ABSTRACTCandida albicans IRS4encodes a protein that regulates phosphatidylinositol-(4,5)-bisphosphate, which was shown to contribute to hematogenously disseminated candidiasis (DC) after several days in the standard mouse model. Our objective was to more accurately define the temporal contributions ofIRS4to pathogenesis. During competition assaysin vitro, anirs4-null (Δirs4) mutant exhibited wild-type fitness. In DC experiments, mice were infected intravenously with the Δirs4mutant, strain CAI-12 (1 × 105CFU), or a mixture of the strains (0.5 × 105CFU each). In single-strain infections, quantitative PCR revealed reduced Δirs4mutant burdens within kidneys at days 1, 4, and 7 but not 6 h. In competitive infections, the Δirs4mutant was outcompeted by CAI-12 in each mouse at ≥6 h (competitive indices,P≤ 0.0001). At 4 and 7 days, the Δirs4mutant burdens during competitive infections were significantly lower than those during single-strain infections (P= 0.01 andP< 0.001, respectively), suggesting increased susceptibility to inflammatory responses. Phagocytic infiltration of kidneys in response to CAI-12 or competitive infections was significantly greater than that in response to Δirs4mutant infection at days 1 and 4 (P< 0.001), and the Δirs4mutant was more susceptible to phagocytosis and killing by human polymorphonuclear cells (P= 0.01 andP= 0.006, respectively) and mouse macrophagesin vitro(P= 0.04 andP= 0.01, respectively). Therefore,IRS4contributes to tissue invasion at early stages of DC and mediates resistance to phagocytosis as DC progresses. Microarray analysis revealed remarkably similar gene expression by the Δirs4mutant and reference strain CAI-12 within blood, suggesting thatIRS4is not significantly involved in the hematogenous stage of disease. A competitive DC model detects attenuated virulence that is not evident with the standard model.
Human monoclonal anti‑TLR4 antibody negatively regulates lipopolysaccharide‑induced inflammatory responses in mouse macrophages
