Low programmed cell death‐1 (PD‐1) expression in peripheral CD4+ T cells in Japanese patients with autoimmune type 1 diabetes

Programmed cell death‐1 (PD‐1) is a co‐stimulatory molecule that inhibits T cell proliferation. We aimed to clarify PD‐1 expression in CD4⁺ T cells and the association between PD‐1 expression and the 7785C/T polymorphism of PDCD1, with a focus on the two subtypes of type 1 diabetes, type 1A diabetes (T1AD) and fulminant type 1 diabetes (FT1D), in the Japanese population. We examined 22 patients with T1AD, 15 with FT1D, 19 with type 2 diabetes (T2D) and 29 healthy control (HC) subjects. Fluorescence‐activated cell sorting (FACS) and real‐time PCR were utilized to analyse PD‐1 expression quantitatively. Genotyping of 7785C/T in PDCD1 was performed using the TaqMan method in a total of 63 subjects (21 with T1AD, 15 with FT1D and 27 HC). FACS revealed a significant reduction in PD‐1 expression in CD4⁺ T cells in patients with T1AD (mean: 4·2 vs. 6·0% in FT1D, P = 0·0450; vs. 5·8% in T2D, P = 0·0098; vs. 6·0% in HC, P = 0·0018). PD‐1 mRNA expression in CD4⁺ T cells was also significantly lower in patients with T1AD than in the HC subjects. Of the 63 subjects, PD‐1 expression was significantly lower in individuals with the 7785C/C genotype than in those with the C/T and T/T genotypes (mean: 4·1 vs. 5·9%, P = 0·0016). Our results indicate that lower PD‐1 expression in CD4⁺ T‐cells might contribute to the development of T1AD through T cell activation.     

Phenotypic characterization of regulatory T cells from antiretroviral‐naive HIV‐1‐infected people

Regulatory T (Treg) cells play a key role in dampening excessive immune activation. However, antiretroviral therapy (ART) ‐naive HIV‐1 infection maintains the immune system in a sustained state of activation that could alter both Treg cell surface markers and functions. As Treg cell surface markers are directly linked to their functions the overall objective of this study was to determine how ART‐naive HIV infection affects the phenotypic properties of Treg cells. Our data showed that in ART‐naive HIV‐1 infection, Treg cells are dominated by effector (CD45RA⁺ CD27⁻ CCR7⁻ CD62L⁻) and effector memory (CD45RA⁻ CD27⁻ CCR7⁻ CD62L⁻) cells. In contrast Treg cells from HIV‐negative individuals were mainly naive (CD45RA⁺ CD27⁺ CCR7⁺ CD62L⁺) and central memory (CD45RA⁻ CD27⁺ CCR7⁺ CD62L⁺) cells. Whereas effector and effector memory Treg cells showed enhanced expression of CD39 (P < 0·05), CD73 (P < 0·001), HLA‐DR and CD38 (P < 0·001); naive and central memory Treg cells showed a significant reduction in the expression of these markers. Overall Treg cell frequencies within total CD4⁺ T cells correlated positively with plasmatic HIV‐1 viral load. As increased viral load is associated with augmented CD4⁺ T‐cell destruction; this could suggest a resistance of peripheral Treg cells to HIV‐1 destruction. Hence the modulation of Treg cell phenotype and frequencies could be considered in designing immunotherapeutic strategies targeting immune system restoration during HIV‐1 infection.     

Association between discordant immunological response to highly active anti‐retroviral therapy,regulatory T cell percentage,immune cell activation and very low‐level viraemia in HIV‐infected patients

The mechanisms sustaining the absence of complete immune recovery in HIV‐infected patients upon long‐term effective highly active anti‐retroviral therapy (HAART) remain elusive. Immune activation, regulatory T cells (T_regs) or very low‐level viraemia (VLLV) have been alternatively suspected, but rarely investigated simultaneously. We performed a cross‐sectional study in HIV‐infected aviraemic subjects (mean duration of HAART: 12 years) to concomitantly assess parameters associated independently with inadequate immunological response. Patients were classified as complete immunological responders (cIR, n = 48) and inadequate immunological responders (iIR, n = 39), depending on the CD4⁺ T cell count (> or < 500/mm³). Clinical and virological data (including very low‐level viraemia) were collected. In parallel, immunophenotyping of CD4⁺ lymphocytes, including T_reg subsets, and CD8⁺ T cells was performed. Percentages of activated CD4⁺ T cells, T_regs, effector T_regs and terminal effector T_regs were found to be significantly elevated in iIR. Neither the percentage of activated CD8⁺ T cells nor VLLV were found to be associated with iIR. In the multivariate analysis, nadir of CD4⁺ T cell count and percentage of T_regs were the only two parameters associated independently with iIR [odds ratio (OR) = 2·339, P = 0·001, and OR = 0·803, P = 0·041]. We present here the largest study investigating simultaneously the immune response to long‐term HAART, activation of CD4⁺ and CD8⁺ T cells, T_reg percentages and very low‐level viraemia. Causative interactions between T_regs and CD4⁺ T cells should now be explored prospectively in a large patients cohort.     

