scholarly journals 754 TIGIT-PVR is a key immune checkpoint and therapeutic target in HPV-positive head and neck squamous cell carcinomas

2021 ◽  
Vol 9 (Suppl 3) ◽  
pp. A788-A788
Author(s):  
Xiuning Le ◽  
Minghao Dang ◽  
Venkatesh Hegde ◽  
Bo Jiang ◽  
Ravaen Slay ◽  
...  

BackgroundHuman papillomavirus (HPV)-positive head and neck squamous cell carcinoma (HPV+ HNSCC) is a disease that has moderate response to anti-PD-1/L1 immune checkpoint blockade, with the response rates less than 20% and median progression-free survival less than 3 months. A greater understanding of tumor intrinsic and extrinsic factors that restrict anti-tumor immunity in the tumor immune microenvironment (TIME) is needed to identify other immune checkpoints to enhance therapeutic efficacy.MethodsTwo cohorts (TCGA n=72 and a separate cohort n=84) of surgically resected, treatment-naïve HPV+ HNSCC with RNA-seq were analyzed to understand the immune features. In addition, single-cell RNA-seq and TCR-seq were performed on 18 cases to further delineate the immune molecules' interactions. An immune-competent murine HPV+ HNSCC model was used to preliminarily evaluate the therapeutic efficacy.ResultsIn two bulk-sequenced HPV+ HNSCC cohorts, TIGIT ligands PVR and NECTIN2 were found to associate with an epithelial-to-mesenchymal gene expression signature, suppression of IFNα and IFNγ signaling, a stromal-enriched or immune-excluded TIME, and poor survival. Single-cell RNA-seq of over 72,000 cells of HPV+ HNSCC revealed that the PVR/NECTIN ligand TIGIT was highly prevalent in T-cells (34%), significantly higher than PD1- (20%, p<0.01). There is an enrichment of cell-cell interactions mediated by TIGIT-PVR/NECTIN2 in the TIME of HPV+HNSCC versus normal tonsil. TIGIT was the most differentially upregulated immune checkpoint on clonally expanded CD8+T-cells and was abundant on antigen-experienced, tissue-resident memory CD8+T-cell and T-regulatory subsets. TIGIT ligands PVR, NECTIN1, and NECTIN2 were abundant on mature regulatory dendritic cells (DCs), immunosuppressive plasmacytoid (p)DCs, and macrophages, respectively. TIGIT and PD-1 co-blockade in the mEER syngeneic murine model significantly reduced tumor growth, improved survival, restored effector function of HPV16E7-specific CD8+T cells, natural killer cells, and DCs, and conferred tumor re-challenge protection.ConclusionsTIGIT-PVR/NECTIN receptors/ligands are more abundant than PD-1/L1 in the TIME of HPV+ HNSCC. Co-blockade of TIGIT and PD-1 immune checkpoints enhanced anti-tumor efficacy in a CD8+ T-cell-dependent manner and conferred long-term immune protection in a murine model. Our study nominates TIGIT as a therapeutic target for HPV+ HNSCC.

2021 ◽  
Author(s):  
Joy A. Pai ◽  
Andrew Chow ◽  
Jennifer Sauter ◽  
Marissa Mattar ◽  
Hira Rizvi ◽  
...  

Paired T cell receptor and RNA single cell sequencing (scTCR/RNA-seq) has allowed for enhanced resolution of clonal T cell dynamics in cancer. Here, we report a scTCR/RNA-seq dataset of 162,062 single T cells from 31 tissue regions, including tumor, adjacent normal tissues, and lymph nodes (LN), from three patients who underwent resections for progressing lung cancers after immune checkpoint blockade (ICB). We found marked regional heterogeneity in tumor persistence that was associated with heterogeneity in CD4 and CD8 T cell phenotypes; regions with persistent cancer cells were enriched for follicular helper CD4 T cells (TFH), regulatory T cells (Treg), and exhausted CD8 T cells. Clonal analysis demonstrated that highly-expanded T cell clones were predominantly of the CD8 subtype, were ubiquitously present across all sampled regions, found in the peripheral circulation, and expressed gene signatures of 'large' and 'dual-expanded' clones that have been predictive of response to ICB. Longitudinal tracking of CD8 T cell clones in the peripheral blood revealed that the persistence of ubiquitous CD8 T cell clones, as well as phenotypically distinct clones with tumor-reactive features, correlated with systemic tumor control. Finally, tracking CD8 T cell clones across tissues revealed the presence of TCF-1+ precursor exhausted CD8 T cells in tumor draining LNs that were clonally linked to expanded exhausted CD8 T cells in tumors. Altogether, this comprehensive scTCR/RNA-seq dataset with regional, longitudinal, and clonal resolution provides fundamental insights into the tissue distribution, persistence, and differentiation trajectories of ICB-responsive T cells that underlie clinical responses to ICB.


