Recognition of Homo- and Heterosubtypic Variants of Influenza A Viruses by Human CD8+ T Lymphocytes

Abstract

In the present study, the recognition of epitope variants of influenza A viruses by human CTL was investigated. To this end, human CD8+ CTL clones, specific for natural variants of the HLA-B*3501-restricted epitope in the nucleoprotein (NP418–426), were generated. As determined in 51Cr release assays and by flow cytometry with HLA-B*3501-peptide tetrameric complexes, CTL clones were found to be specific for epitopes within one subtype or cross-reactive with heterosubtypic variants of the epitope. Using eight natural variants of the epitope, positions in the 9-mer important for T cell recognition and involved in escape from CTL immunity were identified and visualized using multidimensional scaling. It was shown that positions 4 and 5 in the 9-mer epitope were important determinants of T cell specificity. The in vivo existence of CD8+ cells cross-reactive with homo- and heterosubtypic variants of the epitope was further confirmed using polyclonal T cell populations obtained after stimulation of PBMC with different influenza A viruses. Based on the observed recognition patterns of the clonal and polyclonal T cell populations and serology, it is hypothesized that consecutive infections with influenza viruses containing different variants of the epitope select for cross-reactive T cells in vivo.

Preexisting CD8 + T-cell immunity to the H7N9 influenza A virus varies across ethnicities

“…S3). Indeed, the H7N9 variant of the immunodominant NP 418 peptides presented by the large B7 family (15,16) was identical to that within the 1918-H1N1 virus and closely resembled that from H1N1pdm-2009 (Table S4). In agreement with our previous data (16), this H7N9-NP 418 variant is not recognized by memory CTL specific for the various seasonal influenza types from the last decades (Fig.…”

“…We then examined CTL responses to the antigenic peptides unique to the H7N9 virus (Table S3). Although human populations that have not previously encountered H7N9 would likely see these pHLA1s as novel, there is also the possibility that there could be some "plasticity" in the cross-recognition of antigenic variants (15,16).…”

Cytotoxic T Lymphocytes Established by Seasonal Human Influenza Cross-React against 2009 Pandemic H1N1 Influenza Virus

“…Since there is a very low frequency of influenza virus-specific T cells in human peripheral blood, most studies have used IFN-␥ responses to investigate the cross-reactive T-cell responses or have used influenza virus peptide-pulsed cell lines or cell lines in which HA, NA, and M proteins are expressed as target cells to determine the cross-reactive CTLs of in vitroexpanded CD8 T-cell lines (5,23,29,51). However, these assays have some limitations.…”

“…Cross-reactivity of influenza A virus-specific T-cell immunity against heterosubtypic strains which are serologically distinct has been demonstrated (5,29,33,47). Humans who have not been exposed to avian influenza A (H5N1) virus do have crossreactive memory CD4 and CD8 T cells to a wide range of H5N1 peptides (33,47).…”

Preemptive priming readily overcomes structure-based mechanisms of virus escape

“…With influenza, although mutations have been found for >70% of immunogenic T-cell peptides (7), this finding has received little attention because of the acute nature of the disease. Even so, such escape mutants are readily generated using TCR transgenic mice (11), and "natural" variants occur within the influenza nucleoprotein (NP) 380 (HLA-B8), NP 383 (HLA-B27), and NP 418 (HLA-B35) viral peptides (12)(13)(14). Furthermore, given sufficient immune pressure and relative fitness, such mutated viruses can become fixed in the population, leading to the disappearance of WT T-cell specificities (15).…”