Multi-immunodot for rapid differential diagnosis of eosinophilic meningitis due to parasitic infections.

A multi-dot enzyme-linked immunosorbent assay (ELISA) was developed for the rapid and simple differential diagnosis of eosinophilic meningitis due to helminth infections. Ultrafiltered, purified antigens of Parastrongylus (=Angiostrongylus) cantonensis, Gnathostoma spinigerum and Taenia solium metacestodes, the most common parasites that invade the central nervous system and cause eosinophilic pleocytosis, were dotted onto a single nitrocellulose membrane strip. Antigen-coated strips, when blocked with 5% skimmed milk and dried, were stable for at least 6 months at 4 degrees C. With peroxidase conjugated anti-human immunoglobulins and 4-chloro-1-naphthol as a substrate, antibodies in the corresponding patients' sera were clearly detected on the membrane strip as well-defined blue dots. Although cross-reactions between P. cantonensis and G. spinigerum antigens were observed with the use of partially purified antigens, the darkest dot correlated well with the infecting parasites in all cases. This fast, easy and economical multiple dot-blot ELISA method is useful for the differential diagnosis of eosinophilic meningitis caused by parasitic helminths, as semi-purified antigens can be easily obtained by ultrafiltration and used. Further improvements using highly specific parasite antigens may make this multi-immunodot test more suitable for wide-scale use in field studies and diagnostic laboratories.

A dot-blot ELISA comparable to immunoblot for the specific diagnosis of human parastrongyliasis.

A dot-blot enzyme-linked immunosorbent assay (dot-blot ELISA) using an electroeluted 31-kDa glycoprotein from adult worms of Parastrongylus cantonensis as the specific antigen was evaluated for the immunological diagnosis of patients infected with P. cantonensis. The sensitivity and specificity for the detection of serum antibody to P. cantonensis in dot-blot ELISA were both 100%, as determined with serum samples of ten P. cantonensis-infected patients, 60 patients with other related parasitic infections, and 20 uninfected controls. The test was as sensitive and specific as the immunoblot test which revealed a reactive band of 31 kDa. Both the dot-blot ELISA and immunoblot detected all sera from ten P. cantonensis-infected individuals, but not with those of other heterologous parasitoses (gnathostomiasis, toxocariasis, filariasis, paragonimiasis, cysticercosis and malaria) or sera from healthy controls. The dot-blot ELISA is much simpler to perform than the immunoblot technique, and the test can be applied under field conditions where sophisticated facilities are lacking.

Purification of a specific immunodiagnostic Parastrongylus cantonensis antigen by electroelution from SDS-polyacrylamide gels.

A 31-kDa glycoprotein antigen was purified by electrophoresing the crude extract of Parastrongylus cantonensis adult worms in a 12% SDS-polyacrylamide gel, identifying the 31-kDa component with prestained molecular weight standards, cutting the desired gel strip, and then isolating it by electroelution. Antigen fraction of 31 kDa was re-electrophoresed, transferred to a nitrocellulose membrane and found to be reactive with only the sera from patients with parastrongyliasis. No reactive band was observed with the sera from other related parasitic infections, eg, gnathostomiasis, toxocariasis, filariasis, paragonimiasis, cysticercosis and malaria, and the normal healthy control sera. This antigen fraction isolated showed 100% sensitivity and 100% specificity in the enzyme-linked immunosorbent assay (ELISA) for the detection of 31-kDa specific antibody in the sera from patients with parastrongyliasis. The P. cantonensis antigen of 31 kDa has been obtained by this means with a high degree of purity and applied successfully in conventional ELISA for the specific immunodiagnosis of human parastrongyliasis.