A human immunodeficiency virus-transgenic mouse model for assessing interventions that block microbial-induced proviral expression

Delay of simian human immunodeficiency virus infection and control of viral replication in vaccinated macaques challenged in the presence of a topical microbicide

OBJECTIVE

Development of an effective vaccine or topical compound to prevent HIV transmission remains a major goal for control of the AIDS pandemic. Using a nonhuman primate model of heterosexual HIV-1 transmission, we tested whether a topical microbicide that reduces viral infectivity can potentiate the efficacy of a T-cell-based HIV vaccine.

DESIGN

A DNA prime and rAd5 virus boost vaccination strategy was employed, and a topical microbicide against the HIV nucleocapsid protein was used. To rigorously test the combination hypothesis, the vaccine constructs contained only two transgenes and the topical microbicide inhibitor was used at a suboptimal dose. Vaccinees were exposed in the absence and presence of the topical microbicide to repeated vaginal R5 simian human immunodeficiency virus (SHIV)(SF162P3) challenge at an escalating dose to more closely mimic high-risk exposure of women to HIV.

METHODS

Infection status was determined by PCR. Antiviral immune responses were evaluated by gp120 ELISA and intracellular cytokine staining.

RESULTS

A significant delay in SHIV acquisition (log-rank test; P = 0.0416) was seen only in vaccinated macaques that were repeatedly challenged in the presence of the topical microbicide. Peak acute viremia was lower (Mann-Whitney test; P = 0.0387) and viral burden was also reduced (Mann-Whitney test; P = 0.0252) in the combination-treated animals.

CONCLUSION

The combined use of a topical microbicide to lower the initial viral seeding/spread and a T-cell-based vaccine to immunologically contain the early virological events of mucosal transmission holds promise as a preventive approach to control the spread of the AIDS epidemic.

Molecular aspects involved in swimming exercise training reducing anhedonia in a rat model of depression

Patients suffering from depression frequently display hyperactivity of the hypothalamic-pituitary-adrenal axis (HPA) resulting in elevated cortisol levels. One main symptom of this condition is anhedonia. There is evidence that exercise training can be used as a rehabilitative intervention in the treatment of depressive disorders. In this scenario, the aim of the present study was to assess the effect of an aerobic exercise training protocol on the depressive-like behavior, anhedonia, induced by repeated dexamethasone administration. The study was carried out on adult male Wistar rats randomly divided into four groups: the "control group" (C), "exercise group" (E), "dexamethasone group" (D) and the "dexamethasone plus exercise group" (DE). The exercise training consisted of swimming (1 h/d, 5 d/wk) for 3 weeks, with an overload of 5% of the rat body weight. Every day rats were injected with either dexamethasone (D/DE) or saline solution (C/E). Proper positive controls, using fluoxetine, were run in parallel. Decreased blood corticosterone levels, reduced adrenal cholesterol synthesis and adrenal weight (HPA disruption), reduced preference for sucrose consumption and increased immobility time (depressive-like behavior), marked hippocampal DNA oxidation, increased IL-10 and total brain-derived neurotrophic factor (BDNF; pro-plus mature-forms) and a severe loss of body mass characterized the dexamethasone-treated animals. Besides increasing testosterone blood concentrations, the swim training protected depressive rats from the anhedonic state, following the same profile as fluoxetine, and also from the dexamethasone-induced impaired neurochemistry. The data indicate that physical exercise could be a useful tool in preventing and treating depressive disorders.

Short-course raltegravir intensification does not reduce persistent low-level viremia in patients with HIV-1 suppression during receipt of combination antiretroviral therapy

BACKGROUND

Combination antiretroviral therapy suppresses but does not eradicate human immunodeficiency virus type 1 (HIV-1) in infected persons, and low-level viremia can be detected despite years of suppressive antiretroviral therapy. Short-course (28-day) intensification of standard antiretroviral combination therapy is a useful approach to determine whether complete rounds of HIV-1 replication in rapidly cycling cells contribute to persistent viremia. We investigated whether intensification with the integrase inhibitor raltegravir decreases plasma HIV-1 RNA levels in patients receiving suppressive antiretroviral therapy.

METHODS

Subjects (n = 10) with long-term HIV-1 suppression receiving combination antiretroviral regimens had their regimens intensified for 4 weeks with raltegravir. Plasma HIV-1 RNA level was determined before, during, and after the 4-week intensification period, using a sensitive assay (limit of detection, 0.2 copies of HIV-1 RNA/mL of plasma). A 4-week intensification course was chosen to investigate potential HIV-1 replication in cells with relatively short (approximately 1-14-day) half-lives.

