Injections of Clostridium botulinum neurotoxin A may cause thyroid complications in predisposed persons based on molecular mimicry with thyroid autoantigens

A woman with Hashimoto's thyroiditis, under replacement L-T4, repeatedly experienced, over a 10-year period, elevations of serum TSH after eyelid injections of Clostridium botulinum neurotoxin A (Btx). We hypothesized a link between Btx injections and TSH elevations via molecular mimicry, and aimed to verify our hypothesis. Using an in silico approach, we searched first for amino acid sequence homology between Btx and thyroid autoantigens, and next for HLA binding motifs within homologous segments. We found that (i) Btx and thyroid autoantigens share amino acid sequence homology; (ii) some homologous regions contain epitopes of both Btx and thyroid autoantigens; (iii) some of such regions contain HLA-DR3 and/or HLA-DR7 binding motifs, which predominate over other HLA-DRs. This is relevant because the patient's HLA-DR haplotype was DR3/DR7. In conclusion, clinical and bioinformatics data suggest a possible pathogenetic link between Btx and autoimmune thyroid diseases. Considering the wide and increasing medical and dermocosmetic use of Btx, and the frequently subclinical course of autoimmune thyroid diseases, we think that thyroid "complications" may pass frequently undetected in Btx-treated persons.

The role of glutamic or aspartic acid in position four of the epitope binding motif and thyrotropin receptor-extracellular domain epitope selection in Graves' disease

CONTEXT

Development of Graves' disease (GD) is related to HLA-DRB1*0301 (DR3),and more specifically to arginine at position 74 of the DRB1 molecule. The extracellular domain (ECD) of human TSH receptor (hTSH-R) contains the target antigen.

OBJECTIVE AND DESIGN

We analyzed the relation between hTSH-R-ECD peptides and DR molecules to determine whether aspartic acid (D) or glutamic acid (E) at position four in the binding motif influenced selection of functional epitopes.

RESULTS

Peptide epitopes from TSH-R-ECD with D or E in position four (D/E+) had higher affinity for binding to DR3 than peptides without D/E (D/E-) (IC(50) 29.3 vs. 61.4, P = 0.0024). HLA-DR7, negatively correlated with GD, and DRB1*0302 (HLA-DR18), not associated with GD, had different profiles of epitope binding. Toxic GD patients who are DR3+ had higher responses to D/E+ peptides than D/E- peptides (stimulation index 1.42 vs. 1.22, P = 0.028). All DR3+ GD patients (toxic + euthyroid) had higher responses, with borderline significance (Sl; 1.32 vs. 1.18, P = 0.051). Splenocytes of DR3 transgenic mice immunized to TSH-R-ECD responded to D/E+ peptides more than D/E- peptides (stimulation index 1.95 vs. 1.69, P = 0.036). Seven of nine hTSH-R-ECD peptide epitopes reported to be reactive with GD patients' peripheral blood mononuclear cells contain binding motifs with D/E at position four.

CONCLUSIONS

TSH-R-ECD epitopes with D/E in position four of the binding motif bind more strongly to DRB1*0301 than epitopes that are D/E- and are more stimulatory to GD patients' peripheral blood mononuclear cells and to splenocytes from mice immunized to hTSH-R. These epitopes appear important in immunogenicity to TSH-R due to their favored binding to HLA-DR3, thus increasing presentation to T cells.

Shared MHC class II-dependent melanoma ribosomal protein L8 identified by phage display

Antigens recognized by T helper (Th) cells in the context of MHC class II molecules have vaccine potential against cancer and infectious agents. We have described previously a melanoma patient's HLA-DR7-restricted Th cell clone recognizing an antigen, which is shared among melanoma and glioma cells derived from various patients. Here, this antigen was cloned using a novel antigen phage display approach. The antigen was identified as the ribosomal protein L8 (RPL8). A peptide of RPL8 significantly stimulated proliferation and/or cytokine expression of the Th cell clone and lymphocytes in four of nine HLA-DR7(+) melanoma patients but not in healthy volunteers. The RPL8 antigen may represent a relevant vaccine target for patients with melanoma, glioma, and breast carcinoma whose tumors express this protein.

Modulation of allergic response by gene-environment interaction: olive pollen allergy

This article summarizes the most important advances of recent years in the field of gene-environment interaction in allergic response. It specifically examines sensitization to olive pollen as an example of one of the main causes of allergic disease in the Mediterranean area. The presence of at least 20 proteins with allergic activity has been demonstrated in olive pollen, and 10 of these have been characterized (Ole e 1 to Ole e 10). Ole e 1, which is considered to be the majority allergen (causing sensitization in more than 70% of patients), has been the subject of many studies looking for risk factors and ways to protect against sensitization. Markers of the major histocompatibility complex and other genetic loci associated with the allergic response have been analyzed using population-based, family-based, and functional approaches, which have revealed the involvement of genetic regulation in this type of response. Furthermore, evaluation of environmental factors and their relationship with genetic factors is essential when attempting to understand this type of disease. In this review, we provide examples of how exposure to high doses of olive pollen allergen in a specific genetic context can trigger different allergic conditions (from asthma to nonresponse). We stress the importance of evaluating these factors in order to modulate this response correctly.

[Influence of genetic and phenotypical factors on the efficiency of the vaccination of young children against diphtheria and measles]

The child's sex was shown to influence the character of antibody formation only after immunization against diphtheria with live measles vaccine: girls exhibited stronger reaction to vaccination than boys. Children of different gender were found to have characteristic HLA DR markers of humoral immune response to diphtheria toxoid and measles vaccine. HLA DR7 proved to be the marker of low production of antibodies to diphtheria toxoid and measles vaccine in boys.

Phenotype and function of monocyte derived dendritic cells in chronic hepatitis B virus infection

The antiviral T cell failure of patients with chronic hepatitis B virus (HBV) infection was suggested to be caused by a T cell stimulation defect of dendritic cells (DC). To address this hypothesis, monocyte derived DC (MDDC) of patients with chronic or resolved acute HBV infection and healthy controls were studied phenotypically by FACS analyses and functionally by mixed lymphocyte reaction, ELISA, ELISpot and proliferation assays of MDDC cultures or co-cultures with an allogeneic HBc-specific Th cell clone. HBV infection of MDDC was studied by quantitative PCR. MDDC from HBV patients seemed to be infected by the HBV, showed a reduced surface expression of HLA DR and CD40 and exhibited a reduced secretion of IL12p70 in response to HBcAg but not to LPS, as compared to control MDDC. However, after cytokine induced maturation, MDDC from HBV patients revealed an unimpaired phenotype. Moreover, the T cell stimulatory capacity of HBV-DC was intact, since (i) the induction of allospecific proliferative and IFN-gamma responses was not affected in HBV-MDDC, and (ii) HLA DR7 restricted stimulation of an allogeneic HBc-specific Th cell clone was not impaired by HBV-MDDC compared to control MDDC. It is hypothesized that HBV infection of DC might lead to minor phenotypic and functional alterations without significantly affecting their antiviral Th cell stimulatory capacity.

A CD4+, HLA-DR7-restricted T-helper lymphocyte clone recognizes an antigen shared by human malignant melanoma and glioma

CD4(+) Th cells that are restricted by MHC class II molecules play an important role in the induction of antitumor immune responses. We have established a stable CD4(+) Th cell clone (Th35-1A) from the PBMCs of a patient with primary cutaneous melanoma. The Th cell clone is noncytolytic and proliferates specifically in the presence of irradiated autologous melanoma cells or autologous EBV-transformed B cells pulsed with melanoma tumor cell lysates. Th35-1A produces IFN-gamma (a Th1-type cytokine) after autologous tumor cell stimulation, and its proliferative reactivity is HLA class II-restricted. Th cells showed helper activity for PWM responses of PBMCs. Using a panel of HLA class II-matched and unmatched EBV-B cells as APCs and allogeneic melanoma tumor cell lysate as stimulant, DR7 was delineated as the HLA class II restriction element used by the Th cell clone. In agreement with these results, transfection of an allogeneic melanoma cell line with HLA-DR7 isolated from autologous EBV-B cells rendered the cell line stimulatory for Th35-1A cells. Specificity studies using autologous EBV-B cells (EBV-B35) pulsed with a panel of allogeneic tumor cell lysates of various tissue origins indicated that the Th cell clone recognizes an antigen shared by melanoma and glioma cells. The availability of the Th cell clone may lead to the development of new therapies against melanoma, using adoptive Th cell transfer and/or active immunization with a shared Th cell antigen.

Donor-derived b2a2-specific T cells for immunotherapy of patients with chronic myeloid leukemia

The BCR-ABL fusion proteins, b2a2 and b3a2, are potential targets for a beneficial graft-versus-leukemia (GVL) effect after allogeneic stem cell transplantation for chronic myeloid leukemia (CML). This study demonstrates that CD4+ T cells specific to the b2a2 peptide can be generated from a normal allogeneic stem cell transplant donor after stimulation with monocyte-derived dendritic cells (Mo-DC) using culture conditions applicable to clinical use. Stimulation of donor T-cell enriched mononuclear cells (MNC) with b2a2-pulsed Mo-DC produced approximately 3 x 10(9) b2a2-specific CD4+ T cells. The CD4+ T cells were HLA-DR7 restricted. These results confirm that the generation of donor derived b2a2-specific T cells for clinical use is feasible and warrants clinical testing after stem cell transplantation.

Revelation of a cryptic major histocompatibility complex class II-restricted tumor epitope in a novel RNA-processing enzyme

CD4+ T-cell responses against human tumor antigens are a potentially critical component of the antitumor immune response. Molecular methods have been devised for rapidly identifying MHC class II-restricted tumor antigens and elucidating the recognized epitopes. We describe here the identification of neo-poly(A) polymerase (neo-PAP), a novel RNA processing enzyme overexpressed in a variety of human cancers, by screening a melanoma-derived invariant chain fusion cDNA library with tumor-reactive CD4+ T lymphocytes. A cryptic nonmutated HLA-DRbeta1*0701-restricted neo-PAP epitope was processed through the endogenous MHC class II pathway. A unique point mutation effected a nonconservative substitution of a leucine for a proline residue at a structurally important site in neo-PAP that was remote from the recognized peptide, revealing a normally silent epitope for immune recognition. Genetic aberrations such as the described point mutation can have unexpected immunological consequences, in this case leading to immune recognition of a distant normal self epitope.

Identification of an antigenic epitope for helper T lymphocytes from carcinoembryonic antigen

PURPOSE

The product of the carcinoembryonic antigen (CEA) gene is an attractive candidate for T-cell-based immunotherapy because it is frequently expressed in epithelial solid carcinomas. Although many CEA peptide epitopes capable of stimulating CTLs have been identified, no MHC class II-restricted T helper epitope has yet been reported.

EXPERIMENTAL DESIGN

The amino acid sequence of CEA was examined for the presence of potential T helper epitopes, and candidate peptides were used to stimulate in vitro T-cell responses.

RESULTS

We describe here that using an algorithm to identify promiscuous helper T-cell epitopes, a peptide of CEA occupying residue positions 653 to 667 (CEA(653-667)), was effective in inducing in vitro T helper responses in the context of the HLA-DR4, HLA-DR7, and HLA-DR 9 alleles. Most significantly, some of the peptide-reactive helper T lymphocytes were also capable of recognizing naturally processed antigen in the form of recombinant CEA protein or cell lysates from tumors that express CEA. Interestingly, the newly identified helper T-cell epitope was found to overlap with a previously described HLA-A24-restricted CTL epitope, CEA(652-660), which could facilitate the development of a therapeutic vaccine capable of eliciting both CTL and T helper responses in patients suffering from epithelial carcinomas.

