Human Galectin-9 Is a Potent Mediator of HIV Transcription and Reactivation

Immune regulatory networks coordinated by glycans and glycan-binding proteins in autoimmunity and infection

The immune system is coordinated by an intricate network of stimulatory and inhibitory circuits that regulate host responses against endogenous and exogenous insults. Disruption of these safeguard and homeostatic mechanisms can lead to unpredictable inflammatory and autoimmune responses, whereas deficiency of immune stimulatory pathways may orchestrate immunosuppressive programs that contribute to perpetuate chronic infections, but also influence cancer development and progression. Glycans have emerged as essential components of homeostatic circuits, acting as fine-tuners of immunological responses and potential molecular targets for manipulation of immune tolerance and activation in a wide range of pathologic settings. Cell surface glycans, present in cells, tissues and the extracellular matrix, have been proposed to serve as "self-associated molecular patterns" that store structurally relevant biological data. The responsibility of deciphering this information relies on different families of glycan-binding proteins (including galectins, siglecs and C-type lectins) which, upon recognition of specific carbohydrate structures, can recalibrate the magnitude, nature and fate of immune responses. This process is tightly regulated by the diversity of glycan structures and the establishment of multivalent interactions on cell surface receptors and the extracellular matrix. Here we review the spatiotemporal regulation of selected glycan-modifying processes including mannosylation, complex N-glycan branching, core 2 O-glycan elongation, LacNAc extension, as well as terminal sialylation and fucosylation. Moreover, we illustrate examples that highlight the contribution of these processes to the control of immune responses and their integration with canonical tolerogenic pathways. Finally, we discuss the power of glycans and glycan-binding proteins as a source of immunomodulatory signals that could be leveraged for the treatment of autoimmune inflammation and chronic infection.

Human galectin-9 potently enhances SARS-CoV-2 replication and inflammation in airway epithelial cells

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has caused a global economic and health crisis. Recently, plasma levels of galectin-9 (Gal-9), a β-galactoside-binding lectin involved in immune regulation and viral immunopathogenesis, were reported to be elevated in the setting of severe COVID-19 disease. However, the impact of Gal-9 on SARS-CoV-2 infection and immunopathology remained to be elucidated. In this study, we demonstrate that Gal-9 treatment potently enhances SARS-CoV-2 replication in human airway epithelial cells (AECs), including immortalized AECs and primary AECs cultured at the air-liquid interface. Gal-9-glycan interactions promote SARS-CoV-2 attachment and entry into AECs in an angiotensin-converting enzyme 2 (ACE2)-dependent manner, enhancing the binding of the viral spike protein to ACE2. Transcriptomic analysis revealed that Gal-9 and SARS-CoV-2 infection synergistically induced the expression of key pro-inflammatory programs in AECs, including the IL-6, IL-8, IL-17, EIF2, and TNFα signaling pathways. Our findings suggest that manipulation of Gal-9 should be explored as a therapeutic strategy for SARS-CoV-2 infection.

Antiretroviral Treatment-Induced Galectin-9 Might Impact HIV Viremia in Addition to Contributing to Inflammaging

BACKGROUND

Galectin-9 induces HIV reactivation and also contributes to non-AIDS events through inflammaging. Hence, it is important to assess its levels in HIV-infected individuals to determine their association with HIV viremia and other comorbidities.

METHODS

Plasma galectin-9 levels were estimated in viremic (n = 152) and aviremic (n = 395) individuals on first-line antiretroviral therapy (ART). They were assessed for correlation with HIV-1 viral load (VL), CD4 count, and ART duration, as well as for receiver operating characteristic curve analysis.

RESULT

Plasma galectin-9 levels correlated positively with VL (r = 0.507, p < 0.0001) and ART duration (r = 0.308, p = 0.002) and negatively with CD4 count (r = -0.186, p < 0.0001). Area under the curve for galectin-9/CD4 count ratio for identifying viremic individuals was 0.906. Sensitivity and specificity of the ratio at a cutoff of 14.47 were 90.13% and 70.05%, respectively, for detecting viremic individuals. Further, galectin-9 levels correlated with cystatin C (r = 0.239, p = 0.0183), IL-18 (r = 0.311, p = 0.006), and systolic blood pressure (r = 0.220, p = 0.0355). Galectin-9-induced HIV reactivation was significantly lower in individuals on long-term ART than those on short-term ART.

CONCLUSION

The galectin-9-to-CD4 count ratio indicated the potential of galectin-9 as a cheaper monitoring tool to detect HIV viremia. Strategies for countering the effects of galectin-9 for controlling HIV viremia and non-AIDS events are urgently warranted.

Human galectin-9 promotes the expansion of HIV reservoirs in vivo in humanized mice

OBJECTIVE

The human endogenous protein galectin-9 (Gal-9) reactivates latently HIV-infected cells in vitro and ex vivo , which may allow for immune-mediated clearance of these cells. However, Gal-9 also activates several immune cells, which could negatively affect HIV persistence by promoting chronic activation/exhaustion. This potential 'double-edged sword' effect of Gal-9 raises the question of the overall impact of Gal-9 on HIV persistence in vivo .

DESIGN

We used the BLT (bone marrow, liver, thymus) humanized mouse model to evaluate the impact of Gal-9 on HIV persistence in vivo during antiretroviral therapy (ART).

METHODS

Two independent cohorts of ART-suppressed HIV-infected BLT mice were treated with either recombinant Gal-9 or phosphate-buffered saline control. Plasma viral loads and levels of tissue-associated HIV DNA and RNA were measured by qPCR. Immunohistochemistry and HIV RNAscope were used to quantify CD4 + T, myeloid, and HIV RNA+ cells in tissues. T cell activation and exhaustion were measured by flow cytometry, and plasma markers of inflammation were measured by multiplex cytokine arrays.

RESULTS

Gal-9 did not induce plasma markers of inflammation or T cell markers of activation/exhaustion in vivo . However, the treatment significantly increased levels of tissue-associated HIV DNA and RNA compared to controls ( P  = 0.0007 and P  = 0.011, respectively, for cohort I and P  = 0.002 and P  = 0.005, respectively, for cohort II). RNAscope validated the Gal-9 mediated induction of HIV RNA in tissue-associated myeloid cells, but not T cells.

CONCLUSIONS

Our study highlights the overall adverse effects of Gal-9 on HIV persistence and the potential need to block Gal-9 interactions during ART-suppressed HIV infection.

Strategies to overcome HIV drug resistance-current and future perspectives

The availability of combined antiretroviral therapy (cART) has revolutionized the course of HIV infection, suppressing HIV viremia, restoring the immune system, and improving the quality of life of HIV infected patients. However, the emergence of drug resistant and multidrug resistant strains remains an important contributor to cART failure, associated with a higher risk of HIV-disease progression and mortality. According to the latest WHO HIV Drug Resistance Report, the prevalence of acquired and transmitted HIV drug resistance in ART naive individuals has exponentially increased in the recent years, being an important obstacle in ending HIV-1 epidemic as a public health threat by 2030. The prevalence of three and four-class resistance is estimated to range from 5 to 10% in Europe and less than 3% in North America. The new drug development strategies are focused on improved safety and resistance profile within the existing antiretroviral classes, discovery of drugs with novel mechanisms of action (e.g., attachment/post-attachment inhibitors, capsid inhibitors, maturation inhibitors, nucleoside reverse transcriptase translocation inhibitors), combination therapies with improved adherence, and treatment simplification with infrequent dosing. This review highlight the current progress in the management of salvage therapy for patients with multidrug-resistant HIV-1 infection, discussing the recently approved and under development antiretroviral agents, as well as the new drug targets that are providing a new avenue for the development of therapeutic interventions in HIV infection.

Both N- and C-terminal domains of galectin-9 are capable of inducing HIV reactivation despite mediating differential immunomodulatory functionalities

Background

The shock-and-kill strategy for HIV cure requires the reactivation of latent HIV followed by the killing of the reactivated cellular reservoir. Galectin-9, an immunomodulatory protein, is shown to induce HIV reactivation as well as contribute to non-AIDS- and AIDS-defining events. The protein is prone to cleavage by inflammatory proteases at its linker region separating the N- and C-terminal carbohydrate-binding domains (N- and C-CRDs) which differ in their binding specificities. It is important to study the activity of its cleaved as well as uncleaved forms in mediating HIV reactivation and immunomodulation in order to understand their role in HIV pathogenesis and their further utilization for the shock-and-kill strategy.

Methodology

The PBMCs of HIV patients on virally suppressive ART (n = 11) were stimulated using 350 nM of the full-length protein and N- and C-CRDs of Gal-9. HIV reactivation was determined by analyzing gag RNA copies using qPCR using isolated CD4 cells and intracellular P24 staining of PBMCs by flow cytometry. Cytokine responses induced by the full-length protein and N- and C-CRDs of Gal-9 were also assessed by flow cytometry, Luminex, and gene expression assays. Changes in T helper cell gene expression pattern after the stimulation were also determined by real-time PCR array.

Results

Both N- and C-CRDs of galectin-9 induced HIV reactivation in addition to the full-length galectin-9 protein. The two domains elicited higher cytokine responses than the full-length protein, possibly capable of mediating higher perturbations in the immune system if used for HIV reactivation. N-CRD was found to induce the development of Treg cells, whereas C-CRD inhibited the induction of Treg cells. Despite this, both domains elicited IL-10 secretory response although targeting different CD4 cell phenotypes.

Conclusion

N- and C-CRDs were found to induce HIV reactivation similar to that of the full-length protein, indicating their possible usefulness in the shock-and-kill strategy. The study indicated an anti-inflammatory role of N-CRD versus the proinflammatory properties of C-CRD of galectin-9 in HIV infection.

