Functional comparisons among members of the poxvirus T1/35kDa family of soluble CC-chemokine inhibitor glycoproteins.
Many poxviruses express a 35-40-kDa secreted protein, termed "T1" (for leporipoxviruses) or "35kDa" (for orthopoxviruses), that binds CC-chemokines with high affinity but is unrelated to any known cellular proteins. Many previously identified poxvirus cytokine-binding proteins display strict species ligand-binding specificity. Because the T1 and 35kDa proteins share only 40% amino acid identity, we compared the abilities of purified myxoma virus-T1 (M-T1) and vaccinia virus (strain Lister)- and rabbitpox virus-35kDa proteins to inhibit human CC-chemokines in vitro. All three proteins were equally effective in preventing several human CC-chemokines from binding to target chemokine receptors and blocking subsequent intracellular calcium release. The inhibitory affinities were comparable (Ki = 0.07-1.02 nM). These proteins also displayed similar abilities to inhibit (IC50 = 6.3-10.5 nM) human macrophage inflammatory protein-1alpha-mediated chemotaxis of human monocytes. None of the viral proteins blocked interleukin-8-mediated calcium flux or chemotaxis of human neutrophils, confirming that the biological specificity of the T1/35kDa family is targeted inhibition of CC-chemokines. Despite the significant sequence divergence between the leporipoxvirus T1 and orthopoxvirus 35kDa proteins, our data suggest that their CC-chemokine binding and inhibitory properties appear to be species nonspecific and that the critical motifs most likely reside within the limited regions of conservation.
Department of Biochemistry, University of Alberta, Edmonton, Alberta, T6G 2H7, Canada.
A S
AS
Lalani
T L
TL
Ness
R
R
Singh
J K
JK
Harrison
B T
BT
Seet
D J
DJ
Kelvin
G
G
McFadden
R W
RW
Moyer
D002118:Calcium / Q000378:metabolism; D018925:Chemokines / Q000378:metabolism*; D002634:Chemotaxis, Leukocyte; D006023:Glycoproteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D006031:Glycosylation; D018922:HL-60 Cells; D006801:Humans; D008970:Molecular Weight; D009000:Monocytes / Q000166:cytology; D009233:Myxoma virus / Q000276:immunology*; D009504:Neutrophils / Q000166:cytology; D019707:Receptors, Chemokine; D017421:Sequence Analysis; D014407:Tumor Cells, Cultured; D014616:Vaccinia virus / Q000276:immunology*; D014764:Viral Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*
D018925:Chemokines; D006023:Glycoproteins; D019707:Receptors, Chemokine; D014764:Viral Proteins; D002118:Calcium