Protection of non-murine mammals against encephalomyocarditis virus using a genetically engineered Mengo virus

Abstract

Genetically engineered Mengo viruses with artificial deletions in the 5' noncoding poly(C) tracts are highly attenuated for pathogenicity when introduced as live vaccines into the natural murine host. Inoculation produces lifelong protective immunity without disease or viral persistence. This report extends the vaccination studies to non-murine hosts, including baboons, macaques and domestic pigs, all of which are susceptible to severe cardiovirus epizootics. All animals of these species that were inoculated with vMC24, an engineered strain of Mengo, seroconverted. When the immunized animals were challenged, they were protected against lethal doses of encephalomyocarditis virus (EMCV) derived from currently circulating epizootic strains. In baboons, the neutralizing antibody titers induced by vMC24 were significantly higher than from an inactivated EMCV vaccine. Moreover, terminal histopathology on baboons (inoculated intramuscularly), macaques (inoculated intracerebrally), and pigs (inoculated intramuscularly) showed few, if any, gross lesions characteristic of EMCV-like disease, in the vMC24 vaccinates. We suggest that genetically engineered, short poly(C) Mengo viruses may be universally potent attenuated vaccines for many types of animals and can possibly provide safe, efficacious protection against all cardioviruses of the EMCV serotype.