AbstractsBiology & Animal Science

The innate immune response to pathogens plays important roles to limit early infection and initiate subsequent adaptive immune mechanisms. Innate recognition of microbes are initiated by pattern recognition receptors (PRRs), germline-encoded receptors which are well known to initiate inflammatory processes upon activation. Toll-like receptors (TLRs) are a large class of PRRs, and have recently been described to also be capable of inducing anti-inflammatory responses. TLR2 activation by Staphylococcus aureus peptidoglycan preparations has been shown to induce the production of the anti-inflammatory cytokine IL-10 in human peripheral blood mononuclear cells (PBMCs). Previous work in our laboratory has shown that the pro- and anti-inflammatory responses elicited by S. aureus community isolates can be uncoupled mechanistically. We hypothesized that these two responses are resultant from two distinct sets of ligands on the S. aureus cell wall. S. aureus community isolates were enzymatically digested to prepare staphylococcal cell walls. Size-exclusion chromatography and ion-exchange chromatography were used to fractionate cell wall preparations by size and charge, and fractions of interest were identified by assaying pro- and anti-inflammatory cytokine production following ex vivo stimulation of human PBMCs. We found that biochemical separation was able to enrich fractions of cell wall components in IL-10-inducing capacity. Through proteomic analyses of these fractions, proteins that were dependent on Sortase A for cell wall anchoring were identified, and Sortase A was found to be indispensable for IL-10 induction. Additionally, fusion proteins linking the extracellular domains of TLR2, 1, 6, and 10 with human IgG1 Fc domains were generated as tools to purify TLR2 ligands from complex ligand mixtures by affinity chromatography. Anti-inflammatory TLR2 ligands, once found, can be used as templates for the development of novel immunomodulatory strategies. La réponse immunitaire innée joue un rôle important pour circonscrire rapidement la progression d'une infection causée par un pathogène et pour enclencher les mécanismes de la réponse immune adaptative. La reconnaissance des microbes par la réponse innée est médiée par les récepteurs de reconnaissance de motifs moléculaires (PRR), des récepteurs codés par les cellules germinales reconnus pour induire de l'inflammation lorsqu'ils sont activés. Les récepteurs de type Toll (TLR) sont une classe de PRR pouvant aussi induire une réponse anti-inflammatoire. Il a été démontré que l'activation de TLR2 par des préparations de peptidoglycane provenant de Staphylococcus aureus pouvait induire la production d'une cytokine anti-inflammatoire, l'interleukine-10 (IL-10), par les cellules mononuclées du sang périphérique (PBMC). Les précédents travaux de notre laboratoire ont démontré que les réponses pro- et anti-inflammatoires induites par des souches sauvages de S. aureus provenant d'individus porteurs ne sont pas liées par un mécanisme commun. Nous avons donc émis l'hypothèse… Advisors/Committee Members: Joaquin Madrenas (Internal/Supervisor).