Localization and RNAi-driven inhibition of a Brugia malayi encoded Interleukin-5 Receptor Binding protein

A molecule termed BmIL5Rbp (aka Bm8757) was identified from Brugia malayi filarial worms and found to competitively inhibit human IL-5 binding to its human receptor. After the expression and purification of a recombinant BmIL5Rbp and generation of BmIL5Rbp-specific rabbit antibody, we localized the molecule on B. malayi worms through immunohistochemistry and immunoelectron microscopy. RNA interference was used to inhibit BmIL5Rbp mRNA and protein production. BmIL5Rbp was shown to localize to the cuticle of Brugia malayi and to be released in their excretory/secretory products. RNAi inhibited BmIL5Rbp mRNA production by 33% and reduced the surface protein expression by ~50% and suppressed the release of BmIL5Rbp in the excretory/secretory products. RNAi has been used successfully to knock down the mRNA and protein expression of BmIL5Rbp in the early larval stages of B. malayi and provided a proof-of-principle for the local inhibition of the human IL5 receptor. These findings provide evidence that a parasite encoded IL5R antagonist could be utilized therapeutically.