Low serum levels of promatrix metalloproteinase-2 and-9 occur during acute Babesia canis infection in dogs

Inflammation is a hallmark of the acute Babesia canis infection. Pmmatrix metalloproteinase (proMMP)-2 and -9 are involved in inflammation, but their levels have not been analyzed in canine babesiosis. We hypothesized that in dogs infected with B. canis, serum proMMP-2 and -9 levels change between presentation and recovery. Degree of the change differs if dogs develop systemic inflammatory response syndrome (SIRS). This study included 24 dogs with an acute B. canis infection, at presentation and after two weeks. We used routine hematology and biochemistry methods, spectrophotometry for the acute-phase proteins, microscopy for parasitemia and zymography for (pro)MMPs. In vitro endothelial cells and leukocyte short-term cultures, and platelet lysates were used to detect specific MMP activity. Statistical analyses included Wilcoxon test for paired samples, Mann-Whitney U test and Spearman's rank correlation. Our results showed that endothelial cells, leukocytes and platelets are the source of proMMP-2 and proMMP-9. Furthermore, both proMMPs were lower at presentation than after recovery (p < 0.001). At presentation, proMMP-9 levels correlated with parasitemia (rho = -0.616, p = 0.009), total leukocyte (rho = 0.704, p < 0.001) and neutrophil counts (rho = 0.741, p < 0.001). Extent of alterations in proMMP-2 levels between presentation and recovery was lower (p = 0.038) in dogs with SIRS than in non-SIRS dogs, while levels of proMMP-9 were comparable between these groups. Our conclusion is that during the acute B. canis infection, low serum levels of proMMP-2 and proMMP-9 at presentation reflect thrombocytopenia and leukopenia. Decreased proMMP-2 level could be associated with SIRS.