CXCR5+CD8+ T cells are a distinct functional subset with an antitumor activity

Impact of isotype on the mechanism of action of agonist anti-OX40 antibodies in cancer: implications for therapeutic combinations

BACKGROUND

OX40 has been widely studied as a target for immunotherapy with agonist antibodies taken forward into clinical trials for cancer where they are yet to show substantial efficacy. Here, we investigated potential mechanisms of action of anti-mouse (m) OX40 and anti-human (h) OX40 antibodies, including a clinically relevant monoclonal antibody (mAb) (GSK3174998) and evaluated how isotype can alter those mechanisms with the aim to develop improved antibodies for use in rational combination treatments for cancer.

METHODS

Anti-mOX40 and anti-hOX40 mAbs were evaluated in a number of in vivo models, including an OT-I adoptive transfer immunization model in hOX40 knock-in (KI) mice and syngeneic tumor models. The impact of FcγR engagement was evaluated in hOX40 KI mice deficient for Fc gamma receptors (FcγR). Additionally, combination studies using anti-mouse programmed cell death protein-1 (mPD-1) were assessed. In vitro experiments using peripheral blood mononuclear cells (PBMCs) examining possible anti-hOX40 mAb mechanisms of action were also performed.

RESULTS

Isotype variants of the clinically relevant mAb GSK3174998 showed immunomodulatory effects that differed in mechanism; mIgG1 mediated direct T-cell agonism while mIgG2a acted indirectly, likely through depletion of regulatory T cells (Tregs) via activating FcγRs. In both the OT-I and EG.7-OVA models, hIgG1 was the most effective human isotype, capable of acting both directly and through Treg depletion. The anti-hOX40 hIgG1 synergized with anti-mPD-1 to improve therapeutic outcomes in the EG.7-OVA model. Finally, in vitro assays with human peripheral blood mononuclear cells (hPBMCs), anti-hOX40 hIgG1 also showed the potential for T-cell stimulation and Treg depletion.

CONCLUSIONS

These findings underline the importance of understanding the role of isotype in the mechanism of action of therapeutic mAbs. As an hIgG1, the anti-hOX40 mAb can elicit multiple mechanisms of action that could aid or hinder therapeutic outcomes, dependent on the microenvironment. This should be considered when designing potential combinatorial partners and their FcγR requirements to achieve maximal benefit and improvement of patient outcomes.

Hepatitis B cure: Current situation and prospects

Achievement of a 'clinical cure' in chronic hepatitis B (CHB) implies sustained virological suppression and immunological control over the infection, which is the ideal treatment goal according to domestic and international CHB management guidelines. Clinical practice has shown encouraging results for specific patient cohorts using tailored treatment regimens. These regimens incorporate either nucleos(t)ide analogs, immunomodulatory agents such as pegylated interferon α, or a strategic combination of both, sequentially or concurrently administered. Despite these advancements in the clinical handling of hepatitis B, achieving a clinical cure remains elusive for a considerable subset of patients due to the number of challenges that preclude the realization of optimal treatment outcomes. These include, but are not limited to, the emergence of antiviral resistance, incomplete immune recovery, and the persistence of covalently closed circular DNA. Moreover, the variance in response to interferon therapy and the lack of definitive biomarkers for treatment cessation also contribute to the complexity of achieving a clinical cure. This article briefly overviews the current research progress and existing issues in pursuing a clinical cure for hepatitis B.

Unlocking PD-1 antibody resistance: The MUC1 DNA vaccine augments CD8+ T cell infiltration and attenuates tumour suppression

In light of increasing resistance to PD1 antibody therapy among certain patient populations, there is a critical need for in-depth research. Our study assesses the synergistic effects of a MUC1 DNA vaccine and PD1 antibody for surmounting PD1 resistance, employing a murine CT26/MUC1 colon carcinoma model for this purpose. When given as a standalone treatment, PD1 antibodies showed no impact on tumour growth. Additionally, there was no change observed in the intra-tumoural T-cell ratios or in the functionality of T-cells. In contrast, the sole administration of a MUC1 DNA vaccine markedly boosted the cytotoxicity of CD8+ T cells by elevating IFN-γ and granzyme B production. Our compelling evidence highlights that combination therapy more effectively inhibited tumour growth and prolonged survival compared to either monotherapy, thus mitigating the limitations intrinsic to single-agent therapies. This enhanced efficacy was driven by a significant alteration in the tumour microenvironment, skewing it towards pro-immunogenic conditions. This assertion is backed by a raised CD8+/CD4+ T-cell ratio and a decrease in immunosuppressive MDSC and Treg cell populations. On the mechanistic front, the synergistic therapy amplified expression levels of CXCL13 in tumours, subsequently facilitating T-cell ingress into the tumour setting. In summary, our findings advocate for integrated therapy as a potent mechanism for surmounting PD1 antibody resistance, capitalizing on improved T-cell functionality and infiltration. This investigation affords critical perspectives on enhancing anti-tumour immunity through the application of innovative therapeutic strategies.

Single-cell adhesive profiling in an optofluidic device elucidates CD8+ T lymphocyte phenotypes in inflamed vasculature-like microenvironments

Tissue infiltration by circulating leukocytes occurs via adhesive interactions with the local vasculature, but how the adhesive quality of circulating cells guides the homing of specific phenotypes to different vascular microenvironments remains undefined. We developed an optofluidic system enabling fluorescent labeling of photoactivatable cells based on their adhesive rolling velocity in an inflamed vasculature-mimicking microfluidic device under physiological fluid flow. In so doing, single-cell level multidimensional profiling of cellular characteristics could be characterized and related to the associated adhesive phenotype. When applied to CD8+ T cells, ligand/receptor expression profiles and subtypes associated with adhesion were revealed, providing insight into inflamed tissue infiltration capabilities of specific CD8+ T lymphocyte subsets and how local vascular microenvironmental features may regulate the quality of cellular infiltration. This methodology facilitates rapid screening of cell populations for enhanced homing capabilities under defined biochemical and biophysical microenvironments, relevant to leukocyte homing modulation in multiple pathologies.

