Sialogenins and immunomodulators derived from blood feeding parasites

Abstract

Several molecules and cell types constitute the innate or natural and the acquired or adaptive arms of the immune response. The innate arm represents the first line of host defense while the acquired arm develops upon recurring contact with the parasites and promotes long-lasting responses and immunological memory. When attempting to intake a blood meal, hematophagous parasites may face the immune system of their vertebrate hosts. In order to counteract the host immune protective barriers and facilitate their feeding, these organisms developed, throughout the evolutionary process, a salivary cocktail with an arsenal of molecules containing several immunomodulatory properties. Advances in biochemical techniques and molecular biology tools made the genome sequencing and the development of sialome catalogs possible, allowing the identification and study of each salivary component. In consequence, an increasing number of immunologists and immunoparasitologists are now focusing their efforts on unveiling the biological role of these molecules and contributing to the creation of a database representing the salivary immunome of blood feeding organisms. Thus, the present chapter illustrates the current knowledge of proteins, here termed sialogenins (from the Greek sialo: saliva; gen: origin; in: protein), and nonprotein constituents present in the salivary secretion employed by bloodsucking ectoparasites to circumvent such effector mechanisms of host immunity. Also presented is an updated list of complement system and chemokine inhibitors, histamine- and immunoglobulin-binding proteins, and modulators of host cell activation and function described in saliva or salivary gland extract of hematophagous ectoparasites.