Chloroquine efficacy studies confirm drug susceptibility of Plasmodium vivax in Chennai, India

Abstract

BackgroundAssessing the Plasmodium vivax burden in India is complicated by the potential threat of an emerging chloroquine (CQ) resistant parasite population from neighbouring countries in Southeast Asia. Chennai, the capital of Tamil Nadu and an urban setting for P. vivax in southern India, was selected as a sentinel site for investigating CQ efficacy and sensitivity in vivax malaria.MethodsCQ efficacy was evaluated with a 28-day in vivo therapeutic study, while CQ sensitivity was measured with an in vitro drug susceptibility assay. In both studies, isolates also underwent molecular genotyping to investigate correlations between parasite diversity and drug susceptibility to CQ. Molecular genotyping included sequencing a 604 base pair (bp) fragment of the P. vivax multidrug resistant gene-1 (Pvmdr1) for single nucleotide polymorphisms (SNPs) and also the amplification of eight microsatellite (MS) loci located across the genome on eight different chromosomes.ResultsIn the 28-day in vivo study (N=125), all subjects were aparasitaemic by Day 14. Passive case surveillance continuing beyond Day 28 in 22 subjects exposed 17 recurrent infections, which ranged from 44 to 148 days post-enrollment. Pvmdr1 sequencing of these recurrent infections revealed that 93.3% had identical mutant haplotypes (958M/Y976/1076L) to their baseline Day 0 infection. MS genotyping further revealed that nine infection pairs were related with ≥75% haplotype similarity (same allele at six or more loci). To test the impact of this mutation on CQ efficacy, an in vitro drug assay (N=68) was performed. No correlation between IC50 values and the percentage of ring-stage parasites prior to culture was observed (rsadj: -0.00063, p = 0.3307) and the distribution of alleles among the Pvmdr1 SNPs and MS haplotypes showed no significant associations with IC50 values.ConclusionsPlasmodium vivax was found to be susceptible to CQ drug treatment in both the in vivo therapeutic drug study and the in vitro drug assay. Though the mutant 1076L of Pvmdr1 was found in a majority of isolates tested, this single mutation did not associate with CQ resistance. MS haplotypes revealed strong heterogeneity in this population, indicating a low probability of reinfection with highly related haplotypes.

Therapeutic assessment of chloroquine–primaquine combined regimen in adult cohort of Plasmodium vivax malaria from a tertiary care hospital in southwestern India

“…Furthermore, similar therapeutic efficacy until day 28 has also been reported from other parts of India viz. 100% (41/41) from Mangalore [ 11 ], 98.1% (105/107) from Chennai [ 12 ] and 96.9% (63/65) from Gujarat [ 13 ] for CQ only and 100% (103/103) from Kolkata [ 14 ] for CQ–PQ combined regimen during the years 2003–2012. Notably, CQ–PQ combined regimen is known to have superior efficacy than CQ alone for preventing P. vivax recurrences [ 14 – 16 ].…”

Plasmodium vivax mdr1 genotypes in isolates from successfully cured patients living in endemic and non-endemic Brazilian areas

“…However, the clear association between the clinical outcome following a three-day CQ treatment and non-synonymous mutations in this gene has never been demonstrated elsewhere. In fact, the single 976 F mutant was not very common worldwide (7.4 %) [ 22 ], and the F F double mutant genotype was detected only in endemic regions of three countries: Brazil [ 36 , 37 ], Honduras [ 38 ] and Papua New Guinea [ 39 ]. In the samples herein analysed, no significant difference was observed between the presence of double 976 F /1076 L mutant (12 %) and single 976 F mutant (15 %) and no single 1076 L mutant was noted.…”

“…Indeed, in Thailand, Indonesia [ 17 ] and Myanmar [ 18 ], as well as in Mauritania [ 19 ] and Cambodia [ 20 ], it has been shown that 976 F mutants were associated with clinical resistance to CQ. In Nepal and India, where P. vivax CQR has not been recorded, prevalence of the 976 F mutation is very low (5 %) [ 21 ] or not detected [ 22 ], while in India the presence of the F1076 L mutation was not associated to CQR. In addition, in Madagascar, despite 5 % of clinical failures more than 90 % of Y976 F mutant parasites were detected [ 33 ].…”

Per protocol analysis of therapeutic efficacy of chloroquine for the treatment of Plasmodium vivax malaria in children

“…13 However there are some threatening reports on chloroquine resistant vivax malaria from different malaria endemic regions of India. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] Thus it is becoming a major public health problem that needs to be dealt with on an urgent basis by initiating proper…”