CONCLUSION

These results indicate that T helper lymphocytes are capable of recognizing CEA as a tumor antigen and that epitope CEA(653-667) could be used for immunotherapy against tumors expressing CEA.

Identification of HLA DR7-restricted epitopes from human telomerase reverse transcriptase recognized by CD4+ T-helper cells

CD4+ T cells play critical roles in initiating, regulating, and maintaining antitumor immune responses. One way to improve current tumor vaccines that mainly induce CTLs would be to activate antigen-specific CD4+ T cells that recognize MHC class II restricted tumor associated antigens. Human telomerase reverse transcriptase (hTRT) is preferentially expressed by various tumors and, therefore, could be a universal tumor antigen. In this study, we used a combined approach of using the prediction software TEPITOPE to select class II epitope candidates and in vitro T-cell biological analysis to identify class II-restricted epitope(s) in hTRT. We first identified several HLA-DR7-restricted class-II epitope candidates in hTRT by examining human T-cell responses to synthetic peptides. We then characterized these HLA-DR7-restricted hTRT epitope candidates by establishing and analyzing peptide-specific T-cell clones. It was demonstrated that CD4+ T cells specific for the HLA-DR7-restricted hTRT(672) epitope (RPGLLGASVLGLDDI) can respond to naturally processed hTRT proteins. Furthermore, the hTRT(672)-specific T cells recognized hTRT antigen from various tumors, including prostate cancer, breast cancer, melanoma, and leukemia. Thus, the identification of the naturally processed HLA-DR7-restricted hTRT epitope, together with the previous finding of class I-restricted hTRT epitopes, provide a basis for the combined application of class I- and II-restricted hTRT epitopes to induce potent, long-term CD4+ and CD8+ T-cell responses against a broad spectrum of tumors.

Human lymphocyte antigen DR7 protects against proliferative retinopathy with type II diabetes mellitus

BACKGROUND

This study was undertaken in order to analyze the genetic incidence of human lymphocyte antigen diabetic retinopathy (HLA-DR) and its influence in proliferative diabetic retinopathy (PDR).

METHODS

We designed a case-control study in which 127 mestizo Mexican patients with DM II and diabetic retinopathy were studied. DNA was extracted and HLA-DR regions were amplified using PCR. Alleles were determined by DNA hybridization. Diagnosis was assessed clinically and by fluorescein angiography. Incidence of HLA-DR alleles in patients was compared with an ethnically matched control group of healthy subjects (n = 98). Statistical significance was established with non-parametric tests.

RESULTS

Patients with diabetic retinopathy showed less frequency of HLA-D11 compared with the control group (p = 0.043). NPDR patients with 10 or more years of DM II showed an increase of HLA-DR7 (p = 0.01).

CONCLUSIONS

Our results suggest that the presence of HLA-DR7 protects against the development of proliferative disease in the diabetic Mexican population.

Identification of helper T-cell epitopes that encompass or lie proximal to cytotoxic T-cell epitopes in the gp100 melanoma tumor antigen

The melanocyte-associated antigen gp100 constitutes one of the most attractive targets for T-cell-based immunotherapy against malignant melanoma. Although several MHC class I-restricted epitopes have been identified for CTLs, thus far, only one MHC class II T helper epitope (restricted by HLA-DR4) has been described in the literature. Using an algorithm to identify promiscuous helper T-cell epitopes, here we describe three additional MHC class II-restricted epitopes from gp100. Whereas one T helper epitope, gp100(175-189), was restricted by the HLA-DR53 and DQw6 alleles, the T-cell responses to two other epitopes, gp100(74-89) and gp100(576-590), were restricted by HLA-DR7. Most interestingly, the newly identified helper T lymphocyte epitopes encompass or lie proximal to previously described CTL epitopes for this tumor-associated antigen. Together with the previously described HLA-DR4-restricted epitope, these T helper epitopes offer coverage for the majority of the human population. Moreover, the use of peptide vaccines containing both CTLs and T helper epitopes could offer therapeutic advantages over current approaches that focus solely on eliciting antitumor CTL responses.

Tumor-reactive T helper lymphocytes recognize a promiscuous MAGE-A3 epitope presented by various major histocompatibility complex class II alleles

The development of effective T cell-based immunotherapy for cancer requires the identification of antigens capable of inducing both CTL and T helper immune responses. Although CTLs will participate in the antitumor response mainly by exerting their lytic activity on the tumor cells, helper T lymphocytes will be critical for the induction and maintenance of the CTLs. Thus, effective subunit therapeutic vaccines should include both CTL and T helper epitopes from antigens expressed on the tumor cells. The product of the MAGE-A3 gene is an attractive candidate for tumor immunotherapy because it is expressed in the majority of melanomas and in a great proportion of other solid tumors. Although numerous CTL epitopes for the MAGE-A3 antigen have been reported, only a few have been described for helper T cells. Here we show that a synthetic peptide derived from the MAGE-A3 sequence (MAGE-A3(146-160)) was effective in inducing in vitro T helper responses in the context of HLA-DR4 and HLA-DR7 alleles. Most significantly, the peptide-reactive helper T lymphocytes were capable of recognizing various forms of MAGE-A3 antigen (tumor cell lysates, dead/apoptotic tumor cells, or recombinant MAGE-A3 protein), indicating that the T-cell epitope represented by peptide MAGE-A3(146-160) is naturally processed by antigen-presenting cells. These studies are relevant for the design of multi-epitope vaccines for treating MAGE-A3-expressing tumors through the simultaneous stimulation of CTL and T helper lymphocytes.

