In Vivo Synergy of Amphotericin B plus Posaconazole in Murine Aspergillosis

Aspergillus fumigatus escape mechanisms from its harsh survival environments

Aspergillus fumigatus is a ubiquitous pathogenic mold and causes several diseases, including mycotoxicosis, allergic reactions, and systemic diseases (invasive aspergillosis), with high mortality rates. In its ecological niche, the fungus has evolved and mastered many reply strategies to resist and survive against negative threats, including harsh environmental stress and deficiency of essential nutrients from natural environments, immunity responses and drug treatments in host, and competition from symbiotic microorganisms. Hence, treating A. fumigatus infection is a growing challenge. In this review, we summarized A. fumigatus reply strategies and escape mechanisms and clarified the main competitive or symbiotic relationships between A. fumigatus, viruses, bacteria, or fungi in host microecology. Additionally, we discussed the contemporary drug repertoire used to treat A. fumigatus and the latest evidence of potential resistance mechanisms. This review provides valuable knowledge which will stimulate further investigations and clinical applications for treating and preventing A. fumigatus infections. KEY POINTS: • Harsh living environment was a great challenge for A. fumigatus survival. • A. fumigatus has evolved multiple strategies to escape host immune responses. • A. fumigatus withstands antifungal drugs via intrinsic escape mechanisms.

Challenges in the Treatment of Invasive Aspergillosis in Immunocompromised Children

Invasive aspergillosis (IA) is associated with significant morbidity and mortality. Voriconazole remains the drug of choice for the treatment of IA in children; however, the complex kinetics of voriconazole in children make dosing challenging and therapeutic drug monitoring (TDM) essential for treatment success. The overarching goal of this review is to discuss the role of voriconazole, posaconazole, isavuconazole, liposomal amphotericin B, echinocandins, and combination antifungal therapy for the treatment of IA in children. We also provide a detailed discussion of antifungal TDM in children.

Outcomes of a Modified Treatment Ladder Algorithm Using Retrobulbar Amphotericin B for Invasive Fungal Rhino-Orbital Sinusitis

PURPOSE

To assess whether a modified treatment ladder algorithm incorporating transcutaneous retrobulbar amphotericin B (TRAMB) for invasive fungal rhino-orbital sinusitis can reduce the risk of exenteration without compromising survival.

DESIGN

Retrospective, comparative clinical study with historical control subjects.

METHODS

Fifty consecutive patients with biopsy-proven invasive fungal sinusitis and radiographic evidence of orbital involvement were evaluated at a single tertiary institution from 1999-2020. TRAMB was incorporated as part of the treatment algorithm in 2015. Demographics, underlying immune derangement, infective organism, ophthalmic examination, surgical care, and survival were compared in a quasiexperimental pre-post format, dividing patients into a pre-2015 group and a post-2015 group. Risk of exenteration and mortality were the primary outcomes.

RESULTS

Baseline characteristics did not differ significantly between the 2 groups. Nearly all patients underwent a surgical intervention, most commonly functional endoscopic sinus surgery with debridement. TRAMB was administered to 72.7% of the post-2015 group. Exenteration was more common in the pre-2015 group (36.4% vs 9.1% [95% confidence interval {CI} 5.2-48.8]; P = .014), while mortality was similar (40.0% vs 36.7% [95% CI -22.1 to 29.3]; P = .816). After adjusting for potential confounders, patients treated after 2015 were found to have lower risk of exenteration (relative risk 0.28 [95% CI 0.08-0.99]; P = .049) and similar risk of mortality (relative risk 1.04 [95% CI 0.50-2.16]; P = .919).

CONCLUSION

Compared with historical control subjects, patients with invasive fungal rhino-orbital sinusitis who were treated with a modified treatment ladder algorithm incorporating TRAMB had a lower risk of disfiguring exenteration without an apparent increase in the risk of mortality.

ASP2397 Is a Novel Natural Compound That Exhibits Rapid and Potent Fungicidal Activity against Aspergillus Species through a Specific Transporter

Current therapies against invasive pulmonary aspergillosis (IPA) have a limited cure rate. Given that a delay in treatment initiation may be fatal, a new drug with rapid-onset and potent fungicidal activity is needed. The novel cyclic hexapeptide ASP2397 (currently known as VL-2397) exhibited antifungal activity against Aspergillus fumigatus (including azole-sensitive and azole-resistant isolates), A. terreus, and A. flavus at an MIC range of 1 to 4 μg/ml in human serum. Time-kill curve experiments showed that ASP2397 reduced germinated conidia of A. fumigatus by more than 1 log₁₀ CFU within 6 h. In addition, ASP2397 inhibited hyphal elongation from germinated conidia of A. fumigatus, A. terreus, and A. flavus more rapidly than voriconazole. Under conditions of delayed treatment initiation in an IPA mouse model, ASP2397 had efficacy superior to that of posaconazole, with 100% survival and over 1 log₁₀ CFU/g reduction in lung fungal burden. Histopathological investigation of lungs also showed that ASP2397 markedly suppressed disease progression. To clarify its mechanism of action, we generated a UV-induced mutant of A. fumigatus with low susceptibility to ASP2397. The mutant had a point mutation in the siderophore transporter gene sit1, which is absent in mammalian cells. These findings suggest that ASP2397 may improve clinical treatment options for IPA.

Increased Efficacy of Oral Fixed-Dose Combination of Amphotericin B and AHCC® Natural Adjuvant against Aspergillosis

Invasive pulmonary aspergillosis represents one of the most serious fungal infections among immunocompromised patients. In this study, we aimed to analyze the in vivo efficacy of prophylactic oral amphotericin B (AMB) encapsulated in modified chitosan-nanoparticles (Nanomerics’ Molecular Envelope Technology (MET)) supplemented with a standardized extract of cultured Lentinula edodes mycelia (AHCC^®) in a murine model of pulmonary aspergillosis. We determined fungal burden and survival of mice and additionally, we carried out a cytokine analysis in an attempt to understand the immunomodulation of the extract. Our results evidenced equivalent efficacy between orally administered AMB-MET and the intravenous liposomal AMB marketed formulation. Addition of the AHCC^® supplement significantly improved efficacy in terms of burden reduction and survival increase of both oral and intravenous AMB therapies compared to the untreated control group. Moreover, a protective effect of the extract was observed in terms of weight loss. Regarding the cytokine profiles, the Th1 immune response was stimulated in treated animals when compared to the control group. This response was marked by an enhancement in the MCP-1, GM-CSF, VEGF, RANTES and IL-17 levels and a decrease in the IL-6, a biomarker related to the severity of the infection.