Prime-boost with Chikungunya virus E2 envelope protein combined with Poly (I:C) induces specific humoral and cellular immune responses.

Chikungunya virus (CHIKV) is an arbovirus transmitted to humans mainly by the bite of infected and mosquitoes. CHIKV illness is characterized by fever and long-lasting arthritic symptoms, and in some cases it is a deadly disease. The CHIKV envelope E2 (E2) glycoprotein is crucial for virus attachment to the cell. Furthermore, E2 is the immunodominant protein and the main target of neutralizing antibodies. To date, there is no available prophylactic vaccine or specific treatment against CHIKV infection. Here, we designed and produced a DNA vaccine and a recombinant protein containing a consensus sequence of E2. C57BL/6 mice immunized twice with the E2 recombinant protein in the presence of the adjuvant Poly (I:C) induced the highest E2-specific humoral and cellular immune responses, while the immunization with the homologous DNA vaccine pVAX-E2 was able to induce specific IFN-γ producing cells. The heterologous prime-boost strategy was also able to induce specific cellular and humoral immune responses that were, in general, lower than the responses induced by the homologous E2 recombinant protein immunization. Furthermore, recombinant E2 induced the highest titers of neutralizing antibodies. Collectively, we believe this is the first report to analyze E2-specific humoral and cellular immune responses after immunization with E2 recombinant protein and DNA pVAX-E2 vaccine platforms.