CCR5

CCR5, short for chemokine (C-C motif) receptor 5, is a cytokine receptor that macrophage-tropic viruses including HIV use as a co-receptor to enter host cells.

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CCR5 is also the name of the gene that codes for the CCR5 receptor.

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A number of alleles of the CCR5 gene exist. In particular, the Δ32 allele of CCR5 is of interest to microbiologists and medical researchers, as it offers partial protection against infection by macrophage-tropic viruses and also delays the onset of AIDS in HIV-infected individuals.

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About ten percent of Europeans have the Δ32 allele. This is thought to be the result of the selection pressure of some past exposure, most likely smallpox, to another virus using CCR5 as an entry point. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15715976&query_hl=54

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A new drug AK602 sticks to CCR5, prevents HIV from entering cells, causes almost no side effects, and was developed by researchers at Kumamoto University. http://www.asahi.com/english/Herald-asahi/TKY200507070204.html A problem of this approach is that CCR5 is the major, but not the only co-receptor by which HIV infects cells. HIV strains exist which rely on the co-receptor CXCR4 alone for infection, and these are more aggressive, with individuals infected by CXCR4-tropic HIV experiencing a more rapid onset of AIDS, more severe disease and die sooner. Would AK602 be widely introduced, the evolutionary fitness of CXCR4-tropic HIV would dramatically increase and this more dangerous strain could become predominant; it nowadays is found only in 5% of all HIV infections.

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That such a phenomenon can indeed occur is demonstrated by the experience with malaria in Thailand in the 1960s-70s: New drugs that were very effective against Plasmodium ovale and Plasmodium malariae, which cause the comparatively harmless tertiana and quartana forms of malaria were at that time widely distributed. This led to an increase in competitive fitness of the Plasmodium falciparum parasite, which causes the most lethal tropica form of malaria which nowadays constitutes around 80% of all malaria cases in Thailand, as opposed to less than 20% after WW2.

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Cytokine: Cytokines are small protein molecules that are the core of communication between immune system cells, and even between these cells and cells belonging to other tissue types. They are actively secreted by immune cells as well as other cell types in response to external stimuli. Cytokines that are pro...

Receptor: Receptor may refer to:...

Macrophage-tropic virus: REDIRECT HIV tropism...