Simian Immunodeficiency Virus Strains Research Articles

Replicative fitness and pathogenicity of primate lentiviruses in lymphoid tissue, primary human and chimpanzee cells: relation to possible jumps to humans

Simian immunodeficiency viruses (SIV) have been jumping between non-human primates in West/Central Africa for thousands of years and yet, the HIV-1 epidemic only originated from a primate lentivirus over 100 years ago. This study examined the replicative fitness, transmission, restriction, and cytopathogenicity of 22 primate lentiviruses in primary human lymphoid tissue and both primary human and chimpanzee peripheral blood mononuclear cells. Pairwise competitions revealed that SIV from chimpanzees (cpz) had the highest replicative fitness in human or chimpanzee peripheral blood mononuclear cells, even higher fitness than HIV-1 group M strains responsible for worldwide epidemic. The SIV strains belonging to the "HIV-2 lineage" (including SIVsmm, SIVmac, SIVagm) had the lowest replicative fitness. SIVcpz strains were less inhibited by human restriction factors than the "HIV-2 lineage" strains. SIVcpz efficiently replicated in human tonsillar tissue but did not deplete CD4+ T-cells, consistent with the slow or nonpathogenic disease observed in most chimpanzees. In contrast, HIV-1 isolates and SIV of the HIV-2 lineage were pathogenic to the human tonsillar tissue, almost independent of the level of virus replication. Of all primate lentiviruses, SIV from chimpanzees appears most capable of infecting and replicating in humans, establishing HIV-1. SIV from other Old World monkeys, e.g. the progenitor of HIV-2, replicate slowly in humans due in part to restriction factors. Nonetheless, many of these SIV strains were more pathogenic than SIVcpz. Either SIVcpz evolved into a more pathogenic virus while in humans or a rare SIVcpz, possibly extinct in chimpanzees, was pathogenic immediately following the jump into human. Support for this study to E.J.A. was provided by the NIH/NIAID R01 AI49170 and CIHR project grant 385787. Infrastructure support was provided by the NIH CFAR AI36219 and Canadian CFI/Ontario ORF 36287. Efforts of J.A.B. and N.J.H. was provided by NIH AI099473 and for D.H.C., by VA and NIH AI AI080313.

Plasma galectin-9 levels correlate with blood monocyte turnover and predict simian/human immunodeficiency virus disease progression

Abstract Background Late-stage human immunodeficiency virus (HIV) infection is typically characterized by low CD4 + T-cell count. We previously showed that profound changes in the monocyte turnover (MTO) rate in rhesus macaques infected by the simian immunodeficiency virus (SIV) outperforms declining CD4 + T-cell counts in predicting rapid health decline associated with progression to terminal disease. High MTO is associated with increased tissue macrophage death. However, MTO analysis is complex and not directly applicable to humans. Methods We explored blood-available biomarkers associated with MTO using comprehensive immune cell profiling via flow cytometry, blood cell count and chemistry, and ELISA. Results Plasma galectin-9 was identified as the most highly correlated marker with MTO. This correlation remained statistically significant during acute, chronic, and late-stage infections caused by three different SIV strains tested. In addition, the galectin-9 level also predicted decline in animal health, requiring medical cull. The correlation between MTO and galectin-9 was maintained even in uninfected animals showing variable MTO. Conclusions These findings support the exploration of galectin-9 as a surrogate biomarker of MTO for non-invasive monitoring of disease progression (e.g. HIV) that may also be applicable in humans and as a potential indicator of tissue macrophages apoptosis.

Increased neutralization potency and breadth elicited by a SARS-CoV-2 mRNA vaccine forming virus-like particles

