Too Hot to Handle: Early Temperature Management and Unique Treatment of Hyperpyrexia in SARS-CoV2 Encephalopathy.

A 45-year-old otherwise healthy active duty male was admitted to the medical intensive care unit for severe acute respiratory syndrome-coronavirus 2 (SARS-CoV2) encephalopathy associated with hyperpyrexia. Magnetic resonance imaging findings demonstrated cytotoxic lesions primarily at the midline of the splenium of corpus callosum (CLOCC). Similar cases involving hyperpyrexia in the setting of SARS-CoV2 infection have demonstrated exceedingly high-mortality outcomes. Three mechanisms exist as to the likely underlying pathophysiology of SARS-CoV2-induced hyperpyrexia: direct brain injury, persistent immune dysregulation of cytokines, and vascular thrombosis. To date, no cases have reported imaging findings consistent with SARS-CoV2-induced brain injury leading to hyperpyrexia. Magnetic resonance imaging findings in this case, however, may finally elucidate the underlying mechanism for hyperpyrexia in this population. Magnetic resonance imaging findings in this case show diffusion restriction of the corpus callosum without evidence of any Central Nervous System (CNS) vessel abnormality. Given that hyperpyrexia has a clear association with increased mortality and morbidity in the SARS-CoV2 infected population, the decision to initiate steroids and remdesivir regardless of respiratory status was made for the concern for severe SARS-CoV2 infection as demonstrated by the CLOCC. Additional cases will be needed to assess their potential use as a radiological marker of disease burden.

Interleukin-10 contributes to reservoir establishment and persistence in SIV-infected macaques treated with antiretroviral therapy.

Interleukin-10 (IL-10) is an immunosuppressive cytokine that signals through STAT3 to regulate T follicular helper (Tfh) cell differentiation and germinal center formation. In SIV-infected macaques, levels of IL-10 in plasma and lymph nodes (LNs) were induced by infection and not normalized with antiretroviral therapy (ART). During chronic infection, plasma IL-10 and transcriptomic signatures of IL-10 signaling were correlated with the cell-associated SIV-DNA content within LN CD4+ memory subsets, including Tfh cells, and predicted the frequency of CD4+ Tfh cells and their cell-associated SIV-DNA content during ART, respectively. In ART-treated rhesus macaques, cells harboring SIV-DNA by DNAscope were preferentially found in the LN B cell follicle in proximity to IL-10. Finally, we demonstrated that the in vivo neutralization of soluble IL-10 in ART-treated, SIV-infected macaques reduced B cell follicle maintenance and, by extension, LN memory CD4+ T cells, including Tfh cells and those expressing PD-1 and CTLA-4. Thus, these data support a role for IL-10 in maintaining a pool of target cells in lymphoid tissue that serve as a niche for viral persistence. Targeting IL-10 signaling to impair CD4+ T cell survival and improve antiviral immune responses may represent a novel approach to limit viral persistence in ART-suppressed people living with HIV.

Combinatorial immunotherapy induces tumor-infiltrating CD8+ T cells with distinct functional, migratory, and stem-like properties.

BACKGROUND: Programmed death (ligand) 1 (PD-(L)1) blockade and OX40/4-1BB costimulation have been separately evaluated in the clinic to elicit potent antitumor T cell responses. The precise mechanisms underlying single agent activity are incompletely understood. It also remains unclear if combining individual therapies leads to synergism, elicits novel immune mechanisms, or invokes additive effects. METHODS: We performed high-dimensional flow cytometry and single-cell RNA sequencing-based immunoprofiling of murine tumor-infiltrating lymphocytes (TILs) isolated from hosts bearing B16 or MC38 syngeneic tumors. This baseline infiltrate was compared to TILs after treatment with either anti-PD-(L)1, anti-OX40, or anti-4-1BB as single agents or as double and triple combinatorial therapies. Fingolimod treatment and CXCR3 blockade were used to evaluate the contribution of intratumoral versus peripheral CD8+ T cells to therapeutic efficacy. RESULTS: We identified CD8+ T cell subtypes with distinct functional and migratory signatures highly predictive of tumor rejection upon treatment with single agent versus combination therapies. Rather than reinvigorating terminally exhausted CD8+ T cells, OX40/4-1BB agonism expanded a stem-like PD-1loKLRG-1+Ki-67+CD8+ T cell subpopulation, which PD-(L)1 blockade alone did not. However, PD-(L)1 blockade synergized with OX40/4-1BB costimulation by dramatically enhancing stem-like TIL presence via a CXCR3-dependent mechanism. CONCLUSIONS: Our findings provide new mechanistic insights into the interplay between components of combinatorial immunotherapy, where agonism of select costimulatory pathways seeds a pool of stem-like CD8+ T cells more responsive to immune checkpoint blockade (ICB).

