Saccharomyces as a vaccine against systemic aspergillosis: 'the friend of man' a friend again?

The mortality of clinical Aspergillus infections necessitates consideration of the utility of a vaccine. We have found that Saccharomyces species can act as a protective vaccine against a lethal systemic Aspergillus infection, and describe experiments optimizing a subcutaneous regimen with killed yeast. Three injections of 2.5 mg given a week apart, 2 weeks prior to challenge, consistently, significantly, provided survival protection and reduction of infection in organs in survivors. The protection was independent of the strain of Saccharomyces, and possibly even the species, and could be demonstrated in several inbred (including C'-deficient) and outbred mouse strains. The protective moiety(ies) appeared to reside in the cell wall and was resistant to 100 °C, but not to protease or formalin. Alum potentiated the protection. The protection was comparable or superior to that of several Aspergillus-specific preparations described in the literature. Other studies have indicated that heat-killed Saccharomyces can protect against infection with at least three other fungal genera, raising the possibility of development of a panfungal vaccine, and such a vehicle has been studied in clinical trials, without dose-limiting toxicity.