Translational Frontiers for Chikungunya Virus: New World Epidemic, New Strains, New Therapeutic Targets

Chikungunya virus (CHIKV) infection results in chikungunya fever (CHIKF), marked by sudden onset of high fever, rash, and debilitating polyarthritis and polyarthralgia, which can last for months to years. Despite the severe morbidity and impact on disability adjusted life-years, an FDA-approved CHIKV vaccine or therapeutic remains elusive. This project addresses two aspects of therapeutic development: surveillance and drug target development. First, an outbreak of CHIKF in La Romana, Dominican Republic is described. During this outbreak, several parameters of established CHIKV epidemiology were challenged, such as the percent of patients presenting with arthritis as well as demographic distribution of disease. Overall, CHIKF was underdiagnosed in La Romana, likely due to attenuated CHIKV-disease phenotype. Related to this, the virulence of strains from distinct CHIKV lineages was compared in the lethal A129 CHIKF mouse model. Isolates from the Caribbean and Mexico were attenuated compared to the West African, East/Central/South African, and Indian Ocean isolates, and even compared to other Asian isolates to which strains in the Caribbean are most closely related. Surveillance is an important aspect of developing appropriate trials for future vaccines and therapeutics, and together these data suggest that the incidence of CHIKF in the New World is likely underestimated, and surveillance practices need to be adjusted to include identification of an attenuated disease phenotype. Finally, the development of novel antiviral drug targets was explored. As the envelope proteins of alphaviruses are replete with structure-maintaining disulfide bonds, inhibitors to the host enzymes responsible for disulfide bond formation—protein disulfide isomerase (PDI) family chaperones—were utilized as a tool to potentiate PDI as an anti-CHIKV (and anti-alphavirus) drug target. PDI-inhibitors PACMA31 and 16F16, as well as inhibitors EN460 and auranofin to PDI regulatory proteins endoplasmic reticulum oxidoreductin-1 (ERO-1) and thioredoxin reductase (TRX-R), respectively, all greatly reduced CHIKV replication in vitro; 16F16 likely caused misfolding of the envelope proteins and subsequent production of non-functional virus particles, while auranofin likely selectively induced apoptosis in infected cells. Auranofin modestly reduced viral replication and significantly reduced footpad swelling in infected C57Bl/6 mice. In all, this project addressed two important translational avenues of CHIKV research.