Bernard Rutti

Th2 polarization of the immune response of BALB/c mice to Ixodes ricinus instars, importance of several antigens in activation of specific Th2 subpopulations

BALB/c mice were infested with Ixodes ricinus larvae, nymphs or adults. Expression of IL‐4 and IFN‐γ mRNA in axillary and brachial draining lymph node cells were measured by competitive quantitative reverse transcription‐polymerase chain reaction 9 days after the beginning of primary‐infestation. IL‐4 mRNA was always higher than that of IFN‐γ mRNA for all tick instars. Moreover, IL‐4 mRNA expression progressively increased during nymphal primary‐infestation with a high burst of expression 7 days after the beginning of infestation. No evolution of IFN‐γ mRNA expression was detected. Draining lymph node cells of infested BALB/c produced higher level of IL‐4 than IFN‐γ following in vitro restimulation with adult tick saliva, salivary gland extract (SGE) or with five selected different chromatographic fractions of SGE. Anti‐tick IgG1 antibodies but no IgG2a were detected in BALB/c pluri‐infested with I. ricinus nymphs, which confirmed the Th2 polarization of the immune response.

Immunosuppressive effects of Ixodes ricinus tick saliva or salivary gland extracts on innate and acquired immune response of BALB/c mice

Abstract. Saliva and salivary gland extract (SGE) of Ixodes ricinus ticks have suppressive effects on the innate immune response of BALB/c mice. Tick saliva prevents hemolysis of sheep red blood cells (SRBC) by the human alternative pathway of complement. The adaptive immune response is also modulated by tick antigens (saliva or SGE). When stimulated in vitro with increasing doses of tick antigens, the proliferation and IL-4 production of draining lymph node T cells of mice infested with nymphal ticks increase, peak and then decrease. These results indicate that immunostimulative and immunosuppressive molecules have competing effects in tick saliva or in SGE. I. ricinus saliva inhibits, in a dose-dependent manner, splenic T cell proliferation in response to concanavalin A (ConA). Tick SGE or saliva injected intraperitoneally to BALB/c mice simultaneously with SRBC systemically immunosuppress the anti-SRBC response as shown in vitro by the reduced responsiveness of sensitized splenic T cells to restimulation with SRBC. In brief some components of SGE or tick saliva reduce the responsiveness of draining lymph node T cells and of sensitized splenic T cells in vitro. The responsiveness of naive splenic T cells to ConA stimulation in vitro is also decreased by tick saliva. Modulation of host responses by tick antigens may facilitate tick feeding, transmission and the propagation of pathogens.

Susceptibility of BALB/c mice to nymphs and larvae of Ixodes ricinus after modulation of IgE production with anti-interleukin-4 or anti-interferon-γ monoclonal antibodies

BALB/c mice infested three times with nymphs or larvae of Ixdoes ricinus ticks do not acquire resistance as assessed by evaluation of both tick attachment and the weight of engorged nymphs or larvae. Tick challenge causes a gradual increase in total IgE antibody production from the first to the third infestation. Anti-tick IgG antibodies are never detected. When the mice are treated with anti-interleukin-4 (anti-IL-4) or anti-interferon-gamma (anti-IFN-γ) monoclonal antibodies (mAbs) 1 day before each infestation, they produce fewer or more IgE antibodies, respectively. No effect is observed on IgG antibodies. In IL-4-deficient mice, no IgE or IgG antibody is produced. However, these treatments and the use of IL-4-deficient mice have no negative effect on either tick attachment or the weight of engorged nymphs or larvae. Treatment with anti-IL-4 mAb and the use of IL-4-deficient mice inhibits and abolishes the switching of IgE, respectively, but these are apparently not sufficient to shift the response toward Th1 cells.