Vaccines have played a fundamental role in the control of infectious diseases. We previously developed a messenger RNA (mRNA) vaccine against HIV-1 that forms virus-like particles (VLPs) through coexpression of the viral envelope with Gag. Here, we applied the same principle to the design of a VLP-forming mRNA vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). To promote cognate interaction with simian immunodeficiency virus (SIV) Gag, we engineered different chimeric proteins encompassing the ectodomain and the transmembrane region of the SARS-CoV-2 Spike protein from the Wuhan-Hu-1 strain fused to the gp41 cytoplasmic tail of either HIV-1 (strain WITO) or SIV (strain mac239) with or without a partial truncation at amino acid 745 to enhance membrane expression. Upon cotransfection with SIV gag mRNA, the Spike-SIVCT.745 (SSt) chimera yielded the highest level of cell-surface expression and extracellular VLP release. Immunization of BALB/c mice with SSt+gag mRNA at 0, 4, and 16 wk induced higher titers of Spike-binding and autologous neutralizing antibodies at all time points compared to SSt mRNA alone. Furthermore, mice immunized with SSt+gag mRNA developed neutralizing antibodies effective against different variants of concern. These data demonstrate that the Gag/VLP mRNA platform can be successfully applied to vaccines against different agents for the prevention of infectious diseases of global relevance.

FRugally Optimized DNA Octomer (FRODO) qPCR Measurement of HIV and SIV in Human and Nonhuman Primate Samples.

Quantitative polymerase chain reactions (qPCRs) are commonly employed to enumerate genes of interest among particular biological samples. Insertion of PCR amplicons into plasmid DNA is a mainstay for creation of known quantities of target sequences to standardize qPCRs. Typically, one amplicon is inserted into one plasmid construct, and the plasmid is then amplified, purified, serially diluted, and quantified to be used to enumerate target sequences in unknown samples. As qPCR is often used to detect multiple amplicons simultaneously, individual qPCR standards are often desired to normalize one to another. Here we report a single plasmid containing eight amplicons, which can be used to quantify several different strains of simian immunodeficiency virus and human immunodeficiency virus, cell number equivalents for humans and nonhuman primates, T cell receptor excision circles, and bacterial 16S DNA. This FRugally Optimized DNA Octomer (FRODO) plasmid was created and standardized to quantify all eight PCR amplicons. © 2021 US Government. Basic Protocol 1: Total genomic DNA extraction from primary cells Basic Protocol 2: Quantitative PCR for viral, bacterial, and cell number equivalents Support Protocol: Purification, quantification, and storage of FRODO standard plasmid DNA.

Close-up: HIV/SIV intasome structures shed new light on integrase inhibitor binding and viral escape mechanisms.

Integrase strand transfer inhibitors (INSTIs) are important components of drug formulations that are used to treat people living with HIV, and second-generation INSTIs dolutegravir and bictegravir impart high barriers to the development of drug resistance. Reported 10years ago, X-ray crystal structures of prototype foamy virus (PFV) intasome complexes explained how INSTIs bind integrase to inhibit strand transfer activity and provided initial glimpses into mechanisms of drug resistance. However, comparatively low sequence identity between PFV and HIV-1 integrases limited the depth of information that could be gleaned from the surrogate model system. Recent high-resolution structures of HIV-1 intasomes as well as intasomes from a closely related strain of simian immunodeficiency virus (SIV), which were determined using single-particle cryogenic electron microscopy, have overcome this limitation. The new structures reveal the binding modes of several advanced INSTI compounds to the HIV/SIV integrase active site and critically inform the structural basis of drug resistance. These findings will help guide the continued development of this important class of antiretroviral therapeutics.

Protection against SIV in Rhesus Macaques Using Albumin and CD4-Based Vector-Mediated Gene Transfer

Antibody-like molecules were evaluated with potent simian immunodeficiency virus (SIV) neutralizing properties (immunoadhesins) that were delivered by a recombinant adeno-associated virus (rAAV) vector in the SIV-infected rhesus macaque model. When injected intramuscularly into the host, the vector directs in vivo production of the transgenes with antibody-like binding properties that lead to serum neutralizing activity against SIV. To extend the half-life of the immunoadhesins, rhesus cluster of differentiation 4 (CD4) and a single-chain antibody (4L6) were fused with albumin molecules, and these constructs were tested in our model of SIV infection. Antibody-based immunoadhesins provided high serum neutralizing titers against the original SIV strain. CD4-based immunoadhesins provided a wider spectrum of neutralization against different SIV strains in comparison to antibody-based therapeutics and had the potential to protect against high viral challenging doses. Although the albumin-antibody fusion immunoadhesin provided strong and prolonged protection of the immunized animals against SIV challenge, the albumin-CD4 fusion altered the specificity and decreased the overall protection effectiveness of the immunoadhesin in comparison to the antibody-based molecules. Albumin-based immunoadhesins increase in vivo longevity of the immune protection; however, they present challenges likely linked to the induction of anti-immunoadhesin antibodies.