T cell exhaustion dynamics in systemic autoimmune disease

Unlike in infection and cancer, T cell exhaustion in autoimmune disease has not been clearly defined. Here we set out to understand inhibitory protein (PD-1, Tim3, CTLA4, Lag3) expression in CXCR5- and CXCR5+ CD8 and CD4 T cells in systemic lupus erythematosus. CXCR5+ CD8 and CD4 T cells express PD-1 and engage B cells in germinal center reactions, leading to autoantibody formation in autoimmunity. We hypothesized that CXCR5+ CD8 T cells develop an exhausted phenotype as SLE autoimmunity expands from initial to chronic, self-perpetuating disease due to chronic self-antigen exposure. Our results indicate that there is no exhaustion frequency differences between sexes, although disease kinetics vary by sex. CXCR5+ CD8 T cells express primarily IFNγ, known to promote autoimmune disease development, whereas CXCR5-CD8 T cells express TNFα and IFNγ as disease progresses from 2-6 months. Tim3 is the highest expressed inhibitory marker for all CD4 and CD8 T cell populations demonstrating potential for terminally exhausted populations. CTLA4 expression on CD4 T cells suggests potential tolerance induction in these cells. We identified exhaustion phenotypes within autoimmune disease that progress with increasing lupus erythematosus severity and possibly provide a feedback mechanism for immunological tolerance.

Highlights

CXCR5- and CXCR5+ CD8 T cells expand with rate of disease in SLE mouse model.CXCR5+ CD8 T cells are low contributors to TNFα disease progression unlike CXCR5-CD8 T cells but may increase disease mechanisms through high IFNγ production.Inhibitory markers upregulate in frequency with the highest amounts seen in Tim3+ populations. Tim3+Lag3+ expression may be an indicator of terminal differentiation for all populations.Inhibitory marker expression frequency was unrelated to sex.

T-cell subset changes during the first year of pre-seasonal allergoid allergen-specific immunotherapy

Allergen-specific immunotherapy (AIT) is the only treatment for type I allergy, which achieves long-lasting effects. Repeated subcutaneous applications of allergen extracts cause a protective antibody response and an immune deviation of T cells. In AIT with allergoids, chemically modified allergen extracts are injected. During a so-called special pre-seasonal application scheme, after the initial phase of applying increased doses of allergoids is followed by natural allergen exposure as a maintenance phase. The effectiveness of allergoid vaccines has been described regarding the improvement of clinical symptoms and the development of protective humoral responses. In this longitudinal observational study, we sought to investigate changes at the T cell level in pre-seasonal AIT with allergoid. Different subsets within CD4+ and CD8+ T cells were monitored by flow cytometry in PBMC of patients known to possess protective antibody responses. Compared to before treatment, a small early boost among allergenic Th cells was observed after 4 months of AIT. In line, a slight Th2 bias was observed after 4 months within circulating T follicular T cells, Tfh and Tfc, representing pre-existing memory Th2 cells. Furthermore, it was demonstrated that responsiveness of CD8+ T cells to allergen stimulation decreased during the course of treatment. Apart from that, we found an influence of the meteorological season on the activation profile of Tfh and Tfc over the course of the treatment. Together, this is the first study investigating changes of different T cell subsets over the course of an allergoid AIT against airborne allergens. Our findings match previous reports on conventional AIT, especially the initial increase of Th2 responses. However, the observed changes were less pronounced which may be either due to the modification of allergens or to the reduced maintenance dose provided by natural allergen exposure compared to a perennial protocol.

CD8 T-cell subsets: heterogeneity, functions, and therapeutic potential

CD8 T cells play crucial roles in immune surveillance and defense against infections and cancer. After encountering antigenic stimulation, naïve CD8 T cells differentiate and acquire effector functions, enabling them to eliminate infected or malignant cells. Traditionally, cytotoxic T cells, characterized by their ability to produce effector cytokines and release cytotoxic granules to directly kill target cells, have been recognized as the constituents of the predominant effector T-cell subset. However, emerging evidence suggests distinct subsets of effector CD8 T cells that each exhibit unique effector functions and therapeutic potential. This review highlights recent advancements in our understanding of CD8 T-cell subsets and the contributions of these cells to various disease pathologies. Understanding the diverse roles and functions of effector CD8 T-cell subsets is crucial to discern the complex dynamics of immune responses in different disease settings. Furthermore, the development of immunotherapeutic approaches that specifically target and regulate the function of distinct CD8 T-cell subsets holds great promise for precision medicine.

Clinical cure of hepatitis B: Delight and anticipation

Chronic hepatitis B (CHB) patients achieving clinical cure represent individuals who have attained persistent virological suppression and immunological control. This is the ideal treatment goal in both domestic and international CHB management guidelines. Clinical practice has demonstrated promising outcomes for certain patient populations treated with optimized regimens involving nucleos(t)ide analogs (NAs) or immunomodulators (such as pegylated interferon α) administered sequentially or in combination. However, despite the gratifying progress in the clinical management of hepatitis B, a significant number of patients still cannot achieve the goal of clinical cure. Many challenges remain to be overcome to achieve better treatment outcomes. This article provides a brief overview of the current research progress and existing issues in the pursuit of clinical cure of hepatitis B.

Follicular lymphoma microenvironment: insights provided by single-cell analysis

Follicular lymphoma (FL) is the most frequent indolent lymphoma and is characterized by the abundant infiltration of tumor microenvironment (TME) cells. The activity of TME cells reportedly plays an important role in the biology of FL. TME cells that reside within neoplastic follicles, such as T-follicular helper cells and follicular dendritic cells, have been shown to aid in FL development and progression through interactions with malignant B cells, whereas regulatory T cells have unexpectedly shown an apparently favorable prognostic impact in FL. Unfortunately, the understanding of the FL TME, particularly regarding minor cell subsets, has been hampered by unknown cell heterogeneity. As with other solid and hematologic cancers, novel single-cell analysis technologies have recently been applied to FL research and have uncovered previously unrecognized heterogeneities, not only in malignant B cells but also in TME cells. These reports have greatly increased the resolution of our understanding of the FL TME and, at the same time, raised questions about newly identified TME cells. This review provides an overview of the unique aspects of FL TME cells with a clinical viewpoint and highlights recent discoveries from single-cell analysis, while also suggesting potential future directions.

Cellular and molecular waypoints along the path of T cell exhaustion

Thirty years of foundational research investigating molecular and cellular mechanisms promoting T cell exhaustion are now enabling rational design of T cell-based therapies for the treatment of chronic infections and cancer. Once described as a static cell fate, it is now well appreciated that the developmental path toward exhaustion is composed of a heterogeneous pool of cells with varying degrees of effector potential that ultimately converge on a terminally differentiated state. Recent description of the developmental stages along the differentiation trajectory of T cell exhaustion has provided insight into past immunotherapeutic success and future opportunities. Here, we discuss the hallmarks of distinct developmental stages occurring along the path to T cell dysfunction and the impact of these discrete CD8+ T cell fates on cancer immunotherapy.

