The in vitro culture protocol established at helminGuard allows the stable maturation of Schistosoma mansoni larvae into adult parasites including deposition of viable eggs and hatching of miracidia. The worms are kept with human blood/constituents to mimic their natural environment, i.e. human blood/vessels. Thus, immune cells and immune factors are present in the assay milieu. The presence of these factors is essential for potentiating the mode of action of anthelminthic compounds such as praziquantel, and represents a key advantage of this functional assay format over target-based biochemical or cellular assays.
In vitro-grown 12-day-old Schistosoma mansoni larvae
In vitro-matured S. mansoni couples and in vitro-laid eggs of various maturation stages
First infectious miracidia from eggs of in vitro-grown schistosomes
Recently, we have successfully modified our culture conditions to raise fertile eggs releasing infectious miracidia.
As shown in the above video, maturation and vitality of most in vitro raised eggs/miracidia does not yet reach that of their ex vivo counterparts with many miracidia being morphologically and functionally hampered: short, pear-shaped bodies and slow meandering, rotating or circle-like movements. However, there are already long, quickly moving in vitro-raised miracidia, which are not distinguishable from their ex vivo counterparts. The infection rate of B. glabrata snails by in vitro miracidia is at about 10%, so far, which is way below the 90-100% obtained with ex vivo miracidia.
Despite the yet existing limitations, it is now possible to maintain the S. mansoni life cycle without infecting mammalian animals as an important further step in implementing the Three Rs (3Rs) principle.
*supported by the Federal Ministry for Education and Research Program “Alternative Methods to Animal Experiments”, BMBF/PTJ 0315277