Single T cell receptor-mediated recognition of an identical HIV-derived peptide presented by multiple HLA class I molecules

CD8+ T-cell responses towards conserved influenza B virus epitopes across anatomical sites and age

Influenza B viruses (IBVs) cause substantive morbidity and mortality, and yet immunity towards IBVs remains understudied. CD8+ T-cells provide broadly cross-reactive immunity and alleviate disease severity by recognizing conserved epitopes. Despite the IBV burden, only 18 IBV-specific T-cell epitopes restricted by 5 HLAs have been identified currently. A broader array of conserved IBV T-cell epitopes is needed to develop effective cross-reactive T-cell based IBV vaccines. Here we identify 9 highly conserved IBV CD8+ T-cell epitopes restricted to HLA-B*07:02, HLA-B*08:01 and HLA-B*35:01. Memory IBV-specific tetramer+CD8+ T-cells are present within blood and tissues. Frequencies of IBV-specific CD8+ T-cells decline with age, but maintain a central memory phenotype. HLA-B*07:02 and HLA-B*08:01-restricted NP30-38 epitope-specific T-cells have distinct T-cell receptor repertoires. We provide structural basis for the IBV HLA-B*07:02-restricted NS1196-206 (11-mer) and HLA-B*07:02-restricted NP30-38 epitope presentation. Our study increases the number of IBV CD8+ T-cell epitopes, and defines IBV-specific CD8+ T-cells at cellular and molecular levels, across tissues and age.

Determination of a T cell receptor of potent CD8+ T cells against simian immunodeficiency virus infection in Burmese rhesus macaques

Cumulative studies on human immunodeficiency virus (HIV)-infected individuals have shown association of major histocompatibility complex class I (MHC-I) polymorphisms with lower viral load and delayed AIDS progression, suggesting that HIV replication can be controlled by potent CD8⁺ T-cell responses. We have previously established an AIDS model of simian immunodeficiency virus (SIV) infection in Burmese rhesus macaques and found a potent CD8⁺ T cell targeting the Mamu-A1*065:01-restricted Gag_241-249 epitope, which is located in a region corresponding to the HIV Gag_240-249 TW10 epitope restricted by a protective MHC-I allele, HLA-B*57. In the present study, we determined a T cell receptor (TCR) of this Gag_241-249 epitope-specific CD8⁺ T cell. cDNA clones encoding TCR-α and TCR-β chains were obtained from a Gag_241-249-specific CD8⁺ T-cell clone. Coexpression of these TCR-α and TCR-β cDNAs resulted in reconstitution of a functional TCR specifically detected by Gag_241-249 epitope-Mamu-A1*065:01 tetramer. Two of three previously-reported CD8⁺ T-cell escape mutations reduced binding affinity of Gag_241-249 peptide to Mamu-A1*065:01 but the remaining one not. This is consistent with the data obtained by molecular modeling of the epitope-MHC-I complex and TCR. These results would contribute to understanding how viral CD8⁺ T-cell escape mutations are selected under structural constraint of viral proteins.

Increased HIV-1 superinfection risk in carriers of specific human leukocyte antigen alleles

OBJECTIVE

The aim of this study was to characterize the demographic, behavioural, clinical and immunogenetic determinants of HIV-1 superinfection in a high-risk cohort of MSM.

DESIGN

A retrospective cohort study of prospectively followed MSM.

METHODS

Ninety-eight MSM with acute or early HIV-1 monoinfection were followed for a median of 15.6 months. Demographic and human leukocyte antigen (HLA) genotype data were collected at enrolment. Sexual behaviour, clinical and the infection status (monoinfection or superinfection) data were recorded at each visit (at enrolment and thereafter at a median of 4.2-month intervals). HIV-1 superinfection risk was determined by Cox regression and Kaplan-Meier survival analysis.

