Immunotherapeutic strategies against mucormycosis in haematopoietic stem cell transplantation

Developments in identifying and managing mucormycosis in hematologic cancer patients

INTRODUCTION

Mucormycoses represent a rare but very aggressive class of mold infections occurring in patients with hematological malignancies (HMs). In the past, patients at high risk of invasive mucomycosis (IM) were those affected by acute myeloid leukemia but over the last ten years the prophylaxis with a very effective mold-active drug, such as posaconazole, has completely modified the epidemiology. In fact, IM is now observed more frequently in patients with lymphoproliferative disorders who do not receive antifungal prophylaxis.

AREAS COVERED

The attention was focused on the epidemiology, diagnosis, prophylaxis and treatment of IM in HMs. Authors excluded pediatric patients considering the different epidemiology and differences in treatment given the limitation of the use of azoles in the pediatric field. A systematic literature review was performed using PubMed database listings between February 2014 and February 2020 using the following MeSH terms: leukemia, hematological malignancies, stem cell transplantation, mucormycosis, molds, prophilaxis, treatment.

EXPERT OPINION

The epidemiology of mucormycosis in HMs is changing in the last years. The availability of drugs more effective than in the past against this infection has reduced the mortality; however, a timely diagnosis remains a relevant problem potentially influencing the outcome of hematologic patients with IM.

Impact of human mesenchymal stromal cells on antifungal host response against Aspergillus fumigatus

Mesenchymal stromal cells (MSCs) are increasingly given as immunotherapy to hematopoietic stem cell transplant (HSCT) recipients with refractory graft-versus-host disease (GvHD). Whereas the immunosuppressive properties of MSCs seem to be beneficial in GvHD, there is, at the same time, major concern that MSCs increase the risk for infection. We therefore investigated the interplay of human MSCs with Aspergillus fumigatus and the impact of MSCs on different arms of the anti-Aspergillus host response in vitro. Although A. fumigatus hyphae increase mRNA levels of IL6 in MSCs, the extracellular availability of IL-6 and other pro-inflammatory cytokines remains unaffected. Human MSCs are able to phagocyte Aspergillus conidia, but phagocytosis of conidia is not associated with an alteration of the cytokine production by MSCs. In addition, human MSCs do not affect activation and function of A. fumigatus specific CD4+ T cells, and MSCs do not negatively impact the oxidative burst activity of phagocytes. Our in vitro data indicate that administration of human MSCs is not associated with a negative impact on the host response against A. fumigatus and that the fungus does not stimulate MSCs to increase the release of those cytokines which play a central role in the pathophysiology of GvHD.