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MyD88 dependent signaling contributes to protective host defense against Burkholderia pseudomallei.

Wiersinga WJ, Wieland CW, Roelofs JJ, van der Poll T - PLoS ONE (2008)

Bottom Line: First, we found that MyD88, but not TRIF, deficient whole blood leukocytes released less TNFalpha upon stimulation with B. pseudomallei compared to wild-type (WT) cells.The decreased bacterial clearance capacity of MyD88 KO mice was accompanied by a markedly reduced early pulmonary neutrophil recruitment and a diminished activation of neutrophils after infection with B. pseudomallei.MyD88 dependent signaling, but not TRIF dependent signaling, contributes to a protective host response against B. pseudomallei at least in part by causing early neutrophil recruitment towards the primary site of infection.

View Article: PubMed Central - PubMed

Affiliation: Center for Infection and Immunity Amsterdam (CINIMA), Academic Medical Center, Amsterdam, The Netherlands. w.j.wiersinga@amc.uva.nl

ABSTRACT

Background: Toll-like receptors (TLRs) have a central role in the recognition of pathogens and the initiation of the innate immune response. Myeloid differentiation primary-response gene 88 (MyD88) and TIR-domain-containing adaptor protein inducing IFNbeta (TRIF) are regarded as the key signaling adaptor proteins for TLRs. Melioidosis, which is endemic in SE-Asia, is a severe infection caused by the gram-negative bacterium Burkholderia pseudomallei. We here aimed to characterize the role of MyD88 and TRIF in host defense against melioidosis.

Methodology and principal findings: First, we found that MyD88, but not TRIF, deficient whole blood leukocytes released less TNFalpha upon stimulation with B. pseudomallei compared to wild-type (WT) cells. Thereafter we inoculated MyD88 knock-out (KO), TRIF mutant and WT mice intranasally with B. pseudomallei and found that MyD88 KO, but not TRIF mutant mice demonstrated a strongly accelerated lethality, which was accompanied by significantly increased bacterial loads in lungs, liver and blood, and grossly enhanced liver damage compared to WT mice. The decreased bacterial clearance capacity of MyD88 KO mice was accompanied by a markedly reduced early pulmonary neutrophil recruitment and a diminished activation of neutrophils after infection with B. pseudomallei. MyD88 KO leukocytes displayed an unaltered capacity to phagocytose and kill B. pseudomallei in vitro.

Conclusions: MyD88 dependent signaling, but not TRIF dependent signaling, contributes to a protective host response against B. pseudomallei at least in part by causing early neutrophil recruitment towards the primary site of infection.

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No difference in B. pseudomallei phagocytosis or killing capacity between WT and MyD88 KO cells.(A) Peripheral blood neutrophils were incubated at 37°C with CFSE-labeled growth-arrested B. pseudomallei (1×107 CFU/ml) after which time-dependent phagocytosis was quantified; 1×104 neutrophils were analysed per sample (see Methods section). (B) Killing capacity of peritoneal macrophages are shown as percentage of killed B. pseudomallei compared to t = 0. Data are mean±SEM; n = 5 per mouse strain. Open rounds represent WT cells, while black squares represent MyD88 KO mice; ns denotes not significant.
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pone-0003494-g007: No difference in B. pseudomallei phagocytosis or killing capacity between WT and MyD88 KO cells.(A) Peripheral blood neutrophils were incubated at 37°C with CFSE-labeled growth-arrested B. pseudomallei (1×107 CFU/ml) after which time-dependent phagocytosis was quantified; 1×104 neutrophils were analysed per sample (see Methods section). (B) Killing capacity of peritoneal macrophages are shown as percentage of killed B. pseudomallei compared to t = 0. Data are mean±SEM; n = 5 per mouse strain. Open rounds represent WT cells, while black squares represent MyD88 KO mice; ns denotes not significant.

Mentions: The experiments described above established the key role of MyD88 in the antibacterial defense towards B. pseudomallei infection. MyD88 has been described to play an important role in phagocytosis and killing of invading bacteria [26] and since B. pseudomallei is a facultative intracellular bacterium [13], [29]–[31] we next determined whether MyD88 contributes to phagocytosis and/or killing of B. pseudomallei. Interstingly, we found that MyD88 deficient neutrophils demonstrated an unaltered capacity to phagocytose B. pseudomallei (Fig. 7A). In addition, no difference in the killing capacity between WT and MyD88 deficient macrophages was observed (Fig. 7B).