RESULTS

Ten individuals (10.2%) had superinfection during follow-up. Cox regression did not show significantly increased superinfection risk for individuals with an increased amount of condomless anal intercourse, lower CD4 T-cell count or higher viral load, but higher number of sexual contacts demonstrated a trend towards significance [hazard ratio, 4.74; 95% confidence interval (95% CI), 0.87-25.97; P = 0.073]. HLA-A*29 (hazard ratio, 4.10; 95% CI, 0.88-14.76; P = 0.069), HLA-B*35 (hazard ratio, 4.64; 95% CI, 1.33-18.17; P = 0.017), HLA-C*04 (hazard ratio, 5.30; 95% CI, 1.51-20.77; P = 0.010), HLA-C*16 (hazard ratio, 4.05; 95% CI, 0.87-14.62; P = 0.071), HLA-DRB1*07 (hazard ratio, 3.29; 95% CI, 0.94-12.90; P = 0.062) and HLA-DRB1*08 (hazard ratio, 15.37; 95% CI, 2.11-79.80; P = 0.011) were associated with an increased risk of superinfection at α = 0.10, whereas HLA-DRB1*11 was associated with decreased superinfection risk (hazard ratio, 0.13; 95% CI, 0.00-1.03; P = 0.054).

CONCLUSION

HLA genes may, in part, elucidate the genetic basis of differential superinfection risk, and provide important information for the development of efficient prevention and treatment strategies of HIV-1 superinfection.

Dynamic Perturbations of the T-Cell Receptor Repertoire in Chronic HIV Infection and following Antiretroviral Therapy

HIV infection profoundly affects many parameters of the immune system and ultimately leads to AIDS, yet which factors are most important for determining resistance, pathology, and response to antiretroviral treatment – and how best to monitor them – remain unclear. We develop a quantitative high-throughput sequencing pipeline to characterize the TCR repertoires of HIV-infected individuals before and after antiretroviral therapy, working from small, unfractionated samples of peripheral blood. This reveals the TCR repertoires of HIV⁺ individuals to be highly perturbed, with considerably reduced diversity as a small proportion of sequences are highly overrepresented. HIV also causes specific qualitative changes to the repertoire including an altered distribution of V gene usage, depletion of public TCR sequences, and disruption of TCR networks. Short-term antiretroviral therapy has little impact on most of the global damage to repertoire structure, but is accompanied by rapid changes in the abundance of many individual TCR sequences, decreases in abundance of the most common sequences, and decreases in the majority of HIV-associated CDR3 sequences. Thus, high-throughput repertoire sequencing of small blood samples that are easy to take, store, and process can shed light on various aspects of the T-cell immune compartment and stands to offer insights into patient stratification and immune reconstitution.

Clonotypically similar hybrid αβ T cell receptors can exhibit markedly different surface expression, antigen specificity and cross-reactivity

Emerging data indicate that particular major histocompatibility complex (MHC)‐bound antigenic peptides can be recognized by identical or near‐identical αβ T cell receptors (TCRs) in different individuals. To establish the functional relevance of this phenomenon, we artificially paired α and β chains from closely related TCRs specific for the human leucocyte antigen (HLA)‐B*35:01‐restricted HIV‐1 negative regulatory factor (Nef)‐derived epitope VY8 (VPLRPMTY, residues 74–81). Several hybrid TCRs generated in this manner failed to express at the cell surface, despite near homology with naturally isolated αβ chain combinations. Moreover, a substantial proportion of those αβ TCRs that did express lost specificity for the index VY8 peptide sequence. One such hybrid αβ pair gained neo‐variant specificity in the context of the VY8 backbone. Collectively, these data show that clonotypically similar TCRs can display profound differences in surface expression, antigen specificity and cross‐reactivity with potential relevance for the control of mutable viruses.

T cells recognizing a 11mer influenza peptide complexed to H-2D(b) show promiscuity for peptide length

T-cell repertoire is selected according to self peptide-MHC (major histocompatibility complex) complexes in the thymus. Although most peripheral T cells recognize specific pathogen-derived peptides complexed to self-MHC exclusively, some possess cross-reactivity to other self or foreign peptides presented by self-MHC molecules; a phenomenon often termed T-cell receptor (TCR) promiscuity or degeneracy. TCR promiscuity has been attributed to various autoimmune conditions. On the other hand, it is considered a mechanism for a relatively limited TCR repertoire to deal with a potentially much larger antigenic peptide repertoire. Such property has also been utilized to bypass self-tolerance for cancer vaccine development. Although many studies explored such degeneracy for peptide of the same length, few studies reported such properties for peptides of different length. In this study, we finely characterized the CD8(+) T-cell response specific for a 11mer peptide derived from influenza A viral polymerase basic protein 2. The short-term T-cell line, despite possessing highly biased TCR, was able to react with multiple peptides of different length sharing the same core sequence. Out data clearly showed the importance of detailed and quantitative assessments for such T-cell specificity. Our data also emphasize the importance of biochemical demonstration of the naturally presented minimal peptide.

