In Vivo Activation of Human NK Cells by Treatment with an Interleukin-15 Superagonist Potently Inhibits Acute In Vivo HIV-1 Infection in Humanized Mice

Pathophysiology and preclinical relevance of experimental graft-versus-host disease in humanized mice

Graft-versus-host disease (GVHD) is a life-threatening complication of allogeneic hematopoietic cell transplantations (allo-HCT) used for the treatment of hematological malignancies and other blood-related disorders. Until recently, the discovery of actionable molecular targets to treat GVHD and their preclinical testing was almost exclusively based on modeling allo-HCT in mice by transplanting bone marrow and splenocytes from donor mice into MHC-mismatched recipient animals. However, due to fundamental differences between human and mouse immunology, the translation of these molecular targets into the clinic can be limited. Therefore, humanized mouse models of GVHD were developed to circumvent this limitation. In these models, following the transplantation of human peripheral blood mononuclear cells (PBMCs) into immunodeficient mice, T cells recognize and attack mouse organs, inducing GVHD. Thereby, humanized mice provide a platform for the evaluation of the effects of candidate therapies on GVHD mediated by human immune cells in vivo. Understanding the pathophysiology of this xenogeneic GVHD is therefore crucial for the design and interpretation of experiments performed with this model. In this article, we comprehensively review the cellular and molecular mechanisms governing GVHD in the most commonly used model of xenogeneic GVHD: PBMC-engrafted NOD/LtSz-PrkdcscidIL2rγtm1Wjl (NSG) mice. By re-analyzing public sequencing data, we also show that the clonal expansion and the transcriptional program of T cells in humanized mice closely reflect those in humans. Finally, we highlight the strengths and limitations of this model, as well as arguments in favor of its biological relevance for studying T-cell reactions against healthy tissues or cancer cells.

HIV-1 latency reversal and immune enhancing activity of IL-15 is not influenced by sex hormones

The role of different biological variables including biological sex, age, and sex hormones in Human immunodeficiency virus (HIV) cure approaches is not well understood. The γc-cytokine IL-15 is a clinically relevant cytokine that promotes immune activation and mediates HIV reactivation from latency. In this work, we examined the interplay that biological sex, age, and sex hormones 17β-estradiol, progesterone, and testosterone may have on the biological activity of IL-15. We found that IL-15-mediated CD4+ T cell activation was higher in female donors than in male donors. This difference was abrogated at high 17β-estradiol concentration. Additionally, there was a positive correlation between age and both IL-15-mediated CD8+ T cell activation and IFN-γ production. In a primary cell model of latency, biological sex, age, or sex hormones did not influence the ability of IL-15 to reactivate latent HIV. Finally, 17β-estradiol did not consistently affect reactivation of translation-competent reservoirs in CD4+ T cells from people living with HIV who are antiretroviral therapy (ART) suppressed. Our study has found that biological sex and age, but not sex hormones, may influence some of the biological activities of IL-15. Understanding how different biological variables may affect HIV cure therapies will help us evaluate current and future clinical trials aimed toward HIV cure in diverse populations.

Next-generation bNAbs for HIV-1 cure strategies

Despite the ability to suppress viral replication using anti-retroviral therapy (ART), HIV-1 remains a global public health problem. Curative strategies for HIV-1 have to target and eradicate latently infected cells across the body, i.e. the viral reservoir. Broadly neutralizing antibodies (bNAbs) targeting the HIV-1 envelope glycoprotein (Env) have the capacity to neutralize virions and bind to infected cells to initiate elimination of these cells. To improve the efficacy of bNAbs in terms of viral suppression and viral reservoir eradication, next generation antibodies (Abs) are being developed that address the current limitations of Ab treatment efficacy; (1) low antigen (Env) density on (reactivated) HIV-1 infected cells, (2) high viral genetic diversity, (3) exhaustion of immune cells and (4) short half-life of Abs. In this review we summarize and discuss preclinical and clinical studies in which anti-HIV-1 Abs demonstrated potent viral control, and describe the development of engineered Abs that could address the limitations described above. Next generation Abs with optimized effector function, avidity, effector cell recruitment and immune cell activation have the potential to contribute to an HIV-1 cure or durable control.

Highly Sensitive Analysis of Cervical Mucosal HIV-1 Infection Using Reporter Viruses Expressing Secreted Nanoluciferase

Ex vivo cervical tissue explant models offer a physiologically relevant approach for studying virus-host interactions that underlie mucosal HIV-1 transmission to women. However, the utility of cervical explant tissue (CET) models has been limited for both practical and technical reasons. These include assay variation, inadequate sensitivity for assessing HIV-1 infection and replication in tissue, and constraints imposed by the requirement for using multiple replica samples of CET to test each experimental variable and assay parameter. Here, we describe an experimental approach that employs secreted nanoluciferase (sNLuc) and current HIV-1 reporter virus technologies to overcome certain limitations of earlier ex vivo CET models. This method augments application of the CET model for investigating important questions involving mucosal HIV-1 transmission.

Resident cutaneous memory T cells: a clinical review of their role in chronic inflammatory dermatoses and potential as therapeutic targets

Resident memory T cells (T-RMs) remain in epithelial barrier tissues after antigen exposure and the initial effector phase. These T-RMs provide effective antimicrobial and anticancer immunity; however, pathogenic T-RMs have been shown to mediate various chronic inflammatory disorders in a variety of tissue types. In the skin, T-RMs are referred to as resident cutaneous memory T cells (cT-RMs). Understanding the mechanisms leading to the development and establishment of these cT-RMs populations may allow for targeted treatments that provide durable responses in chronic immune-mediated skin diseases, even after cessation. In this review, we summarize the evidence on cT-RMs as drivers of chronic inflammatory dermatoses, including psoriasis, vitiligo, atopic dermatitis, cutaneous lupus erythematosus and alopecia areata, among others. Data from in vitro, animal model and ex vivo human studies are presented, with a focus on the potential for cT-RMs to trigger acute disease flares, as well as recurrent disease, by establishing an immune 'memory' in the skin. Furthermore, the available data on the potential for existing and novel treatments to affect the development or survival of cT-RMs in the skin are synthesized. The data suggest a dynamic and rapidly growing area in the field of dermatology; however, we also discuss areas in need of greater research to allow for optimal treatment selection for long-term disease control.

Multimeric immunotherapeutic complexes activating natural killer cells towards HIV-1 cure

BACKGROUND

Combination antiretroviral therapy (cART) has dramatically extended the life expectancy of people living with HIV-1 and improved their quality of life. There is nevertheless no cure for HIV-1 infection since HIV-1 persists in viral reservoirs of latently infected CD4+ T cells. cART does not eradicate HIV-1 reservoirs or restore cytotoxic natural killer (NK) cells which are dramatically reduced by HIV-1 infection, and express the checkpoint inhibitors NKG2A or KIR2DL upregulated after HIV-1 infection. Cytotoxic NK cells expressing the homing receptor CXCR5 were recently described as key subsets controlling viral replication.

METHODS

We designed and evaluated the potency of "Natural killer activating Multimeric immunotherapeutic compleXes", called as NaMiX, combining multimers of the IL-15/IL-15Rα complex with an anti-NKG2A or an anti-KIR single-chain fragment variable (scFv) to kill HIV-1 infected CD4+ T cells. The oligomerization domain of the C4 binding protein was used to associate the IL-15/IL-15Rα complex to the scFv of each checkpoint inhibitor as well as to multimerize each entity into a heptamer (α form) or a dimer (β form). Each α or β form was compared in different in vitro models using one-way ANOVA and post-hoc Tukey's tests before evaluation in humanized NSG tg-huIL-15 mice having functional NK cells.

RESULTS

All NaMiX significantly enhanced the cytolytic activity of NK and CD8+ T cells against Raji tumour cells and HIV-1+ ACH-2 cells by increasing degranulation, release of granzyme B, perforin and IFN-γ. Targeting NKG2A had a stronger effect than targeting KIR2DL due to higher expression of NKG2A on NK cells. In viral inhibition assays, NaMiX initially increased viral replication of CD4+ T cells which was subsequently inhibited by cytotoxic NK cells. Importantly, anti-NKG2A NaMiX enhanced activation, cytotoxicity, IFN-γ production and CXCR5 expression of NK cells from HIV-1 positive individuals. In humanized NSG tg-huIL-15 mice, we confirmed enhanced activation, degranulation, cytotoxicity of NK cells, and killing of HIV-1 infected cells from mice injected with the anti-NKG2A.α NaMiX, as compared to control mice, as well as decreased total HIV-1 DNA in the lung.

