Interaction of tick saliva with the host immune mechanisms and its significance for pathogen transmission

N. Fuchsberger 1 , P.Kocáková 1 , V.Hajnická 2 , M. Slovák 3 , M. Labuda 3 & P.A. Nuttall 4

1 Inst. Virology, Slovak Acad. Sci., 842 45 Bratislava, Slovakia; 2 Institute of Preventive and Clinical Medicine, Limbova 14, 83301 Bratislava, Slovakia; 3 Institute of Zoology, Slovak Academy of Sciences, Dubravska 9, 84306 Bratislava, Slovakia; 4 CEH Institute of Virology and Environmental Microbiology, Oxford, OX1 3SR United Kingdom

Ticks are of great medical and veterinary importance not only as haematophagous ectoparasites infesting humans and domestic animals, but also as vectors of a wide variety of pathogenic organisms. Ixodid ticks are obligate blood-feeders in all their life stages. In contrast to other haematophagous parasites, the contact between an ixodid tick and its host lasts for days or even weeks. During the prolonged feeding period, the salivary glands increases in protein content. Feeding provokes host haemostatic, inflammatory and immune responses. Therefore, ticks counterattack with anti-haemostatic, anti-inflammatory and immunomodulatory substances. We demonstrate the differences in protein patterns of different tick species (Ixodes ricinus, Haemaphysalis inermis, Dermacentor reticulatus, Rhipicephalus appendiculatus, Amblyomma variegatum), differences in patterns at different stages of feeding, differences between sexes and collaboration of both sexes during feeding. The salivary glands are also the primary means for transmission of tick-borne pathogens. Such pathogens exploit the immunomodulatory activities of tick saliva. This phenomenon is known as Saliva activated transmission (SAT). We demonstrate the promotion of virus growth by tick SGE in an animal-free system. We demonstrate the interaction of tick SGE with host immune mechanisms namely with the interferon system, with natural killer cells, and with chemotaxis. We demonstrate the interaction of tick saliva with the host cytokine network at the levels of both production and action.

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