Role of cytotoxic T-lymphocyte-mediated immune selection in a dominant human leukocyte antigen-B8-restricted cytotoxic T-lymphocyte epitope in Nef.

OBJECTIVES: To study the role of cytotoxic T-lymphocyte (CTL) escape for disease progression in HIV-1 infection, we analyzed the CTL response to the dominant human leukocyte antigen (HLA)-B8-restricted CTL epitope FLKEKGGL (FL8) in HIV-1 Nef. METHODS: HIV-1 nef genes derived from 56 patients were analyzed by polymerase chain reaction (PCR)-based sequencing. T-cell responses against FL8 and mutated FL8 variants were detected by gamma-interferon (gamma-IFN) enzyme linked immunospot (ELISPOT) assay. RESULTS: The longitudinal analysis of an HIV-1-infected patient with good control of HIV-1 viremia for several years demonstrated an association of rising viremia with the emergence of CTL escape mutations within the HLA-B8-restricted Nef-specific CTL epitopes FLKEKGGL and WPAIRERM. Analysis of nef genes in 56 HIV-1-infected patients demonstrated a significant correlation between the occurrence of mutations in the FL8 epitope and the presence of HLA-B8. The mutations within the FL8 epitope could decrease CTL recognition; however, there was strong variation regarding the recognition of viral variants between individual donors. The presence of FL8 mutations was associated with lower CD4 cell counts and higher viral loads. CONCLUSIONS: Our data demonstrate a strong CTL selection pressure on the immunodominant HLA-B8-restricted CTL epitope FL8 in HIV-1 Nef. The association of FL8 mutations with lower CD4 cell counts indicates an important role of CTL escape mutations for disease progression.

HLA-B35 influences the apoptosis rate in human peripheral blood mononucleated cells and HLA-transfected cells.

Human leukocyte antigen (HLA) class I antigens can act as signal-transducing molecules that influence individual reactivity to external stimuli and the existence of haplotype-specific cell signal regulation has been suggested. In this article, we provide definite experimental evidence for the existence of a HLA-B35 haplotype-specific regulation of cell apoptosis in different experimental models. First, we demonstrated that HLA-B35, but not other HLA-class I antigens, was associated with an increased cell susceptibility to apoptosis in human peripheral mononuclear cells (PBMCs) exposed in vitro to thapsigargin. Second, we confirmed this association in human ECV 304 cells transfected with HLA-B35 or with HLA-B8, an antigen that did not appear to influence the apoptosis rate in the thapsigargin-treated PBMCs. Third, we confirmed the specific influence of HLA-B35 on cell apoptosis in non human cells (i.e., HLA-B35-transfected NIH3T3 murine fibroblasts). Our data show the existence of HLA-B35 haplotype-specific regulation of cell apoptosis and open new perspectives on the role of HLA class I genes in cell activation and disease susceptibility.

[Role of HLA phenotype in the formation of chronic hepatitis C virus infection]. / Rol' HLA-fenotipa v formirovanii khronicheskoi HCV-infektsii.

Clinical, biochemical and immunological parameters depending on HLA-phenotypic features were examined in 107 patients aged 18-78 years with chronic hepatitis C virus (HCV) infection. Clinical and biochemical manifestations (asthenic, pain and cytolytic syndromes, hepatomegalia, hyperbilirubinemia, hypoprothrombin- and proteinemia), observed in hepatitis C, were more pronounced in patients having HLA-A30, B35, B41, Cw2, A1-B35, A9-B8. The carriers of B8 and B35 antigens were found to have inadequate immune response in HCV infection, manifested by progressive chronic process in the liver and the development of cirrhosis in patients with such specificity.

Recombinant modified vaccinia virus Ankara efficiently restimulates human cytotoxic T lymphocytes in vitro.

The immunogenicity of recombinant modified vaccinia Ankara, a highly attenuated vaccinia virus, expressing influenza nucleoprotein (MVA-NP) and HIV-1 gag (MVA-gag) was investigated. Restimulation of peripheral blood lymphocytes of healthy subjects with MVA-NP led to expansion of CTL with specificity for known NP epitopes. These CTL efficiently lysed NP peptide-pulsed targets and released interferon-gamma (IFN-gamma) on contact with epitope peptide. MVA-NP-stimulated CTL specific for the HLA-B8 epitope, NP380-88, stained with a tetrameric complex of HLA-B8 refolded with the NP380-88 peptide and anti-CD8 antibody on flow cytometry. CTL were also elicited from two HIV-1 seropositive donors by restimulation with MVA-HIV-1 gag and showed specificity for immunodominant gag epitopes. These data indicate that restimulation of human CTL with recombinant MVA is effective and suggest that MVA will elicit CTL responses in humans in vivo.

A large, single center investigation of the immunogenetic factors affecting liver transplantation.