CONCLUSIONS

NK cell-mediated killing of HIV-1 infected cells by NaMiX represents a promising approach to support HIV-1 cure strategies.

IL-15 and N-803 for HIV Cure Approaches

In spite of the advances in antiretroviral therapy to treat HIV infection, the presence of a latent reservoir of HIV-infected cells represents the largest barrier towards finding a cure. Among the different strategies being pursued to eliminate or reduce this latent reservoir, the γc-cytokine IL-15 or its superagonist N-803 are currently under clinical investigation, either alone or with other interventions. They have been shown to reactivate latent HIV and enhance immune effector function, both of which are potentially required for effective reduction of latent reservoirs. In here, we present a comprehensive literature review of the different in vitro, ex vivo, and in vivo studies conducted to date that are aimed at targeting HIV reservoirs using IL-15 and N-803.

Immunomodulation with IL-7 and IL-15 in HIV-1 infection

Immunomodulating agents are substances that modify the host immune responses in diseases such as infections, autoimmune conditions and cancers. Immunomodulators can be divided into two main groups: 1) immunostimulators that activate the immune system such as cytokines, toll-like receptor agonists and immune checkpoint blockers; and 2) immunosuppressors that dampen an overactive immune system such as corticosteroids and cytokine-blocking antibodies. In this review, we have focussed on the two primarily T and natural killer (NK) cell homeostatic cytokines: interleukin-7 (IL-7) and -15 (IL-15). These cytokines are immunostimulators which act on immune cells independently of the presence or absence of antigen. In vivo studies have shown that IL-7 administration enhances proliferation of circulating T cells whereas IL-15 agonists enhance the proliferation and function of NK and CD8+ T cells. Both IL-7 and IL-15 therapies have been tested as single interventions in HIV-1 cure-related clinical trials. In this review, we explore whether IL-7 and IL-15 could be part of the therapeutic approaches towards HIV-1 remission.

Current Advances in Humanized Mouse Models for Studying NK Cells and HIV Infection

Human immunodeficiency virus (HIV) has infected millions of people worldwide and continues to be a major global health problem. Scientists required a small animal model to study HIV pathogenesis and immune responses. To this end, humanized mice were created by transplanting human cells and/or tissues into immunodeficient mice to reconstitute a human immune system. Thus, humanized mice have become a critical animal model for HIV researchers, but with some limitations. Current conventional humanized mice are prone to death by graft versus host disease induced by the mouse signal regulatory protein α and CD47 signaling pathway. In addition, commonly used humanized mice generate low levels of human cytokines required for robust myeloid and natural killer cell development and function. Here, we describe recent advances in humanization procedures and transgenic and knock-in immunodeficient mice to address these limitations.

HIV infection dynamics and viral rebound: Modeling results from humanized mice

Despite years of combined antiretroviral therapy (cART), HIV persists in infected individuals. The virus also rebounds after the cessation of cART. The sources contributing to viral persistence and rebound are not fully understood. When viral rebound occurs, what affects the time to rebound and how to delay the rebound remain unclear. In this paper, we started with the data fitting of an HIV infection model to the viral load data in treated and untreated humanized myeloid-only mice (MoM) in which macrophages serve as the target of HIV infection. By fixing the parameter values for macrophages from the MoM fitting, we fit a mathematical model including the infection of two target cell populations to the viral load data from humanized bone marrow/liver/thymus (BLT) mice, in which both CD4+ T cells and macrophages are the target of HIV infection. Data fitting suggests that the viral load decay in BLT mice under treatment has three phases. The loss of infected CD4+ T cells and macrophages is a major contributor to the first two phases of viral decay, and the last phase may be due to the latent infection of CD4+ T cells. Numerical simulations using parameter estimates from the data fitting show that the pre-ART viral load and the latent reservoir size at treatment cessation can affect viral growth rate and predict the time to viral rebound. Model simulations further reveal that early and prolonged cART can delay the viral rebound after cessation of treatment, which may have implications in the search for functional control of HIV infection.

Human Hematopoietic Stem Cell Engrafted IL-15 Transgenic NSG Mice Support Robust NK Cell Responses and Sustained HIV-1 Infection

Mice reconstituted with human immune systems are instrumental in the investigation of HIV-1 pathogenesis and therapeutics. Natural killer (NK) cells have long been recognized as a key mediator of innate anti-HIV responses. However, established humanized mouse models do not support robust human NK cell development from engrafted human hematopoietic stem cells (HSCs). A major obstacle to human NK cell reconstitution is the lack of human interleukin-15 (IL-15) signaling, as murine IL-15 is a poor stimulator of the human IL-15 receptor. Here, we demonstrate that immunodeficient NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) mice expressing a transgene encoding human IL-15 (NSG-Tg(IL-15)) have physiological levels of human IL-15 and support long-term engraftment of human NK cells when transplanted with human umbilical-cord-blood-derived HSCs. These Hu-NSG-Tg(IL-15) mice demonstrate robust and long-term reconstitution with human immune cells, but do not develop graft-versus-host disease (GVHD), allowing for long-term studies of human NK cells. Finally, we show that these HSC engrafted mice can sustain HIV-1 infection, resulting in human NK cell responses in HIV-infected mice. We conclude that Hu-NSG-Tg(IL-15) mice are a robust novel model to study NK cell responses to HIV-1.

Use of Hu-PBL Mice to Study Pathogenesis of Human-Restricted Viruses

Different humanized mouse models have been developed to study human diseases such as autoimmune illnesses, cancer and viral infections. These models are based on the use of immunodeficient mouse strains that are transplanted with human tissues or human immune cells. Among the latter, mice transplanted with hematopoietic stem cells have been widely used to study human infectious diseases. However, mouse models built upon the transplantation of donor-specific mature immune cells are still under development, especially in the field of viral infections. These models can retain the unique immune memory of the donor, making them suitable for the study of correlates of protection upon natural infection or vaccination. Here, we will review some of these models and how they have been applied to virology research. Moreover, the future applications and the potential of these models to design therapies against human viral infections are discussed.

Natural killer cells for antiviral therapy

Natural killer (NK) cell-based immunotherapy is being explored for treating infectious diseases, including viral infections. Here, we discuss evidence of NK cell responses to different viruses, ongoing clinical efforts to treat such infections with NK cell products, and review platforms to generate NK cell products.

A humanized mouse model to study NK cell biology during HIV infection

NK cells are an important subset of innate immune effectors with antiviral activity. However, NK cell development and immune responses in different tissues during acute and chronic HIV infection in vivo have been difficult to study due to the impaired development and function of NK cells in conventional humanized mouse models. In this issue of the JCI, Sangur et al. report on a transgenic MISTRG-6-15 mouse model with human IL-6 and IL-15 knocked into the previously constructed MISTRG mice. The predecessor model was deficient in Rag2 and γ chain (γc) with knock-in expression of human M-CSF, IL-3, GM-CSF, and TPO, and transgenic expression of human SIRPα. The researchers studied tissue-specific NK cell immune responses during HIV infection and clearly show that the endogenous human NK cells in the humanized mouse model suppressed HIV-1 replication in vivo. These findings provide insight into harnessing the innate immune response for clinical antiviral therapies.

Natural killer cells during acute HIV-1 infection: clues for HIV-1 prevention and therapy

Despite progress in preexposure prophylaxis, the number of newly diagnosed cases with HIV-1 remains high, highlighting the urgent need for preventive and therapeutic strategies to reduce HIV-1 acquisition and limit disease progression. Early immunological events, occurring during acute infection, are key determinants of the outcome and course of disease. Understanding early immune responses occurring before viral set-point is established, is critical to identify potential targets for prophylactic and therapeutic approaches. Natural killer (NK) cells represent a key cellular component of innate immunity and contribute to the early host defence against HIV-1 infection, modulating the pathogenesis of acute HIV-1 infection (AHI). Emerging studies have identified tools for harnessing NK cell responses and expanding specialized NK subpopulations with adaptive/memory features, paving the way for development of novel HIV-1 therapeutics. This review highlights the knowns and unknowns regarding the role of NK cell subsets in the containment of acute HIV-1 infection, and summarizes recent advances in selectively augmenting NK cell functions through prophylactic and therapeutic interventions.

