La infección persistente por el virus de la hepatitis C (VHC) altera la reactividad de las células citotóxicas VHC específicas mediante el desequilibrio entre Mcl-1 y Bim debido a la disminución de la expresión de CD127

  1. Lokhande, Megha Uttam
Supervised by:
  1. Juan Ramón Larrubia Marfil Director

Defence university: Universidad de Alcalá

Fecha de defensa: 17 July 2013

Committee:
  1. Agustín Albillos Martínez Chair
  2. Melchor Álvarez de Mon Soto Secretary
  3. Conrado M. Fernández Rodriguez Committee member
  4. José Antonio Solis Herrero Committee member
  5. José María Ladero Quesada Committee member

Type: Thesis

Abstract

Background: In persistent hepatitis C virus (HCV) infection, HCV-specific cytotoxic T lymphocyte (CTL) reactivity is impaired and this affects HCV control. Interleukin-7 receptor (CD127) expression on these cells could regulate CTL reactivity through Mcl-1/Bim balance modulation. Bim is a proapoptotic molecule blocked by the action of Mcl-1. Mcl-1/Bim expression and T cell reactivity on HCV-specific CTLs were compared according to CD127 phenotype. Materials and Methods: Peripheral blood lymphocytes (PBL) from HLA-A2+ HCV+ patients were obtained. HCV-specific CTLs were visualized by staining PBL with anti-CD8 and HLA-A2/peptide pentameric complexes (pentamer). Mcl-1/Bim/CD127/IFN-! phenotype of HCV-specific CTLs was tested by staining detectable CD8+/pentamer+ cells with anti-Mcl-1/Bim/CD127/IFN-! antibodies. HCV-specific CTL proliferation ability after specific in vitro challenge was tested in the presence and absence of pancaspase inhibitor z-VAD-fmk. All stained cells were analyzed by flow cytometry. Results: CD127low-expressing HCV-specific CTLs associated with high HCV viraemia, while CD127high correlated with undetectable viral loads (P < 0.001). Directly ex vivo, pentamer+ cell frequency was similar according to CD127 expression level. Nevertheless, CD127low pentamer+ cell proliferation after specific in vitro challenge was impaired (P < 0.05), although this was corrected by z-VAD-fmk treatment (P < 0.05). Mcl-1 expression was low directly ex vivo (P < 0.01), and Bim was up regulated after antigen encounter (P < 0.05) of CD127low pentamer+ cells. The ex vivo difference between Mcl-1 and Bim expression on pentamer+ cells correlated positively with CD127 expression level (P < 0.001) and with pentamer+ cell reactivity (P < 0.05). The frequency directly ex vivo of IFN-!-producing pentamer+ cells was lower in CD127low group than in CD127high group (P<0.05). Conclusion: A low ex vivo Mcl-1 expression and Bim up-regulation after antigen encounter are involved in CD127low HCV-specific CTL hyporeactivity during chronic infection, but it can be overcome by apoptosis blockade.