Improvement of in vitro culture conditions of Brugia pahangi four day old developing larvae for use in an antifilarial drug assay.

Four day old third stage larvae of Brugia pahangi were cultured in the presence of differing concentrations of early passage dog kidney cells and inactivated foetal calf serum. After a six day culture period worm length, number of moults and worm mortality were determined. Analysis of the length data demonstrated a significant interactive relationship between cell and serum concentration. The greatest increases in length were obtained using an initial cell density of dog kidney cells of 40 x 10(4) plus a serum concentration of 10%. (The surface area of all culture vessels was 2.0 cm2). In addition moulting occurred earlier and was more prolific with higher cell and serum concentrations. The response of larvae to antiparasitic agents in the presence or absence of a confluent dog kidney feeder layer was then compared to determine whether the inclusion of cells altered drug effects. From this it was found that the killing effects of flubendazole, albendazole, furazolidone, levamisole and nifurtimox at their minimum effective concentrations were delayed under biphasic culture conditions. It is suggested that this is an advantage and will improve the selectivity of the assay over and above an assay which does not include a cell feeder layer. In addition the improved growth rates obtained in cultures containing dog kidney cells should mean an increase in test sensitivity to agents capable of disrupting biosynthesis.