PLASMODIUM-FALCIPARUM ROSETTING IS ASSOCIATED WITH MALARIA SEVERITY IN KENYA

Rosette formation in 154 fresh Plasmodium falciparum isolates from Ken yan children with mild (n = 54), moderate (n = 64), or severe (n = 36) malaria was studied to determine whether the ability to form rosettes in vitro is correlated with malaria severity. There was a wide distri bution of rosette frequencies within each clinical category; however, a clear trend towards higher rosette frequency with increasing severit y of disease was seen, with the median rosette frequency of the mild-m alaria group (1%; range, 0 to 82%) being significantly lower than thos e of the moderate-malaria group (5%; range, 0 to 45%; Mann-Whitney U t est, P < 0.02) and the severe-malaria group (7%; range, 0 to 97%; Mann -Whitney U test, P < 0.003). Within the severe-malaria category there was no difference in resetting among isolates from cerebral malaria pa tients or those with other forms of severe malaria. We also examined t he ABO blood groups of the patients from whom isolates were obtained a nd found that isolates from group 0 patients (median rosette frequency , 2%; range 0 to 45%) rosetted less well than those from group A (medi an, 7%; range 0 to 82%; Mann-Whitney U test, P < 0.01) or group AB (me dian, 11%; range 0 to 94%; Mann-Whitney U test, P < 0.03). We therefor e confirm that resetting is associated with severe malaria and provide further evidence that rosetting is influenced by ABO blood group type . Whether resetting itself plays a direct role in the pathogenesis of severe malaria or is a marker for some other causal factor remains unk nown.