| Shigella is facultative bacilli that cause Shigellosis, or bacillary dysentery. Its lipopolysaccharide and invasion plasmid antigen proteins are the two main antigen molecules associated with bacterial virulence. There was evidence that neither clone strain nor imitative strain has virulence when expressed independently. Only when the two kinds of molecules are fully expressed simultaneously, can those strains cause ser+ of guinea pig and bacillary dysentery. McAbs targeting at various membrane components of S. flexneri2a-12 have been developed in our lab, using intact bacterium or different purified components as antigens. These antibodies include McAb 3A6, recognizing LPS type II, group 3,4 O-antigen of S. flexneri2a-12, McAb 1G8 and 2A3, only recognizing group 3,4 O-antigen of S. flexneri2a-12, and McAb 17G2, recognizing pathogenic membrane protein IpaB of S. flexneri2a-12. Can these monoclonal antibodies prevent the virulence phenotypes expressed by 5. flexneri2a-121 This is just the objective that we intended to study.In this study, we observed the influence of various McAbs on Shigella's contact hemolysis, ability to invade HeLa cells and to cause inflammation in guinea pig's eyes. At the same time, by scanning electronic microscopy, transmitting electronic microscopy and laser scanning confocal microscopy, we observed the morphological changes of HeLa cells infected by S.flexneri2a-12 and the rearrangement of actin in HeLa cells. It was found that firstly 3A6, the McAb recognizing shigella LPS type II and group 3,4 O-antigen, could effectively prevent the activity of the contact hemolysis of the S.flexneri2a-12, while 17G2, the McAb recognizing IpaB couldn't. Secondly, neither 3A6 nor 17G2 could prevent the invasion of S. Jlexneri2a-12. On the contrary, both of them promoted the invasion abilities of S. flexneri2a-12, increased the rate of the infected cells and the number of the invasive bacteria. It was also observed that the cytoskeleton of the HeLa cells was rearranged during the invasion process. Thirdly, we observed that the inflammation became more severe when guinea pig was infected with S. flexneri2a-12 pretreated with 3A6 and 17G2. Finally, anti-CD44-antibody could obviously prevent S.flexneri2a-12 from invading into the HeLa cells. These results first demonstrate that lipopolysaccharide on the surface of the Shigella may be associated with its invasion ability. We achieved newacknowledge about the role of different membrane antigens in pathogenesis and immune protection against this bacterium and thus provided important information for the development of new shigella vaccine.95 percent of infection takes place in mucosa or through mucosa, so more and more attention is paid to the mucosal immunity. To explore the mechanism of the common mucosal immunity, the homing and recirculation of the lymphocyte is becoming one of the hot spots in immunology. In earlier studies, we found that intranasal immunization could induce stronger immune responses of different mucosal sites than intraintestinal route, as well as sronger systematic immune responses. In the second part of the paper, we studyed the expression of some adhesion molecules, such as CD44, CD54, a 4 integrin and MAdCAM-1 on the surface of different lymphocytes of mouse after intragastric infection or intranasal infection by S. flexneri2a-12. Having compared with their expressions, we found that the lymphocytes in MLN and PP expressed high levels of a 4 integrin and MAdCAM-1 by 48h after intranasal infection, and the higher expression of MAdCAM-1 was found in the genital mucosae simultaneously. The result show that effector cells can effectively home to different mucosal sites and induce genital mucosal response after intranasal immunization. We also found different changes of CD44 or CD54 on the surface of the lymphocyte in different mucosal sites after intranasal infection or intraintestinal infection. This study provided useful information for the further study on the migration and the regulation of the immune cells.
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