Open Access Research

Genetic polymorphisms associated with anti-malarial antibody levels in a low and unstable malaria transmission area in southern Sri Lanka

Rajika L Dewasurendra1, Prapat Suriyaphol2, Sumadhya D Fernando1, Richard Carter3, Kirk Rockett4, Patrick Corran5, Dominic Kwiatkowski46, Nadira D Karunaweera17* and in collaboration with the 7 MalariaGEN Consortium

Author Affiliations

1 Department of Parasitology, Faculty of Medicine, University of Colombo, Colombo, Sri Lanka

2 Bioinformatics and Data Management for Research, Office for Research and Development, Faculty of Medicine, Siriraj Hospital, University of Mahidol, Bangkok, Thailand

3 University of Edinburgh, Edinburgh, UK

4 Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK

5 London School of Hygiene and Tropical Medicine, University of London, London, UK

6 Wellcome Trust Sanger Institute,, Wellcome Trust Genome Campus,, Hinxton, Cambridge,, UK

7 Malaria Genomic Epidemiological Network, University of Oxford, Oxford, UK

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Malaria Journal 2012, 11:281  doi:10.1186/1475-2875-11-281

Published: 20 August 2012

Abstract

Background

The incidence of malaria in Sri Lanka has significantly declined in recent years. Similar trends were seen in Kataragama, a known malaria endemic location within the southern province of the country, over the past five years. This is a descriptive study of anti-malarial antibody levels and selected host genetic mutations in residents of Kataragama, under low malaria transmission conditions.

Methods

Sera were collected from 1,011 individuals residing in Kataragama and anti-malarial antibodies and total IgE levels were measured by a standardized ELISA technique. Host DNA was extracted and used for genotyping of selected SNPs in known genes associated with malaria. The antibody levels were analysed in relation to the past history of malaria (during past 10 years), age, sex, the location of residence within Kataragama and selected host genetic markers.

Results

A significant increase in antibodies against Plasmodium falciparum antigens AMA1, MSP2, NANP and Plasmodium vivax antigen MSP1 in individuals with past history of malaria were observed when compared to those who did not. A marked increase of anti-MSP1(Pf) and anti-AMA1(Pv) was also evident in individuals between 45–59 years (when compared to other age groups). Allele frequencies for two SNPs in genes that code for IL-13 and TRIM-5 were found to be significantly different between those who have experienced one or more malaria attacks within past 10 years and those who did not. When antibody levels were classified into a low-high binary trait, significant associations were found with four SNPs for anti-AMA1(Pf); two SNPs for anti-MSP1(Pf); eight SNPs for anti-NANP(Pf); three SNPs for anti-AMA1(Pv); seven SNPs for anti-MSP1(Pv); and nine SNPs for total IgE. Eleven of these SNPs with significant associations with anti-malarial antibody levels were found to be non–synonymous.

Conclusions

Evidence is suggestive of an age–acquired immunity in this study population in spite of low malaria transmission levels. Several SNPs were in linkage disequilibrium and had a significant association with elevated antibody levels, suggesting that these host genetic mutations might have an individual or collective effect on inducing or/and maintaining high anti–malarial antibody levels.

Keywords:
Anti-malarial antibodies; Host genetic mutations; Low malaria transmission