Augmented induction of CD8+ cytotoxic T-cell response and antitumour resistance by T helper type 1-inducing peptide

The effector CD8(+) T cells recognize major histocompatibility complex (MHC) class I binding altered self-peptides expressed in tumour cells. Although the requirement for CD4(+) T helper type 1 (Th1) cells in regulating CD8(+) T cells has been documented, their target epitopes and functional impact in antitumour responses remain unclear. We examined whether a potent immunogenic peptide of Mycobacterium tuberculosis eliciting Th1 immunity contributes to the generation of CD8(+) T cells and to protective antitumour immune responses to unrelated tumour-specific antigens. Peptide-25, a major Th epitope of Ag85B from M. tuberculosis preferentially induced CD4(+) Th1 cells in C57BL/6 mice and had an augmenting effect on Th1 generation for coimmunized unrelated antigenic peptides. Coimmunization of mice with Peptide-25 and ovalbumin (OVA) or Peptide-25 and B16 melanoma peptide [tyrosinase-related protein-2 (TRP-2)] for MHC class I led to a profound increase in CD8(+) T cells specific for OVA and TRP-2 peptides, respectively. This heightened response depended on Peptide-25-specific CD4(+) T cells and interferon-gamma-producing T cells. In tumour protection assays, immunization with Peptide-25 and OVA resulted in the enhancement of CD8(+) cytotoxic cell generation specific for OVA and the growth inhibition of EL-4 thymoma expressing OVA peptide leading to the tumour rejection. These phenomena were not achieved by immunization with OVA alone. Peptide-25-reactive Th1 cells counteractivated dendritic cells in the presence of Peptide-25 leading them to activate and present OVA peptide to CD8(+) cytotoxic T cells.     

Identification of an HLA-A*0201-restrictive CTL epitope from MUC4 for applicable vaccine therapy

Recent research has indicated that MUC4 plays an important role in the development of many tumors and may prove useful as a novel cancer immunotherapy target. We aimed to identify HLA-A*0201-restrictive cytotoxic T lymphocyte (CTL) epitopes of the cancer-associated antigen MUC4. The MUC4 sequence was scanned for immunogenic peptides using HLA-binding prediction software. Dendritic cells (DCs) from peripheral blood mononuclear cells (PBMCs) were induced by cytokines. Five possible CTL epitopes were selected by software analysis, synthesized, and used to pulse mature DCs. The CD8⁺ T cells from PBMCs from an HLA-A*0201 healthy donor were stimulated with autologous MUC4-peptide-loaded DCs and expanded in vitro. T cell activation was assessed by ELISPOT, and cytotoxicity was determined by ⁵¹chromium (⁵¹Cr)-release assays. Our results show that CTLs induced by peptide P01204 could lyse T2 cells pulsed with peptide P01204 and HCT-116 cells (MUC4⁺, HLA-A2⁺). Compared with a control peptide, P01204 increased the number of IFN-γ producing T cells. Overall, these results suggest that P01204 is a novel HLA-A*0201-restrictive CTL epitope of the cancer-associated antigen MUC4. This will provide a foundation for the development of tumor-specific peptide vaccines.     

Identification of a dengue virus‐specific HLA‐A*0201‐restricted CD8+ T cell epitope

In this study, a combination of epitope‐prediction programs and in vitro assays was used to identify dengue virus (DENV)‐specific CD8⁺ T cell epitopes. Peripheral blood mononuclear cells (PBMCs) isolated from patients who recovered from dengue fever were stimulated with candidate epitope peptides derived from DENV, which were predicted by using SYFPEITHI and RANKpep epitope‐prediction programs. The IFN‐γ ELISpot results and the results of intracellular staining of IFN‐γ showed that peptides NS4b_40 (TLYAVATTI), E_256 (QEGAMHTAL), NS3_205 (LPAIVREAI), NS5_210 (SRNSTHEMY), and NS3_207 (AIVREAIKR) could induce the recall response of CD8⁺ T cells. Furthermore, the results of the MHC–peptide complex stabilization assay revealed that peptide NS4b_40 (TLYAVATTI) has a high affinity for HLA‐A*0201 molecules. The IFN‐γ ELISpot results and staining of intracellular IFN‐γ confirmed that this peptide could induce high‐level CD8⁺ T cell response in HLA‐A*0201 positive PBMCs. Peptide NS4b_40 (TLYAVATTI) was identified as a novel DENV‐specific HLA‐A*0201‐restricted CD8⁺ T cell epitope. J. Med. Virol. 82:642–648, 2010. © 2010 Wiley‐Liss, Inc.     