Transcriptome profiles of latently- and reactivated HIV-1 infected primary CD4+ T cells: A pooled data-analysis

The main obstacle to cure HIV-1 is the latent reservoir. Antiretroviral therapy effectively controls viral replication, however, it does not eradicate the latent reservoir. Latent CD4⁺ T cells are extremely rare in HIV-1 infected patients, making primary CD4⁺ T cell models of HIV-1 latency key to understanding latency and thus finding a cure. In recent years several primary CD4⁺ T cell models of HIV-1 latency were developed to study the underlying mechanism of establishing, maintaining and reversing HIV-1 latency. In the search of biomarkers, primary CD4⁺ T cell models of HIV-1 latency were used for bulk and single-cell transcriptomics. A wealth of information was generated from transcriptome analyses of different primary CD4⁺ T cell models of HIV-1 latency using latently- and reactivated HIV-1 infected primary CD4⁺ T cells. Here, we performed a pooled data-analysis comparing the transcriptome profiles of latently- and reactivated HIV-1 infected cells of 5 in vitro primary CD4⁺ T cell models of HIV-1 latency and 2 ex vivo studies of reactivated HIV-1 infected primary CD4⁺ T cells from HIV-1 infected individuals. Identifying genes that are differentially expressed between latently- and reactivated HIV-1 infected primary CD4⁺ T cells could be a more successful strategy to better understand and characterize HIV-1 latency and reactivation. We observed that natural ligands and coreceptors were predominantly downregulated in latently HIV-1 infected primary CD4⁺ T cells, whereas genes associated with apoptosis, cell cycle and HLA class II were upregulated in reactivated HIV-1 infected primary CD4⁺ T cells. In addition, we observed 5 differentially expressed genes that co-occurred in latently- and reactivated HIV-1 infected primary CD4⁺ T cells, one of which, MSRB2, was found to be differentially expressed between latently- and reactivated HIV-1 infected cells. Investigation of primary CD4⁺ T cell models of HIV-1 latency that mimic the in vivo state remains essential for the study of HIV-1 latency and thus providing the opportunity to compare the transcriptome profile of latently- and reactivated HIV-1 infected cells to gain insights into differentially expressed genes, which might contribute to HIV-1 latency.

A Dynamic Interplay of Circulating Extracellular Vesicles and Galectin-1 Reprograms Viral Latency during HIV-1 Infection

Combined Antiretroviral therapy (cART) suppresses HIV replication but fails to eradicate the virus, which persists in a small pool of long-lived latently infected cells. Immune activation and residual inflammation during cART are considered to contribute to viral persistence. Galectins, a family of β-galactoside-binding proteins, play central roles in host-pathogen interactions and inflammatory responses. Depending on their structure, glycan binding specificities and/or formation of distinct multivalent signaling complexes, different members of this family can complement, synergize, or oppose the function of others. Here, we identify a regulatory circuit, mediated by galectin-1 (Gal-1)–glycan interactions, that promotes reversal of HIV-1 latency in infected T cells. We found elevated levels of circulating Gal-1 in plasma from HIV-1-infected individuals, which correlated both with inflammatory markers and the transcriptional activity of the reservoir, as determined by unspliced-RNA (US-RNA) copy number. Proinflammatory extracellular vesicles (EVs) isolated from the plasma of HIV-infected individuals induced Gal-1 secretion by macrophages. Extracellularly, Gal-1 interacted with latently infected resting primary CD4⁺ T cells and J-LAT cells in a glycan-dependent manner and reversed HIV latency via activation of the nuclear factor κB (NF-κB). Furthermore, CD4⁺ T cells isolated from HIV-infected individuals showed increased HIV-1 transcriptional activity when exposed to Gal-1. Thus, by modulating reservoir dynamics, EV-driven Gal-1 secretion by macrophages links inflammation with HIV-1 persistence in cART-treated individuals.

HIV cure strategies: which ones are appropriate for Africa?

Although combination antiretroviral therapy (ART) has reduced mortality and improved lifespan for people living with HIV, it does not provide a cure. Patients must be on ART for the rest of their lives and contend with side effects, unsustainable costs, and the development of drug resistance. A cure for HIV is, therefore, warranted to avoid the limitations of the current therapy and restore full health. However, this cure is difficult to find due to the persistence of latently infected HIV cellular reservoirs during suppressive ART. Approaches to HIV cure being investigated include boosting the host immune system, genetic approaches to disable co-receptors and the viral genome, purging cells harboring latent HIV with latency-reversing latency agents (LRAs) (shock and kill), intensifying ART as a cure, preventing replication of latent proviruses (block and lock) and boosting T cell turnover to reduce HIV-1 reservoirs (rinse and replace). Since most people living with HIV are in Africa, methods being developed for a cure must be amenable to clinical trials and deployment on the continent. This review discusses the current approaches to HIV cure and comments on their appropriateness for Africa.

Galectin-3 facilitates cell-to-cell HIV-1 transmission by altering the composition of membrane lipid rafts in CD4 T cells

Galectin-3 (GAL3) is a β-galactoside-binding lectin expressed in CD4 T cells infected with human immunodeficiency virus-1 (HIV-1). GAL3 promotes HIV-1 budding by associating with ALIX and Gag p6. GAL3 has been shown to localize in membrane lipid rafts in dendritic cells and positively regulate cell migration. HIV-1 spreads between T cells by forming supramolecular structures (virological synapses [VSs]), whose integrity depends on lipid rafts. Here, we addressed the potential role of GAL3 in cell-to-cell transmission of HIV-1 in CD4 T cells. GAL3 expressed in donor cells was more important for facilitating HIV-1 cell-to-cell transfer than GAL3 expressed in target cells. GAL3 was found to be co-transferred with Gag from HIV-1-positive donor to HIV-1-negative target T cells. HIV-1 infection induced translocation of GAL3 together with Gag to the cell-cell interfaces and colocalize with GM1, where GAL3 facilitated VS formation. GAL3 regulated the coordinated transfer of Gag and flotillin-1 into plasma membrane fractions. Finally, depletion of GAL3 reduced the cholesterol levels in membrane lipid rafts in CD4 T cells. These findings provide evidence that endogenous GAL3 stimulates lipid raft components and facilitates intercellular HIV-1 transfer among CD4 T cells, offering another pathway by which GAL3 regulates HIV-1 infection. These findings may inform the treatment of HIV-1 infection based on targeting GAL3 to modulate lipid rafts.

Human Galectin-9 Potently Enhances SARS-CoV-2 Replication and Inflammation in Airway Epithelial Cells

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has caused a global economic and health crisis. Recently, plasma levels of galectin-9 (Gal-9), a β-galactoside-binding lectin involved in immune regulation and viral immunopathogenesis, were reported to be elevated in the setting of severe COVID-19 disease. However, the impact of Gal-9 on SARS-CoV-2 infection and immunopathology remained to be elucidated. Here, we demonstrate that Gal-9 treatment potently enhances SARS-CoV-2 replication in human airway epithelial cells (AECs), including primary AECs in air-liquid interface (ALI) culture. Gal-9-glycan interactions promote SARS-CoV-2 attachment and entry into AECs in an ACE2-dependent manner, enhancing the binding affinity of the viral spike protein to ACE2. Transcriptomic analysis revealed that Gal-9 and SARS-CoV-2 infection synergistically induce the expression of key pro-inflammatory programs in AECs including the IL-6, IL-8, IL-17, EIF2, and TNFα signaling pathways. Our findings suggest that manipulation of Gal-9 should be explored as a therapeutic strategy for SARS-CoV-2 infection.

Importance

COVID-19 continues to have a major global health and economic impact. Identifying host molecular determinants that modulate SARS-CoV-2 infectivity and pathology is a key step in discovering novel therapeutic approaches for COVID-19. Several recent studies have revealed that plasma concentrations of the human β-galactoside-binding protein galectin-9 (Gal-9) are highly elevated in COVID-19 patients. In this study, we investigated the impact of Gal-9 on SARS-CoV-2 pathogenesis ex vivo in airway epithelial cells (AECs), the critical initial targets of SARS-CoV-2 infection. Our findings reveal that Gal-9 potently enhances SARS-CoV-2 replication in AECs, interacting with glycans to enhance the binding between viral particles and entry receptors on the target cell surface. Moreover, we determined that Gal-9 accelerates and exacerbates several virus-induced pro-inflammatory programs in AECs that are established signature characteristics of COVID-19 disease and SARS-CoV-2-induced acute respiratory distress syndrome (ARDS). Our findings suggest that Gal-9 is a promising pharmacological target for COVID-19 therapies.

ISG15 deficiency restricts HIV-1 infection

Type I interferons (IFN-Is) are a group of potent inflammatory and antiviral cytokines. They induce IFN stimulated genes (ISGs), which act as proinflammatory mediators, antiviral effectors, and negative regulators of the IFN-I signaling cascade itself. One such regulator is interferon stimulated gene 15 (ISG15). Humans with complete ISG15 deficiency express persistently elevated levels of ISGs, and consequently, exhibit broad spectrum resistance to viral infection. Here, we demonstrate that IFN-I primed fibroblasts derived from ISG15-deficient individuals are more resistant to infection with single-cycle HIV-1 compared to healthy control fibroblasts. Complementation with both wild-type (WT) ISG15 and ISG15ΔGG (incapable of ISGylation while retaining negative regulation activity) was sufficient to reverse this phenotype, restoring susceptibility to infection to levels comparable to WT cells. Furthermore, CRISPR-edited ISG15^ko primary CD4⁺ T cells were less susceptible to HIV-1 infection compared to cells treated with non-targeting controls. Transcriptome analysis of these CRISPR-edited ISG15^ko primary CD4⁺ T cells recapitulated the ISG signatures of ISG15 deficient patients. Taken together, we document that the increased broad-spectrum viral resistance in ISG15-deficiency also extends to HIV-1 and is driven by a combination of T-cell-specific ISGs, with both known and unknown functions, predicted to target HIV-1 replication at multiple steps.

