Plasmodium falciparum-infected erythrocytes: Agglutination by diverse Kenyan plasma is associated with severe disease and young host age

The variant surface antigens (VSAs) of Plasmodium falciparum-infected red b lood cells are potentially important targets of naturally acquired immunity to malaria. Natural infections induce agglutinating antibodies specific to the VSA variants expressed by the infecting parasites, Previously, when di fferent parasite isolates were tested against a panel of heterologous plasm a from Kenyan children, the proportion of plasma that agglutinated the para sites (the agglutination frequency [AF]) was highly variable among isolates , suggesting the existence of rare and prevalent variants. Here, the AF of 115 isolates from Kenyan children were compared, The results show that the AF of isolates causing severe malaria were significantly higher than those of isolates causing mild malaria; and AF decreased significantly with the i ncreasing age of the infected child. We propose that parasites causing seve re disease tend to express a subset of VSA variants that are preferentially associated with infections of children with low immunity.