Disruption of Ixodes scapularis anticoagulation by using RNA interference

Abstract

Ixodes scapularis ticks transmit many pathogens, including Borrelia burgdorferi, Anaplasma phagocytophilum, and Babesia microti. Vaccines directed against arthropod proteins injected into the host during tick engorgement could prevent numerous infectious diseases. Salp14, a salivary anticoagulant, poses a key target for such intervention. Salp14 is the prototypic member of a family of potential I. scapularis anticoagulants, expressed and secreted in tick saliva during tick feeding. RNA interference was used to assess the role of Salp14 in tick feeding. Salp14 and its paralogs were silenced, as demonstrated by the reduction of mRNA and protein specific for these antigens. Tick salivary glands lacking Salp14 had reduced anticoagulant activity, as revealed by a 60 -80% reduction of anti-factor Xa activity. Silencing the expression of salp14 and its paralogs also reduced the ability of I. scapularis to feed, as demonstrated by a 50 -70% decline in the engorgement weights. Because ticks have several anticoagulants, it is likely that the expression of multiple anticoagulants in I. scapularis saliva would have to be ablated simultaneously to abolish tick feeding. These studies demonstrate that RNA interference can silence I. scapularis genes and disrupt their physiologic function in vivo, and they identify vaccine candidates that can alter vector engorgement.

Tick anti-hemostatics: targets for future vaccines and therapeutics

“…Immunoprecipitation of tick saliva with anti-salp14 antibodies eliminated 87% of the anticoagulant activity [32]. Silencing of salp14 and its paralogues resulted in a 60-80% reduction of FXa activity and a 50-70% decline in engorgement weights of adult female I. sacpularis, thus emphasizing its role during adult tick feeding [33]. By contrast, salp14 silencing in naïve nymphs had no effect on the engorgement weights, suggesting that nymphs and adults feed by different mechanisms [34].…”

A manganese transporter, BB0219 (BmtA), is required for virulence by the Lyme disease spirochete, Borrelia burgdorferi

“…I. scapularis nymphs or larvae (obtained from the Tick Rearing Facility at Oklahoma State University, Stillwater, OK) were artificially infected with various strains of Bb by using a microinjection technique (11,43) or an immersion method (30) (see SI Methods). After infection, ticks were fed to repletion on separate naïve C3H/HeN mice.…”

Gene Silencing of a Cubilin-Related Serine Proteinase from the Hard Tick Haemaphysalis longicornis by RNA Interference

“…The RISC RNA molecules complementary to the mRNAs seem to work as a guide recruiting a ribonuclease that consequently cleaves only specific mRNAs [8,11]. The RNAi process was studied in several eukaryotic organisms including ticks in the past few years by introducing a dsRNA derived from a determined gene sequence in vivo by injecting the dsRNA in the whole organism [1,2,13,17].…”