Use of mycelial-phase Sporothrix schenckii exoantigens in an enzyme-linked immunosorbent assay for diagnosis of sporotrichosis by antibody detection

Abstract

An enzyme-linked immunosorbent assay (ELISA) was developed for specific antibody detection in serum specimens of patients with sporotrichosis. The assay was made with mycelial-phase Sporothrix schenckii exoantigens and was tested against 90 sera from patients with different clinical forms of sporotrichosis. Potential cross-reactions were analyzed with 72 heterologous sera from patients with paracoccidioidomycosis, cryptococcosis, aspergillosis, histoplasmosis, tuberculosis, and American tegumentary leishmaniasis, as well as 76 sera from healthy controls. We found a sensitivity of 97% and a specificity of 89% in this assay. Some cross-reactions were seen, as observed in other immunoassays for the diagnosis of sporotrichosis. The ELISA appears to be especially useful for cutaneous forms of disease, since these are not promptly diagnosed with available immunoprecipitation or agglutination techniques. These results suggest that the ELISA using mycelial-phase S. schenckii exoantigens is a very sensitive diagnostic tool for the serodiagnosis of sporotrichosis and can be used in conjunction with conventional methods of diagnosis, particularly in cases where cross-reactions or false-positive results are experienced with the serodiagnosis.

FIG. 1.

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis profile of the mycelial-phase S. schenckii 23508 exoantigens. MW, standard molecular mass; Ag, antigen. The molecular masses (in kDa) of the five protein bands detected in the silver stain are indicated on the right.

FIG. 2.

Detection by ELISA of IgG responses to S. schenckii exoantigens in sera from sporotrichosis patients, from patients with other proven infectious diseases, and from healthy controls. The dashed horizontal line shows the cutoff point. Sp, sporotrichosis; PCM, paracoccidioidomycosis; Cr, cryptococcosis; Asp, aspergillosis; Hp, histoplasmosis; Tb, tuberculosis; Leish, leishmaniasis; NHS, normal healthy sera (controls).

FIG. 3.

ROC curve of the described ELISA. The area under the curve is 0.9767 ± 0.0085.

FIG. 4.

IgG antibodies responses from patients with different clinical forms of sporotrichosis by ELISA. The dashed horizontal line shows the cutoff point. FC, fixed cutaneous sporotrichosis; LC, lymphocutaneous sporotrichosis; CD, cutaneous disseminated sporotrichosis; Dis, disseminated sporotrichosis; EC, extracutaneous sporotrichosis.

FIG. 5.

Distribution and reproducibility of ELISA results in two distinct experiments. Symbols: •, homologous sera; ▾, heterologous sera; ▪, healthy control sera. The correlation coeficient (r²) between these two experiments was 0.9608.