Selection of TI8-8V mutant associated with long-term control of HIV-1 by cross-reactive HLA-B*51:01-restricted cytotoxic T cells

Elite controllers of HIV-1-infected HLA-B*51:01(+) hemophiliacs, who remain disease free and have a very low plasma viral load for >30 y, had the 8V mutation at an immunodominant Pol283-8 (TI8) epitope, whereas the 8T mutant was predominantly selected in other HIV-1-infected HLA-B*51:01(+) hemophiliacs, suggesting an important role of the 8V mutant selection in long-term control of HIV-1. However, the mechanism of this selection and the long-term control in these elite controllers remains unknown. In this study, we investigated the mechanism of the 8V mutant selection in these controllers. TI8-specific CTLs from these individuals evenly recognized both TI8 peptide-pulsed and TI8-8V peptide-pulsed cells and effectively suppressed replication of wild-type (WT) and the 8V viruses. However, the results of a competitive viral suppression assay demonstrated that CTLs from the individual who had WT virus could discriminate WT virus from the 8V virus, whereas those from the individuals who had the 8V virus evenly recognized both viruses. The former CTLs carried TCRs with weaker affinity for the HLA-B*51:01-TI8-8V molecule than for the HLA-B*51:01-TI-8 one, whereas the latter ones carried TCRs with similar affinity for both molecules. The reconstruction of the TCRs from these CTLs in TCR-deficient cells confirmed the different recognition of the TCRs for these epitopes. The present study showed that the 8V mutant virus could be selected by cross-reactive CTLs carrying TCR that could discriminate a small difference between the two molecules. The selection of the 8V mutant and elicitation of these two cross-reactive CTLs may contribute to the long-term control of HIV-1.

Cross-reactivity analysis of T cell receptors specific for overlapping HIV-1 Nef epitopes of different lengths

Overlapping peptides of different lengths from a certain immunodominant region can be presented by the same HLA class I molecule and elicit different T cell responses. However, how peptide-length specificity of antigen-specific CD8(+) T lymphocytes influence cross-reactivity profiles of these cells remains elusive. This question is particularly important in the face of highly variable pathogens such as HIV-1. Here, we examined this problem by using HLA-B*35:01-restricted CD8(+) T lymphocytes specific for Nef epitopes, i.e., RY11 (RPQVPLRPMTY), VY8 (VPLRPMTY), and RM9 (RPQVPLRPM), in which VY8 and RM9 were contained entirely within RY11, in combination with a T cell receptor (TCR) reconstruction system as well as HLA-B35 tetramers and a set of a single-variant peptide library. The TCR reactivity toward the peptide-length variants was classified into three types: mutually exclusive specificity toward (1) RY11 or (2) VY8 and (3) cross-recognition toward RM9 and RY11. TCR cross-reactivity toward variant peptides was similar within the same peptide-length reactivity type but was markedly different between the types. Thus, TCRs showing similar peptide-length reactivity have shared peptide recognition footprints and thereby similar weakness to antigenic variations, providing us with further insight into the antiviral vaccine design.

CD8(+) T cell cross-reactivity profiles and HIV-1 immune escape towards an HLA-B35-restricted immunodominant Nef epitope

Antigen cross-reactivity is an inbuilt feature of the T cell compartment. However, little is known about the flexibility of T cell recognition in the context of genetically variable pathogens such as HIV-1. In this study, we used a combinatorial library containing 24 billion octamer peptides to characterize the cross-reactivity profiles of CD8⁺ T cells specific for the immunodominant HIV-1 subtype B Nef epitope VY8 (VPLRPMTY) presented by HLA-B^*35∶01. In conjunction, we examined naturally occurring antigenic variations within the VY8 epitope. Sequence analysis of plasma viral RNA isolated from 336 HIV-1-infected individuals revealed variability at position (P) 3 and P8 of VY8; Phe at P8, but not Val at P3, was identified as an HLA-B^*35∶01-associated polymorphism. VY8-specific T cells generated from several different HIV-1-infected patients showed unique and clonotype-dependent cross-reactivity footprints. Nonetheless, all T cells recognized both the index Leu and mutant Val at P3 equally well. In contrast, competitive titration assays revealed that the Tyr to Phe substitution at P8 reduced T cell recognition by 50–130 fold despite intact peptide binding to HLA-B^*35∶01. These findings explain the preferential selection of Phe at the C-terminus of VY8 in HLA-B^*35∶01⁺ individuals and demonstrate that HIV-1 can exploit the limitations of T cell recognition in vivo.

