Epitope focusing using structure-based immunogen design approaches

Project Summary/Abstract Since the emergence of the novel severe acute respiratory syndrome virus 2 (SARS-CoV-2) coronavirus, the need for better frameworks to rapidly develop vaccines in response to emerging viral threats, including other coronaviruses of potential pandemic concern, is clear. One approach is to develop an immunogen design platform that leverages the often-conserved interface between viral surface glycoproteins and their host cellular receptor(s). For SARS-CoV-2, elicited antibodies would target the interaction between its "spike" glycoprotein and the human angiotensin-converting enzyme 2 (ACE-2) receptor. Other coronaviruses like SARS-CoV-1 and the common cold-causing NL63 also use ACE-2, thus antibodies that interfere with this conserved interaction might also protect against future novel coronaviruses that also use this receptor. The goal of this proposed work is to use structure-guided, rational design of novel immunogens to focus the immune response to the ACE-2 receptor binding interface of SARS-CoV-2. This may provide a generalizable framework of immunogen design strategies that can be rapidly used to combat novel emerging viruses in the future. I will use the following two design approaches: 1) I will use molecular scaffolds that are structurally homologous to the SARS-CoV-2 receptor binding domain (RBD) and "resurface" them with the ACE-2 receptor binding motif (RBM) from SARS- CoV-2. As a result, the antigenically distinct scaffolds will uniformly present the conserved SARS-CoV-2 RBM and will focus the immune response to the conserved interface. 2) I will use hyperglycosylation to mask immunodominant, non-protective epitopes on the SARS-CoV-2 RBD to direct the immune response to the SARS-CoV-2 RBM. For both approaches, I will analyze the elicited immune response to determine the extent of immune focusing to the SARS-CoV-2 RBM, obtain neutralization profiles and structurally characterize down- selected elicited antibodies. Collectively, these data will provide insight into how masking and resurfacing can determinatively direct the immune response to a conserved viral epitope. While I use SARS-CoV-2 as a model virus, this could provide a vaccine design framework for future viral pathogens with the potential for rapid deployment.