Excerpt:

RESULTS: This study
reveals the digestive machinery of the I. ricinus during the course of
blood-feeding on the host. The dynamic profiling of concentrations,
activities and mRNA expressions of the major digestive enzymes demonstrates
that the de novo synthesis of peptidases triggers the dramatic increase of
the hemoglobinolytic activity along the feeding period. Overall
hemoglobinolysis, as well as the activity of digestive peptidases are
negligible at the early stage of feeding, but increase dramatically towards
the end of the slow feeding period, reaching maxima in fully fed ticks. This
finding contradicts the established opinion that blood digestion is reduced
at the end of engorgement.
Furthermore, we show that the digestive proteolysis is localized
intracellularly throughout the whole duration of feeding. 
CONCLUSIONS: Results suggest that the
egressing proteolytic system in the early stage of feeding and digestion is
a potential target for efficient impairment, most likely by blocking its
components via antibodies present in the host blood. Therefore, digestive
enzymes are promising candidates for development of novel ‘anti-tick’
vaccines capable of tick control and even transmission of tick-borne
pathogens.