Submitted to: American Association of Veterinary Parasitologists
Publication Type: Abstract Only
Publication Acceptance Date: 6/20/2004
Publication Date: 7/21/2004
Citation: Zarlenga, D.S., Duffy, M.S., Appleton, J.A. 2004. Identification of an aspartyl protease from infective larvae as a candidate antigen for vaccination against parelaphostrongylus tenuis. American Association of Veterinary Parasitologists. Interpretive Summary:
Technical Abstract: Parelaphostrongylus tenuis is a neurotropic parasitic nematode of white-tailed deer (Odocoileus virginianus) that causes debilitating neurologic disease in all other North American cervids and in some domestic livestock species. We produced a cDNA library from P. tenuis infective third-stage larvae (L3) in order to identify excretory/secretory (E/S) molecules deployed during infection. We identified from the library, a transcript with sequence similarity to aspartyl proteases from parasitic helminths. The sequence showed similarity to all types of aspartyl proteases, but was most similar with pepsinogens. Semi-quantitative RT-PCR performed on cDNA from male and female adults, L3 and first-stage larvae (L1) of P. tenuis indicated that Pt-apr-1 was upregulated in L3. The gene was cloned into an expression vector for synthesis and purification of the recombinant protein (rPt-APR-1). Antibody generated against rPt-APR-1 detected the native molecule in adult E/S products and somatic extracts of P. tenuis L3. Aspartyl protease activity was documented using a fluorogenic peptide substrate in both somatic extracts and E/S products from adult worms. Optimal enzymatic activity occurred at pH 5.5. Observations from studies of orthologous proteins suggest a role for aspartyl proteases in tissue penetration and digestion of host blood proteins. The upregulated transcription of Pt-apr-1 in L3 as well as the presence of Pt-APR-1 in both L3 protein extracts and adult E/S, supports use of this molecule as a candidate antigen for vaccination against P. tenuis or as a target for drug intervention.