Viral protein X reduces the incorporation of mutagenic noncanonical rNTPs during lentivirus reverse transcription in macrophages

Unlike activated CD4+ T cells, nondividing macrophages have an extremely small dNTP pool, which restricts HIV-1 reverse transcription. However, rNTPs are equally abundant in both of these cell types and reach much higher concentrations than dNTPs. The greater difference in concentration between dNTPs and rNTPs in macrophages results in frequent misincorporation of noncanonical rNTPs during HIV-1 reverse transcription. Here, we tested whether the highly abundant SAM domain– and HD domain–containing protein 1 (SAMHD1) deoxynucleoside triphosphorylase in macrophages is responsible for frequent rNTP incorporation during HIV-1 reverse transcription. We also assessed whether Vpx (viral protein X), an accessory protein of HIV-2 and some simian immunodeficiency virus strains that targets SAMHD1 for proteolytic degradation, can counteract the rNTP incorporation. Results from biochemical simulation of HIV-1 reverse transcriptase–mediated DNA synthesis confirmed that rNTP incorporation is reduced under Vpx-mediated dNTP elevation. Using HIV-1 vector, we further demonstrated that dNTP pool elevation by Vpx or deoxynucleosides in human primary monocyte-derived macrophages reduces noncanonical rNTP incorporation during HIV-1 reverse transcription, an outcome similarly observed with the infectious HIV-1 89.6 strain. Furthermore, the simian immunodeficiency virus mac239 strain, encoding Vpx, displayed a much lower level of rNTP incorporation than its ΔVpx mutant in macrophages. Finally, the amount of rNMPs incorporated in HIV-1 proviral DNAs remained unchanged for ∼2 weeks in macrophages. These findings suggest that noncanonical rNTP incorporation is regulated by SAMHD1 in macrophages, whereas rNMPs incorporated in HIV-1 proviral DNA remain unrepaired. This suggests a potential long-term DNA damage impact of SAMHD1-mediated rNTP incorporation in macrophages.

Blocking α4β7 integrin binding to SIV does not improve virologic control.

A study in nonhuman primates reported that infusions of an antibody against α4β7 integrin, in combination with antiretroviral therapy, showed consistent, durable control of simian immunodeficiency virus (SIV) in rhesus macaques. The antibody used has pleiotropic effects, so we set out to gain insight into the underlying mechanism by comparing this treatment to treatment with non-neutralizing monoclonal antibodies against the SIV envelope glycoprotein that only block α4β7 binding to SIV Env but have no other host-directed effects. Similar to the initial study, we used an attenuated strain of SIV containing a stop codon in nef. The study used 30 macaques that all began antiretroviral therapy and then were divided into five groups to receive different antibody treatments. Unlike the published report, we found no sustained virologic control by these treatments in vivo.

Engineering of a Lectibody Targeting High-Mannose-Type Glycans of the HIV Envelope.

High-mannose-type glycans (HMGs) are aberrantly enriched on HIV envelope glycoproteins. However, there is currently no drug selectively targeting HIV-associated HMGs. Here, we describe a novel HMG-targeting “lectibody,” a recombinant Fc-fusion protein comprising human IgG1 Fc and a novel actinohivin lectin variant (Avaren) obtained by structure-guided modifications for improved overall surface charge properties (AvFc). AvFc was engineered and produced using a rapid and scalable plant-based transient overexpression system. The lectibody exhibited potent antiviral activity against HIV-1 groups M and O primary viruses, as well as HIV-2 and simian immunodeficiency virus (SIV) strains, without affecting normal human blood cells. Furthermore, the lectibody induced Fc-mediated cell killing activity against HIV-1-infected cells and selectively recognized SIVmac239-infected macaque mesenteric lymph node cells in vitro. AvFc showed an extended serum half-life in rats and rhesus macaques, while no discernible toxicity was observed upon repeated systemic dosing in mice. These results highlight AvFc’s potential as a biotherapeutic targeting HIV-associated HMGs of cell-free virions, as well as productively infected cells, providing a foundation for new anti-HIV strategies. Efficient and cost-effective bioproduction in greenhouse facilities may open unique possibilities for further development of AvFc.

