HIV-1-Specific Chimeric Antigen Receptors Based on Broadly Neutralizing Antibodies

The enchanting canvas of CAR technology: Unveiling its wonders in non-neoplastic diseases

Chimeric antigen receptor (CAR) T cells have made a groundbreaking advancement in personalized immunotherapy and achieved widespread success in hematological malignancies. As CAR technology continues to evolve, numerous studies have unveiled its potential far beyond the realm of oncology. This review focuses on the current applications of CAR-based cellular platforms in non-neoplastic indications, such as autoimmune, infectious, fibrotic, and cellular senescence-associated diseases. Furthermore, we delve into the utilization of CARs in non-T cell populations such as natural killer (NK) cells and macrophages, highlighting their therapeutic potential in non-neoplastic conditions and offering the potential for targeted, personalized therapies to improve patient outcomes and enhanced quality of life.

Harnessing natural killer cells to target HIV-1 persistence

PURPOSE OF REVIEW

The purpose of this article is to review recent advances in the role of natural killer (NK) cells in approaches aimed at reducing the latent HIV-1 reservoir.

RECENT FINDINGS

Multiple approaches to eliminate cells harboring latent HIV-1 are being explored, but have been met with limited success so far. Recent studies have highlighted the role of NK cells and their potential in HIV-1 cure efforts. Anti-HIV-1 NK cell function can be optimized by enhancing NK cell activation, antibody dependent cellular cytotoxicity, reversing inhibition of NK cells as well as by employing immunotherapeutic complexes to enable HIV-1 specificity of NK cells. While NK cells alone do not eliminate the HIV-1 reservoir, boosting NK cell function might complement other strategies involving T cell and B cell immunity towards an HIV-1 functional cure.

SUMMARY

Numerous studies focusing on targeting latently HIV-1-infected cells have emphasized a potential role of NK cells in these strategies. Our review highlights recent advances in harnessing NK cells in conjunction with latency reversal agents and other immunomodulatory therapeutics to target HIV-1 persistence.

Application of chimeric antigen receptor therapy beyond oncology: A bibliometric and visualized analysis

PURPOSE

Chimeric antigen receptor therapy beyond oncology has gained increasing attention. While a substantial number of publications have emerged in recent years, there has been a paucity of conducted bibliometric studies. Our objective is to systematically summarize and visually analyze the literature in the field of chimeric antigen receptors therapy beyond oncology and explore hotspots in this field.

METHODS

Web of Science Core Collection was selected as the data source, and the data was retrieved on December 23, 2022, according to the search strategy. CiteSpace 6.1.R6 and Vosviewer 1.6.18 were used to analyze publications and explore research hotspots and directions.

RESULTS

A total of 338 publications written by 1832 authors from 516 institutions in 42 countries/regions were selected for the analysis. The number of publications is steadily increasing annually. The United States emerged as the primary contributor, and University of Pennsylvania was the leading institution. Frontiers in Immunology boasted the highest number of published papers. Kitchen SG, Riley JL, and Scott DW were the most productive researchers in this field. The keyword cluster analysis identified HIV, autoimmune diseases, transplant related diseases and COVID-19 as the primary focus areas within the realm of chimeric antigen receptor therapy beyond oncology.

CONCLUSION

The advancement of chimeric antigen receptor therapy beyond oncology has witnessed rapid progress in recent years. We have explored the hotspots and research directions in this field. It is hoped that this study could provide references and directions for future clinical researches.

Is the Central Nervous System Reservoir a Hurdle for an HIV Cure?

There is currently no cure for HIV infection although adherence to effective antiretroviral therapy (ART) suppresses replication of the virus in blood, increases CD4+ T-cell counts, reverses immunodeficiency, and increases life expectancy. Despite these substantial advances, ART is a lifelong treatment for people with HIV (PWH) and upon cessation or interruption, the virus quickly rebounds in plasma and anatomic sites, including the central nervous system (CNS), resulting in disease progression. With recent advances in quantifying viral burden, detection of genetically intact viral genomes, and isolation of replication-competent virus from brain tissues of PWH receiving ART, it has become apparent that the CNS viral reservoir (largely comprised of macrophage type cells) poses a substantial challenge for HIV cure strategies. Other obstacles impacting the curing of HIV include ageing populations, substance use, comorbidities, limited antiretroviral drug efficacy in CNS cells, and ART-associated neurotoxicity. Herein, we review recent findings, including studies of the proviral integration sites, reservoir decay rates, and new treatment/prevention strategies in the context of the CNS, together with highlighting the next steps for investigations of the CNS as a viral reservoir.

Broadly neutralizing antibodies targeting HIV: Progress and challenges

Anti-HIV broadly neutralizing antibodies (bNAbs) offer a novel approach to treating, preventing, or curing HIV. Pre-clinical models and clinical trials involving the passive transfer of bNAbs have demonstrated that they can control viremia and potentially serve as alternatives or complement antiretroviral therapy (ART). However, antibody decay, persistent latent reservoirs, and resistance impede bNAb treatment. This review discusses recent advancements and obstacles in applying bNAbs and proposes strategies to enhance their therapeutic potential. These strategies include multi-epitope targeting, antibody half-life extension, combining with current and newer antiretrovirals, and sustained antibody secretion.

Targeting the HIV reservoir: chimeric antigen receptor therapy for HIV cure

ABSTRACT

Although antiretroviral therapy (ART) can reduce the viral load in the plasma to undetectable levels in human immunodeficiency virus (HIV)-infected individuals, ART alone cannot completely eliminate HIV due to its integration into the host cell genome to form viral reservoirs. To achieve a functional cure for HIV infection, numerous preclinical and clinical studies are underway to develop innovative immunotherapies to eliminate HIV reservoirs in the absence of ART. Early studies have tested adoptive T-cell therapies in HIV-infected individuals, but their effectiveness was limited. In recent years, with the technological progress and great success of chimeric antigen receptor (CAR) therapy in the treatment of hematological malignancies, CAR therapy has gradually shown its advantages in the field of HIV infection. Many studies have identified a variety of HIV-specific CAR structures and types of cytolytic effector cells. Therefore, CAR therapy may be beneficial for enhancing HIV immunity, achieving HIV control, and eliminating HIV reservoirs, gradually becoming a promising strategy for achieving a functional HIV cure. In this review, we provide an overview of the design of anti-HIV CAR proteins, the cell types of anti-HIV CAR (including CAR T cells, CAR natural killer cells, and CAR-encoding hematopoietic stem/progenitor cells), the clinical application of CAR therapy in HIV infection, and the prospects and challenges in anti-HIV CAR therapy for maintaining viral suppression and eliminating HIV reservoirs.