Effector memory CD4+ T cells differentially express activation associated molecules depending on the duration of American cutaneous leishmaniasis lesions

A high number of Leishmania‐responder T cells is found in cutaneous leishmaniasis lesions, suggesting that important immunological events occur at the site of infection. Although activated, cytotoxic and regulatory T cells infiltrating into lesions may influence disease pathogenesis, the role of the T cell differentiation pattern of lymphocytes in lesions is unknown. Our aim was to investigate whether the phase of lesion development (early or late) is influenced by the functional status of cells present in inflammatory infiltrate. Activation, cytotoxity and T cell differentiation molecules were evaluated in lesion mononuclear cells by flow cytometry. The frequency of T cells was correlated with the lesion area (r = 0·68; P = 0·020). CD4⁺CD25⁺ T cells predominated over CD4⁺CD69⁺ T cells in early lesions (less than 30 days), whereas late lesions (more than 60 days) exhibited more CD4⁺CD69⁺ T cells than CD4⁺CD25⁺ T cells. The duration of illness was correlated positively with CD4⁺CD69⁺ (r = 0·68; P = 0·005) and negatively with CD4⁺CD25⁺ T cells (r = ?0·45; P = 0·046). Most CD8⁺ T cells expressed cytotoxic‐associated molecules (CD244⁺), and the percentages were correlated with the lesion area (r = 0·52; P = 0·04). Both CD4⁺ and CD8⁺ effector memory T cells (T_EM‐CD45RO⁺CCR7^–) predominated in CL lesions and were significantly higher than central memory (T_CM‐CD45RO⁺CCR7⁺) or naive T cells (CD45RO^–CCR7⁺). An enrichment of T_EM cells and contraction of naive T cells were observed in lesions in comparison to blood (P = 0·006) for both CD4⁺ and CD8⁺ T cells. Lesion chronicity is associated with a shift in activation phenotype. The enrichment of T_EM and activated cytotoxic cells can contribute to immune‐mediated tissue damage.     

Low numbers of CD8+ T lymphocytes in hereditary haemochromatosis are explained by a decrease of the most mature CD8+ effector memory T cells

Low CD8⁺ T lymphocyte numbers have long been described in hereditary haemochromatosis (HH). Recently, two conserved haplotypes localized near the microsatellite D6S105 at the major histocompatibility complex (MHC) class I region were described predicting the clinical expression of HH and the CD8⁺ T lymphocyte numbers. The A‐A‐T haplotype was associated with a severe clinical expression of HH and low CD8⁺ T lymphocyte numbers, while the G‐G‐G haplotype was associated with a milder clinical expression of HH and high CD8⁺ T lymphocyte numbers. As CD8⁺ T lymphocytes are a very heterogeneous population, in this study we analysed the CD8⁺ subpopulations of naive, central memory (T_CM) and effector memory (T_EM), and further subsets of CD8⁺ T_EM cells in 47 HH patients and 68 controls. In addition, association studies were conducted between the conserved haplotypes and the CD8⁺ T cell subpopulations in HH. Variations of the numbers of naive and central memory cells with age were similar between HH patients and controls. For T_EM cells and the T_EM CD27^‐CD28^‐ subset no effect of age was observed in HH [R² = 0·001, not significant (n.s.) and R² = 0·01, n.s., respectively] contrasting with the increasing of these subpopulations with age in controls (R² = 0·09, P = 0·017 and R² = 0·22, P = 0·0005, respectively). Interestingly, patients homozygous for the A‐A‐T haplotype have lower numbers of CD8⁺ T_EM cells due especially to lower numbers of T_EM CD27^‐CD28^‐ (0·206 ± 0·119 and 0·066 ± 0·067 × 10⁶ cells/ml, respectively) than patients carrying the G‐G‐G haplotype (0·358 ± 0·195 and 0·246 ± 0·202 × 10⁶ cells/ml, respectively). This may suggest an inability of HH patients to differentiate the CD8⁺ T cells into the most mature phenotype.     

