Intestinal immune responses in patients infected with enterotoxigenic Escherichia coli and in vaccinees

Immune responses against enterotoxigenic Escherichia coli (ETEC) were exami ned in Bangladeshi adults with naturally acquired disease and compared to r esponses in age-matched Bangladeshi volunteers who had been orally immunize d with a vaccine consisting of inactivated ETEC bacteria expressing differe nt colonization factor antigens (CFs) and the B subunit of cholera toxin, B cell responses in duodenal biopsy samples, feces, intestinal washings, and blood were determined. Because most of the patients included in the study were infected with ETEC expressing CS5, immune responses to this CF were st udied most extensively. Vaccines and patients had comparable B-cell respons es against this antigen in the duodenum: the median numbers of antibody-sec reting cells (ASC) were 3,300 immunoglobulin A (IgA) ASC/10(7) mononuclear cells (MNC) in the patient group (n = 8) and 1,200 IgA ASC/10(7) MNC in the vaccinees (n = 13) (not a significant difference). Similarly; no statistic ally significant differences were seen in the levels of duodenal B cells di rected against enterotoxin among vaccinees and patients, A comparison of th e capacities of the various methods used to assess mucosal immune responses revealed a correlation between numbers of circulating B cells and antibody levels in saponin extracts of duodenal biopsy samples (r = 0.58; n = 13; P = 0.04) after vaccination. However, no correlation was seen between blood IgA ASC and duodenal IgA ASC after two doses of vaccine, Still, a correlati on between numbers of CF-specific B cells in blood sampled from patients ea rly during infection and numbers of duodenal B cells collected 1 week later was apparent (r = 0.70; n = 10; P = 0.03).