Chemokine Cellular Coreceptors

The HIV-1 coreceptors CXCR4 and CCR5 bind to ligand members of a family of molecules known as chemokines, or chemotactic cytokines. While the hallmark function of these small proteins is the direction of leukocyte trafficking, they can also participate in cellular events such as activation and costimulation (Bajetto et al. 2(X)la). Members of the chemokine family can be classified as either homeostatic or inflammatory based on their temporal expression (Charo and Ransohoff 2006 Kim 2005). Although traditionally the CNS had been thought to be protected from immune acti-... 

Several recent studies have also investigated whether CD4 and chemokine receptors exist in a complex on target cells (67-70). To what extent viral entry requires formation of a competent receptor complex remains to be determined. Certainly, cellular tropism is affected by the levels of expression of CD4 and specific coreceptors, but might also depend on the activation, configuration, and modification of these coreceptors, as well as on additional cellular factors regulating steps after viral entry. 

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