Hfe : une molécule à l’interface entre immunité et métabolisme du fer ?

International audienc

Conservation and Diversity of Influenza A H1N1 HLA-Restricted T Cell Epitope Candidates for Epitope-Based Vaccines

Background: The immune-related evolution of influenza viruses is exceedingly complex and current vaccines against influenza must be reformulated for each influenza season because of the high degree of antigenic drift among circulating influenza strains. Delay in vaccine production is a serious problem in responding to a pandemic situation, such as that of the current H1N1 strain. Immune escape is generally attributed to reduced antibody recognition of the viral hemagglutinin and neuraminidase proteins whose rate of mutation is much greater than that of the internal non-structural proteins. As a possible alternative, vaccines directed at T cell epitope domains of internal influenza proteins, that are less susceptible to antigenic variation, have been investigated. Methodology/Principal Findings: HLA transgenic mouse strains expressing HLA class I A*0201, A*2402, and B*0702, and class II DRB1*1501, DRB1*0301 and DRB1*0401 were immunized with 196 influenza H1N1 peptides that contained residues of highly conserved proteome sequences of the human H1N1, H3N2, H1N2, H5N1, and avian influenza A strains. Fifty-four (54) peptides that elicited 63 HLA-restricted peptide-specific T cell epitope responses were identified by IFN-γ ELISpot assay. The 54 peptides were compared to the 2007-2009 human H1N1 sequences for selection of sequences in the design of a new candidate H1N1 vaccine, specifically targeted to highly-conserved HLA-restricted T cell epitopes. Conclusions/Significance: Seventeen (17) T cell epitopes in PB1, PB2, and M1 were selected as vaccine targets based on sequence conservation over the past 30 years, high functional avidity, non-identity to human peptides, clustered localization, and promiscuity to multiple HLA alleles. These candidate vaccine antigen sequences may be applicable to any avian or human influenza A virus. © 2010 Tan et al

Sustained Progression-Free Survival Benefit of Rituximab Maintenance in Patients With Follicular Lymphoma : Long-Term Results of the PRIMA Study

PURPOSE The PRIMA study (ClinicalTrials.gov identifier: NCT00140582) established that 2 years of rituximab maintenance after first-line immunochemotherapy significantly improved progression-free survival (PFS) in patients with follicular lymphoma compared with observation. Here, we report the final PFS and overall survival (OS) results from the PRIMA study after 9 years of follow-up and provide a final overview of safety. METHODS Patients (> 18 years of age) with previously untreated high-tumor-burden follicular lymphoma were nonrandomly assigned to receive one of three immunochemotherapy induction regimens. Responding patients were randomly assigned (stratified by induction regimen, response to induction treatment, treatment center, and geographic region) 1:1 to receive 2 years of rituximab maintenance (375 mg/m(2), once every 8 weeks), starting 8 weeks after the last induction treatment, or observation (no additional treatment). All patients in the extended follow-up provided their written informed consent (data cutoff: December 31, 2016). RESULTS In total, 1,018 patients completed induction treatment and were randomly assigned to rituximab maintenance (n = 505) or observation (n = 513). Consent for the extended follow-up was provided by 607 patients (59.6%) of 1,018 (rituximab maintenance, n = 309; observation, n = 298). After data cutoff, median PFS was 10.5 years in the rituximab maintenance arm compared with 4.1 years in the observation arm (hazard ratio, 0.61; 95% CI, 0.52 to 0.73; P <.001). No OS difference was seen in patients randomly assigned to rituximab maintenance or observation (hazard ratio, 1.04; 95% CI, 0.77 to 1.40; P = .7948); 10-year OS estimates were approximately 80% in both study arms. No new safety signals were observed. CONCLUSION Rituximab maintenance after induction immunochemotherapy provides a significant long-term PFS, but not OS, benefit over observation.Peer reviewe

The Th1 immune response against HIV-1 Gag p24-derived peptides in mice expressing HLA-A02.01 and HLA-DR1