Properties of HLA class II molecules divergently associated with Goodpasture's disease

Goodpasture's disease provides an opportunity to analyse molecular mechanisms that may underlie MHC class II associations with autoimmune disease because it is caused by autoimmunity to a defined antigen [the 230 amino acid NC1 domain of the alpha3 chain of type IV collagen (alpha3(IV)NC1)] and has strong HLA class II associations. We compared the alpha3(IV)NC1 peptide binding of class II molecules with strong positive (DR15) and dominant negative (DR7/1) associations using an inhibition binding assay and short synthetic peptides spanning the sequence of alpha3(IV)NC1. DR15 in general bound the peptides with low affinity (three of 23 < 100 nM) compared to DR1 and DR7 (12 and 10 < 100 nM respectively), and no peptide bound DR15 with much higher affinity (>10-fold) than both DR1 and DR7. Thus DR15 molecules are unlikely to increase susceptibility to Goodpasture's disease by presenting a particular alpha3(IV)NC1-derived peptide uniquely well and DR1/7 are unlikely to protect by their inability to present particular peptides. However DR1/7 could protect by capturing alpha3(IV)NC1 peptides and preventing their display bound to DR15; the binding data suggest that all the major (biochemically detectable) alpha3(IV)NC1 peptides presented bound to DR15 by DR15 homozygous antigen-presenting cells (APC) would bind preferentially to DR1/7 in DR15, 1/7 heterozygote APC.

Characteristics of Prevotella intermedia-specific CD4+ T cell clones from peripheral blood of a chronic adult periodontitis patient

Periodontitis is a chronic destructive inflammatory disease associated with periodontopathic bacteria. In addition, autoantigens such as collagen and heat shock proteins (hsp) have been suggested to play a role. Established periodontal lesions are characterized by dense infiltrations of immune cells such as cytokine-producing CD4+ and CD8+ T cells. CD4+ T cells specific for Prevotella intermedia can be isolated from lesional gingiva, suggesting an active role for CD4+ T cells in the response to this bacterium. We therefore investigated the characteristics of a panel of 13 P. intermedia-specific CD4+ T cells generated from the peripheral blood of a patient with chronic adult periodontitis. All 13 P. intermedia-specific CD4+ T cells recognized the antigens in the context of HLA-DR. The T cell clones were mainly classified as Th0, producing comparable amounts of interferon-gamma (IFN-gamma) and IL-4, and Th2, producing high amounts of IL-4 and almost no IFN-gamma. None of the P. intermedia-specific T cell clones recognized antigens of the periodontopathic bacteria Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis and of the autoantigens collagen and hsp. The reactivity profile of the T cell clones to size-fractionated cell envelope antigens of P. intermedia indicated that P. intermedia-specific CD4+ T cell clones recognize probably five different antigen specificities in the context of the MHC class II molecules, DR7 or DR15. These results suggest that a broad panel of cell-associated protein antigens play a role in the induction of P. intermedia-specific CD4+ T cell response.

[Connection between Epstein-Barr virus infection and HLA phenotype and features of cytokine status in patients with non-Hodgkin's lymphomas]

Thirty-four primary (untreated) patients with non-Hodgkin's lymphomas (NHL) infected with Epstein-Barr virus (EBV) were examined. Their HLA phenotype and the production of interleukin-1 beta and tumor necrosis factor alpha were assessed. Serological profiles characteristic of the late stages and reactivation of EBV infection were detected in 16 (47.1%) patients. NHL of low malignancy predominated in EBV-infected patients. A greater number of blank HLA-A antigens and a higher incidence of HLA-DR7 antigen was observed in infected patients. Serum concentration of tumor necrosis factor alpha was reliably higher in them, whereas the production of this cytokine by the peripheral blood mononuclears decreased. Hence, serum tumor necrosis factor is a product of transformed B lymphocytes. Spontaneous and stimulated production of interleukin-1 beta by peripheral blood mononuclears was significantly decreased in EBV-infected patients, and the serum concentration of this cytokine similarly had a trend to decrease, which indicates an inhibition of interleukin-1 beta production in EBV-infected patients with NHL.

A novel approach to human anti-HLA mABs production: use of phage display libraries

The production of human monoclonal antibodies was previously limited to very laborious and time-consuming processes involving EBV-transformation and/or hybridoma generation. Due to the development of molecular cloning techniques, it is now possible to produce human monoclonal antibody fragments quickly by panning phage display libraries against predefined antigenic specificities. Therefore, we tested this technology for producing human single chain Fv fragments (scFvs) against HLA-DR1 purified molecules immobilized on solid phase. Enrichment of DR1-specific phages was measured through five selection rounds of a synthetic library and revealed a 100-fold amplification. Soluble antibody fragments were then expressed and 7 out of 48 clones were found to secrete scFvs which specifically bind to DR1 molecules in ELISA. Further analysis revealed binding of the scFvs also to DR3 but not to DR5 or DR7 molecules correlating with the presence of particular polymorphic aminoacid residues in the DR beta chain. Western blot analysis indicated that the 7 scFvs react with the DR1 alpha/beta-dimer but not with free alpha- or beta- chains. This study shows that the innovative approach of phage display libraries can efficiently provide scFv fragments as useful reagents for the identification and dissection of HLA polymorphic epitopes.

Modulation of the immune response in multiple sclerosis: production of monoclonal antibodies specific to HLA/myelin basic protein

Monoclonal Abs to the complex formed between human MHC class II molecules (DR7 and DRw11) and myelin basic protein (MBP) were produced. The specificity of these Abs was established by both FACS analysis and complement-mediated cytotoxicity of MBP- or OVA-pulsed human APC of the same or of different DR restriction. These Abs bound to and lysed only MBP-pulsed human APC of the same DR restriction (DR7 or DRw11) but not to APC of different DR restriction or pulsed with a different Ag (OVA). The physiologic role of these Abs was further investigated. They blocked the in vitro proliferative response to MBP-specific T cell clones isolated from multiple sclerosis patients in an antigen-specific and DR-restricted manner. However, the Abs did not affect the response of MBP-specific T cell clones of other DR restriction nor did they interfere with the response to other Ags (purified protein derivative or copolymer 1) presented on APC with the same DR restriction. These Abs may be useful for treating multiple sclerosis in which reactivity to MBP is implicated. Moreover, this approach may be extended to other autoantigens and their counterpart autoimmune diseases.

