Figure 4.

Summary of recommendations for further studies involving animal models of invasive aspergillosis. Suggestions for standardization are based on objective analysis of all the published literature faced with the authors' personal experience. In light of all the benefits due to their small size, their costs and the large availability of reagents dedicated to, mice should be privileged. Within a 1–2 week-long period, immunocompromised status is easily achieved by repeated injections of low-cost drugs, like alkylating agents or steroids. Thereafter, a tracheo-pulmonary challenge is recommended by non-invasive device, like MicroSprayer® aerosolizer, allowing accurate control of the fungal inoculum. In such a context, no more than 10⁷ A. fumigatus conidia are usually needed to yield 90–100% infection rates. Generally, onset of clinical signs occurs within 48–72 h after the experimental inoculation. After that time, the challenged animals start becoming moribund from aspergillosis (ruffled fur, decreased defecation, lethargy, anorexia, weight loss, ataxia, various pulmonary signs, gross bleeding …). Although death remains the major clinical outcome, primarily in therapeutic assays, alternative endpoints may be assessed to estimate the fungal load while refining the animal welfare: nowadays, galactomannan antigen determination in blood and histopathology in lungs appear reliable and largely validated, in comparison with other surrogate biomarkers. ^*For therapeutic assays: outbred mouse strains like Albino Swiss Webster and CD-1; for pharmacology-pharmacokinetics and toxicology studies: outbred mouse strains like Swiss OF1 and NMRI; for immuno-pathophysiology: inbred mouse strains like C57BL/6, BALB/c, DBA2, 129/Sv, and CD2F1; for general purposes: C57BL/6 and BALB/c. ^#Referenced A. fumigatus strains should be privileged for inoculation, especially those that have been widely used so far, like AF293 and Dal/CEA10. Otherwise, it makes sense to use strains that were initially isolated in a relevant context of invasive aspergillosis. Environmental strains or local unreferenced strains should be avoided, because they don't allow large-scale reliable comparison. biw, Twice a week; D, Day (D₀ being the date of experimental challenge); GMS, Grocott-Gomori methenamine silver staining; IP, Intraperitoneal; ♂, Male; sc, Subcutanous; tiw, Thrice a week.