Intra-Tumoral Activation of Endosomal TLR Pathways Reveals a Distinct Role for TLR3 Agonist Dependent Type-1 Interferons in Shaping the Tumor Immune Microenvironment.

Toll-like receptor (TLR) agonists have received considerable attention as therapeutic targets for cancer immunotherapy owing to their ability to convert immunosuppressive tumor microenvironments towards a more T-cell inflamed phenotype. However, TLRs differ in their cell expression profiles and intracellular signaling pathways, raising the possibility that distinct TLRs differentially influence the tumor immune microenvironment. Using single-cell RNA-sequencing, we address this by comparing the tumor immune composition of B16F10 melanoma following treatment with agonists of TLR3, TLR7, and TLR9. Marked differences are observed between treatments, including decreased tumor-associated macrophages upon TLR7 agonist treatment. A biased type-1 interferon signature is elicited upon TLR3 agonist treatment as opposed to a type-2 interferon signature with TLR9 agonists. TLR3 stimulation was associated with increased macrophage antigen presentation gene expression and decreased expression of PD-L1 and the inhibitory receptors Pirb and Pilra on infiltrating monocytes. Furthermore, in contrast to TLR7 and TLR9 agonists, TLR3 stimulation ablated FoxP3 positive CD4 T cells and elicited a distinct CD8 T cell activation phenotype highlighting the potential for distinct synergies between TLR agonists and combination therapy agents.

Increased homeostatic cytokines and stability of HIV-infected memory CD4 T-cells identify individuals with suboptimal CD4 T-cell recovery on-ART.

Clinical outcomes are inferior for individuals with HIV having suboptimal CD4 T-cell recovery during antiretroviral therapy (ART). We investigated if the levels of infection and the response to homeostatic cytokines of CD4 T-cell subsets contributed to divergent CD4 T-cell recovery and HIV reservoir during ART by studying virologically-suppressed immunologic responders (IR, achieving a CD4 cell count >500 cells/µL on or before two years after ART initiation), and virologically-suppressed suboptimal responders (ISR, did not achieve a CD4 cell count >500 cells/µL in the first two years after ART initiation). Compared to IR, ISR demonstrated higher levels of HIV-DNA in naïve, central (CM), transitional (TM), and effector (EM) memory CD4 T-cells in blood, both pre- and on-ART, and specifically in CM CD4 T-cells in LN on-ART. Furthermore, ISR had higher pre-ART plasma levels of IL-7 and IL-15, cytokines regulating T-cell homeostasis. Notably, pre-ART PD-1 and TIGIT expression levels were higher in blood CM and TM CD4 T-cells for ISR; this was associated with a significantly lower fold-changes in HIV-DNA levels between pre- and on-ART time points exclusively on CM and TM T-cell subsets, but not naïve or EM T-cells. Finally, the frequency of CM CD4 T-cells expressing PD-1 or TIGIT pre-ART as well as plasma levels of IL-7 and IL-15 predicted HIV-DNA content on-ART. Our results establish the association between infection, T-cell homeostasis, and expression of PD-1 and TIGIT in long-lived CD4 T-cell subsets prior to ART with CD4 T-cell recovery and HIV persistence on-ART.

