Serum antibody response induced in mice after oral administration of threedifferent antigens of enterotoxigenic Escherichia coli in enteric coated microparticles

Background: Gastric digestion of these antigens plays an important role, de creasing the ability to deliver antigens to the gut-associated lymphoid tis sue. To overcome this obstacle, microencapsulated antigens from enterotoxig enic Escherichia coil (ETEC) were evaluated for oral immunization of mice. Methods: Four groups of 10 each received 3 series of 3 doses each of (1) B subunit of cholera toxin (CTB), similar to heat-labile toxin of ETEC, (2) f ormalin-killed whole cell ETEC H10407 (FK-ETEC), (3) crude preparation of c olonization factor antigen I (CFA/1), or (4) placebo. Serum antibody was me asured on day 0 and 60 by ELISA. Results: In group 1 a CTB antibody response was induced in all mice, 3 with 1:10(5) titer and 7 with 1:10(6). These antibodies neutralized cholera tox in-induced steriodogenesis of Y-1 adrenal cells. In group 2, 8 mice develop ed a whole H10407 bacteria antibody titer of 1:100, one 1:200 and one showe d no immune response. In the same group, an anti-CFA/I response was observe d in 6 mice and anti-LPS in 4 mice as determined by Western blot. All mice in group 3 showed > 1:10(4) anti-CFA/I antibody titer. Group 4 mice did not develop an immune response to any ETEC antigens. Conclusion: Microencapsulation appears to be a suitable approach for oral v accination against ETEC and Vibrio cholerae.