Cross-allele cytotoxic T lymphocyte responses against 2009 pandemic H1N1 influenza A virus among HLA-A24 and HLA-A3 supertype-positive individuals

Lack of a universal vaccine against all serotypes of influenza A viruses and recent progress on T cell-related vaccines against influenza A virus illuminate the important role of human leukocyte antigen (HLA)-restricted cytotoxic T lymphocytes (CTLs) in anti-influenza virus immunity. However, the diverse HLA alleles among humans complicate virus-specific cellular immunity research, and elucidation of cross-HLA allele T cell responses to influenza virus specificity requires further detailed work. An ideal CTL epitope-based vaccine would cover a broad spectrum of epitope antigens presented by most, if not all, of the HLAs. Here, we evaluated the 2009 pandemic influenza A (H1N1) virus-specific T cell responses among the HLA-A24(+) population using a rationally designed peptide pool during the 2009 pandemic. Unexpectedly, cross-HLA allele T cell responses against the influenza A virus peptides were detected among both HLA-A11(+) and HLA-A24(+) donors. Furthermore, we found cross-responses in the entire HLA-A3 supertype population (including HLA-A11, -A31, -A33, and -A30). The cross-allele antigenic peptides within the peptide pool were identified and characterized, and the crystal structures of the major histocompatibility complex (MHC)-peptide complexes were determined. The subsequent HLA-A24-defined cross-allele peptides recognized by the HLA-A11(+) population were shown to mildly bind to the HLA-A*1101 molecule. Together with the structural models, these results partially explain the cross-allele responses. Our findings elucidate the promiscuity of the cross-allele T cell responses against influenza A viruses and are beneficial for the development of a T cell epitope-based vaccine applied in a broader population.

High-functional-avidity cytotoxic T lymphocyte responses to HLA-B-restricted Gag-derived epitopes associated with relative HIV control

Virus-specific cytotoxic T lymphocytes (CTL) with high levels of functional avidity have been associated with viral clearance in hepatitis C virus infection and with enhanced antiviral protective immunity in animal models. However, the role of functional avidity as a determinant of HIV-specific CTL efficacy remains to be assessed. Here we measured the functional avidities of HIV-specific CTL responses targeting 20 different, optimally defined CTL epitopes restricted by 13 different HLA class I alleles in a cohort comprising 44 HIV controllers and 68 HIV noncontrollers. Responses restricted by HLA-B alleles and responses targeting epitopes located in HIV Gag exhibited significantly higher functional avidities than responses restricted by HLA-A or HLA-C molecules (P = 0.0003) or responses targeting epitopes outside Gag (P < 0.0001). The functional avidities of Gag-specific and HLA-B-restricted responses were higher in HIV controllers than in noncontrollers (P = 0.014 and P = 0.018) and were not restored in HIV noncontrollers initiating antiretroviral therapy. T-cell receptor (TCR) analyses revealed narrower TCR repertoires in higher-avidity CTL populations, which were dominated by public TCR sequences in HIV controllers. Together, these data link the presence of high-avidity Gag-specific and HLA-B-restricted CTL responses with viral suppression in vivo and provide new insights into the immune parameters that mediate spontaneous control of HIV infection.

HLA class I allele promiscuity revisited

The peptide repertoire presented on human leukocyte antigen (HLA) class I molecules is largely determined by the structure of the peptide binding groove. It is expected that the molecules having similar grooves (i.e., belonging to the same supertype) might present similar/overlapping peptides. However, the extent of promiscuity among HLA class I ligands remains controversial: while in many studies T cell responses are detected against epitopes presented by alternative molecules across HLA class I supertypes and loci, peptide elution studies report minute overlaps between the peptide repertoires of even related HLA molecules. To get more insight into the promiscuous peptide binding by HLA molecules, we analyzed the HLA peptide binding data from the large epitope repository, Immune Epitope Database (IEDB), and further performed in silico analysis to estimate the promiscuity at the population level. Both analyses suggest that an unexpectedly large fraction of HLA ligands (>50%) bind two or more HLA molecules, often across supertype or even loci. These results suggest that different HLA class I molecules can nevertheless present largely overlapping peptide sets, and that “functional” HLA polymorphism on individual and population level is probably much lower than previously anticipated.