RESULTS

There was no evidence in any subject of a decline in HIV-1 RNA level during the period of raltegravir intensification or of rebound after discontinuation. Median levels of HIV-1 RNA before (0.17 log10 copies/mL), during (0.04 log10 copies/mL), and after (0.04 log10 copies/mL) raltegravir intensification were not significantly different (P > .1 for all comparisons in parametric analyses). High-performance liquid chromatography and mass spectroscopy experiments confirmed that therapeutic levels of raltegravir were achieved in plasma during intensification.

CONCLUSIONS

Intensification of antiretroviral therapy with a potent HIV-1 integrase inhibitor did not decrease persistent viremia in subjects receiving suppressive regimens, indicating that rapidly cycling cells infected with HIV-1 were not present. Eradication of HIV-1 from infected persons will require new therapeutic approaches.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT00618371.

Human immunodeficiency virus type 1 nucleocapsid inhibitors impede trans infection in cellular and explant models and protect nonhuman primates from infection

Here, we report that the S-acyl-2-mercaptobenzamide thioester (SAMT) class of human immunodeficiency virus type 1 (HIV-1) nucleocapsid protein (NCp7) inhibitors was able to prevent transmission of HIV-1 from infected cells, including primary cells. Furthermore, when SAMTs were introduced during an HIV-1 challenge of cervical explant tissue, inhibition of dissemination of infectious virus by cells emigrating from the tissue explants was observed. Preliminary studies using a rhesus macaque vaginal challenge model with mixed R5 and X4 simian-human immunodeficiency virus infection found that five of six monkeys were completely protected, with the remaining animal being partially protected, infected only by the R5 virus. These data suggest that SAMTs may be promising new drug candidates for further development in anti-HIV-1 topical microbicide applications.

CD4-specific transgenic expression of human cyclin T1 markedly increases human immunodeficiency virus type 1 (HIV-1) production by CD4+ T lymphocytes and myeloid cells in mice transgenic for a provirus encoding a monocyte-tropic HIV-1 isolate

Human immunodeficiency virus type 1 (HIV-1)-encoded Tat provides transcriptional activation critical for efficient HIV-1 replication by interacting with cyclin T1 and recruiting P-TEFb to efficiently elongate the nascent HIV transcript. Tat-mediated transcriptional activation in mice is precluded by species-specific structural differences that prevent Tat interaction with mouse cyclin T1 and severely compromise HIV-1 replication in mouse cells. We investigated whether transgenic mice expressing human cyclin T1 under the control of a murine CD4 promoter/enhancer cassette that directs gene expression to CD4(+) T lymphocytes and monocytes/macrophages (hu-cycT1 mice) would display Tat responsiveness in their CD4-expressing mouse cells and selectively increase HIV-1 production in this cellular population, which is infected primarily in HIV-1-positive individuals. To this end, we crossed hu-cycT1 mice with JR-CSF transgenic mice carrying the full-length HIV-1(JR-CSF) provirus under the control of the endogenous HIV-1 long terminal repeat and demonstrated that human cyclin T1 expression is sufficient to support Tat-mediated transactivation in primary mouse CD4 T lymphocytes and monocytes/macrophages and increases in vitro and in vivo HIV-1 production by these stimulated cells. Increased HIV-1 production by CD4(+) T lymphocytes was paralleled with their specific depletion in the peripheral blood of the JR-CSF/hu-cycT1 mice, which increased over time. In addition, increased HIV-1 transgene expression due to human cyclin T1 expression was associated with increased lipopolysaccharide-stimulated monocyte chemoattractant protein 1 production by JR-CSF mouse monocytes/macrophages in vitro. Therefore, the JR-CSF/hu-cycT1 mice should provide an improved mouse system for investigating the pathogenesis of various aspects of HIV-1-mediated disease and the efficacies of therapeutic interventions.

Optimization of unique, uncharged thioesters as inhibitors of HIV replication

A combinatorial chemistry approach was employed to prepare a restricted library of N-substituted S-acyl-2-mercaptobenzamide thioesters. It was shown that many members of this chemotype display anti-HIV activity via their ability to interact with HIV-1, HIV-2, SIV-infected cells, cell-free virus, and chronically and latently infected cells in a manner consistent with targeting of the highly conserved HIV-1 NCp7 zinc fingers. Compounds were initially screened using two different in vitro antiviral assays and evaluated for stability in neutral buffer containing 10% pooled human serum using a spectrophotometric assay. These data revealed that there was no significant correlation between thioester stability and antiviral activity, however, a slight inverse correlation between serum stability and virucidal activity was noted. Based on the virucidal capability and the ability to select lead compounds to inhibit virus expression from latently infected TNFalpha-induced U1 cells, we next determined if these compounds could prevent HIV cell-to-cell transmission. Several thioesters demonstrated potent inhibition of HIV cell-to-cell transmission with EC50 values in the 80-100 nM range. Thus, we have optimized a series of restricted thioesters and provided evidence that serum stability is not required for antiviral activity. Moreover, selected compounds show potential for development as topical microbicides.

