CLOSTRIDIOIDES DIFFICILE UPTAKE BY HUMAN MACROPHAGES OCCURS IN A SLAMF1-INDEPENDENT MANNER

BARBERO ANGELA MARIA; HERNANDEZ DEL PINO RODRIGO EMANUEL; ESPAÑOL LAUREANO; MORRO LORENZO; MACHAIN MONICA; FUENTES FEDERICO; BARRIONUEVO PAULA; PASQUINELLI VIRGINIA

Congreso; Reunión Conjunta SAIC, SAI, AAFE, NANOMED-AR; 2021

Sociedad Argentina de Inmunología

C. difficile (CD), a Gram+ spore-forming anaerobic bacteria, is themajor cause of nosocomial infectious diarrhea that generally developsafter antibiotic treatment. SLAMF1 (Signaling LymphocyticActivation Molecule) is expressed on macrophages and triggers notonly phagosome-related functions, but can also recognize and internalizedifferent pathogens. CD components regulate macrophagesfunctions and both toxins and spores invade host cells. However,the endocytosis of the bacteria has not been explored. Here, weaddress the internalization of CD and the role of SLAMF1 duringthis process.Monocyte-derived macrophages from healthy donors were culturedin the presence or absence of CD (NAP1/BI/027 strain) inactivatedby heat or formalin treatment (CDH or CDF). For some experimentsCD was coupled with FITC and an agonistic antibody for SLAMF1was added to the cell culture.Our results show that SLAMF1 expression is not modulated on humanmacrophages surface by either CDH or CDF, even in the presenceof increasing amounts of bacteria as shown by flow cytometry.Biochemical assays were conducted and SLAMF1 detection witha specific antibody indicated that there is no interaction betweenSLAMF1 and CDH or CDF. Nevertheless, we did detect interactionof macrophages with CD. SLAMF1 is also a costimulatory molecule,but SLAMF1 costimulation through an agonistic antibody had noeffect on the CD-macrophage interaction as measured by flow cytometryand fluorescence microscopy. Moreover, most of the interactingmacrophages were SLAMF1 negative. Finally, we confirmedintracellular localization of C. difficile in macrophages and a partialcolocalization with LAMP2 by confocal microscopy.In conclusion, SLAMF1 does not promote the interaction betweenhuman macrophages and C. difficile and does not participate in theinternalization process of the bacterium. Further studies are neededto elucidate the molecules involved in macrophage entry mechanismsof C. difficile.