Short-course quinazoline drug treatments are effective in the Litomosoides sigmodontis and Brugia pahangi jird models

Abstract

The quinazolines CBR417 and CBR490 were previously shown to be potent anti-wolbachials that deplete Wolbachia endosymbionts of filarial nematodes and present promising pre-clinical candidates for human filarial diseases such as onchocerciasis. In the present study we tested both candidates in two models of chronic filarial infection, namely the Litomosoides sigmodontis and Brugia pahangi jird model and assessed their long-term effect on Wolbachia depletion, microfilariae counts and filarial embryogenesis 16−18 weeks after treatment initiation (wpt). Once per day (QD) oral treatment with CBR417 (50 mg/kg) for 4 days or twice per day (BID) with CBR490 (25 mg/kg) for 7 days during patent L. sigmodontis infection reduced the Wolbachia load by >99% and completely cleared peripheral microfilaremia from 10–14 wpt. Similarly, 7 days of QD treatments (40 mg/kg) with CBR417 or CBR490 cleared >99% of Wolbachia from B. pahangi and reduced peritoneal microfilariae counts by 93% in the case of CBR417 treatment. Transmission electron microscopy analysis indicated intensive damage to the B. pahangi ovaries following CBR417 treatment and in accordance filarial embryogenesis was inhibited in both models after CBR417 or CBR490 treatment. Suboptimal treatment regimens of CBR417 or CBR490 did not lead to a maintained reduction of the microfilariae and Wolbachia load. In conclusion, CBR417 or CBR490 are pre-clinical candidates for filarial diseases, which achieve long-term clearance of Wolbachia endosymbionts of filarial nematodes, inhibit filarial embryogenesis and clear microfilaremia with treatments as short as 7 days.

Oxfendazole mediates macrofilaricidal efficacy against the filarial nematode Litomosoides sigmodontis in vivo and inhibits Onchocerca spec. motility in vitro

“…The L . sigmodontis rodent model has been used to validate macrofilaricidal drug candidates by a consortium led by the Bill & Melinda Gates Foundation, Drugs for Neglected Diseases initiative (DND i ), academia, and pharmaceutical companies and has supported the advancement of a few macrofilaricidal compounds through preclinical and clinical development [ 17 , 22 – 28 ]. In this study we demonstrate that oxfendazole exhibits excellent macrofilaricidal efficacy following both oral and sc administrations in the L .…”

The endosymbiont Wolbachia rebounds following antibiotic treatment

“…Wolbachia titers in adult male and female worms were determined by qPCR at 1 week, 6 weeks, 17 weeks and 8 months post-first dose following the protocol by McGarry et al [ 37 ]. The relative abundance of single copy genes encoding the Wolbachia surface protein ( wsp ) were normalized to that of Brugia glutathione-S-transferase gene ( gst ) [ 28 , 29 , 38 – 40 ]. At the 1-week timepoint, Wolbachia titers were significantly reduced by 95.2% in female worms ( Fig 1A ).…”

“…Wolbachia titers were reduced by >95% in female worms from rifampicin treated animals at the 1-week timepoint compared to those of worms from vehicle animals. The extensive reduction of Wolbachia titers in adult worms has been previously described in other rodent studies with filarial worms, but the studies were terminated 16-18 weeks post-treatment [26,27,29,40,50], and the long-term effects of antibiotic treatment on filarial worms and their Wolbachia were not evaluated in these models.…”

“…Several studies have recently shown that short courses of 7-and 14-days of anti-Wolbachia compounds hold promise as excellent drugs to treat onchocerciasis and LF [25][26][27][28][29]. Studies by Hübner et al however, showed that suboptimal treatment regimens of doxycycline in the Litomosoides sigmodontis infection model did not lead to a sustained reduction in Wolbachia loads in worms 14-18 weeks post-treatment and that longer term studies were needed to assess permanent sterilization of female adult worms [27,29].…”

“…Several studies have recently shown that short courses of 7-and 14-days of anti-Wolbachia compounds hold promise as excellent drugs to treat onchocerciasis and LF [25][26][27][28][29]. Studies by Hübner et al however, showed that suboptimal treatment regimens of doxycycline in the Litomosoides sigmodontis infection model did not lead to a sustained reduction in Wolbachia loads in worms 14-18 weeks post-treatment and that longer term studies were needed to assess permanent sterilization of female adult worms [27,29]. Although West African cattle infected with Onchocerca ochengi are excellent hosts for long-term studies to evaluate the efficacy of antibiotics for the treatment of human onchocerciasis [30][31][32][33][34][35][36], the purpose of our study was to investigate the long-term effects of rifampicin in a rodent model of infection.…”