Assessment of cathepsin D and L-like proteinases of poultry red mite, Dermanyssus gallinae (De Geer), as potential vaccine antigens

Vaccination is a feasible strategy for controlling the haematophagous poultry red mite Dermanyssus gallinae. A cDNA library enriched for genes upregulated after feeding was created to identify potential vaccine antigens. From this library, a gene (Dg-CatD-1) encoding a 383 amino acid protein (Dg-CatD-1) with homology to cathepsin D lysosomal aspartyl proteinases was identified as a potential vaccine candidate. A second gene (Dg-CatL-1) encoding a 341 amino acid protein (Dg-CatL-1) with homology to cathepsin L cysteine proteinases was also selected for further study. IgY obtained from naturally infested hens failed to detect Dg-CatD-1 suggesting that it is a concealed antigen. Conversely, Dg-CatL-1 was detected by IgY derived from natural-infestation, indicating that infested hens are exposed to Dg-CatL-1. Mortality rates 120 h after mites had been fed anti-Dg-CatD-1 were significantly higher than those fed control IgY (PF<0·01). In a survival analysis, fitting a proportional hazards model to the time of death of mites, anti-Dg-CatD-1 and anti-Dg-CatL-1 IgY had 4·42 and 2·13 times higher risks of dying compared with controls (PF<0·05). Dg-CatD-1 and L-1 both have potential as vaccine antigens as part of a multi-component vaccine and have the potential to be improved as vaccine antigens using alternative expression systems.