Genetic polymorphism of merozoite surface protein-1 in Plasmodium falciparum isolates from patients with mild to severe malaria in Libreville, Gabon

We assessed Plasmodium (P.) falciparum allelic diversity based on clinical severity and age. The study was conducted from 2011 to 2012 in Libreville, Gabon where malaria prevalence was 24.5%. The polymorphism of the merozoite surface protein-1 (msp1) locus was analyzed in isolates from patients with complicated and uncomplicated malaria. Blood was collected on filter paper. After DNA extraction, genotyping of the msp1 gene was performed using nested PCR. The K1, Ro33, and Mad20 allelic families were detected in 71 (63%), 64 (57%), and 38 (34%) of the 112 analyzed samples, respectively. Overall, 17 K1 and 11 Mad20 alleles were detected. There was no association between msp1 allelic families and age. Mad20 allelic diversity increased with the severity of malaria. The number of K1 and Mad20 alleles decreased with age. The multiplicity of infection (MOI) was 1-6 genotypes and the complexity of infection (COI) 1.8 +/- 1. The COI differed based on age: it was 1.9 (+/- 1.1) in the isolates from adults, 1.8 (+/- 1.1) in those from 0-5 year-old children, whereas it tended to be lower (1.6 +/- 0.8) in those from 6-15 year-old children. Extensive genetic diversity is found in P. falciparum strains circulating in Libreville. The number of specific msp1 alleles increased with clinical severity, suggesting an association between the diversity and the severity of malaria.