Identification of granulocyte-macrophage colony-stimulating factor and lipopolysaccharide-induced signal transduction pathways that synergize to stimulate HIV type 1 production by monocytes from HIV type 1 transgenic mice

HIV-1-infected monocyte/macrophages located in lymph nodes and tissues are highly productive sources of HIV-1 and may function as a persistent reservoir contributing to the rebound viremia observed after highly active antiretroviral therapy is stopped. Mechanisms activating latently infected, primary monocyte/macrophages to produce HIV-1 were investigated using monocytes isolated from a transgenic mouse line carrying a full-length proviral clone of a monocyte-tropic HIV-1 isolate, HIV-1(JR-CSF), regulated by the endogenous long terminal repeat (LTR) (JR-CSF mice). Granulocyte-macrophage colony-stimulating factor (GM-CSF) combined with lipopolysaccharide (LPS) induced infectious HIV-1 production by JR-CSF mouse monocytes over 10-fold and 100-fold higher than that stimulated by GM-CSF or LPS alone, respectively. We examined mechanisms of GM-CSF synergy with LPS and demonstrated that GM-CSF up-regulated the LPS receptor, TLR-4, and also synergized with LPS to activate mitogen-activated protein (MAP) kinase/ERK kinase and the Sp1 transcription factor. Inhibitors of either MAP kinase/ERK kinase or p38 kinase but not PI 3-kinase potently suppressed GM-CSF and LPS-induced HIV-1 production by JR-CSF mouse monocytes. Because Sp1 is activated by both the MAP kinase/ERK kinase and p38 kinase pathways, we postulate that synergistic activation of these pathways by GM-CSF and LPS induced sufficient levels of Sp1 to activate the HIV-1 LTR in a Tat-independent manner and induced HIV-1 production by JR-CSF mouse monocytes. Thus, our study delineated the pathway of HIV-1 LTR activation by GM-CSF and LPS and indicated that JR-CSF transgenic mice may provide a new in vitro and in vivo system for investigating the mechanism by which inflammatory and infectious stimuli activate HIV-1 production from latently infected monocytes.

Focal glomerulosclerosis in proviral and c-fms transgenic mice links Vpr expression to HIV-associated nephropathy

Clinical and morphologic features of human immunodeficiency virus (HIV)-associated nephropathy (HIVAN), such as proteinuria, sclerosing glomerulopathy, tubular degeneration, and interstitial disease, have been modeled in mice bearing an HIV proviral transgene rendered noninfectious through a deletion in gag/pol. Exploring the genetic basis of HIVAN, HIV transgenic mice bearing mutations in either or both of the accessory genes nef and vpr were created. Proteinuria and focal glomerulosclerosis (FGS) only developed in mice with an intact vpr gene. Transgenic mice bearing a simplified proviral DNA (encoding only Tat and Vpr) developed renal disease characterized by FGS in which Vpr protein was localized to glomerular and tubular epithelia by immunohistochemistry. The dual transgenic progeny of HIV[Tat/Vpr] mice bred to HIV[DeltaVpr] proviral transgenic mice displayed a more severe nephropathy with no apparent increase in Vpr expression, implying that multiple viral genes contribute to HIVAN. However, the unique contribution of macrophage-specific Vpr expression in the development of glomerular disease was underscored by the induction of FGS in multiple murine lines bearing a c-fms/vpr transgene.

McCoy cell line as a possible model containing CD4+ receptors for the study of HIV-1 replication

Several studies have recently shown the use of recombinant rabies virus as potential vector-viral vaccine for HIV-1. The sequence homology between gp 120 and rabies virus glycoprotein has been reported. The McCoy cell line has therefore been used to show CD4+ or CD4+ like receptors. Samples of HIV-1 were isolated, when plasma of HIV-1 positive patients was inoculated in the McCoy cell line. The virus infection was then studied during successive virus passages. The proteins released in the extra cellular medium were checked for protein activity, by exposure to SDS Electrophoresis and blotting to nitro-cellulose filter, then reacting with sera of HIV positive and negative patients. Successive passages were performed, and showed viral replication, membrane permeabilization, the syncytium formation, and the cellular lysis (cytopathic effect). Flow cytometry analysis shows clear evidence that CD4+ receptors are present in this cell line, which enhances the likelihood of easy isolation and replication of HIV. The results observed allow the use of this cell line as a possible model for isolating HIV, as well as for carrying out studies of the dynamics of viral infection in several situations, including exposure to drugs in pharmacological studies, and possibly studies and analyses of the immune response in vaccine therapies.

