Genetic diversity of VAR2CSA ID1-DBL2Xb in worldwide Plasmodium falciparum populations: Impact on vaccine design for placental malaria Bita Bordbar a,b , Nicaise Tuikue Ndam a,b,c , Emmanuelle Renard a,b , Sayeh Jafari-Guemouri a,b , Livingstone Tavul d , Charlie Jennison e , Sédami Gnidehou a,b , Rachida Tahar a,b , Dionicia Gamboa f , Jorge Bendezu f , Didier Menard g , Alyssa E. Barry e , Philippe Deloron a,b,1 , Audrey Sabbagh a,b,⇑,1 a PRES Sorbonne Paris Cité, Université Paris Descartes, Paris, France b Institut de Recherche Pour le Développement (IRD), UMR216 Mère et enfant face aux infections tropicales, Paris, France c Centre d‘Étude et de Recherche sur le Paludisme Associé à la Grossesse et à l’Enfance (CERPAGE), Cotonou, Benin d Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea e Division of Infection and Immunity, The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia f Instituto de Medicina Tropical "Alexander Von Humboldt", Universidad Peruana Cayetano Heredia, Lima, Peru g Unité d’Epidémiologie Moléculaire, Institut Pasteur du Cambodge, Phnom Penh, Cambodia article info Article history: Received 10 February 2014 Received in revised form 11 April 2014 Accepted 12 April 2014 Available online 21 April 2014 Keywords: Pregnancy-associated malaria VAR2CSA Plasmodium falciparum Vaccine Next-generation sequencing Genetic structure abstract In placental malaria (PM), sequestration of infected erythrocytes in the placenta is mediated by an inter- action between VAR2CSA, a Plasmodium falciparum protein expressed on erythrocytes, and chondroitin sulfate A (CSA) on syncytiotrophoblasts. Recent works have identified ID1-DBL2Xb as the minimal CSA-binding region within VAR2CSA able to induce strong protective immunity, making it the leading candidate for the development of a vaccine against PM. Assessing the existence of population differences in the distribution of ID1-DBL2Xb polymorphisms is of paramount importance to determine whether geographic diversity must be considered when designing a candidate vaccine based on this fragment. In this study, we examined patterns of sequence variation of ID1-DBL2Xb in a large collection of P. falciparum field isolates (n = 247) from different malaria-endemic areas, including Africa (Benin, Senegal, Cameroon and Madagascar), Asia (Cambodia), Oceania (Papua New Guinea), and Latin America (Peru). Detection of variants and estimation of their allele frequencies were performed using next-gener- ation sequencing of DNA pools. A considerable amount of variation was detected along the whole gene segment, suggesting that several allelic variants may need to be included in a candidate vaccine to achieve broad population coverage. However, most sequence variants were common and extensively shared among worldwide parasite populations, demonstrating long term persistence of those polymor- phisms, probably maintained through balancing selection. Therefore, a vaccine mixture including such stable antigen variants will be putatively applicable and efficacious in all world regions where malaria occurs. Despite similarity in ID1-DBL2Xb allele repertoire across geographic areas, several peaks of strong population differentiation were observed at specific polymorphic loci, pointing out putative targets of humoral immunity subject to positive immune selection. Ó 2014 Elsevier B.V. All rights reserved. 1. Introduction Placental malaria (PM), a manifestation of severe malaria, causes adverse pregnancy outcomes, including maternal anemia, miscarriage and delivery of low birth weight babies, which represents a major risk factor for infant mortality in Africa (Brabin et al., 2004; Umbers et al., 2011). The disease is precipi- tated by the selective accumulation of Plasmodium falciparum- infected erythrocytes (IEs) in the placental microvasculature. Tropism and sequestration of IEs to the placenta is mediated by an interaction between VAR2CSA, a member of the P. falciparum erythrocyte membrane protein 1 (PfEMP1) family of variable surface antigens, and chondroitin sulfate A (CSA) on syncytiotroph- oblasts (Duffy et al., 2006; Fried and Duffy, 1996; Salanti et al., 2003; Tuikue Ndam et al., 2005). A specific immune response acquired during first pregnancies reduces the harmful effects of http://dx.doi.org/10.1016/j.meegid.2014.04.010 1567-1348/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding author at: UMR 216 IRD, Faculté des Sciences Pharmaceutiques et Biologiques, Université Paris Descartes, 4 avenue de l’Observatoire, 75270 Paris Cedex 06, France. Tel.: +33 170649429; fax: +33 153739617. E-mail address: audrey.sabbagh@ird.fr (A. Sabbagh). 1 Contributed equally to the work. Infection, Genetics and Evolution 25 (2014) 81–92 Contents lists available at ScienceDirect Infection, Genetics and Evolution journal homepage: www.elsevier.com/locate/meegid