Agrawal Lokesh, Lu Xihua, Qingwen Jin, VanHorn-Ali Zainab, Nicolescu Ioan Vlad, McDermott David H, Murphy Philip M, Alkhatib Ghalib
Department of Microbiology and Immunology and Walther Oncology Center, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA.
J Virol. 2004 Mar;78(5):2277-87. doi: 10.1128/jvi.78.5.2277-2287.2004.
CCR5Delta32 is a loss-of-function mutation that abolishes cell surface expression of the human immunodeficiency virus (HIV) coreceptor CCR5 and provides genetic resistance to HIV infection and disease progression. Since CXCR4 and other HIV coreceptors also exist, we hypothesized that CCR5Delta32-mediated resistance may be due not only to the loss of CCR5 function but also to a gain-of-function mechanism, specifically the active inhibition of alternative coreceptors by the mutant CCR5Delta32 protein. Here we demonstrate that efficient expression of the CCR5Delta32 protein in primary CD4(+) cells by use of a recombinant adenovirus (Ad5/Delta32) was able to down-regulate surface expression of both wild-type CCR5 and CXCR4 and to confer broad resistance to R5, R5X4, and X4 HIV type 1 (HIV-1). This may be important clinically, since we found that CD4(+) cells purified from peripheral blood mononuclear cells of individuals who were homozygous for CCR5Delta32, which expressed the mutant protein endogenously, consistently expressed lower levels of CXCR4 and showed less susceptibility to X4 HIV-1 isolates than cells from individuals lacking the mutation. Moreover, CD4(+) cells from individuals who were homozygous for CCR5Delta32 expressed the mutant protein in five of five HIV-exposed, uninfected donors tested but not in either of two HIV-infected donors tested. The mechanism of inhibition may involve direct scavenging, since we were able to observe a direct interaction of CCR5 and CXCR4 with CCR5Delta32, both by genetic criteria using the yeast two-hybrid system and by biochemical criteria using the coimmunoprecipitation of heterodimers. Thus, these results suggest that at least two distinct mechanisms may account for genetic resistance to HIV conferred by CCR5Delta32: the loss of wild-type CCR5 surface expression and the generation of CCR5Delta32 protein, which functions as a scavenger of both CCR5 and CXCR4.
CCR5Delta32是一种功能丧失性突变，它消除了人类免疫缺陷病毒（HIV）共受体CCR5的细胞表面表达，并为HIV感染和疾病进展提供了遗传抗性。由于CXCR4和其他HIV共受体也存在，我们推测CCR5Delta32介导的抗性可能不仅归因于CCR5功能的丧失，还归因于一种功能获得机制，特别是突变型CCR5Delta32蛋白对替代共受体的主动抑制。在此我们证明，通过使用重组腺病毒（Ad5/Delta32）在原代CD4(+)细胞中高效表达CCR5Delta32蛋白，能够下调野生型CCR5和CXCR4的表面表达，并赋予对R5、R5X4和X4型1型人类免疫缺陷病毒（HIV-1）的广泛抗性。这在临床上可能很重要，因为我们发现，从CCR5Delta32纯合个体的外周血单核细胞中纯化的CD4(+)细胞，其内生性表达突变蛋白，与缺乏该突变的个体的细胞相比，CXCR4表达水平始终较低，并且对X4型HIV-1分离株的敏感性较低。此外，在测试的5名暴露于HIV但未感染的供体中，有5名CCR5Delta32纯合个体的CD4(+)细胞表达了突变蛋白，但在测试的2名HIV感染供体中均未表达。抑制机制可能涉及直接清除，因为我们能够通过使用酵母双杂交系统的遗传标准以及通过使用异二聚体的共免疫沉淀的生化标准，观察到CCR5和CXCR4与CCR5Delta32的直接相互作用。因此，这些结果表明，至少有两种不同的机制可能解释CCR5Delta32赋予的对HIV的遗传抗性：野生型CCR5表面表达的丧失以及CCR5Delta32蛋白的产生，该蛋白作为CCR5和CXCR4的清除剂发挥作用。