Increased levels of regulatory T cells (Tregs) in human immunodeficiency virus‐infected patients after 5 years of highly active anti‐retroviral therapy may be due to increased thymic production of naive Tregs

This study determines levels of regulatory T cells (T_regs), naive T_regs, immune activation and cytokine patterns in 15 adult human immunodeficiency virus (HIV)‐infected patients receiving prolonged highly active anti‐retroviral therapy (HAART) who have known thymic output, and explores if naive T_regs may represent recent thymic emigrant T_regs. HIV‐infected patients treated with HAART with a median of 1 and 5 years were compared with healthy controls. Percentages of T_regs (CD3⁺CD4⁺CD25⁺CD127^low), naive T_regs (CD3⁺CD4⁺CD25⁺CD45RA⁺) and activation markers (CD38⁺human leucocyte antigen D‐related) were determined by flow cytometry. Forkhead box P3 mRNA expression and T cell receptor excision circles (T_REC) content in CD4⁺ cells were determined by polymerase chain reaction and cytokines analysed with Luminex technology. Levels of T_regs were significantly higher in HIV‐infected patients compared with controls, both after 1 and 5 years of HAART (P < 0·001), despite fully suppressed HIV‐RNA and normalization of both CD4 counts, immune activation and cytokine patterns. Furthermore, levels of naive T_regs were elevated significantly in HIV‐infected patients (P < 0·001) and were associated with thymic output measured as the T_REC frequency in CD4⁺ cells (P = 0·038). In summary, T_reg levels in HIV‐infected patients are elevated even after 5 years of HAART. Increased thymic production of naive T_regs may contribute to higher T_reg levels in HIV‐infection.     

Selective infection of CD4 effector memory T lymphocytes leads to preferential depletion of memory T lymphocytes in R5 HIV-1-infected humanized NOD/SCID/IL-2Rγ mice

To investigate the events leading to the depletion of CD4⁺ T lymphocytes during long-term infection of human immunodeficiency virus type 1 (HIV-1), we infected human CD34⁺ cells-transplanted NOD/SCID/IL-2Rγ^null mice with CXCR4-tropic and CCR5-tropic HIV-1. CXCR4-tropic HIV-1-infected mice were quickly depleted of CD4⁺ thymocytes and both CD45RA⁺ naïve and CD45RA⁻ memory CD4⁺ T lymphocytes, while CCR5-tropic HIV-1-infected mice were preferentially depleted of CD45RA⁻ memory CD4⁺ T lymphocytes. Staining of HIV-1 p24 antigen revealed that CCR5-tropic HIV-1 preferentially infected effector memory T lymphocytes (T_EM) rather than central memory T lymphocytes. In addition, the majority of p24⁺ cells in CCR5-tropic HIV-1-infected mice were activated and in cycling phase. Taken together, our findings indicate that productive infection mainly takes place in the activated T_EM in cycling phase and further suggest that the predominant infection in T_EM would lead to the depletion of memory CD4⁺ T lymphocytes in CCR5-tropic HIV-1-infected mice.     

Could a loss of memory T cells limit responses to hepatitis C virus (HCV) antigens in blood leucocytes from patients chronically infected with HCV before and during pegylated interferon-α and ribavirin therapy?

The proportions and activation status of T cells may influence responses to hepatitis C virus (HCV) and treatment outcome in patients receiving pegylated interferon (IFN)‐α/ribavirin therapy. We confirmed that IFN‐γ enzyme‐linked immunospot (ELISPOT) responses to HCV are poor in HCV patients and showed that responses to HCV and cytomegalovirus (CMV) antigens decrease during therapy. This was most apparent in patients with sustained virological response (SVR). Baseline frequencies of CD4⁺ effector memory (T_EM) T cells were lower in SVR than non‐SVR. Proportions of CD4⁺ and CD8⁺ T_EM and terminally differentiated effector memory (T_EMRA) T cells declined on therapy in SVR, as did proportions of Fas⁺ CD8⁺ T_EMRA T cells. Baseline frequencies of programmed death (PD)‐1‐expressing CD4⁺ T_EM and T_EMRA T‐cells were higher in SVR. Therapy increased percentages of PD‐1⁺ CD4⁺ central memory (T_CM) T cells and PD‐1⁺ CD8⁺ T_EM and T_EMRA T cells in SVR. We conclude that successful therapy depletes circulating antigen‐specific CD4⁺ T cell responses. This paralleled decreases in proportions of effector memory T cells and higher percentages of CD4⁺ T_CM T cells expressing PD‐1.     

