Dectin-3-targeted antifungal liposomes efficiently bind and kill diverse
fungal pathogens
Abstract
DectiSomes are anti-infective drug-loaded liposomes targeted to
pathogenic cells by pathogen receptors including the Dectins. We have
previously used C-type lectin (CTL) pathogen receptors Dectin-1,
Dectin-2, and DC-SIGN to target DectiSomes to the extracellular
oligoglycans surrounding diverse pathogenic fungi and kill them.
Dectin-3 (a.k.a. MCL, CLEC4D) is a CTL pathogen receptor whose
known cognate ligands are partly distinct from other CTLs. We expressed
and purified a truncated Dectin-3 polypeptide (DEC3) comprised of its
carbohydrate recognition domain and stalk region. We prepared
amphotericin B (AmB)-loaded pegylated liposomes (AmB-LLs) and coated
them with this isoform of Dectin-3 (DEC3-AmB-LLs), and we prepared
control liposomes coated with Bovine Serum Albumin (BSA-AmB-LLs).
DEC3-AmB-LLs bound to the exopolysaccharide matrices of Candida
albicans, Rhizopus delemar (f.k.a. R. oryzae), and
Cryptococcus neoformans from one to several orders of magnitude
more strongly than untargeted AmB-LLs or BSA-AmB-LLs. The data from our
quantitative fluorescent binding assays were standardized using a
CellProfiler program, AreaPipe, that was developed for this purpose.
Consistent with enhanced binding, DEC3-AmB-LLs inhibited and/or killed
C. albicans and R. delemar more efficiently than control
liposomes, which significantly reduced the effective dose of AmB. In
conclusion, Dectin-3 targeting has the potential to advance our goal of
building pan-antifungal DectiSomes.