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Infection and Immunity, September 2000, p. 5030-5036, Vol. 68, No. 9
Departamento de Salud Publica, Facultad de
Medicina, Universidad Nacional Autonoma de Mexico, Mexico D.F.
04510, Mexico
Received 24 February 2000/Returned for modification 2 April
2000/Accepted 14 June 2000
Enteropathogenic Escherichia coli (EPEC) produces a
characteristic attaching and effacing (A/E) lesion in the small
intestines of infected children. The immune response to EPEC infection
remains poorly characterized. The molecular targets that elicit
protective immunity against EPEC disease are unknown. In this study
protein antigens from EPEC were identified using secretory
immunoglobulin A (sIgA) antibodies isolated from milk from Mexican
women by Western blot analysis. Purified sIgA antibodies, which inhibit
the adherence of EPEC to cells, reacted to many EPEC proteins, the most
prominent of which were intimin (a 94-kDa outer membrane protein) and
two unknown proteins with apparent molecular masses of 80 and 70 kDa. A
culture supernatant protein of 110 kDa also reacted strongly with the
sIgA antibodies. The molecular size of this protein and its reactivity
with specific anti-EspC antiserum suggest that it is EPEC-secreted
protein C (EspC). These EPEC surface protein antigens were consistently
recognized by all the different sIgA samples obtained from 15 women.
Screening of clinical isolates of various O serogroups from cases of
severe infantile diarrhea revealed that all EPEC strains able to
produce the A/E lesion showed expression of intimin and the 80- and
70-kDa proteins. Such proteins reacted strongly with the purified sIgA
pool. Moreover, nonvirulent E. coli strains were unable to
generate a sIgA response. The immunogenic capacities of the 80- and
70-kDa proteins as virulence antigens have not been previously
reported. The strong sIgA response to intimin and the 80- and 70-kDa
proteins obtained in this study indicates that such antigens stimulate
intestinal immune responses and may elicit protective immunity against
EPEC disease.
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Antigen Detection in Enteropathogenic
Escherichia coli Using Secretory Immunoglobulin A Antibodies
Isolated from Human Breast Milk
*
Corresponding author. Mailing address: Apartado Postal
70-443, Mexico D.F. 04510, Mexico. Phone: (525) 616-1162 or 550-7577. Fax: (525) 616-1616. E-mail: acq{at}servidor.unam.mx.
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