Dissecting the Protective Effect of CD8+ T Cells in Response to SARS-CoV-2 mRNA Vaccination and the Potential Link with Lymph Node CD8+ T Cells

SARS-CoV-2 vaccines have played a crucial role in effectively reducing COVID-19 disease severity, with a new generation of vaccines that use messenger RNA (mRNA) technology being administered globally. Neutralizing antibodies have featured as the heroes of vaccine-induced immunity. However, vaccine-elicited CD8⁺ T cells may have a significant impact on the early protective effects of the mRNA vaccine, which are evident 12 days after initial vaccination. Vaccine-induced CD8⁺ T cells have been shown to respond to multiple epitopes of SARS-CoV-2 and exhibit polyfunctionality in the periphery at the early stage, even when neutralizing antibodies are scarce. Furthermore, SARS-CoV-2 mRNA vaccines induce diverse subsets of memory CD8⁺ T cells that persist for more than six months following vaccination. However, the protective role of CD8⁺ T cells in response to the SARS-CoV-2 mRNA vaccines remains a topic of debate. In addition, our understanding of CD8⁺ T cells in response to vaccination in the lymph nodes, where they first encounter antigen, is still limited. This review delves into the current knowledge regarding the protective role of polyfunctional CD8⁺ T cells in controlling the virus, the response to SARS-CoV-2 mRNA vaccines, and the contribution to supporting B cell activity and promoting immune protection in the lymph nodes.

PD-1Hi CAR-T cells provide superior protection against solid tumors

Chimeric antigen receptor (CAR)-T cell therapy has emerged as a promising treatment option for several hematologic cancers. However, efforts to achieve the same level of therapeutic success in solid tumors have largely failed mainly due to CAR-T cell exhaustion and poor persistence at the tumor site. Although immunosuppression mediated by augmented programmed cell death protein-1 (PD-1) expression has been proposed to cause CAR-T cell hypofunction and limited clinical efficacy, little is known about the underlying mechanisms and immunological consequences of PD-1 expression on CAR-T cells. With flow cytometry analyses and in vitro and in vivo anti-cancer T cell function assays, we found that both manufactured murine and human CAR-T cell products displayed phenotypic signs of T cell exhaustion and heterogeneous expression levels of PD-1. Unexpectedly, PD-1high CAR-T cells outperformed PD-1low CAR-T cells in multiple T cell functions both in vitro and in vivo. Despite the achievement of superior persistence at the tumor site in vivo, adoptive transfer of PD-1high CAR-T cells alone failed to control tumor growth. Instead, a PD-1 blockade combination therapy significantly delayed tumor progression in mice infused with PD-1high CAR-T cells. Therefore, our data demonstrate that robust T cell activation during the ex vivo CAR-T cell manufacturing process generates a PD-1high CAR-T cell subset with improved persistence and enhanced anti-cancer functions. However, these cells may be vulnerable to the immunosuppressive microenvironment and require combination with PD-1 inhibition to maximize therapeutic functions in solid tumors.

TGFβ control of immune responses in cancer: a holistic immuno-oncology perspective

The immune system responds to cancer in two main ways. First, there are prewired responses involving myeloid cells, innate lymphocytes and innate-like adaptive lymphocytes that either reside in premalignant tissues or migrate directly to tumours, and second, there are antigen priming-dependent responses, in which adaptive lymphocytes are primed in secondary lymphoid organs before homing to tumours. Transforming growth factor-β (TGFβ) - one of the most potent and pleiotropic regulatory cytokines - controls almost every stage of the tumour-elicited immune response, from leukocyte development in primary lymphoid organs to their priming in secondary lymphoid organs and their effector functions in the tumour itself. The complexity of TGFβ-regulated immune cell circuitries, as well as the contextual roles of TGFβ signalling in cancer cells and tumour stromal cells, necessitates the use of rigorous experimental systems that closely recapitulate human cancer, such as autochthonous tumour models, to uncover the underlying immunobiology. The diverse functions of TGFβ in healthy tissues further complicate the search for effective and safe cancer therapeutics targeting the TGFβ pathway. Here we discuss the contextual complexity of TGFβ signalling in tumour-elicited immune responses and explain how understanding this may guide the development of mechanism-based cancer immunotherapy.

Immunological Pathways in Sarcoidosis and Autoimmune Rheumatic Disorders-Similarities and Differences in an Italian Prospective Real-Life Preliminary Study

BACKGROUND

The pathogenesis of sarcoidosis involves T cells and B lymphocytes that produce autoantibodies. We compared the expression of different T and B cell subsets in sarcoidosis and three B-mediated rheumatic diseases that can affect the lungs in an attempt to identify similarities and differences that distinguish these diseases.

METHODS

The study included patients referred to Siena University Hospital's respiratory disease and rheumatology units. Patients were enrolled prospectively and consecutively. Healthy volunteers were also included. Multicolor flow cytometry was performed on phenotype T and B cell subsets. Multivariate analysis was carried out to reduce the dimensionality of the data.

RESULTS

Fifteen patients had a diagnosis of sarcoidosis, fourteen idiopathic inflammatory myopathies (IIM), five granulomatosis with polyangiitis (GPA), ten microscopic polyangiitis (MPA), and seven were controls. Thirty-five T and B cell subsets were phenotyped, 15 of which were significantly different in sarcoidosis, B-mediated rheumatic disorders, and controls. Principal components analysis distinguished the four groups of patients with a total explained variance of 54.7%. A decision tree was constructed to determine which clustering variables would be most useful for distinguishing sarcoidosis, IIM, MPA, and GPA. The model showed regulatory T helper cells (Th-reg) > 5.70% in 91% of sarcoidosis patients as well as Th-reg ≤ 5.70 and Th17 > 43.27 in 100% of MPA. It also showed Th-reg ≤ 5.70, Th17 ≤ 43.27 and Tfh-reg ≥ 7.81 in 100% of GPA patients, and Th-reg ≤ 5.70, Th17 ≤ 43.27 and Tfh-reg ≤ 7.81 in 100% of IIM patients.

CONCLUSION

The immune cell profile sheds light on similarities and differences between sarcoidosis and B-mediated rheumatic diseases. Sarcoidosis and autoimmune diseases show similar patterns of cellular immune dysregulation, suggesting a common pathogenic pathway that may provide an opportunity for further understanding autoimmunity and exploring biological therapies to treat sarcoidosis.