2021 ◽  
Vol 9 (Suppl 3) ◽  
pp. A338-A338
Author(s):  
Berengere Salome ◽  
John Sfakianos ◽  
Andrew Charap ◽  
Adam Farkas ◽  
Daniel Geanon ◽  
...  

BackgroundBladder cancer is characterized by a poor prognosis, with muscle-invasive cases harboring a 34–76% 10-year recurrence-free survival rate.1 Neoadjuvant PD-1/PD-L1 blockade strategies have recently been approved by the US Food and Drug Administration for bladder cancer treatment, yet only achieving a complete response rate of 31–37%, thereby suggesting additional mechanisms of resistance.2 HLA-E is a known inhibitor of NKG2A+ CD8 T cells and NK cell responses. A monoclonal antibody binding to the NKG2A receptor has been developed and proven to restore CD8 T cell and NK cell responses in head and neck cancer, with ongoing clinical trials across multiple tumor indications.3 4 We evaluated the potential role of the HLA-E/NKG2A inhibitory pathway in modulating T cell immunity in bladder cancer.MethodsCyTOF was performed on CD8+ T cells from fresh bladder tumors (n=6), as well as on expanded CD8+ T cells from bladder-draining lymph nodes (n=11) and tumors (n=8). Flow cytometry (n=25) and single-cell RNA-sequencing (scRNAseq) (n=13) were performed on cells from fresh bladder tumors.ResultsMechanisms of tumor escape from CD8+ T cell recognition include impairment of antigen presentation. Accordingly, we found a significant reduction of HLA class I expression on tumors. However, expression of DNAM-1-activating ligands (e.g. CD112,CD155) on bladder tumors was retained, indicating a possible role for TCR-independent activation pathways traditionally ascribed to natural killer (NK) cells. Using mass cytometry and scRNAseq, we observed that acquisition of NKG2A on tumor-derived PD-1+ CD8+ T cells promotes tissue-resident memory features alongside diminished CD28 expression and significantly weaker sensitivity to CD3/CD28-signaling. However, NKG2A+ CD8 T cells possess a proliferative advantage with enhanced expression of DNAM-1 and cytolytic machinery.Strikingly, we found that NKG2A+PD-1+ CD8 T cells are strongly activated in response to HLA class I-deficient tumors compared to their NKG2A- PD-1+ CD8 T cell counterparts. TCR-independent NK-like function by NKG2A+ CD8 T cell is partly mediated by the DNAM-1 pathway and inhibited by HLA-E. NKG2A+ CD8 T cell functions are restored upon NKG2A blockade, where efficiency positively correlates with HLA-E expression on bladder tumors.ConclusionsCollectively, our data indicate that NKG2A+ CD8 T cells display a strong capacity for TCR-independent activation that enables them to circumvent bladder tumor evasion mechanisms. NKG2A+ CD8 T cells lack expression of CD28 suggesting a lower susceptibility to PD-1-mediated inhibiton. Our data suggest a need for thorough reappraisal of current protocols that assess CD8 T cell exhaustion and for strategies to restore their antitumor functions.ReferencesSanli O, Dobruch J, Knowles MA, Burger M, Alemozaffar M, Nielsen ME, Lotan Y. Bladder cancer. Nat Rev Dis Primers 2017 April 13;3:17022. doi: 10.1038/nrdp.2017.22. PMID: 28406148. Rouanne M, Bajorin DF, Hannan R, Galsky MD, Williams SB, Necchi A, Sharma P, Powles T. Rationale and outcomes for neoadjuvant immunotherapy in urothelial carcinoma of the bladder. Eur Urol Oncol 2020 December;3(6):728–738. doi: 10.1016/j.euo.2020.06.009. Epub 2020 Nov 8. PMID: 33177001. André P, Denis C, Soulas C, Bourbon-Caillet C, Lopez J, Arnoux T, Bléry M, Bonnafous C, Gauthier L, Morel A, Rossi B, Remark R, Breso V, Bonnet E, Habif G, Guia S, Lalanne AI, Hoffmann C, Lantz O, Fayette J, Boyer-Chammard A, Zerbib R, Dodion P, Ghadially H, Jure-Kunkel M, Morel Y, Herbst R, Narni-Mancinelli E, Cohen RB, Vivier E. Anti-NKG2A mAb is a checkpoint inhibitor that promotes anti-tumor immunity by unleashing both T and NK Cells. Cell 2018 December 13;175(7):1731–1743.e13. doi: 10.1016/j.cell.2018.10.014. Epub 2018 Nov 29. PMID: 30503213; PMCID: PMC6292840. van Hall T, André P, Horowitz A, Ruan DF, Borst L, Zerbib R, Narni-Mancinelli E, van der Burg SH, Vivier E. Monalizumab: inhibiting the novel immune checkpoint NKG2A. J Immunother Cancer 2019 October 17;7(1):263. doi: 10.1186/s40425-019-0761-3. PMID: 31623687; PMCID: PMC6798508.


Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 4132-4132
Author(s):  
Marzia Palma ◽  
Giusy Gentilcore ◽  
Fariba Mozaffari ◽  
Kia Heimersson ◽  
Barbro Näsman-Glaser ◽  
...  

Abstract Background CLL patients (pts) have impaired humoral and cellular immune functions, which is largely due to profound defects of T-cells. Regulation and activation of T lymphocytes depend not only on T cell receptor signaling but also on co-signaling receptors delivering either inhibitory or stimulatory signals, known as immune checkpoints. CTLA-4 (cytotoxic T lymphocyte-associated antigen-4) is transiently expressed on activated T cells, binding the same ligands as CD28, inhibiting T-cell activation. Similarly, programmed cell death protein 1 (PD-1) is expressed on activated CD4+ and CD8+ T cells inhibiting T-cell functions upon binding to the ligands B7-H1 (PD-L1, CD274) and B7-DC (PD-L2, CD273). CD137 is an inducible costimulatory receptor expressed by activated T cells. Dysregulated expression of immune checkpoint receptors on T cells of CLL pts may have an impact on T-cell responsiveness and might be a mechanism for the immune deficiency in the disease. Aim To evaluate the expression of the immune checkpoint molecules CTLA-4, PD-1 and CD137 as well as of the cell proliferation marker Ki67, the activation marker CD69 and of CD103, a marker expressed on regulatory T cells, in T cells from CLL pts in different disease phases. Methods Peripheral blood samples were obtained from 69 CLL pts and 13 healthy control donors (HD). Pts were sub-grouped according to disease phase: indolent vs progressive (i.e. fulfilling criteria for active disease). The expression of CTLA-4, PD-1, PD-L1, CD69, CD103, CD137 and Ki-67 was assessed by flow-cytometry on CD4+ and CD8+ T cells. We also analysed the change in expression of these markers on T cells after 72 hours of PHA stimulation. Results CLL pts (n=17) had a significanty higher percentage of proliferating (Ki67+) CD3+ cells compared to HD (n=7) (median 3.7% in progressive vs 1.7% in indolent CLL vs 0.9% in HD, p=0.004 and p=0.04, respectively) (Fig.1). Progressive CLL pts had a significantly higher percentage Ki67+ CD4+ compared to indolent pts as well as HD (p=0.007 and p=0.001, respectively). Both indolent and progressive pts had higher percentage of Ki67+ CD8+ T cells compared to HD (p=0.01 and p=0.03, respectively). The percentage of CTLA-4+ CD4+ and CTLA-4+ CD8+ cells was low in CLL pts as well as in HD. However, the percentage of PD-1+ CD4+ T cells was significantly higher in progressive (n=32) as compared to indolent (n=35) CLL pts (median 40.3% vs 23.3%, p<0.0001) and HD (n=13) (median 21.5%, p<0.0001) (Fig.2) and correlated positively to the white blood cell counts (WBC) at the time of testing (r=0.29, p=0.03), while no difference was found with regard to the percentage of PD-1+ CD8+ T cells. No difference was observed between CLL pts and HD regarding the expression of PD-L1 on T cells. Both the percentage of CD69+ CD4+ and CD137+ CD4+ T cells were significantly higher in progressive as compared to indolent disease and correlated positively to WBC while no difference was found seen in CD8+ T cells. The percentage of CD103+ T cells was significantly lower in progressive compared to and HD within both the CD4+ (p=0.02) and the CD8+ subpopulations (p=0.02). After 72-hrs of PHA stimulation, PD-1 and CTLA-4 expression increased in CD4+ and CD8+ cells to a similar extent in CLL pts and HD, while PD-L1 increased in HD but not in progressive CLL pts (p=0.03 and p=0.007 for CD4+ and CD8+ cells, respectively). CD69 expression increased to a similar extent in CLL pts and HD, while CD137 expression increased more in T cells from progressive pts compared to HD (p=0.03 and 0.01 for the CD4+ and CD8+ cells, respectively). No increase in CD103 on CD8+ T-cells was observed in CLL pts compared to HD (p=0.04 and p=0.01 for the indolent and progressive pts, respectively). Conclusions Progressive CLL pts have more proliferating (Ki67+) T cells in both the CD4+ and CD8+ compartments compared to HD. CD4+ T-cells in progressive CLL pts display an activated phenotype (CD69+) and express the immune co-stimulatory molecule CD137 at a significantly higher level compared to indolent pts and HD. Nevertheless, the expression of the inhibitory immune checkpoint molecule PD-1 is so high that it is reasonable to assume that these cells are heavily impaired in their immune functions. The differences observed in the expression of immune checkpoints and activation markers between CLL pts in different phases of the disease suggest that major changes occur in the CD4+ T-cell compartment during disease progression. Figure 1. Figure 1. Figure 2. Figure 2. Disclosures Hansson: Jansse Cilag: Research Funding. Österborg:Janssen, Pharmacyclics, Gilead: Consultancy, Research Funding; Novartis: Research Funding.