Analysis and Prospects of Using Recombinant Vaccinia Virus MVA Strain as a Vector in the Development of the Vaccines against Human and Simian Immunodeficiency Virus Diseases

The review presents the results of preclinical use of vector vaccines against human immunodeficiency virus (HIV) disease and simian immunodeficiency virus (SIV) disease. Application of antiretroviral therapy exclusively is insufficient for elimination of HIV from patient’s body. This dictates the need for an effective vaccine which will reduce the number of new cases of the disease and reduce the risk of virus transmission. Current practice of medicinal product development showed the effectiveness of heterologous prime-boost regimens for the induction of expressed immune response in laboratory animals. Various vector constructs were used as priming vaccines: DNA vaccines, Bacille Calmette-Guerin vaccine, chimpanzee adenovirus, vesicular stomatitis virus, alphavirus repli-clone. Booster vaccine was represented by recombinant MVA strain. In all vector vaccines, different genes of immunodominant antigens of HIV and SIV agents were inserted. On rhesus macaques, murine, rabbit models, it was demonstrated that deployed vaccination schemes were safe and induced immune response. Because membrane HIV protein is highly variable, strongly glycoziled and subjected to structural changes during receptor binding, it cannot be viewed as a target for induction of virus neutralized antibodies. Therefore, we mainly studied the cell immune response that was presented by poly-functional CD8+ T-cells. However, some recent researches are aimed at such modification of envelope HIV immunogene that would provide for virus neutralizing antibody induction. The study of protective efficiency of the induced immunity in rhesus macaques, immunized with recombinant vectors expressing SIV’ s immunodominant antigens, in case of subsequent inoculation with virulent SIV strain has revealed that all monkeys developed illness. Assuming that the constructions with SIV’ s immunodominant antigens under protective efficiency testing on rhesus macaques imitate AIDS in humans, it seems that vaccines, developed up-to-date, will not be effective for collective immunity formation against AIDS. Therefore, the search for novel combinations of expressed immunodominant antigens for the inclusion into the composition of priming and booster vaccines remains a priority area at present time.

Neuroinflammatory Changes in Relation to Cerebrospinal Fluid Viral Load in Simian Immunodeficiency Virus Encephalitis.

The exact cause of neurocognitive dysfunction in HIV-positive patients despite successful control of the infection in the periphery is not completely understood. One suggested mechanism is a vicious cycle of microglial activation and release of proinflammatory chemokines/cytokines that eventually leads to neuronal loss and dysfunction. However, the exact role of microglial activation in the earliest stages of the infection with high cerebrospinal fluid (CSF) viral loads (VL) is unclear. In this study, we imaged the translocator protein (TSPO), a mitochondrial membrane receptor known to be upregulated in activated microglia and macrophages, in rhesus macaques before and multiple times after inoculation with a neurotropic simian immunodeficiency virus (SIV) strain (SIVsm804E), using 18F-DPA714 positron emission tomography (PET). The whole-brain standardized uptake values of TSPO at equilibrium reflecting total binding (SUVT) and binding potentials (BPND) were calculated and correlated with CSF and serum markers of disease, and a corresponding postmortem immunostaining analysis was also performed. SUVT was found to be inversely correlated with both CSF VL and monocyte chemoattractant protein 1 (MCP-1) levels. In SIV-infected macaques with very high CSF VL at necropsy (>106 copies/ml), we found decreased TSPO binding by PET, and this was supported by immunostaining which showed glial and neuronal apoptosis rather than microglial activation. On the other hand, with only moderately elevated CSF VL (∼104 copies/ml), we found increased TSPO binding as well as focal and diffuse microglial activation on immunostaining. Our results in the SIV-infected macaque model provide insights into the relationship between HIV neuropathology and CSF VL at various stages of the disease.IMPORTANCE Neurological and cognitive problems are a common complication of HIV infection and are prevalent even in treated individuals. Although the molecular processes underlying brain involvement with HIV are not completely understood, inflammation is suspected to play a significant role. Our work presents an in vivo assessment of neuroinflammation in an animal model of HIV, the simian immunodeficiency virus (SIV)-infected rhesus macaque. Using positron emission tomography (PET) imaging, we identified changes in brain inflammation after inoculation with SIV over time. Interestingly, we found decreased binding of the PET ligand in the presence of very high cerebrospinal fluid (CSF) viral loads. These findings were supported by immunostaining which showed marked glial loss instead of inflammation. This study provides insight into glial and neuronal changes associated with very high CSF viral load and could reflect similar changes occurring in HIV-infected patients.

