Comparison of fusion protein and excretory-secretory antigens of Toxocara canis in detection of antibodies in experimental toxocariasis

Abstract

The immunodiagnosis of visceral larva migrans due to Toxocara canis infection is based on the detection of specific antibodies with the enzyme-linked immunoassay (EIA) using excretory-secretory (ES) antigens of second stage larvae of the parasite. As ES antigens are cumbersome to produce, a specific recombinant protein would be an attractive alternative. A recombinant protein produced previously (Yamasaki et al., 1998) was compared with ES antigens in the EIA and immunoblot detection of antibodies in the sera of Macaca fascicularis experimentally infected with 5000 - 10000 T.canis embryonated eggs. The EIA using recombinant protein and ES antigens gave optical density readings that correlated significantly well with each other (p<0.02). Antibody response increased rapidly from week 1, and peaked at 6-8 weeks post-infection. In immunoblot assays, infected monkey sera at 4-8 weeks post-infection, recognized the recombinant protein and produced a single prominent band at 38 kDa relative molecular weight. In contrast, multiple bands between 38 - 98 kDa were obtained with ES antigens. Sera from uninfected control monkeys and pre-infection sera did not produce these bands. In conclusion, the recombinant protein is suitable for use in the ElA and immunoblot assay for the detection of specific anti-T. canis antibodies.