Cytolytic CD8+ T cells infiltrate germinal centers to limit ongoing HIV replication in spontaneous controller lymph nodes

Follicular CD8⁺ T cells (fCD8) mediate surveillance in lymph node (LN) germinal centers against lymphotropic infections and cancers, but the precise mechanisms by which these cells mediate immune control remain incompletely resolved. To address this, we investigated functionality, clonotypic compartmentalization, spatial localization, phenotypic characteristics, and transcriptional profiles of LN-resident virus-specific CD8⁺ T cells in persons who control HIV without medications. Antigen-induced proliferative and cytolytic potential consistently distinguished spontaneous controllers from noncontrollers. T cell receptor analysis revealed complete clonotypic overlap between peripheral and LN-resident HIV-specific CD8⁺ T cells. Transcriptional analysis of LN CD8⁺ T cells revealed gene signatures of inflammatory chemotaxis and antigen-induced effector function. In HIV controllers, the cytotoxic effectors perforin and granzyme B were elevated among virus-specific CXCR5⁺ fCD8s proximate to foci of HIV RNA within germinal centers. These results provide evidence consistent with cytolytic control of lymphotropic infection supported by inflammatory recruitment, antigen-specific proliferation, and cytotoxicity of fCD8s.

Innate and Adaptive Immunity during SARS-CoV-2 Infection: Biomolecular Cellular Markers and Mechanisms

The coronavirus 2019 (COVID-19) pandemic was caused by a positive sense single-stranded RNA (ssRNA) severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, other human coronaviruses (hCoVs) exist. Historical pandemics include smallpox and influenza, with efficacious therapeutics utilized to reduce overall disease burden through effectively targeting a competent host immune system response. The immune system is composed of primary/secondary lymphoid structures with initially eight types of immune cell types, and many other subtypes, traversing cell membranes utilizing cell signaling cascades that contribute towards clearance of pathogenic proteins. Other proteins discussed include cluster of differentiation (CD) markers, major histocompatibility complexes (MHC), pleiotropic interleukins (IL), and chemokines (CXC). The historical concepts of host immunity are the innate and adaptive immune systems. The adaptive immune system is represented by T cells, B cells, and antibodies. The innate immune system is represented by macrophages, neutrophils, dendritic cells, and the complement system. Other viruses can affect and regulate cell cycle progression for example, in cancers that include human papillomavirus (HPV: cervical carcinoma), Epstein-Barr virus (EBV: lymphoma), Hepatitis B and C (HB/HC: hepatocellular carcinoma) and human T cell Leukemia Virus-1 (T cell leukemia). Bacterial infections also increase the risk of developing cancer (e.g., Helicobacter pylori). Viral and bacterial factors can cause both morbidity and mortality alongside being transmitted within clinical and community settings through affecting a host immune response. Therefore, it is appropriate to contextualize advances in single cell sequencing in conjunction with other laboratory techniques allowing insights into immune cell characterization. These developments offer improved clarity and understanding that overlap with autoimmune conditions that could be affected by innate B cells (B1+ or marginal zone cells) or adaptive T cell responses to SARS-CoV-2 infection and other pathologies. Thus, this review starts with an introduction into host respiratory infection before examining invaluable cellular messenger proteins and then individual immune cell markers.

Follicular CD8+ T Cells Are Elevated in HIV Infection and Induce PD-L1 on B Cells

Follicular CD8+CXCR5+ T cells are a specialized CD8+ T cell subset with unique follicular-homing capabilities that have been reported to display effector functions in viral immunity, tumor immunity, and autoimmunity. CD8+CXCR5+ T cells exhibit B cell helper functions and express CD40L, ICOS, programmed cell death protein 1 (PD-1), and BCL-6, the transcriptional regulator of CD4+CXCR5+ T follicular helper cells and of germinal center B cells. HIV is known to be sequestered in lymphoid follicles, and CD8+CXCR5+ T cell frequency is a marker for disease severity, given that HIV-infected patients with lower numbers of circulating CD8+CXCR5+ T cells display lower CD4+ T cell counts. Likewise, several groups have reported a direct correlation between the quantity of CD8+CXCR5+ T cells and suppression of HIV viral load. In this study, we observed elevated absolute numbers of CD8+CXCR5+ and CD8+CXCR5+BCL-6+PD-1+ T cells in the blood of HIV-infected participants of the Multicenter AIDS Cohort Study. We further demonstrated in vitro that activated human CD8+CXCR5+ T cells isolated from peripheral blood and tonsil from healthy donors show increased CD40L expression and induce the production of PD ligand 1 (PD-L1)+IgG+ B cells. Moreover, absolute numbers of CD8+CXCR5+ T cells significantly and positively correlated with numbers of PD-L1+ B cells found in blood of HIV-infected individuals. Altogether, these results show that activated CD8+CXCR5+ T cells have the ability to activate B cells and increase the percentage of PD-L1+ and PD-L1+IgG+ B cells, which provides insights into the early events of B cell activation and differentiation and may play a role in disease progression and lymphomagenesis in HIV-infected individuals.

Biology and clinical relevance of follicular cytotoxic T cells

Follicular cytotoxic T (Tfc) cells are a newly identified subset of CD8⁺ T cells enriched in B cell follicles and their surroundings, which integrate multiple functions such as killing, memory, supporting and regulation. Tfc cells share similarities with follicular helper T (Tfh) cells, conventional cytotoxic CD8⁺ T (Tc cells)cells and follicular regulatory T (Tfr) cells, while they express distinct transcription factors, phenotype, and perform different functions. With the participation of cytokines and cell-cell interactions, Tfc cells modulate Tfh cells and B cells and play an essential role in regulating the humoral immunity. Furthermore, Tfc cells have been found to change in their frequencies and functions during the occurrence and progression of chronic infections, immune-mediated diseases and cancers. Strategies targeting Tfc cells are under investigations, bringing novel insights into control of these diseases. We summarize the characteristics of Tfc cells, and introduce the roles and potential targeting modalities of Tfc cells in different diseases.

Extensive Phenotypic Characterization of T Cells Infiltrating Liver Metastasis from Colorectal Cancer: A Potential Role in Precision Medicine

Colorectal cancer (CRC) is one of the most common cancers worldwide, with liver metastasis being its main cause of death. This study harvested fresh biological material from non-tumor and tumor tissue from 47 patients with CRC liver metastasis after surgery, followed by mechanical cellular extraction and stain-lyse-wash direct immunofluorescence technique. Here, 60 different T-cell populations were characterized by flow cytometry. Tumor samples were also subdivided according to their growth pattern into desmoplastic and non-desmoplastic. When we compared tumor versus non-tumor samples, we observed a significantly lower percentage of T-lymphocyte infiltration in the tumor in which the CD4⁺ T-cell density increased compared to the CD8⁺ T cells. T regulatory cells also increased within the tumor, even with an activated phenotype (HLA-DR⁺). A higher percentage of IL-17-producing cells was present in tumor samples and correlated with the metastasis size. In contrast, we also observed a significant increase in CD8⁺ follicular-like T cells (CD185⁺), suggesting a cytotoxic response to cancer cells. Additionally, most infiltrated T cells exhibit an intermediate activation phenotype (CD25⁺). In conclusion, our results revealed potential new targets and prognostic biomarkers that could take part in an algorithm for personalized medicine approaches improving CRC patients' outcomes.

