Abstract 1042: Viral Chemokine Modulating Protein, M-T7, Interrupts Chemokine : Glycosaminoglycan (GAG) Interaction: M-T7 Inhibitory Activity is Dependent upon Y46 and V210 aminoacid residues
Background: Chemokines bind to glycosaminoglycans (GAGs) forming gradients that direct inflammatory cell invasion. The viral chemokine modulating protein (CMP), MT-7 binds the C terminal, GAG-binding domain of chemokines and has been previously reported to significantly reduce cell invasion and plaque growth in rat aortic and renal transplant models. Two other viral CMPs, M-T1 and M3 CMPs bind the N terminal domain of chemokines that bind to cell surface receptors. To determine the role of CC chemokine receptor 2 (CCR2) and GAGs for M-T7 anti-inflammatory activity, effects of M-T7 on plaque growth were assessed after mouse CCR2 deficient (CCR2−/−) or GAG deficient (NDST1−/−) aortic allograft transplant. Mononuclear cell migration in response to MCP-1 or RANTES into mouse ascites was also tested. Active sites necessary for M-T7 inhibition of chemokine function and monocyte activation, were assessed by infusion of in the mouse cell migration and human monocyte membrane fluidity assays.
Results: M-T7 significantly reduced cell migration and intimal hyperplasia in wild type CCR2+/+ (p<0.009), and CCR2−/− aortic transplants (p<0.026). M-T1 and M3 inhibited cell invasion and plaque in CCR2+/+, but not CCR2−/− mice. M-T7 inhibited plaque growth and CC chemokine (MCP-1 and RANTES)-induced cell migration in wild type mice (P<0.01), but not in NDST1−/− mice (P=0.34). Selected M-T7 point mutations Ty (Y)46A, and Val (V) 210A no longer block chemokine-induced cell migration nor monocyte activation, whereas Asn (N) 40, Asn (N) 63 and Val (V)129 retain inhibitory activity.
M-T7 but not M-T1 nor M3, blocks cell migration and plaque growth in CCR2 deficient (CCR2−/−) mouse aortic transplant models.
M-T7 loses the ability to block cell migration and plaque growth in NDST1−/−, GAG (heparan sulfate) deficient mice.
Point mutations Tyr46 and Val 210 lack inflammatory for mouse and human inflammatory monocyte responses indicating that these amino acid residues on the M-T7 CMP protein are required for inhibitory activity.