Cytokines (IL-4 and IFN-γ) and antibodies (IgE and IgG2a) produced in mice infected with Borrelia burgdorferi sensu stricto via nymphs of Ixodes ricinus ticks or syringe inoculations

Abstract Mice were tolerant to tick bites during three infestations with nymphs of Ixodes ricinus infected with Borrelia burgdorferi sensu stricto. To determine whether tick bites influence the immune response against B. burgdorferi, we examined the production of cytokines IL-4 and IFN-γ by lymph node cells of BALB/c mice and IL-4 deficient BALB/c mice after tick inoculation versus syringe inoculation of B. burgdorferi. We also measured IgG2a anti-borrelial antibodies and total IgE in these mice. Results showed that BALB/c mice developed a Th2 immune response against B. burgdorferi after tick inoculation and a mixed Th1/Th2 response after syringe inoculation of B. burgdorferi. IL-4 deficient mice produced a Th1 immune response in both cases. IL-4 produced following tick bites greatly decreased the production of anti-borrelial IgG2a antibodies by comparison with the production of anti-borrelial IgG2a antibodies produced following syringe injection of B. burgdorferi.

Influence of the genetic background and parasite load of mice on the immune response developed against nymphs of Ixodes ricinus.

Abstract The immune response of BALB/c (H-2d), DBA (H-2d), C57BL/6 (H-2b), C3H (H-2k), CBA (H-2k), SJL (H-2s), and FVB (H-2q) mice infested once with 15 nymphs of Ixodes ricinus is polarized toward Th2 as suggested by cytokines produced by lymph node cells stimulated with concanavalin A. The parasite load does not influence the polarization of the immune response as observed in BALB/c mice, which developed a Th2 response when infested with 5 or 45 nymphs. As assessed by attachment and weights of engorged nymphs, no resistance was acquired by BALB/c, C57BL/6, or C3H mice undergoing three successive infestations. However, these mice produced a gradual increase in IgE.

Repetitive detection by immunoblotting of an integumental 25-kDa antigen in Ixodes ricinus and a corresponding 20-kDa antigen in Rhipicephalus appendiculatus with sera of pluriinfested mice and rabbits

Mice were pluriinfested with nymphs and rabbits, with adultIxodes ricinus. As determined by immunoblotting, >50% of sera from these animals reacted against a tick antigen with a molecular weight of 25 kDa, which was detected in total extracts of partially fedI. ricinus females and in tick integumental extract. It was also found in engorged nymphs but was absent from larvae. Sera ofI. ricinus-infested rabbits and mice or of rabbits infested withRhipicephalus appendiculatus adults reacted with a 20-kDa antigen in total extracts of partially fedR. appendiculatus females and the integument of this species.

Identification of an Ixodes ricinus salivary gland fraction through its ability to stimulate CD4 T cells present in BALB/c mice lymph nodes draining the tick fixation site

BALB/c mice infested with larvae or nymphs of Ixodes ricinus develop in their lymph nodes a T cell-specific immune response triggered by salivary gland soluble antigens (SGA). SGA are apparently conserved in the 3 biological stages of I. ricinus ticks and are species specific. SGA derived from partially fed females I. ricinus stimulate lymph node T cells from mice infested with I. ricinus larvae or nymphs. In contrast, lymph node cells from mice infested with Amblyomma hebraeum nymphs do not respond. A chromatographic fraction enriched with a 65 kDa protein (IrSG65) isolated from salivary glands of I. ricinus partially fed females induces in vitro a specific T cell proliferation of lymph node cells from mice infested with I. ricinus nymphs. The depletion of CD4+ T cells drastically reduces the ability of lymphocytes from infested mice to proliferate after IrSG65 stimulation.

Induction of host resistance to Rhipicephalus appendiculatus in rabbits: effects of immunizing with detergent-solubilized tick tissue proteins.

Resistance to the hard tick,Rhipicephalus appendiculatus, was induced in rabbits by immunizing them with tick tissue proteins extracted with a detergent, Triton X-100. There was 25% mortality in female ticks fed on immunized rabbits as compared with those fed on controls. Similarly, there was a 40% and 60% reduction in the engorged weight and the weight of egg batches, respectively, of ticks fed on immunized rabbits. Western blot analysis of detergent-solubilized tick tissue Western blot analysis of detergent-solubilized tick tissue proteins, carried out using immune sera, recognized a complex pattern of proteins. A strong reaction was observed with proteins with apparent molecular weights of 94000 and 40000 daltons.