Caspofungin enhances antifungal immunity in human blood through transcriptional reprogramming

Candida albicans is a leading cause of invasive candidiasis, a life-threatening infection with high mortality despite antifungal therapy. Echinocandins are first-line agents due to their fungicidal activity and low toxicity profile. Beyond direct killing, they may also modulate host immunity, e.g. through fungal cell wall remodeling. However, the systemic impact of echinocandins on human immune cells remains incompletely understood, particularly in the context of drug resistance. Using an ex vivo human whole-blood infection model, we assessed the effects of caspofungin during infection with echinocandin-susceptible (ECH^S/FKS^wt) and echinocandin-resistant (ECH^R/FKS^mut) C. albicans strains. Infection alone triggered a strong and conserved transcriptional immune program enriched for innate recognition and inflammatory pathways. Caspofungin treatment during infection with the susceptible strain selectively amplified these responses, engaging a sequential cascade of host defenses that linked pathogen recognition with innate effector functions and adaptive polarisation. In contrast, caspofungin induced only minimal transcriptional changes in resistant strain infections or in uninfected blood. These findings demonstrate that caspofungin efficacy arises not only from its fungicidal activity but also from amplification of host immunity, an effect primarily dependent on fungal susceptibility. This dual mode of action highlights a previously underappreciated role of echinocandins in shaping antifungal immunity and provides new mechanistic insight into drug-host-pathogen interactions during systemic candidiasis.