Strategies for enhancing CAR T cell expansion and persistence in HIV infection

Chimeric Antigen Receptor (CAR) T cell therapies are tremendously successful in hematological malignancies and show great promise as treatment and curative strategy for HIV. A major determinant for effective CAR T cell therapy is the persistence of CAR T cells. Particularly, antigen density and target cell abundance are crucial for the engagement, engraftment, and persistence of CAR T cells. The success of HIV-specific CAR T cells is challenged by limited antigen due to low cell surface expression of viral proteins and the scarcity of chronically infected cells during antiretroviral therapy. Several strategies have been explored to increase the efficacy of CAR T cells by enhancing expansion and persistence of the engineered cells. This review highlights the challenges of designing CAR T cells against HIV and other chronic viral infections. We also discuss potential strategies to enhance CAR T cell expansion and persistence in the setting of low antigen exposure.

Humanized Mice for Studies of HIV-1 Persistence and Elimination

A major roadblock to achieving a cure for human immunodeficiency virus type one (HIV-1) is the persistence of latent viral infections in the cells and tissue compartments of an infected human host. Latent HIV-1 proviral DNA persists in resting memory CD4+ T cells and mononuclear phagocytes (MPs; macrophages, microglia, and dendritic cells). Tissue viral reservoirs of both cell types reside in the gut, lymph nodes, bone marrow, spleen, liver, kidney, skin, adipose tissue, reproductive organs, and brain. However, despite the identification of virus-susceptible cells, several limitations persist in identifying broad latent reservoirs in infected persons. The major limitations include their relatively low abundance, the precise identification of latently infected cells, and the lack of biomarkers for identifying latent cells. While primary MP and CD4+ T cells and transformed cell lines are used to interrogate mechanisms of HIV-1 persistence, they often fail to accurately reflect the host cells and tissue environments that carry latent infections. Given the host specificity of HIV-1, there are few animal models that replicate the natural course of viral infection with any precision. These needs underlie the importance of humanized mouse models as both valuable and cost-effective tools for studying viral latency and subsequently identifying means of eliminating it. In this review, we discuss the advantages and limitations of humanized mice for studies of viral persistence and latency with an eye toward using these models to test antiretroviral and excision therapeutics. The goals of this research are to use the models to address how and under which circumstances HIV-1 latency can be detected and eliminated. Targeting latent reservoirs for an ultimate HIV-1 cure is the task at hand.

Challenges in HIV-1 Latent Reservoir and Target Cell Quantification in CAR-T Cell and Other Lentiviral Gene Modifying HIV Cure Strategies

Gene-modification therapies are at the forefront of HIV-1 cure strategies. Chimeric antigen receptor (CAR)-T cells pose a potential approach to target infected cells during antiretroviral therapy or following analytical treatment interruption (ATI). However, there are technical challenges in the quantification of HIV-1-infected and CAR-T cells in the setting of lentiviral CAR gene delivery and also in the identification of cells expressing target antigens. First, there is a lack of validated techniques to identify and characterize cells expressing the hypervariable HIV gp120 in both ART-suppressed and viremic individuals. Second, close sequence homology between lentiviral-based CAR-T gene modification vectors and conserved regions of HIV-1 creates quantification challenges of HIV-1 and lentiviral vector levels. Consideration needs to be taken into standardizing HIV-1 DNA/RNA assays in the setting of CAR-T cell and other lentiviral vector-based therapies to avoid these confounding interactions. Lastly, with the introduction of HIV-1 resistance genes in CAR-T cells, there is a need for assays with single-cell resolution to determine the competence of the gene inserts to prevent CAR-T cells from becoming infected in vivo. As novel therapies continue to arise in the HIV-1 cure field, resolving these challenges in CAR-T-cell therapy will be crucial.

Chimeric antigen receptor-based therapies beyond cancer

Adoptive cell transfer (ACT) therapies have gained renewed interest in the field of immunotherapy following the advent of chimeric antigen receptor (CAR) technology. This immunological breakthrough requires immune cell engineering with an artificial surface protein receptor for antigen-specific recognition coupled to an intracellular protein domain for cell activating functions. CAR-based ACT has successfully solved some hematological malignancies, and it is expected that other tumors may soon benefit from this approach. However, the potential of CAR technology is such that other immune-mediated disorders are beginning to profit from it. This review will focus on CAR-based ACT therapeutic areas other than oncology such as infection, allergy, autoimmunity, transplantation, and fibrotic repair. Herein, we discuss the results and limitations of preclinical and clinical studies in that regard.

Allogeneic gene-edited HIV-specific CAR-T cells secreting PD-1 blocking scFv enhance specific cytotoxic activity against HIV Env+ cells invivo

HIV-specific chimeric antigen receptor (CAR) T-cells have been developed to target HIV-1 infected CD4⁺ T-cells that express HIV Env proteins. However, T cell exhaustion and the patient-specific autologous paradigm of CAR-T cell hurdled clinical applications. Here, we created HIV-specific CAR-T cells using human peripheral blood mononuclear cells and a 3BNC117-E27 (3BE) CAR construct that enabled the expression of programmed cell death protein (PD-1) -blocking scFv E27 and the single-chain variable fragment of the HIV-1-specific broadly neutralizing antibody 3BNC117 to target native HIV Env. Compared with T cells expressing 3BNC117-CAR alone, 3BE CAR-T cells showed greater cytotoxic activity against HIV Env⁺ cells with stronger proliferation capability, higher killing efficiency, and enhanced cytokine secretion in the presence of HIV Env-expressing cells. Furthermore, we manufactured TCR-deficient 3BE CAR-T cells through gene editing and demonstrated that these CAR-T cells could effectively kill HIV Env ​⁺ ​cells in vivo without the occurrence of severe graft-versus-host disease (GvHD) in NSG mice. These data suggest that we have provided a feasible approach to the generation of "off-the-shelf" anti-HIV CAR-T cells in combination with PD-1 checkpoint blockade immunotherapy, which can be a powerful therapeutic candidate for the functional cure of HIV.

Development of HIV-Resistant CAR T Cells by CRISPR/Cas-Mediated CAR Integration into the CCR5 Locus

Adoptive immunotherapy using chimeric antigen receptor (CAR) T cells has been highly successful in treating B cell malignancies and holds great potential as a curative strategy for HIV infection. Recent advances in the use of anti-HIV broadly neutralizing antibodies (bNAbs) have provided vital information for optimal antigen targeting of CAR T cells. However, CD4+ CAR T cells are susceptible to HIV infection, limiting their therapeutic potential. In the current study, we engineered HIV-resistant CAR T cells using CRISPR/Cas9-mediated integration of a CAR cassette into the CCR5 locus. We used a single chain variable fragment (scFv) of the clinically potent bNAb 10-1074 as the antigen-targeting domain in our anti-HIV CAR T cells. Our anti-HIV CAR T cells showed specific lysis of HIV-infected cells in vitro. In a PBMC humanized mouse model of HIV infection, the anti-HIV CAR T cells expanded and transiently limited HIV infection. In conclusion, this study provides proof-of-concept for developing HIV-resistant CAR T cells using CRISPR/Cas9 targeted integration.

