Defining the directionality and quality of influenza virus–specific CD8+ T cell cross-reactivity in individuals infected with hepatitis C virus

Abstract

Cross-reactivity of murine and recently human CD8 + T cells between different viral peptides, i.e., heterologous immunity, has been well characterized. However, the directionality and quality of these cross-reactions is critical in determining their biological importance. Herein we analyzed the response of human CD8 + T cells that recognize both a hepatitis C virus peptide (HCV-NS3) and a peptide derived from the influenza neuraminidase protein (Flu-NA). To detect the cross-reactive CD8 + T cells, we used peptide-MHC class I complexes (pMHCs) containing a new mutant form of MHC class I able to bind CD8 more strongly than normal MHC class I complexes. T cell responses against HCV-NS3 and Flu-NA peptide were undetectable in normal donors. In contrast, some responses against the Flu-NA peptide were identified in HCV + donors who showed strong HCV-NS3-specific reactivity. The Flu-NA peptide was a weak agonist for CD8 + T cells in HCV + individuals on the basis of novel pMHCs and functional assays. These data support the idea of cross-reactivity between the 2 peptides, but indicate that reactivity toward the Flu-NA peptide is highly CD8-dependent and occurs predominantly after priming during HCV infection. Our findings indicate the utility of the novel pMHCs in dissecting cross-reactivity and suggest that cross-reactivity between HCV and influenza is relatively weak. Further studies are needed to relate affinity and functionality of cross-reactive T cells.

Detection of low avidity CD8+ T cell populations with coreceptor-enhanced peptide-major histocompatibility complex class I tetramers

“…Together with coreceptor-null pMHCI tetramers (Laugel et al, 2007; Pittet et al, 2003; Choi et al, 2003; Price et al, 2005; Purbhoo et al, 2001), these reagents allow for the rigorous physical assessment of antigen avidities within CD8 + T cell populations of defined specificity. Thus, despite the caveats elucidated above, it seems likely that the ability to detect low avidity CD8 + T cells will prove useful for the full evaluation of antigen-specific immune responses in several settings; these include auto-immune conditions, tumor immunity, heterologous phenomena and lymphopenic situations in which low avidity T cells expand during the process of homeostatic reconstitution (Goldrath and Bevan, 1999; Cho et al, 2000; Krupica et al, 2006; Selin et al, 2006; Kasprowicz et al, 2008). …”

Age-Associated Increase of Low-Avidity Cytomegalovirus-Specific CD8+ T Cells That Re-Express CD45RA

“…Occasionally cells were also stained with either Live/Dead Fixable Blue Dead Cell Stain (Invitrogen, Paisley, UK) or BD Via-Probe (BD Biosciences). Tetramer staining was conducted on HLA matched donor PBMCs for 20 mins at 37°C with either HLA-A*0201 (NLVPMVATV) or HLA-B*0701 (TPRVTGGGAM) CMVpp65-specific conventional tetramers or “null” tetramers that have been mutated in the α3 domain in the conserved binding site for CD8 as previously described (18). Conventional tetramers identify all specific CD8 + T cells that are able to bind specific peptide whilst the null tetramers identify CD8 + T cells that have high avidity for specific peptide without the need for CD8 binding.…”

“…In this study we show that the expanded CMV-specific CD8 + T cell population specific for a HLA-A*0201 restricted epitope (NLV) of the immunodominant pp65CMV protein can show either high or low avidity, as identified by tetramers that have been mutated in their MHC binding domain for CD8 (16-18). This low avidity population accumulates in older subjects, preferentially expresses CD45RA and have reduced functional responses to antigen specific stimulation compared to their high avidity CD45RO expressing counterparts.…”

Cross-Reactivity of T Cells and Its Role in the Immune System

“…63,67,70,73,74,77,78 Estimates of cross-reactivity of known clones can be up to 10 6 different peptides. 6,72 At the same time, several reports have indicated an extremely low frequency of cross-reactions between unrelated peptides.…”