Establishment of two immunodiagnostic methods for human gnathostomiasis and their application

Objective To establish sensitive and specific immunodiagnostic methods for gnathostomiasis and to use them in practice.Methods The soluble protein of the third-stage larvae of gnathostoma was used as antigen.The Western blot was used to detect the specific antigen recognition bands with relative molecular mass (Mr) 24 000 and 21 000.An indirect ELISA was used as semi-quantitative method to detect specific IgG antibodies in serum samples of patients with gnathostomiasis.Results The immunoblotting results showed that specific antigen recognition bands with Mr 24 000 were detected in all serum samples from 8 positive cases of gnathostomiasis,among which 7 had specific antigen recognition bands with Mr 21 000.Of 30 suspects,18 were detected specific antigen recognition bands between Mr 17 000 and 26 000.Western blotting was also used to detect 25 serum samples from healthy subjects and 25 serum samples from other patients with sparganosi mansoni,angiostrongyliasis cantonensis,paragonimiasis,cysticercosis,or schistosomiasis and neither of the 2 specific antigen recognition bands were observed in the two groups.ELISA results showed IgG positive in all 8 serum samples of patients with gnathostomiasis.The specificity of ELISA for the detection of IgG antibody of gnathostomiasis was 98.0％ (49/50).However,the cross-reaction rate with serum samples from patients with sparganosi mansoni,angiostrongyliasis cantonensis,paragonimiasis,cysticercosis,or schistosomiasis were 20.0％(6/ 30),14.3％(3/21),6.7％(2/30),3.3％(1/30),and 3.3％(1/30),respectively.ELISA results were all positive in 30 suspects,while the Western blot had 18 positive results.Conclusions The Western blot method to separate the specific antigen of gnathostomasis by Mr 24 000 and 21 000 is with good specificity and can be used for differential diagnosis of suspects,but this method is complicated and time-consuming and also requires high specification.ELISA to detect serum specific IgG antibodies with semi-automatic operation procedures has good sensitivity and can be used for screening outpatients and epidemiological survey,but its cross-reaction rate with other helminthiasis is high. Key words: Gnathostoma;  Immunoblotting;  Enzyme-linked immunosorbent assay;  Immunodiagnosis