The thymoproteasome in shaping the CD8+ T-cell repertoire

The thymoproteasome is a type of proteasome expressed specifically in thymic cortical epithelial cells. Thymoproteasome affects antigen processing of major histocompatibility complex (MHC)-I-associated peptides and optimizes positive selection of CD8+ T cells. However, it remains unanswered whether and how thymoproteasome-dependent MHC-I-associated self-peptides contribute to positive selection of cortical thymocytes. This short piece discusses the potential mechanisms of thymoproteasome contribution to positive selection of MHC-I-restricted CD8+ T cells.

Polymorphic KIR3DL3 expression modulates tissue-resident and innate-like T cells

Most human killer cell immunoglobulin-like receptors (KIR) are expressed by natural killer (NK) cells and recognize HLA class I molecules as ligands. KIR3DL3 is a conserved but polymorphic inhibitory KIR recognizing a B7 family ligand, HHLA2, and is implicated for immune checkpoint targeting. The expression profile and biological function of KIR3DL3 have been somewhat elusive, so we searched extensively for KIR3DL3 transcripts, revealing highly enriched expression in γδ and CD8+ T cells rather than NK cells. These KIR3DL3-expressing cells are rare in the blood and thymus but more common in the lungs and digestive tract. High-resolution flow cytometry and single-cell transcriptomics showed that peripheral blood KIR3DL3+ T cells have an activated transitional memory phenotype and are hypofunctional. The T cell receptor (TCR) usage is biased toward genes from early rearranged TCR-α variable segments or Vδ1 chains. In addition, we show that TCR-mediated stimulation can be inhibited through KIR3DL3 ligation. Whereas we detected no impact of KIR3DL3 polymorphism on ligand binding, variants in the proximal promoter and at residue 86 can reduce expression. Together, we demonstrate that KIR3DL3 is up-regulated alongside unconventional T cell stimulation and that individuals may vary in their ability to express KIR3DL3. These results have implications for the personalized targeting of KIR3DL3/HHLA2 checkpoint inhibition.

Interleukin-37 suppresses the cytotoxicity of hepatitis B virus peptides-induced CD8+ T cells in patients with acute hepatitis B

Interleukin-37 (IL-37) is a newly identified anti-inflammatory cytokine, owning immunosuppressive activity in infectious diseases. The aim of this study was to investigate the regulatory function of IL-37 on CD8+ T cells during hepatitis B virus (HBV) infection. Eighteen acute hepatitis B (AHB) patients, thirty-nine chronic hepatitis B (CHB) patients, and twenty controls were enrolled. IL-37 concentration was measured by ELISA. IL-37 receptor subunits expressions on CD8+ T cells were assessed by flow cytometry. Purified CD8+ T cells were stimulated with HBV peptides and recombinant IL-37. Perforin and granzyme B secretion was investigated by ELISPOT. Programmed death-1 (PD-1) and cytotoxic T-lymphocyte associated protein-4 (CTLA-4) mRNA expressions were semi-quantified by real-time PCR. CD8+ T cell cytotoxicity was assessed in direct contact and indirect contact coculture with HepG2.2.15 cells. Plasma IL-37 level was down-regulated and negatively correlated with aminotransferase levels in AHB patients. There were no significant differences of IL-37 receptor subunits among AHB patients, CHB patients, and controls. Exogenous IL-37 stimulation suppressed HBV peptides-induced perforin and granzyme B secretion by CD8+ T cells in AHB patients, but not in CHB patients. Exogenous IL-37 stimulation did not affect proinflammatory cytokines secretion as well as PD-1/CTLA-4 mRNA expressions in CD8+ T cells in AHB and CHB patients. Exogenous IL-37 stimulation dampened HBV peptide-induced CD8+ T cell cytotoxicity in a cell-to-cell contact manner. The current data indicated that acute HBV infection might induce down-regulation of IL-37, which might be associated with enhanced CD8+ T cell cytotoxicity and liver damage.

Aminobisphosphonates reactivate the latent reservoir in people living with HIV-1

Antiretroviral therapy (ART) is not curative due to the existence of cellular reservoirs of latent HIV-1 that persist during therapy. Current research efforts to cure HIV-1 infection include "shock and kill" strategies to disrupt latency using small molecules or latency-reversing agents (LRAs) to induce expression of HIV-1 enabling cytotoxic immune cells to eliminate infected cells. The modest success of current LRAs urges the field to identify novel drugs with increased clinical efficacy. Aminobisphosphonates (N-BPs) that include pamidronate, zoledronate, or alendronate, are the first-line treatment of bone-related diseases including osteoporosis and bone malignancies. Here, we show the use of N-BPs as a novel class of LRA: we found in ex vivo assays using primary cells from ART-suppressed people living with HIV-1 that N-BPs induce HIV-1 from latency to levels that are comparable to the T cell activator phytohemagglutinin (PHA). RNA sequencing and mechanistic data suggested that reactivation may occur through activation of the activator protein 1 signaling pathway. Stored samples from a prior clinical trial aimed at analyzing the effect of alendronate on bone mineral density, provided further evidence of alendronate-mediated latency reversal and activation of immune effector cells. Decay of the reservoir measured by IPDA was however not detected. Our results demonstrate the novel use of N-BPs to reverse HIV-1 latency while inducing immune effector functions. This preliminary evidence merits further investigation in a controlled clinical setting possibly in combination with therapeutic vaccination.

