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Toll-like receptor (TLR) polymorphisms in African children: Common TLR-4 variants predispose to severe malaria

Frank P Mockenhaupt1, Jakob P Cramer, Lutz Hamann

  • 1Institute of Tropical Medicine Berlin, Charité-Universitätsmedizin Berlin, Spandauer Damm 130, 14050 Berlin, Germany.

Proceedings of the National Academy of Sciences of the United States of America
|December 24, 2005
PubMed

Insights

Genetic variations in Toll-like Receptor 4 (TLR4) increase the risk of severe malaria. Specific TLR4 polymorphisms, Asp299Gly and Thr399Ile, were significantly more frequent in Ghanaian children with severe malaria, highlighting their role in disease susceptibility.

Area of Science:

  • Immunology
  • Genetics
  • Infectious Diseases

Background:

  • Malaria remains a major global health threat, causing over a million deaths annually.
  • Genetic host factors significantly influence malaria susceptibility and severity.
  • Toll-like Receptors (TLRs) are implicated in recognizing Plasmodium falciparum components and mediating host responses.

Purpose of the Study:

  • To investigate the association between polymorphisms in Toll-like Receptor (TLR)-2, -4, and -9 genes and susceptibility to severe malaria in Ghanaian children.
  • To identify specific genetic variants that confer increased risk for severe malaria.

Main Methods:

  • A case-control study was conducted involving 870 Ghanaian children.
  • Genotyping was performed to analyze polymorphisms in TLR-2, TLR-4, and TLR-9 genes.
  • Statistical analyses were used to compare allele frequencies between severe malaria patients and healthy controls.

Main Results:

  • No common TLR-2 variants found in Caucasians/Asians; a rare mutation (Leu658Pro) impairing TLR-2 signaling was identified.
  • No polymorphisms were detected in the TLR-9 Toll/IL-1 receptor domain; frequent TLR-9 promoter polymorphisms showed no clear association with malaria severity.
  • The TLR-4-Asp299Gly variant was more frequent in severe malaria patients (24.1%) than controls (17.6%), conferring a 1.5-fold increased risk.
  • The TLR-4-Thr399Ile variant was also more frequent in patients (6.2%) than controls (2.4%), conferring a 2.6-fold increased risk.

Conclusions:

  • TLR-4 polymorphisms, specifically Asp299Gly and Thr399Ile, are associated with an increased risk of severe malaria in Ghanaian children.
  • These findings suggest a significant role for TLR4-mediated immune responses in malaria pathogenesis and disease manifestation.

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