Oral infection with enteropathogenic Escherichia coli triggers immune response and intestinal histological alterations in mice selected for their minimal acute inflammatory responses.

Enteropathogenic Escherichia coli (EPEC), a leading cause of infant diarrhea, is an important public health problem in Brazil and other developing countries. In vitro assays of bacterial adhesion to cultured cells are important tools for studying bacterial pathogenicity but do not reproduce all the events that occur in natural infections. In this study, the effects of oral infection with EPEC on mice selected for their minimal acute inflammatory response (AIR min) were evaluated. Mice were orally infected with EPEC and variations in body weight, bacterial shedding and antibody production observed. The infected animals developed seric and secretory anti-EPEC antibodies; however, neither mortality nor diarrhea was observed. Light microscopy of their intestines demonstrated histological modifications that were not present in controls. However, electron microscopy did not show bacteria attached to the intestinal epithelia to form attaching and effacing lesions, characteristic of EPEC in humans. The bacteria were detected in Peyer's patches and intestinal contents up to 5 hr post-infection. When human anti-EPEC secretory immunoglobulin A or avian immunoglobulin Y antibodies were administered to infected animals, they developed minor histological alterations compared with non-treated animals. In summary, it was found that EPEC triggers immune responses and intestinal histological alterations but does not produce evidence of diarrheal disease in mice infected by the oral route. This study of EPEC experimental infection provides a better understanding of the effects of antibodies on bacterial infections and may provide a suitable model for the design and testing of immunobiological products for active or passive immunization.

In vitro reactivity and growth inhibition of EPEC serotype O111 and STEC serotypes O111 and O157 by homologous and heterologous chicken egg yolk antibody.

IgY is a chicken egg yolk antibody which has been used for treatment and prophylaxis of gastrointestinal infections. Our aim was to verify if IgY obtained from chickens immunized with EPEC O111, STEC O111 and STEC O157 is able to show in vitro reactivity and biological activity towards the three bacteria. IgY was obtained from eggs laid before and after immunization with each bacterium. The preparations of IgY anti-EPEC O111 and anti-STEC O111 shared high reactivity detected by ELISA and growth inhibition ability towards both bacteria EPEC O111 and STEC O111. Nevertheless, the preparation of IgY anti-STEC O157 showed high reactivity and growth inhibitory effect only towards the homologous strain. Our results showing in vitro biological activity of IgY reinforce its use as an alternative for the treatment or prophylaxis of E. coli infections and encourage the development of in vivo studies for a possible future human therapeutic use.

In vitro reactivity and growth inhibition of EPEC serotype O111 and STEC serotypes O111 and O157 by homologous and heterologous chicken egg yolk antibody

IgY is a chicken egg yolk antibody which has been used for treatment and prophylaxis of gastrointestinal infections. Our aim was to verify if IgY obtained from chickens immunized with EPEC O111, STEC O111 and STEC O157 is able to show in vitro reactivity and biological activity towards the three bacteria. IgY was obtained from eggs laid before and after immunization with each bacterium. The preparations of IgY anti-EPEC O111 and anti-STEC O111 shared high reactivity detected by ELISA and growth inhibition ability towards both bacteria EPEC O111 and STEC O111. Nevertheless, the preparation of IgY anti-STEC O157 showed high reactivity and growth inhibitory effect only towards the homologous strain. Our results showing in vitro biological activity of IgY reinforce its use as an alternative for the treatment or prophylaxis of E. coli infections and encourage the development of in vivo studies for a possible future human therapeutic use

[Total and specific IgA in colostrum and milk of mothers of Natal-Rio Grande do Norte, Brasil]. / IgA secretora total e específica no colostro e leite de mães da cidade do Natal-Rio Grande do Norte, Brasil.

PURPOSE: To determine the concentration of total secretory IgA and evaluate the repertoire of IgA antibodies to enteropathogenic Escherichia coli and Shigella flexneri antigens in colostrums and milk from mothers in Natal, RN. METHODS: The sample was constituted by 22 healthy clinically women whose babies were born at public hospital in Natal, RN. To determine total secretory IgA a radial immunedifusion tecnique (Mancini et al, 1965), was employed and to detect specific antibodies, immuneenzimatic assays, ELISA was used. RESULTS: The median values of total secretory IgA concentration presented individual variations with high levels in colostrums samples, decreasing during lactation, it was observed a p < 0.001 among the samples from the first day of lactation, to the thirtieth for total IgA concentration. All the donators present in colostrum and milk specific antibodies to Escherichia coli enteropathogenic (EPEC) and Shigella flexneri with titles higer in colostrum. There was parallel and directional pattern between total IgA and IgA anti-EPEC and Shegella flexneri, during period. CONCLUSION: The concentrations of total SIgA and specific antibodies to enteropathogenic Escherichia coli and Shigella flexneri in colostrums and milk in our study do not differ from others accomplished among populations with the same social and econimic features, stressing the importance of human milk as a protector agent against pathogens.

Colostrum from healthy Brazilian women inhibits adhesion and contains IgA antibodies reactive with Shiga toxin-producing Escherichia coli.

UNLABELLED: Although Shiga toxin-producing Escherichia coli (STEC) has been isolated in Brazil, severe manifestations of the infection, such as haemorrhagic colitis and haemolytic-uraemic syndrome, are extremely rare in our population. Enteropathogenic Escherichia coli (EPEC) is the main aetiological agent of acute infantile diarrhoea in Brazil. There are many similarities between STEC and EPEC, such as the ability to produce attaching and effacing (A/E) lesions and some virulence-associated factors. Our aim was to investigate the presence of anti-STEC antibodies in healthy people living in an EPEC endemic area. Colostrum samples collected from 51 women living in low socio-economic conditions were analysed. Two STEC strains: O111:H- (Stx1) and O157:H7 (Stx2), and one EPEC strain (O111:H-) were used in the bacterial adhesion assays to HEp-2 cells, in the Stx1 and Stx2 cytotoxicity assays on Vero cells, in immunoblotting and in ELISA assays. All the samples strongly inhibited the adhesion of the three strains and contained SIgA antibodies reactive with antigens of EPEC O111:H-, STEC O111:H- and STEC O157:H7, mainly STEC and EPEC 94 kDa adhesin intimin. High titres of anti-LPS O111 antibodies were found in many samples. Nevertheless, the cytotoxic effect of both Stx1 and Stx2 on Vero cells was not neutralised by any sample. CONCLUSION: Our results suggest that Brazilian people may be exposed to Shiga toxin-producing Escherichia colimore frequently than previously thought or alternatively there may be a cross reactive immunity between enteropathogenic Escherichia coliand Shiga toxin-producing Escherichia coli.