We have developed a monoclonal antibody (MAb), C7, that reacts with the Als3p and enolase present in the Candida albicans cell wall and exerts three anti-Candida activities: candidacidal activity and inhibition of both adhesion and filamentation. To investigate the mode of action of MAb C7 on fungal viability, we examined changes in the genome-wide gene expression profile of C. albicans grown in the presence of a subinhibitory concentration of MAb C7 (12.5 g/ml) by using microarrays. A total of 49 genes were found to be differentially expressed upon treatment with MAb C7. Of these, 28 were found to be upregulated and 21 were found to be downregulated. The categories of upregulated genes with the largest number of variations were those involved in iron uptake or related to iron homeostasis (42.86%), while the energy-related group accounted for 38.10% of the downregulated genes (8/21). Results were validated by real-time PCR. Since these effects resembled those found under iron-limited conditions, the activity of MAb C7 on C. albicans mutants with deletions in key genes implicated in the three iron acquisition systems described in this yeast was also assessed. Only mutants lacking the TPK1 gene and, to a lesser extent, the TPK2 gene were less sensitive to the candidacidal effect of MAb C7. FeCl 3 or hemin at concentrations of >7.8 M reversed the candidacidal effect of MAb C7 on C. albicans in a concentration-dependent manner. The results presented in this study provide evidence that the candidacidal effect of MAb C7 is related to the blockage of the reductive iron uptake pathway of C. albicans.

Monoclonal antibody (MAb) C7 reacted with a >200-kDa component from the Candida albicans cell wall identified by matrix-assisted laser desorption ionization-time-of-flight mass spectrometry as Als3. It also bound the recombinant N terminus of Als3. Binding of MAb C7 to Als3 may explain the biological activities exerted by the MAb on C. albicans.

Background: The diagnosis of invasive candidiasis is difficult because there are no specific clinical manifestations of the disease and colonization and infection are difficult to distinguish. In the last decade, much effort has been made to develop reliable tests for rapid diagnosis of invasive candidiasis, but none of them have found widespread clinical use.

Immunization of mice with a stress mannoprotein of >200 kDa from the cell wall of Candida albicans led to the production of monoclonal antibody (Mab) C7. The immunogen is a major target of secretory IgA and its expression is regulated by different environmental conditions including temperature, pH, glucose concentration and ammonium sulphate in the culture medium. Mab C7 reacted with a peptide epitope present in the >200 kDa antigen as well as in a number of antigens from the blastoconidium and germ tube cell wall, including enolase. In addition to its reactivity with C. albicans, Mab C7 also reacted with antigens present in C. krusei, C, tropicalis, C. glabrata, C. dubliniensis and C. lusitaniae, as well as in Cryptococcus neoformans, Scedosporium prolificans and Aspergillus fumigatus. Mab C7 exhibited four important biological activities, namely inhibition of adhesion of C. albicans to a variety of surfaces, inhibition of germination of C. albicans, direct candidacidal activity and direct tumoricidal activity. In tumor cells, Mab C7 reacted with nucleoporin Nup88, a reactivity that can be utilized for diagnostic and prognostic purposes.

The use of DNA microarrays is becoming the method of choice for assaying gene expression, particularly as costs and complexity are being reduced as the technology becomes more widespread and better standardized. A DNA array is nothing but a collection of probes fixed on a solid support. The probes can be PCR products of ORFs or short intragenic oligonucleotides deposited or synthesized in situ by photolithographic methods. To date, sequencing projects for fungal genomes have yielded 10 complete genomes and 21 whole shotgun sequences, including Candida albicans strain SC5314. Sequencing of the C. albicans genome has led to the construction of whole-genome DNA microarrays for in vitro transcription profiling by several universities and companies. The use of microarray or DNA chip techniques for Candida research has started recently but the number of studies using this technology is increasing rapidly, in order to address important remaining questions about pathogenesis, cell biology, antifungal susceptibility, and diagnosis.