Helminth exposure protects against murine SARS-CoV-2 infection through macrophage dependent T cell activation

Helminth endemic regions report lower COVID-19 morbidity and mortality. Here, we show that lung remodeling from a prior infection with a lung migrating helminth, Nippostrongylus brasiliensis , enhances viral clearance and survival of human-ACE2 transgenic mice challenged with SARS-CoV-2 (SCV2). This protection is associated with a lymphocytic infiltrate including an increased accumulation of pulmonary SCV2-specific CD8+ T cells and anti-CD8 antibody depletion abrogated the N. brasiliensis -mediated reduction in viral loads. Pulmonary macrophages with a type-2 transcriptional signature persist in the lungs of N. brasiliensis exposed mice after clearance of the parasite and establish a primed environment for increased antigen presentation. Accordingly, depletion of macrophages ablated the augmented viral clearance and accumulation of CD8+ T cells driven by prior N. brasiliensis infection. Together, these findings support the concept that lung migrating helminths can limit disease severity during SCV2 infection through macrophage-dependent enhancement of anti-viral CD8+ T cell responses.

Abstract Figure

KDM6A Depletion in Breast Epithelial Cells Leads to Reduced Sensitivity to Anticancer Agents and Increased TGFβ Activity

KDM6A, an X chromosome-linked histone lysine demethylase, was reported to be frequently mutated in many tumor types including breast and bladder cancer. However, the functional role of KDM6A is not fully understood. Using MCF10A as a model of non-tumorigenic epithelial breast cells, we found that silencing KDM6A promoted cell migration and transformation demonstrated by the formation of tumor-like acini in three-dimensional culture. KDM6A loss reduced the sensitivity of MCF10A cells to therapeutic agents commonly used to treat patients with triple-negative breast cancer and also induced TGFβ extracellular secretion leading to suppressed expression of cytotoxic genes in normal human CD8+ T cells in vitro. Interestingly, when cells were treated with TGFβ, de novo synthesis of KDM6A protein was suppressed while TGFB1 transcription was enhanced, indicating a TGFβ/KDM6A-negative regulatory axis. Furthermore, both KDM6A deficiency and TGFβ treatment promoted disorganized acinar structures in three-dimensional culture, as well as transcriptional profiles associated with epithelial-to-mesenchymal transition and metastasis, suggesting KDM6A depletion and TGFβ drive tumor progression.

IMPLICATIONS

Our study provides the preclinical rationale for evaluating KDM6A and TGFβ in breast tumor samples as predictors for response to chemo and immunotherapy, informing personalized therapy based on these findings.

Changes in bone marrow and peripheral blood lymphocyte subset findings with onset of hepatitis-associated aplastic anemia

RATIONALE

Hepatitis-associated aplastic anemia (HAAA) is a rare illness that results in bone marrow failure following hepatitis development. The etiological agent remains unknown in most HAAA cases. However, clinical features of the disease and immunotherapy response indicate that immune-mediated factors play a central role in the pathogenesis of HAAA. Activation of cytotoxic T cells and increase in CD8 cells could exert cytotoxic effects on the myelopoietic cells in the bone marrow.

PATIENT CONCERNS

A 15-month-old boy was brought to our hospital with complaints of generalized petechiae and purpura observed a week prior to hospitalization. His liver was palpated 3 cm below the costal margin, platelet count was 0 × 104/μL, and alanine aminotransferase level was 1346 IU/L. A blood test indicated cytomegalovirus infection, and 3 bone marrow examinations revealed progressive HAAA. As the disease progressed to the 3rd, 6th, and 9th week after onset, CD4+ T cells were markedly decreased, CD8+ T cells were markedly increased, and the CD4/CD8 ratio was significantly decreased. The number of B cells and natural killer cells decreased with time, eventually reaching 0.0%.

DIAGNOSIS

HAAA.

INTERVENTIONS

Rabbit antithymocyte globulin and eltrombopag olamine (a thrombopoietin receptor agonist) were administered.

OUTCOMES

The patient's platelet count returned to normal, and bone marrow transplantation was avoided. The peripheral blood lymphocytes (PBLs) improved as the patient's general condition recovered.

LESSONS

This case demonstrates that HAAA induced by cytomegalovirus infection features decreasing CD4+ and increasing CD8+ PBLs as the bone marrow hypoplasia progresses. The PBLs return to their normal levels with the recovery from the disease. Our case findings thus support the involvement of immunological abnormality in HAAA.

Cholesterol-Lowering Intervention Decreases mTOR Complex 2 Signaling and Enhances Antitumor Immunity

PURPOSE

There is a need for strategies to prevent prostate cancer. Cholesterol-lowering interventions are employed widely and safely to reduce risk of cardiovascular disease and has been proposed for chemoprevention. Using preclinical models and a window-of-opportunity clinical trial, we describe an adaptive antitumor immunity resulting from cholesterol lowering.

EXPERIMENTAL DESIGN

Statins do not reliably lower serum cholesterol in mice. Therefore, oral ezetimibe was administered to mice to lower serum cholesterol to clinically relevant levels and evaluated the final adaptive immune response. T-lymphocytes-specific mTORC2 knockout mice were used to evaluate mTOR signaling and antitumor immunity. Pretreatment and posttreatment prostate tumors and lymphocytes were examined from a window-of-opportunity clinical trial where men with prostate cancer were treated with 2 to 6 weeks of aggressive cholesterol-lowering intervention prior to radical prostatectomy.

RESULTS

Mice treated with oral ezetimibe exhibited enhanced antitumor immunity against syngeneic cancers in a CD8+ lymphocyte-dependent manner, produced immunity that was transferrable through lymphocytes, and had enhanced central CD8+ T-cell memory. In mice and in patients undergoing prostatectomy, lowering serum cholesterol inhibited mTORC2 signaling in lymphocytes and increased infiltration of CD8+ lymphocytes into prostate tumors. T-lymphocyte-specific mTORC2 knockout mice demonstrated enhanced CD8+ lymphocyte function and antitumor capacity. In patients, cholesterol-lowering intervention prior to prostatectomy decreased the proliferation of normal prostate and low-grade adenocarcinomas.