Safety and durability of AGT103-T autologous T cell therapy for HIV infection in a Phase 1 trial

The cell and gene therapy product AGT103-T was designed to restore the Gag-specific CD4+ T cell response in persons with chronic HIV disease who are receiving antiretroviral therapy. This autologous, genetically engineered cell product is under investigation in a Phase 1 clinical trial (NCT03215004). Trial participants were conditioned with cyclophosphamide approximately 1 week before receiving a one-time low (< 109 genetically modified CD4+ T cells) or high (≥109 genetically modified CD4+ T cells) dose of AGT103-T, delivering between 2 and 21 million genetically modified cells per kilogram (kg) body weight. There were no serious adverse events (SAEs) and all adverse events (AEs) were mild. Genetically modified AGT103-T cells were detected in most of the participant blood samples collected 6 months after infusion, which was the last scheduled monitoring visit. Peripheral blood mononuclear cells (PBMC) collected after cell product infusion were tested to determine the abundance of Gag-specific T cells as a measure of objective responses to therapy. Gag-specific CD4+ T cells were detected in all treated individuals and were substantially increased by 9 to 300-fold compared to baseline, by 14 days after cell product infusion. Gag-specific CD8+ T cells were increased by 1.7 to 10-fold relative to baseline, by 28 days after cell product infusion. Levels of Gag-specific CD4+ T cells remained high (~2 to 70-fold higher relative to baseline) throughout 3-6 months after infusion. AGT103-T at low or high doses was safe and effective for improving host T cell immunity to HIV. Further studies, including antiretroviral treatment interruption, are warranted to evaluate the product's efficacy in HIV disease.

CLINICAL TRIAL REGISTRATION

www.clinicaltrials.gov, identifier: NCT03215004.

Stem-like T cells and niches: Implications in human health and disease

Recently, accumulating evidence has elucidated the important role of T cells with stem-like characteristics in long-term maintenance of T cell responses and better patient outcomes after immunotherapy. The fate of TSL cells has been correlated with many physiological and pathological human processes. In this review, we described present advances demonstrating that stem-like T (TSL) cells are central players in human health and disease. We interpreted the evolutionary characteristics, mechanism and functions of TSL cells. Moreover, we discuss the import role of distinct niches and how they affect the stemness of TSL cells. Furthermore, we also outlined currently available strategies to generate TSL cells and associated affecting factors. Moreover, we summarized implication of TSL cells in therapies in two areas: stemness enhancement for vaccines, ICB, and adoptive T cell therapies, and stemness disruption for autoimmune disorders.

Advances in HIV-1-specific chimeric antigen receptor cells to target the HIV-1 reservoir

Antiretroviral therapy (ART) for HIV-1 has dramatically improved outcomes for people living with HIV-1 but requires life-long adherence and can be associated with short and long-term toxicity. Numerous pre-clinical and clinical investigations are underway to develop therapies for immune control of HIV-1 in the absence of ART. The success of chimeric antigen receptor (CAR) cell therapy for hematological malignancy has renewed efforts to develop and investigate CAR cells as strategies to enhance HIV-1 immunity, enable virus control or elimination, and allow ART-free HIV-1 remission. Here, we review the improvements in anti-HIV-1 CAR cell therapy in the two decades since their initial clinical trials were conducted, describe the additional engineering required to protect CAR cells from HIV-1 infection, and preview the current landscape of CAR cell therapies advancing to HIV-1 clinical trials.

Insights Into Persistent HIV-1 Infection and Functional Cure: Novel Capabilities and Strategies

Although HIV-1 replication can be efficiently suppressed to undetectable levels in peripheral blood by combination antiretroviral therapy (cART), lifelong medication is still required in people living with HIV (PLWH). Life expectancies have been extended by cART, but age-related comorbidities have increased which are associated with heavy physiological and economic burdens on PLWH. The obstacle to a functional HIV cure can be ascribed to the formation of latent reservoir establishment at the time of acute infection that persists during cART. Recent studies suggest that some HIV reservoirs are established in the early acute stages of HIV infection within multiple immune cells that are gradually shaped by various host and viral mechanisms and may undergo clonal expansion. Early cART initiation has been shown to reduce the reservoir size in HIV-infected individuals. Memory CD4+ T cell subsets are regarded as the predominant cellular compartment of the HIV reservoir, but monocytes and derivative macrophages or dendritic cells also play a role in the persistent virus infection. HIV latency is regulated at multiple molecular levels in transcriptional and post-transcriptional processes. Epigenetic regulation of the proviral promoter can profoundly regulate the viral transcription. In addition, transcriptional elongation, RNA splicing, and nuclear export pathways are also involved in maintaining HIV latency. Although most proviruses contain large internal deletions, some defective proviruses may induce immune activation by expressing viral proteins or producing replication-defective viral-like particles. In this review article, we discuss the state of the art on mechanisms of virus persistence in the periphery and tissue and summarize interdisciplinary approaches toward a functional HIV cure, including novel capabilities and strategies to measure and eliminate the infected reservoirs and induce immune control.

Engineered Zinc Finger Protein Targeting 2LTR Inhibits HIV Integration in Hematopoietic Stem and Progenitor Cell-Derived Macrophages: In Vitro Study

Human hematopoietic stem/progenitor cell (HSPC)-based gene therapy is a promising direction for curing HIV-1-infected individuals. The zinc finger protein (2LTRZFP) designed to target the 2-LTR-circle junction of HIV-1 cDNA was previously reported as an intracellular antiviral molecular scaffold that prevents HIV integration. Here, we elucidate the efficacy and safety of using 2LTRZFP in human CD34⁺ HSPCs. We transduced 2LTRZFP which has the mCherry tag (2LTRZFPmCherry) into human CD34⁺ HSPCs using a lentiviral vector. The 2LTRZFPmCherry-transduced HSPCs were subsequently differentiated into macrophages. The expression levels of pro-apoptotic proteins of the 2LTRZFPmCherry-transduced HSPCs showed no significant difference from those of the non-transduced control. Furthermore, the 2LTRZFPmCherry-transduced HSPCs were successfully differentiated into mature macrophages, which had normal phagocytic function. The cytokine secretion assay demonstrated that 2LTRZFPmCherry-transduced CD34⁺ derived macrophages promoted the polarization towards classically activated (M1) subtypes. More importantly, the 2LTRZFPmCherry transduced cells significantly exhibited resistance to HIV-1 integration in vitro. Our findings demonstrate that the 2LTRZFPmCherry-transduced macrophages were found to be functionally and phenotypically normal, with no adverse effects of the anti-HIV-1 scaffold. Our data suggest that the anti-HIV-1 integrase scaffold is a promising antiviral molecule that could be applied to human CD34⁺ HSPC-based gene therapy for AIDS patients.

