Application of Toxocara canis excretory-secretory antigens and IgG subclass antibodies (IgG1-4) in serodiagnostic assays of human toxocariasis.
A major problem in the serodiagnosis of human toxocariasis in tropical countries is cross-reaction with antibodies to other helminthic diseases and a lack of sensitivity. The majority of tests currently available use total IgG and, in this study, the use of peroxidase-conjugated anti-human IgG subclass antibodies (IgG1-4) was compared with total IgG for the diagnosis of human toxocariasis by using Toxocara excretory-secretory (TES) antigens in an enzyme-linked immunosorbent assay (ELISA) format. All four IgG subclass antibodies gave approximately 10-fold increases in optical density (OD) values for 50 toxocariasis patients compared to 29 healthy normals; this was significantly greater than the approximate doubling of OD values seen in the total IgG-ELISA format. IgG2 gave by far the greatest sensitivity (values: IgG, 50%; IgG1, 60%; IgG2, 98%; IgG3, 78%; IgG4, 64%). Significant cross-reactivity using all IgG subclasses in the TES ELISA was seen with 141 serum samples from patients with 10 other helminthic infections. However, IgG3 gave the best specificity (values: IgG, 73%; IgG1, 76%; IgG2, 71%; IgG3, 81%; IgG4, 71%). Thus, of the IgG subclass antibodies, IgG2 appeared best and employing this subclass can improve the serodiagnosis of human toxocariasis since it recognises carbohydrate epitopes of TES antigens.
Watthanakulpanich
Dorn
D
School of Biomolecular Sciences, Liverpool John Moores University, Byrom Street, Liverpool L3 3AF, UK.
Smith
Huw V
HV
Hobbs
Glyn
G
Whalley
Anthony J
AJ
Billington
David
D
D000818:Animals; D000888:Antibodies, Anti-Idiotypic; D000909:Antibodies, Helminth / Q000097:blood; D000947:Antigens, Helminth / Q000302:isolation & purification; D003429:Cross Reactions; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D006801:Humans; D007074:Immunoglobulin G; D012680:Sensitivity and Specificity; D012698:Serologic Tests / Q000379:methods; D017166:Toxocara canis / Q000737:chemistry* / Q000276:immunology*; D014120:Toxocariasis / Q000175:diagnosis*
D000888:Antibodies, Anti-Idiotypic; D000909:Antibodies, Helminth; D000947:Antigens, Helminth; D007074:Immunoglobulin G