Differential genetic hitchhiking around mutant pfcrt alleles in the Indian Plasmodium falciparum population.
OBJECTIVE
To study the origin and spread of the chloroquine-resistant Plasmodium falciparum population in the Indian subcontinent.


METHODS
Fourteen microsatellites spanning a ∼120 kb region, flanking the P. falciparum chloroquine resistance transporter (pfcrt) gene, were analysed in 185 parasite isolates.


RESULTS
The Indian P. falciparum population exhibited a selective valley of reduced genetic variation in the flanking microsatellites of the mutant pfcrt alleles (up to ±29 kb) as compared with the wild-type allele. This valley is much narrower than the ±200 kb valley reported from African and South-East Asian countries. The majority of the isolates showed asymmetry in the selective valley, where upstream microsatellites showed less genetic variation than the downstream microsatellites. Regional variation in the width and symmetry of the selective valley was noticed, which seems to be related to the number of pfcrt alleles present in the parasite population of a region. Forty-six different microsatellite haplotypes were observed among the P. falciparum isolates containing mutant pfcrt alleles. Parasite populations from different regions of mainland India shared microsatellite haplotypes between them, but they shared none with the isolates from the Andaman and Nicobar Islands, and vice versa. Indian isolates shared microsatellite haplotypes with the isolates from Papua New Guinea and Thailand.


CONCLUSIONS
With regard to chloroquine there is regional variation in the selection pressure on the P. falciparum population in India. These findings will help the regional implementation of drug policy in India's malaria control programme.
Department of Biotechnology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India.
Vanshika
V
Lumb
Rahul
R
Madan
Manoj K
MK
Das
Vipin
V
Rawat
Vas
V
Dev
Wajihullah
W
Khan
Haris
H
Khan
Yagya D
YD
Sharma
D000483:Alleles; D000818:Animals; D000962:Antimalarials / Q000494:pharmacology*; D058448:Biota; D002738:Chloroquine / Q000494:pharmacology*; D004351:Drug Resistance; D006801:Humans; D007194:India; D026901:Membrane Transport Proteins / Q000235:genetics*; D018895:Microsatellite Repeats; D010963:Plasmodium falciparum / Q000145:classification* / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D011110:Polymorphism, Genetic; D015800:Protozoan Proteins / Q000235:genetics*; D012641:Selection, Genetic
D000962:Antimalarials; D026901:Membrane Transport Proteins; C416369:PfCRT protein, Plasmodium falciparum; D015800:Protozoan Proteins; D002738:Chloroquine