IL-21 and IFNα therapy rescues terminally differentiated NK cells and limits SIV reservoir in ART-treated macaques.

Unlike HIV infection, which progresses to AIDS absent suppressive anti-retroviral therapy, nonpathogenic infections in natural hosts, such African green monkeys, are characterized by a lack of gut microbial translocation and robust secondary lymphoid natural killer cell responses resulting in an absence of chronic inflammation and limited SIV dissemination in lymph node B-cell follicles. Here we report, using the pathogenic model of antiretroviral therapy-treated, SIV-infected rhesus macaques that sequential interleukin-21 and interferon alpha therapy generate terminally differentiated blood natural killer cells (NKG2a/clowCD16+) with potent human leukocyte antigen-E-restricted activity in response to SIV envelope peptides. This is in contrast to control macaques, where less differentiated, interferon gamma-producing natural killer cells predominate. The frequency and activity of terminally differentiated NKG2a/clowCD16+ natural killer cells correlates with a reduction of replication-competent SIV in lymph node during antiretroviral therapy and time to viral rebound following analytical treatment interruption. These data demonstrate that African green monkey-like natural killer cell differentiation profiles can be rescued in rhesus macaques to promote viral clearance in tissues.

Virologic and Immunologic Features of Simian Immunodeficiency Virus Control Post-ART Interruption in Rhesus Macaques.

Antiretroviral therapy (ART) cannot eradicate human immunodeficiency virus (HIV) and a rapid rebound of virus replication follows analytical treatment interruption (ATI) in the vast majority of HIV-infected individuals. Sustained control of HIV replication without ART has been documented in a subset of individuals, defined as posttreatment controllers (PTCs). The key determinants of post-ART viral control remain largely unclear. Here, we identified 7 SIVmac239-infected rhesus macaques (RMs), defined as PTCs, who started ART 8 weeks postinfection, continued ART for >7 months, and controlled plasma viremia at <104 copies/ml for up to 8 months after ATI and <200 copies/ml at the latest time point. We characterized immunologic and virologic features associated with post-ART SIV control in blood, lymph node (LN), and colorectal (RB) biopsy samples compared to 15 noncontroller (NC) RMs. Before ART initiation, PTCs had higher CD4 T cell counts, lower plasma viremia, and SIV-DNA content in blood and LN compared to NCs, but had similar CD8 T cell function. While levels of intestinal CD4 T cells were similar, PTCs had higher frequencies of Th17 cells. On ART, PTCs had significantly lower levels of residual plasma viremia and SIV-DNA content in blood and tissues. After ATI, SIV-DNA content rapidly increased in NCs, while it remained stable or even decreased in PTCs. Finally, PTCs showed immunologic benefits of viral control after ATI, including higher CD4 T cell levels and reduced immune activation. Overall, lower plasma viremia, reduced cell-associated SIV-DNA, and preserved Th17 homeostasis, including at pre-ART, are the main features associated with sustained viral control after ATI in SIV-infected RMs.IMPORTANCE While effective, antiretroviral therapy is not a cure for HIV infection. Therefore, there is great interest in achieving viral remission in the absence of antiretroviral therapy. Posttreatment controllers represent a small subset of individuals who are able to control HIV after cessation of antiretroviral therapy, but characteristics associated with these individuals have been largely limited to peripheral blood analysis. Here, we identified 7 SIV-infected rhesus macaques that mirrored the human posttreatment controller phenotype and performed immunologic and virologic analysis of blood, lymph node, and colorectal biopsy samples to further understand the characteristics that distinguish them from noncontrollers. Lower viral burden and preservation of immune homeostasis, including intestinal Th17 cells, both before and after ART, were shown to be two major factors associated with the ability to achieve posttreatment control. Overall, these results move the field further toward understanding of important characteristics of viral control in the absence of antiretroviral therapy.

CTLA-4 and PD-1 dual blockade induces SIV reactivation without control of rebound after antiretroviral therapy interruption.

