Klíšťata sají obrovské množství krve, která je jejich jediným zdrojem živin a energie. Přesný enzymatický mechanismus zpracování krve ve střevě klíšťat však kupodivu nebyl donedávna vůbec znám. Náš komplexní molekulární model trávení hostitelského hemoglobinu u klíštěte obecného (Ixodes ricinus) poprvé odhalil analogii enzymatického aparátu s krevsajícími ploštěnci a hlísticemi, a zároveň tato znalost představuje zásadní poznatek pro účinný boj s klíšťaty a jimi přenášenými patogeny., Ticks (in this case Ixodidae and Argasidae) feed on enormous amounts of host blood, which provides their ultimate source of energy and nutrients. There has been only limited evidence on the exact molecular mechanisms of blood digestion in ticks. For the first time, our complex enzymatic model of proteolytic digestion in the Common Tick (Ixodes ricinus) reveals the analogy of tick intestinal proteolysis with bloodfeeding platyhelminthes and nematodes and presents a future application potential in tick or tick-borne pathogen interventions., and Daniel Sojka.
Saliva-activated transmission (SAT) of Borrelia burgdorferi sensu stricto was demonstrated using real-time PCR and salivary gland extract (SGE) from partially fed Ixodes ricinus ticks. C3H/HeN mice were injected intradermally with 1.5 × 103 spirochetes mixed with 40 µg of SGE per mouse. The control group was inoculated with the same dose of spirochetes without SGE. The accelerating effect of SGE on spirochete proliferation was demonstrated on day 1 post infection, when a 4.2-fold increase in spirochetes was found in the skin and a 10-fold increase in the blood, compared with control mice. The data represent the first direct evidence of a SAT effect of I. ricinus SGE on infection with the Lyme disease agent B. burgdorferi.
Previous studies have demonstrated that both tick saliva and Borrelia burgdorferi sensu lato antigens modulate the cytokine response of the host. In this paper, the effect of salivary gland extract (SGE) from Ixodes ricinus (L., 1758) ticks on cytokine production by primary cultures of mouse epidermal cells stimulated with Borrelia afzelii Canica, Nato, du Merle, Mazie, Baranton et Postic, 1993 spirochetes was analysed. Epidermal cells were derived from C3H/HeN mice, susceptible to Lyme disease, and BALB/c mice, which are resistant. In cultures from C3H/HeN mice, SGE down regulated production of tumour necrosis factor alpha (TNF-α) and up regulated Th2 cytokine, interleukin 4 (IL-4). Cultures from BALB/c mice produced higher basal levels of monitored cytokines, but their production was affected by SGE a different way. While Th2 cytokines IL-6 and IL-10 were down regulated, the effect on TNF-α and IL-4 was ambiguous. These results indicate that the effect of tick saliva on the epidermal cells of Lyme disease-susceptible C3H/HeN mice mirrors its effect on other cells of the immune system.
Ixodid ticks remain attached to their hosts for several days to weeks. During this extended feeding process new proteins involved in the modulation of host immune responses are expressed in tick salivary glands. In our study a stimulatory or inhibitory effect of salivary gland extracts (SGE) of unfed and partially fed female Ixodes ricinus (Linnaeus, 1758), female and male Amblyomma variegatum (Fabricius, 1794) and Rhipicephalus appendiculatus Neumann, 1901 ticks on human lymphocyte proliferation induced by Concanavalin A (ConA) and phytohaemagglutinin (PHA), respectively, was investigated. SGE of all female ticks examined suppressed proliferation of ConA-induced lymphocytes; highly significant suppression was observed in the presence of unfed I. ricinus and 9-day fed A. variegatum SGE. SGE of partially fed A. variegatum and I. ricinus females suppressed PHA responses of lymphocytes. Lymphocytes showed reduced PHA and ConA responses in the presence of SGE of unfed and 2-day fed R. appendiculatus females, while SGE of 6-day fed females enhanced PHA responses, but reduced their ConA responses; generally SGE of 2-day fed females displayed the strongest inhibition. Amblyomma variegatum male SGE slightly enhanced PHA, but significantly reduced ConA responses of lymphocytes and their inhibitory effect increased during feeding. SGE of unfed and 2-day fed R. appendiculatus males enhanced PHA and ConA responses and those of 6-day fed males suppressed lymphocyte proliferation. The results suggest that (i) species- and sex-specific differences exist in the effects of tick salivary gland antigens on human lymphocyte proliferation and (ii) effect of SGE on human lymphocyte responses to mitogens varies depending on the tick feeding status.
A total of 7210 unfed adult Ixodes persulcatus Schulze, 1930 and I. ricinus (L., 1758) ticks were collected from the vegetation by flagging in 35 study sites located in the zone of their sympatry (mainly in Leningrad region, Russia). Borrelia infection in ticks was estimated by the dark-field microscopic analysis of gut contents in standard vital preparations at a magnification of ×600. No correlation was revealed between the series of parameters characterising the abundance of each tick species (τ = -0.13) and between the series of these parameters and the prevalence of Borrelia in each vector. It is concluded that in the broad zone of I. persulcatus and I. ricinus sympatry, the presence and proportion of one vector in the ecosystem does not have any significant effect on the extensity of infection and on the epizootic and epidemic significance of the other vector. Each tick species has its independent (of the other species) and relatively original functional role in the focal ecosystem.
Saliva-activated transmission of Borrelia afzelii Canica, Nato, du Merle, Mazie, Baranton et Postic, 1993 was demonstrated using salivary gland extract (SGE) from Ixodes ricinus (L., 1758) ticks and C3H mice. Injection of Borrelia spirochaetes together with SGE increased the level of bacteraemia and accelerated the appearance of bacteria in the urinary bladder, compared with the injection of spirochaetes alone. More I. ricinus nymphs became infected when feeding on mice inoculated with B. afzelii plus SGE. Analysis of cytokines produced by cells of draining lymph nodes from SGE-treated mice showed a suppression of proinflammatory cytokines IFN-γ, IL-6 and GM-CSF following a transient upregulation in comparison with the control mice infected without SGE.
A previously reported procedure for the introduction of Borrelia spirochetes into tick larvae by immersion in a suspension of spirochetes was tested on Ixodes ricinus (L.) ticks and three of the most medically important European Borrelia genomic species, B. burgdorferi sensu stricto, B. garinii and B. afzelii. The procedure was compared with ''classical'' infection of nymphs by feeding on infected mice. Both methods yielded comparable results (infection rate 44-65%) with the exception of B. afzelii, which produced better results using the immersion method (44%) compared with feeding on infected mice (16%). Nymphs infected by the immersion method at the larval stage were able to transmit the infection to naïve mice as shown by serology and PCR detection of spirochetal DNA in organs. The immersion method is faster than feeding on infected mice and provides more reproducible conditions for infection. It can be exploited for studies on both pathogen transmission and Borrelia-vector interactions.