Ha. Manjarrez-hernandez et al., Antigen detection in enteropathogenic Escherichia coli using secretory immunoglobulin A antibodies isolated from human breast milk, INFEC IMMUN, 68(9), 2000, pp. 5030-5036
Enteropathogenic Escherichia coli (EPEC) produces a characteristic attachin
g and effacing (A/E) lesion in the small intestines of infected children. T
he immune response to EPEC infection remains poorly characterized. The mole
cular targets that elicit protective immunity against EPEC disease are unkn
own. In this study protein antigens from EPEC were identified using secreto
ry immunoglobulin A (sIgA) antibodies isolated from milk from Mexican women
by Western blot analysis, Purified sIgA antibodies, which inhibit the adhe
rence of EPEC to cells, reacted to many EPEC proteins, the most prominent o
f which were intimin (a 94-kDa outer membrane protein) and two unknown prot
eins with apparent molecular masses of 80 and 70 kDa. A culture supernatant
protein of 110 kDa also reacted strongly with the sIgA antibodies. The mol
ecular size of this protein and its reactivity with specific anti-EspC anti
serum suggest that it is EPEC-secreted protein C (EspC). These EPEC surface
protein antigens were consistently recognized by all the different sIgA sa
mples obtained from 15 women. Screening of clinical isolates of various O s
erogroups from cases of severe infantile diarrhea revealed that all EPEC st
rains able to produce the A/E lesion showed expression of intimin and the 8
0- and 70-kDa proteins. Such proteins reacted strongly with the purified sI
gA pool. Moreover, nonvirulent E. coli strains were unable to generate a sI
gA response. The immunogenic capacities of the 80- and 70-kDa proteins as v
irulence antigens have not been previously reported. The strong sIgA respon
se to intimin and the 80- and 70-kDa proteins obtained in this study indica
tes that such antigens stimulate intestinal immune responses and may elicit
protective immunity against EPEC disease.