Evaluation of the vaccine efficacy of three digestive protease antigens from Dermanyssus gallinae using an in vivo rearing system

The poultry red mite (PRM), Dermanyssus gallinae, is a hematophagous ectoparasite considered as the major pest in the egg-laying industry. Vaccination is feasible strategy for controlling the haematophagous PRMs. Cathepsin D (CatD), cathepsin L (CatL) and legumain (Lgm) are three endopeptidases participating in digestion of hemoglobin in ticks. The in vitro test and the on-hen feeding device have been used to evaluate the efficacy of vaccines against D. gallinae, however they lacked some of the natural feeding cues for mites, resulting in unreliable results. In the present study, a reliable in vivo rearing system which was nearly close to the natural infestation status of mites was applied to evaluate the efficacy of vaccines against D. gallinae. After vaccinations with rDg-CatD-1, rDg-CatL-1 or rDg-Lgm, chicks developed the antigen-specific IgY immune response to each antigen. The survival rates of D. gallinae in three groups decreased significantly after they fed on the immunized birds. And the oviposition rate and fecundity were significantly reduced by 13.18% and 49.90% in the rDg-CatD-1 immunized group, 5.49% and 38.55% in the rDg-CatL-1 immunized group, respectively. Moreover, immunization with rDg-CatD-1 or rDg-CatL-1 significantly decreased the blood digestion rate of D. gallinae. However, no statistically significant effects on reproduction performance and blood digestion rate of mite were observed in group immunized with rDg-Lgm. Our results demonstrated that immunization with rDg-CatD-1 or rDg-CatL-1 could prevent and control D. gallinae by reducing the survival, reproductive capacity and blood digestion of mite. Importantly, the evaluation system based on the in vivo rearing system was reliable and practical, and it can accurately evaluate the effects of immunization on D. gallinae for pre-screening of potential novel antigens.