Evaluation of two in vitro test systems employing Brugia malayi parasite for prescreening of potential antifilarials

In the present study, we employed adult worms and microfilariae of the huma n filarial parasite, Brugia malayi, in two in vitro systems and evaluated t he suitability of the systems as prescreens for identifying potential antif ilarials. A total of 38 new synthetic compounds and 19 plant products that were found active or inactive in Acanthocheilonema viteae-Mastomys coucha ( rodent filariid in rodent host) and/or B. malayi-M. coucha (human filariid in rodent host) models, were tested in the in vitro systems using inhibitio n of worm motility (motility assay) and inhibition of MTT reduction potenti al (MTT assay) of the parasite as test parameters. Two known antifilarials, ivermectin and diethylcarbamazine, mere included as standards. All (100%) the synthetic and plant products that were active in B. malayi-M. coucha mo del were also found active in the in vitro systems: About 82% and 20% of sy nthetic and plant products respectively that were active in A. viteae-M. co ucha system were positive and 87.5% of the synthetic products and 9% of the plant products found inactive in A. viteae-M. coucha system were also posi tive in the ill vitro systems. The results show that plant products showing LC100 in the range of 31.25 mu g/ml to 62.5 mu g/ml in the in vitro system s can be considered as potential antifilarials and followed-up in in vivo a ssay systems. It is concluded that the motility and MTT assays using both t he life forms of B. malayi are reliable prescreens with high predictive val ue; both the assays are necessary for screening synthetic compounds whereas the motility assay using adult worms alone appears sufficient for screenin g plant products.