Sandflies (
Diptera Psychodidae) are important
disease vectors of
parasites of the genus
Leishmania, as well as
bacteria and
viruses. Following studies of the midgut
transcriptome of
Phlebotomus papatasi, the principal vector of
Leishmania major, two non-classical Kazal-type
serine proteinase inhibitors were identified (PpKzl1 and PpKzl2). Analyses of expression profiles indicated that PpKzl1 and PpKzl2 transcripts are both regulated by
blood-
feeding in the midgut of P. papatasi and are also expressed in
males,
larva and
pupa. We expressed a recombinant PpKzl2 in a mammalian expression system (CHO-S free style
cells) that was applied to
in vitro studies to assess
serine proteinase inhibition. Recombinant PpKzl2 inhibited α-
chymotrypsin to 9.4% residual activity and also inhibited α-
thrombin and
trypsin to 33.5% and 63.9% residual activity, suggesting that native PpKzl2 is an active
serine proteinase inhibitor and likely involved in regulating digestive
enzymes in the midgut. Early stages of
Leishmania are susceptible to
killing by digestive
proteinases in the
sandfly midgut. Thus, characterising
serine proteinase inhibitors may provide new targets and
strategies to prevent
transmission of
Leishmania.