Co-expression of Japanese encephalitis virus prM–E–NS1 antigen with granulocyte-macrophage colony-stimulating factor enhances humoral and anti-virus immunity after DNA vaccination
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Abstract
Japanese encephalitis virus (JEV) is an agent of Japanese encephalitis, and granulocyte-macrophage
colony-stimulating factor (GM-CSF) is an attractive DNA vaccine adjuvant for its antigen
presentation. In the present study, we have constructed DNA vaccines that carried
JEV prM-E-NS1 genes with or without the GM-CSF gene. Immunization with the bicistronic
plasmid pCAG-JEGM that co-expresses GM-CSF and viral prM-E-NS1, resulted in the highest
IgG response and sufficient protection against virus-challenged BALB/c mice. However,
much to our surprise, co-inoculation of the GM-CSF plasmid with the pCAG-JE plasmid
expressing viral prM-E-NS1 lead to a low antibody titer and a relatively low survival
rate. Moreover, anamnestic antibody-mediated protection played a dominant role in
the mice JEV challenge model, according to the enhancement of post-challenge neutralizing
antibody titers and further adoptive transfer experiments. Taken together, this study
should encourage further development of JEV DNA vaccine strategies and caution against
the use of cytokines as an adjuvant.