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

Parasite Immunol. 2020 Dec;42(12):e12788. doi: 10.1111/pim.12788. Epub 2020 Sep 14.


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 novel Psoroptes ovis immunodiagnostic 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 to P. 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 diagnose P. ovis on 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.

Keywords: antigen; diagnostic; genome; immunoreactive; proteomics; sheep scab; vaccine.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Arthropod Proteins / immunology*
  • Immunoglobulin G / blood
  • Mite Infestations / diagnosis
  • Mite Infestations / veterinary*
  • Psoroptidae / immunology*
  • Recombinant Fusion Proteins / immunology
  • Sensitivity and Specificity
  • Serologic Tests / methods
  • Serologic Tests / veterinary*
  • Sheep
  • Sheep Diseases / diagnosis*


  • Arthropod Proteins
  • Immunoglobulin G
  • Recombinant Fusion Proteins