Relationship of anticardiolipin antibodies and antiphospholipid syndrome to HLA-DR7 in Mexican patients with systemic lupus erythematosus (SLE)

We studied IgG and IgM anticardiolipin antibodies (aCL) by an ELISA method in 80 Mexican systemic lupus erythematosus (SLE) patients and 378 of their first degree relatives. Sixty five percent of SLE patients and 16% of their relatives were positive for aCL. We also determined allele and haplotype frequencies of Major Histocompatibility Complex (MHC) genes (classes I, II and III) in both patients and relatives. MHC allele and haplotype frequencies of aCL positive and negative individuals were compared to those of normal ethnically matched controls. SLE patients with aCL had statistically significant increased corrected frequencies of HLA-DR3 (pC = 0.04, RR = 2.78); DR7 (pC = 0.005), RR = 3.42) and DQ2 (pC = 0.003, RR = 2.58) antigens. Their first degree relatives positive for aCL also had increased frequency of HLA-DR7 but it did not remain significant after correcting the P value. On the other hand, SLE patients negative for aCL had a moderate increased frequency of DR3 and DQ2 but not of DR7. These results suggest that DR7 associates with the presence of aCL. The distribution of MHC alleles in SLE patients positive for aCL resembles that found in their aCL positive first degree relatives. Since the presence of the antibody is not sufficient to predict a clinical outcome, we studied those patients with reliable clinical data regarding the presence of the antiphospholipid syndrome (aPLS). SLE patients with aPLS had significantly increased frequency of DR7 (pC = 0.004), as did those with probable aPLS (pC = 0.05), while the frequency of DR7 in SLE patients in the doubtful or negative aPLS categories was no different from normal controls. These data support a possible role of DR7 in the development of aCL in SLE patients and their relatives and suggest a contribution of this class II MHC antigen to the development of aPLS within SLE.

Breast cancer-associated antigen, DF3/MUC1, induces apoptosis of activated human T cells

Given the plethora of well-documented breast carcinoma-associated antigens in humans including MAGE-1, -2 and -3, mutated p53, p21ras, HER-2/neu and DF3/MUC-1, coupled with evidence that humoral and cytotoxic T-cell responses against these antigens exist, the central dilemma facing tumor immunologists is why the host immune response is so inefficient. One possibility is that tumor cells themselves are either inefficient or ineffective antigen-presenting cells (APCs). The failure of tumor cells to function as APCs may be due to their inability to process and present the antigen, the absence or insufficient numbers of adhesion and costimulatory molecules or, potentially, the secretion of inhibitory cytokines. Therefore, we sought to determine whether human breast cancer cell lines could function as APCs and, if not, to identify mechanism(s) responsible for this defect. Here, we show that human breast cancer cell lines fail to present alloantigen. This defect does not reside in their inherent capacity to present antigen but rather is due to apoptosis of activated T cells induced by exposure to the breast carcinoma-associated mucin antigen, DF3/MUC1. These results support the hypothesis that DF3/MUC1 may contribute to the paucity of clinically significant anticarcinoma-specific immune responses.

R24 anti-GD3 ganglioside antibody can induce costimulation and prevent the induction of alloantigen-specific T cell clonal anergy

R24 is a monoclonal antibody directed against the cell surface ganglioside GD3. It can detect GD3 on the surface of a subset of T lymphocytes and can stimulate proliferation and secretion of cytokines in vitro. In the present report, we examined the effects of the R24 antibody upon antigen-specific T cell response, employing an HLA-DR7-specific T cell clonal model. As previously shown, primary stimulation of HLA-DR7-specific alloreactive T cell clones by transfectants expressing HLA-DR7 alone (t-DR7) in the absence of B7 co-stimulation resulted in anergy. Binding of cell surface GD3 on HLA-DR7-specific alloreactive T cell clones with R24 under these anergizing conditions resulted in interleukin-2 (IL-2) accumulation and prevented the induction of alloantigen-specific T cell clonal anergy. Binding of GD3 by R24 also prevented anergy under conditions where B7:CD28 interactions were blocked by CTLA4-Ig. The effect of R24 was abrogated in the presence of a combination of monoclonal antibodies for the alpha and beta chains of the IL-2 receptor (IL-2R) or a neutralizing anti-IL-2 antibody. R24 does not appear to interact directly with the IL-2R since incubation of T cell clones with R24 did not induce early activation of IL-2R associated Jak kinases, Jak1 and Jak3, as was induced following incubation with IL-2. In contrast, incubation of HLA-DR7-specific clones with t-DR7 in the presence of R24 did result in phosphorylation of IL-2R related Jak kinases after 24 h. Our data indicate that the membrane ganglioside GD3 structure recognized by R24 may play an important role in antigen-specific T cell clonal response.

Allergy to olive pollen: T-cell response from olive allergic patients is restricted by DR7-DQ2 antigens

BACKGROUND

We have recently described the association between the IgE antibody response to Ole e I (the major antigen from olive tree pollen) and the DR7-DQ2 haplotype in a Spanish population.

