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Sporotrichosis diagnosis involves a series of analyses, including culture and antibody detection in serum samples. Serologic methods may sometimes yield false-negative or false-positive results, leading to inaccurate diagnoses. This study assessed specific patient groups in which antibody detection of different isotypes and subclasses may lack sensitivity. An enzyme-linked immunosorbent assay (ELISA) with Sporothrix brasiliensis exoantigens was used to investigate IgM, IgG, IgG1, IgG2, IgG3, IgG4, IgA, IgA1 and IgA2 antibodies in human serum samples. Eighty serum samples from patients with different sporotrichosis clinical manifestations, including cutaneous forms with and without hypersensitivity manifestations, extracutaneous forms (bone, ocular, meningeal and pulmonary), disseminated cutaneous forms and disseminated forms in individuals living with HIV/AIDS, diabetics and alcoholics, were evaluated. The ELISA sensitivities in the detection of different antibodies ranged from 0.85 to 0.60 for the detection of IgG2 and IgG3, respectively. The antibodies with higher area under ROC curves were IgG2, IgG, IgA and IgA1. There were no significant differences in the immunological reactivity of the tested antibodies among different clinical forms of sporotrichosis. The data revealed a higher likelihood of a false-negative outcome in patients with lesions in the nasal mucosa regarding the detection of IgM and a lower likelihood in patients with lymphocutaneous sporotrichosis regarding the detection of IgG3. Patients with hypersensitivity manifestations had a 3.71 odds ratio to yield negative results in total IgG detection. In conclusion, we identified specific patient groups in which antibody detection may lack sensitivity, thus contributing to a better understanding of the diagnostic challenges associated with this condition., (© 2024 Wiley‐VCH GmbH. Published by John Wiley & Sons Ltd.)

This study was undertaken to examine the effects of immunization with Sporothrix schenckii and oral potassium iodide (KJ) administration on the chemiluminescence (CL) response of mouse polymorphonuclear leukocytes (PMNs) in experimental murine sporotrichosis. When N-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP) particles were used as foreign bodies to be phagocytosed, the time to the peak CL response of the PMNs in an immunized group was shortened in comparison with a non-immunized control group, and the CL intensity was found to be prolonged. Whereas administration of KJ resulted in a reduction of the CL intensity in non-immunized mice, in immunized mice it caused a rise in CL intensity. When the foreign bodies used as targets for phagocytosis were Sp. schenckii, changes similar to the above occurred, but CL production was reduced.