The primary human immunodeficiency virus (HIV) reservoir is composed of resting memory CD4+ T cells, which often express the immune checkpoint receptors programmed cell death protein 1 (PD-1) and cytotoxic T lymphocyte-associated protein 4 (CTLA-4), which limit T cell activation via synergistic mechanisms. Using simian immunodeficiency virus (SIV)-infected, long-term antiretroviral therapy (ART)-treated rhesus macaques, we demonstrate that PD-1, CTLA-4 and dual CTLA-4/PD-1 immune checkpoint blockade using monoclonal antibodies is well tolerated, with evidence of bioactivity in blood and lymph nodes. Dual blockade was remarkably more effective than PD-1 blockade alone in enhancing T cell cycling and differentiation, expanding effector-memory T cells and inducing robust viral reactivation in plasma and peripheral blood mononuclear cells. In lymph nodes, dual CTLA-4/PD-1 blockade, but not PD-1 alone, decreased the total and intact SIV-DNA in CD4+ T cells, and SIV-DNA and SIV-RNA in B cell follicles, a major site of viral persistence during ART. None of the tested interventions enhanced SIV-specific CD8+ T cell responses during ART or viral control after ART interruption. Thus, despite CTLA-4/PD-1 blockade inducing robust latency reversal and reducing total levels of integrated virus, the degree of reservoir clearance was still insufficient to achieve viral control. These results suggest that immune checkpoint blockade regimens targeting PD-1 and/or CTLA-4, if performed in people living with HIV with sustained aviremia, are unlikely to induce HIV remission in the absence of additional interventions.

Fingolimod retains cytolytic T cells and limits T follicular helper cell infection in lymphoid sites of SIV persistence.

Lymph nodes (LN) and their resident T follicular helper CD4+ T cells (Tfh) are a critical site for HIV replication and persistence. Therefore, optimizing antiviral activity in lymphoid tissues will be needed to reduce or eliminate the HIV reservoir. In this study, we retained effector immune cells in LN of cART-suppressed, SIV-infected rhesus macaques by treatment with the lysophospholipid sphingosine-1 phosphate receptor modulator FTY720 (fingolimod). FTY720 was remarkably effective in reducing circulating CD4+ and CD8+ T cells, including those with cytolytic potential, and in increasing the number of these T cells retained in LN, as determined directly in situ by histocytometry and immunohistochemistry. The FTY720-induced inhibition of T cell egress from LN resulted in a measurable decrease of SIV-DNA content in blood as well as in LN Tfh cells in most treated animals. In conclusion, FTY720 administration has the potential to limit viral persistence, including in the critical Tfh cellular reservoir. These findings provide rationale for strategies designed to retain antiviral T cells in lymphoid tissues to target HIV remission.

Bone Marrow-Derived CD4+ T Cells Are Depleted in Simian Immunodeficiency Virus-Infected Macaques and Contribute to the Size of the Replication-Competent Reservoir.

