Unveiling Strategies for Chikungunya Virus Attenuation and Antiviral Therapy

Abstract

Chikungunya virus (CHIKV) is a mosquito-borne cause of epidemics of debilitating arthritis worldwide. Currently, there are no licensed vaccines or antiviral therapies available for the prevention or treatment of CHIKV disease. Furthermore, the viral and host determinants required for CHIKV replication and pathogenesis are not understood. Using chimeric viruses generated from virulent and attenuated CHIKV strains, I identified a single residue in the E2 viral attachment protein that serves as a critical determinant of CHIKV replication in cultured cells and pathogenesis in mice. I demonstrate that E2 residue 82 differentially influences infectivity in mammalian and mosquito cells and contributes to interactions with glycosaminoglycans (GAGs). Moreover, mice inoculated with GAG-dependent viruses displayed reduced inflammation in the joint and dissemination to sites of secondary replication. These findings indicate that E2 residue 82 modulates CHIKV dissemination and arthritis and suggest a function for GAG utilization in CHIKV attenuation. Using chemical compound and RNA interference screening approaches, I identified digoxin, an inhibitor of the sodium-potassium ATPase, and PSME2, a regulator of the immunoproteasome, as antagonists of CHIKV infection. Digoxin inhibited CHIKV at both entry and post-entry steps in the replication cycle and was effective against other alphaviruses. Knockdown of PSME2 or blockade of proteasome activity enhanced CHIKV infection. These data suggest roles for the sodium-potassium ATPase and immunoproteasome in CHIKV replication. Collectively, this work reveals mechanisms of CHIKV virulence and provides new targets for the development of CHIKV-specific and broad-spectrum antivirals.