Effective innate immune response in natural HIV-1 controllers. Can mimicking lead to novel preventive and cure strategies against HIV-1?

PURPOSE OF REVIEW

HIV-1 controller individuals represents a model that can be useful for the development of novel vaccines and therapies. Initial studies pointed to the involvement of improved adaptive immunity, however, new emerging evidence suggests the contribution of innate cells to effective antiviral responses in spontaneous controllers. Therefore, understanding the alterations on innate cell subsets might be crucial to develop new effective therapeutic strategies.

RECENT FINDINGS

Among different innate immune cells, dendritic cell (DC) and natural killer (NK) cell are essential for effective antiviral responses. DC from controllers display improved innate detection of HIV-1 transcripts, higher induction of interferons, higher antigen presenting capacities and increased metabolism and higher capacities to induce polyfunctional CD8+ T-cell responses. Such properties have been mimicked by Toll-like receptor ligands and applied to DC-based immunotherapies in humans and in animal models. NK cells from controllers display higher expression of activating receptors promoting increased antibody-dependent cellular cytotoxicity (ADCC) and natural cytotoxicity activities. Neutralizing antibodies in combination with interleukin-15 superagonist or interferon-α can increase ADCC and cytotoxicity in NK cells from HIV-1 progressors.

SUMMARY

Mimicking DC and NK cell innate profiles in controllers has become a promising strategy to step forward a novel efficient immunotherapy against the HIV-1 infection.

The HIV Latency Reversal Agent HODHBt Enhances NK Cell Effector and Memory-Like Functions by Increasing Interleukin-15-Mediated STAT Activation

Elimination of human immunodeficiency virus (HIV) reservoirs is a critical endpoint to eradicate HIV. One therapeutic intervention against latent HIV is "shock and kill." This strategy is based on the transcriptional activation of latent HIV with a latency-reversing agent (LRA) with the consequent killing of the reactivated cell by either the cytopathic effect of HIV or the immune system. We have previously found that the small molecule 3-hydroxy-1,2,3-benzotriazin-4(3H)-one (HODHBt) acts as an LRA by increasing signal transducer and activator of transcription (STAT) factor activation mediated by interleukin-15 (IL-15) in cells isolated from aviremic participants. The IL-15 superagonist N-803 is currently under clinical investigation to eliminate latent reservoirs. IL-15 and N-803 share similar mechanisms of action by promoting the activation of STATs and have shown some promise in preclinical models directed toward HIV eradication. In this work, we evaluated the ability of HODHBt to enhance IL-15 signaling in natural killer (NK) cells and the biological consequences associated with increased STAT activation in NK cell effector and memory-like functions. We showed that HODHBt increased IL-15-mediated STAT phosphorylation in NK cells, resulting in increases in the secretion of CXCL-10 and interferon gamma (IFN-γ) and the expression of cytotoxic proteins, including granzyme B, granzyme A, perforin, granulysin, FASL, and TRAIL. This increased cytotoxic profile results in increased cytotoxicity against HIV-infected cells and different tumor cell lines. HODHBt also improved the generation of cytokine-induced memory-like NK cells. Overall, our data demonstrate that enhancing the magnitude of IL-15 signaling with HODHBt favors NK cell cytotoxicity and memory-like generation, and thus, targeting this pathway could be further explored for HIV cure interventions. IMPORTANCE Several clinical trials targeting the HIV latent reservoir with LRAs have been completed. In spite of a lack of clinical benefit, they have been crucial to elucidate hurdles that "shock and kill" strategies have to overcome to promote an effective reduction of the latent reservoir to lead to a cure. These hurdles include low reactivation potential mediated by LRAs, the negative influence of some LRAs on the activity of natural killer and effector CD8 T cells, an increased resistance to apoptosis of latently infected cells, and an exhausted immune system due to chronic inflammation. To that end, finding therapeutic strategies that can overcome some of these challenges could improve the outcome of shock and kill strategies aimed at HIV eradication. Here, we show that the LRA HODHBt also improves IL-15-mediated NK cell effector and memory-like functions. As such, pharmacological enhancement of IL-15-mediated STAT activation can open new therapeutic avenues toward an HIV cure.

Engaging innate immunity in HIV-1 cure strategies

Combination antiretroviral therapy (ART) can block multiple stages of the HIV-1 life cycle to prevent progression to AIDS in people living with HIV-1. However, owing to the persistence of a reservoir of latently infected CD4⁺ T cells, life-long ART is necessary to prevent viral rebound. One strategy currently under consideration for curing HIV-1 infection is known as 'shock and kill'. This strategy uses latency-reversing agents to induce expression of HIV-1 genes, allowing for infected cells to be cleared by cytolytic immune cells. The role of innate immunity in HIV-1 pathogenesis is best understood in the context of acute infection. Here, we suggest that innate immunity can also be used to improve the efficacy of HIV-1 cure strategies, with a particular focus on dendritic cells (DCs) and natural killer cells. We discuss novel latency-reversing agents targeting DCs as well as DC-based strategies to enhance the clearance of infected cells by CD8⁺ T cells and strategies to improve the killing activity of natural killer cells.

Advances of research of Fc-fusion protein that activate NK cells for tumor immunotherapy

The rapid development of bioengineering technology has introduced Fc-fusion proteins, representing a novel kind of recombinant protein, as promising biopharmaceutical products in tumor therapy. Numerous related anti-tumor Fc-fusion proteins have been investigated and are in different stages of development. Fc-fusion proteins are constructed by fusing the Fc-region of the antibody with functional proteins or peptides. They retain the bioactivity of the latter and partial properties of the former. This structural and functional advantage makes Fc-fusion proteins an effective tool in tumor immunotherapy, especially for the recruitment and activation of natural killer (NK) cells, which play a critical role in tumor immunotherapy. Even though tumor cells have developed mechanisms to circumvent the cytotoxic effect of NK cells or induce defective NK cells, Fc-fusion proteins have been proven to effectively activate NK cells to kill tumor cells in different ways, such as antibody-dependent cell-mediated cytotoxicity (ADCC), activate NK cells in different ways in order to promote killing of tumor cells. In this review, we focus on NK cell-based immunity for cancers and current research progress of the Fc-fusion proteins for anti-tumor therapy by activating NK cells.

CounterAKTing HIV: Toward a “Block and Clear” Strategy?

The protein kinase B or Akt is a central regulator of survival, metabolism, growth and proliferation of the cells and is known to be targeted by various viral pathogens, including HIV-1. The central role of Akt makes it a critical player in HIV-1 pathogenesis, notably by affecting viral entry, latency and reactivation, cell survival, viral spread and immune response to the infection. Several HIV proteins activate the PI3K/Akt pathway, to fuel the progression of the infection. Targeting Akt could help control HIV-1 entry, viral latency/replication, cell survival of infected cells, HIV spread from cell-to-cell, and the immune microenvironment which could ultimately allow to curtail the size of the HIV reservoir. Beside the “shock and kill” and “block and lock” strategies, the use of Akt inhibitors in combination with latency inducing agents, could favor the clearance of infected cells and be part of new therapeutic strategies with the goal to “block and clear” HIV.

Immune Dysfunctions of CD56neg NK Cells Are Associated With HIV-1 Disease Progression

Background

Populations of natural killer cells lacking CD56 expression [CD56^neg natural killer (NK) cells] have been demonstrated to expand during human immunodeficiency virus (HIV)-1 infection. However, their phenotypic and functional characteristics have not been systematically analyzed, and their roles during disease progression remain poorly understood.

