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Antiretroviral therapy inhibits HIV-1 replication but is not curative due to establishment of a persistent reservoir after virus integration into the host genome. Reservoir reduction is therefore an important HIV-1 cure strategy. Some HIV-1 nonnucleoside reverse transcriptase inhibitors induce HIV-1 selective cytotoxicity in vitro but require concentrations far exceeding approved dosages. Focusing on this secondary activity, we found bifunctional compounds with HIV-1–infected cell kill potency at clinically achievable concentrations. These targeted activator of cell kill (TACK) molecules bind the reverse transcriptase–p66 domain of monomeric Gag-Pol and act as allosteric modulators to accelerate dimerization, resulting in HIV-1 + cell death through premature intracellular viral protease activation. TACK molecules retain potent antiviral activity and selectively eliminate infected CD4 + T cells isolated from people living with HIV-1, supporting an immune-independent clearance strategy.

Simian immunodeficiency virus SIVsab infection is completely controlled in rhesus macaques (RMs) through functional immune responses. We report that in SIVsab-infected RMs, (i) viral replication is controlled to + cell depletion is replication competent and genetically similar to the original virus stock, suggesting early reservoir seeding. This model permits assessment of strategies aimed at depleting the reservoir without multidrug antiretroviral therapy.

HIV infection is associated with increased risk of cardiovascular complications, the underlying mechanism of which remains unclear. Plasma levels of the coagulation biomarker D-dimer (DD) correlate with increased mortality and cardiovascular events in HIV-infected patients. We compared the incidence of cardiovascular lesions and the levels of the coagulation markers DD and thrombin antithrombin in pathogenic SIV infections of rhesus and pigtailed macaques (PTMs) and in nonpathogenic SIV infection of African green monkeys (AGMs) and sooty mangabeys. Hypercoagulability and cardiovascular pathology were only observed in pathogenic SIV infections. In PTMs infected with SIV from AGMs (SIVagm), DD levels were highly indicative of AIDS progression and increased mortality and were associated with cardiovascular lesions, pointing to SIVagm-infected PTMs as an ideal animal model for the study of HIV-associated cardiovascular disease. In pathogenic SIV infection, DD increased early after infection, was strongly correlated with markers of immune activation/inflammation and microbial translocation (MT), and was only peripherally associated with viral loads. Endotoxin administration to SIVagm-infected AGMs (which lack chronic SIV-induced MT and immune activation) resulted in significant increases of DD. Our results demonstrate that hypercoagulation and cardiovascular pathology are at least in part a consequence of excessive immune activation and MT in SIV infection.

Severe malarial anemia (SMA) is a leading cause of mortality among children in sub-Saharan Africa. Although the novel cytokine, interleukin (IL)-23, promotes anemia in chronic inflammatory diseases, the role of IL-23 in SMA remains undefined. Since IL-23 and IL-12 share the IL-12p40 subunit and IL-12Rβ1 receptor, and are down-regulated by IL-10, relationships among these cytokines were explored in Kenyan children with varying severities of malarial anemia. Children with malarial anemia had increased circulating IL-23 and IL-10 and decreased IL-12 relative to healthy controls. Enhanced anemia severity and elevated parasitemia were associated with increased IL-10 relative to IL-23 and IL-12. Further exploration of the relationships among the cytokines using an in vitro model in which peripheral blood mononuclear cells were treated with synthetic hemozoin (sHz, malarial pigment) revealed that IL-12p35 and IL-23p19 transcripts had a sustained induction over 72 h, while IL-12p40 and IL-10 message peaked at 24 h, and rapidly declined thereafter. Taken together, results here show that IL-23 is elevated in children with malarial anemia, and that IL-10 and IL-12 appear to have important regulatory effects on IL-23 production during childhood malaria.

Malaria causes 300-500 million clinical cases and 1-3 million deaths per year, the majority of which occur in African children less than five years of age. The failure of vector control methods to achieve adequate reductions in morbidity and mortality and the widespread resistance to conventional antimalarial drugs have made development of an effective malaria vaccine a global priority. An ideal malaria vaccine should recapitulate naturally acquired immunity in an endemic setting. However, progress toward an efficacious vaccine has been slow, due to the high polymorphism of prospective target antigens and the inability of most vaccines to elicit long-lived immunological memory in the host. This review discusses the efficacy of current pre-erythrocytic-stage, asexual blood-stage, and transmission-blocking vaccine candidates, as well as future prospects for malaria vaccine development.

