Abstract: Disclosed herein are compositions, kits and methods for determining the concentration of fluid-phase MASP-2/C1-INH complex in a biological fluid, such as a biological fluid obtained from a subject infected with SARS-CoV-2. Also disclosed are methods of using said compositions, methods and kits for detection of MASP-2/C1-INH complex to determine the status of lectin pathway activation in a mammalian subject and thereby assess the risk of a subject that is or has been infected with SARS-CoV-2 for developing COVID-19-related ARDS or other poor outcome, or determine the need for treatment or efficacy of treatment of a subject in need thereof with a complement inhibitor such as a MASP-2 inhibitory agent.

Abstract: Disclosed herein are monoclonal antibodies that specifically bind to human mature Factor D and that do not bind to human Pro-Factor D, monoclonal antibodies that specifically bind to human Pro-Factor D and do not bind to human mature Factor D, and monoclonal antibodies that bind to both human mature Factor D and human Pro-Factor D. Also disclosed are methods of using the monoclonal antibodies, and compositions comprising the same, for detection of the mature and/or the pro-form of Factor D in biological samples, to determine the status of the Alternative Pathway of Complement (APC) in a mammalian subject, or to determine the status of Factor D after treatment with a MASP-3 inhibitory agent which inhibits the conversion of Pro-Factor D to mature Factor D.