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Individuals heterozygous for the mutant allele have a greater than 50% reduction in functional CCR5 receptors on their cell surfaces due to dimerization between mutant and wild-type receptors that interferes with transport of CCR5 to the cell surface.
Heterozygote carriers are resistant to HIV-1 infection relative to wild types and when infected, heterozygotes exhibit reduced viral loads and a 2-3-year-slower progression to AIDS relative to wild types.
Because binding to CD4 alone can sometimes result in gp120 shedding, gp120 must next bind to co-receptor CCR5 in order for fusion to proceed.
The tyrosine sulfated amino terminus of this co-receptor is the "essential determinant" of binding to the gp120 glycoprotein.
Maraviroc was approved for use by the FDA in August 2007.
A problem of this approach is that, while CCR5 is the major co-receptor by which HIV infects cells, it is not the only such co-receptor.
This bind results in gp41, the other protein product of gp160, to be released from its metastable conformation and insert itself into the membrane of the host cell.
Although it hasn't been finalized as a proven theory yet, binding of gp120-CCR5 involves two crucial steps: 1) The tyrosine sulfated amino terminus of this co-receptor is an "essential determinant" of binding to gp120 (as stated previously) 2) Following step 1., there must be reciprocal action (synergy, intercommunication) between gp120 and the CCR5 transmembrane domains These experimental drugs include PRO140 (Cyto Dyn), Vicriviroc (Phase III trials were cancelled in July 2010) (Schering Plough), Aplaviroc (GW-873140) (Glaxo Smith Kline) and Maraviroc (UK-427857) (Pfizer).
The envelope glycoprotein structure consists of two protein subunits cleaved from a Gp160 protein precursor encoded for by the HIV-1 env gene: the Gp120 external subunit, and the Gp41 transmembrane subunit.
Two studies have used linkage analysis to estimate the age of the CCR5 Δ32 deletion, assuming that the amount of recombination and mutation observed on genomic regions surrounding the CCR5 Δ32 deletion would be proportional to the age of the deletion.
Using a sample of 4000 individuals from 38 ethnic populations, Stephens et al.
estimated that the CCR5-Δ32 deletion occurred 700 years ago (275-1875, 95% confidence interval). (1998), estimated the age of the CCR5 Δ32 mutation is based on the microsatellite mutations to be 2100 years (700-4800, 95% confidence interval).
On the basis of observed recombination events, they estimated the age of the mutation to be 2250 years (900-4700, 95% confidence interval).