Tick salivary gland extract inhibits killing of Borrelia afzelii spirochetes by mouse macrophages.

Salivary gland extract (SGE) from Ixodes ricinus ticks inhibited the killing of Borrelia afzelii spirochetes by murine macrophages. SGE also reduced the production of two major defense molecules of phagocytes, superoxide and nitric oxide. It is likely that the suppression of macrophage microbicidal mechanisms contributes to the inhibitory effect of tick saliva on the killing of B. afzelii spirochetes, thus facilitating the transmission of this important pathogen.

Identification of Borrelia burgdorferi sensu stricto, Borrelia garinii and Borrelia afzelii in Ixodes ricinus ticks from southern Bohemia using monoclonal antibodies.

The prevalence of Borrelia burgdorferi sensu lato (s.l.) in 761 Ixodes ricinus ticks collected in different localities of southern Bohemia was investigated. The minimum infection rate of nymphs, males and females as determined by dark-field microscopy was 4.8% in 1997. The total B. burgdorferi prevalence determined in ticks in 1998 was 11.04%. A significant local variability of the prevalence of B. burgdorferi was not found. Nine isolates were identified at a genospecies level by immunoblotting with prepared monoclonal antibodies (Mabs). The most prevalent genospecies in ticks was B. burgdorferi sensu stricto (s.s.) (6 strains). Two tick isolates reacted with Mabs specific to both B. garinii and B. afzelii and one isolate was detected as a mixed culture of B. burgdorferi s.s. and B. garinii. Considerable variability in protein composition among the strains obtained was found to exist. Five B. burgdorferi genospecies-specific Mabs were prepared and used for the identification of spirochaete isolates. Mabs 9B8 and 6C5 reacted with OspA and OspB proteins of B. burgdorferi s.s., while 4D7 and 1D11 recognised OspA protein of B. garinii and 9D2 specifically reacted with the OspB protein of B. afzelii. In addition, Mab 5H4 reacted with flagellin of all the above-mentioned genospecies of B. burgdorferi s.l.

Salivary gland extract from Ixodes ricinus ticks inhibits production of interferon-gamma by the upregulation of interleukin-10.

Tick saliva has been shown to modulate host immunity by a so far unknown mechanism. We have demonstrated an inverted effect of salivary gland extract (SGE), derived from partially fed Ixodes ricinus females, on the production of two cytokines, interferon (IFN)-gamma and interleukin (IL)-10, in vitro. While SGE markedly suppressed the elaboration of IFN-gamma by mouse splenocytes stimulated with lipopolysaccharide (LPS), the production of IL-10 was increased in comparison with SGE-untreated cultures. The suppressive effect of SGE could be abolished by the addition of an IL-10 neutralizing monoclonal antibody to splenocyte cultures. Similar results were obtained when live Borrelia afzelii spirochetes, which are transmitted in Europe by I. ricinus ticks, were used for the cytokine induction. These results suggest that tick saliva can upregulate the IL-10 production at the tick feeding site, which consecutively inhibits the elaboration of pro-inflammatory cytokines, for example IFN-gamma. This immunosuppression may facilitate the establishment of tick-transmitted pathogens in the host.

Suppressive effect of Ixodes ricinus salivary gland extract on mechanisms of natural immunity in vitro.

Tick saliva has been shown to contain a variety of pharmacologically active molecules, including those with immunosuppressive activities. There is increasing evidence that the nonspecific suppression of host immunity by tick saliva is exploited by tick-borne pathogens, e.g. the saliva-activated transmission (SAT) of some tick-borne viruses. We have demonstrated the suppressive effect of the salivary gland extract (SGE) derived from partially fed (five days) Ixodes ricinus females on important mechanisms of innate immunity: natural killer (NK) cells, interferon and nitric oxide production. SGE reduced the interferon induction by polyinosinic-polycytidylic acid (poly I:C) or Escherichia coli lipopolysaccharide (LPS) in a culture of Balb/c mouse splenocytes by 94% and 62%, respectively. SGE suppressed the cytotoxicity of nonstimulated and in vivo poly I:C-stimulated mouse NK cells by up to 31% and 26%, respectively. The induction of NK activity in vitro by LPS but not by Concanavalin-A (Con-A) was also downregulated in the presence of SGE. The addition of SGE to cultures of mouse macrophages partially inhibited the production of nitric oxide, induced by LPS. These data suggest that the facilitating effect of SGE on the transmission of some tick-borne pathogens might be associated with the suppression of the host innate resistance mechanisms, represented by interferon, nitric oxide and NK cells.