Methods

In this study, 84 donors, namely 34 treatment-naïve HIV-1-infected patients (TNs), 29 HIV-1-infected patients with successful antiretroviral therapy (ARTs), and 21 healthy controls (HCs), were enrolled. The phenotypic and functional characteristics of CD56^neg NK cells were analyzed using single-cell RNA-sequencing (scRNA-seq) and flow cytometry. A potential link between the characteristics of CD56^neg NK cells and the clinical parameters associated with HIV-1 disease progression was examined.

Results

The frequency of the CD56^neg NK cell population was significantly increased in TNs, which could be partially rescued by ART. Flow cytometry analyses revealed that CD56^neg NK cells were characterized by high expression of CD39, TIGIT, CD95, and Ki67 compared to CD56^dim NK cells. In vitro assays revealed reduced IFN-γ and TNF-α secretion, as well as decreased expression of granzyme B and perforin in CD56^neg NK cells. In line with the data obtained by flow cytometry, scRNA-seq analysis further demonstrated impaired cytotoxic activities of CD56^neg NK cells. Notably, a negative correlation was observed between CD39, CD95, and Ki67 expression levels in CD56^neg NK cells and CD4⁺ T cell counts.

Conclusions

The results presented in this study indicate that the CD56^neg NK cell population expanded in HIV-1-infected individuals is dysfunctional and closely correlates with HIV-1 disease progression.

So Pathogenic or So What?-A Brief Overview of SIV Pathogenesis with an Emphasis on Cure Research

HIV infection requires lifelong antiretroviral therapy (ART) to control disease progression. Although ART has greatly extended the life expectancy of persons living with HIV (PWH), PWH nonetheless suffer from an increase in AIDS-related and non-AIDS related comorbidities resulting from HIV pathogenesis. Thus, an HIV cure is imperative to improve the quality of life of PWH. In this review, we discuss the origins of various SIV strains utilized in cure and comorbidity research as well as their respective animal species used. We briefly detail the life cycle of HIV and describe the pathogenesis of HIV/SIV and the integral role of chronic immune activation and inflammation on disease progression and comorbidities, with comparisons between pathogenic infections and nonpathogenic infections that occur in natural hosts of SIVs. We further discuss the various HIV cure strategies being explored with an emphasis on immunological therapies and "shock and kill".

Implications of the accumulation of CXCR5+ NK cells in lymph nodes of HIV-1 infected patients

Background

B cell follicles are immune-privileged sites where intensive HIV-1 replication and latency occur, preventing a permanent cure. Recent study showed that CXCR5⁺ NK cells in B cell follicles can inhibit SIV replication in African green monkeys, but this has not been reported in HIV-1 infected patients.

Methods

Lymphocytes and tissue sections of lymph node were collected from 11 HIV-1 positive antiretroviral therapy (ART)-naive and 19 HIV-1 negative donors. We performed immunofluorescence and RNA-scope to detect the location of CXCR5⁺ NK cells and its relationship with HIV-1 RNA, and performed flow cytometry and RNA-seq to analyze the frequency, phenotypic and functional characteristics of CXCR5⁺ NK cells. The CXCL13 expression were detected by immunohistochemistry.

Findings

CXCR5⁺ NK cells, which accumulated in LNs from HIV-1 infected individuals, expressed high levels of activating receptors such as NKG2D and NKp44. CXCR5⁺ NK cells had upregulated expression of CD107a and β-chemokines, which were partially impaired in HIV-1 infection. Importantly, the frequency of CXCR5⁺NK cells was inversely related to the HIV-1 viral burden in LNs. In addition, CXCL13—the ligand of CXCR5—was upregulated in HIV-1 infected individuals and positively correlated with the frequency of CXCR5⁺ NK cells.

Interpretation

During chronic HIV-1 infection, CXCR5⁺ NK cells accumulated in lymph node, exhibit altered immune characteristics and underlying anti-HIV-1 effect, which may be an effective target for a functional cure of HIV-1.

T cell receptor-targeted immunotherapeutics drive selective in vivo HIV- and CMV-specific T cell expansion in humanized mice

To delineate the in vivo role of different costimulatory signals in activating and expanding highly functional virus-specific cytotoxic CD8+ T cells, we designed synTacs, infusible biologics that recapitulate antigen-specific T cell activation signals delivered by antigen-presenting cells. We constructed synTacs consisting of dimeric Fc-domain scaffolds linking CD28- or 4-1BB-specific ligands to HLA-A2 MHC molecules covalently tethered to HIV- or CMV-derived peptides. Treatment of HIV-infected donor PBMCs with synTacs bearing HIV- or CMV-derived peptides induced vigorous and selective ex vivo expansion of highly functional HIV- and/or CMV-specific CD8+ T cells, respectively, with potent antiviral activities. Intravenous injection of HIV- or CMV-specific synTacs into immunodeficient mice intrasplenically engrafted with donor PBMCs markedly and selectively expanded HIV-specific (32-fold) or CMV-specific (46-fold) human CD8+ T cells populating their spleens. Notably, these expanded HIV- or CMV-specific CD8+ T cells directed potent in vivo suppression of HIV or CMV infections in the humanized mice, providing strong rationale for consideration of synTac-based approaches as a therapeutic strategy to cure HIV and treat CMV and other viral infections. The synTac platform flexibility supports facile delineation of in vivo effects of different costimulatory signals on patient-derived virus-specific CD8+ T cells, enabling optimization of individualized therapies, including HIV cure strategies.

NK cell-based therapies for HIV infection: Investigating current advances and future possibilities

NK cells are well-known for their antiviral functions. Also, their role in HIV has been well established, with rapid responses elicited during early HIV infection. Most immune cells including CD4⁺ T cells, monocytes, Mϕs, and dendritic cells are readily infected by HIV. Recent evidence from multiple studies has suggested that similar to these cells, in chronic conditions like HIV, NK cells also undergo functional exhaustion with impaired cytotoxicity, altered cytokine production, and impaired ADCC. NK-based immunotherapy aims to successfully restore, boost, and modify their activity as has been already demonstrated in the field of cancer immunotherapy. The utilization of NK cell-based strategies for the eradication of HIV from the body provides many advantages over classical ART. The literature search consisted of manually selecting the most relevant studies from databases including PubMed, Embase, Google Scholar, and ClinicalTrial.gov. Some of the treatments currently under consideration are CAR-NK cell therapy, facilitating ADCC, TLR agonists, bNAbs, and BiKEs/TriKEs, blocking inhibitory NK receptors during infection, IL-15 and IL-15 superagonists (eg: ALT-803), and so on. This review aims to discuss the NK cell-based therapies currently under experimentation against HIV infection and finally highlight the challenges associated with NK cell-based immunotherapies.

Therapeutic Potential of IL-15 and N-803 in HIV/SIV Infection

IL-15, a proinflammatory cytokine critical for the generation, maintenance, and homeostasis of T cell responses, is produced naturally in response to HIV/SIV infection, but has also demonstrated therapeutic potential. IL-15 can boost CD4+ and CD8+ T cell and NK cell proliferation, activation, and function. However, IL-15 treatment may cause aberrant immune activation and accelerated disease progression in certain circumstances. Moreover, the relationship between the timing of IL-15 administration and disease progression remains unclear. The IL-15 superagonist N-803 was developed to expand the therapeutic potential of IL-15 by maximizing its tissue distribution and half-life. N-803 has garnered enthusiasm recently as a way to enhance the innate and cellular immune responses to HIV/SIV by improving CD8+ T cell recognition and killing of virus-infected cells and directing immune cells to mucosal sites and lymph nodes, the primary sites of virus replication. N-803 has also been evaluated in "shock and kill" strategies due to its potential to reverse latency (shock) and enhance antiviral immunity (kill). This review examines the current literature about the effects of IL-15 and N-803 on innate and cellular immunity, viral burden, and latency reversal in the context of HIV/SIV, and their therapeutic potential both alone and combined with additional interventions such as antiretroviral therapy (ART) and vaccination.