Exploring the application of immunotherapy against HIV infection in the setting of malignancy: A detailed review article

According to the Joint United Nations Programme on HIV/AIDS (UNAIDS), as of 2019, approximately 42.2 million people have died from acquired immunodeficiency syndrome (AIDS)-related illnesses since the start of the epidemic. Antiretroviral therapy (ART) has significantly reduced mortality, morbidity, and incidence of the human immunodeficiency virus (HIV)/AIDS-defining cancers, taming once-dreaded disease into a benign chronic infection. Although the treatment has prolonged the patients' survival, general HIV prevalence has increased and this increase has dovetailed with an increasing incidence of Non-AIDS-defining cancers (NADCs) among people living with HIV (PLWH). This is happening when new promising approaches in both oncology and HIV infection are being developed. This review focuses on recent progress witnessed in immunotherapy approaches against HIV-related, Non-AIDS-defining cancers (NADCs), and HIV infection.

Therapeutic roles of CAR T cells in infectious diseases: Clinical lessons learnt from cancer

Cancer immunotherapy has made improvements due to the advances in chimaeric antigen receptor (CAR) T cell development, offering a promising treatment option for patients who have failed to respond to traditional treatments. In light of the successful use of adoptive CAR T cell therapy for cancer, researchers have been inspired to develop CARs for the treatment of other diseases beyond cancers such as viral infectious diseases. Nonetheless, various obstacles limit the efficacy of CAR T cell therapies and prevent their widespread usage. Severe toxicities, poor in vivo persistence, antigen escape, and heterogeneity, as well as off-target effect, are key challenges that must all be addressed to broaden the application of CAR T cells to a wider spectrum of diseases. The key advances in CAR T cell treatment for cancer and viral infections are reviewed in this article. We will also discuss revolutionary CAR T cell products developed to improve and enhance the therapeutic advantages of these treatments.

T Cell Engaging Immunotherapies, Highlighting Chimeric Antigen Receptor (CAR) T Cell Therapy

In the past decade, chimeric antigen receptor (CAR) T cell technology has revolutionized cancer immunotherapy. This strategy uses synthetic CARs to redirect the patient's own immune cells to recognize specific antigens expressed on the surface of tumor cells. The unprecedented success of anti-CD19 CAR T cell therapy against B cell malignancies has resulted in its approval by the US Food and Drug Administration (FDA) in 2017. However, major scientific challenges still remain to be addressed for the broad use of CAR T cell therapy. These include severe toxicities, limited efficacy against solid tumors, and immune suppression in the hostile tumor microenvironment. Furthermore, CAR T cell therapy is a personalized medicine of which the production is time- and resource-intensive, which makes it very expensive. All these factors drive new innovations to engineer more powerful CAR T cells with improved antitumor activity, which are reviewed in this manuscript.

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.

Immune inactivation of anti-simian immunodeficiency virus chimeric antigen receptor T cells in rhesus macaques

Chimeric antigen receptor (CAR) T cell therapies are being investigated as potential HIV cures and designed to target HIV reservoirs. Monoclonal antibodies (mAbs) targeting the simian immunodeficiency virus (SIV) envelope allowed us to investigate the potency of single-chain variable fragment (scFv)-based anti-SIV CAR T cells. In vitro, CAR T cells expressing the scFv to both the variable loop 1 (V1) or V3 of the SIV envelope were highly potent at eliminating SIV-infected T cells. However, in preclinical studies, in vivo infusion of these CAR T cells in rhesus macaques (RMs) resulted in lack of expansion and no detectable in vivo antiviral activity. Injection of envelope-expressing antigen-presenting cells (APCs) 1 week post-CAR T cell infusion also failed to stimulate CAR T cell expansion in vivo. To investigate this in vitro versus in vivo discrepancy, we examined host immune responses directed at CAR T cells. A humoral immune response against the CAR scFv was detected post-infusion of the anti-SIV CAR T cells; anti-SIV IgG antibodies present in plasma of SIV-infected animals were associated with inhibited CAR T cell effector functions. These data indicate that lack of in vivo expansion and efficacy of CAR T cells might be due to antibodies blocking the interaction between the CAR scFv and its epitope.

Challenges and Opportunities of Using Adoptive T-Cell Therapy as Part of an HIV Cure Strategy

HIV-infected individuals successfully controlling viral replication via antiretroviral therapy often have a compromised HIV-specific T-cell immune response due to the lack of CD4 T-cell help, viral escape, T-cell exhaustion, and reduction in numbers due to the withdrawal of cognate antigen. A successful HIV cure strategy will likely involve a durable and potent police force that can effectively recognize and eliminate remaining virus that may emerge decades after an individual undergoes an HIV cure regimen. T cells are ideally suited to serve in this role, but given the state of the HIV-specific T-cell response, it is unclear how to best restore HIV-specific T-cell activity prior initiation of a HIV cure strategy. Here, we review several strategies of generating HIV-specific T cells ex vivo that are currently being tested in the clinic and discuss how infused T cells can be part of an HIV cure strategy.

Broadly neutralizing antibody-derived CAR-T cells reduce viral reservoir in HIV-1-infected individuals

BACKGROUND

Chimeric antigen receptor (CAR)-modified T cells have emerged as a novel approach to treat malignant tumors. This strategy has also been proposed for the treatment of HIV-1 infection. We have developed a broadly neutralizing antibody (bNAb)-derived CAR-T cell therapy which can exerted specific cytotoxic activity against HIV-1-infected cells.

METHODS

We conducted an open-label trial of the safety, side-effect profile, pharmacokinetic properties, and antiviral activity of bNAb-derived CAR-T cell therapy in HIV-1-infected individuals who were undergoing analytical interruption of antiretroviral therapy (ART).

RESULTS

A total of 14 participants completed only a single administration of bNAb-derived CAR-T cells. CAR-T administration was safe and well tolerated. Six participants discontinued ART, and viremia rebound occurred in all of them, with a 5.3-week median time. Notably, the cell-associated viral RNA and intact proviruses decreased significantly after CAR-T treatment. Analyses of HIV-1 variants before or after CAR-T administration suggested that CAR-T cells exerted pressure on rebound viruses, resulting in a selection of viruses with less diversity and mutations against CAR-T-mediated cytotoxicity.

