Efforts to describe toxins from the two major families of venomous snakes (Viperidae and Elapidae) usually reveal proteins belonging to few structural types, particular of each family. Here we carried on an effort to determine uncommon cDNAs that represent possible new toxins from Lachesis muta (Viperidae). In addition to nine classes of typical toxins, atypical molecules never observed in the hundreds of Viperidae snakes studied so far are highly expressed: a diverging C-type lectin that is related to Viperidae toxins but appears to be independently originated; an ohanin-like toxin, which would be the third member of the most recently described class of Elapidae toxins, related to human butyrophilin and B30.2 proteins; and a 3FTx-like toxin, a new member of the widely studied three-finger family of proteins, which includes major Elapidae neurotoxins and CD59 antigen. The presence of these common and uncommon molecules suggests that the repertoire of toxins could be more conserved between families than has been considered, and their features indicate a dynamic process of venom evolution through molecular mechanisms, such as multiple recruitments of important scaffolds and domain exchange between paralogs, always keeping a minimalist nature in most toxin structures in opposition to their nontoxin counterparts.

Immunodeficiency disorders and autoimmune diseases are common, but a lack of effective targeted drugs and the side-effects of existing drugs have stimulated interest in finding therapeutic alternatives. Naturally derived substances are a recognized source of novel drugs, and tick saliva is increasingly recognized as a rich source of bioactive molecules with specific functions. Ticks use their saliva to overcome the innate and adaptive host immune systems. Their saliva is a rich cocktail of molecules including proteins, peptides, lipid derivatives, and recently discovered non-coding RNAs that inhibit or modulate vertebrate immune reactions. A number of tick saliva and/or salivary gland molecules have been characterized and shown to be promising candidates for drug development for vertebrate immune diseases. However, further validation of these molecules at the molecular, cellular, and organism levels is now required to progress lead candidates to clinical testing. In this paper, we review the data on the immuno-pharmacological aspects of tick salivary compounds characterized in vitro and/or in vivo and present recent findings on non-coding RNAs that might be exploitable as immunomodulatory therapies.

The salivary complex of the leech Haementeria depressa produces potent anticoagulant components. Among them, a protein named lefaxin inhibits factor Xa (FXa). Lefaxin was purified to homogeneity from dissected salivary complexes by gel filtration in Sephadex G-150 followed by two ion exchange chromatography steps in Mono-Q. Inhibition of FXa by lefaxin was demonstrated by the inhibition of its amidolytic activity, measured with chromogenic substrate S-2765 (apparent K_I of 4 nM), and of its ability to inhibit thrombin generation in the prothrombinase complex (EC₅₀ of 40 nM). Lefaxin has a molecular weight of 30 kDa and an isoelectric point of 5.7. It is made of a polypeptide chain whose N-terminal sequence shows no similarity with that of other FXa inhibitors (antistasin and ghilianten) isolated from leech saliva. On the other hand, the N-terminal sequence of lefaxin presents significant sequence similarity with nitric oxide carrier proteins myohemerythrin from the annelid Nereis diversicolor and prolixin S from the tick Rhodnius prolixus. Interestingly, prolixin S also proved to be an anticoagulant protein acting on FXa. ^* Present address: Dr. N. Duval, Unité de Neurovirologie et Régénération du Système Nerveux, Institut Pasteur, Paris, France

The hard tick Hyalomma dromedarii is one of the most injurious ectoparasites affecting camels and apparently best adapted to deserts. As long-term blood feeders, ticks are threatened by host defense system compounds that can cause them to be rejected and, ultimately, to die. However, their saliva contains a cocktail of bioactive molecules that enables them to succeed in taking their blood meal. A recent sialotranscriptomic study uncovered the complexity of the salivary composition of the tick H. dromedarii and provided a database for a proteomic analysis. We carried out a proteomic-informed by transcriptomic (PIT) to identify proteins in salivary glands of both genders of this tick species. We reported the array of 1111 proteins identified in the salivary glands of H. dromedarii ticks. Only 24% of the proteins were shared by both genders, and concur with the previously described sialotranscriptome complexity. The comparative analysis of the salivary glands of both genders did not reveal any great differences in the number or class of proteins expressed their enzymatic composition or functional classification. Indeed, few proteins in the entire proteome matched those predicted from the transcriptome while others corresponded to other proteins of other tick species. This investigation represents the first proteomic study of H. dromedarii salivary glands. Our results shed light on the differences between the composition of H. dromedarii male and female salivary glands, thus enabling us to better understand the gender-specific strategy to feed successfully.