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TLR9 polymorphisms are associated with altered IFN-gamma levels in children with cerebral malaria.

ABSTRACT: Toll-like receptor (TLR) polymorphisms have been associated with disease severity in malaria infection, but mechanisms for this association have not been characterized. The TLR2, 4, and 9 single nucleotide polymorphism (SNP) frequencies and serum interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) levels were assessed in Ugandan children with cerebral malaria (CM, N = 65) and uncomplicated malaria (UM, N = 52). The TLR9 C allele at -1237 and G allele at 1174 were strongly linked, and among children with CM, those with the C allele at -1237 or the G allele at 1174 had higher levels of IFN-gamma than those without these alleles (P = 0.03 and 0.008, respectively). The TLR9 SNPs were not associated with altered IFN-gamma levels in children with UM or altered TNF-alpha levels in either group. We present the first human data that TLR SNPs are associated with altered cytokine production in parasitic infection.

SUBMITTER: Sam-Agudu NA

PROVIDER: S-EPMC2844552 | biostudies-literature | 2010 Apr

REPOSITORIES: biostudies-literature

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TLR9 polymorphisms are associated with altered IFN-gamma levels in children with cerebral malaria.

Sam-Agudu Nadia A NA Greene Jennifer A JA Opoka Robert O RO Kazura James W JW Boivin Michael J MJ Zimmerman Peter A PA Riedesel Melissa A MA Bergemann Tracy L TL Schimmenti Lisa A LA John Chandy C CC

The American journal of tropical medicine and hygiene 20100401 4

Toll-like receptor (TLR) polymorphisms have been associated with disease severity in malaria infection, but mechanisms for this association have not been characterized. The TLR2, 4, and 9 single nucleotide polymorphism (SNP) frequencies and serum interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) levels were assessed in Ugandan children with cerebral malaria (CM, N = 65) and uncomplicated malaria (UM, N = 52). The TLR9 C allele at -1237 and G allele at 1174 were strongly li ...[more]

PMID: 20348497

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Project description:BACKGROUND: Cerebral malaria (CM) is the most severe outcome of Plasmodium falciparum infection and a major cause of death in children from 2 to 4 years of age. A hospital based study in Ghana showed that P. falciparum induces eosinophilia and found a significantly higher serum level of eosinophil cationic protein (ECP) in CM patients than in uncomplicated malaria (UM) and severe malaria anemia (SA) patients. Single nucleotide polymorphisms (SNPs) have been described in the ECP encoding-gene (RNASE3) of which the c.371G>C polymorphism (rs2073342) results in an arginine to threonine amino acid substitution p.R124T in the polypeptide and abolishes the cytotoxicity of ECP. The present study aimed to investigate the potential association between polymorphisms in RNASE3 and CM. METHODOLOGY/PRINCIPAL FINDINGS: The RNASE3 gene and flanking regions were sequenced in 206 Ghanaian children enrolled in a hospital based malaria study. An association study was carried out to assess the significance of five SNPs in CM (n=45) and SA (n=56) cases, respectively. The two severe case groups (CM and SA) were compared with the non-severe control group comprising children suffering from UM (n=105). The 371G allele was significantly associated with CM (p=0.00945, OR=2.29, 95% CI=1.22-4.32) but not with SA. Linkage disequilibrium analysis demonstrated significant linkage between three SNPs and the haplotype combination 371G/*16G/*94A was strongly associated with susceptibility to CM (p=0.000913, OR=4.14, 95% CI=1.79-9.56), thus, defining a risk haplotype. The RNASE3 371GG genotype was found to be under frequency-dependent selection. CONCLUSIONS/SIGNIFICANCE: The 371G allele of RNASE3 is associated with susceptibility to CM and forms part of a risk associated haplotype GGA defined by the markers: rs2073342 (G-allele), rs2233860 (G-allele) and rs8019343 (A-allele) respectively. Collectively, these results suggest a hitherto unrecognized role for eosinophils in CM pathogenesis.

Project description:UnlabelledMost patients with cerebral malaria (CM) sustain cerebral microvascular sequestration of Plasmodium falciparum-infected red blood cells (iRBCs). Although many young children are infected with P. falciparum, CM remains a rare outcome; thus, we hypothesized that specific host conditions facilitate iRBC cerebral sequestration. To identify these host factors, we compared the peripheral whole-blood transcriptomes of Malawian children with iRBC cerebral sequestration, identified as malarial-retinopathy-positive CM (Ret+CM), to the transcriptomes of children with CM and no cerebral iRBC sequestration, defined as malarial-retinopathy-negative CM (Ret-CM). Ret+CM was associated with upregulation of 103 gene set pathways, including cytokine, blood coagulation, and extracellular matrix (ECM) pathways (P < 0.01; false-discovery rate [FDR] of <0.05). Neutrophil transcripts were the most highly upregulated individual transcripts in Ret+CM patients. Activated neutrophils can modulate diverse host processes, including the ECM, inflammation, and platelet biology to potentially facilitate parasite sequestration. Therefore, we compared plasma neutrophil proteins and neutrophil chemotaxis between Ret+CM and Ret-CM patients. Plasma levels of human neutrophil elastase, myeloperoxidase, and proteinase 3, but not lactoferrin or lipocalin, were elevated in Ret+CM patients, and neutrophil chemotaxis was impaired, possibly related to increased plasma heme. Neutrophils were rarely seen in CM brain microvasculature autopsy samples, and no neutrophil extracellular traps were found, suggesting that a putative neutrophil effect on endothelial cell biology results from neutrophil soluble factors rather than direct neutrophil cellular tissue effects. Meanwhile, children with Ret-CM had lower levels of inflammation, higher levels of alpha interferon, and upregulation of Toll-like receptor pathways and other host transcriptional pathways, which may represent responses that do not favor cerebral iRBC sequestration.ImportanceThere were approximately 198 million cases of malaria worldwide in 2013, with an estimated 584,000 deaths occurring mostly in sub-Saharan African children. CM is a severe and rare form of Plasmodium falciparum infection and is associated with high rates of mortality and neurological morbidity, despite antimalarial treatment. A greater understanding of the pathophysiology of CM would allow the development of adjunctive therapies to improve clinical outcomes. A hallmark of CM is cerebral microvasculature sequestration of P. falciparum-infected red blood cells (iRBCs), which results in vasculopathy in some patients. Our data provide a global analysis of the host pathways associated with CM and newly identify an association of activated neutrophils with brain iRBC sequestration. Products of activated neutrophils could alter endothelial cell receptors and coagulation to facilitate iRBC adherence. Future studies can now examine the role of neutrophils in CM pathogenesis to improve health outcomes.

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TLR9 polymorphisms are associated with altered IFN-gamma levels in children with cerebral malaria.

Publications

TLR9 polymorphisms are associated with altered IFN-gamma levels in children with cerebral malaria.

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