Invariant chain as a vehicle to load antigenic peptides on human MHC class I for cytotoxic T‐cell activation

Protective T‐cell responses depend on efficient presentation of antigen (Ag) in the context of major histocompatibility complex class I (MHCI) and class II (MHCII) molecules. Invariant chain (Ii) serves as a chaperone for MHCII molecules and mediates trafficking to the endosomal pathway. The genetic exchange of the class II‐associated Ii peptide (CLIP) with antigenic peptides has proven efficient for loading of MHCII and activation of specific CD4⁺ T cells. Here, we investigated if Ii could similarly activate human CD8⁺ T cells when used as a vehicle for cytotoxic T‐cell (CTL) epitopes. The results show that wild type Ii, and Ii in which CLIP was replaced by known CTL epitopes from the cancer targets MART‐1 or CD20, coprecipitated with HLA‐A*02:01 and mediated colocalization in the endosomal pathway. Furthermore, HLA‐A*02:01‐positive cells expressing CLIP‐replaced Ii efficiently activated Ag‐specific CD8⁺ T cells in a TAP‐ and proteasome‐independent manner. Finally, dendritic cells transfected with mRNA encoding IiMART‐1 or IiCD20 primed naïve CD8⁺ T cells. The results show that Ii carrying antigenic peptides in the CLIP region can promote efficient presentation of the epitopes to CTLs independently of the classical MHCI peptide loading machinery, facilitating novel vaccination strategies against cancer.     

CTL recognition of HIV‐1‐infected cells via cross‐recognition of multiple overlapping peptides from a single 11‐mer Pol sequence

It is known that overlapping HIV‐1 peptides of different lengths can be presented by a given HLA class I molecule. However, the role of those peptides in CD8⁺ T cells recognition of HIV‐1‐infected cells remains unclear. Here we investigated the recognition of overlapping 8‐mer to 11‐mer peptides of Pol 155–165 by HLA‐B*54:01‐restricted CD8⁺ T cells. The analysis of ex vivo T cells using ELISPOT and tetramer binding assays showed that there were different patterns of CD8⁺ T‐cell responses to these peptides among chronically HIV‐1‐infected HLA‐B*54:01⁺ individuals, though the response to the 9‐mer peptide was the strongest among them. CD8⁺ T‐cell clones with TCRs specific for the 9‐mer, 10‐mer, and/or 11‐mer peptides effectively killed HIV‐1‐infected cells. Together, these results suggest that the 9‐mer and 10‐mer peptides could be predominantly presented by HLA‐B*54:01, though it remains possible that the 11‐mer peptide was also presented by this HLA allele. The present study demonstrates effective CD8⁺ T‐cell recognition of HIV‐1‐infected cells via presentation of multiple overlapping HIV‐1 peptides and cross‐recognition by the CD8⁺ T cells.     

Shared and distinct roles of T peripheral helper and T follicular helper cells in human diseases

The interactions of CD4⁺ T cells and B cells are fundamental for the generation of protective antibody responses, as well as for the development of harmful autoimmune diseases. Recent studies of human tissues and blood samples have established a new subset of CD4⁺ B helper T cells named peripheral helper T (Tph) cells. Unlike T follicular helper (Tfh) cells, which interact with B cells within lymphoid organs, Tph cells provide help to B cells within inflamed tissues. Tph cells share many B helper-associated functions with Tfh cells and induce B cell differentiation toward antibody-producing cells. The differentiation mechanism is also partly shared between Tph and Tfh cells in humans, and both Tfh and Tph cells can be found within the same tissues, including cancer tissues. However, Tph cells display features distinct from those of Tfh cells, such as the expression of chemokine receptors associated with Tph cell localization within inflamed tissues and a low Bcl-6/Blimp1 ratio. Unlike that of Tfh cells, current evidence shows that the target of Tph cells is limited to memory B cells. In this review, we first summarize recent findings on human Tph cells and discuss how Tph and Tfh cells play shared and distinct roles in human diseases.     