Type I interferons (IFN-Is) are a group of potent inflammatory and antiviral agents. They induce IFN stimulated genes (ISGs), which perform downstream functions to resolve viral infection, mediate the inflammatory response, as well as negatively regulate the IFN-I signaling cascade to prevent hyperinflammation. One such negative regulator is interferon stimulated gene 15 (ISG15). Humans that lack ISG15 have chronic, low levels of antiviral ISGs, and ensuing broad-spectrum resistance to viral infection. We demonstrate that IFN-I priming of ISG15-deficient cells leads to superior resistance to human immunodeficiency virus 1 (HIV-1) infection compared to IFN-I primed healthy control cells. This is true for fibroblast cell lines, as well as primary CD4+ T cells, the main target of HIV-1. Analysis of the gene expression profiles show that ISG15-knockout CD4⁺ T cells express similar inflammatory markers as ISG15-deficient patients. Overall, we show that the broad-spectrum viral resistance in ISG15-deficiency extends to HIV-1.

HIV-1 and methamphetamine alter galectins -1, -3, and -9 in human monocyte-derived macrophages

Macrophages are key elements of the innate immune system. Their HIV-1 infection is a complex process that involves multiple interacting factors and various steps and is further altered by exposure of infected cells to methamphetamine (Meth), a common drug of abuse in people living with HIV. This is reflected by dynamic changes in the intracellular and secreted proteomes of these cells. Quantification of these changes poses a challenge for experimental design and associated analytics. In this study, we measured the effect of Meth on expression of intracellular and secreted galectins-1, -3, and -9 in HIV-1 infected human monocyte-derived macrophages (hMDM) using SWATH-MS, which was further followed by MRM targeted mass spectrometry validation. Cells were exposed to Meth either prior to or after infection. Our results are the first to perform comprehensive quantifications of galectins in primary hMDM cells during HIV-1 infection and Meth exposure a building foundation for future studies on the molecular mechanisms underlying cellular pathology of hMDM resulting from viral infection and a drug of abuse—Meth.

Galectins as potential therapeutic targets in STIs in the female genital tract

Every day, more than one million people worldwide acquire a sexually transmitted infection (STI). This public health problem has a direct effect on women's reproductive and sexual health as STIs can cause irreversible damage to fertility and can have negative consequences associated with discrimination and social exclusion. Infection with one sexually transmitted pathogen predisposes to co-infection with others, suggesting the existence of shared pathways that serve as molecular links between these diseases. Galectins, a family of β-galactoside-binding proteins, have emerged as endogenous mediators that facilitate cell-surface binding, internalization and cell invasion of many sexually transmitted pathogens, including Chlamydia trachomatis, Neisseria gonorrhoeae, Trichomonas vaginalis, Candida albicans, HIV and herpes simplex virus. The ability of certain galectins to dimerize or form multimeric complexes confers the capacity to interact simultaneously with glycosylated ligands on both the pathogen and the cervico-vaginal tissue on these proteins. Galectins can act as a bridge by engaging glycans from the pathogen surface and glycosylated receptors from host cells, which is a mechanism that has been shown to be shared by several sexually transmitted pathogens. In the case of viruses and obligate intracellular bacteria, binding to the cell surface promotes pathogen internalization and cell invasion. Inflammatory responses that occur in cervico-vaginal tissue might trigger secretion of galectins, which in turn control the establishment, evolution and severity of STIs. Thus, galectin-targeted therapies could potentially prevent or decrease STIs caused by a diverse array of pathogenic microorganisms; furthermore, anti-galectin agents might reduce treatment costs of STIs and reach the most vulnerable populations.

Examining the Impact of Galectin-9 on Latent HIV Transcription

The β-galactoside-binding protein Galectin-9 (Gal-9) functions as a double-edged sword during HIV infection. On the one hand, Gal-9 can reactivate HIV latently infected cells, the main barrier to achieving HIV eradication, making them visible to immune clearance. On the other hand, Gal-9 induces latent HIV transcription by activating T cell Receptor (TCR) signaling pathways. These signaling pathways induce undesirable pro-inflammatory responses. While these unwanted responses can be mitigated by rapamycin without impacting Gal-9-mediated latent HIV reactivation, this effect raises the concern that Gal-9 may play a role in the chronic immune activation/inflammation that persists in people living with HIV despite antiretroviral therapy. Together, these data highlight the need to understand the positive and negative impacts of galectin interactions on immunological functions during HIV infection. In this chapter, we describe methods that can be used to investigate the effects of galectins, in particular Gal-9, on latent HIV transcription in vitro and ex vivo.

Plasma galectin-9 as a predictor of adverse non-AIDS events in persons with chronic HIV during suppressive antiretroviral therapy

BACKGROUND

People with HIV (PWH) on antiretroviral therapy (ART) still experience an increased risk of morbidity and mortality, presumably driven by chronic inflammation, yet predictors of discrete or combinatorial outcomes remain unclear. Galectin-9 (Gal-9), a driver of both inflammatory and immunosuppressive responses, has been associated with HIV disease progression and multimorbidity.

OBJECTIVE

To determine whether plasma Gal-9 levels are associated with the occurrence of specific non-AIDS events (NAEs) in PWH initiating ART.

DESIGN

We performed a nested case-control study of PWH enrolled from 2001 to 2009 and evaluated pre-ART (66 cases, 97 controls), a year post-ART (112 cases, 211 controls), and immediately preceding an event (89 cases, 162 controls). Events included myocardial infarction/stroke, malignancy, serious bacterial infection, or death.

METHODS

Plasma Gal-9 levels were assessed by ELISA. Conditional logistic regression assessed associations with NAEs and Spearman's correlations compared Gal-9 with other previously assessed biomarkers.

RESULTS

NAEs occurred at a median of 2.8 years (1.7-4.6) after ART initiation. Higher Gal-9 levels were associated with increased risk of NAEs at year 1 and preevent [odds ratio (OR) per 1 interquartile range = 1.4-1.6; all P < 0.05], specifically myocardial infarction/stroke at year 1 (OR = 1.9; P = 0.029). Gal-9 also correlated with multiple inflammatory and immune activation predictors of NAEs (all timepoints).

CONCLUSION

Elevated Gal-9 levels are predictive of deleterious NAEs, particularly cardiovascular complications. Whether the Gal-9 pathway, potentially binding to its putative ligands, is active in the pathogenesis of these outcomes warrants further investigation to determine if targeting Gal-9 may slow or reverse the risk of NAEs.

Glycan-Lectin Interactions in Cancer and Viral Infections and How to Disrupt Them

Glycan-lectin interactions play an essential role in different cellular processes. One of their main functions is involvement in the immune response to pathogens or inflammation. However, cancer cells and viruses have adapted to avail themselves of these interactions. By displaying specific glycosylation structures, they are able to bind to lectins, thus promoting pathogenesis. While glycan-lectin interactions promote tumor progression, metastasis, and/or chemoresistance in cancer, in viral infections they are important for viral entry, release, and/or immune escape. For several years now, a growing number of investigations have been devoted to clarifying the role of glycan-lectin interactions in cancer and viral infections. Various overviews have already summarized and highlighted their findings. In this review, we consider the interactions of the lectins MGL, DC-SIGN, selectins, and galectins in both cancer and viral infections together. A possible transfer of ways to target and disrupt them might lead to new therapeutic approaches in different pathological backgrounds.

The Current Status of Latency Reversing Agents for HIV-1 Remission

Combinatory antiretroviral therapy (cART) reduces human immunodeficiency virus type 1 (HIV-1) replication but is not curative because cART interruption almost invariably leads to a rapid rebound of viremia due to the persistence of stable HIV-1-infected cellular reservoirs. These reservoirs are mainly composed of CD4⁺ T cells harboring replication-competent latent proviruses. A broadly explored approach to reduce the HIV-1 reservoir size, the shock and kill strategy, consists of reactivating HIV-1 gene expression from the latently infected cellular reservoirs (the shock), followed by killing of the virus-producing infected cells (the kill). Based on improved understanding of the multiple molecular mechanisms controlling HIV-1 latency, distinct classes of latency reversing agents (LRAs) have been studied for their efficiency to reactivate viral gene expression in in vitro and ex vivo cell models. Here, we provide an up-to-date review of these different mechanistic classes of LRAs and discuss optimizations of the shock strategy by combining several LRAs simultaneously or sequentially.

