Concanavalin A reduces liver collagen accumulation in murine schistosomiasis

Mice infected with Schistosoma mansoni develop hepatic fibrosis associated with enhanced collagen synthesis that out-paces induced collagenase activity. Administration of one dose of concanavalin A [Con A (200 micrograms)] by i.p. injection to mice at 5 or 6 weeks after infection with 50 S. mansoni cercariae decreased liver collagen content by 50% compared to levels in control-infected mice injected with either homologous immunoglobulin (200 micrograms) or phosphate-buffered saline; additional doses of Con A had no further effect. The decrease in collagen content could not be attributed to either decreased egg deposition in the liver or inhibition of liver collagen synthesis, but was coincident with a greater solubility of granulomas. Collagen contents of skin and tail were unaffected. The relative solubilities of liver collagen in 8 M urea: 10 mM dithiothreitol were greater in treated animals as compared to controls. However, the amounts of collagen solubilized were similar in both sets of animals, since the total collagen content of treated mice was 50% of the controls. A possible explanation for these results is that much of the synthesized collagen does not accumulate in treated animals, whereas it does accumulate in controls. Peak collagenase and neutral protease activities occurred at 7 weeks postinfection in treated animals, and were 2-fold greater than in controls. Similar effects were observed when succinylated Con A was administered. The results suggest that Con A may modulate host-immune responses influencing fibrogenesis in hepatic murine schistosomiasis.