CONCLUSIONS

Lowering serum cholesterol decreased signaling through mTORC2 and enhanced antitumor CD8+ T-cell memory. We provide a rationale for large-scale clinical testing of cholesterol lowering strategies for prostate cancer chemoprevention.

Compartmentalized T cell profile in the lungs of patients with HIV-1-associated pulmonary Kaposi sarcoma

Pulmonary Kaposi sarcoma (pKS) caused by Human herpesvirus 8 (HHV-8) is a devastating form of KS in patients with advanced acquired immunodeficiency syndrome (AIDS) and is associated with increased morbidity and mortality. Blood T cells play a central role in the response of HIV-1 and HHV-8. However, little information is available on T cells in the alveolar space of HIV-1-associated pKS patients.Therefore, we examined CD8+ and CD4+ T cells in the alveolar space in comparison with the blood of patients with pKS. We recruited 26 HIV-1 positive patients with KS, including 15 patients with pKS. Bronchoalveolar lavage (BAL) cells and blood mononuclear cells were analyzed for T cell memory phenotypes, surface markers associated with exhaustion, and intracellular cytokine staining (ICS) using flow cytometry. HIV-1 and HHV-8 viral loads were measured in plasma by quantitative PCR.BAL T cells showed reduced inflammatory capacities and significantly diminished polyfunctionality compared to blood T cells from patients with pKS. This was not accompanied by increased expression of exhaustion markers, such as TIM-3 and PD-1.More importantly, we found a negative correlation between the production of MIP1-β and TNF-α in T cells in BAL and blood, indicating compartmentalised immune responses to pKS and accentuated chronic HIV-1/HHV-8 pathogenesis via T cells in the lungs of people with pKS.

The roles of T cells in obese adipose tissue inflammation

Adipose tissue inflammation in obese patients can cause a series of metabolic diseases. There are a variety of immune cells in adipose tissue, and studies have shown that T cells are associated with adipose tissue inflammation. This review aims to describe the current understanding of the relationship between T cells and adipose tissue inflammation, with a focus on regulation by T cell subtypes. Studies have shown that Th1, Th17 and CD8+ T cells, which are important T cell subsets, can promote the development of adipose tissue inflammation, whereas Treg cells protect against inflammation, suggesting that targeting the mechanism by which T cell subtypes regulate adipose tissue inflammation is a potential therapeutic strategy for treating obesity. T cells play important roles in regulating obesity-associated adipose tissue inflammation, thus providing new research directions for the treatment of obesity. More studies are needed to clarify how T cell subtypes regulate adipose tissue inflammation to identify new treatments for obesity.

Immune-associated molecular occurrence and prognosis predictor of hepatocellular carcinoma: an integrated analysis of GEO datasets

Hepatocellular carcinoma (HCC) is the fifth most common cancer and the second most common cause of cancer-related deaths worldwide. As immune response failure is the main factor in the occurrence and poor prognosis of HCC, our study aimed to develop an immune-associated molecular occurrence and prognosis predictor (IMOPP) of HCC. To that end, we discovered a 4-gene immune-associated gene signature: C-C motif chemokine ligand 14 (CCL14), kallikrein B1 (KLKB1), vasoactive intestinal peptide receptor 1 (VIPR1), and cluster of differentiation 4 (CD4). When tested on three cohorts as an immune-associated molecular occurrence predictor (IMOP), it had high sensitivity, specificity, and area under the receiver operating characteristics curve. When tested as an immune-associated molecular prognosis predictor (IMPP), it stratified the HCC prognosis for overall survival (Kaplan-Meier analysis, log rank P = 0.0016; Cox regression, HR = 1.832, 95% CI = 1.173-2.859, P = 0.008) and disease-free survival (Kaplan-Meier analysis, log rank P = 0.0227). IMPP also significantly correlated with the clinicopathological characteristics of HCC; integrating it with clinicopathological characteristics improved the accuracy of a nomogram for overall survival prediction (C-index: 0.7097 vs. 0.6631). In HCC tumor microenviroments, the proportion of CD8⁺ T cells significantly differed between IMOP-stratified groups. We conclude that IMOPP can potentially predict the occurrence of HCC in high-risk populations and improve prognostic accuracy by providing new biomarkers for risk stratification. In addition, we believe that the IMOP mechanism may be related to its effect on the proportion of CD8⁺ T cells in tumor-infiltrating lymphocytes.

Circulating tumor cells counts are associated with CD8+ T cell levels in programmed death-ligand 1-negative non-small cell lung cancer patients after radiotherapy: A retrospective study

This study aimed to explore the dynamics of circulating tumor cells (CTCs) and CD8+ T cells in stage II-III non-small cell lung cancer patients with CTCs in different programmed death-ligand 1 (PD-L1) status treated with radiotherapy and evaluate the correlation between CTCs and CD8+ T cells.This study was a retrospective study which reviewed 69 stage II-III non-small cell lung cancer patients underwent postoperative radiotherapy and peripheral blood tests of CTCs and T lymphocyte were available before radiation, 1 week after radiation and 1 month after radiation.In this study, 25 patients had PD-L1 positive CTCs and 44 patients had PD-L1 negative CTCs. The CTCs count was significantly decreased compared with baseline in patients with different PD-L1 status CTCs at 1 week and 1 month after radiotherapy. The proportion of CD8+ T cells was significantly increased at 1 month after radiotherapy compared with baseline in the total population (mean change, 7.24 ± 2.12; P < .05) and patients with PD-L1 negative CTCs (mean change, 7.17 ± 2.65; P < .05). One month after radiotherapy, the proportion of CD8+ T cells was negatively correlated with the CTCs count in the total population (r = -0.255, P = .034) and PD-L1 negative patients (r = -0.330, P = .029). In patients with PD-L1 negative CTCs, the CTCs count 1 week after radiotherapy (hazard ratio, 0.150 [95% confidence intervals., 0.027-0.840], P = .031) and the proportion of CD8+ T cells 1 month after radiotherapy (hazard ratio, 7.961 [95% confidence intervals, 1.028-61.68], P = .047) were independent prognostic factors for disease recurrence.After radiotherapy, only PD-L1-negative patients had a significant increase in the CD8+ T cell levels, while it was negatively correlated with CTCs count and was an independent prognostic factors of disease recurrence.