MyD88 dependent signaling contributes to protective host defense against Burkholderia pseudomallei.

Wiersinga WJ, Wieland CW, Roelofs JJ, van der Poll T - PLoS ONE (2008)

No difference in B. pseudomallei phagocytosis or killing capacity between WT and MyD88 KO cells.(A) Peripheral blood neutrophils were incubated at 37°C with CFSE-labeled growth-arrested B. pseudomallei (1×107 CFU/ml) after which time-dependent phagocytosis was quantified; 1×104 neutrophils were analysed per sample (see Methods section). (B) Killing capacity of peritoneal macrophages are shown as percentage of killed B. pseudomallei compared to t = 0. Data are mean±SEM; n = 5 per mouse strain. Open rounds represent WT cells, while black squares represent MyD88 KO mice; ns denotes not significant.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2566818&req=5

pone-0003494-g007: No difference in B. pseudomallei phagocytosis or killing capacity between WT and MyD88 KO cells.(A) Peripheral blood neutrophils were incubated at 37°C with CFSE-labeled growth-arrested B. pseudomallei (1×107 CFU/ml) after which time-dependent phagocytosis was quantified; 1×104 neutrophils were analysed per sample (see Methods section). (B) Killing capacity of peritoneal macrophages are shown as percentage of killed B. pseudomallei compared to t = 0. Data are mean±SEM; n = 5 per mouse strain. Open rounds represent WT cells, while black squares represent MyD88 KO mice; ns denotes not significant.
Mentions: The experiments described above established the key role of MyD88 in the antibacterial defense towards B. pseudomallei infection. MyD88 has been described to play an important role in phagocytosis and killing of invading bacteria [26] and since B. pseudomallei is a facultative intracellular bacterium [13], [29]–[31] we next determined whether MyD88 contributes to phagocytosis and/or killing of B. pseudomallei. Interstingly, we found that MyD88 deficient neutrophils demonstrated an unaltered capacity to phagocytose B. pseudomallei (Fig. 7A). In addition, no difference in the killing capacity between WT and MyD88 deficient macrophages was observed (Fig. 7B).

Bottom Line: First, we found that MyD88, but not TRIF, deficient whole blood leukocytes released less TNFalpha upon stimulation with B. pseudomallei compared to wild-type (WT) cells.The decreased bacterial clearance capacity of MyD88 KO mice was accompanied by a markedly reduced early pulmonary neutrophil recruitment and a diminished activation of neutrophils after infection with B. pseudomallei.MyD88 dependent signaling, but not TRIF dependent signaling, contributes to a protective host response against B. pseudomallei at least in part by causing early neutrophil recruitment towards the primary site of infection.

View Article: PubMed Central - PubMed

Affiliation: Center for Infection and Immunity Amsterdam (CINIMA), Academic Medical Center, Amsterdam, The Netherlands. w.j.wiersinga@amc.uva.nl

ABSTRACT

Background: Toll-like receptors (TLRs) have a central role in the recognition of pathogens and the initiation of the innate immune response. Myeloid differentiation primary-response gene 88 (MyD88) and TIR-domain-containing adaptor protein inducing IFNbeta (TRIF) are regarded as the key signaling adaptor proteins for TLRs. Melioidosis, which is endemic in SE-Asia, is a severe infection caused by the gram-negative bacterium Burkholderia pseudomallei. We here aimed to characterize the role of MyD88 and TRIF in host defense against melioidosis.

Methodology and principal findings: First, we found that MyD88, but not TRIF, deficient whole blood leukocytes released less TNFalpha upon stimulation with B. pseudomallei compared to wild-type (WT) cells. Thereafter we inoculated MyD88 knock-out (KO), TRIF mutant and WT mice intranasally with B. pseudomallei and found that MyD88 KO, but not TRIF mutant mice demonstrated a strongly accelerated lethality, which was accompanied by significantly increased bacterial loads in lungs, liver and blood, and grossly enhanced liver damage compared to WT mice. The decreased bacterial clearance capacity of MyD88 KO mice was accompanied by a markedly reduced early pulmonary neutrophil recruitment and a diminished activation of neutrophils after infection with B. pseudomallei. MyD88 KO leukocytes displayed an unaltered capacity to phagocytose and kill B. pseudomallei in vitro.

Conclusions: MyD88 dependent signaling, but not TRIF dependent signaling, contributes to a protective host response against B. pseudomallei at least in part by causing early neutrophil recruitment towards the primary site of infection.

Show MeSH
Related in: MedlinePlus