 7-day regimen. Greater exposure to doxycycline (either 125 mg/kg for 7 days or 100 mg/kg for 14 days) impaired locomotor behavior; whereas lower dosing (below 100 mg/kg) produced only transient increases in anxiety-like behavior.

CONCLUSIONS

Expression of HIV-1-Tat1-86 in GT-tg mouse brain produces exposure-dependent, persistent increases in anxiety-like behavior.

The use of Nanotrap particles technology in capturing HIV-1 virions and viral proteins from infected cells

HIV-1 infection results in a chronic but incurable illness since long-term HAART can keep the virus to an undetectable level. However, discontinuation of therapy rapidly increases viral burden. Moreover, patients under HAART frequently develop various metabolic disorders and HIV-associated neuronal disease. Today, the main challenge of HIV-1 research is the elimination of the residual virus in infected individuals. The current HIV-1 diagnostics are largely comprised of serological and nucleic acid based technologies. Our goal is to integrate the nanotrap technology into a standard research tool that will allow sensitive detection of HIV-1 infection. This study demonstrates that majority of HIV-1 virions in culture supernatants and Tat/Nef proteins spiked in culture medium can be captured by nanotrap particles. To determine the binding affinities of different baits, we incubated target molecules with nanotrap particles at room temperature. After short sequestration, materials were either eluted or remained attached to nanotrap particles prior to analysis. The unique affinity baits of nanotrap particles preferentially bound HIV-1 materials while excluded albumin. A high level capture of Tat or Tat peptide by NT082 and NT084 particles was measured by western blot (WB). Intracellular Nef protein was captured by NT080, while membrane-associated Nef was captured by NT086 and also detected by WB. Selective capture of HIV-1 particles by NT073 and NT086 was measured by reverse transcriptase assay, while capture of infectious HIV-1 by these nanoparticles was demonstrated by functional transactivation in TZM-bl cells. We also demonstrated specific capture of HIV-1 particles and exosomes-containing TAR-RNA in patients' serum by NT086 and NT082 particles, respectively, using specific qRT-PCR. Collectively, our data indicate that certain types of nanotrap particles selectively capture specific HIV-1 molecules, and we propose to use this technology as a platform to enhance HIV-1 detection by concentrating viral proteins and infectious virions from infected samples.

RNA deep sequencing analysis reveals that nicotine restores impaired gene expression by viral proteins in the brains of HIV-1 transgenic rats

Persons infected with HIV-1 often develop neurologic disorders despite receiving highly active anti-retroviral therapy. Although the underlying mechanism is largely undetermined, our previous RNA-seq-based study showed that the expression of many genes was altered in the central nervous system (CNS) of HIV-1 transgenic (HIV-1Tg) rats. Because nicotine, a natural agonist of nicotinic acetylcholine receptors, exhibits a neuroprotective effect, we presently tested the hypothesis that nicotine restores the expression of altered genes in the CNS of HIV-1Tg rats. Adult male HIV-1Tg and F344 control strain rats were injected with either nicotine (0.25 mg/kg) or saline subcutaneously twice a day for 17 days. Gene expression in the prefrontal cortex (PFC), dorsal hippocampus (HIP), and dorsal striatum (STR) was evaluated using the RNA deep sequencing technique. We found that about 20% of the altered genes in the HIV-1Tg rat were affected by nicotine in each brain region, with the expression of most restored. Analysis of the restored genes showed distinct pathways corrected by nicotine in different brain regions of HIV-1Tg rats. Specifically, the two most significantly restored pathways were Wnt/β-catenin signaling and ephrin B signaling in the PFC, cAMP-responsive element-binding protein (CREB) signaling and glutathione metabolism pathway in the HIP, and tricarboxylic acid (TCA) cycle and calcium signaling in the STR. Together, our findings indicate that cholinergic modulators such as nicotine have beneficial effects on HIV-1-induced neurologic deficits.

Transcriptome sequencing of gene expression in the brain of the HIV-1 transgenic rat

