Hantavirus Gn^H Nanoparticle Immunogen Elicits a Cross-Neutralizing Antibody Response in Mice

Hantaviruses are zoonotic pathogens that are spread by rodents and can cause severe and fatal disease in humans. "New World" hantaviruses (endemic to North and South America) include the human pathogenic Andes orthohantavirus (ANDV), Choclo orthohantavirus (CHOV), and Sin Nombre orthohantavirus (SNV). Human infections can lead to hantavirus cardiopulmonary syndrome (HCPS), which is associated with ∼40% mortality. Currently, there are no FDA-approved hantavirus vaccines or treatments, but neutralizing antibodies targeting the glycoproteins Gn and Gc have been shown to be protective in animals. Here, we develop nanoparticle immunogens bearing the Gn head domain (Gn^H) from ANDV, CHOV, or SNV. Initial immunization studies with the ANDV-Gn^H monomer indicated that this antigen elicited a reactive but non-neutralizing antibody response in mice. To bolster the immune response, we developed a strategy to link Gn^Hs to mi3 nanoparticles using the SpyCatcher/SpyTag bioconjugation technology. We found that ANDV-Gn^H-mi3 nanoparticles elicited a cross-reactive antibody response that neutralized pseudotyped viruses containing ANDV and CHOV glycoproteins but not SNV. In contrast, CHOV-Gn^H-mi3 nanoparticles elicited only a homotypic neutralizing response. Finally, the reactivity of sera from mice immunized with a cocktail of ANDV-Gn^H-mi3 and SNV-Gn^H-mi3 nanoparticles was similar to sera from mice immunized with ANDV-Gn^H-mi3, only indicating that the SNV-Gn^H-mi3 antibody response was not even homotypically neutralizing. These results suggest that there are differences in immunodominance that may contribute to the breadth of the hantavirus-targeting neutralizing response elicited by Gn^H-based immunogens. Nonetheless, the cross-neutralizing sera obtained by ANDV-Gn^H-mi3 immunization suggest that developing broad immunogens may be possible with appropriate engineering.