Functional impact of HIV coreceptor-binding site mutations

Department of Microbiology, University of Pennsylvania, 225 Johnson Pavilion, 3610 Hamilton Walk, Philadelphia, PA 19104, USA.
Virology (Impact Factor: 3.32). 08/2006; 351(1):226-36. DOI: 10.1016/j.virol.2006.03.017
Source: PubMed


The bridging sheet region of the gp120 subunit of the HIV-1 Env protein interacts with the major virus coreceptors, CCR5 and CXCR4. We examined the impact of mutations in and adjacent to the bridging sheet region of an X4 tropic HIV-1 on membrane fusion and entry inhibitor susceptibility. When the V3-loop of this Env was changed so that CCR5 was used, the effects of these same mutations on CCR5 use were assayed as well. We found that coreceptor-binding site mutations had greater effects on CXCR4-mediated fusion and infection than when CCR5 was used as a coreceptor, perhaps related to differences in coreceptor affinity. The mutations also reduced use of the alternative coreceptors CCR3 and CCR8 to varying degrees, indicating that the bridging sheet region is important for the efficient utilization of both major and minor HIV coreceptors. As seen before with a primary R5 virus strain, bridging sheet mutations increased susceptibility to the CCR5 inhibitor TAK-779, which correlated with CCR5 binding efficiency. Bridging sheet mutations also conferred increased susceptibility to the CXCR4 ligand AMD-3100 in the context of the X4 tropic Env. However, these mutations had little effect on the rate of membrane fusion and little effect on susceptibility to enfuvirtide, a membrane fusion inhibitor whose activity is dependent in part on the rate of Env-mediated membrane fusion. Thus, mutations that reduce coreceptor binding and enhance susceptibility to coreceptor inhibitors can affect fusion and enfuvirtide susceptibility in an Env context-dependent manner.

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Available from: John M Muchiri, Jan 13, 2015
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    • "An interesting observation from our study was the absence of correlation between the infectivity of the recombinant viruses studied and their susceptibility to several different entry inhibitors or neutralizing antibodies. The affinity of Env-coreceptor interactions is one factor that can influence both Env fusion kinetics and the sensitivity of Env to the inhibition by enfuvirtide and TAK-779 [35,36,56,59], although mutations that modify sensitivity to co-receptor antagonists without modifying fusion kinetics have also been described [36,60]. The failure to find a correlation between Env infectivity and sensitivity to these inhibitors suggests that differences affecting membrane fusion that are independent of Env-coreceptor affinity (e.g., "fusogenicity") or differences affecting other Env properties (e.g., the expression or stability of Env trimers) make an important contribution to the wide spectrum of Env infectivities observed in this study. "
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    ABSTRACT: Numerous studies have shown that viral quasi-species with genetically diverse envelope proteins (Env) replicate simultaneously in patients infected with the human immunodeficiency virus type 1 (HIV-1). Less information is available concerning the extent that envelope sequence diversity translates into a diversity of phenotypic properties, including infectivity and resistance to entry inhibitors. To study these questions, we isolated genetically distinct contemporaneous clonal viral populations from the plasma of 5 HIV-1 infected individuals (n = 70), and evaluated the infectivity of recombinant viruses expressing Env proteins from the clonal viruses in several target cells. The sensitivity to entry inhibitors (enfuvirtide, TAK-799), soluble CD4 and monoclonal antibodies (2G12, 48d, 2F5) was also evaluated for a subset of the recombinant viruses (n = 20). Even when comparisons were restricted to viruses with similar tropism, the infectivity for a given target cell of viruses carrying different Env proteins from the same patient varied over an approximately 10-fold range, and differences in their relative ability to infect different target cells were also observed. Variable region haplotypes associated with high and low infectivity could be identified for one patient. In addition, clones carrying unique mutations in V3 often displayed low infectivity. No correlation was observed between viral infectivity and sensitivity to inhibition by any of the six entry inhibitors evaluated, indicating that these properties can be dissociated. Significant inter-patient differences, independent of infectivity, were observed for the sensitivity of Env proteins to several entry inhibitors and their ability to infect different target cells. These findings demonstrate the marked functional heterogeneity of HIV-1 Env proteins expressed by contemporaneous circulating viruses, and underscore the advantage of clonal analyses in characterizing the spectrum of functional properties of the genetically diverse viral populations present in a given patient.
    Retrovirology 02/2008; 5(1):23. DOI:10.1186/1742-4690-5-23 · 4.19 Impact Factor
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    • "It has been shown that an apparent binding affinity between Env and CCR5 correlates with the resistance of fusion to coreceptor binding inhibitors [25,27,28]. Accordingly, we used the CCR5 binding inhibitor, Sch-C [48], to evaluate the apparent relative affinity of Env(wt) and Env(NYP) to CCR5(wt). "
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    Retrovirology 02/2007; 4(1):55. DOI:10.1186/1742-4690-4-55 · 4.19 Impact Factor
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    ABSTRACT: The third variable region, V3, of the gp120 surface envelope glycoprotein is an approximately 35-residue-long, frequently glycosylated, highly variable, disulfide-bonded structure that has a major influence on HIV-1 tropism. Thus the sequence of V3, directly or indirectly, can determine which coreceptor (CCR5 or CXCR4) is used to trigger the fusion potential of the Env complex, and hence which cells the virus can infect. V3 also influences HIV-1's sensitivity to, and ability to escape from, entry inhibitors that are being developed as antiviral drugs. For some strains, V3 is a prominent target for HIV-1 neutralizing antibodies (NAbs); indeed, for many years it was considered to be the "principal neutralization determinant" (PND). Some efforts to use V3 as a vaccine target continue to this day, despite disappointing progress over more than a decade. Recent findings on the structure, function, antigenicity, and immunogenicity of V3 cast new doubts on the value of this vaccine approach. Here, we review recent advances in the understanding of V3 as a determinant of viral tropism, and discuss how this new knowledge may inform the development of HIV-1 drugs and vaccines.
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