CONCLUSIONS

No safety concerns were identified with adoptive transfer of bNAb-derived CAR-T cells. They reduced viral reservoir. All the rebounds were due to preexisting or emergence of viral escape mutations.

TRIAL REGISTRATION

ClinicalTrials.gov number, NCT03240328.

FUNDING

Ministry of Science and Technology of China, National Natural Science Foundation of China, and Department of Science and Technology of Guangdong Province.

HIV-1-Specific CAR-T Cells With Cell-Intrinsic PD-1 Checkpoint Blockade Enhance Anti-HIV Efficacy in vivo

Adoptive cellular immunotherapy therapy using broadly neutralizing antibody-based chimeric antigen receptor-T cells (bNAb-based CAR-T) has shown great potency and safety for the functional cure of HIV. The efficacy of bNAb-based CAR-T cells could be compromised by adaptive resistance during HIV chronic infection according to the phenomenon that cellular exhaustion was observed in endogenous cytotoxic T-lymphocytes (CTLs) along with upregulated expression of PD−1. Here, we created HIV-specific CAR-T cells using human peripheral blood mononuclear cells (PBMCs) and a 3BNC117-DNR CAR (3BD CAR) construct that enables the expression of PD-1 dominant negative receptor (DNR) and the single-chain variable fragment of the HIV-1-specific broadly neutralizing antibody 3BNC117 to target native HIV envelope glycoprotein (Env). Compared with HIV CAR expression alone, 3BD CAR-T cells displayed potent lytic and functional responses to Env-expressing cell lines and HIV-infected CD4⁺ T cells. Moreover, 3BD CAR-T cells can kill HIV-latently-infected cell lines, which are reactivated by the secretory cytokines of effector cells followed by contact with initial HIV-expressing fraction. Furthermore, bioluminescence imaging indicated that 3BD CAR-T cells displayed superior anti-HIV function in an HIV NCG mouse model of transplanting Env⁺/PD-L1⁺ cells (LEL6). These studies suggested that our proposed combinational strategy of HIV CAR-T therapy with PD-1 blockade therapy is feasible and potent, making it a promising therapeutic candidate for HIV functional cure.

Evaluation of chimeric antigen receptor T cell therapy in non-human primates infected with SHIV or SIV

Achieving a functional cure is an important goal in the development of HIV therapy. Eliciting HIV-specific cellular immune responses has not been sufficient to achieve durable removal of HIV-infected cells due to the restriction on effective immune responses by mutation and establishment of latent reservoirs. Chimeric antigen receptor (CAR) T cells are an avenue to potentially develop more potent redirected cellular responses against infected T cells. We developed and tested a range of HIV- and SIV-specific chimeric antigen receptor (CAR) T cell reagents based on Env-binding proteins. In general, SHIV/SIV CAR T cells showed potent viral suppression in vitro, and adding additional CAR molecules in the same transduction resulted in more potent viral suppression than single CAR transduction. Importantly, the primary determinant of virus suppression potency by CAR was the accessibility to the Env epitope, and not the neutralization potency of the binding moiety. However, upon transduction of autologous T cells followed by infusion in vivo, none of these CAR T cells impacted either acquisition as a test of prevention, or viremia as a test of treatment. Our study illustrates limitations of the CAR T cells as possible antiviral therapeutics.

Chimeric Antigen Receptors Targeting Human Cytomegalovirus

Human cytomegalovirus (CMV) is a ubiquitous pathogen that causes significant morbidity in some vulnerable populations. Individualized adoptive transfer of ex vivo expanded CMV-specific CD8+ T cells has provided proof-of-concept that immunotherapy can be highly effective, but a chimeric antigen receptor (CAR) approach would provide a feasible method for broad application. We created 8 novel CARs using anti-CMV neutralizing antibody sequences, which were transduced via lentiviral vector into primary CD8+ T cells. All CARs were expressed. Activity against CMV-infected target cells was assessed by release of cytokines (interferon-γ and tumor necrosis factor-α), upregulation of surface CD107a, proliferation, cytolysis of infected cells, and suppression of viral replication. While some CARs showed varying functional activity across these assays, 1 CAR based on antibody 21E9 was consistently superior in all measures. These results support development of a CMV-specific CAR for therapeutic use against CMV and potentially other applications harnessing CMV-driven immunotherapies.

Immune System Investigation Using Parasitic Helminths

Coevolutionary adaptation between humans and helminths has developed a finely tuned balance between host immunity and chronic parasitism due to immunoregulation. Given that these reciprocal forces drive selection, experimental models of helminth infection are ideally suited for discovering how host protective immune responses adapt to the unique tissue niches inhabited by these large metazoan parasites. This review highlights the key discoveries in the immunology of helminth infection made over the last decade, from innate lymphoid cells to the emerging importance of neuroimmune connections. A particular emphasis is placed on the emerging areas within helminth immunology where the most growth is possible, including the advent of genetic manipulation of parasites to study immunology and the use of engineered T cells for therapeutic options. Lastly,we cover the status of human challenge trials with helminths as treatment for autoimmune disease, which taken together, stand to keep the study of parasitic worms at the forefront of immunology for years to come.

Genetic engineering of T cells for immunotherapy

Genetically engineered T cell immunotherapies have provided remarkable clinical success to treat B cell acute lymphoblastic leukaemia by harnessing a patient's own T cells to kill cancer, and these approaches have the potential to provide therapeutic benefit for numerous other cancers, infectious diseases and autoimmunity. By introduction of either a transgenic T cell receptor or a chimeric antigen receptor, T cells can be programmed to target cancer cells. However, initial studies have made it clear that the field will need to implement more complex levels of genetic regulation of engineered T cells to ensure both safety and efficacy. Here, we review the principles by which our knowledge of genetics and genome engineering will drive the next generation of adoptive T cell therapies.

Application of CAR-T Cell Therapy beyond Oncology: Autoimmune Diseases and Viral Infections

Adoptive cell transfer (ACT) has long been at the forefront of the battle with cancer that began last century with the therapeutic application of tumor-infiltrating lymphocytes (TILs) against melanoma. The development of novel ACT approaches led researchers and clinicians to highly efficient technologies based on genetically engineered T lymphocytes, with chimeric antigen receptor (CAR)-T cells as the most prominent example. CARs consist of an extracellular domain that represents the single-chain variable fragment (scFv) of a monoclonal antibody (mAb) responsible for target recognition and the intracellular domain, which was built from up to several signaling motifs that mediated T cell activation. The number of potential targets amenable for CAR-T cell therapy is expanding rapidly, which means that the tremendous success of this approach in oncology could be further translated to treating other diseases. In this review, we outlined modern trends and recent developments in CAR-T cell therapy from an unusual point of view by focusing on diseases beyond cancer, such as autoimmune disorders and viral infections, including SARS-CoV-2.

