Author:
S Wurster*, ND Albert, U Bharadwaj, MM Kasembeli, DP Kontoyiannis
Author address:
Infectious Diseases, Infection Control and Employee Health, The University of Texas MD Anderson Cancer Center, Houston, USA
Full conference title:
10th Advances Against Aspergillosis and Mucormycosis
Date: 2 February 2022
Abstract:
Purpose:
Anecdotal clinical reports suggested a potential 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/PD-L1 pathway blockade in immunosuppressed mice with invasive pulmonary mucormycosis (IPM).
Methods:
8-week-old BALB/c mice were immunosuppressed with cyclophosphamide (150 mg/kg on days -4 and -1, 100 mg/kg on day +3) and cortisone acetate (300 mg/kg on day -1) and infected intranasally with 50,000 Rhizopus arrhizus spores (clinical isolate Ra-749, day 0). Mice then received intraperitoneal injections (4 × 250 µg/kg every other day) of anti-PD-1, anti-PD-L1, or the corresponding isotype antibodies. Survival was monitored for 7 days post-infection. Infection severity was scored using the murine sepsis score (MSS, 0 = healthy to 3 = moribund, 4 = dead). Pulmonary fungal burden was quantified with an 18S qPCR assay on day +7 or upon death. Exhaustion marker expression on splenic T-cells, NK-cells, and macrophages was analyzed by flow cytometry (day +7). Cytokine and chemokine concentrations in lung tissue and serum were determined using a 19-plex magnetic Luminex assay (days +4 and +7). 34-36 mice per treatment were assessed in 3 independent experiments. Immunological end points were based on 5-6 mice per assay and time point.
Results:
Mice with IPM receiving either of the non-targeting isotype antibodies developed severe infection (median day-7 MSS, 3.0-4.0) and had a 7-day mortality of 46-50%. Blockade of PD-1 modestly improved infection severity (median MSS = 2.0, p < 0.01), 7-day mortality (24%, p < 0.01), and fungal burden (5.6k versus 40.7k spore equivalents per lung, p = 0.09). The PD-L1 inhibitor provided a stronger and more consistent therapeutic benefit, significantly improving morbidity (median MSS = 1.0, p < 0.001), survival (10% 7-day mortality, p < 0.001), and fungal burden (3.6k versus 27.2k spore equivalents, p < 0.001). Both ICI treatments reduced T-cellular exhaustion; however, macrophages of ICI-treated mice with IPM showed compensatory upregulation of other checkpoint molecules, such as Tim-3. Anti-PD-1 elicited stronger pulmonary release of inflammatory cytokines and chemokines (e.g., GM-CSF, M-CSF, CXCL2, CCL7) than anti-PD-L1, but also induced cytokines associated with potentially unfavorable type 2 T-helper-cell (IL-5, IL-13) and regulatory T-cell (IL-10) responses. Although no apparent signs of hyperinflammatory toxicity were observed, mice with IPM receiving ICIs, especially anti-PD-1, had elevated serum levels of IL-6, a cytokine linked to ICI toxicities.
Conclusion:
Blockade of the PD-1/PD-L1 pathway improved infection outcomes in immunosuppressed mice with IPM, 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 better define the “sweet spot” between ICI-induced augmentation of antifungal immunity and potential immunotoxicities. Moreover, development of more pathophysiologically representative infection models (e.g., murine leukemia models) would be warranted in order to dissect the nuanced effects of ICIs and other immuno-oncological agents on the course and immunopathology of opportunistic mold infections.
Abstract Number: 77
Conference Year: 2022
Link to conference website: https://aaam2022.org/
URL Conference abstract: