ÿþ<HTML><HEAD><TITLE>25º Congresso Brasileiro de Microbiologia </TITLE><link rel=STYLESHEET type=text/css href=css.css></HEAD><BODY aLink=#ff0000 bgColor=#FFFFFF leftMargin=0 link=#000000 text=#000000 topMargin=0 vLink=#000000 marginheight=0 marginwidth=0><table align=center width=700 cellpadding=0 cellspacing=0><tr><td align=left bgcolor=#cccccc valign=top width=550><font face=arial size=2><strong><font face=Verdana, Arial, Helvetica, sans-serif size=3><font size=1>25º Congresso Brasileiro de Microbiologia </font></font></strong><font face=Verdana size=1><b><br></b></font><font face=Verdana, Arial,Helvetica, sans-serif size=1><strong> </strong></font></font></td><td align=right bgcolor=#cccccc valign=top width=150><font face=arial size=2><strong><font face=Verdana, Arial, Helvetica, sans-serif size=1><font size=1>ResumoID:2420-2</font></em></font></strong></font></td></tr><tr><td colspan=2><br><br><table align=center width=700><tr><td>Área: <b>Imunologia ( Divisão E )</b><p align=justify><strong>THE ROLE OF INFLAMASSOME IN RECOGNITION OF THE INFECTION BY THE INTRACELLULAR BACTERIA <SPAN STYLE="FONT-STYLE: ITALIC;">COXIELLA BURNETII</SPAN><BR> </strong></p><p align=justify><b>Dario Simões Zamboni </b> (<i>FMRP-USP</i>); <b><u>Larissa Dias da Cunha </u></b> (<i>FMRP-USP</i>)<br><br></p><b><font size=2>Resumo</font></b><p align=justify class=tres><font size=2><span style="font-style: italic;">Coxiella burnetii</span>, the etiological agent of a severe pneumonia called Q-fever, is a Gram-negative obligate intracellular pathogen. The infection occurs via aerosols and the primary target cells are alveolar macrophages. Although <span style="font-style: italic;">Coxiella</span> is highly adapted to avoid vertebrate immune responses, the infection is readily controlled by a competent innate immune response, suggesting that appropriate responses do occur. Herein we aimed to determine if the molecular platforms composed by caspase-1 and specific Nod-like receptors, so called inflammasome, play a role in recognition and restriction of <span style="font-style: italic;">C. burnetii </span>infection. ELISA essays revealed that bone marrow-derived macrophages infected with <span style="font-style: italic;">C. burnetii</span> fail to secrete IL-1<span style="font-family: Symbol;"><span style="font-family: Symbol;">B</span></span>, a cytokine known to be secreted in a caspase-1-dependent pathway. In addition, we did not detect caspase-1 activation by western blot. Alveolar and bone marrow-derived macrophages deficient for caspase-1 do not fail to control replicative vacuole formation and bacterial multiplication, as determined by real time PCR and estimative of large parasitophorous vacuole formation. To investigate whether the absence of caspase-1 activation was due to a subversion of macrophages functions by <span style="font-style: italic;">Coxiella</span> we performed co-infections with <span style="font-style: italic;">Coxiella</span> and <span style="font-style: italic;">Legionella pneumophila</span>, a pathogen known to trigger caspase-1 activation. The activation of caspase-1 and IL-1<span style="font-family: Symbol;">B</span> secretion in response to <span style="font-style: italic;">Legionella</span>&nbsp; were not&nbsp; blocked by the presence of <span style="font-style: italic;">Coxiella</span>. Furthermore, <span style="font-style: italic;">Coxiella</span> does not seem to directly inhibit caspase-1, as the bacteria fail to block caspase-1 autocatalytic activity in a HEK293 cell expression system (transfected with vectors encoding pro-caspase-1). In addition, our data suggests that the bacterium does not interfere with inflammasome activation in response to LPS + ATP, which are potent activators of the inflammasome. Interestingly, cells infected with <span style="font-style: italic;">Coxiella </span>and treated with ATP do not activate caspase-1. In contrast, macrophages treated with heat killed <span style="font-style: italic;">Coxiella</span> + ATP trigger a robust inflammasome response. Regardless to the participation of caspase-1, we found that caspase-3 was required for innate immune responses, as macrophages from caspase-3-/- mice were highly susceptible to <span style="font-style: italic;">Coxiella</span> infection. In conclusion, we found that whereas caspase-3 is unequivocally required to generation of appropriate responses against <span style="font-style: italic;">Coxiella</span>, the caspase-1 inflammasome seems to play no role in the recognition and control of <span style="font-style: italic;">Coxiella</span> infection. </font></p><br><b>Palavras-chave: </b>&nbsp;Coxiella burnetii, infammasome, caspase-1, caspase-3</td></tr></table></tr></td></table></body></html>