T cell dysfunction in chronic hepatitis B infection and liver cancer: evidence from transcriptome analysis

BACKGROUND

T cell dysfunction occurs in many diseases, especially in chronic virus infection and cancers. However, up to now, little is known on the distinctions in T cell exhaustion between cancer and chronic virus infection. The objective of this study is to explore the transcriptional similarities and differences in exhausted CD8 +T cell between chronic hepatitis B virus (HBV) infection and hepatocellular carcinoma (HCC).

METHODS

RNA sequencing was performed to compare the transcriptome of CD8 +T cells isolated from healthy donors' blood, tumour tissues of patients with HCC and chronic HBV infected HCC patients' paracancerous tissues. DESeq2 algorithm was used to determine differentially expressed genes. Gene ontology and Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway enrichment analysis was conducted for in-depth analysis of these differentially expressed genes.

RESULTS

A total number of 2109 and 2203 genes were differentially expressed in patients with chronic HBV infection and HCC, respectively. Comparing these two groups of differentially deregulated genes, we found that nearly half of them were shared, and these shared genes were further classified into several functional categories, such as metabolic process, binding and intracellular organelle. KEGG analysis revealed that these shared deregulated genes were involved in many important pathways such as Parkinson's disease, oxidative phosphorylation and messenger RNA surveillance. Interestingly, we reported that chronic HBV infection specific deregulated genes were mainly enriched in graft versus host disease, allograft rejection, phenylalanine, tyrosine and tryptophan biosynthesis pathways. Whereas, HCC-specific deregulated genes were highly enriched in oxidative phosphorylation, thyroid cancer and endometrial cancer pathways.

CONCLUSION

Our study demonstrated that T cell dysfunction associated with HCC and chronic HBV infection shares high similarities, however, each possesses its own features in terms of specific genes and signalling pathways. Uncovering the differences of T cells dysfunction would facilitate our understanding the diseases pathogenesis and developing innovative therapies in the future.

Evaluation of T cell infiltration in matched biopsy and nephrectomy samples in renal cell carcinoma

T cell infiltration in tumors has been investigated as a biomarker of response to checkpoint inhibitors. Neo-adjuvant studies in renal cell carcinoma (RCC) may provide a unique opportunity to compare T cell infiltration in a pretreatment renal mass biopsy to a posttreatment nephrectomy specimen, and thus evaluate the effects of immune checkpoint inhibitors. However, there are no data regarding the association of T cell infiltration in matched biopsy and nephrectomy samples without intervening treatment. Understanding this association will inform investigation of this potential biomarker in future studies.Matched biopsy and nephrectomy samples (without intervening systemic therapy) were identified from patients with nonmetastatic RCC. Selected tissue sections from biopsy and nephrectomy samples were reviewed and marked for intratumoral lymphocytes by a pathologist. Immunohistochemistry (IHC) was utilized to stain for T cell markers (CD3, CD4, and CD8). Intratumoral staining was then quantified in the tissue sections as counts per total tumor area surveyed. Spearman correlation (r) was used to measure associations.Thirty matched pairs were investigated. The median interval between biopsy and nephrectomy was 2.8 (0.2-87.7) months. Clear cell was the most common histology (29/30; 97%). There was a statistically significant positive correlation between the frequency of CD3 and CD8 T cells between matched biopsy and nephrectomy samples (r = 0.39; P = .036 and r = 0.38; P = .041, respectively).The frequencies of CD8+ T cells in matched biopsy and nephrectomy samples in RCC in the absence of intervening treatment have been characterized and show a positive correlation between matched biopsy and nephrectomy samples.

CD4+ Foxp3+ T cells promote aberrant immunoglobulin G production and maintain CD8+ T-cell suppression during chronic liver disease

Persistent hepatotropic viral infections are a common etiologic agent of chronic liver disease. Unresolved infection can be attributed to nonfunctional intrahepatic CD8+ T-cell responses. In light of dampened CD8+ T-cell responses, liver disease often manifests systemically as immunoglobulin (Ig)-related syndromes due to aberrant B-cell functions. These two opposing yet coexisting phenomena implicate the potential of altered CD4+ T-cell help. Elevated CD4+ forkhead box P3-positive (Foxp3+) T cells were evident in both human liver disease and a mouse model of chemically induced liver injury despite marked activation and spontaneous IgG production by intrahepatic B cells. While this population suppressed CD8+ T-cell responses, aberrant B-cell activities were maintained due to expression of CD40 ligand on a subset of CD4+ Foxp3+ T cells. In vivo blockade of CD40 ligand attenuated B-cell abnormalities in a mouse model of liver injury. A phenotypically similar population of CD4+ Foxp3+, CD40 ligand-positive T cells was found in diseased livers explanted from patients with chronic hepatitis C infection. This population was absent in nondiseased liver tissues and peripheral blood.

