Pilot Study Comparing the In Vitro Response of Circulating Monocytes to Aspergillus fumigatus Swollen Conidia in Patients with Chronic Graft-Versus-Host Disease and Healthy Volunteers

Invasive fungal disease (IFD) is a recognised and potentially life-threatening complication of chronic graft-versus-host disease (cGVHD) and its treatment. Invasive aspergillosis (IA), most often due to the species Aspergillus fumigatus, is the leading IFD in this setting. IA can occur during the early weeks following allogeneic haematopoietic stem cell transplantation (HSCT) coinciding with profound neutropenia, but increasingly, cases of IA occur after engraftment, coinciding with the occurrence of cGVHD. Immunomodulatory treatments of cGVHD can impair innate immune responses to inhaled Aspergillus conidia, increasing the risk of developing IA. Here, in a pilot study, we present an analysis of the phenotypic characteristics (phagocytic efficiency, fungal killing, and cytokine release) of circulating monocytes derived from patients with cGVHD compared to healthy volunteers. We found that there was no statistically significant difference in their ability to phagocytose A. fumigatus conidia, and while there was a trend in their reduced ability to kill conidia, this was not significant when compared to the ability of volunteers’ monocytes to do so. Although we could not demonstrate in this small cohort of patients with cGVHD that monocytes may be a factor in the increased susceptibility to IA, further investigation of larger numbers of study subjects is warranted so that in vitro biomarkers may be developed for immune responses to Aspergillus in patients with cGVHD.