Programmed death‐1+ T cells inhibit effector T cells at the pathological site of miliary tuberculosis

Optimal T cell activation is vital for the successful resolution of microbial infections. Programmed death‐1 (PD‐1) is a key immune check‐point receptor expressed by activated T cells. Aberrant/excessive inhibition mediated by PD‐1 may impair host immunity to Mycobacterium tuberculosis infection, leading to disseminated disease such as miliary tuberculosis (MTB). PD‐1 mediated inhibition of T cells in pulmonary tuberculosis and TB pleurisy is reported. However, their role in MTB, particularly at the pathological site, remains to be addressed. The objective of this study was to investigate the role of PD‐1–PD‐ligand 1 (PD‐L1) in T cell responses at the pathological site from patients of TB pleurisy and MTB as clinical models of contained and disseminated forms of tuberculosis, respectively. We examined the expression and function of PD‐1 and its ligands (PD‐L1–PD‐L2) on host immune cells among tuberculosis patients. Bronchoalveolar lavage‐derived CD3 T cells in MTB expressed PD‐1 (54·2 ± 27·4%, P ≥ 0·0009) with significantly higher PD‐1 ligand‐positive T cells (PD‐L1: 19·8 ± 11·8%; P ≥ 0·019, PD‐L2: 12·6 ± 6·2%; P ≥ 0·023), CD19⁺ B cells (PD‐L1: 14·4 ± 10·4%; P ≥ 0·042, PD‐L2: 2·6 ± 1·43%; not significant) and CD14⁺ monocytes (PD‐L1: 40·2 ± 20·1%; P ≥ 0·047, PD‐L2: 22·4 ± 15·6%; P ≥ 0·032) compared with peripheral blood (PB) of MTB and healthy controls. The expression of PD‐1 was associated with a diminished number of cells producing effector cytokines interferon (IFN)‐γ, tumour necrosis factor (TNF)‐α, interleukin (IL)?2 and elevated apoptosis. Locally accumulated T cells were predominantly PD‐1⁺–PD‐L1⁺, and blocking this pathway restores the protective T cell response. We conclude that M. tuberculosis exploits the PD‐1 pathway to evade the host immune response by altering the T helper type 1 (Th1) and Th2 balance at the pathological site of MTB, thereby favouring disease dissemination.     

High frequency and proliferation of CD4+FOXP3+ Treg in HIV‐1‐infected patients with low CD4 counts

The frequency of Treg is reported to be higher in patients with chronic HIV type 1 (HIV‐1) infection and CD45RA⁺ Treg exist in normal adults. In this study, we found a lower absolute number (15 cells/μL) but a higher proportion (16.2%) of FOXP3⁺ cells (Treg) in the CD4⁺ population in treatment‐naïve HIV‐1 patients with low CD4 (<200 cells/μL) counts than in those with high CD4 counts (34 cells/μL and 9.3%) or healthy adults (48 cells/μL and 7.5%). In HIV‐1 patients, CD45RA⁺CCR7⁺, CD45RA^?CCR7⁺, and CD45RA^?CCR7^? subsets were identified in the Treg population, and the proportion of CD45RA^?CCR7^? Treg was higher (57.9%) in patients with low CD4 than high CD4 counts (38.3%). Treg were in a high proliferation state especially in patients with low CD4 counts. HIV viral load correlated positively with the Treg proliferation rate and the proportion of CD45RA^?CCR7^? Treg. Furthermore, the proliferation of Treg correlated positively with the CD45RA^?CCR7^? Treg proportion but negatively with Treg numbers. Successful antiretroviral therapy resulted in a limited increase in Treg numbers, but their frequency was reduced in 1–2 months due to a rapid rebound of FOXP3^? CD4⁺cells. Our results suggest that HIV‐activating Treg may be a reason for the high frequencies of Treg and CD45RA^?CCR7^? Treg in the peripheral blood of late‐stage HIV‐1‐infected patients.     

