Efficacy of topical tenofovir against transmission of a tenofovir-resistant SHIV in macaques.

BACKGROUND: Topically delivered tenofovir (TFV) from intravaginal rings, tablets, or gels is being evaluated for HIV prevention. We previously demonstrated that TFV delivered vaginally by gel protected macaques from vaginal infection with SHIV. Here we investigated efficacy of the TFV gel against vaginal transmission of a TFV-resistant SHIV containing the K65R mutation (SHIV162P3K65R) and its relationship to drug levels in vaginal tissues. RESULTS: SHIV162P3K65R shows approximately a 5-fold reduction in susceptibility to TFV compared to wild-type SHIV. Efficacy was evaluated in pig-tailed macaques exposed vaginally twice-weekly (up to 10 weeks) to SHIV162P3K65R 30 min after receiving placebo (n = 6) or 1% TFV (n = 6) gel. Four of the six controls were infected after a median of 5 exposures. In contrast, five of six macaques that received TFV gel remained uninfected after 20 vaginal SHIV162P3K65R exposures, resulting in an estimated efficacy of 75%. The mean intracellular TFV-diphosphate (TFV-DP) concentrations in vaginal lymphocytes 4 h after a single gel dose were found to be high (1,631 fmol/10(6) cells, range 492-3,847) and within the in vitro IC75 range (1,206 fmol/10(6) cells) for SHIV162P3K65R. CONCLUSION: Both the modest resistance conferred by K65R and the high TFV-DP exposure in vaginal lymphocytes, likely explain the observed protection. The findings in this model do not predict complete loss of protection by topical TFV against vaginal exposure to HIV-1K65R viruses and provide a tissue drug target for high efficacy. These data will facilitate the development of TFV delivery platforms that have high activity on both wild-type and TFV-resistant viruses.

A longitudinal magnetization transfer imaging evaluation of brain injury in a macaque model of neuroAIDS.

Magnetization transfer (MT) imaging has been explored in prior studies of HIV patients and showed the potential capacity to assess brain injury after HIV infection. In the present study, adult pig-tailed macaques were infected with a highly neuropathogenic virus SIVsmmFGb. MT imaging was exploited to examine the monkey brains before simian immunodeficiency virus (SIV) inoculation and 2, 4, 8, 12, 16, and 20 weeks post-SIV inoculation. Blood samples were collected from each animal for monitoring CD4(+) and CD8(+) T cells before each MRI scan. The MT ratios (MTR) in several brain regions of interest were evaluated longitudinally. Significant reductions of MTR were observed in whole brain and selected regions of interest (genu, splenium, thalamus, caudate, centrum semiovale, frontal white matter, frontal gray matter, and putamen) in the SIV-infected monkeys, consistent with those reported previously in HIV patients. In particular, the longitudinal results indicate that abnormal MTR reduction can be detected as early as in 2 weeks and MTR may be more sensitive to the brain injury in cortical regions than in subcortical regions during acute SIV infection. In addition, MTR reduction in genu, centrum semiovale, and thalamus significantly correlated with the CD4(+) T cell percentage decrease. Also, the MTR reduction in thalamus correlated with the CD8(+) T cell percentage elevation. Taken together, this study reported the longitudinal evolution of MTR in different brain regions during SIV infection and further validates previous findings in HIV patients. The preliminary results suggest that MT imaging could be a robust and sensitive approach to characterize the neurodegeneration after SIV or HIV infection.

Longitudinal cerebral metabolic changes in pig-tailed macaques infected with the neurovirulent virus SIVsmmFGb.

