While most cats infected with Feline Coronavirus (FCoV) develop mild to inapparent diarrheal disease, a subset of them develop the devastating and deadly feline infectious peritonitis (FIP). FCoV can spread via fecal-oral or respiratory routes, particularly in cat shelter environments. Coronaviruses have three envelope glycoproteins, S, E, and M, but the surface protein (S) is in charge of viral entry. S binds the cell surface receptor and then merges the viral membrane to the cell plasma or endosomal membranes, causing viral entry. S also causes cell-cell fusion (syncytia) post-infection. The S protein of most coronaviruses is also highly immunogenic. The devastating FIP disease begs the development of protective vaccines. We identified a small molecule, XM-01, that embeds within viral membranes and inhibits membrane fusion. Importantly, this novel method of inhibition renders virions noninfectious, while maintaining the native conformations of the surface glycoproteins, ideal for eliciting effective immune responses against such viral glycoproteins. Remarkably, vaccination with XM-01-treated influenza virions yielded an increase in neutralizing antibodies and survival rate, and a decrease in morbidity and mortality upon viral challenge in a mouse model, as compared to the traditional formalin-inactivated influenza vaccine. Thus, our Aim 1 will be to determine whether XM-01 can be used to develop a FeCoV inactivated vaccine. Importantly our recent preliminary data includes already determined conditions for complete FCoV inactivation. We will optimize XM-01 inactivation of FCoV in preparation to determine whether this vaccine can yield a robust immune response against this virus. Additionally, our lab has successfully used replication-incompetent vesicular stomatitis virus (VSV)-based pseudotyped virions to vaccinate and protect hamsters against Nipah, Hendra, and Ebola virus diseases with 100% safety and 100% efficacy (manuscript in final revision for Nature Publishing Journals Vaccines). Our Aim 2 will use the replication-incompetent VSV system to develop a vaccine against FCoV. We will optimize incorporation of FCoV-S into VSV virions in preparation to determine whether this vaccine can yield a robust immune response against this virus. As both inactivated and replication-incompetent virions vaccine platforms have been successfully used to prevent other viral diseases, the completion of our Aims will allow our vaccine platforms to readily advance to vaccination clinical trials/licensing.