Mycobacterium tuberculosis‐specific CD8+ T cells are functionally and phenotypically different between latent infection and active disease

Protective immunity to Mycobacterium tuberculosis (Mtb) remains poorly understood and the role of Mtb‐specific CD8⁺ T cells is controversial. Here we performed a broad phenotypic and functional characterization of Mtb‐specific CD8⁺ T cells in 326 subjects with latent Mtb infection (LTBI) or active TB disease (TB). Mtb‐specific CD8⁺ T cells were detected in most (60%) TB patients and few (15%) LTBI subjects but were of similar magnitude. Mtb‐specific CD8⁺ T cells in LTBI subjects were mostly T_EMRA cells (CD45RA⁺CCR7^?), coexpressing 2B4 and CD160, and in TB patients were mostly T_EM cells (CD45RA^?CCR7^?), expressing 2B4 but lacking PD‐1 and CD160. The cytokine profile was not significantly different in both groups. Furthermore, Mtb‐specific CD8⁺ T cells expressed low levels of perforin and granulysin but contained granzymes A and B. However, in vitro‐expanded Mtb‐specific CD8⁺ T cells expressed perforin and granulysin. Finally, Mtb‐specific CD8⁺ T‐cell responses were less frequently detected in extrapulmonary TB compared with pulmonary TB patients. Mtb‐specific CD8⁺ T‐cell proliferation was also greater in patients with extrapulmonary compared with pulmonary TB. Thus, the activity of Mtb infection and clinical presentation are associated with distinct profiles of Mtb‐specific CD8⁺ T‐cell responses. These results provide new insights in the interaction between Mtb and the host immune response.     

The effect of allogeneic in vitro stimulation and in vivo immunization on memory CD4+ T‐cell APOBEC3G expression and HIV‐1 infectivity

Allogeneic immunity is one of the most potent natural immune responses. APOBEC3G (A3G) is an intracellular anti‐viral factor that deaminates cytidine to uridine. Allogeneic stimulation of human CD4⁺ T cells in vitro upregulated A3G mRNA and a significant correlation was found between the mixed leukocyte reaction and A3G mRNA. The mechanism of upregulation of A3G mRNA involves interaction between HLA on DC and TCR of CD4⁺ T cells, which is ZAP70 and downstream ERK phosphokinase signalling dependent and induces CD40L and A3G mRNA expression in CD4⁺ T cells. Alloimmune‐induced A3G was found to be significantly increased in CD45RA^?, CCR5⁺ and CD45RA^?CCR7^? subsets of effector memory T cells. In vivo studies of women alloimmunized with their partners' PBMC also showed a significant increase in A3G protein in CD4⁺ T cells, CD45RO⁺ memory and CCR7^? effector memory T cells. The functional effect of allostimulation upregulating A3G mRNA was demonstrated by a significant decrease in in vitro infectivity, using GFP‐labelled pseudovirus and confirmed by a decrease in HIV‐1 (BaL) infection of primary CD4⁺ T cells. The results suggest that alloimmunization offers an alternative or complementary strategy in inducing an innate anti‐viral factor that inhibits HIV‐1 infection.     

CCR5 expression,haplotype and immune activation in protection from infection in HIV‐exposed uninfected individuals in HIV‐serodiscordant relationships

Several host factors have been implicated in resistance to HIV infection in individuals who remain HIV‐seronegative despite exposure. In a cohort of HIV‐serodiscordant heterosexual couples, we investigated interactions between systemic inflammation and T‐cell activation in resistance to HIV infection. Males and females in stable long‐term relationships with either HIV‐infected or uninfected partners were recruited, blood T‐cell activation (CD38, HLA‐DR, CCR5 and Ki67) and plasma cytokine concentrations were evaluated. The HIV‐negative exposed individuals had significantly lower frequencies of CCR5⁺ CD4⁺ and CD8⁺ T cells than unexposed individuals. Mean fluorescence intensity of CCR5 expression on CD4⁺ T cells was significantly lower in HIV‐negative exposed than unexposed individuals. Protective CCR5 haplotypes (HHA/HHF*2, HHF*2/HHF*2, HHC/HHF*2, HHA/HHA, HHA/HHC and HHA/HHD) tended to be over‐represented in exposed compared with unexposed individuals (38% versus 28%, P = 0·58) whereas deleterious genotypes (HHC/HHD, HHC/HHE, HHD/HHE, HHD/HHD and HHE/HHE) were under‐represented (26% versus 44%; P = 0·16). Plasma concentrations of interleukin‐2 (P = 0·02), interferon‐γ (P = 0·05) and granulocyte–macrophage colony‐stimulating factor (P = 0·006) were lower in exposed compared with unexposed individuals. Activation marker expression and systemic cytokine concentrations were not influenced by gender. We conclude that the dominant signature of resistance to HIV infection in this cohort of exposed but uninfected individuals was lower T‐cell CCR5 expression and plasma cytokine concentrations.     

