ELSEVIER Molecular and Biochemical Parasitology 63 (1994) 203 212 MOLECULAR AND BIOCHEMICAL PARASITOLOGY Plasmodium falciparum genetic diversity can be characterised using the polymorphic merozoite surface antigen 2 (MSA-2) gene as a single locus marker Nicole Prescott a'*, Anthony W. Stowers a, Qin Cheng a, Albino Bobogare b, Christine M. Rzepczyk a, Allan Saul a aQueensland Institute of Medical Research, 300 Herston Road, Herston, Brisbane, Qld., Australia, 4029; h Solomon Islands Medical Training and Research Institute, Honiara, Solomon Islands Received 22 July 1993; accepted 1 November 1993 Abstract The genetic diversity of Solomon Island Plasmodiumfalciparum isolates was examined using MSA-2 as a single locus marker. Amplification of MSA-2 gene fragments showed size polymorphism and the presence of mixed infections. Sequence analysis indicated a global representation of MSA-2 alleles with representatives of 3D7/CAMP allelic subfamilies and the FCQ-27 allelic family being identified. A simplified method of characterisation, utilising PCR- RFLPs of MSA-2 gene fragments, was developed. The RFLPs allowed identification of allelic families and further distinction within the 3D7/CAMP family. The amplification of MSA-2 gene fragments from culture derived lines revealed a loss of diversity for a number of Solomon Island isolates. Genomic diversity was confirmed for Solomon Island lines, along with Papua New Guinean and Thai lines, by the generation of 7H8/6 fingerprints. All lines were distinct and band sharing frequencies and Wagner tree construction failed to identify any geographic clustering. Key words."Plasmodiumfalciparum; Merozoite surface antigen 2; Genetic diversity; Polymerase chain reaction; Restric- tion fragment length polymorphism; DNA fingerprinting ~ponding author. Tel.: 61 7 362 0417; Fax: 61 7 362 0401, Email: nicoleP@qimr.edu.au. Note." Nucleotide sequence data reported in this paper have been submitted to the GenBank TM data base with the accession numbers L19045-L19053. Abbreviations." MSA-2, merozoite surface antigen 2; PCR, polymerase chain reaction; RFLP, restriction fragment length polymorphism. 0166-6851/94/$7.00 © 1994 Elsevier Science B.V. All rights reserved SSDI 0166-6851(93)E0189-F 1. Introduction Malaria continues to pose a serious health pro- blem in almost 100 countries or areas, represent- ing approximately 40% of the world's population. In 1990, the highest reported incidence of malaria cases outside Africa occurred in the Solomon Is- lands, with 372.1 cases reported per 1000 popula- tion (WHO World Malaria Situation, 1992). The percentage of these cases attributed to Plasmodium