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Open Access Research

Expression of a type B RIFIN in Plasmodium falciparum merozoites and gametes

Steven B Mwakalinga1, Christian W Wang1*, Dominique C Bengtsson1, Louise Turner1, Bismarck Dinko2, John P Lusingu3, David E Arnot14, Colin J Sutherland2, Thor G Theander1 and Thomas Lavstsen1

  • * Corresponding author: Christian W Wang cwang@sund.ku.dk

  • † Equal contributors

Author Affiliations

1 Centre for Medical Parasitology, Department of International Health, Immunology, and Microbiology, University of Copenhagen and at Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), 1014, Copenhagen, Denmark

2 Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK

3 National Institute for Medical Research (NIMR), Tanga Medical Research Centre, Tanga, Tanzania

4 Institute of Immunology and Infection Research, School of Biology, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JT, Scotland, UK

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Malaria Journal 2012, 11:429  doi:10.1186/1475-2875-11-429

Published: 21 December 2012

Abstract

Background

The ability of Plasmodium falciparum to undergo antigenic variation, by switching expression among protein variants encoded by multigene families, such as var, rif and stevor, is key to the survival of this parasite in the human host. The RIFIN protein family can be divided into A and B types based on the presence or absence of a 25 amino acid motif in the semi-conserved domain. A particular type B RIFIN, PF13_0006, has previously been shown to be strongly transcribed in the asexual and sexual stages of P. falciparum in vitro.

Methods

Antibodies to recombinant PF13_0006 RIFIN were used in immunofluorescence and confocal imaging of 3D7 parasites throughout the asexual reproduction and sexual development to examine the expression of PF13_0006. Furthermore, reactivity to recombinant PF13_0006 was measured in plasma samples collected from individuals from both East and West African endemic areas.

Results

The PF13_0006 RIFIN variant appeared expressed by both released merozoites and gametes after emergence. 7.4% and 12.1% of individuals from East and West African endemic areas, respectively, carry plasma antibodies that recognize recombinant PF13_0006, where the antibody responses were more common among older children.

Conclusions

The stage specificity of PF13_0006 suggests that the diversity of RIFIN variants has evolved to provide multiple specialized functions in different stages of the parasite life cycle. These data also suggest that RIFIN variants antigenically similar to PF13_0006 occur in African parasite populations.