Structural and functional insights into mpox entry and neutralization

ABSTRACT Orthopoxviruses have caused devastating pandemics and outbreaks throughout human history, primarily through variola virus (smallpox), which was eradicated globally in 1977. Another member of this genus, monkeypox virus (MPXV), causes mpox disease. Recent global MPXV outbreaks have raised concern about threats to global health. Like smallpox, MPXV can be transmitted from person to person. However, current vaccines against MPXV elicit limited antibody responses, with markedly lower neutralizing antibody levels compared to naturally infected convalescent individuals. In this R01 proposal, we aim to identify the primary targets of neutralizing and protective antibodies against MPXV, as well as elucidate MPXV-receptor interactions and molecular determinants of antibody-mediated protection. Addressing these critical knowledge gaps is essential for developing improved therapeutic options against MPXV. We have developed a highly integrated platform that combines diverse sources of antibodies from mpox convalescents, MPXV vaccinees, and a large human antibody phage library, with state-of-the-art antibody isolation strategies, functional assays, and high-throughput structural biology, to address these critical knowledge gaps. Our recent studies have uncovered novel protective antibodies to MPXV and identified vulnerable sites (protective epitopes) on MPXV antigens, establishing the effectiveness of our platform for anti-MPXV antibody studies. Building on this strong foundation, the proposed research aims to (1) uncover new epitopes that are poorly represented in current vaccines but crucial for enhancing immune responses against mpox; (2) define the structural basis of MPXV attachment to human cells by resolving interactions between the viral attachment proteins and host cell receptors as targets for protective antibodies; and (3) define and optimize therapeutic antibody combinations against MPXV. Overall, by leveraging our extensive antibody resources and our structural and functional platform for orthopoxvirus studies, we will identify highly protective as well as novel epitopes and elucidate the mechanisms of MPXV entry and antibody-mediated protection. These insights will guide design of strategies and options for treatment and prevention of current mpox outbreaks and enhance preparedness for future mpox or other poxvirus outbreaks or pandemics.