Neutrophils promote T-cell activation through the regulated release of CD44-bound Galectin-9 from the cell surface during HIV infection

The interaction of neutrophils with T cells has been the subject of debate and controversies. Previous studies have suggested that neutrophils may suppress or activate T cells. Despite these studies, the interaction between neutrophils and T cells has remained a largely unexplored field. Here, based on our RNA sequencing (RNA-seq) analysis, we found that neutrophils have differential transcriptional and functional profiling depending on the CD4 T-cell count of the HIV-infected individual. In particular, we identified that neutrophils in healthy individuals express surface Galectin-9 (Gal-9), which is down-regulated upon activation, and is consistently down-regulated in HIV-infected individuals. However, down-regulation of Gal-9 was associated with CD4 T-cell count of patients. Unstimulated neutrophils express high levels of surface Gal-9 that is bound to CD44, and, upon stimulation, neutrophils depalmitoylate CD44 and induce its movement out of the lipid raft. This process causes the release of Gal-9 from the surface of neutrophils. In addition, we found that neutrophil-derived exogenous Gal-9 binds to cell surface CD44 on T cells, which promotes LCK activation and subsequently enhances T-cell activation. Furthermore, this process was regulated by glycolysis and can be inhibited by interleukin (IL)-10. Together, our data reveal a novel mechanism of Gal-9 shedding from the surface of neutrophils. This could explain elevated plasma Gal-9 levels in HIV-infected individuals as an underlying mechanism of the well-characterized chronic immune activation in HIV infection. This study provides a novel role for the Gal-9 shedding from neutrophils. We anticipate that our results will spark renewed investigation into the role of neutrophils in T-cell activation in other acute and chronic conditions, as well as improved strategies for modulating Gal-9 shedding.

This study shows that HIV-infected individuals have different neutrophil profiles depending on their CD4 T cell count. In particular, neutrophils express high levels of surface Gal-9 but this is shed upon stimulation; this exogenous Gal-9 binds to CD44 on T cells, which promotes LCK activation and subsequently enhances T cell activation.

In pursuit of sensitivity: Lessons learned from viral nucleic acid detection and quantification on the raindance ddPCR platform

Sensitive PCR detection of viral nucleic acids plays a critical role in infectious disease research, diagnosis and monitoring. In the context of SARS-CoV-2 detection, recent reports indicate that digital PCR-based tests are significantly more sensitive than traditional qPCR tests. Numerous factors can influence digital PCR reaction sensitivity. In this review, using a model for human HIV infection and the Raindance ddPCR platform as an example, we describe technical aspects that contribute to sensitive viral signal detection in DNA and RNA from tissue samples, which often harbor viral reservoirs and serve as better predictors of disease outcome and indicators of treatment efficacy.

Blood Levels of Galectin-9, an Immuno-Regulating Molecule, Reflect the Severity for the Acute and Chronic Infectious Diseases

Galectin-9 (Gal-9) is a β-galactoside-binding lectin capable of promoting or suppressing the progression of infectious diseases. This protein is susceptible to cleavage of its linker-peptides by several proteases, and the resulting cleaved forms, N-terminal carbohydrate recognition domain (CRD) and C-terminal CRD, bind to various glycans. It has been suggested that full-length (FL)-Gal-9 and the truncated (Tr)-Gal-9s could exert different functions from one another via their different glycan-binding activities. We propose that FL-Gal-9 regulates the pathogenesis of infectious diseases, including human immunodeficiency virus (HIV) infection, HIV co-infected with opportunistic infection (HIV/OI), dengue, malaria, leptospirosis, and tuberculosis (TB). We also suggest that the blood levels of FL-Gal-9 reflect the severity of dengue, malaria, and HIV/OI, and those of Tr-Gal-9 markedly reflect the severity of HIV/OI. Recently, matrix metallopeptidase-9 (MMP-9) was suggested to be an indicator of respiratory failure from coronavirus disease 2019 (COVID-19) as well as useful for differentiating pulmonary from extrapulmonary TB. The protease cleavage of FL-Gal-9 may lead to uncontrolled hyper-immune activation, including a cytokine storm. In summary, Gal-9 has potential to reflect the disease severity for the acute and chronic infectious diseases.

Modular Approaches to Understand the Immunobiology of Human Immunodeficiency Virus Latency

Despite advances in slowing the progression of acquired immunodeficiency syndrome (AIDS), there is no viable cure for human immunodeficiency virus (HIV). The challenge toward a cure is mainly the formation and maintenance of a latent reservoir of cells that harbor the virus in both replication-competent and replication-defective states. This small niche of quiescent cells has been identified to reside primarily in quiescent and memory CD4⁺ T cells, but parameters that could reliably distinguish an infected T cell from an uninfected one, if any, are not clear. In addition, the migratory properties and specific anatomical reservoirs of latent T cells are difficult to measure at a high resolution in humans. A functional cure of HIV would require targeting this population using innovative new clinical strategies. One constraint toward the empirical development of such approaches is the absence of a native small animal model for AIDS. Since HIV does not efficiently infect murine cells, probing molecular-genetic questions involving latently infected T cells homing to deep tissue sites, interacting with stroma and persisting through different treatment regimens, is challenging. The goal of this article is to discuss how examining the dynamics of T cells in mouse models can provide a framework for effectively studying these questions, even without infecting mice with HIV. The inflammatory and cytokine milieu found in early human HIV infections are being increasingly understood as a result of clinical measurements. Mouse studies that recreate this milieu can potentially be used to subsequently map the fate of T cells activated in this context as well as their migratory routes. In essence, such a framework could allow complementary studies in mice to enhance our understanding of aspects of the biology of HIV latency. This can be the basis of a modular approach to small animal HIV modeling, amenable to preclinical curative strategy development.

Effect of the use of Galectin-9 and blockade of TIM-3 receptor in the latent cellular reservoir of HIV-1

Reactivation of latent HIV-1 is a necessary step for the purging of the viral reservoir, although it does not seem to be enough. The stimulation of HIV-1 specific cytotoxic T lymphocytes (CTL) may be just as essential for this purpose. In this study, we aimed to show the effect of galectin-9 (Gal-9), known to revert HIV-1 latency, in combination with the blockade of TIM-3, a natural receptor for Gal-9 and an exhaustion marker. We confirmed the ability of Gal-9 to reactivate latent HIV-1 in Jurkat-LAT-GFP cells, as well as in an IL-7-based cellular model. This reactivation was not mediated via the TIM-3 receptor, but rather by the recognition of the Gal-9 of a specific oligosaccharide pattern of resting memory CD4⁺ T cells' surfaces. The potency of Gal-9 in inducing transcription of latent HIV-1 was equal to or greater than that of other latency-reversing agents (LRA). Furthermore, the combination of Gal-9 with other LRA did not show synergistic effects in the reactivation of the latent virus. To evaluate the impact of TIM-3 inhibition on the CTL-response, different co-culture experiments with CD4⁺T, CD8⁺ T, and NK cells were performed. Our data showed that blocking TIM-3 was associated with control of viral replication in both in vitro and ex vivo models in cells from PLWH on antiretroviral therapy. A joint strategy of the use of Gal-9 to reactivate latent HIV-1 and the inhibition of TIM-3 to enhance the HIV-1 CTL specific-response was associated with control of the replication of the virus that was being reactivated, thus potentially contributing to the elimination of the viral reservoir. Our results place this strategy as a promising approach to be tested in future studies. Reactivation of latent-HIV-1 by Gal-9 and reinvigoration of CD8⁺ T cells by TIM-3 blockade could be used separately or in combination.ImportanceHIV-1 infection is a health problem of enormous importance that still causes significant mortality. Antiretroviral treatment (ART) has demonstrated efficacy in the control of HIV-1 replication, decreasing the morbidity and mortality of the infection, but it cannot eradicate the virus. In our work, we tested a protein, galectin-9 (Gal-9), an HIV-1 latency-reversing agent, using an in vitro cellular model of latency and in cells from people living with HIV-1 (PLWH) on antiretroviral therapy. Our results confirmed the potential role of Gal-9 as a molecule with a potent HIV-1 reactivation capacity. More importantly, using a monoclonal antibody against T cell immunoglobulin and the mucin domain-containing molecule 3 (TIM-3) receptor we were able to enhance the HIV-1 cytotoxic T lymphocytes (CTL) specific response to eliminate the CD4⁺ T cells in which the virus had been reactivated. When used together, i.e., Gal-9 and TIM-3 blockade, control of the replication of HIV-1 was observed, suggesting a decrease in the cellular reservoir.

Galectin-9 as a biomarker of disease severity

Galectin-9 (Gal-9) is a β-galactoside binding lectin known for its immunomodulatory role in various microbial infections. Gal-9 is expressed in all organ systems and localized in the nucleus, cell surface, cytoplasm and the extracellular matrix. It mediates host-pathogen interactions and regulates cell signalling via binding to its receptors. Gal-9 is involved in many physiological functions such as cell growth, differentiation, adhesion, communication and death. However, recent studies have emphasized on the elevated levels of Gal-9 in autoimmune disorders, viral infections, parasitic invasion, cancer, acute liver failure, atopic dermatitis, chronic kidney disease, type-2 diabetes, coronary artery disease, atherosclerosis and benign infertility-related gynecological disorders. In this paper we have reviewed the potential of Gal-9 as a reliable, sensitive and non-invasive biomarker of disease severity. Tracking changes in Gal-9 levels and its implementation as a biomarker in clinical practice will be an important tool to monitor disease activity and facilitate personalized treatment decisions.

Molecular Identification and mRNA Expression Profiles of Galectin-9 Gene in Red Sea Bream (Pagrus major) Infected with Pathogens

Galectin (Gal) is a member of a family of β-galactoside-binding lectin. The members of this family play important roles in the recognition of carbohydrate ligands and in various other biological processes. In this study, we identified the gene encoding Gal-9 in Pagrus major (PmGal-9) and analyzed its expression in various tissues after pathogen challenge. Alignment analysis revealed that the two galactose-binding lectin domains of the deduced protein were highly conserved among all the teleosts. Phylogenetic analysis revealed that PmGal-9 is most closely related to the Gal-9 gene of gilthead sea bream. PmGal-9 was ubiquitously expressed in all tissues analyzed but was predominantly expressed in the spleen, head kidney, and intestine. After challenges with major microbial pathogens (Edwardsiella piscicida, Streptococcus iniae, or red sea bream iridovirus) of red sea bream, PmGal-9 mRNA expression was significantly regulated in most immune-related tissues. These results suggested that PmGal-9 not only plays an important role in the immune system of red sea bream but is also a possible inflammatory marker for pathogenic diseases.

