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.
Lalani
A S
AS
Department of Biochemistry, University of Alberta, Edmonton, Alberta, T6G 2H7, Canada.
Ness
T L
TL
Singh
R
R
Harrison
J K
JK
Seet
B T
BT
Kelvin
D J
DJ
McFadden
G
G
Moyer
R W
RW
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