Bifunctional TGF-β trap/IL-15 Protein Complex Elicits Potent NK Cell and CD8+ T Cell Immunity Against Solid Tumors

Advances in immunostimulatory and anti-immunosuppressive therapeutics have revolutionized cancer treatment. However, novel immunotherapeutics with these dual functions are not frequently reported. Here we describe the creation of a heterodimeric bifunctional fusion molecule, HCW9218, constructed using our soluble tissue factor-based scaffold technology. This complex comprises extracellular domains of the human transforming growth factor-β (TGF-β) receptor II and a human interleukin (IL)-15/IL-15 receptor α complex. HCW9218 can be readily expressed in CHO cells and purified using antibody-based affinity chromatography in a large-scale manufacturing setting. HCW9218 potently activates mouse natural killer (NK) cells and CD8⁺ T cells in vitro and in vivo to enhance cell proliferation, metabolism and antitumor cytotoxic activities. Similarly, human immune cells become activated with increased cytotoxicity following incubation with HCW9218. This fusion complex also exhibits TGF-β neutralizing activity in vitro and sequesters plasma TGF-β in vivo. In a syngeneic B16F10 melanoma model, HCW9218 displayed strong antitumor activity mediated by NK cells and CD8⁺ T cells, and increased their infiltration into tumors. Repeat-dose subcutaneous administration of HCW9218 was well tolerated by mice, with a half-life sufficient to provide long lasting biological activity. Thus, HCW9218 may serve as a novel therapeutic to simultaneously provide immunostimulation and lessen immunosuppression associated with tumors.

An overview of some potential immunotherapeutic options against COVID-19

After the advent of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) in the late 2019, the resulting severe and pernicious syndrome (COVID-19) immediately was deployed all around the world. To date, despite relentless efforts to control the disease by drug repurposing, there is no approved specific therapy for COVID-19. Given the role of innate and acquired immune components in the control and elimination of viral infections and inflammatory mutilations during SARS-CoV2 pathogenesis, immunotherapeutic strategies appear to be beneficent. Passive immunotherapies such as convalescent plasma, which has received much attention especially in severe cases, as well as suppressing inflammatory cytokines, interferon administration, inhibition of kinases and complement cascade, virus neutralization with key engineered products, cell-based therapies, immunomodulators and anti-inflammatory drugs are among the key immunotherapeutic approaches to deal with COVID-19, which is discussed in this review. Also, details of leading COVID-19 vaccine candidates as the most potent immunotherapy have been provided. However, despite salient improvements, there is still a lack of completely assured vaccines for universal application. Therefore, adopting proper immunotherapies according to the cytokine pattern and involved immune responses, alongside engineered biologics specially ACE2-Fc to curb SARS-CoV2 infection until achieving a tailored vaccine is probably the best strategy to better manage this pandemic. Therefore, gaining knowledge about the mechanism of action, potential targets, as well as the effectiveness of immune-based approaches to confront COVID-19 in the form of a well-ordered review study is highly momentous.

Evolution and Diversity of Immune Responses during Acute HIV Infection

Understanding the earliest immune responses following HIV infection is critical to inform future vaccines and therapeutics. Here, we review recent prospective human studies in at-risk populations that have provided insight into immune responses during acute infection, including additional relevant data from non-human primate (NHP) studies. We discuss the timing, nature, and function of the diverse immune responses induced, the onset of immune dysfunction, and the effects of early anti-retroviral therapy administration. Treatment at onset of viremia mitigates peripheral T and B cell dysfunction, limits seroconversion, and enhances cellular antiviral immunity despite persistence of infection in lymphoid tissues. We highlight pertinent areas for future investigation, and how application of high-throughput technologies, alongside targeted NHP studies, may elucidate immune response features to target in novel preventions and cures.

Humanized Mice for the Evaluation of Novel HIV-1 Therapies

With the discovery of antiretroviral therapy, HIV-1 infection has transitioned into a manageable but chronic illness, which requires lifelong treatment. Nevertheless, complete eradication of the virus has still eluded us. This is partly due to the virus’s ability to remain in a dormant state in tissue reservoirs, ‘hidden’ from the host’s immune system. Also, the high mutation rate of HIV-1 results in escape mutations in response to many therapeutics. Regardless, the development of novel cures for HIV-1 continues to move forward with a range of approaches from immunotherapy to gene editing. However, to evaluate in vivo pathogenesis and the efficacy and safety of therapeutic approaches, a suitable animal model is necessary. To this end, the humanized mouse was developed by McCune in 1988 and has continued to be improved on over the past 30 years. Here, we review the variety of humanized mouse models that have been utilized through the years and describe their specific contribution in translating HIV-1 cure strategies to the clinic.

Analysis of the Characteristics of TIGIT-Expressing CD3-CD56+NK Cells in Controlling Different Stages of HIV-1 Infection

TIGIT expression on natural killer (NK) cells is associated with dysfunction during chronic HIV infection, but the phenotype and biological functions of these cells in the context of acute HIV-1 infection remain poorly understood. Here, 19 acutely infected HIV-1 patients traced at first, third and twelfth month, and age-matched patients with chronic HIV-1 infection were enrolled to investigate the phenotype and functions of TIGIT expression on NK cells. We found that TIGIT-expressing NK cells did not increase in frequency in the first, third and twelfth month of infection until chronic HIV-1 infection lasted over 2 years. The number of TIGIT⁺NK cells in acute infection was positively associated with HIV-1 viral load (r = 0.53, P = 0.0009). CD96 was significantly upregulated on NK cells after acute infection for 1 month and in chronic infection over 2 years, while CD226 was downregulated in chronic infection over 2 years. Further, at different stages of infection, CD96⁻CD226⁺ cells diminished among total NK cells, TIGIT⁺NK and TIGIT⁻NK cells, while CD96⁺CD226⁻ cells expanded. Reduced CD96⁻CD226⁺ cells and elevated CD96⁺CD226⁻ cells among NK cells especially TIGIT⁻NK cells, had opposite associations with viral load in the first month of infection, as well as CD4 T-cell counts in including the twelfth month and more than 2 years of chronic infection. In both HIV-1-infected individuals and healthy donors, TIGIT was predominantly expressed in NKG2A⁻NKG2C⁺NK cells, with a significantly higher proportion than in NKG2A⁺NKG2C⁻NK cells. Moreover, the frequencies of TIGIT⁺NK cells were positively associated with the frequencies of NKG2A⁻NKG2C⁺NK cells in acute infection (r = 0.62, P < 0.0001), chronic infection (r = 0.37, P = 0.023) and healthy donors (r = 0.36, P = 0.020). Enhanced early activation and coexpression of CD38 and HLA-DR in TIGIT⁺NK cells were detected compared to TIGIT⁻NK cells, both of which were inversely associated with the decrease in CD4 T-cell counts in both acute and chronic HIV-1 infection. The ability of TIGIT⁺NK cells to produce TNF-α, IFN-γ and CD107a degranulation substance were consistently weaker than that of TIGIT⁻NK cells in both acute and chronic infection. Moreover, the functionalities of TIGIT⁺NK cells were lower than those of TIGIT⁻NK cells, except for TNF-α⁻CD107a⁺IFN-γ⁻NK cells. These findings highlight the phenotype and functional characteristics of TIGIT-expressing NK cells which have poor capabilities in inhibiting HIV-1 replication and maintaining CD4 T-cell counts.

Pediatric HIV: the Potential of Immune Therapeutics to Achieve Viral Remission and Functional Cure

PURPOSE OF REVIEW

In the absence of antiretroviral therapy (ART), more than 50% of perinatally HIV-infected children die by 2 years of age. Early ART from infancy is therefore a global recommendation and significantly improves immune health, child survival, and disease outcome. However, even early treatment does not prevent or eradicate the latent reservoir necessitating life-long ART. Adherence to life-long ART is challenging for children and longstanding ART during chronic HIV infection led to higher risks of non-AIDS co-morbidities and virologic failure in infected children. Thus, HIV-infected children are an important population for consideration for immune-based interventions to achieve ART-free remission and functional cure. This review summarizes how the uniqueness of the early life immune system can be harnessed for the development of ART-free remission and functional cure, which means complete virus control in absence of ART. In addition, recent advances in therapeutics in the HIV cure field and their potential for the treatment of pediatric HIV infections are discussed.