Cutting edge: in vivo induction of integrated HIV-1 expression by mycobacteria is critically dependent on Toll-like receptor 2

Mycobacterial infection has been implicated as a possible factor in AIDS progression in populations where HIV-1 and Mycobacterium tuberculosis are coendemic. In support of this concept, we have previously shown that HIV-1-transgenic (Tg) mice infected with mycobacteria display enhanced viral gene and protein expression. In this study, we demonstrate that the induction of HIV-1 observed in this model is dependent on Toll-like receptor 2 (TLR2), a pattern recognition receptor known to be involved in mycobacteria-host interaction. Spleen cells from HIV-1-Tg mice deficient in TLR2 (Tg/TLR2(-/-)) were found to be completely defective in p24 production induced in response to live M. tuberculosis or Mycobacterium avium as well as certain mycobacterial products. Importantly, following in vivo mycobacterial infection, Tg/TLR2(-/-) mice failed to display the enhanced HIV-1 gag/env mRNA and p24 protein synthesis exhibited by wild-type Tg animals. Together, these results argue that TLR2 plays a crucial role in the activation of HIV-1 expression by mycobacterial coinfections.

Toll-like receptor 2 (TLR2) and TLR9 signaling results in HIV-long terminal repeat trans-activation and HIV replication in HIV-1 transgenic mouse spleen cells: implications of simultaneous activation of TLRs on HIV replication

Opportunistic infections are common in HIV-infected patients; they activate HIV replication and contribute to disease progression. In the present study we examined the role of Toll-like receptor 2 (TLR2) and TLR9 in HIV-long terminal repeat (HIV-LTR) trans-activation and assessed whether TLR4 synergized with TLR2 or TLR9 to induce HIV replication. Soluble Mycobacterium tuberculosis factor (STF) and phenol-soluble modulin from Staphylococcus epidermidis induced HIV-LTR trans-activation in human microvessel endothelial cells cotransfected with TLR2 cDNA. Stimulation of ex vivo spleen cells from HIV-1 transgenic mice with TLR4, TLR2, and TLR9 ligands (LPS, STF, and CpG DNA, respectively) induced p24 Ag production in a dose-dependent manner. Costimulation of HIV-1 transgenic mice spleen cells with LPS and STF or CpG DNA induced TNF-alpha and IFN-gamma production in a synergistic manner and p24 production in an additive fashion. In the THP-1 human monocytic cell line stably expressing the HIV-LTR-luciferase construct, LPS and STF also induced HIV-LTR trans-activation in an additive manner. This is the first time that TLR2 and TLR9 and costimulation of TLRs have been shown to induce HIV replication. Together these results underscore the importance of TLRs in bacterial Ag- and CpG DNA-induced HIV-LTR trans-activation and HIV replication. These observations may be important in understanding the role of the innate immune system and the molecular mechanisms involved in the increased HIV replication and HIV disease progression associated with multiple opportunistic infections.

In vivo antiviral activity of novel human immunodeficiency virus type 1 nucleocapsid p7 zinc finger inhibitors in a transgenic murine model

Control of human immunodeficiency virus through the use of inexpensive chemotherapeutics, with minimal side effects and decreased potential for engendering resistant virus, is a long-term therapeutic goal. In principle, this goal can be accomplished if viral replication in reservoirs of chronically and latently infected cells is addressed. As a first step, we have developed novel antiviral compounds based on a 2-mercaptobenzamide thioester chemotype, including the pyridinioalkanoyl thioesters, which specifically target the zinc fingers of the human immunodeficiency virus nucleocapsid protein (NCp7). Using these compounds in a murine transgenic model, in which infectious human immunodeficiency virus is induced from an integrated provirus, we show inhibition of transgenic spleen cell p24 expression with potencies comparable to acute infection assays using human peripheral blood lymphocytes. More importantly, transgenic mice treated in vivo with two 2-mercaptobenzamide thioesters expressed significantly lower plasma p24, and splenocytes from these animals produced fewer infectious virions. Thus, these thioesters may provide an effective means for inhibiting the expression of human immunodeficiency virus from integrated viral reservoirs.