Local and systemic antibody response in Balb/c mice immunized with Entamoeba histolytica trophozoites.

Several immunization schedules with E. histolytica trophozoites were tested on Balb/c mice in order to induce antibody responses, both in intestinal secretions and in serum. Mice were immunized either orally, systemically, or using one of two combined schedules: the oral route followed by the systemic route (footpad), or vice versa. Each of the immunization schedules used in this project induced an anti-E. histolytica antibody response and there appears to be a correlation between the immunization route employed and the immunoglobulin isotype induced in the gut. Secretory IgA production is favored by the oral administration of trophozoites, whereas mucosal IgG appears to be enhanced by the systemic immunization route. Both schedules are effective in the induction of secretory IgA in the gut, yet higher and earlier levels of IgA appear in orally immunized mice. When systemic immunization is employed, the increase in antibody levels in the intestinal fluid is slower, and IgG is the predominant class. The combined oral/systemic routes of immunization appear to be comparably effective for the induction of local and systemic IgA and IgM antibody production. However, mice immunized first systemically and then locally produce more IgG in both compartments. Combined schedules modify the isotype pattern of antibody responses in serum and in intestinal secretions when compared with single (i.e., oral or systemic) schedules, but they do not appear to favor a secretory IgA immune response.