Separation of plasma‐derived exosomes into CD3(+) and CD3(–) fractions allows for association of immune cell and tumour cell markers with disease activity in HNSCC patients

Head and neck squamous cell carcinoma (HNSCC) is a highly immunosuppressive malignancy. Exosomes in HNSCC patients' plasma are enriched in inhibitory cargo and mediate immunosuppression. As these exosomes are products of various cells, the cellular origin of immunoregulatory proteins they carry is unknown. To test whether tumour‐ or T cell‐derived exosomes in patients' plasma are immunosuppressive and impact upon disease activity, we separated CD3^(–) from CD3⁽⁺⁾ exosomes by immunocapture using anti‐CD3 antibodies. The exosome protein cargo was evaluated for immunoregulatory proteins using on‐bead flow cytometry. Tumour protein‐enriched CD3^(–) exosomes were CD44v3⁽⁺⁾. Surprisingly, mean levels of programmed death ligand 1 (PD‐L1), cytotoxic T lymphocyte antigen 4 (CTLA‐4) and cyclooxygenase‐2 (COX‐2) were similar in CD3⁽⁺⁾ and CD3^(–) exosomes, although the latter induced higher (P < 0·0025) ex‐vivo apoptosis of CD8⁽⁺⁾ T cells and greater (P < 0·005) conversion of CD4⁺ T cells to CD4⁽⁺⁾CD39⁽⁺⁾ regulatory T cells (T_reg). CD3⁽⁺⁾ and CD3^(–) exosomes carrying high levels of immunosuppressive proteins were highly effective in mediating these functions. Exosomes of patients with Union for International Cancer Control (UICC) stages III/IV disease had higher levels of PD‐L1 and COX‐2 than stages I/II patients (P < 0·005). Patients with nodal involvement had exosomes with the higher inhibitory protein content than N0 patients (P < 0·03). CD3⁽⁺⁾ and CD3^(–) exosomes of HNSCC patients had higher PD‐L1, COX‐2 and CD15s levels than healthy donors' exosomes (P < 0·009), although levels of immunostimulatory OX40 or OX40L were not different. By isolating CD3^(–)/CD44v3‐enriched and CD3⁽⁺⁾ exosomes from plasma, the cellular origins of immunoregulatory proteins they carry were identified. Association of exosome molecular profiles with disease progression supports the exosome potential as future cancer biomarkers.     

CCR7+ Central and CCR7− Effector Memory CD4+ T Cells in Human Cutaneous Leishmaniasis

Purpose

The profile of central (=T_CM) and effector (=T_EM) memory CD4⁺ T cell subsets and the possible role as surrogate markers of protection is studied in the volunteers with history of cutaneous leishmaniasis (HCL).

Methods

Profile of T cell subsets based on CCR7/CD45RA expressions and phenotypic changes after soluble Leishmania antigen (SLA) stimulation were analyzed. Then, sorted CD4⁺CD45RO^?CD45RA⁺ naïve T, CD4⁺CD45RO⁺CD45RA^?CCR7^? T_EM, CD4⁺CD45RO⁺CD45RA^?CCR7⁺ T_CM subsets were cultured with SLA for proliferation, cytokine production and intracellular cytokine assays.

Results

In the HCL and control volunteers, the mean frequencies of CD4⁺CD45RA⁺CCR7⁺ naïve T cells and CD4⁺CD45RA^?CCR7^? T_EM cells were higher than the other subsets before culture. Frequency of naïve T cells and CD4⁺CD45RA^?CCR7⁺ T_CM cells was significantly decreased (P?=?0.01 for naïve T and P?<?0.05 for T_CM cells) and frequency of T_EM cells was significantly increased after SLA stimulation compared to before culture (P?<?0.001). By CFSE labeling, CD4⁺CD45RO⁺CD45RA^?CCR7⁺ T_CM cells showed more proliferation potential than CD4⁺CD45RO⁺CD45RA^?CCR7^? T_EM cells. Stimulation of the T_EM cells in HCL volunteers induced a significantly higher IFN-γ production (P?=?0.04) with higher number of intracellular IFN-γ positive cells (P?=?0.032) than the same cells from controls. A significantly higher number of T_CM cells produced IL-2 in HCL volunteers compared with controls (P?<?0.05). Most of the intracellular IFN-γ positive T_EM cells were proliferating CFSE-dim populations (P?<?0.05).

Conclusions

A combination of Leishmania-reactive IFN-γ producing CD4⁺CD45RO⁺CD45RA^?CCR7^? T_EM and Leishmania-reactive IL-2 producing CD4⁺CD45RO⁺CD45RA^?CCR7⁺ T_CM are identified in individuals with history of CL which might play a role in protective recall immune response against Leishmania infection.     

