FIG. 2.

Dose-response to chloroquine of four P. vivax isolates from Myanmar. The inhibition of P. vivax growth by various concentrations of chloroquine in two isolates sensitive to chloroquine and two P. vivax isolates likely resistant to chloroquine is shown. The parasites were cultured for 48 h in the presence of each drug concentration, the contents of each duplicate well were lysed, and the P. vivax LDH antigen concentration was determined by the DELI with MAbs 6C9 and 19G7. Since the starting levels of parasitemia differed among the four isolates, the maximal OD values recorded without drug were adjusted to 100% and results are expressed as the percentage of decrease in the OD values obtained with the various drug concentrations.