Defining the target and the effect of imatinib on the filarial c-Abl homologue

Abstract

BackgroundPreviously we demonstrated the micro- and macrofilaricidal properties of imatinib in vitro. Here we use electron and multiphoton microscopy to define the target of imatinib in the adult and microfilarial stages of Brugia malayi and assess the effects of pharmacologically relevant levels of imatinib on the adult parasites.MethodsAfter fixation of adult B. malayi males and females, sections were stained with polyclonal rabbit anti-c-Abl antibody (or isotype control) and imaged with multiphoton fluorescent microscopy. Microfilariae were fixed and labeled with rabbit anti-c-Abl IgG primary antibody followed by anti-rabbit gold conjugated secondary antibody and imaged using transmission electron microscopy (TEM; immunoEM). In addition, adult B. malayi males and females were exposed to 0 or 10μM of imatinib for 7 days following which they were prepared for transmission electron microscopy (TEM) to assess the drug’s effect on filarial ultrastructure.ResultsFluorescent localization of anti-c-Abl antibody demonstrated widespread uptake in the adult filariae, but the most intense signal was seen in the reproductive organs, muscle, and intestine of both male and female worms. Fluorescence was significantly more intense in the early microfilarial stage (i.e. early morula) compared with later development stages (i.e. pretzel). Anti-c-Abl antibody in the microfilariae localized to the nuclei. Based on TEM assessment following imatinib exposure, imatinib appeared to be detrimental to embryogenesis in the adult female B. malayi.ConclusionsAt pharmacologically achievable concentrations of imatinib, embryogenesis is impaired and possibly halted in adult filariae. Imatinib is likely a slow microfilaricide due to interference in intra-nuclear processes, which are slowly detrimental to the parasite and not immediately lethal, and thus may be used to lower the levels of L. loa microfilariae before they are treated within the context of conventional mass drug administration.

Mining Filarial Genomes for Diagnostic and Therapeutic Targets

“…Given the structural similarity of these c-Abl like proteins in the filarial nematodes, and the conserved binding site of the TKI, it is likely to be successful in targeting the parasites that cause lymphatic filariasis, loiasis and onchocerciasis [100]. Because the expression of c-abl-like protein localized predominantly to the reproductive organs, muscle and intestine of the adult B. malayi worms, an effort to perform clinical trials in humans (e.g., NCT02644525) with drugs such as these TKIs that are effective as both micro- and macrofilaricides might greatly shorten the length of MDA treatment and significantly boost elimination efforts [101].…”

Reduction of Loa loa Microfilaremia with Imatinib — A Case Report

“…4 The inhibition of this L. loa c-Abl–like tyrosine kinase with imatinib led to the slow death of microfilariae in vitro, 4 probably because imatinib targets the tyrosine kinase expression in the nuclei of the microfilariae. 5 …”

High-resolution AP-SMALDI MSI as a tool for drug imaging in Schistosoma mansoni

“…Imatinib, also known as Gleevec or Glivec (Novartis, Basel, Switzerland; formerly referred to as STI571 or CGP57148B), is used for therapy of chronic myeloid leukemia and malignant gastrointestinal stroma tumors in humans [ 12 , 14 ]. In in vitro assays, imatinib has shown additional efficacy against multicellular and unicellular parasites with high relevance to human health such as S. mansoni and S. japonicum [ 15 , 16 ] but also against Echinococcus multilocularis [ 17 ], filaria [ 18 , 19 ], Plasmodium [ 20 , 21 ], and Leishmania [ 22 ]. Two Abl orthologs and an Abl/Src hybrid kinase occur in S. mansoni and are targets of imatinib [ 15 , 23 , 24 ].…”