PMC

Alignment of DBLα domains. A MUSCLE alignment of the predominant gene transcribed by P. falciparum isolates from cerebral malaria and hyperparasitaemia patients. The second half of the expressed sequence tag is shown and the position of the residues that distinguish DBLα0-like domains (cysteines present) from DBLα1-like domains (cysteines missing) are arrowed, and the cysteine residues are boxed. The predominant gene in 8/9 isolates from cerebral malaria patients is of the DBLα1-like type, whereas the predominant gene in 6/8 hyperparasitaemia isolates is of the DBLα0-like type. This difference is significant by Fishers Exact test (P = 0.013). Symbols: (*) indicates conserved residues; (:) indicates conservative substitution; (·) indicates semi-conservative substitution.

Frequencies of distinct DBLα tags in each isolate. The pie charts represent the relative number of different DBLα var gene sequences detected in each isolate by RT-PCR, cloning and analysis of 14–19 mini-prep clones per isolate. The number of sections in each pie represents the number of distinct DBLα tags detected, and the size of each section represents the relative frequency of each DBLα tag. Bracketed numbers indicate the exact number of mini-prep clones sequenced for each isolate. The sample name is in the top left corner of each box and the rosette frequency (percentage of mature infected erythrocytes binding two or more uninfected erythrocytes) in the bottom left corner. White segments represent DBLα1-like var genes (i.e. two conserved cysteine residues in the amplified DBLα tag) whereas grey segments represent DBLα0-like var genes (i.e. four conserved cysteine residues in the amplified DBLα tag).

Phylogenetic network showing relationships between var gene DBLα sequence tags transcribed by P. falciparum isolates, generated using Neighbour-Net . Sequences transcribed by isolates from African children with cerebral malaria (CM, red), hyperparasitaemia (HYP, blue), and uncomplicated malaria (U, green) are compared to a selection of var genes from the laboratory clone 3D7. For the 3D7 genes, the gene name is preceded by A, B, C, BA or BC to indicate the group to which the gene belongs. The sequences fall into two major clades, with the DBLα0-like sequences to the left of the dotted line and the DBLα1-like sequences to the right. For the predominant gene from nine of the Malian isolates, the var gene upstream region was determined by PCR and is indicated as a boxed letter.