The bone marrow (BM) is the key anatomic site for hematopoiesis and plays a significant role in the homeostasis of mature T cells. However, very little is known on the phenotype of BM-derived CD4+ T cells, their fate during simian immunodeficiency virus (SIV) infection, and their contribution to viral persistence during antiretroviral therapy (ART). In this study, we characterized the immunologic and virologic status of BM-derived CD4+ T cells in rhesus macaques prior to SIV infection, during the early chronic phase of infection, and during ART. We found that BM memory CD4+ T cells are significantly depleted following SIV infection, at levels that are similar to those measured in the peripheral blood (PB). In addition, BM-derived memory CD4+ T cells include a high frequency of cells that express the coinhibitory receptors CTLA-4 and PD-1, two subsets previously shown to be enriched in the viral reservoir; these cells express Ki-67 at levels similar to or higher than the same cells in PB. Finally, when we analyzed SIV-infected RMs in which viral replication was effectively suppressed by 12 months of ART, we found that BM CD4+ T cells harbor SIV DNA and SIV RNA at levels comparable to those of PB CD4+ T cells, including replication-competent SIV. Thus, BM is a largely understudied anatomic site of the latent reservoir which contributes to viral persistence during ART and needs to be further characterized and targeted when designing therapies for a functional or sterilizing cure to HIV.IMPORTANCE The latent viral reservoir is one of the major obstacles in purging the immune system of HIV. It is paramount that we elucidate which anatomic compartments harbor replication-competent virus, which upon ART interruption results in viral rebound and pathogenesis. In this study, using the rhesus macaque model of SIV infection and ART, we examined the immunologic status of the BM and its role as a potential sanctuary for latent virus. We found that the BM compartment undergoes a similar depletion of memory CD4+ T cells as PB, and during ART treatment the BM-derived memory CD4+ T cells contain high levels of cells expressing CTLA-4 and PD-1, as well as amounts of cell-associated SIV DNA, SIV RNA, and replication-competent virus comparable to those in PB. These results enrich our understanding of which anatomic compartments harbor replication virus and suggest that BM-derived CD4+ T cells need to be targeted by therapeutic strategies aimed at achieving an HIV cure.

Systemic DPP4 activity is reduced during primary HIV-1 infection and is associated with intestinal RORC+ CD4+ cell levels: a surrogate marker candidate of HIV-induced intestinal damage.

INTRODUCTION: Combined anti-retroviral therapy (cART) transformed HIV-1 from a deadly disease into a chronic infection, but does not cure HIV infection. It also does not fully restore HIV-induced gut damage unless administered extremely early after infection. Additional biomarkers are needed to evaluate the capacity of therapies aimed at HIV remission/cure to restore HIV-induced intestinal immune damage and limit chronic inflammation. Herein, we aimed to identify a systemic surrogate marker whose levels would reflect gut immune damage such as intestinal Th17 cell loss starting from primary HIV-1 infection. METHODS: Biomarker discovery approaches were performed in four independent cohorts, covering HIV-1 primary and chronic infection in 496 naïve or cART-treated patients (Amsterdam cohort (ACS), ANRS PRIMO, COPANA and CODEX cohorts). The concentration and activity of soluble Dipeptidylpeptidase 4 (sDPP4) were quantified in the blood from these patients, including pre- and post-infection samples in the ACS cohort. For quantification of DPP4 in the gut, we utilized two non-human primate models, representing pathogenic (macaque) and non-pathogenic (African green monkey) SIV infection. Four gut compartments were analysed in each animal model (ileum, jejunum, colon and rectum) for quantification of DPP4, RORC and TBX21 gene expression in sorted CD4+ cells. To analyse if sDPP4 levels increase when Th17 cells were restored, we quantified sDPP4 in plasma from SIV-infected macaques treated with IL-21. RESULTS: We showed that sDPP4 levels were strongly decreased in primary HIV-1 infection. Strikingly, sDPP4 levels in primary HIV-1 infection predicted time to AIDS. They were not increased by cART in chronic HIV-1 infection (median 36 months on cART). In the gut of SIV-infected non-human primates, DPP4 mRNA was higher in CD4+ than CD4- leucocytes. DPP4 specifically correlated with RORC expression, a Th17 marker, in CD4+ cells from the intestine. We further demonstrated that sDPP4 activity levels were increased in animals treated with IL-21 and that this increase was associated with restoration of the Th17 compartment and reduced inflammation. Furthermore, DPP4 mRNA levels in small intestine CD4+ cells positively correlated with circulating DPP4 activity. CONCLUSION: These data provide evidence that blood sDPP4 levels could be useful as a correlate for HIV-induced intestinal damage.

CTLA-4+PD-1- Memory CD4+ T Cells Critically Contribute to Viral Persistence in Antiretroviral Therapy-Suppressed, SIV-Infected Rhesus Macaques.

