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The need for new options for the treatment of invasive candidiasis has fuelled the use of antibodies in combination with conventional antifungal therapy. After a long period of time in which antibodies were considered irrelevant in the resistance against invasive candidiasis, it was demonstrated that a number of antibodies or their engineered derivatives directed against Candida albicans cell-wall polysaccharides and glycopeptides, as well as against some protein epitopes, confer protection against invasive candidiasis. This has confirmed this approach as a new strategy for the prophylaxis of invasive candidiasis. Of particular interest is Mycograb®, a human recombinant monoclonal antibody that inhibits heat shock protein 90, and has been administrated in combination with lipid-associated amphotericin B to patients with invasive candidiasis, and the fungicidal anti-β-glucan antibodies induced by the glycoconjugate vaccine composed of a β-glucan polysaccharide conjugated with the diphtheria toxoid CRM 197. However, despite the promising data obtained in vitro and in animal models, at present there is very little clinical experience on the use of antibodies in Candida immunoprophylaxis.

Mice infected by Candida albicans and treated with monoclonal antibody C7 survived longer than saline-treated animals. A prozone-like effect was observed. The in vitro candidacidal activity of macrophages was strongly enhanced when C. albicans was opsonized by C7 and complete murine serum was present.

Antibodies are believed to play a role in the protection against Candida albicans infections by a number of mechanisms, including the inhibition of adhesion or germ tube formation, opsonization, neutralization of virulence-related enzymes, and direct candidacidal activity. Although some of these biological activities have been demonstrated individually in monoclonal antibodies (MAbs), it is not clear if all these anti- C. albicans activities can be displayed by a single antibody. In this report, we characterized a monoclonal antibody raised against the main target of salivary secretory immunoglobulin A in the cell wall of C. albicans , which exerts three anti- C. albicans activities: (i) inhibition of adherence to HEp-2 cells, (ii) inhibition of germination, and (iii) direct candidacidal activity. MAb C7 reacted with a proteinic epitope from a mannoprotein with a molecular mass of >200 kDa predominantly expressed on the C. albicans germ tube cell wall surface as well as with a number of antigens from Candida lusitaniae , Cryptococcus neoformans , Aspergillus fumigatus , and Scedosporium prolificans. MAb C7 caused a 31.1% inhibition in the adhesion of C. albicans to HEp-2 monolayers and a 55.3% inhibition in the adhesion of C. albicans to buccal epithelial cells, produced a 38.5% decrease in the filamentation of C. albicans , and exhibited a potent fungicidal effect against C. albicans , C. lusitaniae , Cryptococcus neoformans , A. fumigatus , and S. prolificans , showing reductions in fungal growth ranging from 34.2 to 88.7%. The fungicidal activity showed by MAb C7 seems to be related to that reported by antibodies mimicking the activity of a killer toxin produced by the yeast Pichia anomala , since one of these MAbs also reacted with the C. albicans mannoprotein with a molecular mass of >200 kDa. Results presented in this study support the concept of a family of microbicidal antibodies that could be useful in the treatment of a wide range of microbial infections when used alone or in combination with current antimicrobial agents.

The diagnosis of invasive candidiasis remains a clinical challenge. The detection by indirect immunofluorescence of Candida albicans germ-tube-specific antibodies (CAGTA), directed against germ-tube surface antigens, is a useful diagnostic tool that discriminates between colonization and invasion. However, the standardization of this technique is complicated by its reliance on subjective interpretation. In this study, the antigenic recognition pattern of CAGTA throughout experimental invasive candidiasis in a rabbit animal model was determined by means of 2D-PAGE, Western blotting, and tandem mass spectrometry (MS/MS). Seven proteins detected by CAGTA were identified as methionine synthase, inositol-3-phosphate synthase, enolase 1, alcohol dehydrogenase 1,3-phosphoglycerate kinase, 14-3-3 (Bmhl), and Egd2. To our knowledge, this is the first report of antibodies reacting with Bmhl and Egd2 proteins in an animal model of invasive candidiasis. Although all of the antigens were recognized by CAGTA in cell-wall dithiothreitol extracts of both germ tubes and blastospores of C. albicans, immunoelectron microscopy study revealed their differential location, as the antigens were exposed on the germ-tube cell-wall surface but hidden in the inner layers of the blastospore cell wall. These findings will contribute to developing more sensitive diagnostic methods that enable the earlier detection of invasive candidiasis.

Superficial candidiasis of the oral cavity, vagina and the skin are common mild infections though they may be recalcitrant, as in the case of recurrent vaginitis or denture stomatitis. However, in debilitated people with immune deficiencies, Candida can cause serious invasive infections with high mortality. Both types of patients could benefit from the development of vaccines and monoclonal or polyclonal antibodies of utility for a passive immunization, according to their immune status. Several antigens as mannans, β-glucans, various adhesins, heat shock protein 90 and acid secreted proteinases can be very useful for the vaccines development. There is a broad and sound experience with many of these antigens in animal models, mainly in rabbits and mice. However, only two vaccines, based on recombinant antigens (rAls3p-N and rSap2t) are currently being tested in clinical trials.

The phagocytic and candidacidal activities of the peritoneal cells of Candida albicans-infected mice were studied 20 days following experimental infection. Both activities were enhanced during infection. The production of nitric oxide (NO) by the peritoneal cells of infected mice was determined, and an increase in the nitrite concentration in supernatants of peritoneal cell cultures was detected. The period of NO production by the peritoneal cells coincided partially with the period of enhanced C. albicans killing. The inhibition of NO synthesis by N-monomethyl-L-arginine was concomitant with inhibition of candidacidal activity. We conclude that NO synthesis is the primary candidacidal mechanism of the murine peritoneal cells activated by C. albicans infection.

The use of a two-dimensional polyacrylamide gel electrophoresis joined with Western blotting allowed us to investigate the reactivities of antibodies present in sera from mice and humans to antigens of Candida albicans blastoconidia. The analysis of the antibody response in the two models studied and the comparison between the antibody response in infected and non-infected individuals showed that the infection by C. albicans produces changes in the antibody response which may be of relevance in the serodiagnosis of invasive candidiasis. These changes include the induction of antibodies against new antigens, the disappearance of antibodies against a group of antigens and variations in the reactivity of antibodies directed to a different group of antigens. The technique used resolved the isoforms of several antigens including enolase. It is concluded that the antibody response in humans and mice with candidiasis is not homogeneously directed to all the isoforms of an antigen.

The effect of chitin, a polysaccharide of the cell wall of Candida albicans, on both the survival of C. albicans infected mice and the activity of the murine peritoneal macrophages has been studied. Pretreatment of mice with 30 mg kg(-1) C. albicans chitin enhanced the survival of the infected animals. The protective effect was concomitant with an enhancement of both phagocytic and candidacidal activities of the peritoneal macrophages. Chitin by itself did not induce the nitric oxide (NO) synthase in the macrophages, which remained at a level similar to that shown by the macrophages from untreated animals. The administration of 10 mg kg(-1) C. albicans chitin diminished the long term survival of the infected animals. This effect was coincident with a lower candidacidal activity and NO production by the macrophages of the chitin treated and infected animals, compared to the untreated infected animals.

Analysis of mitochondrial DNA restriction patterns was used to study the introduction of a selected strain of Saccharomyces cerevisiae for fermentation of non-sterile musts of La Rioja (Spain). All of the isolates from the inoculated musts showed the restriction pattern of the selected strain. The same technique was used to study the spontaneous fermentation of musts, showing that a few strains were responsible for the fermentations. One of the strains identified from the spontaneous fermentations had been identified in a previous vintage.