RESUMEN
BACKGROUND: Plasmodium vivax malaria is a major public health problem in French Guiana. Some cases of resistance to chloroquine, the first-line treatment used against P. vivax malaria, have been described in the Brazilian Amazon region. The aim of this study is to investigate a possible dispersion of chloroquine-resistant P. vivax isolates in French Guiana. The genotype, polymorphism and copy number variation, of the P. vivax multidrug resistance gene-1 (pvmdr1) have been previously associated with modification of the susceptibility to chloroquine. METHODS: The pvmdr1 gene polymorphism was evaluated by sequencing and copy number variation was assessed by real-time PCR, in P. vivax isolates obtained from 591 symptomatic patients from 1997 to 2013. RESULTS: The results reveal that 1.0% [95% CI 0.4-2.2] of French Guiana isolates carry the mutations Y976F and F1076L, and that the proportion of isolates with multiple copies of pvmdr1 has significantly decreased over time, from 71.3% (OR = 6.2 [95% CI 62.9-78.7], p < 0.0001) in 1997-2004 to 12.8% (OR = 0.03 [95% CI 9.4-16.9], p < 0.0001) in 2009-2013. A statistically significant relationship was found between Guf-A (harboring the single mutation T958M) and Sal-1 (wild type) alleles and pvmdr1 copy number. CONCLUSIONS: Few P. vivax isolates harboring chloroquine-resistant mutations in the pvmdr1 gene are circulating in French Guiana. However, the decrease in the prevalence of isolates carrying multiple copies of pvmdr1 might indicate that the P. vivax population in French Guiana is evolving towards a decreased susceptibility to chloroquine.
Asunto(s)
Dosificación de Gen , Malaria Vivax/parasitología , Proteínas Asociadas a Resistencia a Múltiples Medicamentos/genética , Plasmodium vivax/genética , Plasmodium vivax/aislamiento & purificación , Polimorfismo Genético , Proteínas Protozoarias/genética , Adolescente , Adulto , Anciano , Alelos , Antimaláricos/farmacología , Niño , Preescolar , Cloroquina/farmacología , Resistencia a Medicamentos , Femenino , Guyana Francesa , Genotipo , Humanos , Lactante , Masculino , Persona de Mediana Edad , Mutación Missense , Reacción en Cadena en Tiempo Real de la Polimerasa , Análisis de Secuencia de ADN , Adulto JovenRESUMEN
In regions with high malaria endemicity, the withdrawal of chloroquine (CQ) as first-line treatment of Plasmodium falciparum infections has typically led to the restoration of CQ susceptibility through the reexpansion of the wild-type (WT) allele K76 of the chloroquine resistance transporter gene (pfcrt) at the expense of less fit mutant alleles carrying the CQ resistance (CQR) marker K76T. In low-transmission settings, such as South America, drug resistance mutations can attain 100% prevalence, thereby precluding the return of WT parasites after the complete removal of drug pressure. In French Guiana, despite the fixation of the K76T allele, the prevalence of CQR isolates progressively dropped from >90% to <30% during 17 y after CQ withdrawal in 1995. Using a genome-wide association study with CQ-sensitive (CQS) and CQR isolates, we have identified a single mutation in pfcrt encoding a C350R substitution that is associated with the restoration of CQ susceptibility. Genome editing of the CQR reference strain 7G8 to incorporate PfCRT C350R caused a complete loss of CQR. A retrospective molecular survey on 580 isolates collected from 1997 to 2012 identified all C350R mutant parasites as being CQS. This mutation emerged in 2002 and rapidly spread throughout the P. falciparum population. The C350R allele is also associated with a significant decrease in piperaquine susceptibility in vitro, suggesting that piperaquine pressure in addition to potential fitness costs associated with the 7G8-type CQR pfcrt allele may have selected for this mutation. These findings have important implications for understanding the evolutionary dynamics of antimalarial drug resistance.
