The genome of dengue virus and other members of the flavivirus group consists of a positive strand 42S RNA 10-12,000 bases in length. A 42S mRNA produced in infected cells codes for the three structural proteins V1, V2, and V3 which are also designated the envelope, core and matrix proteins, respectively. The remaining approximately 70% of the viral genome encodes a number of as yet unidentified non-structural proteins. The locations on the genome coding for the dengue structural and non-structural proteins have not been mapped and the functional role that each of these proteins plays remains to be determined. Extension of cloned DNA by "genome walking" has thus far yielded dengue type 4 cDNA of 9 kilobases in 5 overlapping segments. The 5 clones are currently being extended in order to complete our cloning of the dengue genome. The clones are also being sequenced in order to study the gene organization of dengue virus. We plan to approach the mapping and protein analysis of dengue virus by using the recently developed baculovirus vector-host cell system for expressing cloned DNA segments. Expressed polypeptides will be used to immunize animals for preparation of antisera and the antisera will in turn be used for identifying viral proteins present in infected cells. In this manner, the expressed gene product will identify the viral structural or non-structural protein each gene encodes and allow us to map the position of each gene on the dengue genome. In addition, the antisera produced from expressed DNA segements should be useful for identifying the antigenic determinants of dengue virus.