Table_5_Role of cross-reactivity in cellular immune targeting of influenza A M158-66 variant peptide epitopes.docx

The immunologic significance of cross-reactivity of TCR recognition of peptide:MHC complexes is still poorly understood. We have described TCR cross-reactivity in a system involving polyclonal CD8 T cell recognition of the well characterized influenza viral M158-66 epitope. While M158-66 is generally conserved between influenza A isolates, error-prone transcription generates stable variant RNA during infection which could act as novel epitopes. If packaged and viable, variant genomic RNA generates an influenza quasispecies. The stable RNA variants would generate a new transmissible epitope that can select a specific repertoire, which itself should have cross-reactive properties. We tested two candidate peptides in which Thr65 is changed to Ala (A65) or Ser (S65) using recall responses to identify responding T cell clonotypes. Both peptides generated large polyclonal T cell repertoires of their own with repertoire characteristics and cross-reactivity patterns like that observed for the M158-66 repertoire. Both substitutions could be present in viral genomes or mRNA at sufficient frequency during an infection to drive immunity. Peptides from the resulting protein would be a target for CD8 cells irrespective of virus viability or transmissibility. These data support the hypothesis that cross-reactivity is important for immunity against RNA virus infections.

T细胞受体（TCR）识别肽-主要组织相容性复合体（MHC）复合物的交叉反应性的免疫学意义，目前仍未被充分阐明。本研究团队此前已在相关体系中报道了TCR的交叉反应性，该体系涉及多克隆CD8 T细胞对特征明确的流感病毒M158-66表位的识别。尽管M158-66表位在甲型流感分离株之间通常保守，但感染过程中易错转录会产生稳定的变异RNA，这类变异RNA可作为新型表位。若变异基因组RNA被包裹且具备感染活性，则会形成流感准种。这些稳定的RNA变异体将产生一种新的可传播表位，该表位可筛选出特定的T细胞受体库，而该受体库本身应具备交叉反应性特征。本研究通过回忆应答实验，检测了两种候选肽段——其中第65位苏氨酸分别突变为丙氨酸（A65）或丝氨酸（S65），以鉴定产生应答的T细胞克隆型。两种肽段均可各自诱导产生庞大的多克隆T细胞受体库，其受体库特征与交叉反应模式均与M158-66诱导的受体库相似。在感染过程中，这两种氨基酸替换可在病毒基因组或mRNA中以足够高的频率出现，从而驱动免疫应答。无论病毒是否具备感染活性或传播能力，其编码蛋白衍生的肽段均可成为CD8 T细胞的识别靶点。上述数据支持以下假说：交叉反应性对于抗RNA病毒感染的免疫应答至关重要。