An in vivo RNAi approach to disrupt development in the filarial worm, Brugia malayi

Lymphatic filariasis is a disease caused by mosquito-borne filarial nematodes including Wuchereria bancrofti and Brugia malayi (B. malayi). Although over 120 million people suffer from this disfiguring disease, chemotherapeutic options for LF are limited to three drugs: diethylcarbamazine citrate (DEC), albendazole and ivermectin. The threat of drug resistance combined with the inefficacy of these drugs against adult parasites highlights the need for new anthelmintic drugs. Cathepsins are a large family of cysteine proteases with 10 different members identified in B. malayi. They are involved in a number of important biological processes in free living and parasitic nematodes including molting and motility. This makes cathepsins potential targets for drug or vaccine development. However, drug development has been hampered due to the intractability of parasitic nematodes to experimental methods such as RNA interference (RNAi). Previous work in our lab showed that a parasite gene of interest could be suppressed by RNAi in a model system whereby mosquitoes were infected with B. malayi by injection. Here we tested the efficiency of RNAi in mosquitoes in which B. malayi infection was established by the natural route (i.e. exposure via blood-feeding). We used this method to explore the role of the gene encoding cathepsin L-like cysteine protease 1, CPL-1, in B. malayi biology. This “in-squito” protocol to suppress CPL-1 resulted in an 80% decrease in transcript abundance and multiple aberrant phenotypes thus demonstrating that this method can be used to successfully suppress parasite gene expression within the mosquito intermediate host.