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Brossard, Michel

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Brossard, Michel
Affiliation principale
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https://libra.unine.ch/handle/123456789/308

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  • Publication
    Accès libre
    Isolation of Ixodes ricinus salivary gland mRNA encoding factors induced during blood feeding
    (2002)
    Leboulle, Gérard
    ;
    Rochez, Candice
    ;
    Louahed, Jamila
    ;
    Rutti, Bernard
    ;
    Brossard, Michel 
    ;
    Bollen, Alex
    ;
    Godfroid, Edmond
    In tick salivary glands, genes induced during blood feeding result in the expression of new proteins secreted into tick saliva. These proteins are potentially involved in modulation of vertebrate host immune and hemostatic responses. In this study, subtractive and full-length cDNA libraries were constructed by use of mRNA extracted from salivary glands of unfed and 5-day engorged Ixodes ricinus. Sequences from these 2 libraries were compared with European Molecular Biology Laboratory (EMBL)/GenBank databases, which led to their classification into 2 major groups. The first group comprises cDNAs that failed to match or showed low homology to genes of known function. The second group includes sequences that showed high homology to genes of known function--for example, anticoagulants, inhibitors of platelet aggregation, and immunomodulatory proteins. Analyses of corresponding proteins suggest that they may be secreted by salivary gland cells. To study the properties of the recombinant proteins, selected cDNAs were expressed in mammalian or bacterial systems.
  • Publication
    Accès libre
    Immunosuppressive effects of Ixodes ricinus tick saliva or salivary gland extracts on innate and acquired immune response of BALB/c mice
    (2001)
    Mejri, Naceur
    ;
    Rutti, Bernard
    ;
    Brossard, Michel 
    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.
  • Publication
    Accès libre
    Th2 polarization of the immune response of BALB/c mice to Ixodes ricinus instars, importance of several antigens in activation of specific Th2 subpopulations
    (2001)
    Mejri, Naceur
    ;
    Franscini, Nicola
    ;
    Rutti, Bernard
    ;
    Brossard, Michel 
    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.
  • Publication
    Accès libre
    PCR Detection of Granulocytic Ehrlichiae in Ixodes ricinus Ticks and Wild Small Mammals in Western Switzerland
    (2000)
    Liz, Jorge S.
    ;
    Anderes, Laurence
    ;
    Sumner, John W.
    ;
    Massung, Robert F.
    ;
    Gern, Lise 
    ;
    Rutti, Bernard
    ;
    Brossard, Michel 
    The presence of granulocytic ehrlichiae was demonstrated by PCR in Ixodes ricinus ticks and wild small mammals in Switzerland in two areas of endemicity for bovine ehrlichiosis. Six ticks (three females and three nymphs) (1.4%) of 417 I. ricinus ticks collected by flagging vegetation contained ehrlichial DNA. A total of 201 small mammals from five species, wood mouse (Apodemus sylvaticus), yellow-necked mouse (Apodemus flavicollis), earth vole (Pitymys subterraneus), bank vole (Clethrionomys glareolus), and common shrew (Sorex araneus), were trapped. The analysis of I. ricinus mammals collected on 116 small mammals showed that nine C. glareolus voles and two A. sylvaticus mice hosted infected tick larvae. In these rodents, granulocytic ehrlichia infection was also detected in blood, spleen, liver, and ear samples. Further examinations of 190 small mammals without ticks or with noninfected ticks showed the presence of ehrlichial DNA in spleen and other tissues from six additional C. glareolus, three A. flavicollis, and one S. araneus mammals. This study suggests that A. sylvaticus, A. flavicollis, S. araneus, and particularly C. glareolus are likely to be natural reservoirs for granulocytic ehrlichiae. Partial 16S rRNA gene sequences of granulocytic ehrlichiae from ticks and rodents showed a high degree of homology (99 to 100%) with granulocytic ehrlichiae isolated from humans. In contrast, groESL heat shock operon sequence analysis showed a strong divergence (approximately 5%) between the sequences in samples derived from rodents and those derived from samples from questing ticks or from other published ehrlichia sequences. Dual infections with granulocytic ehrlichia and Borrelia burgdorferi were found in ticks and small mammals.
  • Publication
    Accès libre
    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
    (2000)
    Christe, Martine
    ;
    Rutti, Bernard
    ;
    Brossard, Michel 
    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.
  • Publication
    Accès libre
    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
    (1997)
    Ganapamo, F.
    ;
    Rutti, Bernard
    ;
    Brossard, Michel 
    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.
  • Publication
    Accès libre
    Induction of host resistance to Rhipicephalus appendiculatus in rabbits: Effects of immunizing with detergent-solubilized tick tissue proteins
    (1990)
    Dhadialla, T. S.
    ;
    Rutti, Bernard
    ;
    Brossard, Michel 
    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.
  • Publication
    Accès libre
    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
    (1989)
    Rutti, Bernard
    ;
    Brossard, Michel 
    Mice were pluriinfested with nymphs and rabbits, with adult Ixodes 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 fed I. ricinus females and in tick integumental extract. It was also found in engorged nymphs but was absent from larvae. Sera of I. ricinus-infested rabbits and mice or of rabbits infested with Rhipicephalus appendiculatus adults reacted with a 20-kDa antigen in total extracts of partially fed R. appendiculatus females and the integument of this species.