Project 3: Vaccine Design [mRNA] VEEV/CHIKV (alphaviruses)

SUMMARY Alphaviruses are mosquito-transmitted viruses that cause severe disease in humans. The genus is divided into two groups: Arthritogenic viruses cause arthralgia and musculoskeletal disease that can persist for years after infection, and encephalitic viruses infect the brain and can cause long-term neurological injury or lethality. The

goal of FLARE Center Project 3 is a structure-based and epitope-focused design of next-generation vaccine candidates for two prototype alphaviruses, one arthritogenic (chikungunya virus, CHIKV) and one encephalitic (Venezuelan equine encephalitis virus, VEEV). CHIKV is globally distributed and has emerged in part due to

sequence adaptations that enabled an expanded range of mosquito vectors. VEEV is endemic to the Americas and has caused large epidemics in South and Central America. We hypothesize that structural conservation among alphaviruses, coupled with recent advancements in elucidating details of molecular interactions

between the alphavirus E1/E2 glycoprotein and protective monoclonal antibodies (mAbs) or host receptors, will enable immunogen design strategies that yield safe and effective vaccines that can be rapidly adapted to other alphaviruses. Our objective is to build a ‘plug-and-play’ workflow of immunogen and vaccine platform pairs that

can be deployed for emerging or new alphaviruses. Aim 1 focuses on optimization of the E2 B-domain (E2-B), which is engaged by broadly protective mAbs. Aim 2 explores the E1 fusion loop (E1-FL) as a vaccine target, based on the recent discovery that human E1-FL-specific mAbs have pan-alphavirus protective potential via

non-neutralizing, Fc-mediated mechanisms. In Aim 3, structures of the hexameric E1/E2 spike bound to host receptors MXRA8 (CHIKV) or LDLRAD3 (VEEV) will be used as a template to engineer immunogens that capture the prefusion complex (preE12), enabling exposure of key quaternary epitopes. Immunogens will be

integrated into protein nanoparticles or, in collaboration with our industry partner Moderna, encoded as lipid- encapsulated mRNA vaccines. Successful designs will be compared head-to-head with virus-like particle (VLPs)-based vaccines in murine models of arthritis (CHIKV) and lethal disease (CHIKV and VEEV) in Aim 4.

After down-selection and rigorous Go/No-Go decisions, the top vaccine candidates will be transitioned to Animal Core D for further evaluation in mice and non-human primates. Project 3 will work closely with the Scientific and Administrative Cores to accomplish these objectives and is conceptually and technically linked

to other FLARE Center Projects focused on flaviviruses and alphaviruses.