Neisseria Meningitidis NalP Cleaves Human Complement C3, Facilitating Degradation of C3b and Survival in Human Serum

Significance The complement system is a crucial component of the innate immune response in humans. In this study, we report the characterization of an autotransporter protease of Neisseria meningitidis named NalP. We show that NalP is able to cleave the α-chain of the human complement factor C3 in a species-specific manner. As a consequence, the deposition of C3b on the bacterial surface is reduced and, in human serum, the NalP-generated C3b fragment is further degraded by host factors. Our results significantly increase the knowledge of how N. meningitidis can survive and multiply in human serum, evading the innate immune system.