Bernard N F, Pederson K, Chung F, Ouellet L, Wainberg M A, Tsoukas C M
Immunodeficiency Treatment Centre, Montreal General Hospital, Quebec, Canada.
AIDS. 1998 Nov 12;12(16):2125-39. doi: 10.1097/00002030-199816000-00007.
CD8+ T-cell counts usually increase soon after infection with HIV, whereas CD4+ cell counts decrease. The result of these changes in T-cell subpopulation subsets in most HIV-infected subjects is inversion of the CD4 : CD8 ratio from greater than 1.0 typical of uninfected persons to less than 1.0 after infection.
Six HIV-infected individuals were identified in whom the CD4 : CD8 ratio remained normal throughout follow-up (4.0-11.25 years). They all maintained levels of CD4+ cells above 500 x 10(6)/l and had never received antiretroviral therapy. Because HIV-specific cytotoxic T lymphocytes (CTL) have been implicated in control of HIV during the asymptomatic phase of disease, we screened these individuals for the presence of HIV-specific CTL activity.
CTL activity was assessed in freshly isolated peripheral blood mononuclear cells (PBMC) and in phytohaemagglutinin-stimulated interleukin-2 expanded cell lines established from PBMC. Cytotoxicity to HIV-1 env, gag, pol and nef gene products was surveyed in a 4 h 51Cr-release assay using autologous Epstein-Barr virus (EBV) transformed B cells infected with vaccinia constructs expressing each of these HIV genes. The immunodominant CTL epitope and MHC class I antigen restriction specificity of HIV-specific CTL was mapped when present. Plasma viral load was assessed by branched DNA assay. Attempts were made to isolate virus from these individuals by the PBMC coculture assay.
None of the six immunologically normal HIV-infected (INHI) subjects exhibited direct HIV-specific CTL activity in their freshly isolated PBMC compared with 16 (47%) out of 34 HIV disease progressors (P = 0.03, chi2 test) and one out of 10 seronegative subjects. Three of the six INHI subjects had detectable memory HIV-specific precursor CTL (pCTL) activity in in vitro-activated T-cell lines compared with 25 (73.5%) out of 34 HIV-1 disease progressors and in none out of 10 seronegative individuals. All three INHI subjects had Gag-specific pCTL, and none had reverse transcriptase-specific pCTL. Plasma HIV viraemia in all six INHI subjects was below the level of detection by branched DNA assay (< 500 copies/ml). Virus could not be isolated from four of these individuals despite multiple attempts to do so by PBMC coculture assays.
Direct HIV-specific CTL activity mediated by activated circulating PBMC was undetectable in six INHI individuals under conditions where it is frequently observed in HIV disease progressors. Despite the absence of cells activated for killing HIV-infected targets in the circulation of these individuals, they appeared able to control their HIV infection by maintaining normal levels of CD4 and CD8 cells and low viral load.
感染HIV后，CD8+ T细胞计数通常会在短期内增加，而CD4+细胞计数则会下降。在大多数HIV感染患者中，T细胞亚群的这些变化导致CD4:CD8比值从未感染者典型的大于1.0倒置为感染后的小于1.0。
确定了6名HIV感染个体，他们在整个随访期间（4.0 - 11.25年）CD4:CD8比值保持正常。他们的CD4+细胞水平均维持在500×10⁶/L以上，且从未接受过抗逆转录病毒治疗。由于HIV特异性细胞毒性T淋巴细胞（CTL）在疾病无症状期对HIV的控制中发挥作用，我们对这些个体进行了HIV特异性CTL活性检测。
在新鲜分离的外周血单核细胞（PBMC）以及从PBMC建立的经植物血凝素刺激的白细胞介素-2扩增细胞系中评估CTL活性。使用感染了表达这些HIV基因的痘苗构建体的自体EB病毒（EBV）转化B细胞，通过4小时⁵¹Cr释放试验检测对HIV-1 env、gag、pol和nef基因产物的细胞毒性。若存在HIV特异性CTL，绘制其免疫显性CTL表位和MHC I类抗原限制特异性图谱。通过分支DNA检测评估血浆病毒载量。尝试通过PBMC共培养试验从这些个体中分离病毒。
与34名HIV疾病进展者中的16名（47%）（P = 0.03，卡方检验）以及10名血清阴性个体中的1名相比，6名免疫功能正常的HIV感染（INHI）个体在其新鲜分离的PBMC中均未表现出直接的HIV特异性CTL活性。6名INHI个体中有3名在体外激活的T细胞系中具有可检测到的记忆性HIV特异性前体CTL（pCTL）活性，而34名HIV-1疾病进展者中有25名（73.5%）具有该活性，10名血清阴性个体中则无一例有此活性。所有3名INHI个体均有Gag特异性pCTL，无一例有逆转录酶特异性pCTL。所有6名INHI个体的血浆HIV病毒血症均低于分支DNA检测的检测水平（<500拷贝/ml）。尽管通过PBMC共培养试验多次尝试，仍有4名个体无法分离出病毒。
在HIV疾病进展者中经常观察到的条件下，6名INHI个体的活化循环PBMC介导的直接HIV特异性CTL活性未被检测到。尽管这些个体的循环中不存在被激活以杀伤HIV感染靶标的细胞，但他们似乎能够通过维持CD4和CD8细胞的正常水平以及低病毒载量来控制HIV感染。
