Background/Rationale: As the Coronavirus Disease 2019 (COVID-19) epidemic expands across the United States and the world, there are no proven therapies and little information is known regarding on immunity to this virus. At this stage of the pandemic, all prevention and treatment strategies that show promise must be explored. This proposal will focus on the polyclonal and monoclonal antibody responses to the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) envelope. Objectives: The overarching goal of this program is to obtain a comprehensive understanding of the polyclonal and monoclonal response to the SARS-CoV-2 envelope E, M, and S proteins. The specific aims of this proposal are: 1) Deconvolute the polyclonal antibody response against the viral envelope of SARS-CoV-2; 2) Isolate neutralizing and non-neutralizing monoclonal antibodies against various epitopes of spike protein (S), envelope protein (E), and membrane glycoprotein (M) of SARS-CoV-2; and 3) Map the corresponding epitope(s) of the monoclonal antibodies. Methods: We will obtain paired, acute and convalescent, samples from 60 inpatients and outpatients with COVID-19 (30 have already been enrolled from the VA Maryland Health Care System and the University of Maryland Medical System). We will screen samples by binding, live and pseudovirus neutralization. In this proposal, we also will have access to BSL3 facilities on this campus that run neutralization assay with live virus by one of the world experts in coronaviruses (Matt Frieman, PhD). Donors will be ranked on the basis of both neutralization potency and breadth, and binding. The top three donors in each of the inpatient and outpatient groups will be chosen for further study (top anti-RBD neutralization and breath, top anti- receptor binding domain (RBD)-depleted plasma neutralization and breath, and top spike binding titers with non-neutralizing plasma). In these six individuals, the anti-envelope antibody will be affinity purified; and fractionated using free- flow-electrophoresis. This technique can separate antibodies based on charge, which will lead to separation based on targeted epitopes as well. Individual fractions will be tested by binding and neutralization; and characteristic biochemical and functional signatures of antibodies targeting each epitope will be ascertained. Fractions of interest (different for each donor depending if neutralization or binding is targeted) will be sent for mass spectrometry. B cell libraries will also be made from the convalescent IgG and IgA memory B cell pools; and they will be interrogated using three complementary techniques including - acute phase plasmablast repertoire analysis, subtraction analysis, and antigen baiting to identify potential antibodies. Finally, mass spectrometry will be used to rank antibody candidates. 40 monoclonal antibodies (mAbs) will be made and again be screened by neutralization potency, breadth, and isoelectric point, with top neutralizing and...