Live attenuated dengue vaccine development: Experience of Mahidol University

抄録

In 1980, Mahidol University (MU) committed to develop a live attenuated tetravalent dengue vaccine. DEN-1, -2 and -4 obtained from DHF patients were serially passaged in certified primary dog kidney (PDK) cells. DEN-3 obtained from DF patients was first passaged in green monkey kidney (GMK) cells and then in certified Fetal Rhesus Lung (FRhL) cells. The degree of attenuation was empirically based on certain biological markers.

The monovalent live attenuated viruses - DEN-1 PDK13, DEN-2 PDK53, DEN-3 PGMK30/FRhL-3 and DEN-4 PDK48 - were first tested in flavivirus non-immune adult subjects, followed by bivalent, trivalent and tetravalent vaccine trial tests. All vaccine recipients developed either a mild or no reaction to the vaccine but elicited satisfactory immunogenicity.

Homotypic neutralizing antibody began to rise 15 days after immunization in vaccine recipients who had no pre-existing antibodies to dengue or Japanese encephalitis (JE) viruses. In the subjects with pre-existing heterologous antibodies against dengue serotypes of JE viruses, the neutralizing antibodies began to rise earlier (7 days after immunization); the peak titers at 1 month post-immunization were many fold higher that the titers seen in non-immune volunteers. The neutralizing antibodies were homotypic in the flavivirus naïve volunteers receiving monovalent vaccines, and the titers remained at about the same level for 3 years with only slight reduction. After 3 years, heterotypic antibodies against the other serotypes began to appear, raising a possibility that the vaccinees might have experienced a subsequent natural infection. For the bivalent and the trivalent formulation, the vaccinees displayed homotypic neutralizing antibodies, with the exception of the bivalent DEN-1-DEN-4 which showed heterotypic antibodies against DEN-2 and DEN-3 as well. These heterotypic antibodies disappeared after 1 year.

None of the small group of vaccinees with pre-existing dengue antibody showed severe reactions to the vaccines. Follow-up physical examination was possible in about half of the vaccinees, some of whom had been immunized nearly 10 years earlier. There were no apparent sequelae in the follow-up group.