CXCR5+CD8 T cells: Potential immunotherapy targets or drivers of immune-mediated adverse events?

CXCR5⁺CD8 T cells have attracted significant interest within multiple areas of immunology, cancer, and infection. This is in part due to their apparent dual functionality. These cells perform as cytotoxic cells in a variety of infection states including LCMV, HBV, HIV and SIV. However, CXCR5⁺CD8 T cells also associate with B cells in peripheral organs and function to stimulate B cell proliferation, antibody/B cell receptor class-switch, and antibody production. CXCR5⁺CD8 T cells are similar to CXCR5⁺CD4 T follicular helpers in their genetic make-up, B cell interactions, and functionality despite possessing elevated programmed cell death 1 and cytotoxic proteins. Within cancer CXCR5⁺CD8 T cells have risen as potential prognostic markers for overall survival and are functionally cytotoxic within tumor microenvironments. In inflammatory disease and autoimmunity, CXCR5⁺CD8 T cells are implicated in disease progression. During viral infection and cancer, CXCR5 expression on CD8 T cells generally is indicative of progenitor memory stem-like exhausted cells, which are more responsive to immune checkpoint blockade therapy. The use of immune checkpoint inhibitors to overcome immune exhaustion in cancer, and subsequent consequence of immune adverse events, highlights the dual nature of the cellular immune response. This review will detail the functionality of CXCR5⁺CD8 T cells in cancer and autoimmunity with potential repercussions during immune checkpoint blockade therapy discussed.

Immune Checkpoint Inhibitors in 10 Years: Contribution of Basic Research and Clinical Application in Cancer Immunotherapy

Targeting immune evasion via immune checkpoint pathways has changed the treatment paradigm in cancer. Since CTLA-4 antibody was first approved in 2011 for treatment of metastatic melanoma, eight immune checkpoint inhibitors (ICIs) centered on PD-1 pathway blockade are approved and currently administered to treat 18 different types of cancers. The first part of the review focuses on the history of CTLA-4 and PD-1 discovery and the preclinical experiments that demonstrated the possibility of anti-CTLA-4 and anti-PD-1 as anti-cancer therapeutics. The approval process of clinical trials and clinical utility of ICIs are described, specifically focusing on non-small cell lung cancer (NSCLC), in which immunotherapies are most actively applied. Additionally, this review covers the combination therapy and novel ICIs currently under investigation in NSCLC. Although ICIs are now key pivotal cancer therapy option in clinical settings, they show inconsistent therapeutic efficacy and limited responsiveness. Thus, newly proposed action mechanism to overcome the limitations of ICIs in a near future are also discussed.

The diagnostic role of PD-1+ CXCR5+ follicular helper CD8+ T cell in renal allograft dysfunction

BACKGROUND

The roles of PD-1⁺ CXCR5⁺ follicular helper CD8⁺ T cell were reported in different disease conditions, but their roles in transplantation are unclear. In this study, the association between PD-1⁺ CXCR5⁺ follicular helper CD8⁺ T cell and renal allograft dysfunction in kidney transplant recipients (KTRs) was investigated.

METHODS

82 KTRs were enrolled in this study. 45 KTRs were included in the chronic allograft dysfunction (CAD) group, and 37 KTRs were included in the stable recipients group. Among the CAD group, 12 cases of antibody-mediated rejection (ABMR) and 4 cases of T cell-mediated rejection (TCMR) were diagnosed by biopsy. The percentage of CXCR5⁺ CD8⁺ T cells and the co-expression of signal transducers and activators of transcription 4 (STAT4), STAT5, and PD-1 in peripheral blood were determined by flow cytometry.

RESULTS

The expression of CXCR5 on CD3⁺ CD8⁺ T cells and the percentage of STAT5⁺ CXCR5⁺ cells in the CD3⁺ CD8⁺ T-cell population were significantly lower in the CAD group (p < 0.05), while the expression of PD-1⁺ CXCR5⁺ CD8⁺ T cells was significantly higher (p < 0.05). Through logistic regression analysis, we concluded that the percentage of PD-1⁺ CXCR5⁺ CD8⁺ T cells was an independent risk factor for renal dysfunction. Grouping by pathological type, PD-1⁺ CXCR5⁺ CD8⁺ T cells showed relatively good diagnostic efficacy for ABMR by ROC analysis.

CONCLUSIONS

Our results suggested that PD-1⁺ CXCR5⁺ CD8⁺ T cells were a promising biomarker for distinguishing renal allograft dysfunction and different allograft pathological types. Also, our findings may provide new ways of identifying and treating allograft rejection.

The landscape of tumor cell states and ecosystems in diffuse large B cell lymphoma

Biological heterogeneity in diffuse large B cell lymphoma (DLBCL) is partly driven by cell-of-origin subtypes and associated genomic lesions, but also by diverse cell types and cell states in the tumor microenvironment (TME). However, dissecting these cell states and their clinical relevance at scale remains challenging. Here, we implemented EcoTyper, a machine-learning framework integrating transcriptome deconvolution and single-cell RNA sequencing, to characterize clinically relevant DLBCL cell states and ecosystems. Using this approach, we identified five cell states of malignant B cells that vary in prognostic associations and differentiation status. We also identified striking variation in cell states for 12 other lineages comprising the TME and forming cell state interactions in stereotyped ecosystems. While cell-of-origin subtypes have distinct TME composition, DLBCL ecosystems capture clinical heterogeneity within existing subtypes and extend beyond cell-of-origin and genotypic classes. These results resolve the DLBCL microenvironment at systems-level resolution and identify opportunities for therapeutic targeting (https://ecotyper.stanford.edu/lymphoma).

