Effect of mouse antisera targeting the Phlebotomus papatasi midgut chitinase PpChit1 on sandfly physiology and fitness

Abstract

In sandflies, the absence of the peritrophic matrix (PM) affects the rate of blood digestion. Also, the kinetics of PM secretion varies according to species. We previously characterised PpChit1, a midgut-specific chitinase secreted in Phlebotomus papatasi (PPIS) that is involved in the maturation of the PM and showed that antibodies against PpChit1 reduce the chitinolytic activity in the midgut of several sandfly species. Here, sandflies were fed on red blood cells reconstituted with naïve or anti-PpChit1 sera and assessed for fitness parameters that included blood digestion, oviposition onset, number of eggs laid, egg bouts, average number of eggs per bout and survival. In PPIS, anti-PpChit1 led to a one-day delay in the onset of egg laying, with flies surviving three days longer compared to the control group. Anti-PpChit1 also had a negative effect on overall ability of flies to lay eggs, as several gravid females from all three species were unable to lay any eggs despite having lived longer than control flies. Whereas the longer survival might be associated with improved haeme scavenging ability by the PM, the inability of females to lay eggs is possibly linked to changes in PM permeability affecting nutrient absorption.

Arbovirosis and potential transmission blocking vaccines

“…Secures ticks mouth parts during blood feeding [ 136 , 137 ] Reduces vector-host contact. Induces death of blood feed ticks No Bm-86 Rhipicephalus microplus Midgut antigen [ 131 , 134 ] Reduces blood uptake and vector-host contact Yes PpChit-1 Phlebotomus papatasi Aids maturation of peritrophic matrix [ 159 ] Reduced sand fly life span and fecundity No …”

“…This protein is involved in the maturation of the peritrophic matrix (PM), which is of pivotal importance in blood digestion [ 157 ]. Previous studies show that antibodies against this protein also cross-react with other midgut proteins from different Phlebotomus species [ 159 ]. Most importantly, treatment with antibodies against PpChit-1 negatively impacts the ability of sandflies to lay eggs.…”

“…This is potentially caused by PM permeability changes induced by the attaching antibodies. These changes affect nutrient absorption and egg development [ 159 ].…”

Alternative splicing originates different domain structure organization of Lutzomyia longipalpis chitinases

“…As in other hematophagous insects, female sand flies form a peritrophic matrix (PM) around the blood bolus after feeding. The importance of this PM was demonstrated in Phlebotomus papatasi flies fed with blood containing an anti-chitinase antibody that led to delay in the onset of egg laying, but longer survival, which might be due to the haeme scavenging capacity of the PM ( Robles-Murguia et al 2014 ). Also in the Old World vector, when this chitinase gene was silenced there was a decreased infection with Leishmania major , indicating the importance of the PM biogenesis for successful parasite development ( Coutinho-Abreu et al.…”

“…Feeding exogenous chitinase to female L. longipalpis can reduce fecundity ( Araujo et al 2012 ) and chitinase blocking by specific antibody has a deleterious effect on the insect fitness ( Robles-Murguia et al 2014 ). This shows that chitinases are tuned in order to keep the sand fly balanced physiology.…”