PubMed · 16111244
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Takeshi Mori, Konagi Matsumoto. 2005. [Immunologic tests: Cryptococcosis].. https://pubmed.ncbi.nlm.nih.gov/16111244/
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We developed a colorimetric microtiter plate polymerase chain reaction enzyme immunoassay (PCR-EIA) for the detection of Histoplasma capsulatum in urine. The specificity of the PCR assay was confirmed using H. capsulatum (positive control) and Blastomyces dermatitidis (negative control) isolates. The analytical sensitivity of the PCR assay was determined by testing urine samples spiked with freshly grown H. capsulatum organisms and was 2 yeasts per reaction in urine and 0.2 yeasts per reaction in urine sediment after centrifugation. Fifty-one urine specimens positive for H. capsulatum antigen and 25 urine specimens from healthy volunteers were tested blindly. Patient specimens also were cultured for H. capsulatum. The PCR assay was positive in 4 (7.8%) of 51 urine specimens containing antigen and negative in urine specimens from healthy volunteers. The positive PCR results occurred in 4 of 5 urine specimens that were positive by culture, and each exhibited high level of antigenuria (>20 U). Urine cultures were not positive in 24 urine specimens with an antigenuria of 1-19.9 U, but were positive in 5 of 27 urine specimens with antigenuria >20 U. Thus, positive PCR results in urine specimens correlate with positive culture results, but not with antigenuria. The low sensitivity of this PCR assay in urine limits its use in the diagnosis of disseminated histoplasmosis.
Genome dynamics that allow pathogens to escape host immune responses are fundamental to our understanding of host-pathogen interactions. Here we present the first population-based study of the process of concerted evolution in the repetitive domain of a protein-coding gene. This gene, SOWgp, encodes the immunodominant protein in the parasitic phase of the human pathogenic fungi Coccidioides immitis and C. posadasii. We sequenced the entire gene from strains representing the geographic ranges of the two Coccidioides species. By using phylogenetic and genetic distance analyses we discovered that the repetitive part of SOWgp evolves by concerted evolution, predominantly by the mechanism of unequal crossing over. We implemented a mathematical model originally developed for multigene families to estimate the rate of homogenization and recombination of the repetitive array, and the results indicate that the pattern of concerted evolution is a result of homogenization of repeat units proceeding at a rate close to the nucleotide point mutation rate. The release of the SOWgp molecules by the pathogen during proliferation may mislead the host: we speculate that the pathogen benefits from concerted evolution of repeated domains in SOWgp by an enhanced ability to misdirect the host's immune system.
The early diagnosis of mycoses is important for the institution of an effective antifungal therapy. Detection of antibodies against crude antigenic extracts is one of the standard techniques for the diagnosis of most mycoses. However, while these crude antigenic extracts are relatively easy to obtain, they usually show low reproducibility and are not very specific, since antibodies from patients with different mycoses may show cross-reactivity. The application of molecular biology techniques to the study of fungal antigens has allowed the production of recombinant antigens that may help to solve these problems. The purpose of this review is to discuss the use of recombinant fungal antigens in the diagnosis of mycoses.