Cholera toxin B stimulates systemic neutralizing antibodies after intranasal co-immunization with measles virus

An efficient mucosal vaccination has a number of obvious advantages over invasive routes of immunization. The immune response to measles virus (MV) was investigated after intranasal and intragastric co-immunization of mice with cholera toxin B (CTB) as an adjuvant. High titres of virus-specific IgG antibodies and a transient IgA response were detected in the sera after intranasal but not after intragastric immunization when CTB was used. In the presence of CTB, higher titres were reached with less antigen and fewer intranasal boosts. Neutralizing antibodies were found in all animals only after co-immunization with MV and CTB. In the nasal wash and the saliva, IgG and IgA titres were significant only in the MV plus CTB groups; IgG levels were comparable to those found after intraperitoneal (i.p.) immunization with complete Freund's adjuvant. Specific IgA was detected in the mucosal fluids only after intranasal immunization with MV plus CTB but not after i.p. or intragastric immunization. The antibody response consisted of 99% IgG1 after MV immunization. In the CTB groups 10% IgG2b and 1% IgG2a were detected in addition to the predominant IgG1 antibodies.