Human Antibody Response to Longus Type IV Pilus and Study of Its Prevalence among EnterotoxigenicEscherichia coliin Bangladesh by Using Monoclonal Antibodies

Mouse monoclonal antibodies (MAbs) were derived against longus (CS20), a type IV pilus expressed by human enterotoxigenic Escherichia coli (ETEC). One MAb (ICA39) detected longus in 56 (8.5%) of 662 ETEC isolates obtained from a routine surveillance of diarrheal stools from children and adults. Five patients with diarrhea from whom longus-positive ETEC were isolated were also recruited. Of these 61 isolates, 50 were positive for other colonization factors (CFs; 61% for CFA/II and 21% for CFA/I), and 11 were negative for any of the other 8 CFs that were tested. They were either positive for the heat-stable enterotoxin (ST; n=29) or for the heat-labile enterotoxin (LT) and ST (n=32). All longus-positive ETEC were confirmed by polymerase chain reaction to harbor lngA, the longus structural pilin gene. Sera and/or fecal extracts from the patients reacted with the 22-kDa pilin polypeptide in immunoblots and ELISA. These studies show that longus is prevalent among ETEC in Bangladesh and that longus gives rise to IgA antibody responses in patients.