Conditionally Replicating Vectors Mobilize Chimeric Antigen Receptors against HIV

Human immunodeficiency virus (HIV) is an attractive target for chimeric antigen receptor (CAR) therapy. CAR T cells have proved remarkably potent in targeted killing of cancer cells, and we surmised that CAR T cells could prove useful in eradicating HIV-infected cells. Toward this goal, we interrogate several neutralizing single-chain variable fragments (scFvs) that target different regions of the HIV envelope glycoprotein, gp120. We find here that CAR T cells with scFv from NIH45-46 antibody demonstrated the highest cytotoxicity. Although NIH45-46 CAR T cells are capable of eliminating antigen-expressing cells, we wanted to address HIV reactivation from ex vivo culture of HIV patient-derived CAR T cells. In order to capitalize on the HIV reactivation, we developed a conditionally replicating lentiviral vector (crLV). The crLV can hijack HIV machinery, forming a chimeric lentivirus (LV) instead of HIV and delivered to uninfected cells. We find that CAR T cells generated with crLVs have similar CAR-mediated functionality as traditional CARs. We also demonstrate crLVs' capability of expanding CAR percentage and protecting CD4 CAR T cell in HIV donors. Collectively, we demonstrate here that the novel crLV NIH45-46 CAR can serve as a strategy to combat HIV, as well as overcome HIV reactivation in CD4⁺ CAR T cells.

Real-Time Killing Assays to Assess the Potency of a New Anti-Simian Immunodeficiency Virus Chimeric Antigen Receptor T Cell

The success of chimeric antigen receptor (CAR) T cell therapies for treating leukemia has resulted in a booming interest for the technology. Expression of a CAR in T cells allows redirection of their natural cytolytic activity toward cells presenting a specific designated surface antigen. Although CAR T cell therapies have thus far shown promising results mostly in B cell malignancy trials, interest in their potential to treat other diseases is on the rise, including using CAR T cells to control human immunodeficiency virus infection. The assessment of CAR T cell potency toward specific targets in vitro is a critical preclinical step. In this study, we describe novel assays that monitor the cytotoxicity of candidate CAR T cells toward simian immunodeficiency virus (SIV) infected CD4 T cells. The assays involve live cell imaging using a fluorescence microscopy system that records in real time the disappearance or appearance of targets infected with SIV carrying a fluorescent protein gene. The assays are highly reproducible, and their rapid turn around and reduced cost present a significant advance regarding the efficient preclinical evaluation of CAR T cell constructs and are broadly applicable to potential human diseases that could benefit from CAR T cell therapy.

CAR-T cells leave the comfort zone: current and future applications beyond cancer

Chimeric antigen receptor (CAR)-T cell therapy represents a breakthrough in the immunotherapy field and has achieved great success following its approval in 2017 for the treatment of B cell malignancies. While CAR-T cells are mostly applied as anti-tumor therapy in the present, their initial concept was aimed at a more general purpose of targeting membrane antigens, thus translating in many potential applications. Since then, several studies have assessed the use of CAR-T cells toward non-malignant pathologies such as autoimmune diseases, infectious diseases and, more recently, cardiac fibrosis, and cellular senescence. In this review, we present the main findings and implications of CAR-based therapies for non-malignant conditions.

Engineering precision therapies: lessons and motivations from the clinic

In the past decade, gene- and cell-based therapies have been at the forefront of the biomedical revolution. Synthetic biology, the engineering discipline of building sophisticated ‘genetic software’ to enable precise regulation of gene activities in living cells, has been a decisive success factor of these new therapies. Here, we discuss the core technologies and treatment strategies that have already gained approval for therapeutic applications in humans. We also review promising preclinical work that could either enhance the efficacy of existing treatment strategies or pave the way for new precision medicines to treat currently intractable human conditions.

Dual CD4-based CAR T cells with distinct costimulatory domains mitigate HIV pathogenesis in vivo

An effective strategy to cure HIV will likely require a potent and sustained antiviral T cell response. Here we explored the utility of chimeric antigen receptor (CAR) T cells, expressing the CD4 ectodomain to confer specificity for the HIV envelope, to mitigate HIV-induced pathogenesis in bone marrow, liver, thymus (BLT) humanized mice. CAR T cells expressing the 4-1BB/CD3-ζ endodomain were insufficient to prevent viral rebound and CD4⁺ T cell loss after the discontinuation of antiretroviral therapy. Through iterative improvements to the CAR T cell product, we developed Dual-CAR T cells that simultaneously expressed both 4-1BB/CD3-ζ and CD28/CD3-ζ endodomains. Dual-CAR T cells exhibited expansion kinetics that exceeded 4-1BB-, CD28- and third-generation costimulated CAR T cells, elicited effector functions equivalent to CD28-costimulated CAR T cells and prevented HIV-induced CD4⁺ T cell loss despite persistent viremia. Moreover, when Dual-CAR T cells were protected from HIV infection through expression of the C34-CXCR4 fusion inhibitor, these cells significantly reduced acute-phase viremia, as well as accelerated HIV suppression in the presence of antiretroviral therapy and reduced tissue viral burden. Collectively, these studies demonstrate the enhanced therapeutic potency of a novel Dual-CAR T cell product with the potential to effectively treat HIV infection.

A Universal CAR-NK Cell Targeting Various Epitopes of HIV-1 gp160

Engineering T cells and natural killer (NK) cells with anti-HIV chimeric antigen receptors (CAR) has emerged as a promising strategy to eradicate HIV-infected cells. However, current anti-HIV CARs are limited by targeting a single epitope of the HIV envelope glycoprotein gp160, which cannot counter the enormous diversity and mutability of viruses. Here, we report the development of a universal CAR-NK cell, which recognizes 2,4-dinitrophenyl (DNP) and can subsequently be redirected to target various epitopes of gp160 using DNP-conjugated antibodies as adaptor molecules. We show that this CAR-NK cell can recognize and kill mimic HIV-infected cell lines expressing subtypes B and C gp160. We additionally find that anti-gp160 antibodies targeting membrane-distal epitopes (including V1/V2, V3, and CD4bs) are more likely to activate universal CAR-NK cells against gp160⁺ target cells, compared with those targeting membrane-proximal epitopes located in the gp41 MPER. Finally, we confirm that HIV-infected primary human CD4⁺ T cells can be effectively killed using the same approach. Given that numerous anti-gp160 antibodies with different antigen specificities are readily available, this modular universal CAR-NK cell platform can potentially overcome HIV diversity, thus providing a promising strategy to eradicate HIV-infected cells.

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.

