Identifying and characterising the Plasmodium falciparum RhopH3 Plasmodium vivax homologue Alvaro Mongui a , Oscar Perez-Leal a , Jose Rojas-Caraballo a , Diana I. Angel a , Jimena Cortes b , Manuel A. Patarroyo a,c, * a Molecular Biology Department, Fundacion Instituto de Inmunologia de Colombia, Carrera 50#26–00, Bogota, Colombia b Immunochemistry Department, Fundacion Instituto de Inmunologia de Colombia, Bogota, Colombia c Universidad Nacional de Colombia, Bogota, Colombia Received 24 April 2007 Available online 11 May 2007 Abstract Four Plasmodium species cause malaria in humans, Plasmodium falciparum being the most widely studied to date. All Plasmodium species have paired club-shaped organelles towards their apical extreme named rhoptries that contain many lipids and proteins which are released during target cell invasion. P. falciparum RhopH3 is a rhoptry protein triggering important immune responses in patients from endemic regions. It has also been shown that anti-RhopH3 antibodies inhibit in vitro invasion of erythrocytes. Recent immunisation studies in mice with the Plasmodium yoelii and Plasmodium berghei RhopH3 P. falciparum homologue proteins found that they are able to induce protection in murine models. This study described identifying and characterising RhopH3 protein in Plasmodium vivax; it is encoded by a seven exon gene and expressed during the parasite’s asexual stage. PvRhopH3 has similar processing to its homologue in P. falciparum and presents a cellular immunolocalisation pattern characteristic of rhoptry proteins. Ó 2007 Elsevier Inc. All rights reserved. Keywords: Malaria; Plasmodium vivax; Rhoptry; RhopH3; Vaccine candidate Malaria, one of the most prevalent tropical diseases worldwide, is caused by four parasite species: Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae, and Plasmodium ovale, being the first two responsible for 90% of all malaria cases [1]. Several P. falciparum antigens belonging to either the pre-erythrocytic or the intra-eryth- rocytic stages of the parasite’s life cycle have been identified during the last two decades and tested as vaccine candi- dates [2]. The antigens which have been chosen in produc- ing an anti-malarial vaccine against intra-erythrocytic stages are mainly located on the merozoite surface or in the apical organelles, such as rhoptries, micronemes, and dense granules. Rhoptry proteins that are released during the invasion process have been classified into two protein complexes [3–6]. The Rhop-L low molecular weight com- plex (including the rhoptry-associated proteins, RAP) and the high molecular weight complex (Rhop-H), where 105, 135, and 150 kDa polypeptides (RhopH1, RhopH2, and RhopH3, respectively) have been identified, forming a non-covalent and stable association [7,8]. It has been pro- posed that the proteins belonging to both complexes are bound by a GPI membrane-anchored protein named RAMA (rhoptry associated membrane antigen) and thus targeted into the newly forming rhoptries as the parasite matures [9]. The RhopH3 encoding gene has been characterised into several Plasmodium species (P. falciparum, Plasmodium yoelii, and Plasmodium berghei) [10–13] and this protein is a leading vaccine candidate. Strong immune response against RhopH3 has been observed in malaria-infected people and anti-RhopH3 antibodies are able to inhibit 0006-291X/$ - see front matter Ó 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.bbrc.2007.05.015 * Corresponding author. Address: Molecular Biology Department, Fundacion Instituto de Inmunologia de Colombia, Carrera 50#26–00, Bogota, Colombia. Fax: +57 (1) 4815269. E-mail address: mapatarr@fidic.org.co (M.A. Patarroyo). www.elsevier.com/locate/ybbrc Biochemical and Biophysical Research Communications 358 (2007) 861–866