Effects of histoplasmin M antigen chemical and enzymatic deglycosylation on cross-reactivity in the enzyme-linked immunoelectrotransfer blot method.
The enzyme-linked immunoelectrotransfer blot (EITB) method was evaluated as a suitable method for detecting antibodies against M antigen of Histoplasma capsulatum by use of both glycosylated and deglycosylated M protein of histoplasmin (HMIN). Sera from patients with histoplasmosis, paracoccidioidomycosis, blastomycosis, coccidioidomycosis, and aspergillosis were tested by the EITB with glycosylated M protein of HMIN. This assay demonstrated 100% sensitivity with histoplasmosis serum samples, all of which reacted with the 94-kDa glycoprotein (M antigen). Although the EITB is highly sensitive, it is not specific for histoplasmosis when glycosylated M protein is used as an antigen. A total of 81% of paracoccidioidomycosis, 25% of blastomycosis, 33% of coccidioidomycosis, 73% of aspergillosis, and 16% of tuberculosis serum samples cross-reacted with M protein of HMIN and yielded patterns indistinguishable from those obtained with histoplasmosis serum samples. The EITB reactions with both untreated M antigen and M antigen altered by periodate oxidation or by deglycosylation with endoglycosidases were compared. Cross-reactions with heterologous sera in the EITB could be attributed to periodate-sensitive carbohydrate epitopes, as reflected by the increase in the test specificity from 46.1 to 91.2% after periodate treatment of M protein. The EITB for the detection of antibodies to M antigen is a potential diagnostic test for histoplasmosis, provided that periodate-treated M protein is used as an antigen.
Zancopé-Oliveira
R M
RM
Laboratório de Micologia Médica, Hospital Evandro Chagas, Fundaçã Oswaldo Cruz, Rio de Janeiro, Brazil.
Bragg
S L
SL
Reiss
E
E
Wanke
B
B
Peralta
J M
JM
D000918:Antibody Specificity; D003429:Cross Reactions; D000939:Epitopes / Q000276:immunology; D006031:Glycosylation; D006658:Histoplasma / Q000201:enzymology / Q000276:immunology*; D006659:Histoplasmin / Q000276:immunology* / Q000378:metabolism; D006660:Histoplasmosis / Q000175:diagnosis* / Q000276:immunology; D006801:Humans; D015151:Immunoblotting; D007124:Immunoenzyme Techniques; D008934:Mitogens; D010084:Oxidation-Reduction; D010504:Periodic Acid; D012698:Serologic Tests
D000939:Epitopes; D008934:Mitogens; D010504:Periodic Acid; D006659:Histoplasmin; C009288:metaperiodate