RECENT FINDINGS

Preclinical studies and clinical trials demonstrated that immune-based interventions target HIV replication, limit size of virus reservoir, maintain virus suppression, and delay time to virus rebound. However, these studies have been performed so far only in carefully selected HIV-infected adults, highlighting the need to evaluate the efficacy of immune-based therapeutics in HIV-infected children and to design interventions tailored to the early life maturing immune system. Immune-based therapeutics alone or in combination with ART should be actively explored as potential strategies to achieve viral remission and functional cure in HIV-infected pediatric populations.

The Development of Next-generation PBMC Humanized Mice for Preclinical Investigation of Cancer Immunotherapeutic Agents

Investigation of the efficacy and mechanisms of human immuno-oncology agents has been hampered due to species-specific differences when utilizing preclinical mouse models. Peripheral blood mononuclear cell (PBMC) humanized mice provide a platform for investigating the modulation of the human immune-mediated antitumor response while circumventing the limitations of syngeneic model systems. Use of humanized mice has been stymied by model-specific limitations, some of which include the development of graft versus host disease, technical difficulty and cost associated with each humanized animal, and insufficient engraftment of some human immune subsets. Recent advances have addressed many of these limitations from which have emerged humanized models that are more clinically relevant. This review characterizes the expanded usage, advantages and limitations of humanized mice and provides insights into the development of the next generation of murine humanized models to further inform clinical applications of cancer immunotherapeutic agents.

Protective Immune Responses Elicited by Deglycosylated Live-Attenuated Simian Immunodeficiency Virus Vaccine Are Associated with IL-15 Effector Functions

Deglycosylated, live-attenuated SIV vaccines elicited protective immune responses against heterologous SIVsmE543-3, which differs from the vaccine strain SIVmac239 to levels similar to those across HIV-1 clades. Two thirds of the vaccinees contained the chronic SIVsmE543-3 infection (controllers), whereas one third did not (noncontrollers). In this study, we investigated immune correlates of heterologous challenge control in rhesus macaques of Burmese origin. Because depletion of CD8⁺ cells in the controllers by administration of anti-CD8α Ab abrogated the control of viral replication, CD8⁺ cells were required for the protective immune response. However, classical SIV-specific CD8⁺ T cells did not account for the protective immune response in all controllers. Instead, IL-15-responding CD8α⁺ cells, including CD8⁺ T and NK cells, were significantly higher in the controllers than those in the noncontrollers, before and after vaccination with deglycosylated SIV. It is well established that IL-15 signal transduction occurs through "trans-presentation" in which IL-15 complexed with IL-15Rα on monocytes, macrophages, and dendritic cells binds to IL-15 Rβ/γ expressed on CD8⁺ T and NK cells. Accordingly, levels of IL-15 stimulation were strongly affected by the depletion of monocytes from PBMCs, implying key roles of innate immune cells. These results suggest that intrinsic IL-15 responsiveness may dictate the outcome of protective responses and may lead to optimized formulations of future broadly protective HIV vaccines.

A Role of Intracellular Toll-Like Receptors (3, 7, and 9) in Response to Mycobacterium tuberculosis and Co-Infection with HIV

Mycobacterium tuberculosis (Mtb) is a highly infectious acid-fast bacillus and is known to cause tuberculosis (TB) in humans. It is a leading cause of death from a sole infectious agent, with an estimated 1.5 million deaths yearly worldwide, and up to one third of the world's population has been infected with TB. The virulence and susceptibility of Mtb are further amplified in the presence of Human Immunodeficiency Virus (HIV). Coinfection with Mtb and HIV forms a lethal combination. Previous studies had demonstrated the synergistic effects of Mtb and HIV, with one disease accelerating the disease progression of the other through multiple mechanisms, including the modulation of the immune response to these two pathogens. The response of the endosomal pattern recognition receptors to these two pathogens, specifically toll-like receptors (TLR)-3, -7, and -9, has not been elucidated, with some studies producing mixed results. This article seeks to review the roles of TLR-3, -7, and -9 in response to Mtb infection, as well as Mtb-HIV-coinfection via Toll-interleukin 1 receptor (TIR) domain-containing adaptor inducing INF-β (TRIF)-dependent and myeloid differentiation factor 88 (MyD88)-dependent pathways.

Multispecific anti-HIV duoCAR-T cells display broad in vitro antiviral activity and potent in vivo elimination of HIV-infected cells in a humanized mouse model

Adoptive immunotherapy using chimeric antigen receptor-modified T cells (CAR-T) has made substantial contributions to the treatment of certain B cell malignancies. Such treatment modalities could potentially obviate the need for long-term antiretroviral drug therapy in HIV/AIDS. Here, we report the development of HIV-1-based lentiviral vectors that encode CARs targeting multiple highly conserved sites on the HIV-1 envelope glycoprotein using a two-molecule CAR architecture, termed duoCAR. We show that transduction with lentiviral vectors encoding multispecific anti-HIV duoCARs confer primary T cells with the capacity to potently reduce cellular HIV infection by up to 99% in vitro and >97% in vivo. T cells are the targets of HIV infection, but the transduced T cells are protected from genetically diverse HIV-1 strains. The CAR-T cells also potently eliminated PBMCs infected with broadly neutralizing antibody-resistant HIV strains, including VRC01/3BNC117-resistant HIV-1. Furthermore, multispecific anti-HIV duoCAR-T cells demonstrated long-term control of HIV infection in vivo and prevented the loss of CD4⁺ T cells during HIV infection using a humanized NSG mouse model of intrasplenic HIV infection. These data suggest that multispecific anti-HIV duoCAR-T cells could be an effective approach for the treatment of patients with HIV-1 infection.

Harnessing Natural Killer Cell Innate and Adaptive Traits in HIV Infection

Despite efficient virological suppression on antiretroviral therapy (ART), people living with HIV (PLWH), experience an increased burden of premature co-morbidities, such as cancer and end-organ disease. With remaining challenges in terms of access to therapy, adherence and potential long-term drug toxicity, improving their long-term healthcare outcome, including new strategies for HIV clearance, remains a global priority. There is, therefore, an ongoing need to better characterize and harness the immune response in order to develop new strategies and supplement current therapeutic approaches for a “functional” cure. Current efforts toward HIV eradication to enhance immune recognition and elimination of persistently infected cells have highlighted the need for an optimized “kill” approach. Natural killer (NK) cells play an important role in antiviral defense and by virtue of their innate and adaptive features hold great promise as a focus of “kill” efforts. Galvanized by advances in the cancer field, NK cell exploitation, represents a transformative approach to augment HIV therapeutic modalities, circumventing many of the limitations inherent to T cell approaches. In this review we will discuss recent advances in our understanding of the development of NK cell adaptive/memory responses in HIV infection and highlight new and exciting opportunities to exploit the beneficial attributes of NK cells for HIV immunotherapy.

The Potential of Immune Modulation in Therapeutic HIV-1 Vaccination

We discuss here some of the key immunological elements that are at the crossroads and need to be combined to develop a potent therapeutic HIV-1 vaccine. Therapeutic vaccines have been commonly used to enhance and/or recall pre-existing HIV-1-specific cell-mediated immune responses aiming to suppress virus replication. The current success of immune checkpoint blockers in cancer therapy renders them very attractive to use in HIV-1 infected individuals with the objective to preserve the function of HIV-1-specific T cells from exhaustion and presumably target the persistent cellular reservoir. The major latest advances in our understanding of the mechanisms responsible for virus reactivation during therapy-suppressed individuals provide the scientific basis for future combinatorial therapeutic vaccine development.

Flattening the COVID-19 Curve With Natural Killer Cell Based Immunotherapies

Natural Killer (NK) cells are innate immune responders critical for viral clearance and immunomodulation. Despite their vital role in viral infection, the contribution of NK cells in fighting SARS-CoV-2 has not yet been directly investigated. Insights into pathophysiology and therapeutic opportunities can therefore be inferred from studies assessing NK cell phenotype and function during SARS, MERS, and COVID-19. These studies suggest a reduction in circulating NK cell numbers and/or an exhausted phenotype following infection and hint toward the dampening of NK cell responses by coronaviruses. Reduced circulating NK cell levels and exhaustion may be directly responsible for the progression and severity of COVID-19. Conversely, in light of data linking inflammation with coronavirus disease severity, it is necessary to examine NK cell potential in mediating immunopathology. A common feature of coronavirus infections is that significant morbidity and mortality is associated with lung injury and acute respiratory distress syndrome resulting from an exaggerated immune response, of which NK cells are an important component. In this review, we summarize the current understanding of how NK cells respond in both early and late coronavirus infections, and the implication for ongoing COVID-19 clinical trials. Using this immunological lens, we outline recommendations for therapeutic strategies against COVID-19 in clearing the virus while preventing the harm of immunopathological responses.

