In vitro and in vivo efficacies of Dectin-1-Fc(IgG)(s) fusion proteins against invasive fungal infections

Abstract

Fungal infections have increased in the last years, particularly associated to an increment in the number of immunocompromised individuals and the emergence of known or new resistant species, despite the difficulties in the often time-consuming diagnosis. The controversial efficacy of the currently available strategies for their clinical management, apart from their high toxicity and severe side effects, have renewed the interest in the research and development of new broad antifungal alternatives. These encompass vaccines and passive immunization strategies with monoclonal antibodies (mAbs), recognizing ubiquitous fungal targets, such as fungal cell wall β-1,3-glucan polysaccharides, which could be used in early therapeutic intervention without the need for the diagnosis at species-level. As additional alternatives, based on the Dectin-1 great affinity to β-1,3-glucan, our group developed broad antibody-like Dectin1-Fc(IgG)(s) from distinct subclasses (IgG2a and IgG2b) and compared their antifungal in vitro and passive immunizations in vivo performances. Dectin1-Fc(IgG2a) and Dectin1-Fc(IgG2b) demonstrated high affinity to laminarin and the fungal cell wall by ELISA, flow cytometry and microscopy. Both Dectin-1-Fc(IgG)(s) inhibited H. capsulatum and C. neoformans growth in a dose-dependent fashion. For C. albicans, such inhibitory effect was observed with concentrations as low as 0.098 and 0.049 µg/mL, respectively, which correlated with the impairment of the kinetics and lengths of germ tubes in comparison to controls. Previous opsonization with Dectin-1-Fc(IgG)(s) enhanced considerably the macrophage antifungal effector functions, increasing the fungi macrophages-interactions and significantly reducing the intraphagosome fungal survival, as lower CFUs were observed. The administration of both Dectin1-Fc(IgG)(s) reduced the fungal burden and mortality in murine histoplasmosis and candidiasis models, in accordance with previous evaluations in aspergillosis model. These results altogether strongly suggested that therapeutic interventions with Dectin-1-Fc(IgG)(s) fusion proteins could directly impact the innate immunity and disease outcome in favor of the host, by direct neutralization, opsonization, phagocytosis, and fungal elimination, providing interesting information on the potential of these new strategies for the control of invasive fungal infections.

β-1,3-Glucan recognition by Acanthamoeba castellanii as a putative mechanism of amoeba-fungal interactions

“…6 , second row). As described previously by our group ( 32 ), Dectin-1-Fc/IgG-anti-mouse-Alexa 546 labeling of β-1,3-glucans displays a ring-like pattern with randomly located clusters ( Fig. 6 , third row).…”

“…Subsequently, the cells were incubated with a streptavidin‐Alexa 488 conjugate (SouthernBiotech) diluted to 5 µg/mL with 2% BSA-DPBS for 1 h at RT. As a control for the presence of β-1,3-glucan on the fungal surface, the yeasts were incubated with 5 µg/mL Dectin-1-Fc ( 32 , 46 ) in 2% BSA-DPBS for 1 h at RT. After three washes with DPBS, yeasts were further incubated with an anti-mouse IgG Alexa 546 conjugate (SouthernBiotech) diluted to 5 µg/mL with 2% BSA-DPBS for 1 h at RT.…”

Comparative Genomics of Histoplasma capsulatum and Prediction of New Vaccines and Drug Targets

“…There is a paucity of studies on reverse vaccinology, prediction of potential vaccines and drug targets on dimorphic fungi. Additionally, currently, there is a lack of vaccines for fungal diseases despite the attempts of some studies to look for targets of vaccines that may be effective in reducing the rates of systemic mycoses, among them, histoplasmosis [ 25 , 26 , 27 , 28 ]. The search for putative targets is a starting point for drug and vaccine development studies.…”