Co‐inhibitory profile and cytotoxicity of CD57+PD‐1– T cells in end‐stage renal disease patients

Blockade of the CD80/86‐CD28 pathway by belatacept after kidney transplantation is associated with an increased risk of rejection compared with standard, calcineurin inhibitor (CNI)‐based therapy. CD28^– T cells, which express CD57, are not susceptible to belatacept treatment. High numbers of CD4⁺CD57⁺programmed death 1 (PD‐1)^– T cells pretransplantation have been associated with a higher chance of rejection, although conflicting data have been reported. To investigate the working mechanism behind this possible higher chance of rejection, we studied the expression of co‐inhibitory molecules (CD223, CD244 and PD‐1), proliferative capacity and cytotoxic potential of fluorescence activated cell sorted (FACS) CD4⁺CD57⁺PD‐1^– and CD8⁺CD57⁺PD‐1^– T cells, and their CD57^– control populations, after alloantigen stimulation. The effect of belatacept on the cytotoxic capacity of pretransplantation peripheral blood mononuclear cells from 20 patients who received belatacept post‐transplantation was also tested. Expression of co‐inhibitory molecule CD223 increased by approximately 10‐fold after allogeneic stimulation in all four T cell subsets. Proliferation and up‐regulation of CD244 and PD‐1 was observed for CD4⁺CD57^‐PD‐1^– T cells after allogeneic stimulation, but no up‐regulation of these markers occurred on CD8⁺ T cells or CD4⁺CD57⁺PD‐1^– T cells. However, CD4⁺CD57⁺PD‐1^– T cells and, to a lesser extent, CD8⁺CD57⁺PD‐1^– T cells displayed higher cytotoxicity as indicated by granzyme B expression. Belatacept inhibited the cytotoxic potential of CD4⁺CD57⁺PD‐1^– T cells (median of inhibition 31%, P < 0·01) and CD8⁺CD57⁺PD‐1^– T cells (median of inhibition 10%, P < 0·05). In conclusion, alloantigen‐activated CD4⁺CD57⁺PD‐1^– T cells exhibited a less proliferative but more cytotoxic profile than their CD57^– counterparts. Their cytotoxic capacity can be inhibited partly by belatacept and was not associated with development of rejection after kidney transplantation.     

HIV–TB coinfection impairs CD8+ T‐cell differentiation and function while dehydroepiandrosterone improves cytotoxic antitubercular immune responses

Tuberculosis (TB) is the leading cause of death among HIV‐positive patients. The decreasing frequencies of terminal effector (T_TE) CD8⁺T cells may increase reactivation risk in persons latently infected with Mycobacterium tuberculosis (Mtb). We have previously shown that dehydroepiandrosterone (DHEA) increases the protective antitubercular immune responses in HIV–TB patients. Here, we aimed to study Mtb‐specific cytotoxicity, IFN‐γ secretion, memory status of CD8⁺T cells, and their modulation by DHEA during HIV–TB coinfection. CD8⁺T cells from HIV–TB patients showed a more differentiated phenotype with diminished naïve and higher effector memory and T_TE T‐cell frequencies compared to healthy donors both in total and Mtb‐specific CD8⁺T cells. Notably, CD8⁺T cells from HIV–TB patients displayed higher Terminal Effector (T_TE) CD45RA^dim proportions with lower CD45RA expression levels, suggesting a not fully differentiated phenotype. Also, PD‐1 expression levels on CD8⁺T cells from HIV–TB patients increased although restricted to the CD27⁺ population. Interestingly, DHEA plasma levels positively correlated with T_TE in CD8⁺T cells and in vitro DHEA treatment enhanced Mtb‐specific cytotoxic responses and terminal differentiation in CD8⁺T cells from HIV–TB patients. Our data suggest that HIV–TB coinfection promotes a deficient CD8⁺ T‐cell differentiation, whereas DHEA may contribute to improving antitubercular immunity by enhancing CD8⁺T‐cell functions during HIV–TB coinfection.     

