T-cell repertoire diversity of virus-specific CD8 T-cells

Isabelle MICONNET

T-cells, particularly CD8 T-cells, play a crucial role in antiviral immunity. In the context of HIV infection, their presence even in large numbers is not sufficient to control infection indicating that qualitative criteria of the CD8 T-cell response are correlated with virus control and protection. In this regard, more and more studies over the past few years have aimed at a comprehensive characterization of virus-specific T-cells in order to determine whether certain signatures in the immune response emerging upon chronic viral infection are associated with effective virus control and whether they correspond to the immune correlates of protective antiviral T-cell immunity.

Whereas the functional features of virus-specific CD8 T-cell response was extensively explored, the structural characterization of the T-cell repertoire emerging upon virus infection was poorly addressed in vivo. The adaptive immune T-cell response has evolved to generate a large number of T-cells able to recognize diverse antigenic epitopes through T cell receptor (TCR). The T-cell repertoire is potentially extremely diverse as a consequence of the combinatorial rearrangement of TCR genes and to the imprecise recombination during these rearrangements. Despite its potential diversity, the T-cell repertoire emerging in response to antigenic stimulation is restricted. Independently of Ag selection, mechanisms involved during thymic selection contribute to limit the T cell-repertoire diversity.

In addition, T-cell repertoire restriction upon viral stimulation was reported in several occasions. However, the idea of T-cell repertoire narrowing upon virus infection is not consensual rendering difficult to delineate the role of TCR repertoire diversity in virus control.

The uncertain degree of diversity of the T-cell repertoire elicited during chronic virus infection might be related to the experimental strategy consisting in most studies to analyze the TCR usage within T-cell lines and/or clones obtained in vitro and derived mainly from a limited number of subjects.  Our present objective is to revisit the degree of clonal diversity of the CD8 T-cell response against chronic viral infections. For that purpose, we have chosen to analyze virus-specific T-cells isolated ex vivo by a multi-step strategy. This strategy involves: a) sorting of virus-specific peptide/MHCI multimer⁺ CD8 T-cell populations, b) PCR analysis of TRBV usage within the sorted virus-specific CD8 T-cells, c) analysis of the CDR3 junction length by spectratyping and d) sequence analysis of CDR3 junctions in the TRBV families contained within the virus-specific CD8 T-cells. The T-cell repertoire diversity in response to CMV, EBV and HIV infections is addressed.

Preliminary data revealed an unexpected diversity of the CD8 T-cell repertoires emerging upon CMV, EBV and HIV chronic viral infections.

Dernière modification le 04.05.2010 - Impressum - Informations juridiques