Ramaswami Bala, Popescu Iulia, Macedo Camila, Luo Chunqing, Shapiro Ron, Metes Diana, Chalasani Geetha, Randhawa Parmjeet S
Division of Transplant Pathology, Department of Pathology, University of Pittsburgh, Pittsburgh, PA 15213, USA.
Clin Vaccine Immunol. 2011 May;18(5):815-24. doi: 10.1128/CVI.00487-10. Epub 2011 Mar 2.
BK virus (BKV) nephropathy and hemorrhagic cystitis are increasingly recognized causes of disease in renal and hematopoietic stem cell transplant recipients, respectively. Functional characterization of the immune response to BKV is important for clinical diagnosis, prognosis, and vaccine design. A peptide mix (PepMix) and overlapping (OPP) or random (RPP) peptide pools derived from BKV large T antigen (LTA) were used to restimulate 14-day-expanded peripheral blood mononuclear cells (PBMC) from 27 healthy control subjects in gamma interferon (IFN-γ)-specific enzyme-linked immunospot (ELISPOT) assays. A T-cell response to LTA PepMix was detected in 15/27 subjects. A response was frequently observed with peptides derived from the helicase domain (9/15 subjects), while the DNA binding and host range domains were immunologically inert (0/15 subjects). For all nine subjects who responded to LTA peptide pools, the immune response could be explained largely by a 15-mer peptide designated P313. P313-specific CD4(+) T-cell clones demonstrated (i) stringent LTA peptide specificity; (ii) promiscuous recognition in the context of HLA-DR alleles; (iii) cross recognition of homologous peptides from the polyomavirus simian virus 40 (SV40); (iv) an effector memory phenotype, CD107a expression, and intracellular production of IFN-γ and tumor necrosis factor alpha (TNF-α); (v) cytotoxic activity in a chromium release assay; and (vi) the ability to directly present cognate antigen to autologous T cells. In conclusion, T-cell-mediated immunity to BKV in healthy subjects is associated with a polyfunctional population of CD4(+) T cells with dual T-helper and T-cytotoxic properties. HLA class II promiscuity in antigen presentation makes the targeted LTA peptide sequence a suitable candidate for inclusion in immunotherapy protocols.
BK病毒（BKV）肾病和出血性膀胱炎分别日益被认为是肾移植和造血干细胞移植受者发病的原因。对BKV免疫反应的功能特性分析对于临床诊断、预后评估和疫苗设计至关重要。在γ干扰素（IFN-γ）特异性酶联免疫斑点（ELISPOT）试验中，使用源自BKV大T抗原（LTA）的肽混合物（PepMix）以及重叠（OPP）或随机（RPP）肽库，对27名健康对照者经14天扩增的外周血单个核细胞（PBMC）进行再刺激。在27名受试者中，有15名检测到对LTA PepMix的T细胞反应。经常观察到对源自解旋酶结构域的肽有反应（9/15名受试者），而DNA结合结构域和宿主范围结构域在免疫方面无活性（0/15名受试者）。对于所有九名对LTA肽库有反应的受试者，免疫反应很大程度上可由一种名为P313的15聚体肽来解释。P313特异性CD4(+) T细胞克隆表现出：（i）严格的LTA肽特异性；（ii）在HLA-DR等位基因背景下的混杂识别；（iii）对多瘤病毒猴病毒40（SV40）同源肽的交叉识别；（iv）效应记忆表型、CD107a表达以及IFN-γ和肿瘤坏死因子α（TNF-α）的细胞内产生；（v）在铬释放试验中的细胞毒性活性；以及（vi）直接将同源抗原呈递给自体T细胞的能力。总之，健康受试者中对BKV的T细胞介导免疫与具有双重辅助性T细胞和细胞毒性T细胞特性的多功能CD4(+) T细胞群体相关。抗原呈递中HLA II类分子的混杂性使得靶向的LTA肽序列成为免疫治疗方案中合适的候选物。
