Nodavirus-based RNA replicon vaccines for tick-borne encephalitis virus

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Tick-borne encephalitis (TBE) viruses are important human pathogens, particularly in Europe and Asia; one TBE virus, Powassan virus, is endemic to North America. TBE viruses, which are transmitted by ticks, can cause fatal encephalitis in humans. Russian spring-summer encephalitis virus and Central European Encephalitis virus result in mortality of 20% and 1-2%, respectively. In each case, survivors are at risk for developing neurological sequelae. An inactivated virus vaccine protects individuals exposed to ticks in Europe but this vaccine has not been approved for use in the United States. Despite the existence of the vaccine, several thousand cases of TBE encephalitis are reported each year. The National Institute for Allergy and Infectious Disease (NIAID) Biodefense Research Agenda identifies TBE as a Category C priority pathogen on the basis of its transmission by an arthropod host, its infectivity on aerosolized exposure, and its potential threat to public health. Also, of particular concern is the possibility that TBE viruses might be used as agents of bioterrorism. Therefore, development of a vaccine against TBEV consistent with the overall goals of the WRCE as well as a national biodefense priority. The goals of this Career Development Award proposal are to develop a candidate vaccine for tick-borne encephalitis virus and to test its immunogenicity in mice. This proposal incorporates three novel concepts, namely the use of Nodamura virus (NoV) RNA replicons to amplify TBEV mRNAs in the yeast Saccharomyces cerevisiae, the inclusion of an NoV protein that suppresses host cellular defenses like RNA interference, and inoculation of animals with purified total yeast RNA containing amplified NoV-TBEV RNAs. The specific aims of this proposal are to: 1. Construct NoV RNA2-based replicons that contain TBEV structural (glycoprotein E; M) or nonstructural (NS1) proteins and determine the extent to which RNA replication amplifies NoV2-gpE, NoV-M and NoVNS1 mRNA and protein levels in yeast and mammalian cells. 2. Determine the extent to which suppression of RNA interference by an NoV nonstructural protein enhances the efficiency of protein expression from yeast-derived NoV RNA replicons. 3. Evaluate the TBEV structural (gpE, M) and nonstructural (NS1) proteins as potential vaccine candidates by defining the humoral and cell-mediated immune responses to these proteins elicited in inoculated mice. Relevance to public health. Tick-borne encephalitis (TBE) viruses are serious human pathogens that pose a threat to our public health and our national biosafety. Our goal is to develop safe and effective vaccine candidates that will prevent the spread of TBE.