Foster J L, Anderson S J, Frazier A L, Garcia J V
Department of Biochemistry, University of Tennessee Health Sciences Center, Memphis 38163.
Virology. 1994 Jun;201(2):373-9. doi: 10.1006/viro.1994.1303.
HIV-1 Nef down-modulates expression of human CD4, the human immunodeficiency virus (HIV) receptor, at the cell surface. Down-modulation of retrovirus receptors has been shown to be important in the survival of infected cells. To relate this observation to AIDS pathogenesis, we compared the ability of Nef from the SIVmac239open and HIV-1 SF2 isolates to suppress CD4 surface levels. We first obtained the simian immunodeficiency virus (SIV)nef gene by PCR and cloned it into the retroviral vector pLXSN. We then established high titer (1 x 10(6) CFU/ml) amphotropic retrovirus producer lines (PA317/LSnefSN). Using LSnefSN we obtained populations of CD4+ human and mouse T-cells, human B-cells, and mouse fibroblasts that expressed SIV or HIV Nef. In the two human cell lines, both HIV and SIV Nef expression correlated with a significant decrease in CD4 cell surface levels. However, Nef expression did not alter the cell surface levels of CD3, CD18, and MHC class I. Both Nef proteins also suppressed human CD4 surface expression in mouse fibroblasts. Interestingly, SIV Nef failed to suppress cell surface expression of mouse CD4 under conditions where HIV-1 Nef did. Human CD4 down-modulation is a conserved function of SIV and HIV Nef likely to be important for pathogenesis.
HIV-1 Nef可下调人类免疫缺陷病毒（HIV）受体——人类CD4在细胞表面的表达。逆转录病毒受体的下调在受感染细胞的存活中具有重要作用。为了将这一观察结果与艾滋病发病机制联系起来，我们比较了来自SIVmac239open和HIV-1 SF2分离株的Nef抑制CD4表面水平的能力。我们首先通过聚合酶链反应（PCR）获得猿猴免疫缺陷病毒（SIV）nef基因，并将其克隆到逆转录病毒载体pLXSN中。然后我们建立了高滴度（1×10⁶集落形成单位/毫升）的嗜异性逆转录病毒生产细胞系（PA317/LSnefSN）。使用LSnefSN，我们获得了表达SIV或HIV Nef的CD4⁺人类和小鼠T细胞、人类B细胞以及小鼠成纤维细胞群体。在这两种人类细胞系中，HIV和SIV Nef的表达均与CD4细胞表面水平的显著降低相关。然而，Nef的表达并未改变CD3、CD18和MHC I类分子的细胞表面水平。两种Nef蛋白也均抑制了小鼠成纤维细胞中人类CD4的表面表达。有趣的是，在HIV-1 Nef能够抑制小鼠CD4细胞表面表达的条件下，SIV Nef却未能做到。人类CD4的下调是SIV和HIV Nef的一种保守功能，可能对发病机制具有重要意义。