Prediction and characterization of helper T‐cell epitopes from pneumococcal surface adhesin A

Pneumococcal surface adhesin A (PsaA) is a multifunctional lipoprotein known to bind nasopharyngeal epithelial cells, and is significantly involved in bacterial adherence and virulence. Identification of PsaA peptides that optimally bind human leucocyte antigen (HLA) and elicit a potent immune response would be of great importance to vaccine development. However, this is hindered by the multitude of HLA polymorphisms in humans. To identify the conserved immunodominant epitopes, we used an experimental dataset of 28 PsaA synthetic peptides and in silico methods to predict specific peptide‐binding to HLA and murine MHC class II molecules. We also characterized spleen and cervical lymph node (CLN) ‐derived T helper (Th) lymphocyte cytokine responses to these peptides after Streptococcus pneumoniae strain EF3030 challenge in mice. Individual, yet overlapping, peptides 15 amino acids in length revealed residues of PsaA that consistently caused the highest interferon‐γ, interleukin‐2 (IL‐2), IL‐5 and IL‐17 responses and proliferation as well as moderate IL‐10 and IL‐4 responses by ex vivo re‐stimulated splenic and CLN CD4⁺ T cells isolated from S. pneumoniae strain EF3030‐challenged F₁ (B6 ×  BALB/c) mice. In silico analysis revealed that peptides from PsaA may interact with a broad range of HLA‐DP, ‐DQ and ‐DR alleles, due in part to regions lacking β‐turns and asparagine endopeptidase sites. These data suggest that Th cell peptides (7, 19, 20, 22, 23 and 24) screened for secondary structures and MHC class II peptide‐binding affinities can elicit T helper cytokine and proliferative responses to PsaA peptides.     

Extensive major histocompatibility complex class I binding promiscuity for Mycobacterium tuberculosis TB10.4 peptides and immune dominance of human leucocyte antigen (HLA)‐B*0702 and HLA‐B*0801 alleles in TB10.4 CD8+ T‐cell responses

The molecular definition of major histocompatibility complex (MHC) class I‐presented CD8⁺ T‐cell epitopes from clinically relevant Mycobacterium tuberculosis (Mtb) target proteins will aid in the rational design of T‐cell‐based diagnostics of tuberculosis (TB) and the measurement of TB vaccine‐take. We used an epitope discovery system, based on recombinant MHC class I molecules that cover the most frequent Caucasian alleles [human leucocyte antigen (HLA)‐A*0101, A*0201, A*0301, A*1101, A*2402, B*0702, B*0801 and B*1501], to identify MHC class I‐binding peptides from overlapping 9‐mer peptides representing the Mtb protein TB10.4. A total of 33 MHC class I‐binding epitopes were identified, spread across the entire amino acid sequence, with some clustering at the N‐ and C‐termini of the protein. Binding of individual peptides or closely related peptide species to different MHC class I alleles was frequently observed. For instance, the common motif of xIMYNYPAMx bound to six of eight alleles. Affinity (50% effective dose) and off‐rate (half life) analysis of candidate Mtb peptides will help to define the conditions for CD8⁺ T‐cell interaction with their nominal MHC class I‐peptide ligands. Subsequent construction of tetramers allowed us to confirm the recognition of some of the epitopes by CD8⁺ T cells from patients with active pulmonary TB. HLA‐B alleles served as the dominant MHC class I restricting molecules for anti‐Mtb TB10.4‐specific CD8⁺ T‐cell responses measured in CD8⁺ T cells from patients with pulmonary TB.     

