Cell surface proteins were selected from the Candida Genome Database (CGD) using keywords such as ''cell surface'', ''plasma membrane'', and ''cell wall''. The CGD annotation of cell surface proteins is based on published experiments [32, [62] [63] [64] [65] [66] , functionbased prediction of cellular localization, and sequence prediction. Known antigenic proteins are also included as controls (Bgl2, Eno1, Pgk1, Gap1, Cdc19, Tkl1, Hsp90, and members of the Hsp70 family) [15, 17] . Coding regions of the genes were PCR amplified from the clinical isolate SC5314 of C. albicans with primers listed in Table S2 , and cloned into a pXT7 expression vector with a HA-tag at the N-terminus and His-tag at the Cterminus by homologous recombination in E. coli as described [67] . Protein expression was carried out using an E. coli based cell- Figure 3 . Discrimination of convalescent candidemia patients from the study population. (A) Two-way hierarchical cluster analyses of the 33 differentially expressed anti-C. albicans cell surface antibodies from early/mid convalescent candidemia sera. The heatmap is organized with antigens, in rows, and acute candidemia patients (n = 18), early and mid convalescent patients (n = 10) and negative control groups (hospital patients (n = 12) and healthy individuals (n = 50)) in columns. The colorized scale ranks the antigens with red being the strongest, bright green the weakest, and black in between. (B, C & D) Principal component analyses of serum anti-C. albicans cell surface IgG antibody expression profiles that discriminate between convalescent candidemia patients and each negative control group (hospital patients and health individuals). Each circle denotes the anti-C. albicans cell surface antibody profile of asingle serum specimen. Samples are color coded as the following acute candidemia patients (red), convalescent candidemia patients (brown), healthy individuals (green), and hospital patients (blue). (E) The graph shows the ROC curves generated using different sets of serodiagnostic antigens. doi:10.1371/journal.ppat.1000827.g003 free in vitro transcription/translation system (RTS 100 E. coli HY kit, Roche). The protein microarray was made by printing the peptides onto nitrocellulose-coated FAST glass slides (Schleicher & Schuell) using the OmniGrid 100 (GeneMachines) in the UCI Microarray Facility. Each peptide was printed in duplicate and showed homogenous spot morphology as well as low background. Internal controls consisting of buffer alone and a reaction mixture with no DNA were also printed onto the FAST slides. After the addition of the plasma samples the microarray was incubated with a biotin-conjugated donkey anti-human IgG Fc c fragment specific secondary antibody (Jackson Immunoresearch). The secondary antibody was then removed and the microarray was incubated with Streptavidin: SureLight H P-3 (Columbia Biosciences). Details concerning microarray construction and controls, antibody profiling, data normalization, as well as the reproducibility and validity of the microarray are given in the Text S1.