Impact of intrinsic cooperative thermodynamics of peptide-MHC complexes on antiviral activity of HIV-specific CTL

The antiviral activity of HIV-specific CTL is not equally potent but rather is dependent on their specificity. But what characteristic of targeted peptides influences CTL antiviral activity remains elusive. We addressed this issue based on HLA-B35-restricted CTLs specific for two overlapping immunodominant Nef epitopes, VY8 (VPLRPMTY) and RY11 (RPQVPLRPMTY). VY8-specific CTLs were more potently cytotoxic toward HIV-infected primary CD4(+) cells than RY11-specific CTLs. Reconstruction of their TCR revealed no substantial difference in their functional avidity toward cognate Ags. Instead, the decay analysis of the peptide-MHC complex (pMHC) revealed that the VY8/HLA-B35 complex could maintain its capacity to sensitize T cells much longer than its RY11 counterpart. Corroboratively, the introduction of a mutation in the epitopes that substantially delayed pMHC decay rendered Nef-expressing target cells more susceptible to CTL killing. Moreover, by using differential scanning calorimetry and circular dichroism analyses, we found that the susceptible pMHC ligands for CTL killing showed interdependent and cooperative, rather than separate or sequential, transitions within their heterotrimer components under the thermally induced unfolding process. Collectively, our results highlight the significant effects of intrinsic peptide factors that support cooperative thermodynamics within pMHC on the efficient CTL killing of HIV-infected cells, thus providing us better insight into vaccine design.

Extensive HLA class I allele promiscuity among viral CTL epitopes

Promiscuous binding of T helper epitopes to MHC class II molecules has been well established, but few examples of promiscuous class I-restricted epitopes exist. To address the extent of promiscuity of HLA class I peptides, responses to 242 well-defined viral epitopes were tested in 100 subjects regardless of the individuals' HLA type. Surprisingly, half of all detected responses were seen in the absence of the originally reported restricting HLA class I allele, and only 3% of epitopes were recognized exclusively in the presence of their original allele. Functional assays confirmed the frequent recognition of HLA class I-restricted T cell epitopes on several alternative alleles across HLA class I supertypes and encoded on different class I loci. These data have significant implications for the understanding of MHC class I-restricted antigen presentation and vaccine development.

Allorestricted T cells with specificity for the FMNL1-derived peptide PP2 have potent antitumor activity against hematologic and other malignancies

Cell-based immunotherapy in settings of allogeneic stem cell transplantation or donor leukocyte infusion has curative potential, especially in hematologic malignancies. However, this approach is severely restricted due to graft-versus-host disease (GvHD). This limitation may be overcome if target antigens are molecularly defined and effector cells are specifically selected. We chose formin-related protein in leukocytes 1 (FMNL1) as a target antigen after intensive investigation of its expression profile at the mRNA and protein levels. Here, we confirm restricted expression in peripheral blood mononuclear cells (PBMCs) from healthy donors but also observe overexpression in different leukemias and aberrant expression in transformed cell lines derived from solid tumors. We isolated allorestricted T-cell clones expressing a single defined TCR recognizing a particular HLA-A2–presented peptide derived from FMNL1. This T-cell clone showed potent antitumor activity against lymphoma and renal cell carcinoma cell lines, Epstein-Barr virus (EBV)–transformed B cells, and primary tumor samples derived from patients with chronic lymphocytic leukemia (CLL), whereas nontransformed cells with the exception of activated B cells were only marginally recognized. Allorestricted TCRs with specificity for naturally presented FMNL1-derived epitopes may represent promising reagents for the development of adoptive therapies in lymphoma and other malignant diseases.

Altering effects of antigenic variations in HIV-1 on antiviral effectiveness of HIV-specific CTLs

The mutational escape of HIV-1 from established CTL responses is becoming evident. However, it is not yet clear whether antigenic variations of HIV-1 may have an additional effect on the differential antiviral effectiveness of HIV-specific CTLs. Herein, we characterized HIV-specific CTL responses toward Pol, Env, and Nef optimal epitopes presented by HLA-B*35 during a chronic phase of HIV-1 infection. We found CTL escape variants within Pol and Nef epitopes that affected recognition by TCRs, although there was no mutation within the Env epitope. An analysis of peptide-HLA tetrameric complexes revealed that CD8 T cells exclusively specific for the Nef variant were generated following domination by the variant viruses. The variant-specific cells were capable of killing target cells and producing antiviral cytokines but showed impaired Ag-specific proliferation ex vivo, whereas wild-type specific cells had potent activities. Moreover, clonotypic CD8 T cells specific for the Pol variant showed diminished proliferation, whereas Env-specific ones had no functional heterogeneity. Taken together, our data indicate that antigenic variations that abolished TCR recognition not only resulted in escape from established CTL responses but also eventually generated another subset of variant-specific CTLs having decreased antiviral activity, causing an additional negative effect on antiviral immune responses during a chronic HIV infection.