Phenotypic profiling of CD279 and CD185 level on helper T cells in patients with autoimmune hepatitis

The break of immune tolerance and transition from acute to chronic information in the liver lead to the development and persistence of autoimmune hepatitis. Elevated CD279 expression has been detected in type 1 autoimmune hepatitis (AIH) patients with anti-nuclear and/or anti-smooth muscle antibodies. This is correlated with increased CD185 positive CD4⁺ helper T cells which activate B cells producing autoantibodies. However, detailed CD279 profiles on T cell subsets were not clear. Here, we analysed PBMCs of 53 AIH patients and 18 healthy donors. Our work revealed that for their central and effector memory compartment of CD4 T cells was markedly increased. Furthermore, the percentage of CD279⁺CD185⁺ and CD279⁻CD185⁺ T follicular helper cells as well as CD279⁺CD185⁻ but not CD279⁻CD185⁻ populations are significantly enlarged in naïve, central and effector memory subsets. This study suggests that high levels of CD279 and CD185 expression are strongly associated with AIH and may inform disease progression and provide a potential novel therapeutic target.     

Quantification of the CD8+ T cell response against a mucin epitope in patients with breast cancer

Introduction: Mucin 1, encoded by the MUC1 gene, is a tumor-associated antigen expressed on the surface of breast cancer cells. It would be of interest to see whether there is a naturally existing T cell immune response against mucin epitopes in cancer patients. Materials and Methods: Using tetramer and interferon-γ assays, the immune response to one MUC1 peptide epitope in the peripheral blood of breast cancer patients was quantified. The data were compared with the clinical course of the patients. Results: CD8⁺ T cells capable of recognizing the HLA-A*0201-restricted STAPPVHNV epitope were detected in 9 of 19 patients with a frequency ranging 0.01–0.082%. No significant difference was found between the occurrence of epitope-specific CD8⁺ T cells of patients with progressive disease and disease-free patients. However, all patients with stable disease showed a specific immune response, including both patients with the highest frequency. Conclusions: The results of this study provide further evidence that a natural specific cellular immune response against this mucin epitope exists in breast cancer patients.     

Preferential pairing of T and B cells for production of antibodies without covalent association of T and B epitopes

T cell from H-2^b mice recognize at least 12 sequence regions on the Torpedo acetylcholine receptor (TAChR) α, γ and δ subunits. Immunization of C57BL/6 mice with individual synthetic TAChR sequences known to contain CD4⁺ epitopes resulted in most cases (10 out of 12 peptides) in anti-peptide antibody (Ab) production, indicating that short TAChR sequences contain both CD4⁺ and B epitopes. Immunization of C57BL/6 mice with a mixture of a CD4⁺ epitope peptide, from the TAChR or from an unrelated protein, plus another TAChR sequence forming a “pure” B epitope (Tα63–80), induced in most cases anti-peptide Ab and CD4⁺ cell sensitization only against the peptide containing the CD4⁺ epitope. However, when the T epitope peptide Tα360–378 was co-injected with the B epitope, Ab were also produced against the B epitope peptide. Injection of the individual peptides Tα360–378 and Tα63–80 at different and distant sites along the back of mice elicited sensitization of CD4⁺ cells and Ab production only against peptide Tα360–378. Therefore, when optimal cooperation between T and B cells occurs, spatial proximity but not covalent association of the B and the CD4⁺ epitope is necessary for production of Ab against the B epitope.     

CD4+ T cells recognize diverse epitopes within GAD65: implications for repertoire development and diabetes monitoring

Type 1 diabetes is associated with T‐cell responses to β‐cell antigens such as GAD65. Single T‐cell epitopes have been investigated for immune monitoring with some success, but multiple epitopes may be required to fully characterize responses in all subjects. We used a systematic approach to examine the diversity of the GAD65‐specific T‐cell repertoire in subjects with DRB1*04:01 haplotypes. Using class II tetramers, we observed responses to 15 GAD65 epitopes, including five novel epitopes. The majority were confirmed to be processed and presented. Upon stimulation with peptides, GAD‐specific responses were equally broad in subjects with diabetes and healthy controls in the presence or absence of CD25⁺ T cells, suggesting that a susceptible HLA is sufficient to generate a potentially autoreactive repertoire. Without depleting CD25⁺ cells, GAD_113–132 and GAD_265–284 responses were significantly stronger in subjects with diabetes. Although nearly every individual responded to at least one GAD65 epitope, most were seen in less than half of the subjects tested, suggesting that multiple epitopes are recommended for immune monitoring.     

