A novel factor I activity in Nipah virus inhibits human complement pathways through cleavage of C3b

Nipah virus (NiV) belongs to the family Paramyxoviridae, genus Henipavirus, and its host is the megabat. Nipah virus is an emerging zoonotic viral pathogen that can cause serious respiratory and neurological diseases. The complement cascade initiated by three main pathways: the classical pathway, the lectin pathway, or the alternative pathway. These three pathways converge on the C3, which is activated by cleavage to C3a and C3b. C3b covalently bind to virus components and facilitate opsonin action and phagocytosis. Factor I cleaves and inactivates C3b. A novel mechanism has been identified that NiV can cleave and inactivate C3b via factor I-like protease activity to avoid killing from complement. Inhibiting this ability of NiV could be the basis for the development of safer vaccine and more effective therapies.
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