Comparison of effects of multiple adjuvants and immunization routes on the immunogenicity and protection of HSV-2 gD subunit vaccine

Genital herpes caused by herpes simplex virus type 2 (HSV-2) poses a global health issue. HSV-2 infection increases the risk of acquiring HIV infection. Studies have demonstrated that HSV-2 subunit vaccines have potential benefits, but require adjuvants to induce a balanced Th1/Th2 response. To develop a novel, effective vaccine, in this study, a truncated glycoprotein D (aa 1–285) of HSV-2 was formulated with an Al(OH)3 adjuvant, three squalene adjuvants, zMF59, zAS03, and zAS02, or a mucosal adjuvant, bacterium-like particles (BLPs). The immunogenicity of these subunit vaccines was evaluated in mice. After three immunizations, vaccines formulated with Al(OH)3, zMF59, zAS03, and zAS02 (intramuscularly) induced higher titers of neutralizing antibody than that formulated without adjuvant, and in particular, mice immunized with the vaccine plus zAS02 had the highest neutralizing antibody titers and tended to produce a more balanced immune reaction than others. Intranasal gD2-PA-BLPs also induced excellent IgA levels and a more balanced Th1 and Th2 responses than intranasal gD2. After challenge with a lethal dose of HSV-2, all five adjuvants exhibited a positive effect in improving the survival rate. zAS02 and gD2-PA-BLPs enhanced survival by 50% and 25%, respectively, when compared with the vaccine without adjuvant. zAS02 was the only adjuvant that resulted in complete vaginal virus clearance and genital lesion healing within eight days. These results demonstrate the potential of using zAS02 as a subunit vaccine adjuvant, and BLPs as a mucosal vaccine adjuvant.