Critical Roles of Phosphoinositide 3-Kinase δ in the Humoral Immune Response to Trypanosoma congolense Infection

PI3Kδ is critical in generating humoral and regulatory immune responses. In this study, we determined the impact of PI3Kδ in immunity to Trypanosoma congolense, an African trypanosome that can manipulate and evade Ab responses critical for protection. Upon infection with T. congolense, PI3Kδ^D910A mice lacking PI3Kδ activity paradoxically show a transient enhancement in early control of parasitemia, associated with impaired production of regulatory IL-10 by B cells in the peritoneum. C57BL/6 wild-type (WT) mice treated with the PI3Kδ inhibitor (PI3Kδi) Idelalisib showed a similar transient decrease in parasitemia associated with reduced IL-10. Strikingly, however, we find that PI3Kδ^D910A mice were ultimately unable to control this infection, resulting in uncontrolled parasitemia and death within 2 wk. Assessment of humoral responses revealed delayed B cell activation, impaired germinal center responses, and compromised Ab responses to differing degrees in PI3Kδ^D910A and PI3Kδi-treated mice. To test the role of Abs, we administered serum from WT mice to PI3Kδ^D910A mice and found that lethality was prevented by postinfection serum. Interestingly, serum from naive WT mice provided partial protection to PI3Kδ^D910A mutants, indicating an additional role for natural Abs. Together our findings suggest that although PI3Kδ drives immune regulatory responses that antagonize early control of parasite growth in the peritoneum, it is also required for generation of Abs that are critical for protection from systemic trypanosome infection. The essential role of PI3Kδ for host survival of African trypanosome infection contrasts with findings for other pathogens such as Leishmania, underlining the critical importance of PI3Kδ-dependent humoral immunity in this disease.

Lineage Reprogramming of Effector Regulatory T Cells in Cancer

Regulatory T-cells (Tregs) are important for maintaining self-tolerance and tissue homeostasis. The functional plasticity of Tregs is a key feature of this lineage, as it allows them to adapt to different microenvironments, adopt transcriptional programs reflective of their environments and tailor their suppressive capacity in a context-dependent fashion. Tregs, particularly effector Tregs (eTregs), are abundant in many types of tumors. However, the functional and transcriptional plasticity of eTregs in tumors remain largely to be explored. Although depletion or inhibition of systemic Tregs can enhance anti-tumor responses, autoimmune sequelae have diminished the enthusiasm for such approaches. A more effective approach should specifically target intratumoral Tregs or subvert local Treg-mediated suppression. This mini-review will discuss the reported mechanisms by which the stability and suppressive function of tumoral Tregs are modulated, with the focus on eTregs and a subset of eTregs, follicular regulatory T (T_FR) cells, and how to harness this knowledge for the future development of new effective cancer immunotherapies that selectively target the tumor local response while sparing the systemic side effects.

CXCR5+CD8+ T Cells Shape Antibody Responses In Vivo Following Protein Immunisation and Peripheral Viral Infection

Crosstalk between T and B cells is crucial for generating high-affinity, class-switched antibody responses. The roles of CD4⁺ T cells in this process have been well-characterised. In contrast, regulation of antibody responses by CD8⁺ T cells is significantly less defined. CD8⁺ T cells are principally recognised for eliciting cytotoxic responses in peripheral tissues and forming protective memory. However, recent findings have identified a novel population of effector CD8⁺ T cells that co-opt a differentiation program characteristic of CD4⁺ T follicular helper (Tfh) cells, upregulate the chemokine receptor CXCR5 and localise to B cell follicles. While it has been shown that CXCR5⁺CD8⁺ T cells mediate the removal of viral reservoirs in the context of follicular-trophic viral infections and maintain the response to chronic insults by virtue of progenitor/stem-like properties, it is not known if CXCR5⁺CD8⁺ T cells arise during acute peripheral challenges in the absence of follicular infection and whether they influence B cell responses in vivo in these settings. Using the ovalbumin-specific T cell receptor transgenic (OT-I) system in an adoptive transfer-immunisation/infection model, this study demonstrates that CXCR5⁺CD8⁺ T cells arise in response to protein immunisation and peripheral viral infection, displaying a follicular-homing phenotype, expression of cell surface molecules associated with Tfh cells and limited cytotoxic potential. Furthermore, studies assessing the B cell response in the presence of OT-I or Cxcr5^-/- OT-I cells revealed that CXCR5⁺CD8⁺ T cells shape the antibody response to protein immunisation and peripheral viral infection, promoting class switching to IgG2c in responding B cells. Overall, the results highlight a novel contribution of CD8⁺ T cells to antibody responses, expanding the functionality of the adaptive immune system.

CXCR5+CD8+ T cells: A Review of their Antibody Regulatory Functions and Clinical Correlations

CD8⁺ T cells have conventionally been studied in relationship to pathogen or tumor clearance. Recent reports have identified novel functions of CXCR5⁺CD8⁺ T cells that can home to lymphoid follicles, a key site of antibody production. In this review we provide an in-depth analysis of conflicting reports regarding the impact of CXCR5⁺CD8⁺ T cells on antibody production and examine the data supporting a role for antibody-enhancement (B cell "helper") and antibody-downregulation (antibody-suppressor) by CXCR5⁺CD8⁺ T cell subsets. CXCR5⁺CD8⁺ T cell molecular phenotypes are associated with CD8-mediated effector functions including distinct subsets that regulate antibody responses. Co-inhibitory molecule PD-1, among others, distinguish CXCR5⁺CD8⁺ T cell subsets. We also provide the first in-depth review of human CXCR5⁺CD8⁺ T cells in the context of clinical outcomes and discuss the potential utility of monitoring the quantity of peripheral blood or tissue infiltrating CXCR5⁺CD8⁺ T cells as a prognostic tool in multiple disease states.

Intratumoral CXCR5+CD8+T associates with favorable clinical outcomes and immunogenic contexture in gastric cancer

Studies that examined an association between CD8⁺T and prognosis in gastric cancer are inconsistent, and a distinct population of CXCR5⁺CD8⁺T associated with better overall survival has been reported among various malignancies. Here, we show that the abundance of intratumoral CXCR5⁺CD8⁺T cells is associated with better overall survival in patients with gastric cancer. Patients with TNM II + III gastric cancer with higher intratumoral CXCR5⁺CD8⁺T cell infiltration are more likely to benefit from adjuvant chemotherapy. Microsatellite-unstable and Epstein–Barr virus positive tumors are enriched with CXCR5⁺CD8⁺T cells. Gastric cancer infiltrating CXCR5⁺CD8⁺T cells represent a specific subtype of stem-like CD8⁺T with effector memory feature. Identification of the clinical significance and phenotype of gastric cancer infiltrating CXCR5⁺CD8⁺T provides a roadmap for patient stratification and trials of targeted therapies.

The prognostic value of tumor infiltrating lymphocytes in gastric cancer remains controversial. Here the authors show a consistent association between higher density of intratumoral CXCR5+CD8+ T cells and longer overall survival in four different cohorts of patients with gastric cancer.