The role of galectins in virus infection - A systemic literature review

BACKGROUND

Galectins are β-Galactose binding lectins expressed in numerous cells and play multiple roles in various physiological and cellular functions. However, few information is available regarding the role of galectins in virus infections. Here, we conducted a systemic literature review to analyze the role of galectins in human virus infection.

METHODS

This study uses a systematic method to identify and select eligible articles according to the PRISMA guidelines. References were selected from PubMed, Web of Science and Google Scholar database covering publication dated from August 1995 to December 2018.

RESULTS

Results indicate that galectins play multiple roles in regulation of virus infections. Galectin-1 (Gal-1), galectin-3 (Gal-3), galectin-8 (Gal-8), and galectin-9 (Gal-9) were found as the most predominant galectins reported to participate in virus infection. The regulatory function of galectins occurs by extracellularly binding to viral glycosylated envelope proteins, interacting with ligands or receptors on immune cells, or acting intracellularly with viral or cellular components in the cytoplasm. Several galectins express either positive or negative regulatory role, while some had dual regulatory capabilities on virus propagation based on the conditions and their localization. However, limited information about the endogenous function of galectins were found. Therefore, the endogenous effects of galectins in host-virus regulation remains valuable to investigate.

CONCLUSIONS

This study offers information regarding the various roles galectins shown in viral infection and suggest that galectins can potentially be used as viral therapeutic targets or antagonists.

μ-Lat: A mouse model to evaluate human immunodeficiency virus eradication strategies

A critical barrier to the development of a human immunodeficiency virus (HIV) cure is the lack of a scalable animal model that enables robust evaluation of eradication approaches prior to testing in humans. We established a humanized mouse model of latent HIV infection by transplanting "J-Lat" cells, Jurkat cells harboring a latent HIV provirus encoding an enhanced green fluorescent protein (GFP) reporter, into irradiated adult NOD.Cg-Prkdcscid Il2rgtm1Wjl /SzJ (NSG) mice. J-Lat cells exhibited successful engraftment in several tissues including spleen, bone barrow, peripheral blood, and lung, in line with the diverse natural tissue tropism of HIV. Administration of tumor necrosis factor (TNF)-α, an established HIV latency reversal agent, significantly induced GFP expression in engrafted cells across tissues, reflecting viral reactivation. These data suggest that our murine latency ("μ-Lat") model enables efficient determination of how effectively viral eradication agents, including latency reversal agents, penetrate, and function in diverse anatomical sites harboring HIV in vivo.

Plasma Levels of a Cleaved Form of Galectin-9 Are the Most Sensitive Biomarkers of Acquired Immune Deficiency Syndrome and Tuberculosis Coinfection

Acquired immunodeficiency syndrome (AIDS) complicated with tuberculosis (TB) is a global public issue. Due to the paucity of bacteria in AIDS/TB, blood-based biomarkers that reflect disease severity are desired. Plasma levels of matricellular proteins, such as osteopontin (OPN) and galectin-9 (Gal-9), are known to be elevated in AIDS and TB. Therefore, full-length (FL)-Gal9 and FL-OPN, and their truncated forms (Tr-Gal9, Ud-OPN), and 38 cytokines/chemokines were measured in the plasma of 24 AIDS (other than TB), 49 TB, and 33 AIDS/TB patients. Receiver-operating characteristic analysis was used to screen molecules that could distinguish either between disease and normal group, among each disease group, or between deceased patients and survivors. Selected molecules were further analyzed for significant differences. Tr-Gal9 had the highest ability to differentiate TB from AIDS or AIDS/TB, while Ud-OPN distinguished multidrug resistance (MDR)-TB from non-MDR TB, and extra-pulmonary TB from pulmonary TB. Molecules significantly elevated in deceased patients included; FL-Gal9, Tr-Gal9, interleukin (IL)-1 receptor antagonist, IL-17A and transforming growth factor-α in AIDS; IL-6, granulocyte colony-stimulating factor and monocyte chemotactic protein-1 in TB; and macrophage inflammatory protein-1β in AIDS/TB. From the sensitivity, specificity, and significant elevation, Tr-Gal9 is the best biomarker of inflammation and severity in AIDS and AIDS/TB.

Mining for humoral correlates of HIV control and latent reservoir size

While antiretroviral therapy (ART) has effectively revolutionized HIV care, the virus is never fully eliminated. Instead, immune dysfunction, driven by persistent non-specific immune activation, ensues and progressively leads to premature immunologic aging. Current biomarkers monitoring immunologic changes encompass generic inflammatory biomarkers, that may also change with other infections or disease states, precluding the antigen-specific monitoring of HIV-infection associated changes in disease. Given our growing appreciation of the significant changes in qualitative and quantitative properties of disease-specific antibodies in HIV infection, we used a systems approach to explore humoral profiles associated with HIV control. We found that HIV-specific antibody profiles diverge by spontaneous control of HIV, treatment status, viral load and reservoir size. Specifically, HIV-specific antibody profiles representative of changes in viral load were largely quantitative, reflected by differential HIV-specific antibody levels and Fc-receptor binding. Conversely, HIV-specific antibody features that tracked with reservoir size exhibited a combination of quantitative and qualitative changes marked by more distinct subclass selection profiles and unique HIV-specific Fc-glycans. Our analyses suggest that HIV-specific antibody Fc-profiles provide antigen-specific resolution on both cell free and cell-associated viral loads, pointing to potentially novel biomarkers to monitor reservoir activity.

Current combination antiretroviral therapy (ART) regimens have reversed the death sentence once associated with an HIV diagnosis. However, the virus is never fully eliminated. Rather, latently infected cells with integrated virus (latent reservoir) persist and the virus rebounds rapidly upon discontinuation of therapy. Further, even for those on ART, immune dysfunction, driven by persistent non-specific immune activation, ensues and progressively leads to premature immunologic aging. Current biomarkers monitoring these changes are non-specific–they focus on generic inflammatory changes that may also track with other infections or disease states. In this manuscript, we used an unbiased analytical systems approach to identify antigen-specific biomarkers of HIV disease state/treatment status, active viremia and the latent reservoir. By virtue of them being antigen-specific, these are robust context-specific biomarkers of HIV disease progression, viremia and reservoir size. Our framework highlights the strength of using systems approaches in identifying humoral biomarkers, and can be used in other contexts to identify antigen-specific correlates of infectious disease outcome.

The African natural product knipholone anthrone and its analogue anthralin (dithranol) enhance HIV-1 latency reversal

A sterilizing or functional cure for HIV is currently precluded by resting CD4⁺ T cells that harbor latent but replication-competent provirus. The "shock-and-kill" pharmacological ap-proach aims to reactivate provirus expression in the presence of antiretroviral therapy and target virus-expressing cells for elimination. However, no latency reversal agent (LRA) to date effectively clears viral reservoirs in humans, suggesting a need for new LRAs and LRA combinations. Here, we screened 216 compounds from the pan-African Natural Product Library and identified knipholone anthrone (KA) and its basic building block anthralin (dithranol) as novel LRAs that reverse viral latency at low micromolar concentrations in multiple cell lines. Neither agent's activity depends on protein kinase C; nor do they inhibit class I/II histone deacetylases. However, they are differentially modulated by oxidative stress and metal ions and induce distinct patterns of global gene expression from established LRAs. When applied in combination, both KA and anthralin synergize with LRAs representing multiple functional classes. Finally, KA induces both HIV RNA and protein in primary cells from HIV-infected donors. Taken together, we describe two novel LRAs that enhance the activities of multiple "shock-and-kill" agents, which in turn may inform ongoing LRA combination therapy efforts.

Possible role of plasma Galectin-9 levels as a surrogate marker of viremia in HIV infected patients on antiretroviral therapy in resource-limited settings

Background

Early detection of viremia in HIV infected patients on anti-retroviral therapy (ART) is important to prevent disease progression as well as accumulation of drug resistance mutations. This makes HIV viral load (VL) monitoring indispensable in HIV infected patients on ART. However VL, being an expensive test, results in heavy financial burden on health services. Hence, cheaper surrogate markers of viremia are desired to reduce overall cost of management of HIV infected patients.

Methods

We enrolled aviremic (n = 63, M:F = 31:32) and viremic (n = 43, M:F = 21:22) HIV infected patients at 1 year after ART initiation. Viremic individuals were identified as those having a plasma VL of more than 1000 copies/µl and aviremic individuals as less than 40 copies/µl. The study participants also included immuno-virologically discordant patients as they demonstrate differential degrees of immune-reconstitution and are likely to harbour concomitant infections influencing levels of immune-activation markers screened as the surrogate markers. Immune activation markers viz. plasma hs-CRP, soluble-CD14 and Galectin-9 levels were estimated by ELISA, IL-6 by luminex assay and percentages of CD38+ CD8+ cells were determined by flow cytometry. The levels were compared between viremic and aviremic patients and correlated with plasma viral load. Receiver operated curve (ROC) analysis was done for plasma Galectin-9 levels.

Results

Viremic patients had significantly higher levels of Galectin-9 and %CD38+ CD8+ cells (p values < 0.0001) than aviremic patients. Levels of the other activation markers did not differ between viremic and aviremic individuals. Galectin-9 levels (r = 0.76) and %CD38+ CD8+ cells (r = 0.39) correlated positively with VL. Area under curve for Galectin-9 levels for distinguishing between viremic and aviremic individuals was 0.98. Youden index, sensitivity, specificity, positive predictive value and negative predictive value for Galectin-9 levels were 0.87, 0.97, 0.90, 0.87 and 0.98, respectively, at the cut-off value of 5.79 ng/ml.

