Prokaryotic Expression and Serodiagnostic Potential of Glyceraldehyde-3-Phosphate Dehydrogenase and Thioredoxin Peroxidase from Baylisascaris schroederi.

, a roundworm parasite of giant pandas, badly affects the health of its hosts. Diagnosis of this disease currently depends mainly on sedimentation floatation and Polymerase Chain Reaction (PCR) methods to detect the eggs. However, neither of these methods is suitable for diagnosis of early-stage panda baylisascariasis and no information on early diagnosis of this disease is available so far. Therefore, to develop an effective serologic diagnostic method, this study produced recombinant glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and thioredoxin peroxidase (Tpx) proteins from using a prokaryotic expression system. We determined the immunological characteristics of these proteins and their location in the parasite. Indirect enzyme-linked immunosorbent assays (ELISAs) were established to detect infection in giant pandas based on GAPDH and Tpx respectively. The open reading frame of the gene (1083 bp) encoded a 39 kDa protein, while the predicted molecular weight of Tpx (588 bp) was 21.6 kDa. Western-blotting analysis revealed that both recombinant proteins could be recognized with positive serum of pandas infected with . Immunohistochemical staining showed that the endogenous GAPDH of was widely distributed in the worm while Tpx was mainly localized in the muscle, eggs, gut wall, uterus wall and hypodermis. Serological tests showed that the GAPDH-based indirect ELISA had a sensitivity of 95.83% and specificity of 100%, while the test using Tpx as the antigen had sensitivity of 75% and specificity of 91.7%. Thus, Tpx is unsuitable as a diagnostic antigen for baylisascariasis, but GAPDH is a good candidate diagnostic antigen for in pandas.