Longitudinal cerebral metabolite changes in pig-tailed macaques inoculated with the simian immunodeficiency virus SIVsmmFGb were evaluated with in vivo proton MRS at 3 T. Blood sample collection, and MRS were carried out before and 2, 4, 8, 12, 16, 20, and 24 weeks after SIV inoculation. Significant reduction of N-acetylaspartate (NAA)/creatine (Cr) and choline (Cho)/Cr ratios in prefrontal gray matter (PGM) and glutamate/glutamine(Glx)/Cr ratio in striatum, and increase of myo-inositol (mI)/Cr in striatum were observed during acute SIV infection. The metabolite alterations during the SIVsmmFGb infection are largely in agreement with previous findings in other non-human primate models and HIV patients. Also, NAA/Cr in PGM and striatum and Glx/Cr in striatum are negatively correlated with the percentage of CD8+ T cells after the SIV infection, suggesting the interaction between brain metabolite and immune dysfunction. The present study complements previous studies by describing the time course of alterations of brain metabolites during SIVsmmFGb infection. The findings further demonstrate the efficacy of the SIVsmmFGb-infected macaque as a model to characterize central nervous system infection using novel neuroimaging approaches and also as a tool for exploration of novel and advanced neuroimaging techniques in HIV/AIDS studies.

Passive immunization of macaques with polyclonal anti-SHIV IgG against a heterologous tier 2 SHIV: outcome depends on IgG dose.

BACKGROUND: A key goal for HIV-1 envelope immunogen design is the induction of cross-reactive neutralizing antibodies (nAbs). As AIDS vaccine recipients will not be exposed to strains exactly matching any immunogens due to multiple HIV-1 quasispecies circulating in the human population worldwide, heterologous SHIV challenges are essential for realistic vaccine efficacy testing in primates. We assessed whether polyclonal IgG, isolated from rhesus monkeys (RMs) with high-titer nAbs (termed SHIVIG), could protect RMs against the R5-tropic tier-2 SHIV-2873Nip, which was heterologous to the viruses or HIV-1 envelopes that had elicited SHIVIG. RESULTS: SHIVIG demonstrated binding to HIV Gag, Tat, and Env of different clades and competed with the broadly neutralizing antibodies b12, VRC01, 4E10, and 17b. SHIVIG neutralized tier 1 and tier 2 viruses, including SHIV-2873Nip. NK-cell depletion decreased the neutralizing activity of SHIVIG 20-fold in PBMC assays. Although SHIVIG neutralized SHIV-2873Nip in vitro, this polyclonal IgG preparation failed to prevent acquisition after repeated intrarectal low-dose virus challenges, but at a dose of 400 mg/kg, it significantly lowered peak viremia (P = 0.001). Unexpectedly, single-genome analysis revealed a higher number of transmitted variants at the low dose of 25 mg/kg, implying increased acquisition at low SHIVIG levels. In vitro, SHIVIG demonstrated complement-mediated Ab-dependent enhancement of infection (C'-ADE) at concentrations similar to those observed in plasmas of RMs treated with 25 mg/kg of SHIVIG. CONCLUSION: Our primate model data suggest a dual role for polyclonal anti-HIV-1 Abs depending on plasma levels upon virus encounter.

Live attenuated Rev-independent Nef¯SIV enhances acquisition of heterologous SIVsmE660 in acutely vaccinated rhesus macaques.

BACKGROUND: Rhesus macaques (RMs) inoculated with live-attenuated Rev-Independent Nef¯ simian immunodeficiency virus (Rev-Ind Nef¯SIV) as adults or neonates controlled viremia to undetectable levels and showed no signs of immunodeficiency over 6-8 years of follow-up. We tested the capacity of this live-attenuated virus to protect RMs against pathogenic, heterologous SIVsmE660 challenges. METHODOLOGY/PRINCIPAL FINDINGS: Three groups of four RM were inoculated with Rev-Ind Nef¯SIV and compared. Group 1 was inoculated 8 years prior and again 15 months before low dose intrarectal challenges with SIVsmE660. Group 2 animals were inoculated with Rev-Ind Nef¯SIV at 15 months and Group 3 at 2 weeks prior to the SIVsmE660 challenges, respectively. Group 4 served as unvaccinated controls. All RMs underwent repeated weekly low-dose intrarectal challenges with SIVsmE660. Surprisingly, all RMs with acute live-attenuated virus infection (Group 3) became superinfected with the challenge virus, in contrast to the two other vaccine groups (Groups 1 and 2) (P=0.006 for each) and controls (Group 4) (P=0.022). Gene expression analysis showed significant upregulation of innate immune response-related chemokines and their receptors, most notably CCR5 in Group 3 animals during acute infection with Rev-Ind Nef¯SIV. CONCLUSIONS/SIGNIFICANCE: We conclude that although Rev-Ind Nef¯SIV remained apathogenic, acute replication of the vaccine strain was not protective but associated with increased acquisition of heterologous mucosal SIVsmE660 challenges.

