Division of Infectious Diseases, Department of Medicine, Geffen School of Medicine, University of California-Los Angeles, Los Angeles, California, USA.
J Virol. 2013 Aug;87(15):8726-34. doi: 10.1128/JVI.01040-13. Epub 2013 Jun 5.
Although CD8(+) cytotoxic T lymphocytes (CTLs) are protective in HIV-1 infection, the factors determining their antiviral efficiency are poorly defined. It is proposed that Gag targeting is superior because of very early Gag epitope presentation, allowing early killing of infected cells before Nef-mediated downregulation of human leukocyte antigen class I (HLA-I). To study Gag epitope presentation kinetics, three epitopes (SL977-85, KF11162-172, and TW10240-249) were genetically translocated from their endogenous location in the Rev-dependent (late) gag gene into the Rev-independent (early) nef gene with concomitant mutation of the corresponding endogenous epitopes to nonrecognized sequences. These viruses were compared to the index virus for CTL-mediated suppression of replication and the susceptibility of this antiviral activity to Nef-mediated HLA-I downregulation. SL9-specific CTLs gained activity after SL9 translocation to Nef, going from Nef sensitive to Nef insensitive, indicating that translocation accelerated infected cell recognition from after to before HLA-I downregulation. KF11-specific CTL antiviral activity was unchanged and insensitive to HLA-I downregulation before and after KF11 translocation, suggesting that already rapid recognition of infected cells was not accelerated. However, TW10-specific CTLs that were insensitive to Nef at the baseline became sensitive with reduced antiviral activity after translocation, indicating that translocation retarded epitope expression. Cytosolic peptide processing assays suggested that TW10 was inefficiently generated after translocation to Nef, compared to SL9 and KF11. As a whole, these data demonstrate that epitope presentation kinetics play an important role in CTL antiviral efficiency, that Gag epitopes are not uniformly presented early, and that the epitope context can play a major role in presentation kinetics.
尽管 CD8(+)细胞毒性 T 淋巴细胞 (CTL) 在 HIV-1 感染中具有保护作用，但决定其抗病毒效率的因素尚未明确。据推测，Gag 靶向优于其他方式，因为 Gag 表位在非常早期就被呈现出来，从而可以在 Nef 下调人白细胞抗原 I 类 (HLA-I) 之前，早期杀死感染细胞。为了研究 Gag 表位呈现动力学，我们将三个表位 (SL977-85、KF11162-172 和 TW10240-249) 从其在 Rev 依赖性 (晚期) gag 基因中的内源位置遗传转移到 Rev 独立性 (早期) nef 基因中，同时将相应的内源性表位突变为非识别序列。我们将这些病毒与指数病毒进行比较，以评估 CTL 介导的复制抑制作用，以及这种抗病毒活性对 Nef 介导的 HLA-I 下调的敏感性。SL9 特异性 CTL 在 SL9 转移到 Nef 后获得活性，从对 Nef 敏感变为对 Nef 不敏感，这表明转移加速了感染细胞在 HLA-I 下调之前的识别。KF11 特异性 CTL 抗病毒活性在 KF11 转移前后均保持不变，且不受 HLA-I 下调的影响，这表明已经快速识别感染细胞的速度没有加快。然而，TW10 特异性 CTL 在基线时对 Nef 不敏感，但在转移后其抗病毒活性降低，变得对 Nef 敏感，这表明转移延迟了表位表达。细胞溶质肽加工测定表明，与 SL9 和 KF11 相比，TW10 在转移到 Nef 后效率较低。总体而言，这些数据表明，表位呈现动力学在 CTL 抗病毒效率中起着重要作用，Gag 表位并非均匀地早期呈现，表位上下文在呈现动力学中可以起到主要作用。
