Inhibition of mannan-binding lectin associated serine protease (MASP)-2 reduces the cognitive deficits in a mouse model of severe traumatic brain injury.

The lectin pathway (LP) of complement mediates inflammatory processes linked to tissue damage and loss of function following traumatic brain injury (TBI). LP activation triggers a cascade of proteolytic events initiated by LP specific enzymes called MASPs (for Mannan-binding lectin Associated Serine Proteases). Elevated serum and brain levels of MASP-2, the effector enzyme of the LP, were previously reported to be associated with the severity of tissue injury and poor outcomes in patients with TBI. To evaluate the therapeutic potential of LP inhibition in TBI, we first conducted a pilot study testing the effect of an inhibitory MASP-2 antibody (α-MASP-2), administered systemically at 4 and 24 h post-TBI in a mouse model of controlled cortical impact (CCI). Treatment with α-MASP-2 reduced sensorimotor and cognitive deficits for up to 5 weeks post-TBI. As previous studies by others postulated a critical role of MASP-1 in LP activation, we conducted an additional study that also assessed treatment with an inhibitory MASP-1 antibody (α-MASP-1). A total of 78 mice were treated intraperitoneally with either α-MASP-2, or α-MASP-1, or an isotype control antibody 4 h and 24 h after TBI or sham injury. An amelioration of the cognitive deficits assessed by Barnes Maze, prespecified as the primary study endpoint, was exclusively observed in the α-MASP-2-treated group. The behavioral data were paralleled by a reduction of the lesion size when evaluated histologically and by reduced systemic LP activity. Our data suggest that inhibition of the LP effector enzyme MASP-2 is a promising treatment strategy to limit neurological deficits and tissue loss following TBI. Our work has translational value because a MASP-2 antibody has already completed multiple late-stage clinical trials in other indications and we used a clinically relevant treatment protocol testing the therapeutic mechanism of MASP-2 inhibition in TBI.