Recombinant Human Cytomegalovirus Vaccines Expressing Immunodominant IE1/pp65/pp150 Epitopes Elicit Robust Innate and Adaptive Immunity

Background/Objectives: Human cytomegalovirus (HCMV) causes severe disease primarily in immunocompromised and immunodeficient individuals. First-line antivirals are limited by side effects and the risk of acquired resistance. The urgent need for a safe and effective treatment or vaccine to generate strong cellular and humoral immunity against HCMV prompted our research. Methods: We applied bioinformatics tools to predict the dominant T and B-cell epitopes of key HCMV proteins: immediate-early protein 1 (IE1), phosphoprotein 65 (pp65), and phosphoprotein 150 (pp150). We then embarked on an exploration of two efficacious vaccine platforms. One was a human adenovirus (HAdv)-based vaccine named RHAdvIE1/pp65/pp150, and the other was a recombinant subunit vaccine (receptor-binding domain, RBD). To optimize the vaccination strategy, we investigated the effectiveness of a heterologous prime-boost approach and assessed the immunological impact of these HCMV vaccine candidates using mouse models. Results: We observed that RHAdvIE1/pp65/pp150 up-regulates the expression of antigen-presenting cell surface markers and cytokines through the MKK7/JNK signaling pathway. Activation of innate immunity promotes the migration of dendritic cell subsets and macrophage polarization, regulating the downstream Th1-biased polarization. Sequential immunization with RHAdvIE1/pp65/pp150 followed by RBD administration induced an effective T cell response, leading to the production of various cytokines, the development of integrated memory cells, and a specific increased in neutralizing antibodies. Moreover, the heterologous prime-boost regimen of the RHAdvIE1/pp65/pp150 vaccine also improved the Th1-biased T cell response. Conclusions: Therefore, RHAdvIE1/pp65/pp150 and RBD vaccines synergistically stimulate robust cellular and humoral immunity. These findings offer innovative insights into the design of vaccination strategies against HCMV infection.