Atopic asthma: differential activation phenotypes among memory T helper cells

Background T cells have been implicated in the pathogenesis of atopic asthma. We have previously shown that memory T helper cells (CD4⁺CD45RO⁺) are preferentially activated relative to naïve T helper cells (CD4⁺CD45RA⁺) after bronchial allergen challenge. However, specific T helper subpopulations that are activated in atopy and/or asthma remain undefined. Objective To determine the T helper subpopulations and activation phenotypes relevant to acute and stable asthma that may be common with or distinct from atopy. Methods Two groups of atopic asthmatics (ten acute and nine stable asthmatics) and two non‐asthmatic groups (14 non‐asthmatic atopics and eight normal non‐atopic controls) were analysed. Ten acute asthmatics were assessed in the emergency room during an acute episode (FEV₁ 43.6% ± 18.4). Nine stable asthmatics were assessed during a symptom‐free period (FEV₁ 85% ± 6). Using multiple colour flow cytometry we analysed T cell subpopulations and the expression of IL‐2‐receptor (IL‐2R) and MHC‐class II antigens (MHC II) on naïve and memory T helper cells in the peripheral blood of asthmatic and non‐asthmatic groups. Results Atopic asthmatics (acute and stable) had an increased percentage of memory T helper cells expressing IL‐2R compared with normal non‐atopics (mean SD 16.1 ± 6%, 12.4 ± 2% and 7.7 ± 1.8%, P < 0.05) but not compared with non‐asthmatic atopics (10 ± 3.5%). Naïve T helper cells had low expression of IL‐2R and MHC II in all four groups. MHC II antigen expression was increased in memory T helper cells of asthmatics (acute and stable) compared with normal non‐atopics (13.9 ± 7.5, 10.6 ± 5 and 4.9 ± 2.5, P < 0.05) but not compared with non‐asthmatic atopics (7.92 4). A novel finding was that IL‐2R and the MHC II molecules were mainly expressed in non‐overlapping populations and coexpression was found predominantly on memory T helper cells. Asthmatics (acute and stable) had higher proportion of double positive memory T helper cells (IL‐2R⁺MHC II⁺) compared with both non‐asthmatic groups (P < 0.05). Conclusions We demonstrate a differential expression of IL‐2R⁺ and MCH II⁺ on CD45RO⁺ T helper cells that would suggest that there are three subsets of activated memory T helper cells in asthmatics. Two non‐overlapping IL‐2R⁺ or MHC II⁺ CD45RO⁺ T helper cells and a third subpopulation of activated cells that coexpress IL‐2R and MHC II (double positives). This latter subpopulation is significantly higher in asthmatics (acute or stable) compared with both non‐asthmatic groups, suggesting a specific T helper activation phenotype distinct to atopic asthmatics as compared with atopic non‐asthmatics.     

CD40–CD40Ligand interactions and their role in cytotoxic T lymphocyte priming and anti-tumor immunity

Tumor–specific immunity relies on interactions with the antigen receptors as well as costimulatory molecules, such as those of the CD28/B7 pathway and relatives of the TNFR gene family. Cytotoxic T lymphocytes specific for cellular antigens are in general primed by professional antigen–presenting cells that indirectly present antigens derived from cells in the periphery. This cross–priming of CD8⁺T cells requires signals provided by CD4⁺T helper cells. Although this dependency on [help’ for efficient cytotoxic T lymphocyte priming has been well documented, it was only recently that more mechanistic insight into the nature of this event has been obtained. In the absence of the CD4⁺T cells, signalling through CD40 can replace `help' required for priming of these CD8⁺T cells. These observations indicate that T cell help for cytotoxic T lymphocytes is mediated by CD40–CD40Ligand (L) interactions, most likely through activation of professional antigen–presenting cells that cross–present cellular antigens to these T cells.     

