Our previous studies demonstrated that the fbp1Δ mutant elicited superior protective Th1 host immunity in the lungs and that the enhanced immunogenicity of heat-killed fbp1Δ (HK-fbp1) yeast cells can be harnessed to confer protection against a subsequent infection with the virulent parental strain in immunocompetent or CD4+ T cell-deficient hosts (20, 21). This evidence concerns the gene FBP1 and infection.