Modulation of intestinal innate immune response by Giardia intestinalis.

HUMEN MARTIN; GRISELDA MORENO; D GONZALEZ MACIEL,; PABLO PEREZ; MARTIN RUMBO

Congreso; 1st. French-Argentinean Congress of Immunology, November 2-5, 2010. Buenos Aires, Argentina.; 2010

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";} @page Section1 {size:595.3pt 841.9pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:35.4pt; mso-footer-margin:35.4pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> Giardia intestinalis is the etiological agent of giardiasis, one of the most frequent intestinal diseases worldwide, that may present broad clinical picture from mild symptoms to severe and protracted diarrhea. The specific mechanisms of pathogenicity and the major host defenses against Giardia infection still remain unclear. In the present work, we sought to gain insight in the activation and modulation of chemokine production by intestinal mucosa upon Giardia infection, using in vitro and in vivo models. In order to evaluate the expression of chemokines such as CCL20, CXCL10 and CXCL2, human cultured enterocyte-like Caco-2 cells were apically infected with Giardia trophozoites and 4 h later, cells were harvested and RNA levels were measured by QPCR and normalized to actin. There was a nearly 9-fold increase in CCL20 expression in infected cells.  In addition, we assessed the expression in vivo of CCL20 using C57BL/6 infected mice. 5 x 107 trophozoites of Giardia intestinalis strain H7 were administrated per animal and 2 h or 7 days post-infection duodenum samples were taken and analyzed by QPCR. There was an 11-fold  increase in CCL20 expression 2 h post-infection in infected animals compared with uninfected controls. No induction was detected at 7 days post-infection, coincident with no inflammatory alterations in the mucosa. We used a reporter Caco-2 cell line harboring the luciferase gene under the control of the CCL20 promoter to evaluate the modulation of innate response by Giardia infection when co-administered with flagellin, a TLR5 ligand that is an inflammatory stimuli to intestinal epithelial cell. In this format, dose- and strain-dependent inhibition of luciferase production was evidenced. Infection of Giardia 1h previous to flagellin administration showed an even more pronounced inhibition in the reporter activity. In view of these results Giardia intestinalis triggers a transient activation of mucosal innate response but can also modulate the production of proinflammatory chemokines triggered by the activation of innate receptors.