Antiretroviral therapy (ART) suppresses viral replication in HIV-infected individuals but does not eliminate the reservoir of latently infected cells. Recent work identified PD-1+ follicular helper T (Tfh) cells as an important cellular compartment for viral persistence. Here, using ART-treated, SIV-infected rhesus macaques, we show that CTLA-4+PD-1- memory CD4+ T cells, which share phenotypic markers with regulatory T cells, were enriched in SIV DNA in blood, lymph nodes (LN), spleen, and gut, and contained replication-competent and infectious virus. In contrast to PD-1+ Tfh cells, SIV-enriched CTLA-4+PD-1- CD4+ T cells were found outside the B cell follicle of the LN, predicted the size of the persistent viral reservoir during ART, and significantly increased their contribution to the SIV reservoir with prolonged ART-mediated viral suppression. We have shown that CTLA-4+PD-1- memory CD4+ T cells are a previously unrecognized component of the SIV and HIV reservoir that should be therapeutically targeted for a functional HIV-1 cure.

Antiretroviral Therapy in Simian Immunodeficiency Virus-Infected Sooty Mangabeys: Implications for AIDS Pathogenesis.

UNLABELLED: Simian immunodeficiency virus (SIV)-infected sooty mangabeys (SMs) do not develop AIDS despite high levels of viremia. Key factors involved in the benign course of SIV infection in SMs are the absence of chronic immune activation and low levels of infection of CD4(+) central memory (TCM) and stem cell memory (TSCM) T cells. To better understand the role of virus replication in determining the main features of SIV infection in SMs, we treated 12 SMs with a potent antiretroviral therapy (ART) regimen for 2 to 12 months. We observed that ART suppressed viremia to <60 copies/ml of plasma in 10 of 12 animals and induced a variable decrease in the level of cell-associated SIV DNA in peripheral blood (average changes of 0.9-, 1.1-, 1.5-, and 3.7-fold for CD4(+) transitional memory [TTM], TCM, effector memory [TEM], and TSCM cells, respectively). ART-treated SIV-infected SMs showed (i) increased percentages of circulating CD4(+) TCM cells, (ii) increased levels of CD4(+) T cells in the rectal mucosa, and (iii) significant declines in the frequencies of HLA-DR(+) CD8(+) T cells in the blood and rectal mucosa. In addition, we observed that ART interruption resulted in rapid viral rebound in all SIV-infected SMs, indicating that the virus reservoir persists for at least a year under ART despite lower infection levels of CD4(+) TCM and TSCM cells than those seen in pathogenic SIV infections of macaques. Overall, these data indicate that ART induces specific immunological changes in SIV-infected SMs, thus suggesting that virus replication affects immune function even in the context of this clinically benign infection. IMPORTANCE: Studies of natural, nonpathogenic simian immunodeficiency virus (SIV) infection of African monkeys have provided important insights into the mechanisms responsible for the progression to AIDS during pathogenic human immunodeficiency virus (HIV) infection of humans and SIV infection of Asian macaques. In this study, for the first time, we treated SIV-infected sooty mangabeys, a natural host for the infection, with a potent antiretroviral therapy (ART) regimen for periods ranging from 2 to 12 months and monitored in detail how suppression of virus replication affected the main virological and immunological features of this nonpathogenic infection. The observed findings provide novel information on both the pathogenesis of residual immunological disease under ART during pathogenic infection and the mechanisms involved in virus persistence during primate lentiviral infections.

Loss of Function of Intestinal IL-17 and IL-22 Producing Cells Contributes to Inflammation and Viral Persistence in SIV-Infected Rhesus Macaques.

