Detection of antibody to Purpureocillium lilacinum by immunofluorescent assay and flow cytometry in serum of infected C57BL/6 mice

• Seroreactivity of antibodies can be detected using both IFA and FCM.
• Both IFA and FCM indicated that the IgG antibody response appeared early upon infection.
• It is the first time where FCM was used to detect IgG anti-P. lilacinum conidia.
• The immunosupression does not seem to interfere with the humoral immune response.

Purpureocillium lilacinum is an emerging pathogenic fungus that can cause different clinical manifestations ranging from cutaneous and sub-cutaneous infections to severe oculomycosis. In this study, using both conventional indirect immunofluorescence and non-conventional flow cytometry approaches, IgG antibodies were readily detected in both C57BL/6 immunocompetent and immunosuppressed mice after i.v. infection with P. lilacinum. The humoral immune response was specific, since virtually no antibodies were detected in the serum of control mice. Flow cytometry assays also showed both quantitative and qualitative differences in total IgG and its isotypes in sera of immunocompetent and immunosupressed infected mice. Although a good starting point, it is clear that the effectiveness of serological assays for P. lilacinum hyalohyphomycosis identification in clinical studies still requires further standardization. Upon further validation in humans, these techniques have the potential to be suitable to detect P. lilacinum infection in patients, thereby avoiding current laborious and time-consuming culture techniques.