The noninfectious HIV-1 transgenic (HIV-1Tg) rat was developed as a model of AIDs-related pathology and immune dysfunction by manipulation of a noninfectious HIV-1^gag-pol virus with a deleted 3-kb SphI-MscI fragment containing the 3′ -region of gag and the 5′ region of pol into F344 rats. Our previous studies revealed significant behavioral differences between HIV-1Tg and F344 control rats in their performance in the Morris water maze and responses to psychostimulants. However, the molecular mechanisms underlying these behavioral differences remain largely unknown. The primary goal of this study was to identify differentially expressed genes and enriched pathways affected by the gag-pol-deleted HIV-1 genome. Using RNA deep sequencing, we sequenced RNA transcripts in the prefrontal cortex, hippocampus, and striatum of HIV-1Tg and F344 rats. A total of 72 RNA samples were analyzed (i.e., 12 animals per group × 2 strains × 3 brain regions). Following deep-sequencing analysis of 50-bp paired-end reads of RNA-Seq, we used Bowtie/Tophat/Cufflinks suites to align these reads into transcripts based on the Rn4 rat reference genome and to measure the relative abundance of each transcript. Statistical analyses on each brain region in the two strains revealed that immune response- and neurotransmission-related pathways were altered in the HIV-1Tg rats, with brain region differences. Other neuronal survival-related pathways, including those encoding myelin proteins, growth factors, and translation regulators, were altered in the HIV-1Tg rats in a brain region-dependent manner. This study is the first deep-sequencing analysis of RNA transcripts associated the HIV-1Tg rat. Considering the functions of the pathways and brain regions examined in this study, our findings of abnormal gene expression patterns in HIV-1Tg rats suggest mechanisms underlying the deficits in learning and memory and vulnerability to drug addiction and other psychiatric disorders observed in HIV-positive patients.

Effect of mimetic CDK9 inhibitors on HIV-1-activated transcription

Potent anti-retroviral therapy has transformed HIV-1 infection into a chronic manageable disease; however, drug resistance remains a common problem that limits the effectiveness and clinical benefits of this type of treatment. The discovery of viral reservoirs in the body, in which HIV-1 may persist, has helped to explain why therapeutic eradication of HIV-1 has proved so difficult. In the current study, we utilized a combination of structure-based analysis of cyclin/CDK complexes with our previously published Tat peptide derivatives. We modeled the Tat peptide inhibitors with CDKs and found a particular pocket that showed the most stable binding site (Cavity 1) using in silico analysis. Furthermore, we were able to find peptide mimetics that bound to similar regions using in silico searches of a chemical library, followed by cell-based biological assays. Using these methods, we obtained the first-generation mimetic drugs and tested these compounds on HIV-1 long terminal repeat-activated transcription. Using biological assays followed by similar in silico analysis to find second-generation drugs resembling the original mimetic, we found the new targets of Cavity 1 and Cavity 2 regions on CDK9. We examined the second-generation mimetic against various viral isolates and observed a generalized suppression of most HIV-1 isolates. Finally, the drug inhibited viral replication in humanized mouse models of Rag2(-/-)γc(-/-) with no toxicity to the animals at tested concentrations. Our results suggest that it may be possible to model peptide inhibitors into available crystal structures and further find drug mimetics using in silico analysis.

Strategies to Block HIV Transcription: Focus on Small Molecule Tat Inhibitors

After entry into the target cell, the human immunodeficiency virus type I (HIV) integrates into the host genome and becomes a proviral eukaryotic transcriptional unit. Transcriptional regulation of provirus gene expression is critical for HIV replication. Basal transcription from the integrated HIV promoter is very low in the absence of the HIV transactivator of transcription (Tat) protein and is solely dependent on cellular transcription factors. The 5' terminal region (+1 to +59) of all HIV mRNAs forms an identical stem-bulge-loop structure called the Transactivation Responsive (TAR) element. Once Tat is made, it binds to TAR and drastically activates transcription from the HIV LTR promoter. Mutations in either the Tat protein or TAR sequence usually affect HIV replication, indicating a strong requirement for their conservation. The necessity of the Tat-mediated transactivation cascade for robust HIV replication renders Tat one of the most desirable targets for transcriptional therapy against HIV replication. Screening based on inhibition of the Tat-TAR interaction has identified a number of potential compounds, but none of them are currently used as therapeutics, partly because these agents are not easily delivered for an efficient therapy, emphasizing the need for small molecule compounds. Here we will give an overview of the different strategies used to inhibit HIV transcription and review the current repertoire of small molecular weight compounds that target HIV transcription.

Use of ATP analogs to inhibit HIV-1 transcription

Human immunodeficiency virus type 1 (HIV-1) is the etiological agent of AIDS. Chronic persistent infection is an important reason for the presence of "latent cell populations" even after Anti-Retroviral Therapy (ART). We have analyzed the effect of ATP analogs in inhibiting cdk9/T1 complex in infected cells. A third generation drug named CR8#13 is an effective inhibitor of Tat activated transcription. Following drug treatment, we observed a decreased loading of cdk9 onto the HIV-1 DNA. We found multiple novel cdk9/T1 complexes present in infected and uninfected cells with one complex being unique to infected cells. This complex is sensitive to CR8#13 in kinase assays. Treatment of PBMC with CR8#13 does not kill infected cells as compared to Flavopiridol. Interestingly, there is a difference in sensitivity of various clades to these analogs. Collectively, these results point to targeting novel complexes for inhibition of cellular proteins that are unique to infected cells.

