Identification of immunogenic proteins of Candida parapsilosis by serological proteome analysis

AbstractAims: Systemic candidiasis is the leading fungal bloodstream infection, and itsincidence has been on the rise. Recently, Candida parapsilosis has emerged asan increasingly prevalent fungal pathogen, but little is known about itsantigenic profile. Hence, the current work was performed to discoverimmunogenic proteins of C. parapsilosis using serological proteome analysis.Methods and Results: Cell wall proteins extracted from C. parapsilosis wereresolved by two-dimensional electrophoresis followed by immunoblotting usingantisera from experimentally infected mice. Mass spectrometry analysis of the32 immunoreactive protein spots resulted in the identification of 12 distinctproteins. Among them, 11 proteins were known antigens of Candida albicans,whereas Idh2p was identified for the first time as an immunogenic protein ofCandida species. Recombinant Idh2p was expressed in Escherichia coli, and itsantigenicity was verified by immunoblot analysis.Conclusions: An immunoproteomic approach was successfully applied toidentify immunogenic proteins of C. parapsilosis, with Idh2p as a novelcandidate antigen. The identified antigens may serve as potential biomarkersfor development of diagnostic assay and/or vaccine for C. parapsilosis.Significance and Impact of the Study: This work represents the firstimmunoproteomic analysis of C. parapsilosis, which provides new insights intohost–pathogen interactions and pathogenesis of C. parapsilosis. The immunogenicproteinscouldbe studied as biomarker candidates forC. parapsilosis.IntroductionCandida species is a member of normal human microfl-ora that exists in healthy individuals without causing anydisease. However, it is also an opportunistic fungal path-ogen that can cause candidiasis, affecting mainly peoplewith debilitated immune system. Candida spp. is themajor human fungal pathogen and was ranked as thefourth organism causing nosocomial bloodstream infec-tions in the United States (Wisplinghoff et al. 2004).Among all types of candidiasis, the systemic form is offoremost clinical importance as it is associated with highmortality and morbidity rate (Ortega et al. 2011). Theincidence of systemic candidiasis has increased markedlyover the years with Candida albicans as the predominantspecies isolated. However, in recent years, there is achanging trend in the epidemiology of Candida infectionsworldwide (Pfaller and Diekema 2007). Of importantnote is the significant increase in the prevalence ofCandida parapsilosis in several geographical locationsacross the globe (Forrest et al. 2008; Miceli et al. 2011).Likewise, the shift towards C. parapsilosis was alsoobserved in Malaysia (Ng et al. 2001; Rahman et al.2008; Siti Umairah et al. 2012).