Transforming growth factor-β promotes the function of HIV-specific CXCR5+ CD8 T cells

HIV replication can be inhibited by CXCR5⁺ CD8 T cells (follicular cytotoxic T cell [TFC]) which transfer into B-cell follicles where latent HIV infection persists. However, how cytokines affect TFC remain unclear. Understanding which cytokines show the ability to affect TFC could be a key strategy toward curing HIV. Similar mechanisms could be used for the growth and transfer of TFCs and follicular helper T (TFH) cells; as a result, we hypothesized that cytokines IL-6, IL-21, and transforming growth factor-β (TGF-β), which are necessary for the differentiation of TFH cells, could also dictate the development of TFCs. In this work, lymph node mononuclear cells and peripheral blood mononuclear cells from HIV-infected individuals were cocultured with IL-6, IL-21, and TGF-β. We then carried out T-cell receptor (TCR) repertoire analysis to compare the differences between CXCR5^- and CXCR5⁺ CD8 T cells. Our results showed that the percentage and function of TFC can be enhanced by stimulation with TGF-β. Besides, TGF-β stimulation enhanced the diversity of TCR and complementarity-determining region 3 sequences. HIV DNA showed a negative correlation with TFC. The use of TGF-β to promote the expression of CXCR5⁺ CD8 T cells could become a new treatment approach for curing HIV.

Altered Cervical Mucosal Gene Expression and Lower Interleukin 15 Levels in Women With Schistosoma haematobium Infection but Not in Women With Schistosoma mansoni Infection

BACKGROUND

Schistosomiasis increases the risk of human immunodeficiency virus (HIV) acquisition in women by mechanisms that are incompletely defined. Our objective was to determine how the cervical environment is impacted by Schistosoma haematobium or Schistosoma mansoni infection by quantifying gene expression in the cervical mucosa and cytokine levels in cervicovaginal lavage fluid.

METHODS

We recruited women with and those without S. haematobium infection and women with and those without S. mansoni infection from separate villages in rural Tanzania with high prevalences of S. haematobium and S. mansoni, respectively. Infection status was determined by urine and stool microscopy and testing for serum circulating anodic antigen. RNA was extracted from cervical cytobrush samples for transcriptome analysis. Cytokine levels were measured by magnetic bead immunoassay.

RESULTS

In the village where S. haematobium was prevalent, 110 genes were differentially expressed in the cervical mucosa of 18 women with versus 39 without S. haematobium infection. Among the 27 cytokines analyzed in cervicovaginal lavage fluid from women in this village, the level of interleukin 15 was lower in the S. haematobium-infected group (62.8 vs 102.9 pg/mL; adjusted P = .0013). Differences were not observed in the S. mansoni-prevalent villages between 11 women with and 29 without S. mansoni infection.

CONCLUSIONS

We demonstrate altered cervical mucosal gene expression and lower interleukin 15 levels in women with S. haematobium infection as compared to those with S. mansoni infection, which may influence HIV acquisition and cancer risks. Studies to determine the effects of antischistosome treatment on these mucosal alterations are needed.

The human IL-15 superagonist N-803 promotes migration of virus-specific CD8+ T and NK cells to B cell follicles but does not reverse latency in ART-suppressed, SHIV-infected macaques

Despite the success of antiretroviral therapy (ART) to halt viral replication and slow disease progression, this treatment is not curative and there remains an urgent need to develop approaches to clear the latent HIV reservoir. The human IL-15 superagonist N-803 (formerly ALT-803) is a promising anti-cancer biologic with potent immunostimulatory properties that has been extended into the field of HIV as a potential "shock and kill" therapeutic for HIV cure. However, the ability of N-803 to reactivate latent virus and modulate anti-viral immunity in vivo under the cover of ART remains undefined. Here, we show that in ART-suppressed, simian-human immunodeficiency virus (SHIV)SF162P3-infected rhesus macaques, subcutaneous administration of N-803 activates and mobilizes both NK cells and SHIV-specific CD8+ T cells from the peripheral blood to lymph node B cell follicles, a sanctuary site for latent virus that normally excludes such effector cells. We observed minimal activation of memory CD4+ T cells and no increase in viral RNA content in lymph node resident CD4+ T cells post N-803 administration. Accordingly, we found no difference in the number or magnitude of plasma viremia timepoints between treated and untreated animals during the N-803 administration period, and no difference in the size of the viral DNA cell-associated reservoir post N-803 treatment. These results substantiate N-803 as a potent immunotherapeutic candidate capable of activating and directing effector CD8+ T and NK cells to the B cell follicle during full ART suppression, and suggest N-803 must be paired with a bona fide latency reversing agent in vivo to facilitate immune-mediated modulation of the latent viral reservoir.

Potential of the NKG2D/NKG2DL Axis in NK Cell-Mediated Clearance of the HIV-1 Reservoir

Viral persistency in latently infected CD4⁺ T cells despite antiretroviral therapy (ART) represents a major drawback in the fight against HIV-1. Efforts to purge latent HIV-1 have been attempted using latency reversing agents (LRAs) that activate expression of the quiescent virus. However, initial trials have shown that immune responses of ART-treated patients are ineffective at clearing LRA-reactivated HIV-1 reservoirs, suggesting that an adjuvant immunotherapy is needed. Here we overview multiple lines of evidence indicating that natural killer (NK) cells have the potential to induce anti-HIV-1 responses relevant for virus eradication. In particular, we focus on the role of the NKG2D activating receptor that crucially enables NK cell-mediated killing of HIV-1-infected cells. We describe recent data indicating that LRAs can synergize with HIV-1 at upregulating ligands for NKG2D (NKG2DLs), hence sensitizing T cells that exit from viral latency for recognition and lysis by NK cells; in addition, we report in vivo and ex vivo data showing the potential benefits and drawbacks that LRAs may have on NKG2D expression and, more in general, on the cytotoxicity of NK cells. Finally, we discuss how the NKG2D/NKG2DLs axis can be exploited for the development of effective HIV-1 eradication strategies combining LRA-induced virus reactivation with recently optimized NK cell-based immunotherapies.

Establishment of a Novel Humanized Mouse Model To Investigate In Vivo Activation and Depletion of Patient-Derived HIV Latent Reservoirs

Curing HIV infection has been thwarted by the persistent reservoir of latently infected CD4⁺ T cells, which reinitiate systemic infection after antiretroviral therapy (ART) interruption. To evaluate reservoir depletion strategies, we developed a novel preclinical in vivo model consisting of immunodeficient mice intrasplenically injected with peripheral blood mononuclear cells (PBMC) from long-term ART-suppressed HIV-infected donors. In the absence of ART, these mice developed rebound viremia which, 2 weeks after PBMC injection, was 1,000-fold higher (mean = 9,229,281 HIV copies/ml) in mice injected intrasplenically than in mice injected intraperitoneally (mean = 6,838 HIV copies/ml) or intravenously (mean = 591 HIV copies/ml). One week after intrasplenic PBMC injection, in situ hybridization of the spleen demonstrated extensive disseminated HIV infection, likely initiated from in vivo-reactivated primary latently infected cells. The time to viremia was delayed significantly by treatment with a broadly neutralizing antibody, 10-1074, compared to treatment with 10-1074-FcR^null, suggesting that 10-1074 mobilized Fc-mediated effector mechanisms to deplete the replication-competent reservoir. This was supported by phylogenetic analysis of Env sequences from viral-outgrowth cultures and untreated, 10-1074-treated, or 10-1074-FcR^null-treated mice. The predominant sequence cluster detected in viral-outgrowth cultures and untreated mouse plasma was significantly reduced in the plasma of 10-1074-treated mice, whereas two new clusters emerged that were not detected in viral-outgrowth cultures or plasma from untreated mice. These new clusters lacked mutations associated with 10-1074 resistance. Taken together, these data indicated that 10-1074 treatment depletes the reservoir of latently infected cells harboring replication competent HIV. Furthermore, this mouse model represents a new in vivo approach for the preclinical evaluation of new HIV cure strategies.IMPORTANCE Sustained remission of HIV infection is prevented by a persistent reservoir of latently infected cells capable of reinitiating systemic infection and viremia. To evaluate strategies to reactivate and deplete this reservoir, we developed and characterized a new humanized mouse model consisting of highly immunodeficient mice intrasplenically injected with peripheral blood mononuclear cells from long-term ART-suppressed HIV-infected donors. Reactivation and dissemination of HIV infection was visualized in the mouse spleens in parallel with the onset of viremia. The applicability of this model for evaluating reservoir depletion treatments was demonstrated by establishing, through delayed time to viremia and phylogenetic analysis of plasma virus, that treatment of these humanized mice with a broadly neutralizing antibody, 10-1074, depleted the patient-derived population of latently infected cells. This mouse model represents a new in vivo approach for the preclinical evaluation of new HIV cure strategies.