CONCLUSION

Liver disease elicits alterations in the intrahepatic CD4+ T-cell compartment that suppress T-cell immunity while concomitantly promoting aberrant IgG mediated manifestations. (Hepatology 2017;65:661-677).

Tumor-Infiltrating Merkel Cell Polyomavirus-Specific T Cells Are Diverse and Associated with Improved Patient Survival

Tumor-infiltrating CD8+ T cells are associated with improved survival of patients with Merkel cell carcinoma (MCC), an aggressive skin cancer causally linked to Merkel cell polyomavirus (MCPyV). However, CD8+ T-cell infiltration is robust in only 4% to 18% of MCC tumors. We characterized the T-cell receptor (TCR) repertoire restricted to one prominent epitope of MCPyV (KLLEIAPNC, "KLL") and assessed whether TCR diversity, tumor infiltration, or T-cell avidity correlated with clinical outcome. HLA-A*02:01/KLL tetramer+ CD8+ T cells from MCC patient peripheral blood mononuclear cells (PBMC) and tumor-infiltrating lymphocytes (TIL) were isolated via flow cytometry. TCRβ (TRB) sequencing was performed on tetramer+ cells from PBMCs or TILs (n = 14) and matched tumors (n = 12). Functional avidity of T-cell clones was determined by IFNγ production. We identified KLL tetramer+ T cells in 14% of PBMC and 21% of TIL from MCC patients. TRB repertoires were strikingly diverse (397 unique TRBs were identified from 12 patients) and mostly private (only one TCRb clonotype shared between two patients). An increased fraction of KLL-specific TIL (>1.9%) was associated with significantly increased MCC-specific survival P = 0.0009). T-cell cloning from four patients identified 42 distinct KLL-specific TCRa/b pairs. T-cell clones from patients with improved MCC-specific outcomes were more avid (P < 0.05) and recognized an HLA-appropriate MCC cell line. T cells specific for a single MCPyV epitope display marked TCR diversity within and between patients. Intratumoral infiltration by MCPyV-specific T cells was associated with significantly improved MCC-specific survival, suggesting that augmenting the number or avidity of virus-specific T cells may have therapeutic benefit. Cancer Immunol Res; 5(2); 137-47. ©2017 AACR.

Role of CD8(+) T cells in protection against Leishmania donovani infection in healed Visceral Leishmaniasis individuals

BACKGROUND

Majority of individuals with history of visceral leishmaniasis (VL) exhibit strong immunity to re-infection, however, the mechanism of resistance is poorly understood. It is unclear whether CD8(+) T cells contribute to protection against Leishmania donovani infection through cytotoxic activity. The present study aims to evaluate immunological mechanism associated with resistance to the disease in healed VL (HVL) individuals and further, the contribution of CD8(+) T cells in the protective immunity.

METHODS

Peripheral blood mononuclear cells (PBMCs) from VL, HVL and naive groups were exposed in vitro to total soluble Leishmania antigen (TSLA) from L. donovani. The proliferation index was determined by ELISA based lymphoproliferative assay. Cytokines and granzyme B levels were measured by CBA. Activated T-cell populations were estimated using flow cytometry.

RESULTS

We observed significantly higher lymphoproliferation, cytokines and granzyme B levels in HVL group compared to naive or VL group. More strikingly, we found a strong association (rs = 0.895, P < 0.0001) between proliferation index (PI) and granzyme B level, with a significant proportion of activated CD8(+) T cells in HVL group.

CONCLUSIONS

Leishmania immune group (HVL) exhibited durable and strong cellular immune response to TSLA in terms of lymphoproliferation as well as production of Th1 cytokines and granzyme B. Additionally, the elevated level of activated CD8(+) T cells and stimulation of cytotoxic activity through granzyme B production, indicated a possible role of CD8(+) T cells in resistance to L. donovani infection in the HVL group.

Characterization of T-cell responses to cryptic epitopes in recipients of a noncodon-optimized HIV-1 vaccine

INTRODUCTION

Cryptic epitopes (CEs) can be encoded by any of the 5 alternative reading frames (ARFs, 2 sense and 3 antisense) of a known gene. Although CE responses are commonly detected during HIV-1 infection, it is not known whether these responses are induced after vaccination.

METHODS

Using a bioinformatic approach, we determined that vaccines with codon-optimized HIV inserts significantly skewed CE sequences and are not likely to induce crossreactive responses to natural HIV CE. We then evaluated the CE- and protein-specific T-cell responses using Gag, Pol, and ARF peptide pools among participants immunized with a non-codon optimized vaccine regimen of 2 pGA2/JS7 DNA primes followed by 2 MVA/HIV62 Gag-Pol-Env vector boosts or 4 saline injections.

RESULTS

Vaccinees had significantly more interferon gamma enzyme-linked immunosorbent spot (IFNγ ELISpot) responses toward Gag (P = 0.003) but not toward Pol protein than did placebo recipients. However, CE-specific T-cell responses were low in magnitude, and their frequencies did not differ significantly between vaccine and placebo recipients. Additionally, most positive CE responses could not be mapped to individual peptides. After expanding responses in a cultured assay, however, the frequency and the median magnitude of responses to ARF peptides were significantly greater in vaccinees (P < 0.0001), indicating that CE-specific T-cell responses are present but below an ex vivo assay's limit of detection.

CONCLUSIONS

Our data demonstrate that HIV-1 vaccines currently in clinical trials are poorly immunogenic with regard to CE-specific T-cell responses. Therefore, the context of HIV-1 immunogens may need to be modified as a comprehensive strategy to broaden vaccine-induced T-cell responses.