Conclusions

Plasma Galectin-9 levels could identify viremic individuals with sensitivity and specificity of more than 90%. Thus, they showed a potential to serve as a surrogate marker of viremia in HIV infected patients on ART and would have cost implications on HIV management especially in resource-limited settings. However, the findings need to be confirmed in the patients on ART for different durations of time.

Associations Between Plasma Immunomodulatory and Inflammatory Mediators With VACS Index Scores Among Older HIV-Infected Adults on Antiretroviral Therapy

The prevalence of age-related comorbidities is increased in people living with HIV, even in those well-controlled on combination antiretroviral therapy (ART). Persistent immune activation and inflammation may play pivotal roles in the pathogenesis; however, the burden of morbidities in the older HIV infected population may be exacerbated and driven by distinct mechanisms. In a cross sectional study of 45 HIV-infected participants 60 years or older, we examined the relationships between 14 immunomodulatory and inflammatory factors and the Veterans Aging Cohort Study (VACS) Index, a metric of multimorbidity and mortality comprised of age, CD4 count, hemoglobin, Fibrosis-4 [FIB-4], and estimated glomerular filtration rate [eGFR], by linear regression analysis. All participants were virally suppressed (<50 HIV RNA copies/mL), on ART, and primarily Caucasian (86.7%), and male (91.1%). Plasma levels of monocyte/macrophage-associated (neopterin, IP-10, sCD163, sCD14, and MCP-1) and glycan-binding immunomodulatory factors (galectin (Gal)-1, Gal-3, and Gal-9) were assessed, as well as inflammatory biomarkers previously linked to the VACS Index (i.e., CRP, cystatin C, TNF-α, TNFRI, IL-6, and D-dimer) for comparison. In regression analysis, higher VACS index scores were associated with higher levels of neopterin, cystatin C, TNFRI, and Gal-9 (all p < 0.05), potentially driven by correlations found with individual VACS components, including age, CD4 count, FIB-4, and eGFR. Gal-9, cystatin C, and TNFRI directly correlated with the extent of multimorbidity. Multiple correlations among markers were observed, suggesting an interplay of overlapping, but distinct, pathways. Collectively, in addition to cystatin C and TNFRI, both galectin-9 and neopterin, independently emerged as novel fluid markers of the VACS Index and burden of comorbidity and may further guide in understanding pathogenic mechanisms of age-related disorders in older HIV-infected individuals on suppressive ART.

Mycobacterium tuberculosis Reactivates HIV-1 via Exosome-Mediated Resetting of Cellular Redox Potential and Bioenergetics

The synergy between Mycobacterium tuberculosis and human immunodeficiency virus-1 (HIV-1) interferes with therapy and facilitates the pathogenesis of both human pathogens. Fundamental mechanisms by which M. tuberculosis exacerbates HIV-1 infection are not clear. Here, we show that exosomes secreted by macrophages infected with M. tuberculosis, including drug-resistant clinical strains, reactivated HIV-1 by inducing oxidative stress. Mechanistically, M. tuberculosis-specific exosomes realigned mitochondrial and nonmitochondrial oxygen consumption rates (OCR) and modulated the expression of host genes mediating oxidative stress response, inflammation, and HIV-1 transactivation. Proteomics analyses revealed the enrichment of several host factors (e.g., HIF-1α, galectins, and Hsp90) known to promote HIV-1 reactivation in M. tuberculosis-specific exosomes. Treatment with a known antioxidant-N-acetyl cysteine (NAC)-or with inhibitors of host factors-galectins and Hsp90-attenuated HIV-1 reactivation by M. tuberculosis -specific exosomes. Our findings uncover new paradigms for understanding the redox and bioenergetics bases of HIV-M. tuberculosis coinfection, which will enable the design of effective therapeutic strategies.IMPORTANCE Globally, individuals coinfected with the AIDS virus (HIV-1) and with M. tuberculosis (causative agent of tuberculosis [TB]) pose major obstacles in the clinical management of both diseases. At the heart of this issue is the apparent synergy between the two human pathogens. On the one hand, mechanisms induced by HIV-1 for reactivation of TB in AIDS patients are well characterized. On the other hand, while clinical findings clearly identified TB as a risk factor for HIV-1 reactivation and associated mortality, basic mechanisms by which M. tuberculosis exacerbates HIV-1 replication and infection remain poorly characterized. The significance of our research is in identifying the role of fundamental mechanisms such as redox and energy metabolism in catalyzing HIV-M. tuberculosis synergy. The quantification of redox and respiratory parameters affected by M. tuberculosis in stimulating HIV-1 will greatly enhance our understanding of HIV-M. tuberculosis coinfection, leading to a wider impact on the biomedical research community and creating new translational opportunities.

Current Status of Latency Reversing Agents Facing the Heterogeneity of HIV-1 Cellular and Tissue Reservoirs

One of the most explored therapeutic approaches aimed at eradicating HIV-1 reservoirs is the "shock and kill" strategy which is based on HIV-1 reactivation in latently-infected cells ("shock" phase) while maintaining antiretroviral therapy (ART) in order to prevent spreading of the infection by the neosynthesized virus. This kind of strategy allows for the "kill" phase, during which latently-infected cells die from viral cytopathic effects or from host cytolytic effector mechanisms following viral reactivation. Several latency reversing agents (LRAs) with distinct mechanistic classes have been characterized to reactivate HIV-1 viral gene expression. Some LRAs have been tested in terms of their potential to purge latent HIV-1 in vivo in clinical trials, showing that reversing HIV-1 latency is possible. However, LRAs alone have failed to reduce the size of the viral reservoirs. Together with the inability of the immune system to clear the LRA-activated reservoirs and the lack of specificity of these LRAs, the heterogeneity of the reservoirs largely contributes to the limited success of clinical trials using LRAs. Indeed, HIV-1 latency is established in numerous cell types that are characterized by distinct phenotypes and metabolic properties, and these are influenced by patient history. Hence, the silencing mechanisms of HIV-1 gene expression in these cellular and tissue reservoirs need to be better understood to rationally improve this cure strategy and hopefully reach clinical success.

Type 1-programmed dendritic cells drive antigen-specific latency reversal and immune elimination of persistent HIV-1

Background

Despite the success of antiretroviral therapy (ART), latent HIV-1 continues to persist in a long-lived population of resting memory CD4⁺ T cells within those who are infected. Finding a safe and effective means to induce latency reversal (LR) during ART to specifically expose this latent HIV-1 cellular reservoir for immune elimination has been a major barrier to a functional cure.

Methods

In this study, we test the use of antigen-presenting type 1-polarized, monocyte-derived dendritic cells (MDC1) generated from chronic HIV-1-infected individuals on ART as a means to induce HIV-1 latency reversal in autologous CD4⁺ T cells harboring replication-competent provirus. We use the same MDC1 for ex-vivo generation of autologous HIV-1 antigen-specific CD8⁺ cytotoxic T cells (CTL) and test their effector responses against the MDC1-exposed HIV-1- infected CD4⁺ T cell targets.

Findings

MDC1 presentation of either HIV-1 or cytomegalovirus (CMV) antigens to CD4⁺ T cells facilitated HIV-1 LR. This antigen-driven MDC1-mediated LR was sharply diminished with blockade of the CD40L/CD40 ‘helper’ signaling pathway. Importantly, these antigen-presenting MDC1 also activated the expansion of CTL capable of killing the exposed HIV-1-infected targets.

Interpretation

Inclusion of virus-associated MHC class II ‘helper’ antigens in MDC1-based HIV-1 immunotherapies could serve both as a targeted means to safely unmask antigen-specific CD4⁺ T cells harboring HIV-1, and to support CTL responses that can effectively target the MDC1-exposed HIV-1 cellular reservoir as a functional cure strategy.

Fund

This study was supported by the NIH-NAID grants R21-AI131763, U01-AI35041, UM1-AI126603, and T32-AI065380.

Breaking the Glyco-Code of HIV Persistence and Immunopathogenesis

PURPOSE OF REVIEW

Glycoimmunology is an emerging field focused on understanding how immune responses are mediated by glycans (carbohydrates) and their interaction with glycan-binding proteins called lectins. How glycans influence immunological functions is increasingly well understood. In a parallel way, in the HIV field, it is increasingly understood how the host immune system controls HIV persistence and immunopathogenesis. However, what has mostly been overlooked, despite its potential for therapeutic applications, is the role that the host glycosylation machinery plays in modulating the persistence and immunopathogenesis of HIV. Here, we will survey four areas in which the links between glycan-lectin interactions and immunology and between immunology and HIV are well described. For each area, we will describe these links and then delineate the opportunities for the HIV field in investigating potential interactions between glycoimmunology and HIV persistence/immunopathogenesis.

RECENT FINDINGS

Recent studies show that the human glycome (the repertoire of human glycan structures) plays critical roles in driving or modulating several cellular processes and immunological functions that are central to maintaining HIV infection. Understanding the links between glycoimmunology and HIV infection may create a new paradigm for discovering novel glycan-based therapies that can lead to eradication, functional cure, or improved tolerance of lifelong infection.

