Strategies of Dengue Vaccine Development by W. H. O. Using New Biotechnology

Dengue fever and dengue haemorrhagic fever (DHF) with shock syndrome are found in tropical and subtropical areas of Asia, Africa, Western Pacific and Central and South America. DHF is one of the major causes of hospitalization of children in urban of these areas. Control of the mosquito is the only means available now to curb the disease. Therefore a vaccine is urgently needed. Sequential infections with different dengue virus serotypes represent a risk factor for DHF. Prior immunity to a heterologus serotype enhance virus infection of another serotype in macrophages and monocytes. Thus, the approach of the Steering Committee (SC) of W. H. O. is to develop a tetravalent candidate vaccine including 4 serotype antigens or to engineer dengue vaccines without the component of immune-mediated enhancement. The strategic plan of the SC had included (a) definition of protective epitopes; (b) expression of protective epitopes; (c) definition of virulence in molecular terms. In view of the fruits, the following strategic plans of the SC were included. i. Infectious clone research using parental and candidate vaccine strains and definition of virulence and attenuation in molecular terms. ii. Construction and expression of protective immunogens by genetic engineering techniques. iii. Development of animal model for DHF. iv. Development of candidate vaccines