Lack of susceptibility in neonatally infected rhesus macaques to simian immunodeficiency virus-induced encephalitis.

Despite combination antiretroviral therapies making HIV a chronic rather than terminal condition for many people, the prevalence of HIV-associated neurocognitive disorders (HAND) is increasing. This is especially problematic for children living with HIV. Children diagnosed HAND rarely display the hallmark pathology of HIV encephalitis in adults, namely infected macrophages and multinucleated giant cells in the brain. This finding has also been documented in rhesus macaques infected perinatally with simian immunodeficiency virus (SIV). However, the extent and mechanisms of lack of susceptibility to encephalitis in perinatally HIV-infected children remain unclear. In the current study, we compared brains of macaques infected with pathogenic strains of SIV at different ages to determine neuropathology, correlates of neuroinflammation, and potential underlying mechanisms. Encephalitis was not found in the macaques infected within 24h of birth despite similar high plasma viral load and high monocyte turnover. Macaques developed encephalitis only when they were infected after 4months of age. Lower numbers of CCR5-positive cells in the brain, combined with a less leaky blood-brain barrier, may be responsible for the decreased virus infection in the brain and consequently the absence of encephalitis in newborn macaques infected with SIV.

HIV-1 and SIV Infection Are Associated with Early Loss of Lung Interstitial CD4+ T Cells and Dissemination of Pulmonary Tuberculosis

SUMMARYLung interstitial CD4+ T cells are critical for protection against pulmonary infections, but the fate of this population during HIV-1 infection is not well described. We studied CD4+ T cells in the setting of HIV-1 infection in human lung tissue, humanized mice, and a Mycobacterium tuberculosis (Mtb)/simian immunodeficiency virus (SIV) nonhuman primate co-infection model. Infection with a CCR5-tropic strain of HIV-1 or SIV results in severe and rapid loss of lung interstitial CD4+ T cells but not blood or lung alveolar CD4+ T cells. This is accompanied by high HIV-1 production in these cells in vitro and in vivo. Importantly, during early SIV infection, loss of lung interstitial CD4+ T cells is associated with increased dissemination of pulmonary Mtb infection. We show that lung interstitial CD4+ T cells serve as an efficient target for HIV-1 and SIV infection that leads to their early depletion and an increased risk of disseminated tuberculosis.

Polymorphisms in Rhesus Macaque Tetherin Are Associated with Differences in Acute Viremia in Simian Immunodeficiency Virus Δnef-Infected Animals.

Tetherin (BST-2 or CD317) is an interferon-inducible transmembrane protein that inhibits virus release from infected cells. To determine the extent of sequence variation and the impact of polymorphisms in rhesus macaque tetherin on simian immunodeficiency virus (SIV) infection, tetherin alleles were sequenced from 146 rhesus macaques, including 68 animals infected with wild-type SIVmac239 and 47 animals infected with SIVmac239Δnef Since Nef is the viral gene product of SIV that counteracts restriction by tetherin, these groups afford a comparison of the effects of tetherin polymorphisms on SIV strains that are, and are not, resistant to tetherin. We identified 15 alleles of rhesus macaque tetherin with dimorphic residues at 9 positions. The relationship between these alleles and plasma viral loads was compared during acute infection, prior to the onset of adaptive immunity. Acute viremia did not differ significantly among the wild-type SIV-infected animals; however, differences in acute viral loads were associated with polymorphisms in tetherin among the animals infected with SIVΔnef In particular, polymorphisms at positions 43 and 111 (P43 and H111) were associated with lower acute-phase viral loads for SIVΔnef infection. These observations reveal extensive polymorphism in rhesus macaque tetherin, maintained perhaps as a consequence of variability in the selective pressure of diverse viral pathogens, and identify tetherin alleles that may have an inherently greater capacity to restrict SIV replication in the absence of Nef.IMPORTANCE As a consequence of ongoing evolutionary conflict with viral pathogens, tetherin has accumulated numerous species-specific differences that represent important barriers to the transmission of viruses between species. This study reveals extensive polymorphism in rhesus macaque tetherin and identifies specific alleles that are associated with lower viral loads during the first few weeks after infection with nef-deleted SIV. These observations suggest that the variable selective pressure of viral pathogens, in addition to driving the diversification of tetherin among species, also operates within certain species to maintain sequence variation in tetherin.

