Entamoeba histolytica: sequence conservation of the Gal/GalNAc lectin from clinical isolates q David L. Beck, a,b,1 Mehmet Tanyuksel, c,1 Aaron J. Mackey, b Rashidul Haque, d Nino Trapaidze, e William R. Pearson, f Brendan Loftus, g and William A. Petri Jr. a,b,h, * a Department of Internal Medicine, University of Virginia, Charlottesville, VA 22908-1340, USA b Department of Microbiology, University of Virginia, Charlottesville, VA 22908-1340, USA c Department of Microbiology and Clinical Microbiology, Gulhane Military Medical Academy, Etlik, Ankara 06018, Turkey d International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh e National Center for Disease Control of Georgia, 9 Asatiani Street, Tbilisi 380077, Georgia f Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA 22908-1340, USA g The Institute for Genomic Research, Rockville, MD 20850, USA h Department of Pathology, University of Virginia, Charlottesville, VA 22908-1340, USA Received 18 April 2002; accepted 19 August 2002 Abstract The Gal/GalNAc lectin gene of Entamoeba histolytica is a major amebic virulence protein responsible for interaction with host tissues. We investigated sequence differences in the Gal/GalNAc lectin heavy subunit in three isolates from Bangladesh and one isolate from Georgia, each of which was determined to be genetically distinct by SREHP AluI digestion. Interestingly, we observed only slight genetic diversity in the lectin gene as compared with the HM1:IMSS laboratory strain, originally a clinical isolate from Mexico. Genetic conservation of the Gal/GalNAc lectin between isolates may reflect that the lectin is under strong functional se- lection or possibly, that E. histolytica is a clonal population. Sequence conservation of the lectin indicates that immune responses against it should be cross-protective. Index Descriptors and Abbreviations: Entamoeba histolytica, Entamoeba dispar, Protozoa, Amebiasis, Gal/GalNAc lectin, Serine-rich E. histolytica protein (SREHP), Polymerase chain reaction (PCR), Carbohydrate recognition domain (CRD). Ó 2002 Elsevier Science (USA). All rights reserved. 1. Introduction The protozoan parasite Entamoeba histolytica is a major cause of colitis and liver abscess in humans. Ge- netic variation between strains of E. histolytica is a rel- atively unexplored topic. Analysis of the cell surface ‘‘serine-rich E. histolytica protein’’ (SREHP) gene that contains repetitive sequence motifs (Stanley et al., 1990) has demonstrated genetic variation between isolates (Clark and Diamond, 1993). In the Mirpur region of Dhaka, Bangladesh, 34 unique SREHP polymorphisms were observed among 54 isolates from children (Ayeh- Kumi et al., 2001). It is perhaps surprising in the face of this genetic heterogeneity that acquired immunity de- velops in 86% of individuals with a mucosal IgA re- sponse against the carbohydrate recognition domain of another cell surface protein, the galactose (Gal) and N- acetyl-D-galactosamine (GalNAc) inhibitable lectin (Haque et al., 2001, 2002). The amebic Gal/GalNAc lectin is a heterodimer of 170kDa (heavy) and 31/ 35kDa (light) subunits noncovalently associated with a 150kDa (intermediate) subunit (Petri and Ravdin, 1991; Petri et al., 2002). While the function of the SREHP protein is unknown, the Gal/GalNAc lectin is an essential virulence factor required for parasite–host adherence and invasion. The CRD is located within the lectin heavy subunit cysteine-rich region (Dodson et al., Experimental Parasitology 101 (2002) 157–163 www.academicpress.com q The sequence data reported herein have been submitted to GenBank and assigned Accession Nos. AF501267–AF501280 and AF533541. * Corresponding author. Fax: +(434) 924-0075. E-mail address: wap3g@virginia.edu (W.A. Petri Jr.). 1 These authors contributed equally to this work. 0014-4894/02/$ - see front matter Ó 2002 Elsevier Science (USA). All rights reserved. PII:S0014-4894(02)00113-3