Antibody responses in the lower respiratory tract and male urogenital tract in humans after nasal and oral vaccination with cholera toxin B subunit

Nasal vaccine delivery is superior to oral delivery in inducing specific im munoglobulin A (IgA) and IgG antibody responses in the upper respiratory tr act. Although an antibody response in the nasal passages is important in pr otecting against primary colonization with lung pathogens, antibodies in th e lungs are usually required as well. We immunized 15 male volunteers twice nasally or orally with cholera toxin B subunit (CTB) and determined the sp ecific antibody levels in serum, bronchoalveolar lavage (BAL) fluid, and ur ine before and 2 weeks after immunization, Nasal immunization induced fivef old increases in the levels of specific IgA antibodies in BAL fluid of most volunteers, whereas there were no significant specific IgA responses after oral immunization, The specific IgG antibody level increased eightfold in BAL fluid in the nasally vaccinated subjects, and the major part of IgG had most probably been transferred from serum. Since the specific IgG response in serum was lower in the individuals vaccinated orally, the IgG response in BAL fluid in this group was also lower and not significant, In conclusio n, nasal immunization is also preferable to the oral route when vaccinating against lower respiratory tract infections, and a systemic immune response is considerably more important in the lower than in the upper respiratory tract. Moreover, both nasal and oral immunizations were able to stimulate 6 - to 10-fold specific IgA and IgG responses in urine in about half of the i ndividuals, which indicates that distant mucosal vaccination might be used to prevent adhesion of pathogens to the urogenital tract.