Identification and Characterization of Putative Secreted Proteins from the Adult-Stage Hookworm, Ancylostoma caninum
Open AccessSecretions from the adult-stage hookworm that mediate the host-parasite interactions have been partially identified. The proteins injected into the host during hookworm parasitism are unknown. We hypothesize that the hookworm secretions potentially injected into the host are found in the anterior secretory glands of the worm. We used a de novo transcriptomic approach to identify the transcripts expressed in the anterior secretory glands of the adult-stage hookworm, Ancylostoma caninum, a model for human hookworm Necator americanus. We isolated the anterior regions, created a SMART cDNA library, and randomly sequenced 2,162 clones using Sanger-based cycle sequencing. We found 159 transcripts coding putative secreted proteins from seventeen functional groups. We identified venom allergens, anticoagulants, Kaliseptin like ShK toxins, tissue inhibitor of metalloproteases, C type lectins, antioxidants, proteases, signaling proteins, phospholipase A2, deoxiribonuclease II, Kunitz inhibitor, antimicrobial peptide, and transthyretin like protein coded in the library. These findings suggest that the anterior secretory glands of the parasitic hookworm are the source of parasitic proteins important for the host-parasite interactions.One of the most abundant proteins secreted at the host-parasite interface, a putative tissue inhibitor of metalloproteases, AcTMP1, has immunosuppressive activity, but its biochemical mechanism for immunosuppression has not been determined. Our goal was to identify a biochemical function for AcTMP1 using functional genomics approaches. We found that recombinant AcTMP1 is a weak competitive inhibitor of matrix metalloproteases (MMP14, MMP13, and MMP8). AcTMP1 uses the classical cysteine switch inhibition mechanism. The IC50 of rAcTMP1 with MMP14 is 100 nM, ten fold less potent compared with human TIMP2, an inhibitor of MMP14. Recombinant AcTMP1 had no anticomplement activity, and binds <α>a3 <β>b1 integrin in vitro. These results suggest that the hookworm AcTMP1 is a multifunctional protein. AcTMP1 may be exerting it immunosuppressive effect by binding integrin in the surface of dendritic cells. Moreover, the putative proliferative function of AcTMP1suggests a novel immunosuppressive mechanism at the hookworm attachment site. This research provides a new perspective on the potential mechanisms used by hookworm to evade the host immune response and provides additional vaccine targets against the hookworm, and potential therapies for the treatment of autoimmune diseases, and thrombic disorders.
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