Helicobacter pylori infection affects immune responses following vaccination of typhoid-naive us adults with attenuated salmonella typhi oral vaccine CVD 908-htrA

Background. We examined the association between Helicobacter pylori infection and the immune response following oral immunization of US adults with attenuated Salmonella Typhi vaccine CVD 908-htrA.Methods. Baseline sera from 74 volunteers without a history of typhoid fever who were immunized orally with CVD 908-htrA were tested by enzyme-linked immunosorbent assay for immunoglobin G (IgG) antibodies to H. pylori, hepatitis A antibodies (a marker of low socioeconomic status and exposure to enteric infections), and pepsinogen (PG) I and II levels (measures of gastric inflammation). IgG against S. Typhi lipopolysaccharide (LPS) O and flagella was measured before and 28 days following immunization; a ≥4-fold increase in titer from baseline constituted seroconversion.Results. Seroconversion of S. Typhi IgG LPS antibodies was significantly higher among vaccinees infected with H. pylori versus uninfected subjects: adjusted odds ratio (OR) 3.8, 95% confidence interval (CI), 1.1-12.6 (P =. 03). A low PG I:PG II ratio (<5), indicating more advanced corpus gastritis, increased the odds of seroconversion of IgG S. Typhi flagella antibody (adjusted OR 6.4, 95% CI, 1.3-31.4; P =. 02). Hepatitis A infection did not influence the immune response to CVD 908-htrA.Conclusions. H. pylori infection and gastric inflammation may enhance humoral immunity to oral attenuated S. Typhi vaccine.