Using HLA-DR1-transgenic H-2 class II knockout mice, we identified two new HLA-DR1-restricted HIV-1 Gag p24-derived epitopes (Gag321–340 and Gag331–350) and confirmed the immunogenicity of seven that have been previously described. The human relevance was confirmed for the two new ones (Gag321–340 and Gag331–350) assaying peripheral blood mononuclear cells from HLA-DR1+ HIV-1-infected long-term asymptomatic subjects and showing that Gag331–350 could prime CD4+ T cells from two HLA-DR1+ HIV-1 seronegative donors in vitro. Seven of these epitopes, structurally conserved among HIV-1 clade B isolates, were selected for a comparative evaluation of their Th1 helper potential by immunizing HLA-A02.01/HLA-DR1-transgenic, H-2 class I/class II knockout mice with recombinant mouse invariant chain constructs in which each helper epitope was inserted in association with two reporter HIV-1-derived HLA-A02.01-restricted CD8+ T cell epitopes. A T helper effect was demonstrated in all cases, and was particularly strong with epitopes Gag301–320, Gag321–340 and Gag271–290, which should, therefore, be considered in the design of new vaccines

Identification of novel HLA-DR1-restricted epitopes from the hepatitis B virus envelope protein in mice expressing HLA-DR1 and vaccinated human subjects

Helper T lymphocytes that control CD8+ T-cell and antibody responses are key elements for the resolution of infection by the hepatitis B virus and for the development of effective immunological memory after hepatitis B vaccination. We have used H-2 class II-deficient mice that express the human MHC class II molecule, HLA-DR1, to identify novel hepatitis B virus envelope-derived T helper epitopes. We confirmed the immunogenicity of a previously described HLA-DR1-restricted epitope, and identified three novel epitopes. CD4+ T-cell immune responses against these epitopes were detected in peripheral blood mononuclear cells from HLA-DR1+ individuals vaccinated against hepatitis B. We showed that subjects receiving the currently available hepatitis B vaccines do not develop cross-reactive T helper responses against one of the novel epitopes which are structurally variable between different hepatitis B virus subtypes. These findings highlight the need for developing vaccines against a wider range of viral subtypes, and establish humanized mice as a convenient tool for identifying new immunogenic epitopes from pathogens

Comparison of HLA-DR1-directed T cell response induced in HLA-DR1 transgenic mice deficient for murine MHC class II and HLA-DR1 transgenic mice expressing endogenous murine MHC class II molecules

Transgenic mice expressing human HLA class II molecules provide a useful model for identifying HLA-restricted CD4+ epitopes. However, the influence of endogenous murine H-2-restricted T cell responses on HLA-restricted responses is not known. In the present study, we show that HLA-DR1 transgenic mice deficient for H-2 class II expression (HLA-DR1+/+/IAβ0/0) exhibit an equivalent expression level of the transgene HLA-DR1 and a similar diversity in the TCR repertoire, but a slightly different number of CD4+ peripheral T cells, when compared to HLA-DR1 transgenic mice in which H-2 class II molecules were retained (HLA-DR1+/+/IAβ+/+). More importantly, a strong antigen-specific HLA-DR1-restricted response was observed in nearly all HLA-DR1+/+/IAβ0/0 mice immunized with HBV envelope protein (HBs) or capsid protein (HBc), whereas weak HBs- or HBc-specific HLA-DR1-restricted responses were detected in half of the immunized HLA-DR1+/+/IAβ+/+ mice. Conversely, strong HBs- or HBc-specific H-2-restricted T cell responses were detected in HLA-DR1+/+/IAβ+/+ mice but not in HLA-DR1+/+/IAβ0/0 mice. Our results indicate that the coexpression of endogenous H-2 class II molecules reduces the intensity of HLA-DR1-restricted antigen-specific responses in transgenic mice, by favoring murine over human MHC recognition and education. Thus, HLA-DR1+/+/IAβ0/0 mice represent a better model for identifying and characterizing HLA-DR1-restricted epitopes relevant for human disease

Direct Assessment of MHC Class I Binding by Seven Ly49 Inhibitory NK Cell Receptors

Mouse NK cells express at least seven inhibitory Ly49 receptors. Here we employ a semiquantitative cell–cell adhesion assay as well as class I/peptide tetramers to provide a comprehensive analysis of specificities of Ly49 receptors for class I MHC molecules in eight MHC haplotypes. Different Ly49 receptors exhibited diverse binding properties. The degree of class I binding was related to the extent of functional inhibition. The tetramer studies demonstrated that neither glycosylation nor coreceptors were necessary for class I binding to Ly49 receptors and uncovered peptide-specific recognition by a Ly49 receptor. The results provide a foundation for interpreting and integrating many existing functional studies as well as for designing tests of NK cell development and self-tolerance