Changes to the Natural Killer Cell Repertoire after Therapeutic Hepatitis B DNA Vaccination

BACKGROUND: Improvements to the outcome of adaptive immune responses could be achieved by inducing specific natural killer (NK) cell subsets which can cooperate with dendritic cells to select efficient T cell responses. We previously reported the induction or reactivation of T cell responses in chronic hepatitis B patients vaccinated with a DNA encoding hepatitis B envelope proteins during a phase I clinical trial. METHODOLOGY/PRINCIPAL FINDINGS: In this study, we examined changes in the peripheral NK cell populations occurring during this vaccine trial using flow cytometry analysis. Despite a constant number of NK cells in the periphery, a significant increase in the CD56(bright) population was observed after each vaccination and during the follow up. Among the 13 different NK cell markers studied by flow cytometry analysis, the expression of CD244 and NKG2D increased significantly in the CD56(bright) NK population. The ex vivo CD107a expression by CD56(bright) NK cells progressively increased in the vaccinated patients to reach levels that were significantly higher compared to chronically HBV-infected controls. Furthermore, modifications to the percentage of the CD56(bright) NK cell population were correlated with HBV-specific T cell responses detected by the ELISPOT assay. CONCLUSIONS/SIGNIFICANCE: These changes in the CD56(bright) population may suggest a NK helper effect on T cell adaptive responses. Activation of the innate and adaptive arms of the immune system by DNA immunization may be of particular importance to the efficacy of therapeutic interventions in a context of chronic infections. TRIAL REGISTRATION: ClinicalTrials.gov NCT00988767

Evaluation de l'immunogénicité d'un vaccin thérapeutique dans un modèle de souris humanisées et transgéniques pour l'antigène de surface du virus de l'hépatite B (application pour le traitement des porteurs chroniques de ce virus)

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Traitement des infections chroniques dues au virus de l'hépatite B par vaccination thérapeutique

Le virus de l'hépatite B (VHB) est responsable de maladies chroniques du foie pouvant évoluer vers des cirrhoses et des carcinomes hépatocellulaires. On dénombre plus de 370 millions d'individus porteurs chroniques de ce virus dans le monde. Les vaccins actuels, à base de protéines d'enveloppe virales recombinantes, préviennent l'infection de manière très efficace. Chez les porteurs chroniques du VHB, l'efficacité thérapeutique de l'interféron (IFN)-α et des antiviraux n'est que partielle. La persistance virale étant associée à une réponse immunitaire défective, d'autres approches thérapeutiques ont été proposées pour stimuler cette réponse afin de permettre le contrôle de l'infection. Des vaccins basés sur l'enveloppe ou la capside virale, combinés ou non à de nouveaux adjuvants, ainsi que des vaccins génétiques codant pour les protéines virales sont à l'essai chez l'homme. Bien qu'elle soit encore d'une efficacité partielle, la vaccination thérapeutique apparaît comme une approche prometteuse en termes de coût et de bénéfice pour les patients

Hepatitis B Virus Splice-Generated Protein Induces T-Cell Responses in HLA-Transgenic Mice and Hepatitis B Virus-Infected Patients▿

Hepatitis B virus splice-generated protein (HBSP), encoded by a spliced hepatitis B virus RNA, was recently identified in liver biopsy specimens from patients with chronic active hepatitis B. We investigated the possible generation of immunogenic peptides by the processing of this protein in vivo. We identified a panel of potential epitopes in HBSP by using predictive computational algorithms for peptide binding to HLA molecules. We used transgenic mice devoid of murine major histocompatibility complex (MHC) class I molecules and positive for human MHC class I molecules to characterize immune responses specific for HBSP. Two HLA-A2-restricted peptides and one immunodominant HLA-B7-restricted epitope were identified following the immunization of mice with DNA vectors encoding HBSP. Most importantly, a set of overlapping peptides covering the HBSP sequence induced significant HBSP-specific T-cell responses in peripheral blood mononuclear cells from patients with chronic hepatitis B. The response was multispecific, as several epitopes were recognized by CD8+ and CD4+ human T cells. This study provides the first evidence that this protein generated in vivo from an alternative reading frame of the hepatitis B virus genome activates T-cell responses in hepatitis B virus-infected patients. Given that hepatitis B is an immune response-mediated disease, the detection of T-cell responses directed against HBSP in patients with chronic hepatitis B suggests a potential role for this protein in liver disease progression

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