Serological response and diagnostic value of recombinant candida cell wall protein enolase, phosphoglycerate kinase, and β-glucosidase

Abstract

There are no specific signs and symtoms for invasive candidiasis (IC), which makes its diagnosis a challenge. Efforts have been made for decades to establish serological assays for rapid diagnosis of IC, but none of them have found widespread clinical use. Using a systemic candiasis murine model, serological response to recombinant proteins of enolase (rEno1), phosphoglycerate kinase (rPgk1), and β-glucosidase (rBgl2) were evaluated and rEno1 was found to possess the strongest immunoreactivity, followed by rPgk1 and rBgl2. Likewise, IgG antibody titers to rEno1, rPgk1, and rBgl2 in the positive sera of proven IC patients were determined by ELISA. Results show anti-rEno1 antibody possesses the highest titer, followed by rPgk1 and rBgl2. Antibodies against rEno1, rPgk1, and rBgl2 were detected by ELISA tests in a group of 52 proven IC patients or 50 healthy subjects, The sensitivity, specificity, positive and negative predictive values were 88.5, 90.0, 90.2, and 88.2% for anti-rEno1 detection, 86.5, 92.0, 91.8, and 86.8% for anti-rPgk1 detection, and 80.8, 90.0, 89.4, and 81.8% for anti-rBgl2 detection, respectively. The data clearly demonstrate that the recombinant proteins of Eno1, Pgk1, and Bgl2 are promising candidates for IC serodiagnosis. There's great possibility that the recombinant Eno1 will be more applicable in serodiagnosis and vaccine research on account of its strong serological response.

Development of a Lateral Flow Immunoassay for the Rapid Diagnosis of Invasive Candidiasis

“…For the ELISA test, the sensitivity, specificity, PPV and NPV were 86.8, 90.0, 86.8, and 90.0%, respectively. This result was similar to those seen in previous studies (Clancy et al, 2008 ; He et al, 2015 ). For the LFIA test, the corresponding values were 71.1, 96.0, 93.1, and 81.4%.…”

“…Several studies have indicated that C. albicans enolase, a cell wall associated protein, is a promising candidate molecule for diagnosing IC, even in patients with neutropenia and immune defects (Laín et al, 2007 ; Clancy et al, 2008 ; Li et al, 2013 ). According to our previous work (He et al, 2015 ), enolase proved to be an immuno-dominant protein compared to other cell wall associated proteins, which makes enolase more applicable to serodiagnosis research. Using the rEno as the test capture reagent, we detect the antibody against enolase in the sera of proven IC patients and control subjects.…”

“…Recombinant enolase protein was generated and purified as described in our previous work (He et al, 2015 ).…”

“…ELISA was performed as described in our previous work to detect the anti Eno IgG level in the sera of subjects enrolled in this research study (He et al, 2015 ). Briefly, rEno was adjusted to the concentration of 500 ng/mL in the bicarbonate buffer (pH9.6) and used to coat ELISA plates.…”

“…In this study, using recombinant Eno (rEno) of C. albicans (He et al, 2015 ), we developed a lateral flow immunoassay (LFIA) for the detecting human IgG antibodies against Eno. The test is rapid, easy to use and suitable for the serological diagnosis and surveillance of IC.…”