Subclass profile of specific IgG antibodies in rats challenged during acute and chronic primary infection with Fasciola hepatica.

The influence of a previous infection (acute and chronic) on the kinetics of the immune humoral response in rats challenged with Fasciola hepatica was studied. Two infected groups were reinfected at different times--one, at 4 weeks after primary infection (w.a.p.i.); and the other, at 11 w.a.p.i. Signs of reinfection were observed in the two challenged groups as evidenced by an increment in glutamate dehydrogenase and gamma-glutamyl transpeptidase activity after secondary infection. IgG subclass (IgG1, IgG2a, IgG2b, IgG2c) responses to F. hepatica excretory/secretory products (FhESP) differed, depending on the time of challenge infection, but no difference was observed between the reinfected groups. A predominance of the IgG1 subclass was noted in the group challenged at 4 w.a.p.i., and IgG2b and IgG2c were prominent in the group reinfected at 11 w.a.p.i. These results indicate that the presence of juvenile or adult flukes in the liver at the time of challenge seems to influence the immune response to a secondary infection.