The Tumor Microenvironment in Follicular Lymphoma: Its Pro-Malignancy Role with Therapeutic Potential

In the follicular lymphoma (FL) microenvironment, CXCR5⁺ICOS⁺PD1⁺BCL6⁺ follicular helper T (Tfh) cells, which closely correlate with FL B cells in neoplastic follicles, play a major role in supporting FL. Interleukin-4 secreted by Tfh cells triggers the upregulation of the lymphocyte chemoattractant CXCL12 in stromal cell precursors, in particular by fibroblastic reticular cells (FRCs). In turn, mesenchymal stem cells (MSCs) can be committed to FRC differentiation in the bone marrow and lymph nodes involved by FL. Noteworthy, MSCs can promote the differentiation of Tfh cells into highly immunosuppressive T-follicular regulatory cells. The tumor suppressor HVEM is highly mutated in FL cells, and its deficiency increases Tfh cell frequency. In contrast, PI3Kδ inhibition impedes the recruitment of Tfh/regulatory T cells and impairs the proliferation of follicular dendritic cells (FDCs) and FDC-induced angiogenesis. Since TIGIT ligands are expressed by FDCs, the immune checkpoint receptor TIGIT plays an important role in tumor-infiltrating T cells. Thus, TIGIT blockade might invigorate cytotoxic T cells in the FL microenvironment. Given their potential to simultaneously reduce the neoplastic B cells, Tfh, and TFR cells could also reinforce the effects of the cytotoxic T cells. This combinatory strategy should be explored as a treatment option to tackle FL.

Improved Functionality of Exhausted Intrahepatic CXCR5+ CD8+ T Cells Contributes to Chronic Antigen Clearance Upon Immunomodulation

Chronic hepatotropic viral infections are characterized by exhausted CD8+ T cells in the presence of cognate antigen in the liver. The impairment of T cell response limits the control of chronic hepatotropic viruses. Immune-modulatory strategies are attractive options to re-invigorate exhausted T cells. However, in hepatotropic viral infections, the knowledge about immune-modulatory effects on the in-situ regulation of exhausted intrahepatic CD8+ T cells is limited. In this study, we elucidated the functional heterogeneity in the pool of exhausted CD8+ T cells in the liver of mice expressing the model antigen Ova in a fraction of hepatocytes. We found a subpopulation of intrahepatic CXCR5+ Ova-specific CD8+ T cells, which are profoundly cytotoxic, exhibiting efficient metabolic functions as well as improved memory recall and self-maintenance. The intrahepatic Ova-specific CXCR5+ CD8+ T cells are possibly tissue resident cells, which may rely largely on OXPHOS and glycolysis to fuel their cellular processes. Importantly, host conditioning with CpG oligonucleotide reinvigorates and promotes exhausted T cell expansion, facilitating complete antigen eradication. The CpG oligonucleotide-mediated reinvigoration may support resident memory T cell formation and the maintenance of CXCR5+ Ova-specific CD8+ T cells in the liver. These findings suggest that CpG oligodinucleotide may preferentially target CXCR5+ CD8+ T cells for expansion to facilitate the revival of exhausted T cells. Thus, therapeutic strategies aiming to expand CXCR5+ CD8+ T cells might provide a novel approach against chronic liver infection.

The Complex Role of Regulatory T Cells in Immunity and Aging

The immune system is a tightly regulated network which allows the development of defense mechanisms against foreign antigens and tolerance toward self-antigens. Regulatory T cells (Treg) contribute to immune homeostasis by maintaining unresponsiveness to self-antigens and suppressing exaggerated immune responses. Dysregulation of any of these processes can lead to serious consequences. Classically, Treg cell functions have been described in CD4⁺ T cells, but other immune cells also harbour the capacity to modulate immune responses. Regulatory functions have been described for different CD8⁺ T cell subsets, as well as other T cells such as γδT cells or NKT cells. In this review we describe the diverse populations of Treg cells and their role in different scenarios. Special attention is paid to the aging process, which is characterized by an altered composition of immune cells. Treg cells can contribute to the development of various age-related diseases but they are poorly characterized in aged individuals. The huge diversity of cells that display immune modulatory functions and the lack of universal markers to identify Treg make the expanding field of Treg research complex and challenging. There are still many open questions that need to be answered to solve the enigma of regulatory T cells.

CXCR5 CAR-T cells simultaneously target B cell non-Hodgkin's lymphoma and tumor-supportive follicular T helper cells

CAR-T cell therapy targeting CD19 demonstrated strong activity against advanced B cell leukemia, however shows less efficacy against lymphoma with nodal dissemination. To target both B cell Non-Hodgkin’s lymphoma (B-NHLs) and follicular T helper (Tfh) cells in the tumor microenvironment (TME), we apply here a chimeric antigen receptor (CAR) that recognizes human CXCR5 with high avidity. CXCR5, physiologically expressed on mature B and Tfh cells, is also highly expressed on nodal B-NHLs. Anti-CXCR5 CAR-T cells eradicate B-NHL cells and lymphoma-supportive Tfh cells more potently than CD19 CAR-T cells in vitro, and they efficiently inhibit lymphoma growth in a murine xenograft model. Administration of anti-murine CXCR5 CAR-T cells in syngeneic mice specifically depletes endogenous and malignant B and Tfh cells without unexpected on-target/off-tumor effects. Collectively, anti-CXCR5 CAR-T cells provide a promising treatment strategy for nodal B-NHLs through the simultaneous elimination of lymphoma B cells and Tfh cells of the tumor-supporting TME.

CAR-T cell therapy targeting CD19 is not as efficient to treat lymphoma with nodal dissemination as it is for B cell leukaemia. Here, the authors generate CAR-T cells against CXCR5 and show they inhibit tumour growth by depleting both B and follicular T helper cells in lymphoma models.

Biased agonism at chemokine receptors

In the human chemokine system, interactions between the approximately 50 known endogenous chemokine ligands and 20 known chemokine receptors (CKRs) regulate a wide range of cellular functions and biological processes including immune cell activation and homeostasis, development, angiogenesis, and neuromodulation. CKRs are a family of G protein-coupled receptors (GPCR), which represent the most common and versatile class of receptors in the human genome and the targets of approximately one third of all Food and Drug Administration-approved drugs. Chemokines and CKRs bind with significant promiscuity, as most CKRs can be activated by multiple chemokines and most chemokines can activate multiple CKRs. While these ligand-receptor interactions were previously regarded as redundant, it is now appreciated that many chemokine:CKR interactions display biased agonism, the phenomenon in which different ligands binding to the same receptor signal through different pathways with different efficacies, leading to distinct biological effects. Notably, these biased responses can be modulated through changes in ligand, receptor, and or the specific cellular context (system). In this review, we explore the biochemical mechanisms, functional consequences, and therapeutic potential of biased agonism in the chemokine system. An enhanced understanding of biased agonism in the chemokine system may prove transformative in the understanding of the mechanisms and consequences of biased signaling across all GPCR subtypes and aid in the development of biased pharmaceuticals with increased therapeutic efficacy and safer side effect profiles.