Durable protection from vaginal simian-human immunodeficiency virus infection in macaques by tenofovir gel and its relationship to drug levels in tissue.

A vaginal gel containing 1% tenofovir (TFV) was found to be safe and effective in reducing HIV infection in women when used pericoitally. Because of the long intracellular half-life of TFV and high drug exposure in vaginal tissues, we hypothesized that a vaginal gel containing TFV may provide long-lasting protection. Here, we performed delayed-challenge experiments and showed that vaginal 1% TFV gel protected 4/6 macaques against vaginal simian-human immunodeficiency virus (SHIV) exposures occurring 3 days after gel application, demonstrating long-lasting protection. Despite continued gel dosing postinfection, neither breakthrough infection had evidence of drug resistance by ultrasensitive testing of SHIV in plasma and vaginal lavage. Analysis of the active intracellular tenofovir diphosphate (TFV-DP) in vaginal lymphocytes collected 4 h to 3 days after gel dosing persistently showed high TFV-DP levels (median, 1,810 fmol/10(6) cells) between 4 and 24 h that exceed the 95% inhibitory concentration (IC(95)), reflecting rapid accumulation and long persistence. In contrast to those in peripheral blood mononuclear cells (PBMCs) following oral dosing, TFV-DP levels in vaginal lymphocytes decreased approximately 7-fold by 3 days, exhibiting a much higher rate of decay. We observed a strong correlation between intracellular TFV-DP in vaginal lymphocytes, in vitro antiviral activity, and in vivo protection, suggesting that TFV-DP above the in vitro IC(95) in vaginal lymphocytes is a good predictor of high efficacy. Data from this model reveal an extended window of protection by TFV gel that supports coitus-independent use. The identification of protective TFV-DP concentrations in vaginal lymphocytes may facilitate the evaluation of improved delivery methods of topical TFV and inform clinical studies.

Vaccination against heterologous R5 clade C SHIV: prevention of infection and correlates of protection.

A safe, efficacious vaccine is required to stop the AIDS pandemic. Disappointing results from the STEP trial implied a need to include humoral anti-HIV-1 responses, a notion supported by RV144 trial data even though correlates of protection are unknown. We vaccinated rhesus macaques with recombinant simian immunodeficiency virus (SIV) Gag-Pol particles, HIV-1 Tat and trimeric clade C (HIV-C) gp160, which induced cross-neutralizing antibodies (nAbs) and robust cellular immune responses. After five low-dose mucosal challenges with a simian-human immunodeficiency virus (SHIV) that encoded a heterologous R5 HIV-C envelope (22.1% divergence from the gp160 immunogen), 94% of controls became viremic, whereas one third of vaccinees remained virus-free. Upon high-dose SHIV rechallenge, all controls became infected, whereas some vaccinees remained aviremic. Peak viremia was inversely correlated with both cellular immunity (p<0.001) and cross-nAb titers (p<0.001). These data simultaneously linked cellular as well as humoral immune responses with the degree of protection for the first time.

Longitudinal diffusion tensor imaging and perfusion MRI investigation in a macaque model of neuro-AIDS: a preliminary study.

The Simian immunodeficiency virus (SIV) infected macaque model exhibits neuropathological symptoms similar to those of HIV(+) patients, and is ideal for studying cognitive impairment and neuropathological sequelae of disease in repeated measurements. The aim of this study is to use Diffusion Tensor Imaging (DTI) and perfusion MRI to longitudinally access the disease development in SIV-infected monkeys under controlled conditions and to cross-validate our finding with MRI studies in HIV(+) patients. Three adult male pig-tailed macaques (Macaca nemestrina) were inoculated with the SIVsmmFGb virus. Blood was collected for enumeration of CD4+ and CD8+ T-cells. Serial time-sensitive high-resolution T(2)- weighted structural images, Cerebral Blood Flow (CBF) maps measured with the Continuous Arterial Spin Labeling (CASL) technique, and DTI images were obtained. Animals were sacrificed after 24 weeks. Cognitive behavioral tests were also carried out at each time point. Longitudinal changes in brain volume, CBF, and DTI in selected regions were analyzed statistically. In this study, CD4+ T-cell counts were found declined significantly after SIV infection in all macaques. No significant neurological behavior and brain volume changes were observed following virus inoculation. The CBF was found reduced in the caudate, inferior parietal cortex, and the prefrontal cortex. Fractional Anisotropy (FA) values in the whole brain and several Regions of Interest (ROIs) decreased significantly. These longitudinal changes in CBF and FA are correlated with CD4+ T-cell depletion and/or CD4:CD8 ratio. The MRI findings from this pilot study agree with previous results in HIV(+) patients.