CD8+ T cells of Listeria monocytogenes‐infected mice recognize both linear and spliced proteasome products

CD8⁺ T cells responding to infection recognize pathogen‐derived epitopes presented by MHC class‐I molecules. While most of such epitopes are generated by proteasome‐mediated antigen cleavage, analysis of tumor antigen processing has revealed that epitopes may also derive from proteasome‐catalyzed peptide splicing (PCPS). To determine whether PCPS contributes to epitope processing during infection, we analyzed the fragments produced by purified proteasomes from a Listeria monocytogenes polypeptide. Mass spectrometry identified a known H‐2K^b‐presented linear epitope (LLO_296‐304) in the digests, as well as four spliced peptides that were trimmed by ERAP into peptides with in silico predicted H‐2K^b binding affinity. These spliced peptides, which displayed sequence similarity with LLO_296‐304, bound to H‐2K^b molecules in cellular assays and one of the peptides was recognized by CD8⁺ T cells of infected mice. This spliced epitope differed by one amino acid from LLO_296‐304 and double staining with LLO_296‐304‐ and spliced peptide‐folded MHC multimers showed that LLO_296‐304 and its spliced variant were recognized by the same CD8⁺ T cells. Thus, PCPS multiplies the variety of peptides that is processed from an antigen and leads to the production of epitope variants that can be recognized by cross‐reacting pathogen‐specific CD8⁺ T cells. Such mechanism may reduce the chances for pathogen immune evasion.     

Primed and naive helper T cells in labial glands from patients with Sjogren's syndrome

Summary This study has investigated the presence and distribution of B cells, T cells and T-cell subsets within labial glands of patients with primary Sjogren's syndrome (n=9) and secondary Sjogren's syndrome associated with rheumatoid arthritis (n=8) using a sequential double immunoperoxidase technique and true colour image analysis. The composition of the inflammatory infiltrates was similar in glands from both patient groups. B cells were normally present within large foci with few detected in diffuse infiltrates such that the ratio of TB cells in foci (2.41) was significantly lower than in diffuse infiltrates (7.31; P<0.001). In all infiltrates helper T cells (CD8^–, CD3⁺) predominated over suppressor/cytotoxic cells (CD8⁺, CD3⁺; 2.71). Analysis of primed (CD45RA^–, CD45RO⁺) and naive (CD45RA⁺, CD45RO^–) CD8^– T cells showed that the ratio of the primed to naive subset was significantly higher in focal (4.21) compared to diffuse (1.51;P< 0.001) areas of lymphoid infiltration. These results indicate that the focal lymphocytic infiltrates characteristic of Sjogren's syndrome contain B cells associated with a T-cell population consisting predominantly of primed CD8^– helper T cells. This latter population may be responsible for upregulating glandular B-cell activity in Sjogren's syndrome.     

Low expression of CD39+/CD45RA+ on regulatory T cells (Treg) cells in type 1 diabetic children in contrast to high expression of CD101+/CD129+ on Treg cells in children with coeliac disease

Type 1 diabetes (T1D) and coeliac disease are both characterized by an autoimmune feature. As T1D and coeliac disease share the same risk genes, patients risk subsequently developing the other disease. This study aimed to investigate the expression of T helper (Th), T cytotoxic (Tc) and regulatory T cells (T_reg) in T1D and/or coeliac disease children in comparison to healthy children. Subgroups of T cells (Th : CD4⁺ or Tc : CD8⁺); naive (CD27⁺CD28⁺CD45RA⁺CCR7⁺), central memory (CD27⁺CD28⁺CD45RA⁻CCR7⁺), effector memory (early differentiated; CD27⁺CD28⁺CD45RA⁻CCR7⁻ and late differentiated; CD27⁻CD28⁻CD45RA⁻CCR7⁻), terminally differentiated effector cells (TEMRA; CD27⁻CD28⁻CD45RA⁺CCR7⁻) and T_reg (CD4⁺CD25⁺FOXP3⁺CD127⁻) cells, and their expression of CD39, CD45RA, CD101 and CD129, were studied by flow cytometry in T1D and/or coeliac disease children or without any of these diseases (reference group). Children diagnosed with both T1D and coeliac disease showed a higher percentage of TEMRA CD4⁺ cells (P < 0·05), but lower percentages of both early and late effector memory CD8⁺ cells (P < 0·05) compared to references. Children with exclusively T1D had lower median fluorescence intensity (MFI) of forkhead box protein 3 (FoxP3) (P < 0·05) and also a lower percentage of CD39⁺ and CD45RA⁺ within the T_reg population (CD4⁺CD25⁺FOXP3⁺CD127⁻) (P < 0·05). Children with exclusively coeliac disease had a higher MFI of CD101 (P < 0·01), as well as a higher percentage of CD129⁺ (P < 0·05), in the CD4⁺CD25^hi lymphocyte population, compared to references. In conclusion, children with combined T1D and coeliac disease have a higher percentage of differentiated CD4⁺ cells compared to CD8⁺ cells. T1D children show signs of low CD39⁺/CD45RA⁺ T_reg cells that may indicate loss of suppressive function. Conversely, children with coeliac disease show signs of CD101⁺/CD129⁺ T_reg cells that may indicate suppressor activity.     

