Caenorhabditis elegans as a biomonitor for immunological stress in nematodes

An experimental system has been developed using Caenorhabditis elegans (Sec ernentea: Rhabditida), to monitor immunological stress in nematodes. The tr ansgenic C. elegans strain PC72 carries a lacZ reporter gene fused to a C. elegans hsp16-1 gene, which is inducible for beta-galactosidase activity at the heat stress temperature of 26 degrees C. The investigate the possibili ty of using PC72 to monitor immunological stress, its surface coat was targ eted, to mimic immune attack, by raising immune sera against surface coat c omponents selectively removed by the cationic detergent cetyltrimethylammon iunm bromide. initially, a highly significant induction of beta-galaclosida se activity was seen in PC72 incubated in either surface-reactive or naive rabbit serum. Complement (C3) was detected over the entire surface of adult PC72 and was thought to be responsible for stress-induction with naive ser a. When the immunoglobulin (Ig)G fraction of naive sera was used in isolati on, no stress-induction was seen. In contrast a two-fold increase in beta-g alactosidase activity was seen in the presence of surface-reactive IgG (SR- IgG) which recognised surface components of between 6 and 40 kDa in western blot, The belief that surface reactive IgG could induce a stress response was reinforced by analysis of hsp-16 protein expression. Cationised ferriti n was then used to assess whether stress-induction was truly a surface reac tive event; binding of cationised ferritin to the nematode surface also res ulted in two-fold induction of beta-galactosidase activity. To investigate the downstream biological effects of stress induction, worm growth and fecu ndity were measured in the presence of IgG preparations. A significant redu ction,was seen in both worm length and fecundity only when larvae were incu bated in surface-reactive IgG, compared to both naive IgG and K-medium cont rols. In conclusion, it would appear that C. elegans is a suitable model to monitor the induction of immunological stress at the level of the nematode surface coat. Given the ability of nematode surface antigens to protect th e vaccinated host in animal model systems, and the close phylogenetic relat ionships which exist between C. elegans and nematodes of medical and veteri nary importance, it is conceivable that the immunological targets in or on the surface of C. elegans warrant rapid identification.