PRV gD-Based DNA Vaccine Candidates Adjuvanted with cGAS, UniSTING, or IFN-α Enhance Protective Immunity

Pseudorabies virus (PRV), a major swine pathogen, causes severe neurological, respiratory, and reproductive disorders, resulting in substantial economic losses to the global swine industry. Previous studies have shown that the gD glycoprotein of PRV has an effective protective effect. In this study, we constructed a plasmid DNA vaccine (pVAX1-GD-Fc) encoding a gD protein fused with pig IgG Fc and evaluated the adjuvant effects of porcine cGAS, the universal STING complex mimic (UniSTING), or IFN-α in mice. The mice were immunized three times (days 0, 14, and 21) with pVAX1-GD-Fc in the presence or absence of an adjuvant, followed by lethal challenge with PRV-HLJ8 3 days after the final immunization. The results revealed that the pVAX1-GD-Fc group exhibited 20% mortality (1/5 mice) on day 7 postchallenge, and all adjuvanted groups achieved 100% survival during the 14-day observation period. Flow cytometric analysis of splenocytes one week after the second immunization revealed significantly greater CD8+ T cell proportions in the adjuvant groups than in both the mock and pVAX1-GD-Fc-only control groups (p < 0.01). Furthermore, T cell proliferation assays demonstrated a significantly increased stimulation index in the adjuvant-treated mice, confirming enhanced cellular immunity. These findings demonstrate that cGAS, UniSTING, and IFN-α can serve as effective vaccine adjuvants to rapidly enhance cellular immune responses to PRV, highlighting their potential application in veterinary vaccines.