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.
