Abstract:
Phylogenetic relationship of the region II of the P. vivax Duffy Binding Protein gene
(PvdbpII), a prime vaccine candidate against blood stage of vivax malaria, was analysed
between parasite isolates from Sri Lanka and from different geographical areas,
worldwide. A gene tree was derived from the aligned nucleotide sequences of a 672 bp
region, using the Neighbour-Joining method with 1000 bootstrap replicates, the Tamura's
three-parameter distance model as implemented in the MEGA version 4.0 programme.
One hundred and seventy five PvdbpII sequences found in the GenBank were compiled
and compared to 100 Sri Lankan (SL) sequences. The worldwide sequences included those
from the reference Salvador-I strain, single sequences each from Vietnam (VIAT),
Indonesia (INDO) and India (INDI) and 13, 17, 30 and 111 sequences from South Korea
(SK), Colombia (COL), Thailand (Thai) and Papua New Guinea (PNG), respectively.
Twenty three different groups in all were evident in the gene tree. SL isolates were
grouped in 6 different clades (A-G). A majority of these concentrated amongst 3 different
clades (A, B and C), with no clustering detected according to the sample collection sites
within the country. A single clade (D), exclusively contained SL isolates, proving
evidence for geographical isolation. Two other clades (A & F) contained isolates from SL
in combination with THAI and SK, respectively. The close phylogeny of the SL sequences
with world wide ones were more clearly evident in the gene tree by SL isolates grouping
with those from PNG, THAI, COL, INDO and VIAT in clade B, and with those from
PNG, THAI, COL and from INDI with the reference strain Sal-1 in clade E. Interestingly,
both these groups lacked SK isolates. The Sri Lankan PvdbpII sequences thus appeared to
represent a sample from the PvdbpII worldwide genetic diversity, rather than from any
particular lineage
