Kan-Mitchell June, Bajcz Melissa, Schaubert Keri L, Price David A, Brenchley Jason M, Asher Tedi E, Douek Daniel C, Ng Hwee L, Yang Otto O, Rinaldo Charles R, Benito Jose Miguel, Bisikirska Brygida, Hegde Ramakrishna, Marincola Franco M, Boggiano César, Wilson Dianne, Abrams Judith, Blondelle Sylvie E, Wilson Darcy B
Karmanos Cancer Institute, Wayne State University School of Medicine, Detroit, MI 48201, USA.
J Immunol. 2006 Jun 1;176(11):6690-701. doi: 10.4049/jimmunol.176.11.6690.
CD8+ CTL responses are important for the control of HIV-1 infection. The immunodominant HLA-A2-restricted Gag epitope, SLYNTVATL (SL9), is considered to be a poor immunogen because reactivity to it is rare in acute infection despite its paradoxical dominance in patients with chronic infection. We have previously reported SL9 to be a help-independent epitope in that it primes highly activated CTLs ex vivo from CD8+ T cells of seronegative healthy donors. These CTLs produce sufficient cytokines for extended autocrine proliferation but are sensitive to activation-induced cell death, which may cause them to be eliminated by a proinflammatory cytokine storm. Here we identified an agonist variant of the SL9 peptide, p41 (SLYNTVAAL), by screening a large synthetic combinatorial nonapeptide library with ex vivo-primed SL9-specific T cells. p41 invariably immunized SL9-cross-reactive CTLs from other donors ex vivo and H-2Db beta2m double knockout mice expressing a chimeric HLA-A*0201/H2-Db MHC class I molecule. Parallel human T cell cultures showed p41-specific CTLs to be less fastidious than SL9-CTLs in the level of costimulation required from APCs and the need for exogenous IL-2 to proliferate (help dependent). TCR sequencing revealed that the same clonotype can develop into either help-independent or help-dependent CTLs depending on the peptide used to activate the precursor CD8+ T cells. Although Ag-experienced SL9-T cells from two patients were also sensitive to IL-2-mediated cell death upon restimulation in vitro, the loss of SL9 T cells was minimized with p41. This study suggests that agonist sequences can replace aberrantly immunogenic native epitopes for the rational design of vaccines targeting HIV-1.
CD8 + 细胞毒性T淋巴细胞（CTL）反应对于控制HIV - 1感染很重要。免疫显性的HLA - A2限制性Gag表位SLYNTVATL（SL9）被认为是一种较差的免疫原，因为尽管它在慢性感染患者中具有矛盾的优势，但在急性感染中对其的反应性很少见。我们之前报道过SL9是一种不依赖辅助的表位，因为它能在体外从血清阴性健康供体的CD8 + T细胞中诱导出高度活化的CTL。这些CTL产生足够的细胞因子用于长时间的自分泌增殖，但对活化诱导的细胞死亡敏感，这可能导致它们被促炎细胞因子风暴清除。在这里，我们通过用体外诱导的SL9特异性T细胞筛选一个大型合成组合九肽文库，鉴定出了SL9肽的激动剂变体p41（SLYNTVAAL）。p41在体外能始终如一地免疫来自其他供体的SL9交叉反应性CTL以及表达嵌合HLA - A*0201/H2 - Db MHC I类分子的H - 2Db β2m双敲除小鼠。平行的人类T细胞培养显示，p41特异性CTL在抗原呈递细胞（APC）所需的共刺激水平以及增殖所需的外源性白细胞介素 - 2（依赖辅助）方面比SL9 - CTL要求更低。TCR测序显示，根据用于激活前体CD8 + T细胞的肽段不同，相同的克隆型可以发育成不依赖辅助或依赖辅助的CTL。虽然来自两名患者的经历过抗原刺激的SL9 - T细胞在体外再次刺激时也对IL - 2介导的细胞死亡敏感，但用p41可使SL9 T细胞的损失最小化。这项研究表明，激动剂序列可以替代异常免疫原性的天然表位，用于合理设计针对HIV - 1的疫苗。
