A recent study on the association between P.
knowlesi genotype and disease progression involved the
analysis of the DNA sequences of Pknbpxa and Pknbpxb
invasion gene candidates to determine whether they were
polymorphic in human infections (Box 1). This was found to
be the case, with Pknbpxa being more diverse than
Pkbnpxb [1]. DNA sequences were then generated from
polymorphic fragments of Pknbpxa and Pknbpxb from
138 and 134 patient isolates, respectively. The researchers
found 12 Pknbpxa DNA sequence groups and two Pknbpxb
groups in the patient cohort. Parasite isolates within each
group had additional polymorphisms that constituted two
or three allelic types. The alleles with matched patient
clinical and laboratory data were analysed and statistically
significant clustering of particular alleles with clinical and
laboratory measures of disease progression was found,
including parasitaemia [1]. This report showed that some
P. knowlesi parasites may be more virulent in the human
host, and that this virulence is associated with certain
parasite genotypes. These findings can now be taken forward
in proof-of-principle testing using in vitro invasion
assays.