Diagnostic Potential of a Recombinant Candida albicans Hyr1 Protein

Invasive candidiasis (IC) is a life-threatening fungal infection caused by Candida species. Current diagnostic methods are based on blood culture of the fungus, a technique with limited sensitivity and slow turnaround times. To address these limitations, novel diagnostic strategies are under investigation. This study evaluates the diagnostic potential of the Candida albicans germ tube protein Hyr1 and a subterminal Hyr1 fragment (D22b), both produced in an eukaryotic expression system, for the diagnosis of IC; for that purpose, recombinant Hyr1 and D22b were expressed in Pichia pastoris and tested by ELISA using sera from 176 patients at risk of invasive fungal infections. The diagnostic performance of these antigens was determined and compared with other biomarkers (CAGTA and β-D-glucan). Interestingly, the recombinant proteins exhibited higher apparent molecular weights than predicted, suggesting the presence of post-translational modifications. Serological detection of antibodies against the recombinant Hyr1 and D22b fragment successfully distinguished patients with IC caused by the most commonly isolated Candida species, achieving sensitivities greater than 70% and specificities above 80%. These findings highlight the potential of the serological detection of antibodies to Hyr1 and D22b as a promising diagnostic approach that overcomes the drawbacks of CAGTA detection and could serve as a valuable complement to blood culture, supporting earlier diagnosis and guiding timely treatment decisions in IC. Furthermore, comparing results obtained with antigens produced in eukaryotic and prokaryotic systems, results suggest that accurate protein folding and post-translational processing influence the success of the diagnostic technique.