In general, attempts to develop vaccines for pathogens transmitted by arthropods have met with little or no success. It has been widely observed that the saliva of arthropods that transmit disease enhances the infectivity of pathogens the arthropod transmits to the vertebrate host. Indeed, it has been observed that vaccinating against components of the saliva of arthropods or against antigens expressed in the gut of arthropods can protect the host from infection and decrease the viability of the arthropod. These results suggest that multi-subunit vaccines that target the pathogen itself as well as arthropod salivary gland components and arthropod gut antigens may be the most effective at controlling arthropod-borne pathogens as these vaccines would target several facets of the lifecycle of the pathogen. This review covers known immunomodulators in arthropod salivary glands, instances when arthropod saliva has been shown to enhance infection and a limited number of examples of antiarthropod vaccines, with emphasis on three arthropods: sandflies, mosquitoes and hard ticks.

SummaryTrypanosoma cruzi expresses a developmentally regulated neuraminidase (TCNA) implicated in parasite invasion ofcells . We isolated full-length DNA clones encoding TCNA. Sequence analysis demonstrated an open reading frame coding for a polypeptide of 1,162 amino acids. In the N-terminus there is a cysteine-rich domain containing a stretch of 332 amino acids nearly 30% identical to the Clostridium perfringens neuraminidase, three repeat motifs highly conserved in bacterial and viral neuraminidases, and two segments with similarity to the YWTD repeats found in the low density lipoprotein (LDL) receptor and in other vertebrate and invertebrate proteins. This domain is connected by a structure characteristic of type III modules of fibronectin to a long terminal repeat (LTR) consisting of 44 full length copies of twelve amino acids rich (75%) in serine, threonine, and proline. LTR is unusual in that it contains at least 117 potential phosphorylation sites . At the extreme C-terminus is a hydrophobic segment of 35 amino acids, which could mediate anchorage of TCNA to membranes via a glycosylphosphatidylinositol linkage. This is the first time a protozoan protein has been found to contain a YWTD repeat and a fibronectin type III module. The domain structure of TCNA suggests that the enzyme may have functions additional to its catalytic activity such as in protein-protein interaction, which could play a role in T. cruzi binding to host cells.

The potential of Leishmania major culture-derived soluble exogenous antigens (SEAgs) to induce a protective response in susceptible BALB/c mice challenged with L. major promastigotes was investigated. Groups of BALB/c mice were immunized with L. major SEAgs alone, L. major SEAgs coadministered with either alum (aluminum hydroxide gel) or recombinant murine interleukin-12 (rmIL-12), L. major SEAgs coadministered with both alum and rmIL-12, and L. major SEAgs coadministered with Montanide ISA 720. Importantly and surprisingly, the greatest and most consistent protection against challenge with L. major was seen in mice immunized with L. major SEAgs alone, in the absence of any adjuvant. Mice immunized with L. major SEAgs had significantly smaller lesions that at times contained more than 100-fold fewer parasites. When lymphoid cells from L. major SEAg-immunized mice were stimulated with leishmanial antigen in vitro, they proliferated and secreted a mixed profile of type 1 and type 2 cytokines. Finally, analyses with Western blot analyses and antibodies against three surface-expressed and secreted molecules of L. major (lipophosphoglycan, gp46/M2/ PSA-2, and gp63) revealed that two of these molecules are present in L. major SEAgs, lipophosphoglycan and the molecules that associate with it and gp46/M2/PSA-2.

No abstract