A recombinant herpesviral vector containing a near-full-length SIVmac239 genome produces SIV particles and elicits immune responses to all nine SIV gene products.

The properties of the human immunodeficiency virus (HIV) pose serious difficulties for the development of an effective prophylactic vaccine. Here we describe the construction and characterization of recombinant (r), replication-competent forms of rhesus monkey rhadinovirus (RRV), a gamma-2 herpesvirus, containing a near-full-length (nfl) genome of the simian immunodeficiency virus (SIV). A 306-nucleotide deletion in the pol gene rendered this nfl genome replication-incompetent as a consequence of deletion of the active site of the essential reverse transcriptase enzyme. Three variations were constructed to drive expression of the SIV proteins: one with SIV’s own promoter region, one with a cytomegalovirus (cmv) immediate-early promoter/enhancer region, and one with an RRV dual promoter (p26 plus PAN). Following infection of rhesus fibroblasts in culture with these rRRV vectors, synthesis of the early protein Nef and the late structural proteins Gag and Env could be demonstrated. Expression levels of the SIV proteins were highest with the rRRV-SIVcmv-nfl construct. Electron microscopic examination of rhesus fibroblasts infected with rRRV-SIVcmv-nfl revealed numerous budding and mature SIV particles and these infected cells released impressive levels of p27 Gag protein (>150 ng/ml) into the cell-free supernatant. The released SIV particles were shown to be incompetent for replication. Monkeys inoculated with rRRV-SIVcmv-nfl became persistently infected, made readily-detectable antibodies against SIV, and developed T-cell responses against all nine SIV gene products. Thus, rRRV expressing a near-full-length SIV genome mimics live-attenuated strains of SIV in several important respects: the infection is persistent; >95% of the SIV proteome is naturally expressed; SIV particles are formed; and CD8+ T-cell responses are maintained indefinitely in an effector-differentiated state. Although the magnitude of anti-SIV immune responses in monkeys infected with rRRV-SIVcmv-nfl falls short of what is seen with live-attenuated SIV infection, further experimentation seems warranted.

Vaccine-Associated Maintenance of Epithelial Integrity Correlated With Protection Against Virus Entry.

To identify the mechanisms by which human immunodeficiency virus type 1 (HIV-1) might penetrate the epithelial barrier during sexual transmission to women and the mechanisms of vaccine-associated protection against entry, we characterized early epithelial responses to vaginal inoculation of simian immunodeficiency virus strain mac251 (SIVmac251) in naive or SIVmac239Δnef-vaccinated rhesus macaques. Vaginal inoculation induced an early stress response in the cervicovaginal epithelium, which was associated with impaired epithelial integrity, damaged barrier function, and virus and bacterial translocation. In vaccinated animals, early stress responses were suppressed, and the maintenance of epithelial barrier integrity correlated with prevention of virus entry. These vaccine-protective effects were associated with a previously described mucosal system for locally producing and concentrating trimeric gp41 antibodies at the mucosal interface and with formation of SIV-specific immune complexes that block the stress responses via binding to the epithelial receptor FCGR2B and subsequent inhibitory signaling. Thus, blocking virus entry may be one protective mechanism by which locally concentrated non-neutralizing Ab might prevent HIV sexual transmission to women.

A SIV molecular clone that targets the CNS and induces neuroAIDS in rhesus macaques.

