Optimization of culture conditions for the maintenance of Onchocerca gutturosa adult worms in vitro

Abstract

A series of experiments examined the effects of various media, serum supplements, gas phases and the incorporation of mammalian cell feeder layers on the survival on Onchocerca gutturosa adult worms in vitro. The survival of male worms was poor in all media tested that were not supplemented with inactivated foetal calf serum (IFCS), with improved but variable survival in media supplemented with 10–30% IFCS. Using a cell-free system in an atmosphere of 5% CO₂in air, good results were obtained in medium NCTC 135 + 10% IFCS (median survival time 39 days, range 25–41). Marginally better survival was obtained with the same medium in an atmosphere of 95% N₂/5% CO² (medium 45 days, range 25–56)and with a 1:1 mixture of media NCTC 135 and IMDM+10% IFCS(medium 38 days, range 38–51). Survival was enhanced in culture systems which incorporated bovine kindney (MDBK) cells, bovine trachea (EBTR) cells and monkey kidney (LLCMK2) cells. Exceptionally long survival was obtained using medium MEM+10% IFCS+LLCMK2 cells under a gas phase of 5% CO₂in air, in which male worms survived from approximately 6 to over 7 months. Under similar conditions, female worms were also maintained for periods of up to 6 months and 5 out of 18 specimens released microfilariae into the culture system. The long-term culture described in this study will be useful for basic biochemical, chemotherapeutic and immunological studies in vitro.