BACKGROUND: Reports on the relevance of immunogenetic factors in liver transplantation are often conflicting or inconclusive. We have, therefore, investigated a range of factors that may underlie liver graft survival. METHODS: The influences of HLA, flow cytometric, and enhanced cytotoxic crossmatching and immunoglobulin (Ig)A levels on graft survival, and acute and chronic rejection were investigated for a single center involving 446 patients over 13 years. RESULTS: The effect of HLA mismatching on graft survival was significant (P<10(-2)) and was reversed in recipients with autoimmune diseases (P<0.5x10(-2)), whereas the effect of HLA mismatches on the level of acute rejection was detrimental in all recipients. There was a significant effect of a positive cytotoxic crossmatch on 3-month (P<10(-5)) and 1-year (P<10(-4)) graft survival, and an additional effect of the flow cytometric crossmatch was seen for chronic rejection (P<10(-2)) and acute rejection (P<10(-2)). Recipients with HLA-A1,B8,DRB1*0301 had higher levels of acute rejection (P<0.5x10(-2)), and recipients who received an ABO compatible-nonidentical transplant have a significantly higher risk (P<10(-2)) of developing chronic rejection. Finally, the beneficial effect of high serum IgA and, specifically, IgA anti Fab, seen in renal transplants was not evident in liver transplants, and in fact the opposite may be true, at least for acute rejection (P<0.5x10(-2)). CONCLUSIONS: By separating the recipients with autoimmune disease from other patients and by including acute and chronic rejection as outcome parameters, we have used the power of a large single-centre study to delineate the significance of some of the important immunogenetic factors involved in liver transplantation.

The impact of HLA on long-term outcome after thymectomy for myasthenia gravis.

In a retrospective series of 86 patients with myasthenia gravis, the only factors predictive of improvement in muscular strength after transsternal thymectomy were preoperative severity of myasthenia (90% versus 54%, p = 0.0014) and HLA-B8 (79% versus 50%, p = 0.0060) in bivariable and multivariable analyses. Both factors were not interrelated (p = 0.824). The statistical effect of HLA-B8 was independent from preoperative severity of disease. Typing for HLA-B8 may thus be a valuable adjunct in predicting the benefit of thymectomy in myasthenia. The observation that an MHC class I allele is associated with clinical improvement after thymectomy suggests that the clinical course of myasthenia may be influenced by class I restricted T-cells.

Possible role of HLA in hepatotoxicity. An exploratory study in 71 patients with drug-induced idiosyncratic hepatitis.

Possible associations between particular human leucocyte antigen molecules and immunoallergic hepatitis have been suggested previously (HLA-A11 in halothane hepatitis, HLA-DR6 and DR2 in nitrofurantoin hepatitis, HLA-B8 in clometacin hepatitis). In this study the HLA haplotype was determined in 71 patients with idiosyncratic hepatitis due to different drugs. The prevalence of HLA-A11 was twice as high in the 71 patients in the study (23%) as in controls (12%), but p-values were not significant when corrections were made for the large number of comparisons (n = 39). The prevalences of HLA-DR2, DR6, and B8 were similar in the 71 patients and in controls. When hepatitis due to particular drugs was considered, HLA-A11 was found to be present in six of 12 patients (50%) with hepatitis caused by tricyclic antidepressants, and three of four patients (75%) with diclofenac hepatitis, compared to 12% in controls. HLA-DR6 was present in four of five patients (80%) with chlorpromazine hepatitis, compared to 22% in controls. In conclusion, the HLA phenotype does not contribute significantly to idiosyncratic drug-induced hepatitis considered collectively. Possible associations between some HLA molecules and the hepatotoxicity of certain drugs require further confirmation.

Natural killer and lymphokine-activated killer activity in HLA-B8,DR3-positive subjects.

The haplotype HLA-B8,DR3 is over-represented in several autoimmune diseases, implying that genes predisposing people to these disorders are linked to this haplotype. In these diseases, various dysfunctions reflecting an impairment of the immune system have been found. Several reports indicate also that in HLA-B8,DR3-positive healthy subjects similar disorders may be demonstrated. In the present work, we have evaluated NK and LAK activity in these subjects. The study has been performed on monocyte-depleted peripheral blood MNCs by using, the K-562 cell line as a target for NK activity and the HL-60 cell line for as a target LAK activity. LAK cells were obtained by incubating MNCs for 3 days with 100 U/ml of rIL-2. The results of our experiments demonstrate that NK cell activity is significantly decreased in healthy subjects bearing the HLA-B8,DR3 haplotype. Since the number of circulating CD16+ cells is not significantly different between HLA-B8,DR3-positive subjects and negative ones, it is unlikely that this defect is due to a decreased number of NK cells in effector cell preparations. The observation that the treatment with rIL-2 can restore the killer activity of MNCs from these subjects suggests instead that the reduced NK activity may be due at least in part to the imbalance of cytokine network that has been demonstrated in HLA-B8,DR3-positive subjects. Finally, since a decreased NK activity has been reported in the autoimmune diseases linked to this haplotype, our results support the suggestion that immunologic changes observed in autoimmune diseases reflect systemic regulatory disorders that have a genetic basis.

An antigen processing polymorphism revealed by HLA-B8-restricted cytotoxic T lymphocytes which does not correlate with TAP gene polymorphism.

In previous studies of antigen presentation through HLA-B27, we identified a healthy person whose lymphoblastoid cells do not present three B27-restricted viral epitopes to specific cytotoxic T lymphocytes (CTL), despite adequate cell surface expression of HLA-B2702 of normal sequence. Similar findings were observed in all members of his family sharing the HLA-A3-B2702 haplotype. The original donor, NW, carries HLA-B8 on his other class I haplotype, which his daughter, HW, has inherited. We now report a failure to present an HLA-B8-restricted epitope from influenza nucleoprotein following viral infection of NW cells, although exogenous added peptide is still presented normally. However, cells from HW, which do not carry the A3-B2702 haplotype, present the expected epitope after viral infection. Another B8-restricted epitope, from human immunodeficiency virus-gag, is presented equally well by both cell lines when infected with gag-vaccinia. This antigen processing phenotype does not correlate with any of the known human TAP-1 and TAP-2 polymorphisms.