Behavioral and molecular evidence for a feedback interaction between morphine and HIV-1 viral proteins

Morphine use and addiction is common among HIV infected individuals. There is an abundance of research supporting the effects of morphine and other mu opioid receptor (MOR) ligands, on the function of HIV-1 viral proteins and progression of HIV-1 viral infection to AIDS. On the other hand, there is much less research that investigates the possible effects of the persistent presence of HIV-1 viral proteins on the expression of the MOR and the analgesic and rewarding effects of MOR ligands such as morphine. While researchers have made a great deal of progress in the past several years, the overall investigation of the interaction between opiates such as morphine and HIV-1 viral proteins is largely unilateral. It has become widely accepted that drugs of abuse interact with HIV-1 viral proteins, but the mechanisms by which this takes place are only recently being discovered. Molecular and behavioral research suggests a feedback interaction between morphine and HIV-1 viral proteins. This interaction is mediated largely by the MOR as well as interplay between MOR ligands and cytokines, chemokines and their receptors. Some of the mechanisms underlying the feedback interaction between morphine and HIV-1 viral proteins has been demonstrated using cell culture and the recently engineered HIV-1 transgenic (HIV-1Tg) rat models.

The utility of the new generation of humanized mice to study HIV-1 infection: transmission, prevention, pathogenesis, and treatment

Substantial improvements have been made in recent years in the ability to engraft human cells and tissues into immunodeficient mice. The use of human hematopoietic stem cells (HSCs) leads to multi-lineage human hematopoiesis accompanied by production of a variety of human immune cell types. Population of murine primary and secondary lymphoid organs with human cells occurs, and long-term engraftment has been achieved. Engrafted cells are capable of producing human innate and adaptive immune responses, making these models the most physiologically relevant humanized animal models to date. New models have been successfully infected by a variety of strains of Human Immunodeficiency Virus Type 1 (HIV-1), accompanied by virus replication in lymphoid and non-lymphoid organs, including the gut-associated lymphoid tissue, the male and female reproductive tracts, and the brain. Multiple forms of virus-induced pathogenesis are present, and human T cell and antibody responses to HIV-1 are detected. These humanized mice are susceptible to a high rate of rectal and vaginal transmission of HIV-1 across an intact epithelium, indicating the potential to study vaccines and microbicides. Antiviral drugs, siRNAs, and hematopoietic stem cell gene therapy strategies have all been shown to be effective at reducing viral load and preventing or reversing helper T cell loss in humanized mice, indicating that they will serve as an important preclinical model to study new therapeutic modalities. HIV-1 has also been shown to evolve in response to selective pressures in humanized mice, thus showing that the model will be useful to study and/or predict viral evolution in response to drug or immune pressures. The purpose of this review is to summarize the findings reported to date on all new humanized mouse models (those transplanted with human HSCs) in regards to HIV-1 sexual transmission, pathogenesis, anti-HIV-1 immune responses, viral evolution, pre- and post-exposure prophylaxis, and gene therapeutic strategies.

Cyclin T1 stabilizes expression levels of HIV-1 Tat in cells

Transcription from HIV-1 proviral DNA is a rate-determining step for HIV-1 replication. Interaction between the cyclin T1 (CycT1) subunit of positive transcription elongation factor b (P-TEFb) and the Tat transactivator protein of HIV-1 is crucial for viral transcription. CycT1 also interacts directly with the transactivation-responsive element (TAR) located on the 5'end of viral mRNA, as well as with Tat through the Tat-TAR recognition motif (TRM). These molecular interactions represent a critical step for stimulation of HIV transcription. Thus, Tat and CycT1 are considered to be feasible targets for the development of novel anti-HIV therapies. In this study, we demonstrate that CycT1 is positively involved in the Tat protein stability. Selective degradation of CycT1 by small interfering RNA (siRNA) culminated in proteasome-mediated degradation of Tat and eventual inhibition of HIV-1 gene expression. We noted that the siRNA-mediated knockdown of CycT1 could inhibit HIV-1 transcription without affecting cell viability and Tat mRNA levels. These findings clearly indicate that CycT1 is a feasible therapeutic target, and inactivation or depletion of CycT1 should effectively inhibit HIV replication by destabilizing Tat and suppressing Tat-mediated HIV transcription.

