Human candidate gene polymorphisms and risk of severe malaria in children in Kilifi, Kenya: a case-control association study
LANCET HAEMATOLOGY
Authors: Ndila, Carolyne M.; Uyoga, Sophie; Macharia, Alexander W.; Nyutu, Gideon; Peshu, Norbert; Ojal, John; Shebe, Mohammed; Awuondo, Kennedy O.; Mturi, Neema; Tsofa, Benjamin; Sepulveda, Nuno; Clark, Taane G.; Band, Gavin; Clarke, Geraldine; Rowlands, Kate; Hubbart, Christina; Jeffreys, Anna; Kariuki, Silvia; Marsh, Kevin; Mackinnon, Margaret; Maitland, Kathryn; Kwiatkowski, Dominic P.; Rockett, Kirk A.; Williams, Thomas N.
Abstract
Background Human genetic factors are important determinants of malaria risk. We investigated associations between multiple candidate polymorphisms-many related to the structure or function of red blood cells-and risk for severe Plasmodium falciparum malaria and its specific phenotypes, including cerebral malaria, severe malaria anaemia, and respiratory distress. Methods We did a case-control study in Kilifi County, Kenya. We recruited as cases children presenting with severe malaria to the high-dependency ward of Kilifi County Hospital. We included as controls infants born in the local community between Aug 1, 2006, and Sept 30, 2010, who were part of a genetics study. We tested for associations between a range of candidate malaria-protective genes and risk for severe malaria and its specific phenotypes. We used a permutation approach to account for multiple comparisons between polymorphisms and severe malaria. We judged p values less than 0.005 significant for the primary analysis of the association between candidate genes and severe malaria. Findings Between June 11, 1995, and June 12, 2008, 2244 children with severe malaria were recruited to the study, and 3949 infants were included as controls. Overall, 263 (12%) of 2244 children with severe malaria died in hospital, including 196 (16%) of 1233 with cerebral malaria. We investigated 121 polymorphisms in 70 candidate severe malaria-associated genes. We found significant associations between risk for severe malaria overall and polymorphisms in 15 genes or locations, of which most were related to red blood cells: ABO, ATP2B4, ARL14, CD40LG, FREM3, INPP4B, G6PD, HBA (both HBA1 and HBA2), HBB, IL10, LPHN2 (also known as ADGRL2), LOC727982, RPS6KL1, CAND1, and GNAS. Combined, these genetic associations accounted for 5.2% of the variance in risk for developing severe malaria among individuals in the general population. We confirmed established associations between severe malaria and sickle-cell trait (odds ratio [OR] 0.15, 95% CI 0.11-0.20; p=2.61 x 10(-58)), blood group O (0.74, 0.66-0.82; p=6.26 x 10(-8)), and -alpha(3.7)-thalassaemia (0.83, 0.76-0.90; p=2.06 x 10(-6)). We also found strong associations between overall risk of severe malaria and polymorphisms in both ATP2B4 (OR 0.76, 95% CI 0.63-0.92; p=0.001) and FREM3 (0.64, 0.53-0.79; p=3.18 x 10(-14)). The association with FREM3 could be accounted for by linkage disequilibrium with a complex structural mutation within the glycophorin gene region (comprising GYPA, GYPB, and GYPE) that encodes for the rare Dantu blood group antigen. Heterozygosity for Dantu was associated with risk for severe malaria (OR 0.57, 95% CI 0.49-0.68; p= 3.22 x 10(-11)), as was homozygosity (0.26, 0.11-0.62; p=0.002). Interpretation Both ATP2B4 and the Dantu blood group antigen are associated with the structure and function of red blood cells. ATP2B4 codes for plasma membrane calcium-transporting ATPase 4 (the major calcium pump on red blood cells) and the glycophorins are ligands for parasites to invade red blood cells. Future work should aim at uncovering the mechanisms by which these polymorphisms can result in severe malaria protection and investigate the implications of these associations for wider health. Copyright (C) 2018 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license.
Summary of validation studies from twenty-six forensic laboratories in the United States and Canada on the use of the AmpliType(R) PM PCR amplification and typing kit
JOURNAL OF FORENSIC SCIENCES
Authors: Word, CJ; Sawosik, TM; Bing, DH
Abstract
A cooperative study was undertaken to collect and summarize the results of validation studies from forensic laboratories in the United States and Canada on the use of the AmpliType(R) PM PCR amplification and typing kit for genetic typing of forensic biological evidence. This report compiles data from 26 laboratories on: 1) reproducibility studies on DNA extracted from various samples, 2) genetic typing of DNA extracted from a variety of biological samples on various substrates, 3) the effects of exogenous chemicals, materials, and environmental factors on test results, 4) sensitivity studies to determine the least detectable amount of extracted genomic DNA that can be reliably typed, 5) analysis of mixtures containing two sources of genomic DNA, 6) cross-hybridization with DNA extracted from various nonhuman species, and 7) evaluation of assay performance on parallel studies with other genetic typing systems on proficiency test panels, mock cases, and adjudicated/nonprobative casework. Equivalent results were obtained by each laboratory that supplied data, demonstrating the reliability and consistency of the test. Overall, it can be concluded from this study that the AmpliType PM PCR amplification and typing kit meets the guidelines of the Technical Working Group on DNA Analysis Methods (TWGDAM) and there is general scientific acceptability of this kit for forensic DNA testing.