The thermotolerant Arabian killifish, Aphanius dispar , as a novel infection model for human fungal pathogens

Candida albicans : a fungal pathogen, can cause superficial and fatal infections in humans. An important virulence factor in C. albicans dissemination is the transformation from yeast to an invasive hyphal form, which is favoured at human body temperature. Zebrafish, a useful model for studying C. albicans infections, cannot survive at 37°C. Arabian killifish, Aphanius dispar , an emerging teleost model can tolerate temperatures up to 40 °C for up to 12 days (independent feeding time) allowing for longer analysis compared to zebrafish. This study introduces A. dispar as a thermo-relevant and a more accurate reporter of the virulence mechanisms relevant to C. albicans as a human pathogen. Using A. dispar , we tested virulence at human skin (30 °C), body temperature (37 °C) and a high fever condition (40°C). Infection by C. albicans at 37°C and 40°C significantly increased virulence, reduced survival of AKF embryos and formed invasive hyphal network compared to 30 °C. Two mutant strains of C. albicans. pmr1Δ (with aberrant cell surface glycans) exhibited reduced virulence at 37°C, whereas rsr1 Δ (lacking a cell polarity marker) showed less virulence at 30 °C. Additionally, anti-fungal treatment rescued AKF survival in a dose-dependent manner, indicating AKF’s potential for in vivo drug testing. Our data indicates the quantitative and qualitative importance of examining virulence traits at physiologically relevant temperatures and demonstrates an equivalence to findings for systemic infection derived in mouse models. The A. dispar embryo therefore provides an excellent in vivo model system for assessing virulence, drug-testing, and real-time imaging of host-pathogen interactions.