Mutation variants generated from nonvirulent coxsackievirus B3 acquire virulence phenotypes by active virus replication

Attenuated strain of CVB3 with a mutation in the CAR-interacting region protects against both myocarditis and pancreatitis

Coxsackievirus B3 (CVB3), is commonly implicated in myocarditis, which can lead to dilated cardiomyopathy, in addition to causing acute pancreatitis and meningitis. Yet, no vaccines are currently available to prevent this infection. Here, we describe the derivation of a live attenuated vaccine virus, termed mutant (Mt) 10, encoding a single amino acid substitution H790A within the viral protein 1, that prevents CVB3 infection in mice and protects from both myocarditis and pancreatitis in challenge studies. We noted that animals vaccinated with Mt 10 developed virus-neutralizing antibodies, predominantly containing IgG2a and IgG2b, and to a lesser extent IgG3 and IgG1. Furthermore, by using major histocompatibility complex class II dextramers and tetramers, we demonstrated that Mt 10 induces antigen-specific T cell responses that preferentially produce interferon-γ. Finally, neither vaccine recipients nor those challenged with the wild-type virus revealed evidence of autoimmunity or cardiac injury as determined by T cell response to cardiac myosin and measurement of circulating cardiac troponin I levels, respectively. Together, our data suggest that Mt 10 is a vaccine candidate that prevents CVB3 infection through the induction of neutralizing antibodies and antigen-specific T cell responses, the two critical components needed for complete protection against virus infections in vaccine studies.

Antiviral effects of small interfering RNA simultaneously inducing RNA interference and type 1 interferon in coxsackievirus myocarditis

Antiviral therapeutics are currently unavailable for treatment of coxsackievirus B3, which can cause life-threatening myocarditis. A modified small interfering RNA (siRNA) containing 5'-triphosphate, 3p-siRNA, was shown to induce RNA interference and interferon activation. We aimed to develop a potent antiviral treatment using CVB3-specific 3p-siRNA and to understand its underlying mechanisms. Virus-specific 3p-siRNA was superior to both conventional virus-specific siRNA with an empty hydroxyl group at the 5' end (OH-siRNA) and nonspecific 3p-siRNA in decreasing viral replication and subsequent cytotoxicity. A single administration of 3p-siRNA dramatically attenuated virus-associated pathological symptoms in mice with no signs of toxicity, and their body weights eventually reached the normal range. Myocardial inflammation and fibrosis were rare, and virus production was greatly reduced. A nonspecific 3p-siRNA showed relatively less protective effect under identical conditions, and a virus-specific OH-siRNA showed no protective effects. We confirmed that virus-specific 3p-siRNA simultaneously activated target-specific gene silencing and type I interferon signaling. We provide a clear proof of concept that coxsackievirus B3-specific 3p-siRNA has 2 distinct modes of action, which significantly enhance antiviral activities with minimal organ damage. This is the first direct demonstration of improved antiviral effects with an immunostimulatory virus-specific siRNA in coxsackievirus myocarditis, and this method could be applied to many virus-related diseases.