Information on in vivo gene expression would provide insight into how C. albicans interacts with host cells during the transition from commensal colonization to an opportunistic pathogen in the immunocompromised host. However, in vivo transcription profiling of C. albicans during commensal colonization or candidemia is technically challenging [6] . Instead, several genome-wide transcriptional analyses of C. albicans responses to host cells have been performed using ex vivo and in vivo infection models. These include phagocytosis of C. albicans cells by neutrophils [7] and macrophages [8] , exposure to human blood, plasma, and blood cells [9, 10] , as well as invasion of perfused pig liver and reconstituted human epithelium [11, 12] . Genes that are associated with morphological changes, metabolic adaptation, and oxidative stress are the major responses of C. albicans to host cells identified in these studies. The changes in gene expression identified in these in vitro model systems possibly reflect tissue-or stage-specific expression during an infection in patients. Profiling of antibody responses during infection in patients offers an alternative approach that can overcome technical challenges of in vivo transcription profiling. An antibody-based approach has been used to identify C. albicans gene expression during thrush in individuals with HIV [13] .