The World Health Organization’s list of priority pathogens that pose the highest public health risks, and for which there are insufficient treatments, is composed solely of enveloped viruses. Examples of enveloped viruses highly relevant to human health are: HIV, influenza A viruses (IAV), EboV, MERS-CoV, SARS, SARS-CoV-2, CHIKV, NiV, HeV, RSV, ZIKV, and the influenza A (IAV) and B (IBV) viruses. The human cost of their illnesses is in the millions, and the economic cost is in the hundreds of billions of dollars per year. The standard methods for generating vaccines, including whole inactivated virus (WIV), live attenuated virus (LAV), sub-unit, and DNA/RNA, often fail to result in effective prophylaxis. WIV vaccines have some advantages such as their safety and their presentation of multiple antigens to the immune system. However, WIVs often induce insufficient immunity or even vaccine-enhanced disease due to antigen conformational differences between the WIV vaccine and the challenge virus. Our proposal addresses the pressing need for more effective and broadly applicable WIV vaccines by exploring a promising new technology using the antiviral XM-01 (patent applications pending). Current virus inactivation methods for WIV preparation use chemical or physical means that often damage or modify viral antigens, including the glycoproteins, which are important immunogens for the enveloped viruses. This often leads to non-protective or even destructive immune responses. For example, the efficacies of the currently used WIV vaccines for IAV are between 10%-60%. We recently developed a novel vaccine platform that uses XM-01 to target the viral membrane while largely preserving the native conformation of viral glycoproteins. Preliminary data using IAV as a model indicates that immunization with XM-01-inactivated IAV particles improved induction of neutralizing antibodies to both hemagglutinin (HA) and neuraminidase (NA), as well as animal survival, compared to the traditional formalin-inactivated IAV particles. As XM-01 is a broadspectrum inhibitor of enveloped viruses, our central hypothesis is that virus inactivation with XM-01 improves WIV vaccine development by preserving glycoprotein conformations, facilitating the effective generation of a protective immune response. We will test our hypothesis with two Specific Aims: Aim 1: Determine the mechanism by which XM-01 inactivated virus affords improved immune responses as compared to traditional WIV vaccine methods, using the influenza virus model. Aim 2: Determine XM-01 vaccination safety, efficacy, and breadth of immune responses. We expect this work will improve our understanding of the mechanism by which XM-01 membrane-mediated viral inactivation generates an enhanced protective immune response, and to assess the new method’s safety, efficacy, and ability to generate broadly protective antibodies against heterologous viral strains, overall assessing whether this new mode of inactivation may be amenable for broad improvement of WIV vaccines.