Dengue Type 2 Virus Subviral Extracellular Particles Produced by a Stably Transfected Mammalian Cell Line and Their Evaluation for a Subunit Vaccine

A dengue subunit vaccine candidate was developed using a mammalian cell line continuously expressing subviral extracellular particles (EPs) of the New Guinea C (NGC) strain of dengue type 2 virus. The cell line, designated D cell line, maintained envelope (E) antigen production for at least 10 passages. The EPs contained an E protein biochemically and antigenically equivalent to authentic E produced by NGC-infected Vero cells. Two immunizations of BALB/c mice with purified EPs containing 100ng or 400ng of E induced moderate levels of neutralizing antibody and anamnestic neutralizing antibody responses were produced when these animals were challenged with dengue virus. The yield of E antigen from D cells was comparable to that from NGC-infected Vero cells. When D cells were transfected with the anti-apoptotic bcl-2 gene, the E antigen release increased approximately two-fold. These results indicate that D cell EPs are a promising non-infectious vaccine antigen for dengue.