Polymorphisms in the CCR5 genes of African green monkeys and mice implicate specific amino acids in infections by simian and human immunodeficiency viruses

Abstract

CCR5, a receptor for the CC chemokines RANTES, Mip1␣, and Mip1␤, has been identified as a coreceptor for infections by macrophage-tropic isolates of human immunodeficiency virus type 1 (HIV-1). To study its structure and function, we isolated cDNA clones of human, African green monkey (AGM), and NIH/Swiss mouse CCR5s, and we quantitatively analyzed infections by macrophage-tropic HIV-1 and SIV mac251 after transfecting human HeLa-CD4 cells with the CCR5 expression vectors. The AGM and NIH/Swiss mouse CCR5 proteins are 97.7 to 98.3% and 79.8% identical to the human protein, respectively. In addition, we analyzed site-directed mutants and chimeras of these CCR5s. Cell surface expression of CCR5 proteins was monitored by using a specific rabbit antiserum and by binding the chemokine [ 125 I]Mip1␤. Our major results were as follows. (i) Two distinct AGM CCR5 sequences were reproducibly found in DNA from CV-1 cells. The AGM clone 1 CCR5 protein differs from that of clone 2 by two substitutions, Y14N in the amino-terminal extracellular region and L352F at the carboxyl terminus. Interestingly, AGM clone 1 CCR5 was inactive as a coreceptor for all tested macrophage-tropic isolates of HIV-1, whereas AGM clone 2 CCR5 was active. As shown by chimera studies and site-directed mutagenesis, the Y14N substitution in AGM clone 1 CCR5 was solely responsible for blocking HIV-1 infections. In contrast, both AGM CCR5 clones were active coreceptors for SIV mac251. Studies of DNA samples from other AGMs indicated frequent additional CCR5 polymorphisms, and we cloned an AGM clone 2 variant with a Q93R substitution in the extracellular loop 1 from one heterozygote. This variant CCR5 was active as a coreceptor for SIV mac251 but was only weakly active for macrophage-tropic isolates of HIV-1. In addition, SIV mac251 appeared to be dependent on the extracellular amino terminus and loop 2 regions of human CCR5 for maximal infection. Our results suggest major differences in the interactions of SIV mac251 and macrophage-tropic HIV-1 isolates with I9, N13, and Y14 in the amino terminus; with Q93 in extracellular loop 1; and with extracellular loop 2 of human CCR5. (ii) The NIH/Swiss mouse CCR5 protein differs at multiple positions from sequences recently reported for other inbred strains of mice. This CCR5 was inactive as a coreceptor for HIV-1 and SIV mac251. Studies of chimeras that contained different portions of NIH/Swiss mouse CCR5 substituted into human CCR5, as well as the reciprocal chimeras, indicated that the amino-terminal region and extracellular loops 1 and 2 of human CCR5 contribute to its coreceptor activity for macrophage-tropic isolates of HIV-1. Specific differences with previous CCR5 chimera results occurred because the NIH/Swiss mouse CCR5 contains a unique substitution corresponding to P183L in extracellular loop 2 that is nonpermissive for coreceptor activity. We conclude that diverse CCR5 sequences occur in AGMs and mice, that SIV mac251 and macrophage-tropic HIV-1 isolates interact differently with specific CCR5 amino a...

Functional Dissection of CCR5 Coreceptor Function through the Use of CD4-Independent Simian Immunodeficiency Virus Strains

“…It is interesting that the AGM population harbors a CCR5 allele which contains the D13N mutation, which plays an important role in CD4-independent SIV infection (39). Since SIV is thought to have existed in the AGM population for many generations, it has been hypothesized that mutations in CCR5 are likely to occur in regions of CCR5 which limit SIV pathogenicity (39). Interestingly, a separate study found that in four of four sooty mangabeys examined, CCR5 contained the S180P mutation, which we also found to limit CD4-independent virus infection (10).…”

Chemokine Coreceptor Usage by Diverse Primary Isolates of Human Immunodeficiency Virus Type 1

“…Amino acid sequence alignments of CCR5 derived from people of diverse genetic backgrounds show that this chemokine receptor is highly conserved (2,50). Similarly, despite the high frequency of amino acid polymorphism for CCR5 alleles derived from nonhuman primates, including apes, Old World monkeys, New World monkeys, and selected prosimians, we observed amino acid conservation within specific regions, especially within the chemokine receptor ectodomain (4,9,34,43,50). All of these characterized nonhuman primate CCR5 alleles permit primate immunodeficiency virus fusion and entry (34, 35a, 43) and thus likely permit the cross-species transmission of primate immunodeficiency virus (8,47).…”

SIVcpz from a naturally infected Cameroonian chimpanzee: Biological and genetic comparison with HIV‐1 N

“…The ability to replicate in primary human lymphocytes has been observed for other SIVs [11]. In addition, almost all other SIVs studied up to now, including SIVcpz-gabl, also use CCR5 and not CXCR4 [2,7,16]. The exceptions reported so far concern SIVrcm and SIVmind-GB1.…”