Abstract:
Venezuelan equine encephalitis virus (VEEV) is a New World alphavirus that is capable of causing significant disease in equines and humans. Moreover, infection with VEEV can be fatal in up to 90% of cases for equines. In humans, while death is rare, infection with VEEV can result in debilitating neurological sequelae. The current vaccines for VEEV are a live-attenuated vaccine (TC-83) and an inactivated form of the vaccine (C-84). However, neither of these are approved by the FDA for human use and only at risk military personnel and laboratorians are vaccinated. We are studying the rational design of VEEV vaccines through mutation of the programmed -1 ribosomal frameshifting (-1 PRF) signal of VEEV. Use of the -1 PRF signal allows production of the viral trans-frame protein of VEEV, which is known to play a role in neuropathogenesis. Our lab recently characterized the -1 PRF signals for alphaviruses and results revealed novel -1 PRF stimulatory structures. While disruption of the -1 PRF signal mildly affected VEEV kinetics in cell culture, it significantly inhibited its pathogenesis in mice challenged subcutaneously or via aerosol. In addition to markedly increased survival, mice exposed to the -1 PRF mutant VEEV (VEEV TrDPRFm) displayed less severe clinical signs and weight loss over the course of infection compared to wild-type (WT) control mice. Serial sacrifice studies indicated mice exposed to VEEV TrDPRFm had either undetectable or reduced levels of virus in the brain, spleen, and serum at all timepoints assayed indicating that dissemination of VEEV TrDPRFm is altered in vivo, resulting in less viral replication and overall decreased pathogenesis. Finally, mice vaccinated with VEEV TrDPRFm developed strong neutralizing antibodies and were protected against lethal challenge with aerosolized VEEV TrD. These studies indicate that targeting translational recoding events such as frameshifting is a potential avenue of inquiry for rational vaccine development.
