Differential use of TLR2 and TLR9 in the regulation of immune responses during the infection with Trypanosoma cruzi.

PLoS One. 2013 May 1;8(5):e63100.

Gravina HD, Antonelli L, Gazzinelli RT, Ropert C.

Departamento de Bioquímica e Imunologia, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.


Pathogens express ligands for several TLRs that may play a role in the induction or control of the inflammatory response during infection. Concerning Trypanosoma cruzi, the agent of Chagas disease, we have previously characterized glycosylphosphatidylinositol (GPI) anchored mucin-like glycoproteins (tGPI-mucin) and unmethylated CpG DNA sequences as TLR2 and TLR9 agonists, respectively. Here we sought to determine how these TLRs may modulate the inflammatory response in the following cell populations: F4/80(+)CD11b(+) (macrophages), F4/80(low)CD11b(+) (monocytes) and MHCII(+)CD11c(high) (dendritic cells). For this purpose, TLR2(-/-) and TLR9(-/-) mice were infected with Y strain of T. cruzi and different immunological parameters were evaluated. According to our previous data, a crucial role of TLR9 was evidenced in the establishment of Th1 response, whereas TLR2 appeared to act as immunoregulator in the early stage of infection. More precisely, we demonstrated here that TLR2 was mainly used by F4/80(+)CD11b(+) cells for the production of TNF-α. In the absence of TLR2, an increased production of IL-12/IL-23p40 and IFN-γ was noted suggesting that TLR2 negatively controls the Th1 response. In contrast, TLR9 was committed to IL-12/IL-23p40 production by MHCII(+)CD11c(high) cells that constitute the main source of IL-12/IL-23p40 during infection. Importantly, a down-regulation of TLR9 response was observed in F4/80(+)CD11b(+) and F4/80(low)CD11b(+) populations that correlated with the decreased TLR9 expression level in these cells. Interestingly, these cells recovered their capacity to respond to TLR9 agonist when MHCII(+)CD11c(high) cells were impeded from producing IL-12/IL-23p40, thereby indicating possible cross-talk between these populations. The differential use of TLR2 and TLR9 by the immune cells during the acute phase of the infection explains why TLR9- but not TLR2-deficient mice are susceptible to T. cruzi infection.

PMID: 23650544



Model of cooperation between immune cells that use different Toll-Like Receptors (TLRs) during infection. During the infection with Trypanosome cruzi, TLR9 is the main receptor involved in the production of IL-12 by DCs, while TLR2 is responsible for TNF-α production by macrophages. In addition, TLR2 plays in DCs an immunoregulatory role by controlling the TLR9 activity in these cells. Such findings may directly impact on the use of TLR agonists in immunotherapy or as adjuvant in vaccines.

Catherine ROPERT-1

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