title: A new and clinically relevant murine model of solid-organ transplant aspergillosis.
abstract: Invasive fungal infections (IFIs) are a major cause of death in organ transplant patients. The murine hydrocortisone-mediated immunosuppression model of pulmonary aspergillosis is commonly used to characterise IFIs in these patients. However, this model does not take into account the effects of calcineurin inhibitors on transplant immunity to IFIs or the fungal calcineurin pathway, which is required for both virulence and antifungal drug resistance. To address these two issues, a new and clinically relevant transplant immunosuppression model of tacrolimus (FK506) and hydrocortisone-associated pulmonary aspergillosis was developed. We first characterised IFIs in 406 patients with a lung transplant. This showed that all of the patients with pulmonary aspergillosis were immunosuppressed with calcineurin inhibitors and steroids. Murine pharmacokinetic studies demonstrated that an ideal dose of 1 mg/kg/day of FK506 intraperitoneally produced blood trough levels in the human therapeutic range (5-12 ng/ml). There was increased mortality from pulmonary aspergillosis in a transplant-relevant immunosuppression model using both FK506 and hydrocortisone as compared with immunosuppression using hydrocortisone only. Lung histopathology showed neutrophil invasion and tracheobronchitis that was associated with reduced lung tumour necrosis factor-α (TNFα), JE (homologue of human MCP-1) and KC (homologue of human IL-8) at 24 hours, but increased lung TNFα, JE and KC at 48 hours when fungal burden was high. Furthermore, FK506 directly impaired fungal killing in alveolar macrophages in vitro, with FK506-mediated inhibition of the radial growth of Aspergillus fumigatus in vitro occurring at the low concentration of 5 ng/ml. Taken together, these findings show that the immunosuppressive activity of FK506 outweighs its antifungal activity in vivo. These observations demonstrate that FK506 impairs innate immune responses and leads to an incremental increase in susceptibility to IFIs when it is combined with steroids. This new and clinically relevant mouse model of invasive aspergillosis is a valuable addition to the further study of both fungal immunity and antifungal therapy in organ transplantation.
authors.affiliation: Department of Medicine, Imperial College London, Du Cane Road, London W12 0NN, UK.
authors.forename: Susanne
authors.initials: S
authors.lastname: Herbst
authors.forename: Anand
authors.initials: A
authors.lastname: Shah
authors.forename: Martin
authors.initials: M
authors.lastname: Carby
authors.forename: Gary
authors.initials: G
authors.lastname: Chusney
authors.forename: Naresh
authors.initials: N
authors.lastname: Kikkeri
authors.forename: Anthony
authors.initials: A
authors.lastname: Dorling
authors.forename: Elaine
authors.initials: E
authors.lastname: Bignell
authors.forename: Sunil
authors.initials: S
authors.lastname: Shaunak
authors.forename: Darius
authors.initials: D
authors.lastname: Armstrong-James
mesh_terms: D000818:Animals; D001232:Aspergillus fumigatus / Q000187:drug effects / Q000254:growth & development; D018932:Chemokine CCL2 / Q000378:metabolism; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D006801:Humans; D006854:Hydrocortisone / Q000494:pharmacology / Q000627:therapeutic use; D007165:Immunosuppression Therapy; D007166:Immunosuppressive Agents / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D007274:Injections, Intraperitoneal; D016209:Interleukin-8 / Q000378:metabolism; D016040:Lung Transplantation / Q000009:adverse effects*; D008297:Male; D051379:Mice; D011014:Pneumonia / Q000150:complications / Q000382:microbiology; D055732:Pulmonary Aspergillosis / Q000150:complications / Q000209:etiology* / Q000382:microbiology*; D012307:Risk Factors; D013256:Steroids / Q000494:pharmacology / Q000627:therapeutic use; D016019:Survival Analysis; D016559:Tacrolimus / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology / Q000627:therapeutic use; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D018932:Chemokine CCL2; D007166:Immunosuppressive Agents; D016209:Interleukin-8; D013256:Steroids; D014409:Tumor Necrosis Factor-alpha; D006854:Hydrocortisone; D016559:Tacrolimus