Characterization of <em>Phlebotomus papatasi</em> Peritrophins, and the Role of PpPer1 in <em>Leishmania major</em> Survival in its Natural Vector

<div><p>The peritrophic matrix (PM) plays a key role in compartmentalization of the blood meal and as barrier to pathogens in many disease vectors. To establish an infection in sand flies, <i>Leishmania</i> must escape from the endoperitrophic space to prevent excretion with remnants of the blood meal digestion. In spite of the role played regarding <i>Leishmania</i> survival, little is known about sand fly PM molecular components and structural organization. We characterized three peritrophins (PpPer1, PpPer2, and PpPer3) from <i>Phlebotomus papatasi</i>. PpPer1 and PpPer2 display, respectively, four and one chitin-binding domains (CBDs). PpPer3 on the other hand has two CBDs, one mucin-like domain, and a putative domain with hallmarks of a CBD, but with changes in key amino acids. Temporal and spatial expression analyses show that <i>PpPer1</i> is expressed specifically in the female midgut after blood feeding. <i>PpPer2</i> and <i>PpPer3</i> mRNAs were constitutively expressed in midgut and hindgut, with <i>PpPer3</i> also being expressed in Malpighian tubules. <i>PpPer2</i> was the only gene expressed in developmental stages. Interestingly, <i>PpPer1</i> and <i>PpPer3</i> expression are regulated by <i>Le. major</i> infection. Recombinant PpPer1, PpPer2 and PpPer3 were obtained and shown to display similar biochemical profiles as the native; we also show that PpPer1 and PpPer2 are able to bind chitin. Knockdown of <i>PpPer1</i> led to a 44% reduction in protein, which in spite of producing an effect on the percentage of infected sand flies, resulted in a 39% increase of parasite load at 48 h. Our data suggest that PpPer1 is a component for the <i>P. papatasi</i> PM and likely involved in the PM role as barrier against <i>Le. major</i> infection.</p>