The interaction between the amoeba Balamuthia mandrillaris and extracellular matrix glycoproteins in vitro

Balamuthia mandrillaris, a soil amoeba, is the causative agent of Balamuthia granulomatous amoebic encephalitis, a life-threatening brain infection. This amoeba is acquired from contaminated soil and may enter the host through cutaneous lesions or through nasal passages, migrating to the lungs or brain. During invasion, B. mandrillaris has access to components of the extracellular matrix (ECM) of the host. Therefore, we investigated the interaction of B. mandrillaris with 3 ECM glycoproteins (collagen-I, fibronectin and laminin-1) that are encountered in host connective tissues and at the basal lamina. Using optical microscopy, amoeba association on ECM-coated surfaces was examined. Binding of amoebae on laminin was greater than that on collagen or fibronectin. Laminin-adhered B. mandrillaris exhibited elongated and spread forms, distinctive from those observed for amoebae on a plastic surface. Collagen and fibronectin-adhered B. mandrillaris presented elongated shapes with cellular expansions. Binding to collagen, fibronectin, or laminin was inhibited when amoebae were pre-treated with sialic acid. Treatment with galactose resulted in diminished binding of amoebae on laminin, while mannose increased binding in all coating conditions tested. Dependence of divalent cations on amoeba binding was demonstrated for laminin-amoeba interaction. Collectively, the results indicate that B. mandrillaris recognizes specific glycoproteins of the mammalian extracellular matrix.