In vitro effect of immune sera on the invasion of Trichinella spiralis infective larvae into intestinal epithelial cells and their development.

Objective To observe the effect of sera from mice immunized with excretory-secretory (ES) antigen or surface antigen of Trichinella spiralis larvae on the invasion of intestinal epithelial cells in vitro by the larvae and on their development. Methods HCT-8 cells grown to confluence were overlaid with the larvae suspended in semisolid medium (RPMI 1640 medium +1.75% agarose), and the larvae were then observed by using an inverted microscope after being incubated at 37 ℃ under 5% CO2 for 12、 24、 36、 72、 96 h. The larval development and its invasion into intestinal epithelial cells were observed under inverted microscope after 15 min when HCT-8 cells were overlaid with the larvae suspended in semisolid medium supplemented with immune sera. Finally, the 1st stage and 2nd～4th stage larvae were observed and enumerated by indirect fluorescent antibody test (IFAT) after 36 h incubation. Results When the larvae were cultured in semisolid medium, they invaded the HCT-8 cell monolayer and molted 1-2 times at 36 h to 72 h of culture. Early adult was observed at 96 h of culture. Cephalic caps on larvae were found at 15 min of culture when the larvae were cultured with medium containing immune sera, but the caps were not observed on those cultured with sera of normal mice or without sera. And the larvae with cephalic caps did not invade the cell monolayer. When the larvae were cultured with immune sera for 36 h, the percentage of 2nd～4th stage larvae (2.25%, 2.20%) were significantly lower than that of those cultured in normal sera (24.7%) (P0.05). Conclusion The sera from mice immunized with excretorysecretory antigen or surface antigen of T. spiralis larvae prevent the invasion of the larvae into intestinal epithelial cells in vitro and impede the development (ecdysis) of the larvae.