Engineering CAR T Cells to Target the HIV Reservoir

The HIV reservoir remains to be a difficult barrier to overcome in order to achieve a therapeutic cure for HIV. Several strategies have been developed to purge the reservoir, including the “kick and kill” approach, which is based on the notion that reactivating the latent reservoir will allow subsequent elimination by the host anti-HIV immune cells. However, clinical trials testing certain classes of latency reactivating agents (LRAs) have so far revealed the minimal impact on reducing the viral reservoir. A robust immune response to reactivated HIV expressing cells is critical for this strategy to work. A current focus to enhance anti-HIV immunity is through the use of chimeric antigen receptors (CARs). Currently, HIV-specific CARs are being applied to peripheral T cells, NK cells, and stem cells to boost recognition and killing of HIV infected cells. In this review, we summarize current developments in engineering HIV directed CAR-expressing cells to facilitate HIV elimination. We also summarize current LRAs that enhance the “kick” strategy and how new generation and combinations of LRAs with HIV specific CAR T cell therapies could provide an optimal strategy to target the viral reservoir and achieve HIV clearance from the body.

CAR T cells: Living HIV drugs

Human immunodeficiency virus type 1 (HIV-1), the virus that causes AIDS (acquired immunodeficiency syndrome), is a major global public health issue. Although the advent of combined antiretroviral therapy (ART) has made significant progress in inhibiting HIV replication in patients, HIV-infected cells remain the principal cellular reservoir of HIV, this allows HIV to rebound immediately upon stopping ART, which is considered the major obstacle to curing HIV infection. Chimeric antigen receptor (CAR) cell therapy has provided new opportunities for HIV treatment. Engineering T cells or hematopoietic stem cells (HSCs) to generate CAR T cells is a rapidly growing approach to develop an efficient immune cell to fight HIV. Herein, we review preclinical and clinical data available for the development of CAR T cells. Further, the advantages and disadvantages of clinical application of anti-HIV CAR T cells will be discussed.

HIV-Resistant and HIV-Specific CAR-Modified CD4+ T Cells Mitigate HIV Disease Progression and Confer CD4+ T Cell Help In Vivo

HIV infection preferentially depletes HIV-specific CD4+ T cells, thereby impairing antiviral immunity. In this study, we explored the therapeutic utility of adoptively transferred CD4+ T cells expressing an HIV-specific chimeric antigen receptor (CAR4) to restore CD4+ T cell function to the global HIV-specific immune response. We demonstrated that CAR4 T cells directly suppressed in vitro HIV replication and eliminated virus-infected cells. Notably, CAR4 T cells containing intracellular domains (ICDs) derived from the CD28 receptor family (ICOS and CD28) exhibited superior effector functions compared to the tumor necrosis factor receptor (TNFR) family ICDs (CD27, OX40, and 4-1BB). However, despite demonstrating limited in vitro efficacy, only HIV-resistant CAR4 T cells expressing the 4-1BBζ ICD exhibited profound expansion, concomitant with reduced rebound viremia after antiretroviral therapy (ART) cessation and protection of CD4+ T cells (CAR-) from HIV-induced depletion in humanized mice. Moreover, CAR4 T cells enhanced the in vivo persistence and efficacy of HIV-specific CAR-modified CD8+ T cells expressing the CD28ζ ICD, which alone exhibited poor survival. Collectively, these studies demonstrate that HIV-resistant CAR4 T cells can directly control HIV replication and augment the virus-specific CD8+ T cell response, highlighting the therapeutic potential of engineered CD4+ T cells to engender a functional HIV cure.

Measuring the Success of HIV-1 Cure Strategies

HIV-1 eradication strategies aim to achieve viral remission in the absence of antiretroviral therapy (ART). The development of an HIV-1 cure remains challenging due to the latent reservoir (LR): long-lived CD4 T cells that harbor transcriptionally silent HIV-1 provirus. The LR is stable despite years of suppressive ART and is the source of rebound viremia following therapy interruption. Cure strategies such as "shock and kill" aim to eliminate or reduce the LR by reversing latency, exposing the infected cells to clearance via the immune response or the viral cytopathic effect. Alternative strategies include therapeutic vaccination, which aims to prime the immune response to facilitate control of the virus in the absence of ART. Despite promising advances, these strategies have been unable to significantly reduce the LR or increase the time to viral rebound but have provided invaluable insight in the field of HIV-1 eradication. The development and assessment of an HIV-1 cure requires robust assays that can measure the LR with sufficient sensitivity to detect changes that may occur following treatment. The viral outgrowth assay (VOA) is considered the gold standard method for LR quantification due to its ability to distinguish intact and defective provirus. However, the VOA is time consuming and resource intensive, therefore several alternative assays have been developed to bridge the gap between practicality and accuracy. Whilst a cure for HIV-1 infection remains elusive, recent advances in our understanding of the LR and methods for its eradication have offered renewed hope regarding achieving ART free viral remission.

Advances in Developing CAR T-Cell Therapy for HIV Cure

Acquired immune deficiency syndrome (AIDS), which is caused by HIV infection, is an epidemic disease that has killed millions of people in the last several decades. Although combination antiretroviral therapy (cART) has enabled tremendous progress in suppressing HIV replication, it fails to eliminate HIV latently infected cells, and infected individuals remain HIV positive for life. Lifelong antiretroviral therapy is required to maintain control of virus replication, which may result in significant problems, including long-term toxicity, high cost, and stigma. Therefore, novel therapeutic strategies are urgently needed to eliminate the viral reservoir in the host for HIV cure. In this review, we compare several potential strategies regarding HIV cure and focus on how we might utilize chimeric antigen receptor-modified T cells (CAR T) as a therapy to cure HIV infection.

Pathways towards human immunodeficiency virus elimination

Antiretroviral therapy (ART) suppresses human immunodeficiency virus (HIV) infection. Research seeking to transform viral suppression into elimination has generated novel immune, chemical and molecular antiviral agents. However, none, to date, have excised latent integrated proviral DNA or removed infected cells from infected persons. These efforts included, but are not limited to, broadly neutralizing antibodies, "shock" and "kill" latency-reversing agents, innate immune regulators, and sequential long-acting antiretroviral nanoformulated prodrugs and CRISPR-Cas9 gene editing. While, the latter, enabled the complete excision of latent HIV-1 from the host genome success was so far limited. We contend that improvements in antiretroviral delivery, potency, agent specificity, or combinatorial therapies can provide a pathway towards complete HIV elimination.

