Bma-LAD-2, an intestinal cell adhesion protein, as a potential therapeutic target for lymphatic filariasis

Abstract

Lymphatic filariasis (LF) is a debilitating disease that afflicts over 70 million people worldwide. It is caused by the parasitic nematodes Wuchereria bancrofti, Brugia malayi, and Brugia timori. While efforts to eliminate LF have seen substantial success, complete eradication will likely require more time and resources than predicted. Identifying new drug and vaccine targets in adult filariae could help elimination efforts. This studys aim was to evaluate intestinal proteins in adult Brugia malayi worms as possible therapeutic targets. Using siRNA, we successfully inhibited transcripts of four candidate genes: Bma-Serpin, Bma-ShTK, Bma-Reprolysin, and Bma-LAD-2. Of those, Bma-LAD-2, an immunoglobulin superfamily cell adhesion molecule (IgSF CAM), was determined to be essential for adult worm survival. We observed a 70.42% knockdown in Bma-LAD-2 transcript levels 1 day post-siRNA incubation and an 87.02% reduction in protein expression 2 days post-siRNA incubation. This inhibition of Bma-LAD-2 expression resulted in an 80% decrease in worm motility over 6 days, a 93.43% reduction in microfilaria release (Mf) by day 6 post-siRNA incubation, and a significant decrease in MTT reduction. Transmission electron microscopy revealed the loss of microvilli and unraveling of mitochondrial cristae in the intestinal epithelium of Bma-LAD-2 siRNA-treated worms. Strikingly, Bma-LAD-2 siRNA-treated worms exhibited an almost complete loss of pseudocoelomic fluid, suggesting that loss of these tight junctions led to the leakage and subsequent loss of the worms structural integrity. Luciferase immunoprecipitation system assay demonstrated that serum from 30 patients with LF did not have detectable IgE antibodies against Bma-LAD-2, indicating that LF exposure does not result in IgE sensitization to this antigen. These results indicate that Bma-LAD-2 is an essential protein for adult Brugia malayi and may be an effective drug or vaccine target. In addition, these findings further validate the strategy of targeting the worm intestine to prevent and treat helminthic infections. Author SummaryBrugia malayi is a parasitic nematode that can cause lymphatic filariasis, a debilitating disease prevalent in tropical and subtropical countries. Significant progress has been made towards eliminating the disease. However, complete eradication may require new therapeutics such as drugs or a vaccine that kill adult filariae. In this study, we identified an immunoglobulin superfamily cell adhesion molecule (Bma-LAD-2) as a potential drug and vaccine candidate. When we knocked down Bma-LAD-2 expression, we observed a decrease in worm motility, fecundity, and metabolism. We also visualized the loss of microvilli, destruction of the mitochondria in the intestinal epithelium, and loss of pseudocoelomic fluid contents after Bma-LAD-2 siRNA treatment. Finally, we demonstrated that serum from filaria-infected patients does not contain preexisting IgE to Bma-LAD-2, which indicates that this antigen would likely be safe to administer as a vaccine in endemic populations.