2019 ◽  
Vol 78 (11) ◽  
pp. 1566-1575 ◽  
Author(s):  
Zoya Qaiyum ◽  
Eric Gracey ◽  
YuChen Yao ◽  
Robert D Inman

ObjectivesCurrent evidence suggests that immune events in the gut may impact joint inflammation in ankylosing spondylitis (AS) but the expression of gut-related trafficking molecules in the inflammed joint is poorly characterised. We aimed to (1) assess differential expression patterns of trafficking molecules between patients and controls, (2) generate joint-specific cellular signatures and (3) obtain transcriptomic profiles of noteworthy cell subpopulations.MethodsMale subjects under 40 years of age fulfilling the mNY criteria were recruited. The following cells were surface stained using a 36-marker mass cytometry antibody panel: (1) peripheral blood mononuclear cells from AS patients, and healthy controls; (2) synovial fluid mononuclear cells from AS and rheumatoid arthritis (RA) patients. Additionally, RNA-seq was performed on CD8+ T cell subpopulations from the synovial fluid (SF).ResultsMature CD8+ T cells were enriched in AS SF, with a distinct pattern of integrin expression (β7, CD103, CD29 and CD49a). RNA-seq analysis of SF-derived CD103+CD49a+CD8+ T cells revealed elevated TNFAIP3, GZMB, PRF1 and IL-10.ConclusionsWe have identified a novel integrin-expressing mature CD8+ T cell population (CD49a+CD103+β7+CD29+) that appears to be more prevalent in AS SF than RA SF. These cells seem to possess dual cytotoxic and regulatory profiles which may play a role in AS pathogenesis.


2021 ◽  
Author(s):  
Stefan Naulaerts ◽  
Daniel M Borras ◽  
Asier Antoranz Martinez ◽  
Julie Messiaen ◽  
Yannick Van Herck ◽  
...  