Successful vaccination induces multifunctional memory T-cell precursors associated with early control of hepatitis C virus

BACKGROUND & AIMS

T cells are an important component for development of a vaccine against hepatitis C virus (HCV), but little is known about the features of successful vaccine-induced T cells.

METHODS

We compared the phenotype, function, and kinetics of vaccine-induced and infection-induced T cells in chimpanzees with HCV infection using multicolor flow cytometry and real-time polymerase chain reaction.

RESULTS

In chimpanzees successfully vaccinated with recombinant adenovirus and DNA against HCV NS3-5, HCV-specific T cells appeared earlier, maintained better functionality, and persisted at higher frequencies for a longer time after HCV challenge, than those of mock-vaccinated chimpanzees. Vaccine-induced T cells displayed higher levels of CD127, a marker of memory precursors, and lower levels of programmed death-1 (PD-1) than infection-induced T cells. Vaccine-induced, but not infection-induced, T cells were multifunctional; their ability to secrete interferon gamma and tumor necrosis factor α correlated with early expression of CD127 but not PD-1. Based on a comparison of vaccine-induced and infection-induced T cells from the same chimpanzee, the CD127(+) memory precursor phenotype was induced by the vaccine itself rather than by low viremia. In contrast, induction of PD-1 correlated with viremia, and levels of intrahepatic PD-1, PD-L1, and 2,5-OAS-1 messenger RNAs correlated with peak titers of HCV.

CONCLUSIONS

Compared with infection, vaccination-induced HCV-specific CD127(+) T cells with high functionality that persisted at higher levels for a longer time. Control of viremia prevented up-regulation of PD-1 on T cells and induction of PD-1, PD-L1, and 2,5-OAS-1 in the liver. Early development of a memory T-cell phenotype and, via control of viremia, attenuation of the inhibitory PD1-PD-L1 pathway might be necessary components of successful vaccine-induced protection against HCV.

Activation-induced cell death of memory CD8+ T cells from pleural effusion of lung cancer patients is mediated by the type II Fas-induced apoptotic pathway

Lung cancer is the second most common form of cancer and the leading cause of cancer death worldwide. Pleural effusions, containing high numbers of mononuclear and tumor cells, are frequent in patients with advanced stages of lung cancer. We reported that in pleural effusions from primary lung cancer, the CD8+ T cell subpopulation, and particularly the terminally differentiated subset, is reduced compared to that of non-malignant effusions. We analyzed the participation of activation-induced cell death (AICD) and extrinsic pathways (type I or II) as mechanisms for the decrease in pleural effusion CD8+ T cell subpopulation. Pleural effusion or peripheral blood CD4+ and CD8+ T cells, from lung cancer patients, were stimulated with anti-CD3 antibody and analyzed for (a) apoptosis by annexin-V-binding and TUNEL assay, (b) transcript levels of Fas ligand (FasL) and TRAIL by real-time RT-PCR, (c) expression of FasL and TRAIL, measured as integrated mean fluorescence intensities (iMFI) by flow cytometry, (d) expression of Bcl-2 and BIM molecules, measured as MFI, and (e) apoptosis inhibition using caspase-8 and -9 inhibitors. Pleural effusion CD8+ T cells, but not CD4+ T cells, from cancer patients underwent AICD. Blocking FasL/Fas pathway protected from AICD. Upregulation of FasL and TRAIL expressions was found in pleural effusion CD8+ T cells, which also showed a subset of Bcl-2 low cells. In memory CD8+ T cells, AICD depended on both extrinsic and intrinsic apoptotic pathways. Hence, in the pleural space of lung cancer patients, AICD might compromise the antitumor function of CD8+ T cells.

Immunological responses in cancer patients after vaccination with the therapeutic telomerase-specific vaccine Vx-001

Vx-001, an HLA-A*0201 restricted telomerase (TERT)-specific anti-tumor vaccine, is composed of the 9-mer cryptic TERT(572) peptide and its optimized variant TERT(572Y). We have previously shown that Vx-001 is non-toxic, highly immunogenic and in vaccinated NSCLC patients early specific immune response is associated with prolonged survival. The aim of the present study was to investigate the specific T-cell immune response against Vx-001. Fifty-five patients with chemo-resistant advanced solid tumors were vaccinated with TERT(572Y) (2 subcutaneous injections) followed by TERT(572) peptide (4 subcutaneous injections) every 3 weeks. Specific immune response was evaluated by IFN-γ and perforin ELISpot and intracellular cytokine staining assays. TERT-reactive T cells were detected in 27 (51%) out of 53 evaluable patients after the 2nd vaccination and in 22 (69%) out of 32 evaluable patients after the completion of 6 vaccinations. Immune responses developed irrespective of the stage of disease and disease status before vaccination. Patients with disease progression at study entry who developed a post-vaccination-induced immunological response had a significant overall survival benefit compared to the post-vaccination non-responders. The Vx-001 vaccine is a promising candidate for cancer immunotherapy since it can induce a TERT-specific T-cell immune response that is associated with prolonged survival.

Cross-presentation of antigen by diverse subsets of murine liver cells

Antigen cross-presentation is a principal function of specialized antigen-presenting cells of bone marrow origin such as dendritic cells. Although these cells are sometimes known as "professional" antigen-presenting cells, nonbone marrow-derived cells may also act as antigen-presenting cells. Here, using four-way liver cell isolation and parallel comparison of candidate antigen-presenting cells, we show that, depending on the abundance of antigen-donor cells, different subsets of liver cells could cross-present a hepatocyte-associated antigen. This function was observed in both liver sinusoidal endothelial cells and Kupffer cells even at very low antigen concentration, as well as when using soluble protein. Antigen cross-presentation by liver cells induced efficient CD8+ T-cell proliferation in a similar manner to classical dendritic cells from spleen. However, proliferated cells expressed a lower level of T-cell activation markers and intracellular interferon-gamma levels. In contrast to classical spleen dendritic cells, cross-presentation by liver antigen-presenting cells was predominantly dependent on intercellular adhesion molecule-1.

