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Abstract
Developing a comprehensive vaccine for Dengue virus (DENV) has been challenging. Any potential vaccine needs to protect against strains from all four serotypes of the virus to avoid potential antibody dependent enhancement (ADE). ADE can occur when pre-existing antibodies to a virus from one DENV serotype do not neutralize, but enhance a heterotypic infection of a DENV from another serotype. Therefore, it is critical to produce a vaccine against viruses representing all four DENV serotypes without enhancing disease. In the current study, we developed and tested DENV subviral particle (SVP) vaccine targeting the envelope (E) glycoprotein by designing consensus sequences using computationally-optimized broadly reactive antigen (COBRA) methodology.
DENV E sequences were obtained from GenBank and a layered, consensus-building approach was used to derive four final COBRA DENV sequences. COBRA and wild-type SVPs were expressed from 293T cells using a mammalian expression vector encoding prM-E genes. Female C57BL/6 mice (age 6-8 weeks) were vaccinated intramuscularly three times at 4 week intervals with 100mg total SVP plus Imject Alum. Vaccines were prepared as individual or tetravalent SVP formulations. Immune sera were collected and total IgG antibody titers to DENV E were analyzed by ELISA and the ability to prevent virus infection in vitro was assessed in a focus reduction neutralization test (FRNT50) against a panel of 12 prototype and modern strains from all four serotypes.
Mice vaccinated with wild type DENV SVPs expressed anti-E IgG antibodies that were specific to strains in each homologous serotype. The elicited antibodies neutralized serotype specific viruses. COBRA DENV SVPs elicited a broader breadth of antibodies that neutralized various strains across all four serotypes. Similar results were seen in rhesus macaques (Macca mulata) that were immunologically naïve to DENV or pre-immune with antibodies to DENV. One COBRA DENV E immunogen neutralized all 12 strains of DENV in vitro, comparable to tetravalent SVP vaccination. This is a promising vaccine candidate based on broad protection against strains representing all four serotypes of DENV in both naïve and pre-immune populations.
DENV E sequences were obtained from GenBank and a layered, consensus-building approach was used to derive four final COBRA DENV sequences. COBRA and wild-type SVPs were expressed from 293T cells using a mammalian expression vector encoding prM-E genes. Female C57BL/6 mice (age 6-8 weeks) were vaccinated intramuscularly three times at 4 week intervals with 100mg total SVP plus Imject Alum. Vaccines were prepared as individual or tetravalent SVP formulations. Immune sera were collected and total IgG antibody titers to DENV E were analyzed by ELISA and the ability to prevent virus infection in vitro was assessed in a focus reduction neutralization test (FRNT50) against a panel of 12 prototype and modern strains from all four serotypes.
Mice vaccinated with wild type DENV SVPs expressed anti-E IgG antibodies that were specific to strains in each homologous serotype. The elicited antibodies neutralized serotype specific viruses. COBRA DENV SVPs elicited a broader breadth of antibodies that neutralized various strains across all four serotypes. Similar results were seen in rhesus macaques (Macca mulata) that were immunologically naïve to DENV or pre-immune with antibodies to DENV. One COBRA DENV E immunogen neutralized all 12 strains of DENV in vitro, comparable to tetravalent SVP vaccination. This is a promising vaccine candidate based on broad protection against strains representing all four serotypes of DENV in both naïve and pre-immune populations.