Tumoural-CD8+T cells exhibit exhausted or dysfunctional states. Contrary to immunotherapy-responsive exhausted-CD8+T cells, the clinical features of dysfunctional-CD8+T cells are disputed. Hence, we conducted large-scale multi-omics and multi-dimensional mapping of CD8+T cell-states across multiple cancer patient-cohorts. This identified tumour-specific continuum of CD8+T cell-states across 6 human cancers, partly imprinted by organ-specific immuno-modulatory niches. Herein, melanoma and glioblastoma enriched prototypical exhausted (CD8+TEXT) and severely-dysfunctional (CD8+TSDF) states, respectively. Contrary to CD8+TEXT, CD8+TSDF displayed transcriptomic and epigenetic effector/cytolytic dysfunctions, and dysregulated effector/memory single-cell trajectories, culminating into maladaptive pro-death stress and cell-cycle defects. Suboptimal antigen-priming underscored CD8+TSDF, which was distinct from immune-checkpoints 'rich' CD8+TEXT, reflecting chronic antigen-stimulation. Continuum variation also existed on tumour spatial-level, with convergent (CD8+TEXT-supportive vascular regions) and divergent features (dysfunctional CD4+T::CD8+TSDF cell-to-cell interactions) between melanoma and glioblastoma. Globally, IFNG-IL2 disparities, paucity of intra-tumoural CD4+/CD8+T cells, and myeloid TGFB/wound healing responses, distinguished CD8+TSDF-landscape. Within immuno-oncology clinical-trials, anti-PD1 immunotherapy failed to 'reinvigorate' CD8+TSDF-landscape, and instead facilitated effector-dysfunction and TGFB/wound healing. However, cellular immunotherapies (dendritic cell-vaccines, adoptive T-cell therapy) ameliorated assorted CD8+TSDF-landscape disparities, highlighting a roadmap for anti-glioblastoma multimodal-immunotherapy. Collectively, our study comprehensively expands clinical-knowledge on CD8+T cell-exhaustion and suggests that tumour-specific, pre-existing CD8+TEXT/TSDF-states, determine immunotherapy-responses.


2021 ◽  
Vol 12 ◽  
Author(s):  
Danielle M. Clements ◽  
Brenndan Crumley ◽  
Glen M. Chew ◽  
Elijah Davis ◽  
Roberta Bruhn ◽  
...  

Human T-cell lymphotropic virus type 1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) develops in 1–5% of HTLV-1-infected individuals. Previous studies by us and others have shown that the expression of negative immune checkpoint receptors (NCRs) is significantly increased on CD8 T cells in various chronic viral infections and are associated with poor anti-viral immunity. We have previously identified the differential expression of NCRs on CD8 T cells in blood from patients with HAM/TSP and in central nervous system (CNS) tissues of HTLV-1 infected humanized mice and defined the association with neurological complications. In this study, we determined the co-expression patterns of several key NCRs (PD-1, TIGIT, TIM-3, and LAG-3) and their cognate ligands in HTLV-1 infection and assessed how combination strategies targeting these pathways would impact HTLV-1-specific CD8 T-cell effector functions as an approach to reduce CNS disease outcomes. We found that global CD8 T cells from HAM/TSP patients co-express multiple NCRs at significantly higher frequencies than asymptomatic carriers (AC). Moreover, NCR ligands (PVR and PD-LI) on both plasmacytoid and myeloid dendritic cells were also expressed at higher frequencies in HAM/TSP compared to AC. In both AC and HAM/TSP subjects, combination dual PD-L1/TIGIT or triple PD-L1/TIGIT/TIM-3 blockade with monoclonal antibodies resulted in increases in intracellular cytokine expression in CD8 T cells after virus stimulation, particularly CD107a, a marker of degranulation, and TNF-α, a key cytokine that can directly inhibit viral replication. Interestingly, almost all blockade combinations resulted in reduced IL-2+ HTLV-1-specific CD8 T cell frequencies in HAM/TSP subjects, but not in AC. These results define a novel combinatorial NCR immunotherapeutic blockade strategy to reduce HAM/TSP disease burden.


Cells ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 37
Author(s):  
Sarah Schäfer ◽  
Alma Zernecke

Atherosclerotic lesions are populated by cells of the innate and adaptive immune system, including CD8+ T cells. The CD8+ T cell infiltrate has recently been characterized in mouse and human atherosclerosis and revealed activated, cytotoxic, and possibly dysfunctional and exhausted cell phenotypes. In mouse models of atherosclerosis, antibody-mediated depletion of CD8+ T cells ameliorates atherosclerosis. CD8+ T cells control monopoiesis and macrophage accumulation in early atherosclerosis. In addition, CD8+ T cells exert cytotoxic functions in atherosclerotic plaques and contribute to macrophage cell death and necrotic core formation. CD8+ T cell activation may be antigen-specific, and epitopes of atherosclerosis-relevant antigens may be targets of CD8+ T cells and their cytotoxic activity. CD8+ T cell functions are tightly controlled by costimulatory and coinhibitory immune checkpoints. Subsets of regulatory CD25+CD8+ T cells with immunosuppressive functions can inhibit atherosclerosis. Importantly, local cytotoxic CD8+ T cell responses may trigger endothelial damage and plaque erosion in acute coronary syndromes. Understanding the complex role of CD8+ T cells in atherosclerosis may pave the way for defining novel treatment approaches in atherosclerosis. In this review article, we discuss these aspects, highlighting the emerging and critical role of CD8+ T cells in atherosclerosis.


