Isavuconazole for Treatment of Experimental Fungal Endophthalmitis Caused by Aspergillus fumigatus

Abstract

Fungal endophthalmitis remains a significant cause of vision impairment and blindness. Moreover, the prognosis is poor, in part due to delay in diagnosis and to limited availability of effective antifungal agents with good ocular penetration. Thus, it is imperative to evaluate the therapeutic efficacy in fungal endophthalmitis of newer antifungal agents. In this study, we assessed the efficacy of isavuconazole in treating Aspergillus fumigatus endophthalmitis in an exogenous mouse model of the disease. Briefly, endophthalmitis was induced by intravitreal (IVT) injection of A. fumigatus spores into immunocompetent C57BL/6 (B6) mouse eyes. Mice were randomized into five groups that received isavuconazole via (i) oral gavage, (ii) IVT injections, (iii) intravenous injection, (iv) IVT injection followed by oral gavage, and (v) IVT injection followed by intravenous injection. Our data showed that isavuconazole treatment via all routes reduced fungal burden in A. fumigatus-infected eyes. This coincided with the preservation of retinal structural integrity (histology analysis) and retinal function (electroretinography [ERG] analysis), resulting in significantly improved disease outcome. Furthermore, isavuconazole treatment reduced the levels of inflammatory cytokines (tumor necrosis factor α [TNF-α], interleukin 1β [IL-1β], and IL-6) and cellular infiltration in the eyes. Notably, oral administration of isavuconazole was as effective in ameliorating endophthalmitis as intravitreal injection of the drug. Collectively, our study demonstrates that isavuconazole is effective in treating A. fumigatus endophthalmitis in mice, indicating its potential use in human ocular infections.

Keywords: Aspergillus; ERG; endophthalmitis; inflammation; isavuconazole; ocular immunology; retina.

FIG 1

Isavuconazole is effective in treating A. fumigatus (AF) endophthalmitis. (A) Schematic showing the experimental model, isavuconazole treatment groups (n = 8/group), and methods to monitor the disease progression in fungal endophthalmitis. (B) Representative micrographs obtained by slit-lamp microscopy on day 4 postinfection/treatment. The white intraocular opacity in some eyes is due to cataract formation from anesthesia. IVT, intravitreal; IV, intravenous; Isa, isavuconazole.

FIG 2

Isavuconazole treatment ameliorated mouse retinal tissue damage in A. fumigatus endophthalmitis. (A) Representative hematoxylin- and eosin-stained sections (n = 8/group) of eyes from C57BL/6 mice of both sexes that were infected with Aspergillus fumigatus (AF) and treated with isavuconazole (Isa) by the indicated routes (detailed in methods). Eyes were obtained on day 4 postinfection/treatment. (B) The degree and number of retinal folds were assessed in hematoxylin- and eosin-stained images described in panel A, with more folds being indicative of greater damage. **, P < 0.005; ***, P < 0.001 by Student's t test. R, retina; ON, optic nerve; VH, vitreous humor; L, lens, IV, intravenous.

FIG 3

Isavuconazole treatment preserved retinal function in A. fumigatus (AF) endophthalmitis. Electroretinography (ERG) responses were recorded from uninfected control, A. fumigatus-infected untreated, and A. fumigatus-infected, isavuconazole-treated eyes (n = 8/group). (A) Experimental setup to record mouse ERG and (B) a representative ERG wave showing amplitudes of a waves (blue) and b waves (red) in a normal C57BL/6 mouse. (C) For comparative analysis amplitudes of both a- and b-wave from the uninfected control mice were set at 100%. The untreated and isavuconazole-treated groups were compared to the uninfected control group and results were graphed as a percentage of the normal retinal function retained ± SD. **, P < 0.005; ***, P < 0.001 by one-way analysis of variance (ANOVA). IV, intravenous.

FIG 4

Isavuconazole treatment reduces fungal burden and inflammatory cytokines in A. fumigatus-infected eyes. The eyes (n = 8/group) of C57BL/6 mice were uninfected (control), infected with A. fumigatus and untreated (AF), or treated with isavuconazole (Isa) by the indicated routes (details in Materials and Methods). (A) Estimation of fungal burden as determined by the number of fungal CFU per eye. (B, C, and D) Indicated inflammatory cytokine levels as assessed by enzyme-linked immunosorbent assay (ELISA). The untreated and isavuconazole-treated groups were compared. For bacterial burden, the data represent mean ± SEM; for cytokines, data represent mean ± SD. *, P < 0.05; **, P < 0.005; ***, P < 0.001 by Student's t test. IV, intravenous.