Allelic variation in the cg2 gene does not correlate with chloroquine resistance among Indian Plasmodium falciparum isolates

The cg2 gene of Plasmodium falciparum has been proposed to be associated with chloroquine resistance. Here we describe PCR amplification and sequencing of all the four repeat regions (kappa (kappa), gamma (gamma), psi (phi) and omega (omega) of this gene, from Indian isolates. There were variant forms for each of these repeat regions (two for kappa and gamma, and three for phi and omega) among the 123 Indian isolates of P. falciparum. Among these isolates certain forms of phi and omega repeats were uniquely present while some of the reported forms of the kappa and omega repeats were absent. The pattern of combination of all four repeat regions of cg2 gene (genotype) was analysed from 52 isolates. A total of 11 different genotypes were observed among these cases, of which 10 were unique to Indian isolates. Certain genotypes were more common than others. The nucleotide sequencing of all the four repeat regions revealed that Indian isolates have some unique repeating units within the gamma and omega domains. Altogether, the PCR and sequencing results showed that there was an unrelatedness between cg2 repeats and chloroquine resistance. (C) 2001 Australian Society for Parasitology Inc. Published by Elsevier Science Ltd. All rights reserved.