Author : McFadden G., Moyer R.
Description:Unlike the classic viroceptors (virus-encoded receptor homologs) that bind and inhibit cytokines such as TNF, interferons, and IL-1, the viral proteins that bind and modulate chemokines were discovered by screening analysis for novel cytokine inhibitors expressed by poxviruses. Currently, two classes of chemokine-binding proteins have been described which interact with chemokines in different fashion. The first class, exemplified by the M-Tl protein of myxoma virus and the secreted 35K proteins from a variety of orthopoxviruses, are 35-45 kDa secreted glycoproteins that bind and inhibit the ability of a broad spectrum of CC chemokines to engage their cognate receptors. Binding occurs in a relatively species-independent fashion. The second class is typified by the M-T7 protein of myxoma virus, which was first described as an inhibitor of IFN7 but has a second property of binding to a wide spectrum of chemokines via the conserved glycosaminoglycan-binding domains of these ligands. Both classes of proteins affect the pathogenesis of virus infections but are believed to interfere with chemokine biological functions by different mechanisms.