HIV "shock and kill" therapy: In need of revision

The implementation of antiretroviral therapy 23 years ago has rendered HIV infection clinically manageable. However, the disease remains incurable, since it establishes latent proviral reservoirs, which in turn can stochastically begin reproducing viral particles throughout the patient's lifetime. Viral latency itself depends in large part on the silencing environment of the infected host cell, which can be chemically manipulated. "Shock and kill" therapy intends to reverse proviral quiescence by inducing transcription with pharmaceuticals and allowing a combination of antiretroviral therapy, host immune clearance and HIV-cytolysis to remove latently infected cells, leading to a complete cure. Over 160 compounds functioning as latency-reversing agents (LRAs) have been identified to date, but none of the candidates has yet led to a promising functional cure. Furthermore, fundamental bioinformatic and clinical research from the past decade has highlighted the complexity and highly heterogeneous nature of the proviral reservoirs, shedding doubt on the "shock and kill" concept. Alternative therapies such as the HIV transcription-inhibiting "block and lock" strategy are therefore being considered. In this review we describe the variety of existing classes of LRAs, discuss their current drawbacks and highlight the potential for combinatorial "shocktail" therapies for potent proviral reactivation. We also suggest investigating LRAs with lesser-known mechanisms of action, and examine the feasibility of "block and lock" therapy.

Galectin-9 Mediates HIV Transcription by Inducing TCR-Dependent ERK Signaling

Endogenous plasma levels of the immunomodulatory carbohydrate-binding protein galectin-9 (Gal-9) are elevated during HIV infection and remain elevated after antiretroviral therapy (ART) suppression. We recently reported that Gal-9 regulates HIV transcription and potently reactivates latent HIV. However, the signaling mechanisms underlying Gal-9-mediated viral transcription remain unclear. Given that galectins are known to modulate T cell receptor (TCR)-signaling, we hypothesized that Gal-9 modulates HIV transcriptional activity, at least in part, through inducing TCR signaling pathways. Gal-9 induced T cell receptor ζ chain (CD3ζ) phosphorylation (11.2 to 32.1%; P = 0.008) in the J-Lat HIV latency model. Lck inhibition reduced Gal-9-mediated viral reactivation in the J-Lat HIV latency model (16.8-0.9%; P < 0.0001) and reduced both Gal-9-mediated CD4+ T cell activation (10.3 to 1.65% CD69 and CD25 co-expression; P = 0.0006), and IL-2/TNFα secretion (P < 0.004) in primary CD4+ T cells from HIV-infected individuals on suppressive ART. Using phospho-kinase antibody arrays, we found that Gal-9 increased the phosphorylation of the TCR-downstream signaling molecules ERK1/2 (26.7-fold) and CREB (6.6-fold). ERK and CREB inhibitors significantly reduced Gal-9-mediated viral reactivation (16.8 to 2.6 or 12.6%, respectively; P < 0.0007). Given that the immunosuppressive rapamycin uncouples HIV latency reversal from cytokine-associated toxicity, we also investigated whether rapamycin could uncouple Gal-9-mediated latency reactivation from its concurrent pro-inflammatory cytokine production. Rapamycin reduced Gal-9-mediated secretion of IL-2 (4.4-fold, P = 0.001) and TNF (4-fold, P = 0.02) without impacting viral reactivation (16.8% compared to 16.1%; P = 0.2). In conclusion, Gal-9 modulates HIV transcription by activating the TCR-downstream ERK and CREB signaling pathways in an Lck-dependent manner. Our findings could have implications for understanding the role of endogenous galectin interactions in modulating TCR signaling and maintaining chronic immune activation during ART-suppressed HIV infection. In addition, uncoupling Gal-9-mediated viral reactivation from undesirable pro-inflammatory effects, using rapamycin, may increase the potential utility of recombinant Gal-9 within the reversal of HIV latency eradication framework.

Restriction of Human Cytomegalovirus Infection by Galectin-9

Human cytomegalovirus (HCMV) is a ubiquitous human herpesvirus. While HCMV infection is generally asymptomatic in the immunocompetent, it can have devastating consequences in those with compromised or underdeveloped immune systems, including transplant recipients and neonates. Galectins are a widely expressed protein family that have been demonstrated to modulate both antiviral immunity and regulate direct host-virus interactions. The potential for galectins to directly modulate HCMV infection has not previously been studied, and our results reveal that galectin-9 (Gal-9) can potently inhibit HCMV infection. Gal-9-mediated inhibition of HCMV was dependent upon its carbohydrate recognition domains and thus dependent on glycan interactions. Temperature shift studies revealed that Gal-9 specific inhibition was mediated primarily at the level of virus-cell fusion and not binding. Additionally, we found that during reactivation of HCMV in hematopoietic stem cell transplant (HSCT) patients soluble Gal-9 is upregulated. This study provides the first evidence for Gal-9 functioning as a potent antiviral defense effector molecule against HCMV infection and identifies it as a potential clinical candidate to restrict HCMV infections.IMPORTANCE Human cytomegalovirus (HCMV) continues to cause serious and often life-threatening disease in those with impaired or underdeveloped immune systems. This virus is able to infect and replicate in a wide range of human cell types, which enables the virus to spread to other individuals in a number of settings. Current antiviral drugs are associated with a significant toxicity profile, and there is no vaccine; these factors highlight a need to identify additional targets for the development of anti-HCMV therapies. We demonstrate for the first time that secretion of a member of the galectin family of proteins, galectin-9 (Gal-9), is upregulated during natural HCMV-reactivated infection and that this soluble cellular protein possesses a potent capacity to block HCMV infection by inhibiting virus entry into the host cell. Our findings support the possibility of harnessing the antiviral properties of Gal-9 to prevent HCMV infection and disease.

Gal power: the diverse roles of galectins in regulating viral infections

Viruses, as a class of pathogenic microbe, remain a significant health burden globally. Viral infections result in significant morbidity and mortality annually and many remain in need of novel vaccine and anti-viral strategies. The development of effective novel anti-viral therapeutics, in particular, requires detailed understanding of the mechanism of viral infection, and the host response, including the innate and adaptive arms of the immune system. In recent years, the role of glycans and lectins in pathogen-host interactions has become an increasingly relevant issue. This review focuses on the interactions between a specific lectin family, galectins, and the broad range of viral infections in which they play a role. Discussed are the diverse activities that galectins play in interacting directly with virions or the cells they infect, to promote or inhibit viral infection. In addition we describe how galectin expression is regulated both transcriptionally and post-transcriptionally by viral infections. We also compare the contribution of known galectin-mediated immune modulation, across a range of innate and adaptive immune anti-viral responses, to the outcome of viral infections.

Reiterative Enrichment and Authentication of CRISPRi Targets (REACT) identifies the proteasome as a key contributor to HIV-1 latency

The establishment of HIV-1 latency gives rise to persistent chronic infection that requires life-long treatment. To reverse latency for viral eradiation, the HIV-1 Tat protein and its associated ELL2-containing Super Elongation Complexes (ELL2-SECs) are essential to activate HIV-1 transcription. Despite efforts to identify effective latency-reversing agents (LRA), avenues for exposing latent HIV-1 remain inadequate, prompting the need to identify novel LRA targets. Here, by conducting a CRISPR interference-based screen to reiteratively enrich loss-of-function genotypes that increase HIV-1 transcription in latently infected CD4⁺ T cells, we have discovered a key role of the proteasome in maintaining viral latency. Downregulating or inhibiting the proteasome promotes Tat-transactivation in cell line models. Furthermore, the FDA-approved proteasome inhibitors bortezomib and carfilzomib strongly synergize with existing LRAs to reactivate HIV-1 in CD4⁺ T cells from antiretroviral therapy-suppressed individuals without inducing cell activation or proliferation. Mechanistically, downregulating/inhibiting the proteasome elevates the levels of ELL2 and ELL2-SECs to enable Tat-transactivation, indicating the proteasome-ELL2 axis as a key regulator of HIV-1 latency and promising target for therapeutic intervention.

To cure chronic HIV-1 infection requires reversal of HIV-1 latency from latently infected CD4⁺ T cells. A key step in HIV latency reversal is the recruitment of Super Elongation Complexes (SECs) that contain ELL2 by an HIV-encoded protein, Tat, to activate proviral transcription. To identify novel drug targets, we conducted a CRISPRi-based screen to enrich the sgRNAs that increase HIV transcription in latently infected CD4⁺ T cells. Three of the six most prominent hits in our screen are proteasome subunits. We further proved that antagonizing the proteasome promotes Tat-induced HIV-1 transcription in cell line-based latency models. Furthermore, we found that two FDA-approved proteasome inhibitors strongly synergize with existing LRAs ex vivo without inducing cell activation or proliferation. We further found that antagonizing the proteasome elevates the levels of ELL2 and ELL2-containing SECs in the cells, thus enabling Tat-transactivation. These results indicate that the proteasome-ELL2 axis is a key regulator of HIV-1 latency could potentially be targeted for therapeutic interventions.