Human T helper type 1 dichotomy: origin,phenotype and biological activities

The great variety of pathogens present in the environment has obliged the immune system to evolve different mechanisms for tailored and maximally protective responses. Initially, two major types of CD4⁺ T helper (Th) effector cells were identified, and named as type 1 (Th1) and type 2 (Th2) cells because of the different cytokines they produce. More recently, a third type of CD4⁺ Th effectors has been identified and named as Th17 cells. Th17 cells, however, have been found to exhibit high plasticity because they rapidly shift into the Th1 phenotype in the inflammatory sites. Therefore, in these sites there is usually a dichotomous mixture of classic and non-classic (Th17-derived) Th1 cells. In humans, non-classic Th1 cells express CD161, as well as the retinoic acid orphan receptor C, interleukin-17 receptor E (IL-17RE), IL-1RI, CCR6, and IL-4-induced gene 1 and Tob-1, which are all virtually absent from classic Th1 cells. The possibility to distinguish between these two cell subsets may allow the opportunity to better establish their respective pathogenic role in different chronic inflammatory disorders. In this review, we discuss the different origin, the distinctive phenotypic features and the major biological activities of classic and non-classic Th1 cells.     

Distinct activation phenotype of a highly conserved novel HLA‐B57‐restricted epitope during dengue virus infection

Variation in the sequence of T‐cell epitopes between dengue virus (DENV) serotypes is believed to alter memory T‐cell responses during second heterologous infections. We identified a highly conserved, novel, HLA‐B57‐restricted epitope on the DENV NS1 protein. We predicted higher frequencies of B57‐NS1_26–34‐specific CD8⁺ T cells in peripheral blood mononuclear cells from individuals undergoing secondary rather than primary DENV infection. However, high tetramer‐positive T‐cell frequencies during acute infection were seen in only one of nine subjects with secondary infection. B57‐NS1_26–34‐specific and other DENV epitope‐specific CD8⁺ T cells, as well as total CD8⁺ T cells, expressed an activated phenotype (CD69⁺ and/or CD38⁺) during acute infection. In contrast, expression of CD71 was largely limited to DENV epitope‐specific CD8⁺ T cells. In vitro stimulation of cell lines indicated that CD71 expression was differentially sensitive to stimulation by homologous and heterologous variant peptides. CD71 may represent a useful marker of antigen‐specific T‐cell activation.     

Sustained CD8+ T-cell immune response to a novel immunodominant HLA-B*0702-associated epitope derived from an Epstein-Barr virus helicase-primase-associated protein

Generation of a peptide-based vaccine against persistent viral infections, such as Epstein-Barr virus (EBV), requires identification of immunodominant epitopes recognized by anti-viral cytotoxic T-cells. Using available computer algorithms, we have screened the entire translated EBV genome for potential HLA-B7-binding peptides. The binding to HLA-B7 of 18 selected peptides was assessed by competitive binding assays and was found to correlate with the computer-assigned scores, confirming the predictive value of these algorithms in selection of HLA-B7-associated peptides. Screening of the immune responses to these peptides by ELISpot assays identified a novel immunodominant epitope, termed LPRA, derived from an EBV helicase-primase-associated protein encoded by BBLF2/3. Peptide-specific cells constituted up to 0.8% LPRA-specific CD8+ T-cells in the matured anti-viral response. Cytotoxic and proliferative cytotoxic T lymphocytes (CTL) responses to the LPRA peptide were readily demonstrated ex vivo. In addition, mutational studies of this epitope demonstrated a highly specific recognition by LPRA-specific CD8+ T-cells. Taken together, our data suggest that the novel lytic-phase HLA-B7-associated epitope contains essential features required of a component in an EBV peptide-based vaccine.