Novel HIV-1 therapeutics through targeting altered host cell pathways

The emergence of drug-resistant HIV-1 strains presents a challenge for the design of new drugs. Anti-HIV compounds currently in use are the subject of advanced clinical trials using either HIV-1 reverse transcriptase, viral protease or integrase inhibitors. Recent studies show an increase in the number of HIV-1 variants resistant to anti-retroviral agents in newly infected individuals. Targeting host cell factors involved in the regulation of HIV-1 replication might be one way to combat HIV-1 resistance to the currently available anti-viral agents. A specific inhibition of HIV-1 gene expression could be expected from the development of compounds targeting host cell factors that participate in the activation of the HIV-1 LTR promoter. Here we discuss how targeting the host can be accomplished either by using small molecules to alter the function of the host's proteins such as p53 or cdk9, or by utilizing new advances in siRNA therapies to knock down essential host factors such as CCR5 and CXCR4. Finally, we will discuss how the viral protein interactomes should be used to better design therapeutics against HIV-1.

A novel binding pocket of cyclin-dependent kinase 2

The cyclin-dependent kinase 2 (cdk2) is a serine/threonine protein kinase that plays a key role in the cell cycle control system of all eukaryotic organisms. It has been a much studied drug target for potential anticancer therapy. Most cdk2 inhibitors in clinical development target almost exclusively the catalytic ATP-binding pocket of cdk2. However, several five amino-acid peptide inhibitors that are directed towards a noncatalytic binding pocket of cdk2 are reported here. Upon binding to this new pocket located at the cdk2 and cyclin interface, these peptide inhibitors are found to disrupt the cdk2/cyclin E complex partially and diminish its kinase activity in vitro.

Effect of transcription peptide inhibitors on HIV-1 replication

HIV-1 manipulates cellular machineries such as cyclin dependent kinases (cdks) and their cyclin elements, to stimulate virus production and maintain latent infection. Specifically, the HIV-1 viral protein Tat increases viral transcription by binding to the TAR promoter element. This binding event is mediated by the phosphorylation of Pol II by complexes such as cdk9/Cyclin T and cdk2/Cyclin E. Recent studies have shown that a Tat 41/44 peptide derivative prevents the loading of cdk2 onto the HIV-1 promoter, inhibiting gene expression and replication. Here we show that Tat peptide analogs computationally designed to dock at the cyclin binding site of cdk2 have the ability to bind to cdk2 and inhibit the association of cdk2 with the HIV promoter. Specifically, the peptide LAALS dissociated the complex and decreased kinase activity in vitro. We also describe our novel small animal model which utilizes humanized Rag2(-/-)gamma(c)(-/-) mice. This small peptide inhibitor induces a decrease in HIV-1 viral transcription in vitro and minimizes viral loads in vivo.

Spatial learning and memory in HIV-1 transgenic rats

HIV-1 infection of the central nervous system impairs neural, cognitive, and behavioral functioning in patients despite antiretroviral therapy. However, studying mechanisms underlying HIV-1-related neurological and cognitive dysfunction has been limited without an adequate animal model. A novel, noninfectious HIV-1 transgenic (HIV-1Tg) rat model was recently created that expresses an HIV-1 provirus with a deletion of functional gag and pol genes. This HIV-1Tg rat reportedly develops clinical manifestations of human HIV disease and thus appears to mimic the persistent infection that results from the presence of HIV viral proteins in the host. We evaluated the HIV-1Tg rat model using the Morris water maze, a popular paradigm for testing learning and memory deficits in rodents. Because of congenital cataracts in HIV-1Tg rats, however, the traditional use of visual navigational cues in this paradigm were precluded. We first designed a modified Morris water maze and demonstrated that neurologically intact rats can effectively learn the water maze in the absence of visual cues and in the presence of non-visual navigation cues. We then tested HIV-1Tg rats in this modified Morris water maze. These HIV-1Tg rats showed a deficit in learning how to swim to the location of the hidden platform but did not show a deficit in their memory of the general location of the hidden platform. These results suggest that the noninfectious HIV-1Tg rat can be a valid model for the behavioral studies of HIV-related neurological dysfunction.

Inhibition of HIV-1 integrase activity by synthetic peptides derived from the HIV-1 HXB2 Pol region of the viral genome

Peptides deriving from the HIV-1 HXB2 Pol gene sequence were evaluated for inhibitory activity against wild-type (WT) and mutant HIV-1 integrase (IN). The most potent peptide corresponding to a region on the reverse transcriptase (RT) subunit of the Pol polyprotein showed IC(50) value of 5 and 2 microM for 3'-processing and strand transfer, respectively. These peptides, and their analogs, may potentially be used in the elucidation of structural and functional epitopes of IN involved in protein-protein and protein-small molecule interactions.