Mucosal damage to the gastrointestinal (GI) tract with resulting microbial translocation is hypothesized to significantly contribute to the heightened and persistent chronic inflammation and immune activation characteristic to HIV infection. Here we employ a non-human primate model of chemically induced colitis in SIV-uninfected rhesus macaques that we developed using dextran sulfate sodium (DSS), to directly test this hypothesis. DSS treatment results in GI barrier damage with associated microbial translocation, inflammation and immune activation. The progression and severity of colitis are longitudinally monitored by a magnetic resonance imaging approach. DSS treatment of SIV-infected African green monkeys, a natural host species for SIV that does not manifest GI tract damage or chronic immune activation during infection, results in colitis with elevated levels of plasma SIV RNA, sCD14, LPS, CRP and mucosal CD4+ T-cell loss. Together these results support the hypothesis that GI tract damage leading to local and systemic microbial translocation, and associated immune activation, are important determinants of AIDS pathogenesis., HIV-1 infection in humans and SIV infection in rhesus macaques are associated with mucosal damage to the gastrointestinal tract, microbial translocation and chronic immune activation. Here the authors develop a non-human primate DSS colitis model that recapitulates these aspects of the disease in uninfected rhesus macaques.

Damage to the intestinal mucosa results in the translocation of microbes from the intestinal lumen into the circulation. Microbial translocation has been proposed to trigger immune activation, inflammation, and coagulopathy, all of which are key factors that drive HIV disease progression and non-HIV comorbidities; however, direct proof of a causal link is still lacking. Here, we have demonstrated that treatment of acutely SIV-infected pigtailed macaques with the drug sevelamer, which binds microbial lipopolysaccharide in the gut, dramatically reduces immune activation and inflammation and slightly reduces viral replication. Furthermore, sevelamer administration reduced coagulation biomarkers, confirming the contribution of microbial translocation in the development of cardiovascular comorbidities in SIV-infected nonhuman primates. Together, our data suggest that early control of microbial translocation may improve the outcome of HIV infection and limit noninfectious comorbidities associated with AIDS.

While simian immunodeficiency viruses (SIVs) are generally nonpathogenic in their natural hosts, dramatic increases in pathogenicity may occur upon cross-species transmission to new hosts. Deciphering the drivers of these increases in virulence is of major interest for understanding the emergence of new human immunodeficiency viruses (HIVs). We transmitted SIVsab from the sabaeus species of African green monkeys (AGMs) to pigtailed macaques (PTMs). High acute viral replication occurred in all SIVsab-infected PTMs, yet the outcome of chronic infection was highly variable, ranging from rapid progression to controlled infection, which was independent of the dynamics of acute viral replication, CD4 + T cell depletion, or preinfection levels of microbial translocation. Infection of seven PTMs with plasma collected at necropsy from a rapid-progressor PTM was consistently highly pathogenic, with high acute and chronic viral replication, massive depletion of memory CD4 + T cells, and disease progression in all PTMs. The plasma inoculum used for the serial passage did not contain adventitious bacterial or viral contaminants. Single-genome amplification showed that this inoculum was significantly more homogenous than the inoculum directly derived from AGMs, pointing to a strain selection in PTMs. In spite of similar peak plasma viral loads between the monkeys in the two passages, immune activation/inflammation levels dramatically increased in PTMs infected with the passaged virus. These results suggest that strain selection and a massive cytokine storm are major factors behind increased pathogenicity of SIV upon serial passage and adaptation of SIVs to new hosts following cross-species transmission. IMPORTANCE We report here that upon cross-species transmission and serial passage of SIVsab from its natural host, the sabaeus African green monkey (AGM), to a new host, the pigtailed macaque (PTM), viral adaptation and increased pathogenicity involve strain selection and a massive cytokine storm. These results permit the design of strategies aimed at preventing cross-species transmission from natural hosts of SIVs to humans in areas of endemicity. Furthermore, our study describes a new animal model for SIV infection. As the outcomes of SIVsab infection in PTMs, African green monkeys, and rhesus macaques are different, the use of these systems enables comparative studies between pathogenic, nonpathogenic, and elite-controlled infections, to gain insight into the mechanisms of SIV immunodeficiency and comorbidities.

