title: Polymorphisms of TNF-enhancer and gene for FcgammaRIIa correlate with the severity of falciparum malaria in the ethnically diverse Indian population.
abstract: BACKGROUND
  Susceptibility/resistance to Plasmodium falciparum malaria has been correlated with polymorphisms in more than 30 human genes with most association analyses having been carried out on patients from Africa and south-east Asia. The aim of this study was to examine the possible contribution of genetic variants in the TNF and FCGR2A genes in determining severity/resistance to P. falciparum malaria in Indian subjects.
  
  
  METHODS
  Allelic frequency distribution in populations across India was first determined by typing genetic variants of the TNF enhancer and the FCGR2A G/A SNP in 1871 individuals from 55 populations. Genotyping was carried out by DNA sequencing, single base extension (SNaPshot), and DNA mass array (Sequenom). Plasma TNF was determined by ELISA. Comparison of datasets was carried out by Kruskal-Wallis and Mann-Whitney tests. Haplotypes and LD plots were generated by PHASE and Haploview, respectively. Odds ratio (OR) for risk assessment was calculated using EpiInfotrade mark version 3.4.
  
  
  RESULTS
  A novel single nucleotide polymorphism (SNP) at position -76 was identified in the TNF enhancer along with other reported variants. Five TNF enhancer SNPs and the FCGR2A R131H (G/A) SNP were analyzed for association with severity of P. falciparum malaria in a malaria-endemic and a non-endemic region of India in a case-control study with ethnically-matched controls enrolled from both regions. TNF -1031C and -863A alleles as well as homozygotes for the TNF enhancer haplotype CACGG (-1031T>C, -863C>A, -857C>T, -308G>A, -238G>A) correlated with enhanced plasma TNF levels in both patients and controls. Significantly higher TNF levels were observed in patients with severe malaria. Minor alleles of -1031 and -863 SNPs were associated with increased susceptibility to severe malaria. The high-affinity IgG2 binding FcgammaRIIa AA (131H) genotype was significantly associated with protection from disease manifestation, with stronger association observed in the malaria non-endemic region. These results represent the first genetic analysis of the two immune regulatory molecules in the context of P. falciparum severity/resistance in the Indian population.
  
  
  CONCLUSIONS
  Association of specific TNF and FCGR2A SNPs with cytokine levels and disease severity/resistance was indicated in patients from areas with differential disease endemicity. The data emphasizes the need for addressing the contribution of human genetic factors in malaria in the context of disease epidemiology and population genetic substructure within India.
authors.affiliation: Division of Molecular and Structural Biology, Central Drug Research Institute, Post box 173, Chattar Manzil, Mahatma Gandhi Marg, Lucknow-226001, India. swaps_24@yahoo.com
authors.forename: Swapnil
authors.initials: S
authors.lastname: Sinha
authors.forename: Shrawan K
authors.initials: SK
authors.lastname: Mishra
authors.forename: Shweta
authors.initials: S
authors.lastname: Sharma
authors.forename: Phani K
authors.initials: PK
authors.lastname: Patibandla
authors.forename: Prashant K
authors.initials: PK
authors.lastname: Mallick
authors.forename: Surya K
authors.initials: SK
authors.lastname: Sharma
authors.forename: Sanjib
authors.initials: S
authors.lastname: Mohanty
authors.forename: Sudhanshu S
authors.initials: SS
authors.lastname: Pati
authors.forename: Saroj K
authors.initials: SK
authors.lastname: Mishra
authors.forename: Bheshaj K
authors.initials: BK
authors.lastname: Ramteke
authors.forename: Rm
authors.initials: R
authors.lastname: Bhatt
authors.forename: Hema
authors.initials: H
authors.lastname: Joshi
authors.forename: Aditya P
authors.initials: AP
authors.lastname: Dash
authors.forename: Ramesh C
authors.initials: RC
authors.lastname: Ahuja
authors.forename: Shally
authors.initials: S
authors.lastname: Awasthi
authors.forename: Vimala
authors.initials: V
authors.lastname: Venkatesh
authors.forename: Saman
authors.initials: S
authors.lastname: Habib
mesh_terms: D000349:Africa / Q000208:ethnology; D015703:Antigens, CD / Q000235:genetics*; D001210:Asia, Southeastern / Q000208:ethnology; D004797:Enzyme-Linked Immunosorbent Assay; D005787:Gene Frequency; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006239:Haplotypes; D006801:Humans; D007194:India / Q000453:epidemiology; D016778:Malaria, Falciparum / Q000208:ethnology / Q000235:genetics* / Q000473:pathology; D016017:Odds Ratio; D020641:Polymorphism, Single Nucleotide; D017452:Receptors, IgG / Q000235:genetics*; D012720:Severity of Illness Index; D014409:Tumor Necrosis Factor-alpha / Q000097:blood / Q000235:genetics*
chemical_list: D015703:Antigens, CD; C080568:Fc gamma receptor IIA; D017452:Receptors, IgG; C439524:TNF protein, human; D014409:Tumor Necrosis Factor-alpha