Feeding antisera targeting the peritrophic matrix-associated proteins Ppchit1 and PpPer1 interferes with PM kinetics in the sand flies Phlebotomus papatasi and Lutzomyia longipalpis

In female sand flies the peritrophic matrix (PM type 1) is secreted by midgut epithelial cells following blood feeding. When sand flies take an infectious blood meal, for Leishmania to survive and establish within the gut of the flies, they must first escape from the endoperitrophic space and then attach to the midgut epithelia to prevent excretion. It has been shown that RNAi knockdown of PpChit1, a midgut-specific chitinase in Phlebotomus papatasi, leads to a decrease in Le. major load in the gut of the vector. In the present work we assessed PM kinetics in two sand flies, P. papatasi and Lutzomyia longipalpis fed on naïve red blood cells (RBCs) reconstituted with naïve or specific antisera against Ppchit1 and PpPer1, a peritrophin previously characterized from P. papatasi. Sand fly midguts were dissected at 24, 48 and 72h post-blood meal (PBM) and processed for downstream microscopic analyses. Whereas P. papatasi midguts were fixed in 2.5% glutaraldehyde in cacodylate buffer and processed for light and transmission electron (TEM) microscopies, guts obtained from L. longipalpis were processed for light microscopy only. Results indicate that by 24h PBM PMs are thin, becoming significantly thicker by 48h PBM in the two sand flies species fed either on naïve of on RBCs reconstituted with either antisera. At 72h PBM, however, the PM from flies fed on either of the two antisera is still very thick in contrast with those fed on naïve sera, though the lamellate organization appears unchanged. Our results also suggest that feeding with the specific antisera also interfere with the blood digestion, as significantly more undigested blood is still present in the midgut 72h PBM in L. longipalpis in comparison to individuals fed on naïve sera. Collectively, antibodies targeting Ppchit1 and PpPer1 can interfere with the PM kinetics, blood digestion, and parasite survival are currently being tested as potential of transmission blocking vaccines.