CAR T Cells Beyond Cancer: Hope for Immunomodulatory Therapy of Infectious Diseases

Infectious diseases are still a significant cause of morbidity and mortality worldwide. Despite the progress in drug development, the occurrence of microbial resistance is still a significant concern. Alternative therapeutic strategies are required for non-responding or relapsing patients. Chimeric antigen receptor (CAR) T cells has revolutionized cancer immunotherapy, providing a potential therapeutic option for patients who are unresponsive to standard treatments. Recently two CAR T cell therapies, Yescarta® (Kite Pharma/Gilead) and Kymriah® (Novartis) were approved by the FDA for the treatments of certain types of non-Hodgkin lymphoma and B-cell precursor acute lymphoblastic leukemia, respectively. The success of adoptive CAR T cell therapy for cancer has inspired researchers to develop CARs for the treatment of infectious diseases. Here, we review the main achievements in CAR T cell therapy targeting viral infections, including Human Immunodeficiency Virus, Hepatitis C Virus, Hepatitis B Virus, Human Cytomegalovirus, and opportunistic fungal infections such as invasive aspergillosis.

CAR Talk: How Cancer-Specific CAR T Cells Can Instruct How to Build CAR T Cells to Cure HIV

Re-directing T cells via chimeric antigen receptors (CARs) was first tested in HIV-infected individuals with limited success, but these pioneering studies laid the groundwork for the clinically successful CD19 CARs that were recently FDA approved. Now there is great interest in revisiting the concept of using CAR-expressing T cells as part of a strategy to cure HIV. Many lessons have been learned on how to best engineer T cells to cure cancer, but not all of these lessons apply when developing CARs to treat and cure HIV. This mini review will focus on how early CAR T cell studies in HIV paved the way for cancer CAR T cell therapy and how progress in cancer CAR therapy has and will continue to be instructive for the development of HIV CAR T cell therapy. Additionally, the unique challenges that must be overcome to develop a successful HIV CAR T cell therapy will be highlighted.

Cell and Gene Therapy for HIV Cure

As the HIV pandemic rapidly spread worldwide in the 1980s and 1990s, a new approach to treat cancer, genetic diseases, and infectious diseases was also emerging. Cell and gene therapy strategies are connected with human pathologies at a fundamental level, by delivering DNA and RNA molecules that could correct and/or ameliorate the underlying genetic factors of any illness. The history of HIV gene therapy is especially intriguing, in that the virus that was targeted was soon co-opted to become part of the targeting strategy. Today, HIV-based lentiviral vectors, along with many other gene delivery strategies, have been used to evaluate HIV cure approaches in cell culture, small and large animal models, and in patients. Here, we trace HIV cell and gene therapy from the earliest clinical trials, using genetically unmodified cell products from the patient or from matched donors, through current state-of-the-art strategies. These include engineering HIV-specific immunity in T-cells, gene editing approaches to render all blood cells in the body HIV-resistant, and most importantly, combination therapies that draw from both of these respective "offensive" and "defensive" approaches. It is widely agreed upon that combinatorial approaches are the most promising route to functional cure/remission of HIV infection. This chapter outlines cell and gene therapy strategies that are poised to play an essential role in eradicating HIV-infected cells in vivo.

Chimeric antigen receptor T-cell approaches to HIV cure

PURPOSE OF REVIEW

Combination antiretroviral therapy (ART) has enabled tremendous progress in suppressing HIV replication in infected patients. However, ART alone cannot eradicate HIV and its latent, persisting reservoirs. Novel approaches are needed to eradicate the virus or achieve functional cure in the absence of ART.

RECENT FINDINGS

Adoptive T-cell therapies were initially tested in HIV-infected individuals with limited efficiency. Benefiting from new and improved methodologies, an increasing array of CAR T-cell therapies has been successfully developed in the cancer immunotherapy field, demonstrating promising new avenues that could be applied to HIV. Numerous studies have characterized various HIV-specific CAR constructs, types of cytolytic effector cells, and CAR-expressing cells' trafficking to the reservoir compartments, warranting further in-vivo efforts. Notably, the ability of CAR cells to persist and function in low-antigen environments in vivo, that is, in ART-suppressed patients, remains unclear.

SUMMARY

Despite promising results in preclinical studies, only a handful of clinical trials have been initiated worldwide. Several obstacles remain prior to successful application of HIV-specific CAR T-cell therapies in patients. In this review, we survey the current state of the field, and address paths towards realizing the goal of an efficacious HIV CAR T-cell product.

Quarter Century of Anti-HIV CAR T Cells

PURPOSE OF REVIEW

A therapy that might cure HIV is a very important goal for the 30-40 million people living with HIV. Chimeric antigen receptor T cells have recently had remarkable success against certain leukemias, and there are reasons to believe they could be successful for HIV. This manuscript summarizes the published research on HIV CAR T cells and reviews the current anti-HIV chimeric antigen receptor strategies.

RECENT FINDINGS

Research on anti-HIV chimeric antigen receptor T cells has been going on for at least the last 25 years. First- and second-generation anti-HIV chimeric antigen receptors have been developed. First-generation anti-HIV chimeric antigen receptors were studied in clinical trials more than 15 years ago, but did not have meaningful clinical efficacy. There are some reasons to be optimistic about second-generation anti-HIV chimeric antigen receptor T cells, but they have not yet been tested in vivo.

Development of CAR-T cells for long-term eradication and surveillance of HIV-1 reservoir

Human immunodeficiency virus type 1 (HIV-1) reservoir is a pool of latently infected cells harboring replication-competent proviral DNA that limits antiretroviral therapy. Suppression of HIV-1 by combination antiretroviral therapy (cART) delays progression of the disease but does not eliminate the viral reservoir, necessitating lifetime daily administration of antiretroviral drugs. To achieve durable suppression of viremia without daily therapy, various strategies have been developed, including long-acting antiretroviral drugs (LA-ARVs), broadly neutralizing antibodies (bNAbs), and chimeric antigen receptor T (CAR-T) cells. Here, we summarize and discuss recent breakthroughs in CAR-T cell therapies toward the eradication of HIV-1 reservoir. Although substantial challenges exist, CAR-T cell technology may serve as a promising strategy toward HIV-1 functional cure.

Gene Therapy Approaches to Functional Cure and Protection of Hematopoietic Potential in HIV Infection

Although current antiretroviral drug therapy can suppress the replication of human immunodeficiency virus (HIV), a lifelong prescription is necessary to avoid viral rebound. The problem of persistent and ineradicable viral reservoirs in HIV-infected people continues to be a global threat. In addition, some HIV-infected patients do not experience sufficient T-cell immune restoration despite being aviremic during treatment. This is likely due to altered hematopoietic potential. To achieve the global eradication of HIV disease, a cure is needed. To this end, tremendous efforts have been made in the field of anti-HIV gene therapy. This review will discuss the concepts of HIV cure and relative viral attenuation and provide an overview of various gene therapy approaches aimed at a complete or functional HIV cure and protection of hematopoietic functions.