2018 ◽  
Vol 47 (6) ◽  
pp. 2187-2198 ◽  
Author(s):  
Zhen Zhang ◽  
Chaoqi Zhang ◽  
Feng Li ◽  
Bin Zhang ◽  
Yi Zhang

MicroRNAs (miRNAs) have emerged as crucial regulators of T lymphocyte survival, differentiation and function, all of which are key factors impacting the outcome of adoptive T cell-based immunotherapy. It has become increasingly clear that the adoptive transfer of memory CD8+ T cell subsets is highly correlated with objective clinical responses for patients with advanced cancer. However, it is unclear how to improve the long-term persistence of transferred CD8+ T cells using miRNAs. Here, we highlight the current advances in our understanding of the role of miRNAs in regulating the differentiation of memory CD8+ T cells. We specifically discuss the effect of miRNAs on key transcription factors, immune checkpoints and signal pathways, which contribute to the differentiation of effector and memory T cell subsets. Ultimately, miRNAs may be easily integrated into existing T cell receptor (TCR) and chimeric antigen receptor (CAR) platforms to promote adoptive T cell therapy with multiple advantages. Thus, combining T cell-based therapy with miRNAs could be considered a promising and robust strategy for cancer treatment.


2019 ◽  
Vol 5 (3) ◽  
pp. 63
Author(s):  
Alice Bayiyana ◽  
Samuel Okurut ◽  
Rose Nabatanzi ◽  
Godfrey Zziwa ◽  
David R. Boulware ◽  
...  

Despite improvement in the prognosis of HIV/AIDS (human immunodeficiency virus/acquired immune deficiency syndrome) patients on antiretroviral therapy (ART), cryptococcal meningitis (CM) still causes 10–15% mortality among HIV-infected patients. The immunological impact of ART on the CD4+ and CD8+ T cell repertoire during cryptococcal co-infection is unclear. We determined longitudinal phenotypic changes in T cell subsets among patients with CM after they initiated ART. We hypothesized that ART alters the clonotypic phenotype and structural composition of CD4+ and CD8+ T cells during CM co-infection. For this substudy, peripheral blood mononuclear cells (PBMC) were isolated at four time points from CM patients following ART initiation during the parent study (ClinicalTrials.gov number, NCT01075152). Phenotypic characterization of CD4+ and CD8+ T cells was done using T cell surface marker monoclonal antibodies by flow cytometry. There was variation in the expression of immunophenotypic markers defining central memory (CD27+CD45R0+), effector memory (CD45R0+CD27–), immune activation (CD38+ and Human Leucocyte Antigen DR (HLA-DR+), and exhaustion (Programmed cell death protein one (PD-1) in the CD4+ T cell subset. In comparison to the CD4+ T cell population, the CD8+ central memory subset declined gradually with minimal increase in the effector memory subset. Both CD4+ and CD8+ T cell immune exhaustion and activation markers remained elevated over 12 weeks. The relative surge and decline in the expression of T cell surface markers outlines a variation in the differentiation of CD4+ T cells during ART treatment during CM co-infection.


Blood ◽  
2000 ◽  
Vol 96 (5) ◽  
pp. 1994-1995 ◽  
Author(s):  
Masako Moriuchi ◽  
Hiroyuki Moriuchi

Abstract Although it is widely believed that viral clearance is mediated principally by the destruction of infected cells by cytotoxic T cells, noncytolytic antiviral activity of CD8+ T cells may play a role in preventing the progression to disease in infections with immunodeficiency viruses and hepatitis B virus. We demonstrate here that (1) replication of human T-lymphotropic virus type I (HTLV-I) is more readily detected from CD8+ T-cell–depleted (CD8−) peripheral blood mononuclear cells (PBMCs) of healthy HTLV-I carriers than from unfractionated PBMCs, (2) cocultures of CD8− PBMCs with autologous or allogeneic CD8+ T cells suppressed HTLV-I replication, and (3) CD8+ T-cell anti-HTLV-I activity is not abrogated intrans-well cultures in which CD8+ cells are separated from CD8− PBMCs by a permeable membrane filter. These results suggest that class I-unrestricted noncytolytic anti–HTLV-I activity is mediated, at least in part by a soluble factor(s), and may play a role in the pathogenesis of HTLV-I infection.


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