Single nucleotide polymorphisms in TLR9 are highly associated with susceptibility to bacterial meningitis in children.
BACKGROUND
Bacterial meningitis (BM) is a severe infection mainly caused by Streptococcus pneumoniae and Neisseria meningitidis (NM). However, genetically determined susceptibility to develop severe infections by these microorganisms is variable between individuals. Toll-like receptor 9 (TLR9) recognizes bacterial DNA leading to intracellular inflammatory signaling. Single nucleotide polymorphisms (SNPs) within the TLR9 gene are associated with susceptibility to several diseases, no such association with meningitis has been described.


METHODS
We studied the role of TLR9 SNPs in host defense against BM. Two TLR9 SNPs and 4 TLR9 haplotypes were determined in 472 survivors of BM and compared to 392 healthy controls.


RESULTS
Carriage of the TLR9+2848-A mutant was significantly decreased in meningococcal meningitis (MM) patients compared with controls (p: .0098, odds ratio [OR]: .6, 95% confidence interval [CI]: .4-.9). TLR9 haplotype I was associated with an increased susceptibility to MM (p: .0237, OR 1.3, 95% CI: 1.0-1.5). In silico analysis shows a very strong immunoinhibitory potential for DNA of NM upon recognition by TLR9 (CpG index of -106.8).


CONCLUSIONS
We report an association of TLR9 SNPs with susceptibility to BM, specifically MM indicating a protective effect for the TLR9+2848-A allele. We hypothesize that the TLR9+2848-A mutant results in an up-regulation of TLR9 induced immune response compensating the strong inhibitory potential of NM CpG DNA.
Department of Pathology, Laboratory for Immunogenetics, VU University Medical Center, Amsterdam, The Netherlands.
Marieke S
MS
Sanders
Gijs Th J
GT
van Well
Sander
S
Ouburg
Patric S J
PS
Lundberg
A Marceline
AM
van Furth
Servaas A
SA
Morré
D000293:Adolescent; D000328:Adult; D002648:Child; D004198:Disease Susceptibility; D005787:Gene Frequency; D006239:Haplotypes; D006801:Humans; D008585:Meningitis, Meningococcal / Q000235:genetics* / Q000276:immunology; D008586:Meningitis, Pneumococcal / Q000235:genetics* / Q000276:immunology; D020641:Polymorphism, Single Nucleotide; D051217:Toll-Like Receptor 9 / Q000235:genetics* / Q000276:immunology
C495371:TLR9 protein, human; D051217:Toll-Like Receptor 9