In HIV/SIV-infected humans and rhesus macaques (RMs), a severe depletion of intestinal CD4(+) T-cells producing interleukin IL-17 and IL-22 associates with loss of mucosal integrity and chronic immune activation. However, little is known about the function of IL-17 and IL-22 producing cells during lentiviral infections. Here, we longitudinally determined the levels and functions of IL-17, IL-22 and IL-17/IL-22 producing CD4(+) T-cells in blood, lymph node and colorectum of SIV-infected RMs, as well as how they recover during effective ART and are affected by ART interruption. Intestinal IL-17 and IL-22 producing CD4(+) T-cells are polyfunctional in SIV-uninfected RMs, with the large majority of cells producing four or five cytokines. SIV infection induced a severe dysfunction of colorectal IL-17, IL-22 and IL-17/IL-22 producing CD4(+) T-cells, the extent of which associated with the levels of immune activation (HLA-DR(+)CD38(+)), proliferation (Ki-67+) and CD4(+) T-cell counts before and during ART. Additionally, Th17 cell function during ART negatively correlated with residual plasma viremia and levels of sCD163, a soluble marker of inflammation and disease progression. Furthermore, IL-17 and IL-22 producing cell frequency and function at various pre, on, and off-ART experimental points associated with and predicted total SIV-DNA content in the colorectum and blood. While ART restored Th22 cell function to levels similar to pre-infection, it did not fully restore Th17 cell function, and all cell types were rapidly and severely affected--both quantitatively and qualitatively--after ART interruption. In conclusion, intestinal IL-17 producing cell function is severely impaired by SIV infection, not fully normalized despite effective ART, and strongly associates with inflammation as well as SIV persistence off and on ART. As such, strategies able to preserve and/or regenerate the functions of these CD4(+) T-cells central for mucosal immunity are critically needed in future HIV cure research.

Interleukin-21 combined with ART reduces inflammation and viral reservoir in SIV-infected macaques.

Despite successful control of viremia, many HIV-infected individuals given antiretroviral therapy (ART) exhibit residual inflammation, which is associated with non-AIDS-related morbidity and mortality and may contribute to virus persistence during ART. Here, we investigated the effects of IL-21 administration on both inflammation and virus persistence in ART-treated, SIV-infected rhesus macaques (RMs). Compared with SIV-infected animals only given ART, SIV-infected RMs given both ART and IL-21 showed improved restoration of intestinal Th17 and Th22 cells and a more effective reduction of immune activation in blood and intestinal mucosa, with the latter maintained through 8 months after ART interruption. Additionally, IL-21, in combination with ART, was associated with reduced levels of SIV RNA in plasma and decreased CD4(+) T cell levels harboring replication-competent virus during ART. At the latest experimental time points, which were up to 8 months after ART interruption, plasma viremia and cell-associated SIV DNA levels remained substantially lower than those before ART initiation in IL-21-treated animals but not in controls. Together, these data suggest that IL-21 supplementation of ART reduces residual inflammation and virus persistence in a relevant model of lentiviral disease and warrants further investigation as a potential intervention for HIV infection.

Replicative fitness of transmitted HIV-1 drives acute immune activation, proviral load in memory CD4+ T cells, and disease progression.

HIV-1 infection is characterized by varying degrees of chronic immune activation and disruption of T-cell homeostasis, which impact the rate of disease progression. A deeper understanding of the factors that influence HIV-1-induced immunopathology and subsequent CD4(+) T-cell decline is critical to strategies aimed at controlling or eliminating the virus. In an analysis of 127 acutely infected Zambians, we demonstrate a dramatic and early impact of viral replicative capacity (vRC) on HIV-1 immunopathogenesis that is independent of viral load (VL). Individuals infected with high-RC viruses exhibit a distinct inflammatory cytokine profile as well as significantly elevated T-cell activation, proliferation, and CD8(+) T-cell exhaustion, during the earliest months of infection. Moreover, the vRC of the transmitted virus is positively correlated with the magnitude of viral burden in naive and central memory CD4(+) T-cell populations, raising the possibility that transmitted viral phenotypes may influence the size of the initial latent viral reservoir. Taken together, these findings support an unprecedented role for the replicative fitness of the founder virus, independent of host protective genes and VL, in influencing multiple facets of HIV-1-related immunopathology, and that a greater focus on this parameter could provide novel approaches to clinical interventions.

Animal models in HIV cure research.

