Genetic similarity between cysticerci of Taenia solium isolated from human brain and from pigs § Araceli Consuelo Hinojosa-Juarez a , Miguel Sandoval-Balanzario b , Donald Peter McManus c , Amalia Monroy-Ostria a, * a Departamento de Inmunologia, Escuela Nacional de Ciencias Biologicas, IPN, Carpio y Plan de Ayala, Col. Casco de Santo Tomas, C.P. 11340, Mexico, D.F., Mexico b Servicio de Neurocirugia, Hospital de Especialidades, Centro Medico Nacional ‘‘La Raza’’, Mexico c Molecular Parasitology Laboratory, The Queensland Institute of Medical Research, Brisbane, Australia 1. Introduction Taenia solium and Taenia saginata are well-known parasites of medical and economic importance. They cause, cysticercosis in pigs and cattle, which act as intermediate hosts, and taeniasis in humans, acting as definitive hosts. T. solium is severely pathogenic to humans, causing fatal neurocysticercosis when the larval cysticercus stage develops in the central nervous system following the ingestion of parasite eggs; cysticercosis in muscles, subcuta- neous tissue, eyes or other organs may also result. The disease is highly prevalent in regions of Asia, parts of Africa and Latin America and United States (Del Brutto, 2002; Nakao et al., 2002; Ito et al., 2002). Both T. solium and T. saginata have a worldwide distribution; a third human Taenia species, Taenia asiatica, is phylogenetically and morphologically related to T. saginata, and is distributed in Asia (McManus, 2006). In Mexico, neurocysticercosis has an incidence of approxi- mately 0.2–3.4% (Flisser, 1988). There are three morphological types of cysticercus infecting the human nervous system, namely racemose (the most pernicious), cellulose, and parenchymatous, with different locations associated with different degrees of disease severity (Del Brutto, 2002; Chung et al., 2005). It is presumed that these three types of cysticerci are larval stages of T. solium. Knowledge of the genetic structure of T. solium can be applied to understand its epidemiology and transmission, since genetic variants may differ in their infectivity and pathogenicity. Mitochondrial DNA (mtDNA) is considered one of the best molecular markers for demonstrating genetic relationships between genera, species and populations, due to its rapid evolution and sequence divergence (Bowles and McManus, 1994; Gasser et al., 1999). Cytochrome c oxidase subunit I (cox1) and ITS1 have been successfully used in determining phylogenetic relationships among Taenia species. In this study we determined partial sequences for the cox1 and ITS1 genes from cellulose cysticerci Infection, Genetics and Evolution 8 (2008) 653–656 ARTICLE INFO Article history: Received 30 March 2008 Received in revised form 5 June 2008 Accepted 12 June 2008 Available online 3 July 2008 Keywords: Taenia solium Cysticercus cellulose Cysticerus racemosus-genetic similarity ITS1 DNA sequences Mitochondrial cox1 DNA sequences ABSTRACT Mitochondrial (mt) cox1 and ribosomal ITS1 DNA sequences from Taenia solium cysticercus isolates from pigs and cysticerci (racemose and cellulose types) from patients with neurocysticercosis were amplified by the polymerase chain reaction (PCR). The amplicons were sequenced in order to determine the genetic relationship between these types of cysticerci. Phylogenetic trees were constructed and evolutionary distances were calculated. ITS1 and mt cox1 cysticerci sequence data were compared with previously published Taenia spp. sequences. The variation in the ITS1 and cox1 sequences of samples collected from Mexico was minimal, regardless of geographical origin, size or colour of cysticerci from either pigs or human brain. These results suggest that the racemose and cellulose types represent genetically identical metacestodes of T. solium. Alignment of the mt cox1 sequences of the Mexican samples with sequences of other Taenia taxa showed that most were very similar to T. solium from Mexico and T. solium from Colombia; one T. solium Mexican isolate and Taenia hydatigena were placed in the same group close to Taenia crassiceps. The ITS1 sequences for the Mexican T. solium samples indicated the majority were in the same group as the Latin American T. solium. Two Mexican T. solium samples and T. solium from Philippines were placed together in a different group. ß 2008 Elsevier B.V. All rights reserved. § This work was supported by SIP IPN: Project 2003. A. Monroy-Ostria is sponsored by COFAA, EDI, IPN Me ´ xico. A. Hinojosa-Juarez was CONACYT scholar- ship. * Corresponding author. Tel.: +52 55 53 43 88 90; fax: +52 55 53 43 40 88. E-mail address: amonroyos@hotmail.com (A. Monroy-Ostria). Contents lists available at ScienceDirect Infection, Genetics and Evolution journal homepage: www.elsevier.com/locate/meegid 1567-1348/$ – see front matter ß 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.meegid.2008.06.004