DataSheet_1_Blockade of the PD-1/PD-L1 Immune Checkpoint Pathway Improves Infection Outcomes and Enhances Fungicidal Host Defense in a Murine Model of Invasive Pulmonary Mucormycosis.docx

Anecdotal clinical reports suggested a benefit of adjunct immune checkpoint inhibitors (ICIs) to treat invasive mucormycosis. However, proof-of-concept data in animal models and mechanistic insights into the effects of ICIs on host defense against Mucorales are lacking. Therefore, we studied the effects of PD-1 and PD-L1 inhibitors (4 doses of 250 µg/kg) on outcomes and immunopathology of invasive pulmonary mucormycosis (IPM) in cyclophosphamide- and cortisone acetate-immunosuppressed mice. Rhizopus arrhizus-infected mice receiving either of the ICI treatments had significantly improved survival, less morbidity, and lower fungal burden compared to isotype-treated infected mice. While early improvement of morbidity/mortality was comparable between the ICI treatments, anti-PD-L1 provided more consistent sustained protection through day 7 post-infection than anti-PD-1. Both ICIs enhanced the fungicidal activity of ex-vivo splenocytes and effectively counteracted T-cell exhaustion; however, macrophages of ICI-treated mice showed compensatory upregulation of other checkpoint markers. Anti-PD-1 elicited stronger pulmonary release of proinflammatory cytokines and chemokines than anti-PD-L1, but also induced cytokines associated with potentially unfavorable type 2 T-helper-cell and regulatory T-cell responses. Although no signs of hyperinflammatory toxicity were observed, mice with IPM receiving ICIs, particularly anti-PD-1, had elevated serum levels of IL-6, a cytokine linked to ICI toxicities. Altogether, inhibition of the PD-1/PD-L1 pathway improved clinical outcomes of IPM in immunosuppressed mice, even without concomitant antifungals. PD-L1 inhibition yielded more favorable immune responses and more consistent protection from IPM-associated morbidity and mortality than PD-1 blockade. Future dose-effect studies are needed to define the “sweet spot” between ICI-induced augmentation of antifungal immunity and potential immunotoxicities.

轶事性的临床报告提示，辅助性免疫检查点抑制剂（ICIs）在治疗侵袭性毛霉菌病中可能具有益处。然而，动物模型中的概念验证数据和免疫检查点抑制剂对宿主防御毛霉菌科微生物的机制见解尚不足。因此，本研究旨在探讨PD-1和PD-L1抑制剂（250 µg/kg的4个剂量）对免疫抑制的环磷酰胺和醋酸可的松免疫抑制小鼠侵袭性肺毛霉菌病（IPM）的预后和免疫病理学的影响。接受ICI治疗的接菌毛霉属Rhizopus arrhizus感染小鼠与接受同型治疗的感染小鼠相比，生存率显著提高，发病率降低，真菌负荷减少。尽管ICI治疗在早期对发病率/死亡率改善方面相当，但抗PD-L1在感染后第7天提供的持续保护作用更为一致。两种ICIs均增强了体外脾细胞的杀菌活性，并有效对抗T细胞耗竭；然而，ICI治疗小鼠的巨噬细胞表现出补偿性上调其他检查点标记物。抗PD-1比抗PD-L1引起更强的肺释放促炎细胞因子和趋化因子，但同时也诱发了与潜在不利的Th2辅助细胞和调节性T细胞反应相关的细胞因子。尽管未观察到超炎症毒性迹象，但接受ICIs治疗，尤其是抗PD-1治疗的IPM小鼠血清中IL-6水平升高，IL-6是一种与ICIs毒性相关的细胞因子。总之，PD-1/PD-L1通路抑制改善了免疫抑制小鼠的IPM临床预后，即使没有伴随的抗菌药物。PD-L1抑制比PD-1阻断产生了更有利的免疫反应和更一致的从IPM相关发病率及死亡率中的保护作用。未来需要进行剂量效应研究，以确定ICI诱导的抗真菌免疫增强和潜在免疫毒性之间的“最佳平衡点”。