Prime-boost vaccination with heterologous live vectors encoding SIV gag and multimeric HIV-1 gp160 protein: efficacy against repeated mucosal R5 clade C SHIV challenges.

We sought to induce primate immunodeficiency virus-specific cellular and neutralizing antibody (nAb) responses in rhesus macaques (RM) through a bimodal vaccine approach. RM were immunized intragastrically (i.g.) with the live-attenuated Listeria monocytogenes (Lm) vector Lmdd-BdopSIVgag encoding SIVmac239 gag. SIV Gag-specific cellular responses were boosted by intranasal and intratracheal administration of replication-competent adenovirus (Ad5hr-SIVgag) encoding the same gag. To broaden antiviral immunity, the RM were immunized with multimeric HIV clade C (HIV-C) gp160 and HIV Tat. SIV Gag-specific cellular immune responses and HIV-1 nAb developed in some RM. The animals were challenged intrarectally with five low doses of R5 SHIV-1157ipEL-p, encoding a heterologous HIV-C Env (22.1% divergent to the Env immunogen). All five controls became viremic. One out of ten vaccinees was completely protected and another had low peak viremia. Sera from the completely and partially protected RM neutralized the challenge virus > 90%; these RM also had strong SIV Gag-specific proliferation of CD8⁺ T cells. Peak and area under the curve of plasma viremia (during acute phase) among vaccinees was lower than for controls, but did not attain significance. The completely protected RM showed persistently low numbers of the α4ß7-expressing CD4⁺ T cells; the latter have been implicated as preferential virus targets in vivo. Thus, vaccine-induced immune responses and relatively lower numbers of potential target cells were associated with protection.

An anti-HIV-1 V3 loop antibody fully protects cross-clade and elicits T-cell immunity in macaques mucosally challenged with an R5 clade C SHIV.

Neutralizing antibodies have been shown to protect macaques against SHIV challenge. However, genetically diverse HIV-1 clades have evolved, and a key question left unanswered is whether neutralizing antibodies can confer cross-clade protection in vivo. The novel human monoclonal antibody HGN194 was isolated from an individual infected with an HIV-1 clade AG recombinant circulating recombinant form (CRF). HGN194 targets an epitope in the third hypervariable loop (V3) of HIV-1 gp120 and neutralizes a range of relatively neutralization-sensitive and resistant viruses. We evaluated the potential of HGN194 to protect infant rhesus monkeys against a SHIV encoding a primary CCR5-tropic HIV-1 clade C envelope. After high-dose mucosal challenge, all untreated controls became highly viremic while all HGN194-treated animals (50 mg/kg) were completely protected. When HGN194 was given at 1 mg/kg, one out of two monkeys remained aviremic, whereas the other had delayed, lower peak viremia. Interestingly, all protected monkeys given high-dose HGN194 developed Gag-specific proliferative responses of both CD4+ and CD8+ T cells. To test whether generation of the latter involved cryptic infection, we ablated CD8+ cells after HGN194 clearance. No viremia was detected in any protected monkeys, thus ruling out virus reservoirs. Thus, induction of CD8 T-cell immunity may have resulted from transient "Hit and Run" infection or cross priming via Ag-Ab-mediated cross-presentation. Together, our data identified the HGN194 epitope as protective and provide proof-of-concept that this anti-V3 loop mAb can prevent infection with sterilizing immunity after challenge with virus of a different clade, implying that V3 is a potential vaccine target.