OBJECTIVE AND METHODS

Due to the linkage disequilibrium between DR7 and DQ2, and thus the difficult distinction between the role of these two antigens in the T-cell activation response, we decided to solve this question by two approaches: 1. The study of another ethnic group, individuals of Arabic origin, with a presumably distinct disequilibrium linkage between DR and DQ antigens. Genomic DNA typing was performed in 46 subjects (allergic and non-allergic) by Restriction Fragment Length Polymorphism (RFLP) and results showed that patients with specific IgE antibodies alpha-Ole e I, were DR7 and/or DQ2. These data show a similar restriction pattern to those previously described for Spanish patients. The phenotypic frequency of DR7 antigen is significantly greater than in the non-allergic population, with a corrected P (Pc) value of 0.03. 2. The analysis of the genetic requirements of Ole e I response, using T-cell lines specific for this antigen. This was first carried out by blocking the proliferative response of these T-cell lines with specific anti-human HLA class II antibodies and then testing the genetic restriction of this response using a panel of histocompatible and histoincompatible Antigen Presenting Cells (APCs). Both experiments corroborate the hypothesis that DR7 and DQ2 are implicated in the recognition of Ole e I.

Differential expression of the down-regulatory function of CD8 cells in trichosanthin-induced immunosuppression and its genetic control in humans

Trichosanthin (Tk), a plant protein isolated from a Chinese medicinal herb, was shown in our previous experiments to suppress mitogenic, antigenic and allogeneic responses of human lymphocytes. Two non-toxic pathways, the CD8-dependent and the CD8-independent, were identified as being involved in inducing the suppression. In this communication, we report that, in a subgroup of healthy subjects, only the CD8-dependent pathway was found to operate. In cell cultures from the other subjects, removal of CD8 cells from the culture did not diminish the suppression, implying that the down-regulatory function of the CD8 cells was not expressed in the presence of Tk. Two types of subject, CD8 mediators (M+) (CD8-dependent pathway operating) and non-mediators (M-) (CD8-independent pathway operating), were thus distinguishable. A 'mediation index' (MI) was calculated as MI (%) = RR of CD8-depleted cell culture--RR of non-CD8-depleted cell culture. Of 68 unrelated subjects tested, 21 (30.9%) could be classified as M+, with a mean 'mediation index' of 13.4 +/- 4.0, while 47 (69.1%) were M-, with a mean MI of -5.6 +/- 4.3 (t = 17.2, P < 0.001). The M+ and M- groups exhibited an essentially non-overlapping bimodal distribution of MI. Among the 40 Caucasoids in the panel, nine of 14M+ subjects were HLA-DR7, DQ2 (chi 2 = 14.652, Pc = 0.00084). The two DR7-DQ3 panel members, however, were M-, suggesting that DQ2 might be associated with M+. Segregation patterns in two families revealed that the M+ phenotype is a Mendelian dominant trait.

Substitutions in the HLA-DR alpha chain differentially affect DR7-restricted T-cell recognition of rabies virus antigen

To investigate the functional roles of DR alpha residues in T-cell recognition, 20 mutants of the DR alpha chain were constructed by site-directed mutagenesis. These DR alpha mutants were expressed with WT DR(beta 1*0701) on mouse L cells and used as APC for four DR7-restricted T-cell clones specific for rabies virus antigens. The results indicate that the DR alpha residues are differentially involved in recognition of rabies virus antigen by different T-cell clones. Mutations in the floor of the antigen-binding groove (positions 9, 11, 22, and 24), on the alpha-helix (47, 55, 65, 66, and 72), and surprisingly on the outer loop (15, 18, and 19), abrogated recognition by at least one T-cell clone. Most of these residues appear to be involved in either peptide or TCR contact, based on the DR1 crystal structure. The involvement in T-cell recognition of DR alpha residues located in the outer loop outside the binding groove suggests that these residues may directly contact TCR, or indirectly contribute to the conformation of peptide sitting in the groove.

Major histocompatibility complex class II-associated peptides determine the binding of the superantigen toxic shock syndrome toxin-1

Superantigens bind to major histocompatibility complex (MHC) class II proteins and interact with variable parts of the T cell antigen receptor (TCR) beta-chain. Cross-linking the TCR with MHC class II molecules on the antigen-presenting cell by the superantigen leads to T cell activation that plays an essential role in pathogenesis. Recent crystallographic data have resolved the structure of the complexes between HLA-DR1 and staphylococcal enterotoxin B (SEB) and toxic shock syndrome toxin-1 (TSST-1), respectively. For TSST-1, these studies have revealed possible contact sites between the superantigen and the HLA-DR1-bound peptide. Here, we show that TSST-1 binding is dependent on the MHC-II-associated peptides by employing variants of T2 mutant cells deficient in loading of peptides to MHC class II molecules as superantigen-presenting cells. On HLA-DR3-transfected T2 cells, presentation of TSST-1, but not SEB, was dependent on HLA-DR3-associated peptides. Thus, although these superantigens can be recognized in the context of multiple MHC class II alleles and isotypes, they clearly bind to specific subsets of MHC molecules displaying appropriate peptides.

Identification of mycobacterial peptide epitopes recognized by CD4+ T cells in association with multiple major histocompatibility complex class II molecules

The mycobacterial 18-, 28-, and 65-kDa proteins are recognized by T cells in association with multiple class II HLA-DR molecules of the major histocompatibility complex (MHC). To identify the epitopes recognized by T cells in association with multiple HLA-DR molecules, we established CD4+ T cell lines and clones and tested them with overlapping synthetic peptides corresponding to the entire amino acid sequence of the 18- and 65-kDa antigens and to the carboxy terminus of the 28-kDa antigen. The T cell lines established against the 18-kDa antigen recognized three different epitopes, one of which was recognized in the presence of antigen-presenting cells from several allogeneic donors. The 65-kDa antigen-reactive T cell lines responded to nine different peptides, two of which were promiscuous with respect to MHC restriction. The T cell clones responding to the 28-kDa antigen proliferated in response to a single peptide from the carboxy terminus. This peptide was recognized by T cell clones in association with HLA-DRw53, which is coexpressed in individuals expressing HLA-DR4, HLA-DR7, and HLA-DR9. The T cells activated in response to the mycobacterial antigen from vaccinated donors belonged to the protective Th1 subset; hence, the peptides recognized in association with multiple HLA-DR molecules should be useful in subunit vaccines against mycobacterial diseases.

