An immunohistochemical method that differentiates Cryptococcus neoformans varieties and serotypes in formalin-fixed...

Area of Science:

• Mycology
• Immunology
• Veterinary Pathology

Background:

• Cryptococcosis is a fungal infection caused by Cryptococcus neoformans.
• Accurate identification of C. neoformans varieties is crucial for epidemiological studies and patient management.
• Current methods for variety determination can be limited, especially with archival tissue samples.

Purpose of the Study:

• To develop and validate an immunohistochemical (IHC) method for determining the variety of Cryptococcus neoformans in formalin-fixed paraffin-embedded tissues.
• To compare the efficacy of the IHC method with conventional methods like L-Canavanine glycine bromothymol blue (CGB) agar and the 'Crypto-Check' kit.

Main Methods:

• Development of an IHC method using specific monoclonal antibodies (mAbs 471, 302, CRND8).
• Validation using veterinary patient samples with available formalin-fixed lesions and cultured isolates.
• Comparison with CGB agar for variety determination and Crypto-Check kit for serotyping.

Main Results:

• The IHC method accurately predicted C. neoformans variety in all tested tissue specimens.
• IHC results for variety determination agreed with CGB agar in 30 out of 31 specimens.
• Discrepancies between IHC and CGB agar/Crypto-Check kit were observed, with other analyses supporting the IHC findings for C. neoformans var. gattii and C. neoformans var. neoformans.

Conclusions:

• The developed IHC method is a reliable and accurate tool for identifying C. neoformans varieties in tissue samples.
• This IHC technique offers significant advantages for cryptococcosis research, particularly in veterinary settings with limited mycological data.
• The method's versatility allows for future expansion with the development of new monoclonal antibodies.