Drosophila melanogaster S2 cells: a model system to study Chlamydia interaction with host cells

Abstract

SummaryChlamydia spp. are major causes of important human diseases, but dissecting the host-pathogen interactions has been hampered by the lack of bacterial genetics and the difficulty in carrying out forward genetic screens in mammalian hosts. RNA interference (RNAi)-based methodologies for gene inactivation can now be easily carried out in genetically tractable model hosts, such as Drosophila melanogaster, and offer a new approach to identifying host genes required for pathogenesis. We tested whether Chlamydia trachomatis infection of D. melanogaster S2 cells recapitulated critical aspects of mammalian cell infections. As in mammalian cells, C. trachomatis entry was greatly reduced by heparin and cytochalasin D. Inclusions were formed in S2 cells, acquired Golgi-derived sphingolipids, and avoided phagolysosomal fusion. Elementary body (EB) to reticulate body (RB) differentiation was observed, however, no RB to EB development or host cell killing was observed. RNAi-mediated inactivation of Rac, a Rho GTPase recently shown to be required for C. trachomatis entry in mammalian cells, inhibits C. trachomatis infection in S2 cells. We conclude that Drosophila S2 cells faithfully mimic early events in Chlamydia host cell interactions and provides a bona fide system to systematically dissect host functions important in the pathogenesis of obligate intracellular pathogens.

Use of RNA interference inDrosophilaS2 cells to identify host pathways controlling compartmentalization of an intracellular pathogen

“…Recently, Drosophila S2 cells have been established as a suitable host model for bacterial infections (11)(12)(13). These macrophage-like cells were shown to behave similarly to mammalian cells in in vitro infection assays using L. monocytogenes.…”

Genomic RNAi screening in Drosophila S2 cells: what have we learned about host–pathogen interactions?

“…are gram negative obligate intracellular bacteria of which three species cause disease in humans [47]. Whereas the human pathogen C. trichomatis can initiate infection in S2 cells, it cannot complete its lifecycle [48]. A focused screen for early events in the lifecycle included actin regulators and led to the identification of 28 factors including the Abl kinase and components of the PDGFR signaling pathway as essential for early steps in the C. trichomatis infection both in insect and mammalian cells [49].…”

Confronting physiology: how do infected flies die?

“…All assays measure survival. A. tumifaciens (Gottar et al, 2002;Leclerc et al, 2006); B. cepacia ; C. trachomatis (Elwell and Engel, 2005); E. carotovora (Basset et al, 2000;Tang et al, 2006;Acosta Muniz et al, 2007); E. cloacae (Gottar et al, 2002); E. coli (Lemaitre et al, 1995;Elrod-Erickson et al, 2000;Leclerc et al, 2006;Brennan et al, 2007;Schneider et al, 2007;Williams et al, 2007); K. pneumoniae (Benghezal et al, 2006); M. fortuitum ; M. marinum Pham et al, 2007;Schneider et al, 2007); M. smegmatis ; P. aeruginosa (Fauvarque et al, 2002;Lau et al, 2003;Erickson et al, 2004;Apidianakis et al, 2005;Avet-Rochex et al, 2005;Lee et al, 2005;…”

“…Theoretical arguments aside, however, many non-physiological microbes cause unexpectedly interesting infections in the fly. Some particularly odd examples include: Listeria monocytogenes (which has elegant temperature regulation of virulence and might not be expected to be virulent at less than 30°C), Streptococcus pneumoniae (a common inhabitant of our airways that has to be grown under CO 2 and probably never encounters the fly), and Chlamydia trachomatis (a highly co-evolved obligate intracellular pathogen) (Cheng and Portnoy, 2003;Mansfield et al, 2003;Agaisse et al, 2005;Cheng et al, 2005;Elwell and Engel, 2005;Pham et al, 2007).…”