Human antibody response to longus type IV pilus and study of its prevalence among enterotoxigenic Escherichia coli in 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.