Liposomal amphotericin B activates antifungal resistance with reduced toxicity by diverting Toll-like receptor signalling from TLR-2 to TLR-4.
OBJECTIVE
Neutrophils play a crucial role in the control of the Aspergillus fumigatus infection and act in concert with antifungal drugs. This study was undertaken to obtain insights into the possible involvement of Toll-like receptors (TLRs) in the interaction of liposomal amphotericin B (L-AmB; AmBisome) with neutrophils in response to A. fumigatus.


METHODS
For generation of bone marrow-transplanted mice, irradiated C57BL6 mice were infused with T cell-depleted allogeneic donor cells. For infection, mice were injected intranasally with Aspergillus fumigatus conidia and treated with L-Amb and deoxycholate amphotericin B prophylactically or therapeutically. For TLR-dependent antifungal functions, murine neutrophils were preincubated with antifungals or TLR ligands before the addition of Aspergillus conidia.


RESULTS
The results show that: (a) neutrophil activation by Aspergillus occurs through TLR signalling pathways differently affecting the oxidative and non-oxidative mechanisms of the killing machinery; (b) by diverting signalling from TLR-2 to TLR-4, liposomes of AmBisome activate neutrophils to an antifungal state while attenuating the pro-inflammatory effects of deoxycholate amphotericin B; (c) this translates in vivo to the optimization of the AmBisome therapeutic efficacy in mice with aspergillosis.


CONCLUSIONS
These results provide a putative molecular basis for the reduced infusion-related toxicity of AmBisome and suggest that TLR manipulation in vivo is amenable to the induction of optimal microbicidal activity in the absence of inflammatory cytotoxicity to host cells.
Bellocchio
Silvia
S
Microbiology Sections, Department of Experimental Medicine and Biochemical Sciences, University of Perugia, Perugia, Italy.
Gaziano
Roberta
R
Bozza
Silvia
S
Rossi
Giordano
G
Montagnoli
Claudia
C
Perruccio
Katia
K
Calvitti
Mario
M
Pitzurra
Lucia
L
Romani
Luigina
L
D000666:Amphotericin B / Q000008:administration & dosage* / Q000633:toxicity; D000818:Animals; D000935:Antifungal Agents / Q000008:administration & dosage* / Q000633:toxicity; D025141:Drug Resistance, Fungal / Q000187:drug effects* / Q000502:physiology; D005260:Female; D006801:Humans; D008081:Liposomes; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4
D000935:Antifungal Agents; D008081:Liposomes; D011956:Receptors, Cell Surface; C493486:Tlr2 protein, mouse; C493487:Tlr4 protein, mouse; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D000666:Amphotericin B