BCL6 Inhibitor-Mediated Downregulation of Phosphorylated SAMHD1 and T Cell Activation Are Associated with Decreased HIV Infection and Reactivation

Clearance of HIV-infected germinal center (GC) CD4⁺ follicular helper T cells (Tfh) after combination antiretroviral therapy (ART) is essential to an HIV cure. Blocking B cell lymphoma 6 (BCL6; the master transcription factor for Tfh cells) represses HIV infection of tonsillar CD4⁺ Tfh ex vivo, reduces GC formation, and limits immune activation in vivo We assessed the anti-HIV activity of a novel BCL6 inhibitor, FX1, in Tfh/non-Tfh CD4⁺ T cells and its impact on T cell activation and SAMHD1 phosphorylation (Thr592). FX1 repressed HIV-1 infection of peripheral CD4⁺ T cells and tonsillar Tfh/non-Tfh CD4⁺ T cells (P < 0.05) and total elongated and multispliced HIV-1 RNA production during the first round of viral life cycle (P < 0.01). Using purified circulating CD4⁺ T cells from uninfected donors, we demonstrate that FX1 treatment resulted in downregulation pSAMHD1 expression (P < 0.05) and T cell activation (HLA-DR, CD25, and Ki67; P < 0.01) ex vivo corresponding with inhibition of HIV-1 and HIV-2 replication. Ex vivo HIV-1 reactivation using purified peripheral CD4⁺ T cells from HIV-infected ART-suppressed donors was also blocked by FX1 treatment (P < 0.01). Our results indicate that BCL6 function contributes to Tfh/non-Tfh CD4⁺ T cell activation and cellular susceptibility to HIV infection. BCL6 inhibition represents a novel therapeutic strategy to potentiate HIV suppression in Tfh/non-Tfh CD4⁺ T cells without reactivation of latent virus.IMPORTANCE The expansion and accumulation of HIV-infected BCL6⁺ Tfh CD4⁺ T cells are thought to contribute to the persistence of viral reservoirs in infected subjects undergoing ART. Two mechanisms have been raised for the preferential retention of HIV within Tfh CD4⁺ T cells: (i) antiretroviral drugs have limited tissue distribution, resulting in insufficient tissue concentration and lower efficacy in controlling HIV replication in lymphoid tissues, and (ii) cytotoxic CD8⁺ T cells within lymphoid tissues express low levels of chemokine receptor (CXCR5), thus limiting their ability to enter the GCs to control/eliminate HIV-infected Tfh cells. Our results indicate that the BCL6 inhibitor FX1 can not only repress HIV infection of tonsillar Tfh ex vivo but also suppress HIV infection and reactivation in primary, non-Tfh CD4⁺ T cells. Our study provides a rationale for targeting BCL6 protein to extend ART-mediated reduction of persistent HIV and/or support strategies toward HIV remission beyond ART cessation.

Elevated cerebrospinal fluid Galectin-9 is associated with central nervous system immune activation and poor cognitive performance in older HIV-infected individuals

We previously reported that galectin-9 (Gal-9), a soluble lectin with immunomodulatory properties, is elevated in plasma during HIV infection and induces HIV transcription. The link between Gal-9 and compromised neuronal function is becoming increasingly evident; however, the association with neuroHIV remains unknown. We measured Gal-9 levels by ELISA in cerebrospinal fluid (CSF) and plasma of 70 HIV-infected (HIV+) adults stratified by age (older > 40 years and younger < 40 years) either ART suppressed or with detectable CSF HIV RNA, including a subgroup with cognitive assessments, and 18 HIV uninfected (HIV-) controls. Gal-9 tissue expression was compared in necropsy brain specimens from HIV- and HIV+ donors using gene datasets and immunohistochemistry. Among older HIV+ adults, CSF Gal-9 was elevated in the ART suppressed and CSF viremic groups compared to controls, whereas in the younger group, Gal-9 levels were elevated only in the CSF viremic group (p < 0.05). CSF Gal-9 positively correlated with age in all groups (p < 0.05). CSF Gal-9 tracked with CSF HIV RNA irrespective of age (β = 0.33; p < 0.05). Higher CSF Gal-9 in the older viremic HIV+ group correlated with worse neuropsychological test performance scores independently of age and CSF HIV RNA (p < 0.05). Furthermore, CSF Gal-9 directly correlated with myeloid activation (CSF-soluble CD163 and neopterin) in both HIV+ older groups (p < 0.05). Among HIV+ necropsy specimens, Gal-9 expression was increased in select brain regions compared to controls (p < 0.05). Gal-9 may serve as a novel neuroimmuno-modulatory protein that is involved in driving cognitive deficits in those aging with HIV and may be valuable in tracking cognitive abnormalities.

Galectin-9 binds to O-glycans on protein disulfide isomerase

Changes in the T cell surface redox environment regulate critical cell functions, such as cell migration, viral entry and cytokine production. Cell surface protein disulfide isomerase (PDI) contributes to the regulation of T cell surface redox status. Cell surface PDI can be released into the extracellular milieu or can be internalized by T cells. We have found that galectin-9, a soluble lectin expressed by T cells, endothelial cells and dendritic cells, binds to and retains PDI on the cell surface. While endogenous galectin-9 is not required for basal cell surface PDI expression, exogenous galectin-9 mediated retention of cell surface PDI shifted the disulfide/thiol equilibrium on the T cell surface. O-glycans on PDI are required for galectin-9 binding, and PDI recognition appears to be specific for galectin-9, as galectin-1 and galectin-3 do not bind PDI. Galectin-9 is widely expressed by immune and endothelial cells in inflamed tissues, suggesting that T cells would be exposed to abundant galectin-9, in cis and in trans, in infectious or autoimmune conditions.

GalNAc-Specific Soybean Lectin Inhibits HIV Infection of Macrophages through Induction of Antiviral Factors

Although it has been shown that some mannose-binding lectins (MBLs) exhibit significant activity against HIV infection, little is known about whether N-acetylgalactosamine (GalNAc)-binding lectins have the ability to inhibit HIV infection. Here, we demonstrate that a soybean-derived lectin (SBL) with GalNAc-binding affinity could potently suppress HIV infection of macrophages in a dose-dependent fashion. Unlike the MBLs, which block HIV only through binding to the glycosylated envelope proteins (gp120 and gp41) of the virus, SBL inhibited HIV at multiple steps of the virus infection/replication cycle. SBL could activate the beta interferon (IFN-β)-STAT signaling pathway, resulting in the upregulation of a number of antiviral interferon-stimulated genes (ISGs) in macrophages. In addition, SBL treatment of macrophages induced the production of C-C chemokines, which bind to HIV entry coreceptor CCR5. Deglycosylation of cell surface galactosyl moieties or presaturation of GalNAc-binding capacity could compromise SBL-mediated induction of the antiviral factors. Furthermore, SBL exerted its anti-HIV activity in the low nanomolar range with no mitogenic effect on CD4⁺ T cells, a major advantage in the development of SBL as a potential anti-HIV agent compared with MBLs. These data indicate a necessity to further investigate SBL as an alternative and cost-effective anti-HIV natural product.IMPORTANCE Mannose-binding lectins (MBLs) can block the attachment of HIV to target cells and have been suggested as anti-HIV microbicides. However, the mitogenic effect of MBLs on CD4⁺ T cells limits this potential in clinical settings. Lectins with galactose (Gal)- or N-acetylgalactosamine (GalNAc)-binding specificity are another important category of carbohydrate-binding proteins (CBP). Compared to high-mannose N-linked glycans, GalNAc-type glycans present much less in HIV gp120 or gp41 glycosylation. Here, we demonstrate that GalNAc-specific soybean lectin (SBL) triggers antiviral signaling via recognition of the cell surface galactosyl group of macrophages, which results in the suppression of HIV at multiple steps. More importantly, SBL has no mitogenic effect on the activation of CD4⁺ T cells, a major advantage in the development of Gal/GalNAc-specific lectins as naturopathic anti-HIV agents.

Benzotriazoles Reactivate Latent HIV-1 through Inactivation of STAT5 SUMOylation

The presence of latent HIV-1 in infected individuals represents a major barrier preventingviral eradication. For that reason, reactivation of latent viruses in the presence of antiretroviral regimens has been proposed as a therapeutic strategy to achieve remission. We screened for small molecules and identified several benzotriazole derivatives with the ability to reactivate latent HIV-1. In the presence of IL-2, benzotriazoles reactivated and reduced the latent reservoir in primary cells, and, remarkably, viral reactivation was achieved without inducing cell proliferation, T cell activation, or cytokine release. Mechanistic studies showed that benzotriazoles block SUMOylation of phosphorylated STAT5, increasing STAT5’s activity and occupancy of the HIV-1 LTR. Our results identify benzotriazoles as latency reversing agents and STAT5 signaling and SUMOylation as targets for HIV-1 eradication strategies. These compounds represent a different direction in the search for “shock and kill” therapies.

Allogeneic stem cell transplantation in fully MHC-matched Mauritian cynomolgus macaques recapitulates diverse human clinical outcomes

Allogeneic hematopoietic stem cell transplantation (HSCT) is a critically important therapy for hematological malignancies, inborn errors of metabolism, and immunodeficiency disorders, yet complications such as graft-vs.-host disease (GvHD) limit survival. Development of anti-GvHD therapies that do not adversely affect susceptibility to infection or graft-vs.-tumor immunity are hampered by the lack of a physiologically relevant, preclinical model of allogeneic HSCT. Here we show a spectrum of diverse clinical HSCT outcomes including primary and secondary graft failure, lethal GvHD, and stable, disease-free full donor engraftment using reduced intensity conditioning and mobilized peripheral blood HSCT in unrelated, fully MHC-matched Mauritian-origin cynomolgus macaques. Anti-GvHD prophylaxis of tacrolimus, post-transplant cyclophosphamide, and CD28 blockade induces multi-lineage, full donor chimerism and recipient-specific tolerance while maintaining pathogen-specific immunity. These results establish a new preclinical allogeneic HSCT model for evaluation of GvHD prophylaxis and next-generation HSCT-mediated therapies for solid organ tolerance, cure of non-malignant hematological disease, and HIV reservoir clearance.

Rhesus macaques are not ideal for studying response to allogeneic hematopoietic stem cell transplant (allo-HSCT) owing to complex MHC genetics that prevent full MHC-matching. Here the authors show that inbred Mauritian-origin cynomolgus macaques are a superior preclinical model of allogeneic stem cell transplantation that mimics diverse clinical outcomes of human allo-HSCT.