Effects of haemagglutination (lectin) inhibitory sugars on Theileria parva infection in Rhipicephalus appendiculatus

Immune functions of C-type lectins in medical arthropods

C-type lectins (CTLs) are a family of proteins that contain 1 or more carbohydrate-recognition domains (CRDs) and bind to a broad repertoire of ligands in the presence of calcium ions. CTLs play important roles in innate immune defenses against microorganisms by acting as pattern-recognition receptors (PRRs) for invading pathogens, such as bacteria, viruses, and parasites. After binding to pathogen-associated ligands, CTLs mediate immune responses, such as agglutination, phagocytosis, and the activation of phenol oxidase progenitors, thereby clearing pathogens. CTLs are an evolutionarily conserved family found in almost all vertebrates and invertebrates. Medical arthropods can acquire and transmit a range pathogens through various approaches, such as bloodsucking, lancing, and parasitism, thus infecting humans and animals with related diseases, some of which can be life-threatening. Recent studies have shown that lectins are important components of the arthropod immune system and are essential for the immune responses of arthropods to arthropod-borne pathogens. This article reviews the current understanding of the structure, function, and signaling pathways involved in CTLs derived from important medical arthropods.

Tick lectins: structural and functional properties

Few papers have been published on tick lectins so far, and therefore more data are needed to complete the mosaic of knowledge of their structural and functional properties. Tissue-specific lectin/haemagglutinin activities of both soft and hard ticks have been investigated. Some tick lectins are proteins with binding affinity for sialic acid, various derivatives of hexosamines and different glycoconjugates. Most tick lectin/haemagglutinin activities are blood meal enhanced, and could serve as molecular factors of self/non-self recognition in defence reactions against bacteria or fungi, as well as in pathogen/parasite transmission. Dorin M, the plasma lectin of Ornithodoros moubata, is the first tick lectin purified so far from tick haemolymph, and the first that has been fully characterized. Partial characterization of other tick lectins/haemagglutinins has been performed mainly with respect to their carbohydrate binding specificities and immunochemical features.

Lyme borreliosis: insights into tick-/host-borrelia relations

Lyme borreliosis (LB) is a serious infectious disease of humans and some domestic animals in temperate regions of the Northern Hemisphere. It is caused by certain spirochetes in the Borrelia burgdorferi sensu lato (s.l.) species complex. The complex consists of 11 species (genospecies). Borrelia burgdorferi sensu stricto (s.s.), Borrelia garinii and Borrelia afzelii are the major agents of human disease. Borrelia burgdorferi s.l. species are transmitted mainly by ticks belonging to the Ixodes ricinus species complex plus a few additional species not currently assigned to the complex. B. burgdorferi infections may produce an acute or chronic disease with a wide array of clinical symptoms such as erythema migrans (EM), carditis, arthritis, neuroborreliosis, and acrodermatitis chronica atrophicans (ACA). Differences in LB spirochetes 'genospecies' and strains/isolates determine the occurrence and severity of this multi-system disease. Accurate and reliable identification of the LB spirochetes in ticks as well as knowledge of their prevalence are essential for prevention against the disease and development of an effective vaccine. An overview of the knowledge of molecular factors with emphasis on potential protein-carbohydrate interactions in the tick-borrelia system is the main focus of this review.