Validation of ultrasound bioimaging to predict worm burden and treatment efficacy in preclinical filariasis drug screening models

Abstract

Filariasis is a global health problem targeted for elimination. Curative drugs (macrofilaricides) are required to accelerate elimination. Candidate macrofilaricides require testing in preclinical models of filariasis. The incidence of infection failures and high intra-group variation means that large group sizes are required for drug testing. Further, a lack of accurate, quantitative adult biomarkers results in protracted timeframes or multiple groups for endpoint analyses. Here we evaluate intra-vital ultrasonography (USG) to identify B. malayi in the peritonea of gerbils and CB.17 SCID mice and assess prognostic value in determining drug efficacy. USG operators, blinded to infection status, could detect intra-peritoneal filarial dance sign (ipFDS) with 100% specificity and sensitivity, when >5 B. malayi worms were present in SCID mice. USG ipFDS was predictive of macrofilaricidal activity in randomized, blinded studies comparing flubendazole, albendazole and vehicle-treated SCID mice. Semi-quantification of ipFDS could predict worm burden >10 with 87–100% accuracy in SCID mice or gerbils. We estimate that pre-assessment of worm burden by USG could reduce intra-group variation, obviate the need for surgical implantations in gerbils, and reduce total SCID mouse use by 40%. Thus, implementation of USG may reduce animal use, refine endpoints and negate invasive techniques for assessing anti-filarial drug efficacy.

A mouse infection model and long-term lymphatic endothelium co-culture system to evaluate drugs against adult Brugia malayi

“…Through an extensive meta-analysis of 32 independent sub-periodic human strain B. malayi infection experiments undertaken in our laboratory between 2012-2018, including untreated or vehicle control data derived from published in vivo preclinical model development, drug screening or immunological investigations [6, 15, 18-20, 23, 25, 45-49], we determined that immunodeficient mouse strains serve as improved models for propagations of adults. Whilst we have previously described reduced variability of adult worm burden and less frequent occurrence of infection failures in CB.17 SCID mice compared with gerbils [18], we extend our conclusions here that CB.17 SCID mice afford a >3-fold more productive source of adult infections per unit inoculation. Improvements in yields become more pronounced with chronicity of infection with >10-fold increases in adult burdens in >25-week old infections.…”

“…More recently, Severe-Combined ImmunoDeficient (SCID) mice, deficient in adaptive immunity, have been appraised as long-term fully susceptible hosts for B. malayi and the human filarial pathogen, Loa loa, and have been subsequently validated as drug screening models [15][16][17]. Brugia malayi infection success and variability in adult yields are more consistent in SCID mice compared with gerbils [18]. We have recently identified that adaptive immune control of B. malayi in mice is dependent on interleukin (IL)-4 receptor-alpha (Rα) macrophage activation mediating recruitment of a vigorous tissue eosinophilia [19].…”

Preclinical development of an oral anti- Wolbachia macrolide drug for the treatment of lymphatic filariasis and onchocerciasis

“…Infected animals were randomly assigned into dose groups with n = 3 to 7 for larval-stage testing and n = 4 to 9 for adult-stage testing. Randomization was done by stratification based on ID number (B. malayi larval and prefecund adult infections), baseline ultrasonography estimates of worm burden (B. malayi infection of SCID mice and gerbils) using a semi-quantifiable scoring system (26), baseline microfilariaemia (L. sigmodontis infection of gerbils), or order of implantation and source of male worms (O. ochengi implantation into SCID mice or gerbils).…”

Structural Requirements for Dihydrobenzoxazepinone Anthelmintics: Actions against Medically Important and Model Parasites: Trichuris muris, Brugia malayi, Heligmosomoides polygyrus, and Schistosoma mansoni

“…After 6 days of drug exposure, mf were also tested for metabolic activity, a measure of parasite viability, using the MTT assay (Figure C). The MTT assay is part of the WHO-approved in vitro assay for antifilarial activity using O. gutturosa and has been previously used for assessment of B. malayi metabolic status. − 1 and 14 in particular showed activity in this assay, significantly reducing B. malayi mf MTT reductase activity on average by 53 and 82%, respectively (one-way ANOVA with Holm–Sidak’s multiple comparison tests, P < 0.01 and P < 0.0001). The time course of the effect of 1 against mf motility at different concentrations is shown in Supplementary Figure 3.…”