African green monkeys (AGMs) are naturally infected with simian immunodeficiency virus (SIV) at high prevalence levels and do not progress to AIDS. Sexual transmission is the main transmission route in AGM, while mother-to-infant transmission (MTIT) is negligible. We investigated SIV transmission in wild AGMs to assess whether or not high SIV prevalence is due to differences in mucosal permissivity to SIV (i.e., whether the genetic bottleneck of viral transmission reported in humans and macaques is also observed in AGMs in the wild). We tested 121 sabaeus AGMs ( Chlorocebus sabaeus ) from the Gambia and found that 53 were SIV infected (44%). By combining serology and viral load quantitation, we identified 4 acutely infected AGMs, in which we assessed the diversity of the quasispecies by single-genome amplification (SGA) and documented that a single virus variant established the infections. We thus show that natural SIV transmission in the wild is associated with a genetic bottleneck similar to that described for mucosal human immunodeficiency virus (HIV) transmission in humans. Flow cytometry assessment of the immune cell populations did not identify major differences between infected and uninfected AGM. The expression of the SIV coreceptor CCR5 on CD4 + T cells dramatically increased in adults, being higher in infected than in uninfected infant and juvenile AGMs. Thus, the limited SIV MTIT in natural hosts appears to be due to low target cell availability in newborns and infants, which supports HIV MTIT prevention strategies aimed at limiting the target cells at mucosal sites. Combined, (i) the extremely high prevalence in sexually active AGMs, (ii) the very efficient SIV transmission in the wild, and (iii) the existence of a fraction of multiparous females that remain uninfected in spite of massive exposure to SIV identify wild AGMs as an acceptable model of exposed, uninfected individuals. IMPORTANCE We report an extensive analysis of the natural history of SIVagm infection in its sabaeus monkey host, the African green monkey species endemic to West Africa. Virtually no study has investigated the natural history of SIV infection in the wild. The novelty of our approach is that we report for the first time that SIV infection has no discernible impact on the major immune cell populations in natural hosts, thus confirming the nonpathogenic nature of SIV infection in the wild. We also focused on the correlates of SIV transmission, and we report, also for the first time, that SIV transmission in the wild is characterized by a major genetic bottleneck, similar to that described for HIV-1 transmission in humans. Finally, we report here that the restriction of target cell availability is a major correlate of the lack of SIV transmission to the offspring in natural hosts of SIVs.

Pathogenesis studies of SIV infection have not been performed to date in wild monkeys due to difficulty in collecting and storing samples on site and the lack of analytical reagents covering the extensive SIV diversity. We performed a large scale study of molecular epidemiology and natural history of SIVagm infection in 225 free-ranging AGMs from multiple locations in South Africa. SIV prevalence (established by sequencing pol, env, and gag) varied dramatically between infant/juvenile (7%) and adult animals (68%) (p, Author Summary We simultaneously assessed, for the first time in a natural host, the epidemiology, diversity and natural history of SIVagmVer infection in wild vervet populations from South Africa. We report that African green monkeys (AGMs) have likely been infected with SIVagm for a long period, ranging from the time of their speciation to Plio-Pleistocene migrations, refuting previous molecular clock calculations suggesting SIVagm to be of recent occurrence. As a result of virus-host coadaptation, SIVagmVer infection is characterized by a lack of disease progression in spite of robust viral replication. We show that very active SIVagm transmission in adult AGMs contrasts with a very limited transmission to their offspring, in spite of massive exposure to SIVagm both in utero and through breastfeeding. The observation that some AGMs remain uninfected in spite of life-long exposure to SIVagm identifies wild vervets as an acceptable animal model for the exposed uninfected individuals, which can be used to identify correlates of resistance to HIV/SIV infection.