Increased level and longevity of protective immune responses induced by DNA vaccine expressing the HIV-1 Env glycoprotein when combined with IL-21 and IL-15 gene delivery

We investigated the ability of a plasmid-derived IL-21 delivered alone or in combination with the IL-15 gene to regulate immune responses to the HIV-1 envelope (Env) glycoprotein induced by DNA vaccination. Mice were injected with the gp140DeltaCFI(HXB2/89.6) vector expressing a modified Env glycoprotein with C-terminal mutations intended to mimic a fusion intermediate, in which the most divergent region encoding the variable V1, V2, and V3 domains of CXCR4-tropic HxB2 virus was replaced with the dual-tropic 89.6 viral strain. Using a recombinant vaccinia virus expressing 89.6 Env glycoprotein (vBD3) in a mouse challenge model, we observed that IL-21 plasmid produced sustained resistance to viral transmission when injected 5 days after DNA vaccination. Moreover, IL-21 in a synergistic manner with IL-15 expression vector augmented the vaccine-induced recall responses to the vBD3 challenge compared with those elicited by immunization in the presence of either cytokine alone. The synergistic combination of IL-21 and IL-15 plasmids promoted expansion of CD8+CD127+ memory T cell pools specific for a subdominant HLA-A2-restricted Env(121-129) epitope (KLTPLCVTL). Our results also show that coimmunization with IL-21 and IL-15 plasmid combination resulted in enhanced CD8+ T cell function that was partially independent of CD4+ T cell help in mediating protection against vBD3 challenge. Furthermore, the use of IL-21 and IL-15 genes was able to increase Ab-dependent cellular cytotoxicity and complement-dependent lysis of Env-expressing target cells through augmentation of Env-specific IgG Ab levels. These data indicate that the plasmid-delivered IL-21 and IL-15 can increase the magnitude of the response to DNA vaccines.

T cell receptor cross-recognition of an HIV-1 CD8+ T cell epitope presented by closely related alleles from the HLA-A3 superfamily

HLA-A3 and -A11 share similar peptide-binding motifs, however, it is unclear if promiscuous epitope presentation by HLA-A3 or HLA-A11 is associated with promiscuous TCR recognition. Here, we show that despite widespread cross-presentation of identical HIV-1 peptides in HIV-1-infected individuals expressing HLA-A3 or HLA-A11, peptides presented by HLA-A3 or HLA-A11 commonly exhibited clear immune distinctiveness with exclusive TCR recognition. Yet, using HLA-A3 and HLA-A11 tetramers for testing T cell cross-recognition of the HIV-1 Nef QK10 epitope, we observed in two study persons that specific CD8+ T cell populations were able to cross-recognize this peptide in the context of both HLA-A3 and HLA-A11. This cross-recognition was mediated by single cross-reactive TCRs, as shown by TCR sequencing in conjunction with TCR Vbeta chain immunostaining. In each cross-reactive cell population, multiple TCR beta chain variants were detected in the presence of only one TCR alpha chain variant. Thus, despite distinct TCR recognition of HLA-A3 or HLA-A11 presented HIV-1 peptides in the vast majority of cases, specific TCRs can cross-recognize their antigen in the context of both HLA-A3 and HLA-A11.

Reconstitution of anti-HIV effector functions of primary human CD8 T lymphocytes by transfer of HIV-specific alphabeta TCR genes

We redirected the antigen specificity of primary human CD8 T cells by retrovirus-mediated transduction of genes encoding alphabeta TCR specific to HIV-1 Pol protein. A large polyclonal population of TCR-transduced CD8 T cells showed substantial cytotoxic and cytokine production activities toward target cells either pulsed with the peptide or infected with HIV-1, and their functional activities were comparable to those of the parental CTL clone. Peptide fine-specificity and promiscuous recognition of HLA class I supertypes of the parental CTL clone were also preserved in the TCR-transduced cells. There were no signs of allogeneic responses in these cells, although hybrid TCR dimers consisting of transduced TCR and endogenous TCR were suspected to have been formed in these cells, as the effect of transgene expression on the surface expression of the desired TCR was limited. Moreover, the TCR-transduced cells showed potent inhibitory activity against HIV-1 replication in vitro, although the differential surface expression of the desired TCR resulted in differential functional avidity of individual TCR-transduced cells toward the peptide-pulsed target cells. These data suggest that the reconstitution of HIV-specific immunoreactive T cells engineered by genetic transfer of HIV-specific TCR is a potential alternative to immunotherapeutic applications against HIV infections.

