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Updated: Sep 27, 2026
Antigen-Capture Enzyme-Linked Immunosorbent Assay for Specific Detection of Mycoplasma pneumoniae
Published on: February 24, 2023
PCR assay for identification of histoplasma capsulatum based on the nucleotide sequence of the M antigen
Herbert Leonel de Matos Guedes1, Allan Jefferson Guimarães, Mauro de Medeiros Muniz
1Instituto de Pesquisa Clínica Evandro Chagas, FIOCRUZ, Rio de Janeiro, Brazil.
Abstract:
The major diagnostic antigens of Histoplasma capsulatum var. capsulatum are the H and M antigens, pluripotent glycoproteins that elicit both humoral and T-cell-mediated immune responses. The gene encoding the M antigen has previously been sequenced, and its sequence has significant overall homology to those of the genes for fungal catalases. Regions of the M-antigen gene with little or no homology were used to design four oligonucleotide sequences for application in the PCR detection and identification of H. capsulatum var. capsulatum. The PCR correctly identified the 31 H. capsulatum var. capsulatum strains isolated from human, animal, and soil specimens and 1 H. capsulatum var. duboisii isolate. PCR products of 111 and 279 bp were amplified with primers Msp1F-Msp1R and Msp2F-Msp2R, respectively. No amplification product was obtained from DNA extracted from an H. capsulatum var. farciminosum isolate. The specificity of the PCR with the M-antigen-derived primers was confirmed by the total absence of amplification products when genomic DNA from Paracoccidioides brasiliensis, Candida spp., Sporothrix schenckii, Cryptococcus neoformans, Blastomyces dermatitidis, Coccidioides immitis, Aspergillus niger, and Aspergillus fumigatus were applied in the reaction. This rapid, sensitive, and specific assay provides a way to identify typical and atypical isolates of H. capsulatum var. capsulatum.
Insights
A new PCR assay effectively identifies Histoplasma capsulatum var. capsulatum using M-antigen gene sequences. This method accurately detects the fungus in various specimens, offering a rapid diagnostic tool.
Area of Science:
- Mycology
- Molecular Biology
- Infectious Diseases
Background:
- Histoplasma capsulatum var. capsulatum is diagnosed using H and M antigens.
- The M-antigen gene shares homology with fungal catalases.
- Specific gene regions were targeted for diagnostic assay development.
Purpose of the Study:
- To develop a Polymerase Chain Reaction (PCR) assay for detecting Histoplasma capsulatum var. capsulatum.
- To utilize unique regions of the M-antigen gene for primer design.
- To establish a rapid, sensitive, and specific identification method for H. capsulatum var. capsulatum.
Main Methods:
- Oligonucleotide primers were designed based on non-homologous regions of the M-antigen gene.
- PCR was performed on DNA from various Histoplasma isolates and other fungal species.
- Amplification products were analyzed for size and specificity.
Main Results:
- The PCR assay correctly identified 31 strains of H. capsulatum var. capsulatum and one H. capsulatum var. duboisii isolate.
- Specific PCR products of 111 bp and 279 bp were observed with primer pairs Msp1F-Msp1R and Msp2F-Msp2R.
- No amplification occurred with H. capsulatum var. farciminosum or DNA from other fungal pathogens, confirming assay specificity.
Conclusions:
- The developed PCR assay is a rapid, sensitive, and specific method for identifying Histoplasma capsulatum var. capsulatum.
- This assay can differentiate between typical and atypical isolates of H. capsulatum var. capsulatum.
- The M-antigen gene provides a reliable target for molecular diagnostics of histoplasmosis.