CONCLUSION

Hepatic sinusoids are an environment rich in antigen cross-presenting activity. However, the liver's resident antigen-presenting cells cause partial T-cell activation. These results clarify how the liver can act as a primary site of CD8+ T-cell activation, and why immunity against hepatocyte pathogens is sometimes ineffective.

CD8+ T cells induce thyroid epithelial cell hyperplasia and fibrosis

CD8(+) T cells can be important effector cells in autoimmune inflammation, generally because they can damage target cells by cytotoxicity. This study shows that activated CD8(+) T cells induce thyroid epithelial cell hyperplasia and proliferation and fibrosis in IFN-γ(-/-) NOD.H-2h4 SCID mice in the absence of CD4(+) T cells. Because CD8(+) T cells induce proliferation rather than cytotoxicity of target cells, these results describe a novel function for CD8(+) T cells in autoimmune disease. In contrast to the ability of purified CD8(+) T cells to induce thyrocyte proliferation, CD4(+) T cells or CD8 T cell-depleted splenocytes induced only mild thyroid lesions in SCID recipients. T cells in both spleens and thyroids highly produce TNF-α. TNF-α promotes proliferation of thyrocytes in vitro, and anti-TNF-α inhibits development of thyroid epithelial cell hyperplasia and proliferation in SCID recipients of IFN-γ(-/-) splenocytes. This suggests that targeting CD8(+) T cells and/or TNF-α may be effective for treating epithelial cell hyperplasia and fibrosis.

Viral pathophysiology of multiple sclerosis: A role for Epstein-Barr virus infection?

Multiple sclerosis (MS) is the most common inflammatory demyelinating and degenerative disease of the CNS. The cause of MS is unknown but environmental risk factors are implicated in MS. Several viruses have been proposed as a trigger for MS, and lately Epstein-Barr virus (EBV) has become the leading candidate. An infectious aetiology fits with a number of epidemiological observations in addition to the immunopathological features of the disease. In this review we will summarize the emerging evidence, which demonstrates a strong association between EBV infection and MS. The conundrum remains as to whether EBV is directly involved in the pathophysiology of MS, or alternatively if the immunopathology of MS somehow affects the regulation of EBV infection.

Alcohol and hepatitis C virus--interactions in immune dysfunctions and liver damage

Hepatitis C virus infection affects 170 million people worldwide, and the majority of individuals exposed to HCV develop chronic hepatitis leading to progressive liver damage, cirrhosis, and hepatocellular cancer. The natural history of HCV infection is influenced by genetic and environmental factors of which chronic alcohol use is an independent risk factor for cirrhosis in HCV-infected individuals. Both the hepatitis C virus and alcohol damage the liver and result in immune alterations contributing to both decreased viral clearance and liver injury. This review will capture the major components of the interactions between alcohol and HCV infection to provide better understanding for the molecular basis of the dangerous combination of alcohol use and HCV infection. Common targets of HCV and alcohol involve innate immune recognition and dendritic cells, the critical cell type in antigen presentation and antiviral immunity. In addition, both alcohol and HCV affect intracellular processes critical for hepatocyte and immune cell functions including mitochondrial and proteasomal activation. Finally, both chronic alcohol use and hepatitis C virus infection increase the risk of hepatocellular cancer. The common molecular mechanisms underlying the pathological interactions between alcohol and HCV include the modulation of cytokine production, lipopolysaccharide (LPS)-TLR4 signaling, and reactive oxygen species (ROS) production. LPS-induced chronic inflammation is not only a major cause of progressive liver injury and fibrosis, but it can also contribute to modification of the tissue environment and stem cells to promote hepatocellular cancer development. Alteration of these processes by alcohol and HCV produces an environment of impaired antiviral immune response, greater hepatocellular injury, and activation of cell proliferation and dedifferentiation.

Neuroimmune interactions in a model of multiple sclerosis

Psychological stress has been implicated in both the onset and exacerbation of multiple sclerosis (MS). Our research has focused on the role of stress at the onset of MS, using the mouse model Theiler's murine encephalomyelitis virus-induced demyelination. Theiler's virus is a natural pathogen of mice that causes a persistent infection of the central nervous system (CNS) and inflammatory immune-mediated demyelination that is very similar to MS. Our research has shown that restraint stress sufficiently increases corticosterone secretion to cause immunosuppression. Stressed mice develop decreased innate and adaptive immune responses, including decreased chemokine and cytokine responses, to virus, which leads to increased viral replication within the CNS. Higher levels of virus then cause increased later demyelinating disease. These findings may have important implications in our understanding of the interactions between stress and the development of autoimmune diseases induced by infectious agents.

High-programmed death-1 levels on hepatitis C virus-specific T cells during acute infection are associated with viral persistence and require preservation of cognate antigen during chronic infection

Hepatitis C virus (HCV) is an important human pathogen that represents a model for chronic infection given that the majority of infected individuals fail to clear the infection despite generation of virus-specific T cell responses during the period of acute infection. Although viral sequence evolution at targeted MHC class I-restricted epitopes represents one mechanism for immune escape in HCV, many targeted epitopes remain intact under circumstances of viral persistence. To explore alternative mechanisms of HCV immune evasion, we analyzed patterns of expression of a major inhibitory receptor on T cells, programmed death-1 (PD-1), from the time of initial infection and correlated these with HCV RNA levels, outcome of infection, and sequence escape within the targeted epitope. We show that the level of PD-1 expression in early HCV infection is significantly higher on HCV-specific T cells from subjects who progress to chronic HCV infection than from those who clear infection. This correlation is independent of HCV RNA levels, compatible with the notion that high PD-1 expression on HCV-specific CD8 T cells during acute infection inhibits viral clearance. Viral escape during persistent infection is associated with reduction in PD-1 levels on the surface of HCV-specific T cells, supporting the necessity of ongoing antigenic stimulation of T cells for maintenance of PD-1 expression. These results support the idea that PD-1 expression on T cells specific for nonescaped epitopes contributes to viral persistence and suggest that PD-1 blockade may alter the outcome of HCV infection.