The lack of animal models of HIV-related pulmonary arterial hypertension (HIV-PAH) severely limits investigation of this serious disease. While histological evidence of HIV-PAH has been demonstrated in macaques infected with simian immunodeficiency virus (SIV) as well as with chimeric simian/human immunodeficiency virus (SHIV) containing HIV-1-derived Nef protein, other primate models have not been studied. The objective was to document and describe the development of pulmonary vascular changes in macaques infected with SIV or with SIV containing HIV-1-derived envelope protein (SHIV-env). Lung tissue was obtained at necropsy from 13 SHIV (89.6P)-env-infected macaques and 10 SIV (ΔB670)-infected macaques. Pulmonary arterial pathology, including arterial hyperplasia and the presence of plexiform lesions, was compared to normal monkey lung. Pulmonary artery hyperplasia was present in 8 of 13 (62%) SHIV-env-infected macaques and 4/10 (36%) SIV-infected macaques. The most common histopathological lesions were intimal and medial hyperplasia of medium and large pulmonary arteries. Hyperplastic lesions were predominantly due to smooth muscle cell hyperplasia. This is the first report of pulmonary vascular lesions in SHIV-env-infected macaques and confirms prior reports of pulmonary vasculopathy in SIV-infected macaques. The finding of pulmonary arteriopathy in monkeys infected with SHIV not containing HIV-nef suggests that other factors might also be important in the development of HIV-PAH. This SHIV-env model provides a new means to investigate HIV-PAH.

Understanding the mechanism of infection control in elite controllers (EC) may shed light on the correlates of control of disease progression in HIV infection. However, limitations have prevented a clear understanding of the mechanisms of elite controlled infection, as these studies can only be performed at randomly selected late time points in infection, after control is achieved, and the access to tissues is limited. We report that SIVagm infection is elite-controlled in rhesus macaques (RMs) and therefore can be used as an animal model for EC HIV infection. A robust acute infection, with high levels of viral replication and dramatic mucosal CD4+ T cell depletion, similar to pathogenic HIV-1/SIV infections of humans and RMs, was followed by complete and durable control of SIVagm replication, defined as: undetectable VLs in blood and tissues beginning 72 to 90 days postinoculation (pi) and continuing at least 4 years; seroreversion; progressive recovery of mucosal CD4+ T cells, with complete recovery by 4 years pi; normal levels of T cell immune activation, proliferation, and apoptosis; and no disease progression. This “functional cure” of SIVagm infection in RMs could be reverted after 4 years of control of infection by depleting CD8 cells, which resulted in transient rebounds of VLs, thus suggesting that control may be at least in part immune mediated. Viral control was independent of MHC, partial APOBEC restriction was not involved in SIVagm control in RMs and Trim5 genotypes did not impact viral replication. This new animal model of EC lentiviral infection, in which complete control can be predicted in all cases, permits research on the early events of infection in blood and tissues, before the defining characteristics of EC are evident and when host factors are actively driving the infection towards the EC status., Author Summary A small proportion of HIV-infected patients control viral replication and disease progression in the absence of any antiretroviral treatment. Understanding the mechanisms of viral control in these elite controllers may help to identify new therapeutic approaches in order to control HIV infection. However, elite controllers are identified AFTER control is established, therefore it is difficult to identify the virus and host factors that drive the infection to the controlled status. We identified an animal model (the rhesus macaque infection with SIVagm) in which, after massive acute viral replication and CD4+ T cell depletion, SIV infection is controlled in 100% of cases during chronic infection. This “functional cure” of SIVagm infection in rhesus macaques results in a complete immune restoration after four years and can be reverted by depleting the cellular immune responses in vivo. An animal model of elite controlled lentiviral infection in which complete control can be predicted in all cases permits research on the early events of infection when host factors are actively driving the infection towards the controlled status to understand the pathogenesis of HIV/SIV infections and design of new approaches for controlling HIV infection.

