Project Summary/Abstract Acute flaccid myelitis (AFM) is a poliomyelitis-like illness of children that emerged in the US in 2014. Since then, AFM outbreaks occur August-October every other year, concurrent with outbreaks of enterovirus D68 (EV-D68) infection. Increasing evidence now indicates that EV-D68 is a principal cause of AFM. EV-D68, in the same Enterovirus genus as poliovirus, primarily causes respiratory tract infections. However, the mechanisms of EV-D68 neuropathogenesis and the characteristics of the human immune response to EV-D68 are poorly understood. This five-year research career development award will provide training and development of the skills necessary for the PI to establish an independent research program focused on understanding how EV-D68 causes respiratory and neurologic disease and how human antibodies modify this pathogenesis. Currently the PI is an Assistant Professor on the tenure track in Pediatric Infectious Diseases and Microbiology & Immunology at the University of North Carolina at Chapel Hill School of Medicine. His training to date has focused on the isolation and characterization of human monoclonal antibodies (mAbs) from subjects with prior EV-D68 infection. He will supplement this experience with further training in developing in vivo mouse and ex vivo human tissue models of EV-D68 infection with which to study the pathogenesis of this virus and how human antibodies, both monoclonal and polyclonal, modify pathogenesis. The short-term goal of the proposed studies is to test the central hypothesis that human antibodies prevent EV-D68 from causing AFM but do not protect against respiratory disease. The PI will be mentored by national experts in the study of picornaviruses (Drs. Craig Cameron and Stanley Lemon), human airway epithelial cultures (Dr. Raymond Pickles), mouse models of virus infection (Dr. Mark Heise), and human antibodies (Dr. James Crowe, Jr.). The specific aims are to 1) determine how EV-D68-specific human antibodies modify virus-induced respiratory disease and AFM in a mouse model of infection, to test the hypothesis that antibodies efficiently preclude EV- D68 from causing AFM by preventing dissemination to the CNS; and 2) investigate factors that determine the efficacy of antibody at inhibiting EV-D68 infection in differentiated primary human airway epithelial cells at an air-liquid interface, to test the hypothesis that antibodies poorly protect against initial respiratory mucosal infection. Overall, these studies will help determine whether EV-D68 neutralizing antibodies are a mechanistic correlate of protection from AFM by pinpointing the quantity and quality of antibodies capable of restricting EV- D68 infection to the respiratory tract. Industry collaborators are developing protective mAbs made by the PI as human therapeutic agents, which would be the only available targeted therapy for children with EV-D68 infection. Thus, these studies directly translate to importance in human heal...