Current HIV antiretroviral therapy (ART) successfully inhibits viral replication in the majority of HIV-infected individuals. However, ART is not curative and lifelong adherence is required. Despite the undisputed benefit of ART, long-lived latently infected cells that carry HIV-integrated DNA remain. Hence, upon ART interruption, HIV-infected subjects experience viral rebound. Interestingly, similar disease course occurs in the well-characterised animal model of SIV-infected non-human primates. Using these animal models to investigate the mechanisms involved in the generation of latently infected cells, define the phenotypic and anatomical nature of persistent viral reservoirs, and test novel interventions for viral eradication, is critical for strengthening our understanding of HIV persistence and developing novel therapeutics aimed at curing HIV. In this review, we discuss the current animal models used in AIDS cure research, with a particular focus on non-human primates, and outline the experimental strategies explored in the quest for virus eradication.

Reconstitution of intestinal CD4 and Th17 T cells in antiretroviral therapy suppressed HIV-infected subjects: implication for residual immune activation from the results of a clinical trial.

INTRODUCTION: During HIV infection the severe depletion of intestinal CD4+ T-cells is associated with microbial translocation, systemic immune activation, and disease progression. This study examined intestinal and peripheral CD4+ T-cell subsets reconstitution under combined antiretroviral therapy (cART), and systemic immune activation markers. METHODS: This longitudinal single-arm pilot study evaluates CD4+ T cells, including Th1 and Th17, in gut and blood and soluble markers for inflammation in HIV-infected individuals before (M0) and after eight (M8) months of cART. From January 2010 to December 2011, 10 HIV-1 naïve patients were screened and 9 enrolled. Blood and gut CD4+ T-cells subsets and cellular immune activation were determined by flow-cytometry and plasma soluble CD14 by ELISA. CD4+ Th17 cells were detected in gut biopsies by immunohistochemistry. Microbial translocation was measured by limulus-amebocyte-lysate assay to detect bacterial lipopolysaccharide (LPS) and PCR Real Time to detect plasma bacterial 16S rDNA. RESULTS: Eight months of cART increased intestinal CD4+ and Th17 cells and reduced levels of T-cell activation and proliferation. The magnitude of intestinal CD4+ T-cell reconstitution correlated with the reduction of plasma LPS. Importantly, the magnitude of Th17 cells reconstitution correlated directly with blood CD4+ T-cell recovery. CONCLUSION: Short-term antiretroviral therapy resulted in a significant increase in the levels of total and Th17 CD4+ T-cells in the gut mucosa and in decline of T-cell activation. The observation that pre-treatment levels of CD4+ and of CD8+ T-cell activation are predictors of the magnitude of Th17 cell reconstitution following cART provides further rationale for an early initiation of cART in HIV-infected individuals. TRIAL REGISTRATION: ClinicalTrials.gov NCT02097381.

CD4 depletion in SIV-infected macaques results in macrophage and microglia infection with rapid turnover of infected cells.

In rhesus macaques (RMs), experimental depletion of CD4+ T-cells prior to SIV infection results in higher viremia and emergence of CD4-independent SIV-envelopes. In this study we used the rhesus recombinant anti-CD4 antibody CD4R1 to deplete RM CD4+ T-cells prior to SIVmac251 infection and investigate the sources of the increased viral burden and the lifespan of productively infected cells. CD4-depleted animals showed (i) set-point viral load two-logs higher than controls; (ii) macrophages constituting 80% of all SIV vRNA+ cells in lymph node and mucosal tissues; (iii) substantial expansion of pro-inflammatory monocytes; (iv) aberrant activation and infection of microglial cells; and (v) lifespan of productively infected cells significantly longer in comparison to controls, but markedly shorter than previously estimated for macrophages. The net effect of CD4+ T-cell depletion is an inability to control SIV replication and a shift in the tropism of infected cells to macrophages, microglia, and, potentially, other CD4-low cells which all appear to have a shortened in vivo lifespan. We believe these findings have important implications for HIV eradication studies.