Characterization of a lipocalin-like molecule from Dermanyssus gallinae as a potential vaccine antigen.

Poultry red mites (PRMs, Dermanyssus gallinae) are hematophagous ectoparasites of chickens that pose a significant threat to the egg-laying industry. The emergence of acaricide-resistant PRMs raises the demand for alternative control approaches such as vaccination. However, several vaccine antigens have failed to suppress the growth of PRM populations in field trials due to difficulties in maintaining antibody levels. In ticks, the molecules exposed to the host, such as lipocalins, can facilitate antibody production, and are therefore considered advantageous as vaccine antigens. Therefore, we focused on a lipocalin-like molecule (Dg-Lipocalin) identified from an RNA-seq analysis reported by Fujisawa et al. (2020) and analyzed its exposure to the host and potential as a vaccine antigen. Western blotting using 500-fold diluted plasma of chickens from PRM-contaminated farms revealed the presence of antibodies against Dg-Lipocalin, suggesting its exposure to the host. To evaluate its potential as a vaccine antigen, PRMs were artificially fed immune plasma with 32,000- to 64,000-fold antibody titers or plasma from PBS-inoculated control chickens, and their mortality was observed for 7 days. In experiment 1, the immune plasma significantly increased PRM mortality compared to the control plasma. However, these effects were not observed in experiment 2, although the total mortality was significantly increased in immune plasma-fed PRMs. Thus, the efficacy of Dg-Lipocalin appears to be limited; however, its exposure to the host may result in sustained antibody titers. Further investigation is required to evaluate its feasibility.