Identification and validation of an excellent prognosis subtype of muscle-invasive bladder cancer patients with intratumoral CXCR5+ CD8+ T cell abundance

Bladder cancer is the ninth most frequent-diagnosed disease worldwide, bearing high morbidity and mortality rates. Studies have shown that a particular population of CXCR5⁺CD8⁺ T cells was associated with superior prognosis in various tumor types, and yet its role in muscle-invasive bladder cancer (MIBC) remains unclear. In this study, 662 MIBC patients from 3 cohorts (Zhongshan Hospital, n = 141; Shanghai Cancer Center, n = 108; The Cancer Genome Atlas, n = 403) were analyzed retrospectively. 11 fresh resected samples of MIBC were examined to characterize the phenotype of CXCR5⁺CD8⁺ T cells and 402 MIBC patients from TCGA were applied for bioinformatics analysis. It was explored that the abundance of intratumoral CXCR5⁺CD8⁺ T cells indicated superior overall survival and disease-free survival. Patients with a higher infiltration of CXCR5⁺CD8⁺ T cells in tumor tissue benefit more from adjuvant chemotherapy (ACT). Intratumoral CXCR5⁺CD8⁺ T cells displayed cytolytic and self-renewal features. Remarkably, CXCR5⁺CD8⁺ T cells were mainly presented in the basal and stromal-rich subtypes of MIBC and tumors with enriched CXCR5⁺CD8⁺ T cells showed limited FGFR3 signaling signature and activated immunotherapeutic and EGFR associated pathway. In conclusion, we identified an excellent prognosis and ACT sensitive subtype of MIBC with intratumoral CXCR5⁺CD8⁺ T cell abundance. Tumors with high density of CXCR5⁺CD8⁺ T cells possessed potential sensitivity to immunotherapy and EGFR-targeted therapy. CXCR5⁺CD8⁺ T cells provide a new potential biomarker as well as a therapeutic target in MIBC.

Cancer and HIV-1 Infection: Patterns of Chronic Antigen Exposure

The main role of the human immune system is to eliminate cells presenting foreign antigens and abnormal patterns, while maintaining self-tolerance. However, when facing highly variable pathogens or antigens very similar to self-antigens, this system can fail in completely eliminating the anomalies, leading to the establishment of chronic pathologies. Prototypical examples of immune system defeat are cancer and Human Immunodeficiency Virus-1 (HIV-1) infection. In both conditions, the immune system is persistently exposed to antigens leading to systemic inflammation, lack of generation of long-term memory and exhaustion of effector cells. This triggers a negative feedback loop where effector cells are unable to resolve the pathology and cannot be replaced due to the lack of a pool of undifferentiated, self-renewing memory T cells. In addition, in an attempt to reduce tissue damage due to chronic inflammation, antigen presenting cells and myeloid components of the immune system activate systemic regulatory and tolerogenic programs. Beside these homologies shared between cancer and HIV-1 infection, the immune system can be shaped differently depending on the type and distribution of the eliciting antigens with ultimate consequences at the phenotypic and functional level of immune exhaustion. T cell differentiation, functionality, cytotoxic potential and proliferation reserve, immune-cell polarization, upregulation of negative regulators (immune checkpoint molecules) are indeed directly linked to the quantitative and qualitative differences in priming and recalling conditions. Better understanding of distinct mechanisms and functional consequences underlying disease-specific immune cell dysfunction will contribute to further improve and personalize immunotherapy. In the present review, we describe relevant players of immune cell exhaustion in cancer and HIV-1 infection, and enumerate the best-defined hallmarks of T cell dysfunction. Moreover, we highlight shared and divergent aspects of T cell exhaustion and T cell activation to the best of current knowledge.

CXC Chemokine Receptors in the Tumor Microenvironment and an Update of Antagonist Development

Chemokine receptors, a diverse group within the seven-transmembrane G protein-coupled receptor superfamily, are frequently overexpressed in malignant tumors. Ligand binding activates multiple downstream signal transduction cascades that drive tumor growth and metastasis, resulting in poor clinical outcome. These receptors are thus considered promising targets for anti-tumor therapy. This article reviews recent studies on the expression and function of CXC chemokine receptors in various tumor microenvironments and recent developments in cancer therapy using CXC chemokine receptor antagonists.

Toward T Cell-Mediated Control or Elimination of HIV Reservoirs: Lessons From Cancer Immunology

As the AIDS epidemic unfolded, the appearance of opportunistic infections in at-risk persons provided clues to the underlying problem: a dramatic defect in cell-mediated immunity associated with infection and depletion of CD4⁺ T lymphocytes. Moreover, the emergence of HIV-associated malignancies in these same individuals was a clear indication of the significant role effective cellular immunity plays in combating cancers. As research in the HIV field progressed, advances included the first demonstration of the role of PD-1 in human T cell exhaustion, and the development of gene-modified T cell therapies, including chimeric antigen receptor (CAR) T cells. In the intervening years, the oncology field has capitalized on these advances, effectively mobilizing the cellular immune response to achieve immune-mediated remission or cure of previously intractable cancers. Although similar therapeutic advances have not yet been achieved in the HIV field, spontaneous CD8⁺ T cell mediated remission or functional cure of HIV infection does occur in very small subset of individuals in the absence of anti-retroviral therapy (ART). This has many similarities to the CD8⁺ T cell mediated functional control or elimination of cancers, and indicates that immunotherapy for HIV is a rational goal. In HIV infection, one major barrier to successful immunotherapy is the small, persistent population of infected CD4⁺ T cells, the viral reservoir, which evades pharmacological and immune-mediated clearance, and is largely maintained in secondary lymphoid tissues at sites where CD8⁺ T cells have limited access and/or function. The reservoir-enriched lymphoid microenvironment bears a striking resemblance to the tumor microenvironment of many solid tumors–namely high levels of anti-inflammatory cytokines, expression of co-inhibitory receptors, and physical exclusion of immune effector cells. Here, we review the parallels between CD8⁺ T cell-mediated immune control of HIV and cancer, and how advances in cancer immunotherapy may provide insights to direct the development of effective HIV cure strategies. Specifically, understanding the impact of the tissue microenvironment on T cell function and development of CAR T cells and therapeutic vaccines deserve robust attention on the path toward a CD8⁺ T cell mediated cure of HIV infection.