EgLDH as a Novel Target: Design and Preliminary Efficacy Assessment of a DNA Vaccine

(1) Background: Echinococcosis is a significant zoonotic disease that the World Health Organization (WHO) aims to eliminate by 2050. Current drug-based control faces challenges such as drug resistance, highlighting the urgent need to develop vaccines as a supplementary strategy. Although some progress has been made in the study of intermediate host vaccines using antigens such as Eg95, there is still no commercial vaccine available for the definitive host, canines-which are crucial for transmission-and it is not yet suitable for large-scale use. While vaccine studies targeting the key enzyme lactate dehydrogenase (LDH) in parasite energy metabolism remain scarce, they represent a promising area of potential. (2) Methods: The B cell antigen epitopes of LDH were analyzed, and prokaryotic (pET-28a-EgLDH) and eukaryotic (pVAX1-EgLDH) DNA vaccine expression vectors were constructed. After verifying expression and immunogenicity via qRT-PCR and WB, in vitro validation was performed in 293T cells. Mice were immunized with the vaccine and then challenged with the parasite; blood was collected from the orbital sinus, and IgG levels and cytokines were measured by ELISA. Protective effects were assessed through counting liver cysts and histopathological analysis. (3) Results: We constructed the pVAX1-EgLDH plasmid and immunized Kunming (KM) mice. Compared with the PBS control group, the vaccine group showed an 80.95% reduction in liver cysts (Quil-A group: 19.00%). Histopathological analysis indicated no significant liver damage, although the spleens in the vaccine group were smaller. ELISA results demonstrated an increase in total IgG (p < 0.05), and cytokine analysis showed elevated levels of IL-1 (p < 0.01), IL-4, and IL-10 (p < 0.001), whereas IL-5 and IFN-γ showed no significant changes (p > 0.05). (4) Conclusions: The EgLDH DNA vaccine can elicit a specific immune response and significantly reduce cyst burden, providing theoretical basis and data support for its use as a candidate vaccine for the prevention and control of Echinococcosis.