Development of a tier 1 R5 clade C simian-human immunodeficiency virus as a tool to test neutralizing antibody-based immunoprophylaxis.

BACKGROUND: While some recently transmitted HIV clade C (HIV-C) strains exhibited tier 1 neutralization phenotypes, most were tier 2 strains (J Virol 2010; 84:1439). Because induction of neutralizing antibodies (nAbs) through vaccination against tier 2 viruses has proven difficult, we have generated a tier 1, clade C simian-human immunodeficiency virus (SHIV-C) to permit efficacy testing of candidate AIDS vaccines against tier 1 viruses. METHODS: SHIV-1157ipEL was created by swapping env of a late-stage virus with that of a tier 1, early form. RESULTS: After adaptation to rhesus macaques (RM), passaged SHIV-1157ipEL-p replicated vigorously in vitro and in vivo while maintaining R5 tropism. The virus was reproducibly transmissible intrarectally. Phylogenetically, SHIV-1157ipEL-p Env clustered with HIV-C sequences. All RM chronically infected with SHIV-1157ipEL-p developed high nAb titers against autologous as well as heterologous tier 1 strains. CONCLUSIONS: SHIV-1157ipEL-p was reproducibly transmitted in RM, induced cross-clade nAbs, and represents a tool to evaluate anti-HIV-C nAb responses in primates.

A live attenuated Listeria monocytogenes vaccine vector expressing SIV Gag is safe and immunogenic in macaques and can be administered repeatedly.

Listeria monocytogenes (Lm) is known to induce strong cellular immune responses. We constructed a live-attenuated Lm vector, Lmdd-BdopSIVgag, which encodes SIVmac239 gag. Intragastric (i.g.) administration of 3 × 10(12) bacteria to rhesus macaques was safe and induced anti-Gag cellular but no humoral immune responses. Boosting of Gag-specific cellular responses was observed after i.g. administration of Lmdd-BdopSIVgag to previously vaccinated RM despite preexisting anti-Lm immunity shown by lymphoproliferative responses. Surprisingly, anti-Lm cellular responses were also detected in non-vaccinated controls, which may reflect the fact that Lm is a ubiquitous bacterium. The novel, live-attenuated Lmdd-BdopSIVgag may be an attractive platform for oral vaccine delivery.

R5 clade C SHIV strains with tier 1 or 2 neutralization sensitivity: tools to dissect env evolution and to develop AIDS vaccines in primate models.

BACKGROUND: HIV-1 clade C (HIV-C) predominates worldwide, and anti-HIV-C vaccines are urgently needed. Neutralizing antibody (nAb) responses are considered important but have proved difficult to elicit. Although some current immunogens elicit antibodies that neutralize highly neutralization-sensitive (tier 1) HIV strains, most circulating HIVs exhibiting a less sensitive (tier 2) phenotype are not neutralized. Thus, both tier 1 and 2 viruses are needed for vaccine discovery in nonhuman primate models. METHODOLOGY/PRINCIPAL FINDINGS: We constructed a tier 1 simian-human immunodeficiency virus, SHIV-1157ipEL, by inserting an "early," recently transmitted HIV-C env into the SHIV-1157ipd3N4 backbone [1] encoding a "late" form of the same env, which had evolved in a SHIV-infected rhesus monkey (RM) with AIDS. SHIV-1157ipEL was rapidly passaged to yield SHIV-1157ipEL-p, which remained exclusively R5-tropic and had a tier 1 phenotype, in contrast to "late" SHIV-1157ipd3N4 (tier 2). After 5 weekly low-dose intrarectal exposures, SHIV-1157ipEL-p systemically infected 16 out of 17 RM with high peak viral RNA loads and depleted gut CD4+ T cells. SHIV-1157ipEL-p and SHIV-1157ipd3N4 env genes diverge mostly in V1/V2. Molecular modeling revealed a possible mechanism for the increased neutralization resistance of SHIV-1157ipd3N4 Env: V2 loops hindering access to the CD4 binding site, shown experimentally with nAb b12. Similar mutations have been linked to decreased neutralization sensitivity in HIV-C strains isolated from humans over time, indicating parallel HIV-C Env evolution in humans and RM. CONCLUSIONS/SIGNIFICANCE: SHIV-1157ipEL-p, the first tier 1 R5 clade C SHIV, and SHIV-1157ipd3N4, its tier 2 counterpart, represent biologically relevant tools for anti-HIV-C vaccine development in primates.

