MMP9 and infection: Capsule plays a role in the virulence of S. suis; type 2 capsule mutants are avirulent in murine and pig models of infections [43], [49] The capsule itself can mediate prostaglandin E2 (PGE2) and matrix metalloproteinase 9 (MMP-9) production by human macrophages [50] suggesting a role in pathogenesis of disease.