PLASMODIUM-YOELII NIGERIENSIS - BIOLOGICAL MECHANISMS OF RESISTANCE TO CHLOROQUINE

The sensitivity to chloroquine according to the degree of synchronicit y of Plasmodium yoelii nigeriensis, which is considered to be the most resistant of the rodent malaria strains, was studied. The infection w as synchronised by means of a Percoll-glucose gradient which separates rings and young trophozoites from other stages. The mid term trophozo ite, when it predominated in the blood at the time of treatment, was s hown to be as sensitive to chloroquine as Plasmodium vinckei petteri. According to previous results indicating that part of the population o f merozoites is latent and penetrates around midnight, the inoculation s were timed in order to obtain a lower or higher degree of synchronis ation. The infection appeared to be better synchronised if rings and y oung trophozoites, were inoculated at 06:00 hrs rather than at 15:00 h rs and consequently the efficacy of chloroquine was higher in the farm er than in the latter.