Helicobacter pylori antibody profile in household members of children with H. pylori infection.

Intrafamilial spread is implicated as a major route for acquisition of Helicoobacter pylori infection. Investigating H. pylori cytotoxin-associated protein (CagA) and vacuolating toxin (VacA) antibodies within family members enabled the authors to evaluate this possibility further. Serum samples were collected prospectively from household members after their index children were diagnosed with active H. pylori infection. Serum samples were evaluated for anti-H. pylori immunoglobulin G antibody using the enzyme immunoassay (IEA) method and for H. pylori CagA and VacA antibodies with the commercially available immunoprobing Western blot kit. Ten different families participated in the study, including 10 pediatric patients and 31 household members. All patients and 28 household members (90%) were seropositive for H. pylori antibody by IEA and Western blot tests. Overall, 17 subjects (41.4%) were CagA positive, 14 (34.1%) were VacA positive, 11 (26.8%) were positive for both antibodies, and 22 (53.6%) were negative for both antibodies. A significant association in bacterial antibody profile was found between the patient index members and all household members (Cohen's kappa and Mentel-Haenszel methods). In four families, more than 66% of the household members harbored the same antibody profile, and in two families a completely different profile was observed. Moreover, a similar H. pylori antibody profile between the index patient and the mother was found in six families, and between the index patient and the father in two families. The data strongly suggest an intrafamiliar transmission for H. pylori infection.