Neuropathogenic SIVsmmFGb genetic diversity and selection-induced tissue-specific compartmentalization during chronic infection and temporal evolution of viral genes in lymphoid tissues and regions of the central nervous system.

SIVsmmFGb is a lentivirus swarm that induces neuropathology in over 90% of infected pigtailed macaques and reliably models central nervous system HIV infection in people. We have previously studied SIVsmmFGb genetic diversity and compartmentalization during acute infection, but little is understood about diversity and intertissue compartmentalization during chronic infection. Tissue-specific pressure appeared to affect the diversity of Nef sequences between tissues, but changes to the Env V1 region and Int diversity were similar across all tissues. At 2 months postinfection, compartmentalization of the SIVsmmFGb env V1 region, nef, and int was noted between different brain regions and between brain regions and lymph nodes. Convergent evolution of the nef and env V1 region, and divergent evolution of int, was noted between compartments and all genes demonstrated intratissue temporal segregation. For the env V1 region and nef, temporal segregation was stronger in the brain regions than the periphery, but little difference between tissues was noted for int. Positive selection of the env V1 region appeared in most tissues at 2 months postinfection, whereas nef and int faced negative selection in all tissues. Positive selection of the env V1 region sequences increased in some brain regions over time. SIVsmmFGb nef and int sequences each saw increased negative selection in brain regions, and one lymph node, over the course of infection. Functional differences between tissue compartments decreased over time for int and env V1 region sequences, but increased for nef sequences.

AIDS and optic neuritis in a rhesus monkey infected with the R5 clade C SHIV-1157ipd3N4.

A Chinese rhesus macaque infected with the pathogenic CCR5-tropic clade C simian-human immunodeficiency virus, SHIV-1157ipd3N4, had persistent viremia, depletion of CD4(+) T cells to <200 cells/µl, opportunistic infections, coagulopathy, and gradual development of bilateral blindness. MRI revealed marked thickening of both optic nerves. Histopathological evaluation showed diffuse cellular infiltration at necropsy and a focus of SHIV-infected cells. This is the first report of CNS pathology following chronic infection with an obligate R5 SHIV.

Relative transmissibility of an R5 clade C simian-human immunodeficiency virus across different mucosae in macaques parallels the relative risks of sexual HIV-1 transmission in humans via different routes.

BACKGROUND: Worldwide, approximately 90% of all human immunodeficiency virus (HIV) transmissions occur mucosally; almost all involve R5 strains. Risks of sexual HIV acquisition are highest for rectal, then vaginal, and finally oral exposures. METHODS: Mucosal lacerations may affect the rank order of susceptibility to HIV but cannot be assessed in humans. We measured relative virus transmissibility across intact mucosae in macaques using a single stock of SHIV-1157ipd3N4, a simian-human immunodeficiency virus encoding a primary R5 HIV clade C env (SHIV-C). RESULTS: The penetrability of rhesus macaque mucosae differed significantly, with rectal challenge requiring the least virus, followed by vaginal and then oral routes (P = .031, oral vs vaginal; P < .001 rectal vs vaginal). These findings imply that intrinsic mucosal properties are responsible for the differential mucosal permeability. The latter paralleled the rank order reported for humans, with relative risk estimates within the range of epidemiological human studies. To test whether inflammation facilitates virus transmission--as predicted from human studies--we established a macaque model of localized buccal inflammation. Systemic infection occurred across inflamed but not normal buccal mucosa. CONCLUSION: Our primate data recapitulate virus transmission risks observed in humans, thus establishing R5 SHIV-1157ipd3N4 in macaques as a robust model system to study cofactors involved in human mucosal HIV transmission and its prevention.

Complete protection from repeated vaginal simian-human immunodeficiency virus exposures in macaques by a topical gel containing tenofovir alone or with emtricitabine.