Despite effective control of plasma viremia with the use of combination antiretroviral therapies (cART), minor cognitive and motor disorders (MCMD) persist as a significant clinical problem in HIV-infected patients. Non-human primate models are therefore required to study mechanisms of disease progression in the central nervous system (CNS). We isolated a strain of simian immunodeficiency virus (SIV), SIVsm804E, which induces neuroAIDS in a high proportion of rhesus macaques and identified enhanced antagonism of the host innate factor BST-2 as an important factor in the macrophage tropism and initial neuro-invasion of this isolate. In the present study, we further developed this model by deriving a molecular clone SIVsm804E-CL757 (CL757). This clone induced neurological disorders in high frequencies but without rapid disease progression and thus is more reflective of the tempo of neuroAIDS in HIV-infection. NeuroAIDS was also induced in macaques co-inoculated with CL757 and the parental AIDS-inducing, but non-neurovirulent SIVsmE543-3 (E543-3). Molecular analysis of macaques infected with CL757 revealed compartmentalization of virus populations between the CNS and the periphery. CL757 exclusively targeted the CNS whereas E543-3 was restricted to the periphery consistent with a role for viral determinants in the mechanisms of neuroinvasion. CL757 would be a useful model to investigate disease progression in the CNS and as a model to study virus reservoirs in the CNS.

Isolation of a simian immunodeficiency virus from a malbrouck (Chlorocebus cynosuros)

To investigate the diversity of simian immunodeficiency virus (SIV) among nonhuman primates (NHPs) in Zambia, next-generation sequencing was performed to determine the complete genome sequence of a novel SIV recovered by co-culturing African green monkey (AGM) peripheral blood lymphocytes with human CD4+ T-cell lines. We report the first described SIV (SIVagmMAL-ZMB) from a malbrouck (Chlorocebus cynosuros). SIVagmMAL-ZMB was detected by real-time PCR analysis of splenic RNA in 3.2% (3/94) of AGMs and was undetectable in baboons (0/105). SIVagmMAL-ZMB possessed <80% nucleotide sequence identity to known SIV isolates and was located basally to vervet monkey SIV strains in all phylogenies.

TRIM5α Resistance Escape Mutations in the Capsid Are Transferable between Simian Immunodeficiency Virus Strains

Many strains of SIV from sooty mangabey monkeys are susceptible to resistance by common rhesus macaque TRIM5α alleles and result in reduced virus acquisition and replication in macaques that express these restrictive alleles. We previously observed that spontaneous variations in the capsid gene were associated with improved replication in macaques, and the introduction of two amino acid changes in the capsid transfers this improved replication to the parent clone. In the present study, we introduced these mutations into a related but distinct strain of SIV that is commonly used for challenge studies for vaccine trials. These mutations also improved the replication of this strain in macaques with the restrictive TRIM5α genotype and thus will eliminate the confounding effects of TRIM5α in vaccine studies.

Attenuated SIV causes persisting neuroinflammation in the absence of a chronic viral load and neurotoxic antiretroviral therapy.

Objectives:Using simian models, where SIV chronic viral loads are naturally controlled in the absence of potentially neurotoxic therapies, we investigated the neuropathological events occurring during times of suppressed viraemia and when these events were initiated.Design:Cynomolgus macaques were infected with SIV strains that are naturally controlled to low levels of chronic viraemia. Study 1: animals were maintained up to 300 days after inoculation and analysed for viral-induced neuropathology following sustained suppression of chronic viral loads. Study 2: initiation and development of lesion was examined following 3, 10, 21, or 125 days SIVmacC8 infection.Methods:Formalin-fixed, paraffin-embedded brain sections were analysed following immunohistochemical staining for simian immunodeficiency virus (SIV) (KK41), blood–brain barrier leakage (ZO-1, fibrinogen), apoptosis (active caspase 3), neuroinflammation [GFAP, cyclooxygenase (COX)-1, COX-2], microglia and macrophage (Iba-1, CD68, and CD16), oligodendrocytes (CNPase1), MHC class II expression, and T cells (CD3 and CD8). Replicating SIV was detected through in-situ hybridization.Results:Study 1: neuroinflammation was present despite prolonged suppressed viraemia. Study 2: attenuated SIV entered the brain rapidly triggering acute phase neuroinflammatory responses. These did not return to naive levels and GFAP and COX-2 responses continued to develop during a chronic phase with a suppressed viral load.Conclusion:Neuroinflammatory responses similar to those in HIV neurocognitively impaired patients are present within macaque brains during prolonged periods of suppressed SIV viral load and in the absence of potentially neurotoxic antiretroviral drugs. These responses, initiated during acute infection, do not resolve despite the lack of on-going peripheral viraemia to potentially reseed the brain.