Kinetics of local and systemic immune responses to an oral cholera vaccine given alone or together with acetylcysteine

Abstract

The possibility that a mucolytic drug, i.e., acetylcysteine, given orally may enhance the gut mucosal or systemic immune response to an oral B-subunit-whole-cell (B-WC) cholera vaccine was evaluated for 40 adult Swedish volunteers, and the kinetics of the immune responses were monitored for responding volunteers. Two doses of vaccine induced similar frequencies of immunoglobulin A (IgA) and IgG antitoxin responses (80 to 90%) and vibriocidal titer increases (60 to 65%) in serum irrespective of whether the vaccine was given alone or together with 2 g of acetylcysteine. In feces the frequencies of IgA antitoxin (67%) and antibacterial (33 to 40%) antibody responses were also comparable in the two immunization groups. Six months after vaccination, IgA and IgG antitoxin as well as vibriocidal antibody titer increases in serum could still be detected in approximately 80% of initially responding vaccinees. Significantly elevated fecal antitoxin and antibacterial IgA antibody levels were found in, respectively, 50 and 43% of those volunteers who initially had responded to the vaccine. Determination of IgA antibodies in feces does not seem to offer any advantages compared to determination in serum for assessment of immune responses after immunization with inactivated cholera vaccine.

FIG. 1

Geometric mean fold increases (plus standard errors of the mean) of IgA and IgG antitoxin titers in serum and of IgA antitoxin titers/total IgA in feces after two oral doses of B-WC cholera vaccine in 18 Swedish volunteers 23 days (□) and approximately 180 (150 to 210) days (▪) after the first immunization. The numbers of volunteers responding are indicated above the bars.