Molecular antigenic structure of flaviviruses

The focus of this project is the elucidation of molecular details of the antigenic structure of flaviviruses in order to understand the structural basis of antibody-mediated virus neutralization and antigenic cross-reactivity. The genus flavivirus in the family flaviviridae comprises about 70 different viruses, several of which are important human pathogens, including yellow fever virus, Japanese encephalitis virus, dengue virus, West Nile virus, and tick-borne encephalitis virus. Flaviviruses are small membrane-containing viruses and the envelope protein E is the major target for neutralizing antibodies. Although even the most distantly related flaviviruses have about 40% of identical amino acids in their E proteins and antigenic cross-reactivity has been described to occur between all flaviviruses, cross-neutralization is restricted to more closely related members that are grouped together in so-called serocomplexes. The induction of cross-reactive but non-neutralizing antibodies can have significant biological implications, including the phenomena of antibody-dependent enhancement of infection (ADE) and original antigenic sin (OAS). Both phenomena may pose problems in the course of sequential flavivirus infections and/or vaccinations. It is the principal goal of this proposal to exploit the known atomic structure of the flavivirus E protein for identifying those sequence elements that are responsible for the induction of neutralizing as well as cross-reactive, non-neutralizing antibodies. For this purpose we will make use of different recombinant expression systems, site-specific mutagenesis, monoclonal and polyclonal antibody binding studies, sequential immunization protocols, and X-ray structure determination of E-protein Fab complexes. The outcome of these investigations will lay the foundations for a structural understanding of the antigenic and immunogenic properties of flaviviruses, which can have a significant impact on the use and development of flavivirus vaccines. It is expected that the significance of the results obtained with flaviviruses will extend to other groups of antigenically related viral and nonviral pathogens in which cross-reactivity plays an important role.

The focus of this project is the elucidation of molecular details of the antigenic structure of flaviviruses in order to understand the structural basis of antibody-mediated virus neutralization and antigenic cross-reactivity. The genus flavivirus in the family flaviviridae comprises about 70 different viruses, several of which are important human pathogens, including yellow fever virus, Japanese encephalitis virus, dengue virus, West Nile virus, and tick-borne encephalitis virus. Flaviviruses are small membrane-containing viruses and the envelope protein E is the major target for neutralizing antibodies. Although even the most distantly related flaviviruses have about 40% of identical amino acids in their E proteins and antigenic cross-reactivity has been described to occur between all flaviviruses, cross-neutralization is restricted to more closely related members that are grouped together in so-called serocomplexes. The induction of cross-reactive but non-neutralizing antibodies can have significant biological implications, including the phenomena of antibody-dependent enhancement of infection (ADE) and original antigenic sin (OAS). Both phenomena may pose problems in the course of sequential flavivirus infections and/or vaccinations. It is the principal goal of this proposal to exploit the known atomic structure of the flavivirus E protein for identifying those sequence elements that are responsible for the induction of neutralizing as well as cross-reactive, non-neutralizing antibodies. For this purpose we will make use of different recombinant expression systems, site-specific mutagenesis, monoclonal and polyclonal antibody binding studies, sequential immunization protocols, and X-ray structure determination of E-protein Fab complexes. The outcome of these investigations will lay the foundations for a structural understanding of the antigenic and immunogenic properties of flaviviruses, which can have a significant impact on the use and development of flavivirus vaccines. It is expected that the significance of the results obtained with flaviviruses will extend to other groups of antigenically related viral and nonviral pathogens in which cross-reactivity plays an important role.