CTLA4 mediates antigen-specific apoptosis of human T cells

The regulation of T cell-mediated immune responses requires a balance between amplification and generation of effector function and subsequent selective termination by clonal deletion. Although apoptosis of previously activated T cells can be induced by signaling of the tumor necrosis factor receptor family, these molecules do not appear to regulate T-cell clonal deletion in an antigen-specific fashion. We demonstrate that cross-linking of the inducible T-cell surface molecule CTLA4 can mediate apoptosis of previously activated human T lymphocytes. This function appears to be antigen-restricted, since a concomitant signal T-cell receptor signal is required. Regulation of this pathway may provide a novel therapeutic strategy to delete antigen-specific activated T cells.

Nonresponders to hepatitis B vaccine can present envelope particles to T lymphocytes

The mechanisms causing nonresponsiveness to hepatitis B surface Ag (HBsAg) vaccines in humans remain largely unknown. The increased incidence of nonresponsiveness in subjects with HLA-DR3 or -DR7 haplotype suggests that immune response mechanisms governed by genes of the MHC are involved. It is conceivable that APC of nonresponders are defective in the presentation of HBsAg because they are unable to adequately take up, process, or present this Ag. To examine this hypothesis we have used PBMC from nonresponders to present recombinant particles containing S or PreS2-S sequences to HBsAg-specific T cell lines from haplo-identical responder vaccinees. The proliferative response of these lines was used to evaluate the efficacy of Ag presentation. Unfractionated PBMC from five DR2+ and six DR7+ nonresponders did not proliferate to HBsAg in vitro, whereas they vigorously proliferated upon stimulation with tetanus toxoid, thus ruling out the presence of a generalized immunodeficiency. All DR2(15)+ nonresponders were able to present hepatitis B envelope Ag to HBsAg-specific, DR1501-restricted T cells. PBMC from six DR7+ nonresponders were all able to present HBsAg to DR07-restricted T cell lines and PBMC from three DPw4+ nonresponders were able to present HBsAg to DP0402-restricted T cell lines. Additional experiments showed that PBMC from two nonresponders presented HBsAg equally well and sometimes better than PBMC from two partially HLA-matched high responders. We conclude that HLA-DR2+, -DR7+, and -DPw4+ nonresponder vaccinees are able to take up, process and present HBsAg to allogeneic, haplo-identical T cell lines in vitro.

Prevention of T cell anergy by signaling through the gamma c chain of the IL-2 receptor

When stimulated through their antigen receptor without requisite costimulation, T cells enter a state of antigen-specific unresponsiveness termed anergy. In this study, signaling through the common gamma chain of the interleukin-2 (IL-2), IL-4, and IL-7 receptors in the presence of antigen was found to be sufficient to prevent the induction of anergy. After culture with IL-2, IL-4, or IL-7, Jak3 kinase was tyrosine-phosphorylated, which correlated with the prevention of anergy. Therefore, a signal through the common gamma chain may regulate the decision of T cells to either clonally expand or enter a state of anergy.

HLA and hepatitis B infection

The mechanism underlying the development of chronic infection with hepatitis B virus is not known. We have done two independent studies in Qatar, where such infection is common, to determine whether immunity to this virus is influenced by the HLA phenotype of an individual. The first study generated a hypothesis to test in the second. In both studies, there was a significant deficiency of HLA-DR2 and an excess of HLA-DR7 in patients with chronic persistent infection with hepatitis B virus. We conclude that HLA phenotype is one of the factors influencing the response to infection with this virus.

Recognition of envelope protein by dengue virus serotype-specific human CD4+ CD8- cytotoxic T-cell clones

We analyzed dengue virus-specific CD4+ CD8- cytotoxic T lymphocytes (CTL) at the clonal level to further understand their role in dengue virus infections. Stimulation of peripheral blood mononuclear cells from two dengue virus type 4 (D4V)-immune donors with live D4V or noninfectious D4V antigen generated 17 HLA class II-restricted CD4+ CTL capable of specific lysis of dengue virus antigen-treated autologous lymphoblastoid cell lines. Thirteen clones were D4V specific, three clones were cross-reactive for D2V and D4V, and one clone was cross-reactive for D1V, D3V, and D4V. Antigen recognition by six D4V-specific clones and three D2V- and D4V-cross-reactive clones was restricted by HLA-DR7. Five D4V-specific CD4+ CTL clones lysed autologous lymphoblastoid cell lines infected with a dengue virus-vaccinia virus recombinant containing the E gene of D4V, whereas three serotype-cross-reactive CTL clones did not. These results indicate that E-specific clones are serotype specific and HLA-DR7 restricted in these two donors and suggest that a common epitope on E protein may be recognized. E protein-specific CD4+ CTL may be important mediators of virus clearance especially during reinfection with the same serotype as that in primary infection by providing help for virus-specific antibody production and lysis of virus-infected cells.

[HLA DR7 as a protective factor against gold salt toxicity in rheumatoid arthritis]

We performed a study of antigens HLA type I and II (specificity DR) in 90 patients with diagnosis of Rheumatoid Arthritis (RA) treated with Sodium Aurothiomalate (SATM) in order to detect the presence of an antigen HLA which could act as a protective factor against toxicity by SATM. Our results demonstrated a decrease in the frequency of the antigen DR7 in patients with toxicity by SATM, which suggests a protective factor of this antigen against the development of toxic reactions due to gold salts.

