Department of Paediatrics, University of Oxford, Oxford, United Kingdom
Department of Biotechnology, National Centre for Disease Control, Delhi, India.
J Virol. 2020 Jun 16;94(13). doi: 10.1128/JVI.02025-19.
HLA-B52:01 is strongly associated with protection against HIV disease progression. However, the mechanisms of HLA-B52:01-mediated immune control have not been well studied. We here describe a cohort with a majority of HIV C-clade-infected individuals from Delhi, India, where HLA-B52:01 is highly prevalent (phenotypic frequency, 22.5%). Consistent with studies of other cohorts, expression of HLA-B52:01 was associated with high absolute CD4 counts and therefore a lack of HIV disease progression. We here examined the impact of HLA-B52:01-associated viral polymorphisms within the immunodominant C clade Gag epitope RMTSPVSI (here, RI8; Gag residues 275 to 282) on viral replicative capacity (VRC) since HLA-mediated reduction in VRC is a central mechanism implicated in HLA-associated control of HIV. We observed in HLA-B52:01-positive individuals a higher frequency of V280T, V280S, and V280A variants within RI8 (0.0001). Each of these variants reduced viral replicative capacity in C clade viruses, particularly the V280A variant (0.0001 in both the C clade consensus and in the Indian study cohort consensus p24 Gag backbone), which was also associated with significantly higher absolute CD4 counts in the donors (median, 941.5 cells/mm; 0.004). A second HLA-B52:01-associated mutation, K286R, flanking HLA-B52:01-RI8, was also analyzed. Although selected in HLA-B52:01-positive subjects often in combination with the V280X variants, this mutation did not act as a compensatory mutant but, indeed, further reduced VRC. These data are therefore consistent with previous work showing that HLA-B molecules that are associated with immune control of HIV principally target conserved epitopes within the capsid protein, escape from which results in a significant reduction in VRC. Few studies have addressed the mechanisms of immune control in HIV-infected subjects in India, where an estimated 2.7 million people are living with HIV. We focus here on a study cohort in Delhi on one of the most prevalent HLA-B alleles, HLA-B52:01, present in 22.5% of infected individuals. HLA-B52:01 has consistently been shown in other cohorts to be associated with protection against HIV disease progression, but studies have been limited by the low prevalence of this allele in North America and Europe. Among the C-clade-infected individuals, we show that HLA-B52:01 is the most protective of all the HLA-B alleles expressed in the Indian cohort and is associated with the highest absolute CD4 counts. Further, we show that the mechanism by which HLA-B52:01 mediates immune protection is, at least in part, related to the inability of HIV to evade the HLA-B52:01-restricted p24 Gag-specific CD8 T-cell response without incurring a significant loss to viral replicative capacity.
HLA-B52:01 与 HIV 疾病进展的保护作用密切相关。然而,HLA-B52:01 介导的免疫控制机制尚未得到很好的研究。我们在这里描述了一个主要由来自印度德里的 HIV C 型感染个体组成的队列,其中 HLA-B52:01 高度流行(表型频率为 22.5%)。与其他队列的研究一致,HLA-B52:01 的表达与高绝对 CD4 计数相关,因此缺乏 HIV 疾病进展。在这里,我们研究了免疫显性 C 型 Gag 表位 RMTSPVSI(此处为 RI8;Gag 残基 275 至 282)内 HLA-B52:01 相关病毒多态性对病毒复制能力(VRC)的影响,因为 HLA 介导的 VRC 降低是 HLA 相关 HIV 控制中涉及的中心机制。我们在 HLA-B52:01 阳性个体中观察到 RI8 内 V280T、V280S 和 V280A 变体的更高频率(0.0001)。这些变体都降低了 C 型病毒的病毒复制能力,特别是 V280A 变体(在 C 型共识和印度研究队列共识 p24 Gag 骨架中均为 0.0001),这也与供体中显著更高的绝对 CD4 计数相关(中位数为 941.5 个细胞/mm;0.004)。第二个 HLA-B52:01 相关突变,K286R,位于 HLA-B52:01-RI8 侧翼,也进行了分析。尽管 K286R 突变通常与 V280X 变体一起选择,出现在 HLA-B52:01 阳性个体中,但它不作为补偿性突变,实际上进一步降低了 VRC。这些数据与之前的研究一致,表明与 HIV 免疫控制相关的 HLA 分子主要针对衣壳蛋白中的保守表位,逃避这些表位会导致 VRC 显著降低。很少有研究探讨印度 HIV 感染个体的免疫控制机制,据估计,印度有 270 万人感染了 HIV。我们在这里关注的是德里的一个研究队列,研究的是在 22.5%的感染个体中存在的最常见的 HLA-B 等位基因 HLA-B52:01。在其他队列中,HLA-B52:01 一直被证明与 HIV 疾病进展的保护作用相关,但由于这种等位基因在北美和欧洲的流行率较低,研究受到限制。在 C 型感染个体中,我们表明 HLA-B52:01 是印度队列中所有表达的 HLA-B 等位基因中最具保护性的,与最高的绝对 CD4 计数相关。此外,我们表明,HLA-B52:01 介导免疫保护的机制至少部分与 HIV 无法逃避 HLA-B52:01 限制性 p24 Gag 特异性 CD8 T 细胞反应而不显著降低病毒复制能力有关。