Investigating the Efficacy of DNA Vaccines Against Viral Diseases in Veterinary Medicine

Abstract

Viral diseases remain a significant threat to animal health and productivity, underscoring the need for effective, broadly applicable vaccination technologies in veterinary medicine. In this study, we evaluated a plasmid DNA vaccine approach against different viral infections in three veterinary species such as broiler chicken (Gallus gallus domesticus), dogs (Canis lupus familiaris), and goats (Capra aegagrus hircus), using an experimental randomized controlled trial design. A total of 135 animals were grouped as DNA vaccine, conventional vaccine, or control groups and distributed with fifteen individuals per group per species. After a challenge with the homologous virus on day 42 after vaccination, results were assessed based on clinical, immunological, and virological criteria. No mortality was observed in DNA-immunized animals of all species tested, while those inoculated by the traditional vaccination method showed a 6.7% death rate, and controls had 20.0–26.7% mortality rates. The proportion of animals showing clinical symptoms was much lower in DNA-vaccinated groups (6.7–13.3%) than in conventional (26.7–40.0%) or control groups (60.0–73.3%). Humoral responses were consistently high post-DNA vaccination, and the mean virus-specific ELISA antibody titres achieved 3.4−3.5 log₁₀, compared with 2.7−2.9 log₁₀ in traditional vaccine groups and ≤0.5 log₁₀ in challenge controls at day 56. DNA immunization resulted in potent cell-mediated immunity, such as increased IFN-γ levels (136.4-148.9 pg/ml) that were considerably higher compared to those of traditional groups (96.1-101.4 pg/ml) and controls (22.5-25.3 pg/ml). Virological studies indicated significantly lower peak viral loads with DNA vaccinees (1.6–2.1 × 10³ copies/mL) compared to conventional (3.2–4.7 × 10⁴ copies/mL) and control groups (1.8–2.3 × 10⁶ copies/mL), in addition to a significantly shorter period of viral shedding (2.0–2.3 days versus 4.6-5 weeks, and −9 weeks, respectively). These results show that in many animal species, these DNA vaccines are more clinically protective, immunogenic, and better able to control the viruses, demonstrating the scalability of this approach as a veterinary vaccine.