TLR4 genetic variation is associated with inflammatory responses in Gram-positive sepsis.
OBJECTIVE
To identify important pathogen recognition receptor (PRR) pathways regulating innate immune responses and outcome in Staphylococcus aureus sepsis.


METHODS
We analysed whether candidate PRR pathway genetic variants were associated with killed S. aureus-induced cytokine responses ex vivo and performed follow-up in vitro studies. We tested the association of our top-ranked variant with cytokine responses and clinical outcomes in a prospective multicentre cohort of patients with staphylococcal sepsis.


RESULTS
An intronic TLR4 polymorphism and expression quantitative trait locus, rs1927907, was highly associated with cytokine release induced by stimulation of blood from healthy Thai subjects with S. aureus ex vivo. S. aureus did not induce TLR4-dependent NF-κB activation in transfected HEK293 cells. In monocytes, tumor necrosis factor (TNF)-α release induced by S. aureus was not blunted by a TLR4/MD-2 neutralizing antibody, but in a monocyte cell line, TNF-α was reduced by knockdown of TLR4. In Thai patients with staphylococcal sepsis, rs1927907 was associated with higher interleukin (IL)-6 and IL-8 levels as well as with respiratory failure. S. aureus-induced responses in blood were most highly correlated with responses to Gram-negative stimulants whole blood.


CONCLUSIONS
A genetic variant in TLR4 is associated with cytokine responses to S. aureus ex vivo and plasma cytokine levels and respiratory failure in staphylococcal sepsis. While S. aureus does not express lipopolysaccharide or activate TLR4 directly, the innate immune response to S. aureus does appear to be modulated by TLR4 and shares significant commonality with that induced by Gram-negative pathogens and lipopolysaccharide.
Department of Microbiology and Immunology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand; Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand. Electronic address: narisara@tropmedres.ac.
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Chantratita
Department of Microbiology and Immunology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand; Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
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Tandhavanant
Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Washington, Seattle, WA, USA.
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S
Seal
Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
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Wikraiphat
Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
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Wongsuvan
Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
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Ariyaprasert
Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
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Suntornsut
Department of Clinical Pathology, Sunpasitthiprasong Hospital, Ubon Ratchathani, Thailand.
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Teerawattanasook
Department of Clinical Pathology, Udon Thani Hospital, Udon Thani, Thailand.
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Y
Jutrakul
Department of Clinical Pathology, Khon Kaen Hospital, Khon Kaen, Thailand.
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N
Srisurat
Srinagarind Hospital, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand.
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Chaimanee
Department of Medicine, Sunpasitthiprasong Hospital, Ubon Ratchathani, Thailand.
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Mahavanakul
Department of Pediatrics, Sunpasitthiprasong Hospital, Ubon Ratchathani, Thailand.
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P
Srisamang
Department of Medicine, Udon Thani Hospital, Udon Thani, Thailand.
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Phiphitaporn
Department of Medicine, Khon Kaen Hospital, Khon Kaen, Thailand.
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Mokchai
Department of Medicine, Khon Kaen Hospital, Khon Kaen, Thailand.
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Anukunananchai
Department of Microbiology and Melioidosis Research Center, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand.
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Wongratanacheewin
Department of Medicine, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand.
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Chetchotisakd
Department of Biostatistics, University of Washington, Seattle, WA, USA.
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MJ
Emond
Department of Microbiology and Immunology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand; London School of Hygiene and Tropical Medicine, London, United Kingdom.
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SJ
Peacock
Department of Microbiology and Immunology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand; Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Washington, Seattle, WA, USA; International Respiratory and Severe Illness Center, University of Washington, Seattle, USA.
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West
D000328:Adult; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D020022:Genetic Predisposition to Disease; D014644:Genetic Variation; D006801:Humans; D007249:Inflammation / Q000235:genetics* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D018805:Sepsis / Q000382:microbiology*; D013203:Staphylococcal Infections / Q000235:genetics* / Q000382:microbiology*; D013785:Thailand; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*
D016207:Cytokines; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4
Genetic; Humans; Immunity; Sepsis; Staphylococcus