Pulmonary colonization by the opportunistic pathogen Pneumocystis jiroveci is common in HIV + subjects and has been associated with development of chronic obstructive pulmonary disease (COPD). Host and environmental factors associated with colonization susceptibility are undefined. Using a simian-human immunodeficiency virus (SHIV) model of HIV infection, the immunologic parameters associated with natural Pneumocystis jiroveci transmission were evaluated. SHIV-infected macaques were exposed to P. jiroveci by cohousing with immunosuppressed, P. jiroveci -colonized macaques in two independent experiments. Serial plasma and bronchoalveolar lavage (BAL) fluid samples were examined for changes in antibody titers to recombinant Pneumocystis -kexin protein (KEX1) and evidence of Pneumocystis colonization by nested PCR of BAL fluid. In experiment 1, 10 of 14 monkeys became Pneumocystis colonized (Pc + ) by 8 weeks post-SHIV infection, while 4 animals remained Pneumocystis colonization negative (Pc − ) throughout the study. In experiment 2, 11 of 17 animals became Pneumocystis colonized by 16 weeks post-SHIV infection, while 6 monkeys remained Pc − . Baseline plasma KEX1-IgG titers were significantly higher in monkeys that remained Pc − , compared to Pc + monkeys, in experiments 1 ( P = 0.013) and 2 ( P = 0.022). Pc − monkeys had greater percentages of Pneumocystis -specific memory B cells after SHIV infection compared to Pc + monkeys ( P = 0.037). After SHIV infection, Pc + monkeys developed progressive obstructive pulmonary disease, whereas Pc − monkeys maintained normal lung function throughout the study. These results demonstrate a correlation between the KEX1 humoral response and the prevention of Pneumocystis colonization and obstructive lung disease in the SHIV model. In addition, these results indicate that an effective Pneumocystis -specific memory B-cell response is maintained despite progressive loss of CD4 + T cells during SHIV infection.

Human immunodeficiency virus (HIV)-infected patients are at increased risk for development of pulmonary complications, including chronic obstructive pulmonary disease (COPD). Inflammation associated with subclinical infection has been postulated to promote COPD. Persistence of Pneumocystis is associated with HIV infection and COPD, although a causal relationship has not been established. We used a simian/human immunodeficiency virus model of HIV infection to study pulmonary effects of Pneumocystis colonization. Simian/human immunodeficiency virus-infected/Pneumocystis-colonized monkeys developed progressive obstructive pulmonary disease characterized by increased emphysematous tissue and bronchial-associated lymphoid tissue. Increased levels of T helper type 2 cytokines and proinflammatory mediators in bronchoalveolar lavage fluid coincided with Pneumocystis colonization and a decline in pulmonary function. These results support the concept that an infectious agent contributes to the development of HIV-associated lung disease and suggest that Pneumocystis colonization may be a risk factor for the development of HIV-associated COPD. Furthermore, this model allows examination of early host responses important to disease progression, thus identifying potential therapeutic targets for COPD.

SIV/HIV infection is associated with B cell dysfunction, the significance of which is not known. We compared the B cell dynamics in blood, lymph nodes (LNs) and gut during SIVsab pathogenic infection of pigtailed macaques (PTMs) and nonprogressive SIVsab infection of African green monkeys (AGMs) by monitoring the B cell subsets, B regulatory cells (Bregs), CD4+ T follicular helper (Tfh) cells, B cell immune activation, apoptosis, exhaustion and homing to the intestine. Binding anti-gp41 and neutralizing antibodies (Nabs) were also measured. Acute SIV infection induced a transient but significant loss of total circulating B cells in PTMs only. In AGMs, total B cell from LNs increased during chronic infection. B cells transiently increased in the gut and naïve subset decreased in all three compartments in both species. Memory B cell subsets showed a different dynamic for both species. Bregs increased in PTM, correlated with IL-10 expression. B cell proliferation occurred in both species. PTMs expressed high baseline levels of α4β7, high degree of B cell activation and apoptosis and high frequency of Tfh. The dynamics of Ab response was similar in both species, but rapid progressor PTMs lacked the ability to mount anti-gp41. Our data show that B cell dysfunction only occurs in pathogenic SIV infection. While B cell changes were not correlated with production of Nabs, rapid disease progression associated a severe incapacity to mount an anti-SIV Ab response.

