Poly(D,L-lactide-co-glycolide) nanoparticles significantly enhance the immunoprotective efficacy of Ascaridia galli excretory-secretory antigens.

Ascaridia galli infection causes significant economic losses in poultry, with no available vaccine. This study aimed to develop and evaluate a novel nanovaccine by encapsulating A. galli excretory-secretory antigens (ESAs) in poly(lactic-co-glycolic acid) (PLGA) and chitosan (CS) nanoparticles (NPs), comparing their efficacy to antigens delivered with Freund's adjuvant (FA). One-day-old chicks were randomly allocated into five groups. Three treatment groups were immunized intramuscularly on days 7 and 14 with 200 μg of A. galli ESAs delivered via PLGA NPs, CS NPs, or FA. An infected control group and an uninfected blank control group were also included. All groups except the blank control were challenged with 500 infective A. galli larvae on day 21. On day 77, chickens were euthanized for assessment of worm burden, growth performance, antibody responses (systemic and mucosal), and cytokine profiles. Immunization with ESAs-PLGA NPs induced the most significant reduction in total worm burden (34.38%), which was particularly effective against male worms. This group, along with the ESAs-CS NPs group, also showed a significant improvement in average daily weight gain compared to the infected control. Serologically, both NP groups elicited significantly higher and more sustained levels of serum total IgG and ESAs-specific IgG than the FA group. Crucially, only the ESAs-PLGA NPs significantly enhanced IgG levels in the jejunal mucosa. Furthermore, the ESAs-PLGA NP vaccine consistently promoted the strongest Th2-type immune response, characterized by the highest secretion of IL-4 and IL-13. A. galli ESAs are effective vaccine antigens that confer protection by stimulating IgG antibodies and a Th2-skewed immune response. Encapsulation of ESAs in PLGA NPs significantly enhances this immunoprotective efficacy, superior to both CS NPs and traditional FA, by potentiating systemic and mucosal humoral immunity and amplifying Th2-cell responses. The ESAs-PLGA NP formulation represents a promising vaccine candidate for controlling A. galli in poultry.