Regulatory T‐cells in acute dengue viral infection

Although regulatory T‐cells (T_regs) have been shown to be expanded in acute dengue, their role in pathogenesis and their relationship to clinical disease severity and extent of viraemia have not been fully evaluated. The frequency of T_regs was assessed in 56 adult patients with acute dengue by determining the proportion of forkhead box protein 3 (FoxP3) expressing CD4⁺ CD25⁺T‐cells (FoxP3⁺ cells). Dengue virus (DENV) viral loads were measured by quantitative real‐time polymerase chain reaction (PCR) and DENV‐specific T‐cell responses were measured by ex‐vivo interferon (IFN)‐γ enzyme‐linked immunospot (ELISPOT) assays to overlapping peptide pools of DENV‐NS3, NS1 and NS5. CD45RA and CCR4 were used to phenotype different subsets of T‐cells and their suppressive potential was assessed by their expression of cytotoxic T lymphocyte‐antigen 4 (CTLA‐4) and Fas. While the frequency of FoxP3⁺ cells in patients was significantly higher (P < 0·0001) when compared to healthy individuals, they did not show any relationship with clinical disease severity or the degree of viraemia. The frequency of FoxP3⁺ cells did not correlate with either ex‐vivo IFN‐γ DENV‐NS3‐, NS5‐ or NS1‐specific T‐cell responses. FoxP3⁺ cells of patients with acute dengue were predominantly CD45RA⁺ FoxP3^low, followed by CD45RA‐FoxP3^low, with only a small proportion of FoxP3⁺ cells being of the highly suppressive effector Treg subtype. Expression of CCR4 was also low in the majority of T‐cells, with only CCR4 only being expressed at high levels in the effector T_reg population. Therefore, although FoxP3⁺ cells are expanded in acute dengue, they predominantly consist of naive T_regs, with poor suppressive capacity.     

Contribution of the PD-1 ligands/PD-1 signaling pathway to dendritic cell-mediated CD4+ T cell activation

Dendritic cells (DC) are extremely proficient inducers of naïve CD4⁺ T cell activation due to their high expression level of peptide‐MHC and an array of accessory molecules involved in cell migration, adhesion and co‐signaling, including PD‐1 ligand 1 (PD‐L1) and PD‐1 ligand 2 (PD‐L2). Whether PD‐L1 and PD‐L2 have a stimulatory or inhibitory function is a matter of debate, and could be partially dependent on the model system used. In this study we examined the role of PD‐L1 and PD‐L2 expressed by DC in naïve CD4⁺ T cell activation in a more physiologically relevant model system, using OVA‐specific T cells in combination with various levels of TCR stimulation. Overexpression of PD‐L1 or PD‐L2 by DC did not inhibit T cell proliferation, even when B7–1 and B7–2 mediated costimulation was absent, although IL‐2 production was consistently decreased. Surprisingly, blocking PD‐L1 and PD‐L2 with soluble programmed death‐1 (sPD‐1) also inhibited T cell activation, probably via reverse signaling via PD‐L1 and/or PD‐L2 into DC, leading to reduced DC maturation. This study suggests a relatively minor contribution of PD‐1 ligands in DC‐driven CD4⁺ T cell activation and provides evidence for reverse signaling by PD‐L1 and PD‐L2 into DC, resulting in a suppressive DC phenotype.     

Impact of changes in antigen level on CD38/PD‐1 co‐expression on HIV‐specific CD8 T cells in chronic,untreated HIV‐1 infection

Excessive immune activation is a hallmark of chronic uncontrolled HIV infection. During the past years, growing evidence suggests that immune inhibitory signals also play an important role in progressive disease. However, the relationship between positive and negative immune signals on HIV‐specific CD8 T cells has not been studied in detail so far in chronic HIV‐1 infection. In this study, the expression of markers of positive (CD38) and negative (PD‐1) immune signals on virus‐specific CD8 T cells in chronic, untreated HIV‐1 infection was evaluated using intracellular cytokine staining. Viral escape mutations were assessed by autologous virus sequence analysis and subsequent peptide titration assays. Single‐epitope CD8 T‐cell responses toward Gag, Pol, and Nef were compared in 12 HIV‐1 controllers (viral load <5,000 cp/ml) and 12 HIV‐1 progressors (viral load >50,000 cp/ml) and a highly significant increase of CD38/PD‐1 co‐expression on virus‐specific CD8 T cells in progressors was found (P < 0.0001). The level of CD38/PD‐1 co‐expression was independent of epitope specificity. Longitudinal follow‐up revealed a clear drop in CD38/PD‐1 co‐expression on virus‐specific CD8 T cells after the suppression of antigen following either viral escape mutation or the initiation of HAART (P = 0.004). Antigen persistence with a fluctuating viral load revealed stable levels of CD38/PD‐1 co‐expression whereas significant rises in viral load were accompanied or even preceded by substantial increases in CD38/PD‐1 co‐expression. The CD38/PD‐1 phenotype clearly distinguishes HIV‐specific CD8 T‐cell responses between controllers and progressors. Whether it plays a causative role in disease progression remains debatable. J. Med. Virol. 82:358–370, 2010. © 2010 Wiley‐Liss, Inc.