The CXCR4 molecules of both marmosets and squirrel monkeys supported HIV-1 infection, but the CCR5 proteins of both species were only marginally functional.
Stromal cell-derived factor 1 (SDF1), the ligand of the CXCR4 receptor, is a CXC chemokine involved in chemotaxis and brain development that also acts as coreceptor for HIV-1 infection.
These proof-of-concept studies demonstrated the efficacy of an siRNA targeted to an essential cellular coreceptor CXCR4 in protecting from HIV-1 infection.
These results indicated that these CXCR4-antisense expressing cells could resist T-tropic HIV-1 infection and could retain normal biological functions.
HIV-1 infection through CCR5 and CXCR4 receptors can thus be prevented in the absence of steric hindrance or receptor downregulation by acting in trans on a receptor that is rarely used by the virus to infect cells.
The finding is relevant as regards the fact that SDF1-3'A polymorphism induces an increase of SDF1 chemokine production, in which it competes with HIV-1 in binding to CXCR4 receptor, and in turn inhibits HIV-1 infection.
Down regulation of CCR5 and CXCR4 after HIV-1 infection could be the result of indirect events linked to HIV-1 infection, such as the induction of alpha- or beta-chemokines competing with the virions for receptor binding.
This approach was utilized to inhibit human immunodeficiency virus type I (HIV-1) infection in human cells. siRNAs with homology to a motif in the mRNA that encodes for the HIV-1 chemokine coreceptor CXCR4 was utilized.
Exposed seronegative individuals (ES) with persistent high-risk sexual behavior may be less susceptible to human immunodeficiency virus type 1 (HIV-1) infection because they carry the chemokine receptor (CR) gene alleles CCR5 open reading frame (ORF) Delta32, CCR5 promoter -2459G, or CCR2 ORF 64I (CCR2-64I), all of which have been found to diminish HIV-1 infectivity and/or disease progression.
This study analyzed the SDF1-3'A SNP and performed mutation screening for polymorphic markers in the CXCR4 gene to determine the presence or absence of significant associations with susceptibility to HIV-1 infection.
Thus, CXCR4 can differ both structurally and functionally between cells, with HIV-1 infection and chemotaxis apparently mediated by different isoforms.
Since the discovery of the 32-base-pair deletion in the CCR5 chemokine receptor gene (CCR5-Delta32) and its effect on HIV-1 infection and AIDS progression, many genetic factors affecting AIDS have been identified.
A single nucleotide polymorphism (SNP) in SDF-1, the natural ligand for the HIV-1 coreceptor CXCR4, is implicated to have protective effects against HIV-1 infection.
CXCR4 is a frequent alternative coreceptor (CoR) in subtype B and D HIV-1 infection, but the importance of many other alternative CoRs remains elusive.
HIV-1 can use various G protein-coupled receptors (GPCRs) in addition to CCR5 and CXCR4 as coreceptors; however, this type of HIV-1 infection has hardly been detected in vivo.
Therefore, we propose that activated moesin promotes F-actin redistribution and CD4-CXCR4 clustering and is also required for efficient X4-tropic HIV-1 infection in permissive lymphocytes.