Recombinant antigen-based enzyme-linked immunosorbent assay for diagnosis of Baylisascaris procyonis larva migrans

Abstract

Baylisascaris larva migrans is an important zoonotic disease caused by Baylisascaris procyonis, the raccoon roundworm, and is being increasingly considered in the differential diagnosis of eosinophilic meningoencephalitis in children and young adults. Although a B. procyonis excretory-secretory (BPES) antigen-based enzyme-linked immunosorbent assay (ELISA) and a Western blot assay are useful in the immunodiagnosis of this infection, cross-reactivity remains a major problem. Recently, a recombinant B. procyonis antigen, BpRAG1, was reported for use in the development of improved serological assays for the diagnosis of Baylisascaris larva migrans. In this study, we tested a total of 384 human patient serum samples in a BpRAG1 ELISA, including samples from 20 patients with clinical Baylisascaris larva migrans, 137 patients with other parasitic infections (8 helminth and 4 protozoan), and 227 individuals with unknown/suspected parasitic infections. A sensitivity of 85% and a specificity of 86.9% were observed with the BpRAG1 ELISA, compared to only 39.4% specificity with the BPES ELISA. In addition, the BpRAG1 ELISA had a low degree of cross-reactivity with antibodies to Toxocara infection (25%), while the BPES antigen showed 90.6% cross-reactivity. Based on these results, the BpRAG1 antigen has a high degree of sensitivity and specificity and should be very useful and reliable in the diagnosis and seroepidemiology of Baylisascaris larva migrans by ELISA.

Fig. 1.

Reactivities of serum samples from patients with B. procyonis and Toxocara sp. larva migrans in the B. procyonis ES antigen and BpRAG1 ELISAs. Serum samples from patients with Toxocara infections showed strong reactivity in the BPES ELISA (OD cutoff, 0.250), indicating cross-reactivity, but few of them reacted in the BpRAG1 ELISA, indicating low cross-reactivity in that assay (OD cutoff, 0.200). The single very strong reactor (arrows) is considered to indicate a dual infection with both parasites, which was also confirmed by Western blotting.