Functionally impaired HIV-specific CD8 T cells show high affinity TCR-ligand interactions

We eventually isolated two different clonotypic CD8 T cell subsets recognizing an HIV Pol-derived epitope peptide (IPLTEEAEL) in association with HLA-B35 from a chronic HIV-infected patient. By kinetic analysis experiments, the subsets showed a >3-fold difference in half-lives for the HLA tetramer in complex with the Pol peptide. In functional assays in vitro and ex vivo, both subsets showed substantial functional avidity toward peptide-loaded cells. However, the high affinity subset did not show cytolytic activity, cytokine production, or proliferation activity toward HIV-infected cells, whereas the moderate affinity one showed potent activities. Furthermore, using ectopic expression of each of the TCR genes into primary human CD8 T cells, the CD8 T cells transduced with the high affinity TCR showed greater binding activity toward the tetramer and impaired cytotoxic activity toward HIV-infected cells, corroborating the results obtained with parental CD8 T cells. Taken together, these data indicate that impaired responsiveness of T cells toward HIV-infected cells can occur at the level of TCR-ligand interactions, providing us further insight into the immune evasion mechanisms by HIV.

Dual, HLA-B27 subtype-dependent conformation of a self-peptide

The products of the human leukocyte antigen subtypes HLA-B*2705 and HLA-B*2709 differ only in residue 116 (Asp vs. His) within the peptide binding groove but are differentially associated with the autoimmune disease ankylosing spondylitis (AS); HLA-B*2705 occurs in AS-patients, whereas HLA-B*2709 does not. The subtypes also generate differential T cell repertoires as exemplified by distinct T cell responses against the self-peptide pVIPR (RRKWRRWHL). The crystal structures described here show that pVIPR binds in an unprecedented dual conformation only to HLA-B*2705 molecules. In one binding mode, peptide pArg5 forms a salt bridge to Asp116, connected with drastically different interactions between peptide and heavy chain, contrasting with the second, conventional conformation, which is exclusively found in the case of B*2709. These subtype-dependent differences in pVIPR binding link the emergence of dissimilar T cell repertoires in individuals with HLA-B*2705 or HLA-B*2709 to the buried Asp116/His116 polymorphism and provide novel insights into peptide presentation by major histocompatibility antigens.

Requirement for Both H-2Db and H-2Kd for the Induction of Diabetes by the Promiscuous CD8+ T Cell Clonotype AI4

The NOD mouse is a model for autoimmune type 1 diabetes in humans. CD8(+) T cells are essential for the destruction of the insulin-producing pancreatic beta cells characterizing this disease. AI4 is a pathogenic CD8(+) T cell clone, isolated from the islets of a 5-wk-old female NOD mouse, which is capable of mediating overt diabetes in the absence of CD4(+) T cell help. Recent studies using MHC-congenic NOD mice revealed marked promiscuity of the AI4 TCR, as the selection of this clonotype can be influenced by multiple MHC molecules, including some class II variants. The present work was designed, in part, to determine whether similar promiscuity also characterizes the effector function of mature AI4 CTL. Using splenocyte and bone marrow disease transfer models and in vitro islet-killing assays, we report that efficient recognition and destruction of beta cells by AI4 requires the beta cells to simultaneously express both H-2D(b) and H-2K(d) class I MHC molecules. The ability of the AI4 TCR to interact with both H-2D(b) and H-2K(d) was confirmed using recombinant peptide libraries. This approach also allowed us to define a mimotope peptide recognized by AI4 in an H-2D(b)-restricted manner. Using ELISPOT and mimotope/H-2D(b) tetramer analyses, we demonstrate for the first time that AI4 represents a readily detectable T cell population in the islet infiltrates of prediabetic NOD mice. Our identification of a ligand for AI4-like T cells will facilitate further characterization and manipulation of this pathogenic and promiscuous T cell population.