Human T-cell clonal anergy is induced by antigen presentation in the absence of B7 costimulation

The maximal T-cell response to its antigen requires presentation of the antigen by a major histocompatibility complex class II molecule as well as the delivery of one or more costimulatory signals provided by the antigen-presenting cell (APC). Although a number of candidate molecules have been identified that are capable of delivering a costimulatory signal, increasing evidence suggests that one such critical pathway involves the interaction of the T-cell surface antigen CD28 with its ligand B7, expressed on APCs. In view of the number of potential costimulatory molecules that might be expressed on the cell surface of APCs, artificial APCs were constructed by stable transfection of NIH 3T3 cells with HLA-DR7, B7, or both. Here, we show that in a human antigen-specific model system, when tetanus toxoid peptide antigen is presented by cells cotransfected with HLA-DR7 and B7, optimal T-cell proliferation and interleukin 2 production result. In contrast, antigen presentation, in the absence of B7 costimulation, results in T-cell clonal anergy. These results demonstrate that it is possible to induce antigen-specific clonal tolerance in human T cells that have been previously sensitized to antigen. The artificial antigen-presenting system provides a useful model for the investigation of the biochemical events involved in the generation of tolerance and for the study of signals necessary to overcome tolerance.

A DR7 specific monoclonal antibody TAL13.1, raised against a transfectant detects IL-4 upregulated antigen on peripheral B-lymphocytes

A monoclonal antibody TAL13.1 was raised against mouse L cells transfected with the human HLA-DRB1*0701 gene. This antibody was found to be polymorphic recognizing a determinant expressed by the DR7, DRB1*0701 and DRB1*0702 gene products. Four polymorphic sites unique to this specificity have been identified within the DR beta 1 domain. These are residues 11-14, 25, 30 and 71-74, one or a combination of which is postulated as being responsible for conferring the specificity of the antibody. In Western blot analysis TAL13.1 was found to react with the DR alpha beta dimer, but not with the free alpha or beta chains. However, in flow cytometry it failed to bind a DR alpha/DQ beta mixed pair transfectant confirming that it recognizes an epitope on the DR beta not the DR alpha chain. Although TAL13.1, a low affinity antibody is negative or only weakly positive on resting peripheral blood lymphocytes (PBLs), we have demonstrated that by interleukin-4 (IL-4) stimulation we can up-regulate the levels of antigen already present and gain a level of binding comparable to that found on B lymphoid cell lines (B-LCLs) where it has been found to be a valuable reagent in their characterization.

The role of polymorphic HLA-DR beta chain residues in presentation of viral antigens to T cells

The relative importance of 11 polymorphic positions in the HLA-DR7 beta 1 chain in T cell recognition of foreign antigens was investigated using transfectants expressing mutant DR7 beta 1 chains as APC for five rabies virus-specific T cell clones. The results indicate that multiple amino acids, located in both the beta-strands and alpha-helix of DR7 beta 1 in the model of a class II molecule, are involved in DR7-restricted T cell recognition of these antigens. Many of the substitutions appeared to reduce the affinity of an antigenic peptide for the mutant DR7 molecules but did not prevent binding. The heterogeneity of responses of the three G-specific T cell clones to presentation of the G11.3 peptide by several of the mutant DR7 molecules indicates that the T cell receptor (TCR) of each these clones requires a different view of the G11.3/DR7 complex and raises the possibility that the G11.3 peptide may bind to the DR7 molecule in more than one conformation.

Identification of cross-reactive T cell restriction epitopes located on the DR7 beta 1 and DR beta 4 molecules

L cell fibroblasts transfected with HLA class II cDNA clones isolated from a cDNA library produced from a DR7 homozygous cell line were used as antigen-presenting cells (APC) for three HLA DR-restricted, diphtheria toxoid-specific T-cell clones in order to assess the antigen-presenting ability of the transfectants and to define the class II restriction of each clone. Class II-expressing transfectants are capable of presenting antigen to antigen-specific T-cell clones, although the transfectants are less efficient at antigen presentation than conventional APC. Paraformaldehyde fixation of transfectants prior to antigen pulsing abrogated antigen presentation, demonstrating that the transfectants require antigen processing. Antigen presentation by transfectants is completely inhibited by CD4-specific monoclonal antibodies (mAb) and one of four DR-specific mAb, whereas antigen presentation by conventional APC is only partially inhibited. Both the DR alpha:DR7 beta 1 and DR alpha:DR beta 4 (DR omega 53) molecules of the DR7 allotype serve as restriction elements for the diphtheria toxoid-specific T-cell clones. One clone is restricted by the DR7 beta 1 molecule, another clone by the DR beta 4(DR omega 53) molecule, and a third clone by a cross-reactive T cell epitope on DR7 beta 1 and DR beta 4(DR omega 53) molecules. The two DR beta 4(DR omega 53)-restricted clones react, however, differently with a panel of HLA-DR DR omega 53-positive human peripheral blood lymphocytes used as APC. Therefore the data presented here clearly document that the DR beta 4 (DR omega 53) chain may serve as restriction elements for DT-specific T-cell clones. They also provide the first evidence for functional cross-reactivity of the products of two different DR beta loci and in addition emphasize the high complexity of the supertypic HLA-DR omega 53 specificity.

Definition of a new supertypic HLA class II determinant (LAR) associated with HLA-DR2 and -DR7

A serum from a patient (LAR), immunized by pregnancies and blood transfusions, reacted with cells carrying HLA-DR2 and/or -DR7 specificities (titer 1:200-1:1000). Absorption-elution experiments showed that the allo-serum recognized a determinant shared by DR2 and DR7 cells. The high correlation coefficients (0.90-1) with these specificities suggested that the supertypic specificity LAR was carried by the first DR molecule encoded by DRB1 gene. LAR is another example of new supertypic specificities, reflecting structural homologies between alleles at HLA class II loci.