Therapeutic HIV-1 vaccine: time for immunomodulation and combinatorial strategies

PURPOSE OF REVIEW

The purpose is to recall some of the key immunological elements that are at the crossroad and need to be combined for developing a potent therapeutic HIV-1 vaccine.

RECENT FINDINGS

Therapeutic vaccines and cytokines have been commonly used to enhance and/or recall preexisting HIV-1 specific cell-mediated immune responses aiming to suppress virus replication. While the vaccine is important to stimulate HIV-1 specific T-cell responses, the cytokine may support the expansion of the stimulated virus-specific T cells. Moreover, the current success of immune checkpoint blockers in cancer therapy render them very attractive to use in HIV-1 infected individuals, with the objective to preserve the function of HIV-specific T cells from exhaustion and target directly HIV-1 cell reservoir. More recently, the development of passive immunotherapy using broad neutralizing HIV antibodies (bNAbs) and their potential capacity to elicit innate or adaptive HIV-cellular responses, beyond their neutralizing activity, offers a new opportunity to improve the efficiency of therapeutic vaccine. These major advances provide the scientific basis for developing potent combinatorial interventions in HIV-1 infected patients.

SUMMARY

Major advances in our immunological understanding resulting from basic science and clinical trials studies have paved the way and established a solid platform to jump over the stumbling blocks that prevent the field from developing a therapeutic HIV-1 vaccine. It is time for immuno-modulation and combinatorial strategies towards HIV-1 eradication.

Interferon Alpha Enhances NK Cell Function and the Suppressive Capacity of HIV-Specific CD8+ T Cells

Current shock-and-kill strategies for the eradication of the HIV-1 reservoir have resulted in blips of viremia but not in a decrease in the size of the latent reservoir in patients on suppressive antiretroviral therapy (ART). This discrepancy could potentially be explained by an inability of the immune system to kill HIV-1-infected cells following the reversal of latency. Furthermore, some studies have suggested that certain latency-reversing agents (LRAs) may inhibit CD8⁺ T cell and natural killer (NK) cell responses. In this study, we tested the hypothesis that alpha interferon (IFN-α) could improve the function of NK cells from chronic progressors (CP) on ART. We show here that IFN-α treatment enhanced cytokine secretion, polyfunctionality, degranulation, and the cytotoxic potential of NK cells from healthy donors (HD) and CP. We also show that this cytokine enhanced the viral suppressive capacity of NK cells from HD and elite controllers or suppressors. Furthermore, IFN-α enhanced global CP CD8⁺ T cell cytokine responses and the suppressive capacity of ES CD8⁺ T cells. Our data suggest that IFN-α treatment may potentially be used as an immunomodulatory agent in HIV-1 cure strategies.IMPORTANCE Data suggest that HIV⁺ individuals unable to control infection fail to do so due to impaired cytokine production and/cytotoxic effector cell function. Consequently, the success of cure agendas such as the shock-and-kill strategy will probably depend on enhancing patient effector cell function. In this regard, NK cells are of particular interest since they complement the function of CD8⁺ T cells. Here, we demonstrate the ability of short-course alpha interferon (IFN-α) treatments to effectively enhance such effector functions in chronic progressor NK cells without inhibiting their general CD8⁺ T cell function. These results point to the possibility of exploring such short-course IFN-α treatments for the enhancement of effector cell function in HIV⁺ patients in future cure strategies.

Immunological responses against hepatitis B virus in human peripheral blood mononuclear cell-engrafted mice

It is well known that immune-mediated virus elimination is necessary for the treatment of HBV infection. Reconstitution of human immune cells in liver chimeric mice is warranted to understand the immunopathogenesis of HBV infection. Here, we report a new immunologically humanized mouse model with a human immune system via reconstitution of immunodeficient NOG-Iaβ/β2 m double KO mice, which are NOG mice that are deficient in both MHC class I and II (DKO-NOG mice), with human HLA-A2-positive peripheral blood mononuclear cells (PBMCs). After injection of PBMCs, the xenogeneic graft-versus-host disease observed in PBMC-engrafted NOG mice was prevented in PBMC-engrafted DKO-NOG mice. Liver damage was reduced, and the survival time was prolonged in human PBMC-engrafted DKO-NOG mice compared to those in the NOG mice. The expression levels of PD-1 and Tim-3 on human T cells from PBMC-engrafted DKO-NOG mice were lower than those from NOG mice. By induction of HBV-specific T cell responses, such as vaccination with HBc-derived, peptide-pulsed DCs, hydrodynamic injection of HBV vector and intrasplenic injection of HepG2.2.15, the number of HBc-derived, peptide-specific CTLs increased in PBMC-engrafted DKO-NOG mice. Moreover, the recombinant HBV vaccine resulted in the production of hepatitis B surface antibody in 50% of the vaccinated mice. The induction of HBV-specific immune responses could be established in the immunologically humanized mice.

In Vitro Exposure to Prostratin but Not Bryostatin-1 Improves Natural Killer Cell Functions Including Killing of CD4+ T Cells Harboring Reactivated Human Immunodeficiency Virus

In the attempt of purging the HIV-1 reservoir through the “shock-and-kill” strategy, it is important to select latency-reversing agents (LRAs) devoid of deleterious effects on the antiviral function of immune effector cells. Here, we investigated two LRAs with PKC agonist activity, prostratin (PRO) and bryostatin-1 (BRY), for their impact on the function of natural killer (NK) cells, the major effectors of innate immunity whose potential in HIV-1 eradication has emerged in recent clinical trials. Using NK cells of healthy donors, we found that exposure to either PRO or BRY potently activated NK cells, resulting in upmodulation of NKG2D and NKp44 activating receptors and matrix metalloprotease-mediated shedding of CD16 receptor. Despite PRO and BRY affected NK cell phenotype in the same manner, their impact on NK cell function was diverse and showed considerable donor-to-donor variation. Altogether, in most tested donors, the natural cytotoxicity and antibody-dependent cellular cytotoxicity (ADCC) of NK cells were either improved or maintained by PRO, while both activities were impaired by BRY. Moreover, we analyzed the effect of these drugs on the capacity of treated NK cells to kill autologous latently infected CD4⁺ T cells reactivated via the same treatment. First, we found that PRO but not BRY increased upmodulation of the ULBP2 ligand for NKG2D on reactivated p24⁺ cells. Importantly, we showed that clearance of reactivated p24⁺ cells by NK cells was enhanced when both targets and effectors were exposed to PRO but not to BRY. Overall, PRO had a superior potential compared with BRY as to the impact on key NK cell functions and on NK-cell-mediated clearance of the HIV-1 reservoir. Our results emphasize the importance of considering the effects on NK cells of candidate “shock-and-kill” interventions. With respect to combinative approaches, the impact on NK cells of each LRA should be re-evaluated upon combination with a second LRA, which may have analogous or opposite effects, or with immunotherapy targeting NK cells. In addition, avoiding co-administration of LRAs that negatively impact ADCC activity by NK cells might be essential for successful application of antibodies or vaccination to “shock-and-kill” strategies.