Attempts were made to find an inexpensive, readily available substitute for human serum requirement for the continuous culture of erythrocytic stages of Plasmodium falciparum. We found that Neopeptone or Proteose-Peptone No. 3 added together with calf serum gave parasite growth rates comparable to, or surpassing, those obtained with human serum. However, first it was necessary to adapt the parasites by a gradual, stepwise reduction in the amount of human serum used, and a concomitant, stepwise increase in the substitutes added.
Studies of the ability of Plasmodium falciparum to grow in vitro in the red blood cells of subjects with certain beta-thalassemia syndromes are often difficult to interpret because of the known inhibitory effect of an elevated cellular content of human fetal hemoglobin (HbF). P falciparum therefore was cultured in vitro in the erythrocytes of subjects with hemoglobin H (HbH) disease and various other alpha- thalassemia genotypes that are unaccompanied by increased levels of HbF. Growth of the malaria parasite was markedly retarded in HbH red blood cells, when compared with growth in blood from normal control subjects. No consistent impairment of growth was seen in the erythrocytes of subjects having deletion of only one or two alpha- globin genes. These results indicate that erythrocytes with a severe thalassemia phenotype provide a less hospitable growth environment for P falciparum than normally hemoglobinized red blood cells, even in the absence of increased levels of HbF.
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