Plasmodium falciparum: limited genetic diversity of MSP-2 in isolates circulating in Brazilian endemic areas S. Sallenave-Sales, a, * M.F. Ferreira-da-Cruz, a C.P. Faria, a C. Cerruti Jr., b C.T. Daniel-Ribeiro, a and M.G. Zalis c,d a WHO Collaborating Center for Research and Training in the Immunology of Parasitic Diseases, Departamento de Imunologia, Instituto Oswaldo Cruz/Fiocruz, Avenida Brasil 4365, Manguinhos, CEP 21045-900, Rio de Janeiro, Brazil b Departamento de Medicina Social, Universidade Federal do Esp  ırito Santo, Rio de Janeiro, Brazil c Instituto de Biof  ısica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil d Departamento de Medicina Preventiva, Programa de Doenc ßas Infecto-Parasit  arias, Hospital Universit ario Clementino Fraga Filho, UFRJ, CEP 21949-000, Rio de Janeiro, Brazil Received 13 August 2002; received in revised form 24 April 2003; accepted 5 May 2003 Abstract The genetic polymorphism of the surface merozoite protein 2 (MSP-2) was evaluated in Plasmodium falciparum isolates from individuals with uncomplicated malaria living in a Brazilian endemic area of Peixoto de Azevedo. The frequency of MSP-2 alleles and the survival of genetically different populations clones in 104 isolates were verified by Southern blot and SSCP-PCR. Single and mixed infections were observed in similar frequencies and the rate of detection of FC27 and 3D7 allelic families was equivalent. Eight alleles were identified and among them, the sequence polymorphism was mainly attributed to variations in the repetitive region. Interestingly, in three alleles nucleotide polymorphism was identical to that detected in a previous study, conducted in 1992, in a near Brazilian endemic area. This finding demonstrated the genetic similarity between two isolate groups, besides the certain temporal stability in the allelic patterns. The implications of these data for studies on the genetic diversity are also discussed. Ó 2003 Elsevier Science (USA). All rights reserved. Index Descriptors and Abbreviations: MSP-2; Plasmodium falciparum; allelic diversity; SSCP-PCR; MSP-2, merozoite surface protein 2; PCR, polymerase chain reaction; SSCP, single strand conformational polymorphism; SDS, sodium dodecyl sulfate; EDTA, ethylenediaminetetraacetic acid 1. Introduction The great genetic variability of Plasmodium falcipa- rum contributes to generate a number of biologically and antigenically different parasite populations (Anders et al., 1993; Babiker et al., 1997; Druilhe et al., 1998). This genetic diversity can occur at any endemic level and appears to be related to pathology as well as acquired immunity, since multiple allelic forms could differ in their ability to escape recognition by the hostÕs immune response (Engelbrecht et al., 1995; Gupta et al., 1994; Muller et al., 2001; Zevering et al., 1994). Presumably, this polymorphism would also restrict the effectiveness of subunit vaccines against P. falciparum infection if variable proteins are included (Genton et al., 2002). Additionally, the nature and extent of antigenic diversity could also give new information on the dynamics of host–parasite relationships and on parasite evasion mechanisms. Results from epidemiological investigations using PCR-based assays and allele specific hybridization studying P. falciparum polymorphic antigens have given valuable data on parasite population structure in the human host. These typing schemes estimate the extent of antigenic polymorphism by the frequency evaluation of different circulating allelic variants and by the ge- notype complexity of individual infections (Babiker et al., 1999; Daubersies et al., 1994; Mercereau-Puijalon, 1996; Ntoumi et al., 1995; Sallenave-Sales et al., 2000). In this context, particular attention has been given to antigens associated with the surface of merozoite stage, Experimental Parasitology 103 (2003) 127–135 www.elsevier.com/locate/yexpr * Corresponding author. Fax: +55-21-280-1589. E-mail address: sallenave@ioc.fiocruz.br (S. Sallenave-Sales). 0014-4894/03/$ - see front matter Ó 2003 Elsevier Science (USA). All rights reserved. doi:10.1016/S0014-4894(03)00091-2