Adenosine (ADO) is associated with immunosuppression in multiple diseases, yet its role in modulating immune activation/inflammation (IA/INFL) in HIV-1/SIV infection is unclear. We compared changes in ADO pathway-associated markers between African green monkeys (AGMs) that control SIV-related IA/INFL and pigtailed macaques (PTMs) that exhibit IA/INFL associated with AIDS progression. CD39/CD73 and CD26 (which promote ADO production or breakdown to inosine) were assessed by flow cytometry on T cells from blood, lymph nodes (LNs) and intestine of AGMs and PTMs pre and post SIV infection. ADO was measured by mass spectrometry in frozen tissues. Baseline CD39/CD73 expression on Tregs from LNs and intestine were intrinsically high in AGMs and remained high throughout SIV infection. CD26 and inosine did not change in AGMs. In the gut, basal ADO was high in AGMs and further increased early after infection. Conversely, in PTMs, CD26 expression dramatically increased in the gut early in infection, a change associated with increased inosine. CD39/CD73 only increased during late infection in PTMs. Our results suggest a key role for ADO in the control of IA/INFL in nonprogressive SIV infections and that ADO production may be counteracted by the early increase of CD26 in pathogenic HIV/SIV. Furthermore, changes of ADO levels predominately occur in the gut rather than in blood or LNs, suggesting that future studies of the ADO pathway should focus on mucosal sites of viral replication.

We assessed the role of myeloid dendritic cells (mDCs) in the outcome of SIV infection by comparing and contrasting their frequency, mobilization, phenotype, cytokine production and apoptosis in pathogenic (pigtailed macaques, PTMs), nonpathogenic (African green monkeys, AGMs) and controlled (rhesus macaques, RMs) SIVagmSab infection. Through the identification of recently replicating cells, we demonstrated that mDC mobilization from the bone marrow occurred in all species postinfection, being most prominent in RMs. Circulating mDCs were depleted with disease progression in PTMs, recovered to baseline values after the viral peak in AGMs, and significantly increased at the time of virus control in RMs. Rapid disease progression in PTMs was associated with low baseline levels and incomplete recovery of circulating mDCs during chronic infection. mDC recruitment to the intestine occurred in all pathogenic scenarios, but loss of mucosal mDCs was associated only with progressive infection. Sustained mDC immune activation occurred throughout infection in PTMs and was associated with increased bystander apoptosis in blood and intestine. Conversely, mDC activation occurred only during acute infection in nonprogressive and controlled infections. Postinfection, circulating mDCs rapidly became unresponsive to TLR7/8 stimulation in all species. Yet, stimulation with LPS, a bacterial product translocated in circulation only in SIV-infected PTMs, induced mDC hyperactivation, apoptosis and excessive production of proinflammatory cytokines. After infection, spontaneous production of proinflammatory cytokines by mucosal mDCs increased only in progressor PTMs. We thus propose that mDCs promote tolerance to SIV in the biological systems that lack intestinal dysfunction. In progressive infections, mDC loss and excessive activation of residual mDCs by SIV and additional stimuli, such as translocated microbial products, enhance generalized immune activation and inflammation. Our results thus provide a mechanistic basis for the role of mDCs in the pathogenesis of AIDS and elucidate the causes of mDC loss during progressive HIV/SIV infections., Author Summary Myeloid dendritic cells (mDCs) are potent antigen-presenting cells that regulate both innate and adaptive immune responses and act as “watch-dogs”, sensing and controlling aberrant immune activation; as such, they may significantly impact the outcome of HIV/SIV infection. By comparing and contrasting the frequency, function, migration to tissues and levels of activation and apoptosis in progressive, nonprogressive and elite-controlled SIV infections, we investigated the mechanisms responsible for mDC loss in HIV/SIV infection and their role in driving progression to AIDS. We report that progression to AIDS is associated with low mDC preinfection levels and depletion throughout infection, due to massive migration of these cells to mucosal sites and excessive cell death by apoptosis. We also show that residual mDCs from blood and intestine have a high capacity to produce proinflammatory cytokines, thus contributing to the increased immune activation and inflammation characteristic of progressive infections.