Detection of Trichinella spiralis circulating antigens in serum of experimentally infected mice by an IgY-mAb sandwich ELISA

In this study, a sandwich enzyme-linked immunosorbent assay (ELISA) based on IgY (egg yolk immunoglobulin) and 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-mAb sandwich ELISA involved the use of chicken antibody IgY as a capture antibody and mouse mAb 35B9 as a detecting antibody. This method was able to detect as little as 1 ng/mL of ES antigens added to normal mouse serum. A group of 15 mice was orally inoculated with 500 T. spiralis muscle larvae per animal and the serum samples were daily taken during 1-49 days post-infection (dpi). The level of CAg was detectable as early as 3 dpi in the sera from infected mice, increased gradually, and reached two peaks with detection rate of 40% at 13 dpi and 100% at 24 dpi, respectively. The anti-Trichinella antibodies was first detected in 33.3% of the infected mice at 3 week post-infection (wpi), and reached a peak positive rate of 100% at 5 wpi. Moreover, the infected mice were treated with abendazole at 5 weeks post-infection, and the serum levels of CAg in treated group began to increase rapidly at 2 days post-treatment (dpt) and reached a peak with detection rate of 100% (10/10) at 8 dpt, and then decreased gradually. By 42 dpt, the CAg levels decreased to the undetected level, but the anti- Trichinella antibodies were still detected in 100% of the infected mice. The novel assay appears to be sensitive for detection of antigens of T. spiralis and should be valuable to the early diagnosis and evaluation of the efficacy of chemotherapy in trichinellosis.