No abstract

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 (AIRmin) 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 postinfection. 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.

No abstract

RESUMO BORDENALLI, M.A.Efeito da associação da sílica SBA-15 a antígenos de Salmonella na imunização oral de camundongos selecionados para alta e baixa produção de anticorpos. 2016. 67 f. Dissertação de Mestrado (Biotecnologia).

Different concentrations (w/w) of diphtheria anatoxin (D-ANA) were encapsulated into SBA-15 ordered mesoporous silica [1], which is composed by micropores (diameter less than 2 nm), mesopores (mean diameter of 10 nm) and macropores (diameter higher than 50 nm). The encapsulation yield of the antigen diluted in phosphate-buffered saline (PBS) solution inside the silica, after a drying process, was determined by nitrogen adsorption isotherm (NAI), which provided BET surface area and the BJH pore size distribution. These results indicated that for a mass ratio of 5SBA-15:1ANA all mesopores are filled with the antigen, suggesting that it is the optimal concentration of D-ANA into SBA-15. Furthermore, the NAI results revealed that the micropores and mesopores are also filled by PBS. Analyzing the SAXS data, simulated by a theoretical model, which included form and structure factors [2], we concluded that D-ANA is inside the mesopores and that the mass ratio of 5SBA-15:1ANA is excessive, indicating the presence of D-ANA also in the macropore region. Transmission Electron Microscopy (TEM) images further confirmed these latter results. In-situ SAXS measurements of D-ANA release from the silica matrix were performed in mimetic intestine fluid. Dynamic Light Scattering (DLS) obtained from D-ANA in PBS showed that the antigen did not aggregate and hydrodynamic particle sizes between 5 to 10 nm were observed, which is also consistent with the ability of D-ANA to enter the mesopores. X-ray absorption spectroscopy with X-ray microscopy data at the carbon K-edge revealed that the D-ANA is distributed homogeneously in all the silica particles. The thermal stability of D-ANA increased when encapsulated inside SBA-15, as determined by Thermogravimetry (TG). The immunogenic complex D-ANA in the SBA-15 vehicle will be tested in mice in order to check the production of antibodies, regarding the exceptional adjuvant protecting characteristics of .