Immunogenicity of a recombinant envelope domain III protein of dengue virus type-4 with various adjuvants in mice.

Dengue fever, a mosquito borne viral disease, has become a major public health problem with dramatic expansion in recent decades. Several dengue vaccines are at developing stage, none are yet available for humans. There is no vaccine or antiviral therapy available for dengue fever till date. Domain III of envelope protein is involved in binding to host receptors and it contains type and subtype-specific epitopes that elicit virus neutralizing antibodies. Hence domain III is an attractive vaccine candidate. In the present study we report the immunomodulatory potential of refolded D4EIII protein in combination with various adjuvants (Freunds Complete adjuvant, Montanide ISA720, Alum). Mice were tested for humoral immune responses by ELISA, immunofluorescence assay and plaque reduction neutralization test. Cell mediated immune response was tested by lymphocyte proliferation assay and cytokine profiling. All the formulations resulted in high antibody titers that neutralized the virus entry in vitro. D4EIII in combination with montanide ISA720 and Feuds complete adjuvant gave highest antibody endpoint titers followed by alum. The level of antigen-stimulated splenocyte proliferation and cytokine production was comparable to that obtained from Con A stimulation and cytokine profiling of stimulated splenocyte culture supernatants indicated that all the adjuvant formulations have induced cell mediated immune response as well. These findings suggest that D4EIII in combination with compatible adjuvants is highly immunogenic and can elicit high titer neutralizing antibodies and cell mediated immune response which plays an important role in intracellular infections, which proves that refolded D4EIII can be a potential vaccine candidate.