A HLA-Cw*0701 restricted Melan-A/MART1 epitope presented by melanoma tumor cells to CD8+ tumor infiltrating lymphocytes

Melan-A/MART1 is a melanocytic differentiation antigen recognized on melanoma tumor cells by CD8+ and CD4+ T cells. In this study, we describe a new epitope of this protein recognized in the context of HLA-Cw*0701 molecules by a CD8+ tumor infiltrating lymphocyte (TIL) clone. This CD8+ TIL clone specifically recognized and killed a fraction of melanoma cells lines expressing Melan-A/MART1 and HLA-Cw*0701. We further show that the Melan-A/MART1(51-61) peptide is the optimal peptide recognized by this clone. Together, these data significantly enlarge the fraction of melanoma patients susceptible to benefit from a Melan-A/MART1 vaccine approach.

Cellular immune responses against persistent hepatitis C virus: gone but not forgotten

Failure to sustain antiviral T cell responses is a hallmark of persistent hepatitis C virus infection. Early loss of T cell proliferative capacity after acute disease appears to be an important component of this process. T cell function may, however, be restored in vitro with interleukin 2

Early impairment of hepatitis C virus specific T cell proliferation during acute infection leads to failure of viral clearance

BACKGROUND AND AIMS

Cellular mediated immunity (CMI) is thought to play a key role in resolution of primary hepatitis C virus (HCV) infection. However, CD4+ and CD8+ T cell responses are also generated during acute infection in individuals who become chronic, suggesting that they developed a defective CMI. The aim of this study was to verify if and when such immune dysfunction is established by measuring the breadth, magnitude, function, and duration of CMI in a large cohort of subjects during the natural course of acute HCV infection.

METHODS

CMI was comprehensively studied by prospective sampling of 31 HCV acutely infected subjects enrolled at the onset of infection and followed for a median period of one year.

RESULTS

Our results indicated that while at the onset of acute HCV infection a measurable CMI with effector function was detected in the majority of subjects, after approximately six months less than 10% of chronically infected individuals displayed significant CMI compared with 70% of subjects who cleared the virus. We showed that progressive disappearance of HCV specific T cells from the peripheral blood of chronic patients was due to an impaired ability to proliferate that could be rescued in vitro by concomitant exposure to interleukin 2 and the antigen.

CONCLUSION

Our data provide evidence of strong and multispecific T cell responses with a sustained ability to proliferate in response to antigen stimulation as reliable pharmacodynamic measures of a protective CMI during acute infection, and suggest that early impairment of proliferation may contribute to loss of T cell response and chronic HCV persistence.

Surface expression and cytolytic function of natural killer cell receptors is altered in chronic hepatitis C

INTRODUCTION

Impaired activity of natural killer (NK) cells has been proposed as a mechanism contributing to viral persistence in hepatitis C virus (HCV) infection. As the function of NK cells is primarily regulated by NK cell receptors (NKR), we analysed whether decreased NK cell function in hepatitis C may be related to dysregulated NKR expression.

PATIENTS AND METHODS

Expression of NK cell was analysed by flow cytometry on lymphocytes from HCV(+) subjects (n = 30), patients who became HCV(-) after antiviral therapy (n = 10), healthy individuals (n = 10), and hepatitis B virus (HBV) infected patients (n = 9). Cytolytic function of lymphocytes was studied in a redirected lysis assay and in a standard 51chromium release cytotoxicity assay, respectively.

RESULTS

In patients with chronic hepatitis C, we found a significantly reduced proportion of NKp46 and NKp30 expressing NK cells compared with healthy and HBV infected subjects. Low expression of natural cytotoxicity receptor (NCR) was also confirmed in in vitro activated NK cell populations derived from HCV patients compared with uninfected donors. In contrast, patients who cleared HCV under antiviral therapy showed normal expression of NKp44, NKp30, and NKp46. Reduced NCR expression in chronic hepatitis C was associated with a parallel decrease in NCR mediated target cell killing. Furthermore, we found a significantly increased proportion of NKG2A expressing NK cells and CD8+ T cells in HCV positive patients, resulting in a reduced cytolytic activity against cells incubated with the HLA-E stabilising peptide HCV core35-44.

CONCLUSION

The present study indicates that defective expression of NKR represents a novel mechanism contributing to impaired function of NK cells and CD8+ T cells in chronic hepatitis C.

Assumptions of the tumor 'escape' hypothesis

The reasons why cancer cells are not destroyed by the immune system are likely to be similar, in most cases, to the reasons why normal cells are not destroyed by the immune system. Unfortunately for tumor immunologists, these reasons have not yet been fully elucidated. What is known, however, is that the lack of autoimmune destruction of normal tissue after immune activation is a finely regulated, highly orchestrated sequence of events. Viewed in this light, it is interesting to conceptualize the derangement of the tumor genome not merely as an engine that enables cancer cells to dodge immune recognition. The dysregulation characteristic of the transformed genome is also what makes tumor immunity, a specialized form of autoimmunity, possible.