Detection of circulating antigen in serum of mice infected with Trichinella spiralis by an IgY-IgM mAb sandwich ELISA.

In this study, a sandwich ELISA based on IgY (egg yolk immunoglobulin) and IgM monoclonal antibody (mAb) against excretory-secretory (ES) antigens of Trichinella spiralis muscle larvae was developed for detection of circulating antigens (CAg) in serum from mice infected with T. spiralis. The IgY-IgM sandwich ELISA involved the use of chicken antibody IgY as a capture antibody and mouse IgM mAb 5A7G4 as a detecting antibody. This assay was able to detect as little as 1 ng/ml of ES antigens added to normal mouse serum. Two groups of BALB/c mice infected with T. spiralis larvae were used: heavily infected mice (20 mice infected with 300 larvae) and lightly infected mice (20 mice infected with 100 larvae) and 10 normal mice as control. The CAg was detectable as early as 4 days post infection (dpi) in the sera from both groups of infected mice, then increased rapidly, reached a peak with detection rate of 100% in heavily infected mice at 10 dpi and 80% in lightly infected mice at 22 dpi, respectively. The anti-Trichinella IgM antibodies was first detected in 40% of heavily infected mice and 20% of lightly infected mice at 8 dpi, and reached a peak positive rate of 100% in heavily infected mice at 16 dpi and in lightly infected mice at 26 dpi, respectively. The novel assay appears to be sensitive for detection of antigens of T. spiralis and valuable to the early diagnosis of trichinellosis.