Elucidating the Role of Reprolysin Metalloproteases in Amblyomma americanum

Background: Ticks, an obligate ecto-parasite of terrestrial vertebrates, have evolved a specialized complex cocktail of compounds secreted as saliva to assist in blood feeding by interfering with host responses including haemostatic and host immune response. Nicknamed the “lone star tick”, A. americanum is a competent vector for the transmission of a number of human diseases as well as this tick has been linked with an emerging syndrome known as Red Meat allergy, signifying the significance of understanding the role of tick saliva. Tick salivary metalloprotease have been associated with a variety of activities including fibrin(ogen)olytic activity and disaggregation of platelets.

 Methods/Findings: Five Reprolysin Salivary MPs were identified in an A. americanum transcriptome. Total RNA was isolated from female A.americanum ticks and was subjected to Temporal Gene Expression for further understanding of their role throughout tick feeding time points. In addition, the sequence homology between the Reprolysin MPs allowed for a Family RNAi Knockdown to further elucidate their role in tick feeding. Reduction in tick weight as well as egg hatching has further validated the importance of Reprolysin Metalloproteases in A. americanum tick feeding.

 Conclusion/Significance: The data acquired by Temporal Gene Expression and qRT-PCR showed differential expression of the each metalloproteases throughout various tick feeding time points and RNAi Knockdown significant phenotypic changes. Identifying salivary molecules important for tick-host interactions allows for a better understanding of tick physiology and could open new targets for anti-tick vaccines.