Optimal ELISA antigen for the diagnosis of Ascaris suum infection in humans.

Ascarid nematodes, Ascaris suum, Toxocara canis and Toxocara cati, are the most important causative species of larva migrans syndrome (LMS) in humans. Although the diagnosis of ascarid LMS is generally based on serological tests, specific serological tests for A. suum infection have not been fully developed. In the present study, the sensitivity and specificity of three A. suum antigen preparations, i.e., the somatic adult worm antigen (As-SWAP), larval excretory-secretory (ES) antigens derived from infective L3 (AsiL3-ES) and larval ES from tissue migratory L3 (AsmL3-ES), were evaluated for the serodiagnosis of A. suum infection in enzyme-linked immunosorbent assay (ELISA). We found that all A. suum antigen preparations showed positive reaction to all sera from A. suum-infected mice, while only AsmL3-ES obtained 100 % detection of anti-A. suum antibodies in human visceral ascarosis patients. Comparing the reactivity of each A. suum antigen, sera from both A. suum-infected mice and human patients bound to AsiL3-ES significantly weaker than As-SWAP and AsmL3-ES. Moreover, the OD450 values of ELISA with the A. suum antigen preparations and T. canis larval ES antigen (TciL3-ES) were compared in order to discriminate between ascarosis and toxocarosis. Linear discriminant analysis showed that diagnosis based on TciL3-ES and AsmL3-ES ELISA gave the most reliable result for the discrimination of infecting species. In conclusion, the application of AsmL3-ES antigen in ELISA can be recommended for the serodiagnosis of A. suum infection in humans.