Psoroptes ovis-Early Immunoreactive Protein (Pso-EIP-1) a novel diagnostic antigen for sheep scab

Aims Serodiagnosis of sheep scab is an established diagnostic method and has become popular in recent years. However, the current diagnostic antigen, Pso o 2, has shown promise as a component of a recombinant vaccine for scab, making it incompatible with discriminating between infected and vaccinated animals (DIVA). Here, we describe the discovery and characterization of a novelPsoroptes ovisimmunodiagnostic antigen,P. ovis-Early Immunoreactive Protein-1 (Pso-EIP-1). Methods and Results Pso-EIP-1 is a highly abundant member of a six-gene family with no known homologs, indicating its potential uniqueness toP. ovis. Expression of recombinant Pso-EIP-1 (rPso-EIP-1) required a C-terminal fusion protein for stability and specific IgG immunoreactivity against rPso-EIP-1 was observed in sheep serum from 1 to 2 weeks post-infestation, indicating its highly immunogenic nature. Two of the three in silico-predicted B-cell epitopes of Pso-EIP-1 were confirmed by in vitro epitope mapping and, in a direct comparison by ELISA, Pso-EIP-1 performed to the same levels as Pso o 2 in terms of sensitivity, specificity and ability to diagnoseP. ovison sheep within 2 weeks of infestation. Conclusion Pso-EIP-1 represents a novel diagnostic antigen for sheep scab with comparable levels of sensitivity and specificity to the existing Pso o 2 antigen.