New-generation gels that deliver potent antiretroviral drugs against human immunodeficiency virus type 1 have renewed hopes for topical prophylaxis as a prevention strategy. Previous preclinical research with monkey models suggested that high concentrations and drug combinations are needed for high efficacy. We evaluated two long-acting reverse transcriptase inhibitors, tenofovir (TFV) and emtricitabine (FTC), by using a twice-weekly repeat challenge macaque model and showed that a preexposure vaginal application of gel with 1% TFV alone or in combination with 5% FTC fully protected macaques from a total of 20 exposures to simian-human immunodeficiency virus SF162p3. FTC and TFV were detected in plasma 30 min after vaginal application, suggesting rapid absorption. FTC was detected more frequently than TFV and showed higher levels, reflecting the fivefold-higher concentration of this drug than of TFV. Two of 12 repeatedly exposed but protected macaques showed limited T-cell priming, which did not induce resistance to infection when macaques were rechallenged. Thus, single drugs with durable antiviral activity can provide highly effective topical prophylaxis and overcome the need for noncoital use or for drug combinations which are more complex and costly to formulate and approve.

Reduced genetic diversity in lymphoid and central nervous system tissues and selection-induced tissue-specific compartmentalization of neuropathogenic SIVsmmFGb during acute infection.

The simian lentivirus strain SIVsmmFGb is a viral swarm population inducing neuropathology in over 90% of infected pigtailed macaques and serves as a reliable model for HIV neuropathogenesis. However, little is understood about the genetic diversity of this virus, how said diversity influences the initial seeding of the central nervous system and lymph nodes, or whether the virus forms distinct genetic compartments between tissues during acute infection. In this study, we establish that our SIVsmmFGb stock virus contains four genetically distinct envelope V1 region groups, three distinct integrase groups, and two Nef groups. We demonstrate that initial central nervous system and lymph node seeding reduces envelope V1 and integrase genetic diversity but has a variable effect on Nef diversity. SIVsmmFGb envelope V1 region genes from the basal ganglia, cerebellum, and hippocampus form distinct genetic compartments from each other, the midfrontal cortex, and the lymph nodes. Basal ganglia, cerebellum, hippocampus, and midfrontal cortex-derived nef genes all form distinct genetic compartments from each other, as well as from the lymph nodes. We also find basal ganglia, hippocampus, and midfrontal cortex-derived integrase sequences forming distinct compartments from both of the lymph nodes and that the hippocampus and midfrontal cortex form separate compartments from the cerebellum, while the axillary and mesenteric lymph nodes compartmentalize separately from each other. Compartmentalization of the envelope V1 genes resulted from positive selection, and compartmentalization of the nef and integrase genes from negative selection. These results indicate restrictions on virus genetic diversity during initial tissue seeding in neuropathogenic SIV infection.

Probable deceleration of progression of Simian AIDS affected by opiate dependency: studies with a rhesus macaque/SIVsmm9 model.

OBJECTIVES: To determine effects of opiate dependency on development of simian AIDS. DESIGN: Assessments of viral, immune, and clinicopathological status were conducted on rhesus macaques before and after establishment of opiate dependency and Simian Immunodeficiency Virus, sooty mangabey, strain-9 (SIVsmm9) infection. Controls received saline. METHODS: Blood was collected at baseline, before opiate dependencies, and viral infections were established and then after SIVsmm9 infection, longitudinally, through 216 weeks. Plasma viral titers were assessed using the branched chain DNA assay and CD4 and CD8 counts via cytofluorometry. Clinicopathological assessments of AIDS were founded on Centers for Disease Control and Prevention and other selected criteria. RESULTS: AIDS progression rates seemed to be decelerated and survival times increased by opiate dependency. Mean viral titers were unaffected by opiate exposure. Opiate-dependent monkeys that evidenced high initial viral titers survived significantly longer than controls. Several opiate-dependent monkeys maintained high viral titers for atypically extended durations. Several (5/19) opiate-dependent monkeys died or were removed early from the study due to "non-AIDS" causes. CONCLUSIONS: Long-term opiate dependency seemed to decelerate the rate of progression to AIDS in the SIVsmm9 monkey model. This effect was most evident in monkeys with high initial viral titers/set points. "Non-AIDS" morbidities and mortalities were noted as potential confounds of epidemiological assessments of the role of opiates in HIV/AIDS.