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Gern, Lise

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Gern, Lise
Affiliation principale
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Ancien.ne collaborateur.trice
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https://libra.unine.ch/handle/123456789/303

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  • Publication
    Métadonnées seulement
    Ixodes ticks belonging to the Ixodes ricinus complex encode a family of anticomplement proteins
    (2007)
    Daix, Virginie
    ;
    Schroeder, Hélène
    ;
    Praet, N
    ;
    Georgin, Jean-Pierre
    ;
    Chiappino, I
    ;
    Gillet, Laurent
    ;
    de Fays, Katalin
    ;
    Decrem, Yves
    ;
    Leboulle, Gérard
    ;
    Godfroid, Edmond
    ;
    Bollen, Alex
    ;
    Pastoret, Paul-Pierre
    ;
    Gern, Lise 
    ;
    Sharp, Paul
    ;
    Vanderplasschen, Alain
    The alternative pathway of complement is an important innate defence against pathogens including ticks. This component of the immune system has selected for pathogens that have evolved countermeasures. Recently, a salivary protein able to inhibit the alternative pathway was cloned from the American tick Ixodes scapularis (Valenzuela et al., 2000; J. Biol. Chem. 275, 18717-18723). Here, we isolated two different sequences, similar to Isac, from the transcriptome of I. ricinus salivary glands. Expression of these sequences revealed that they both encode secreted proteins able to inhibit the complement alternative pathway. These proteins, called I. ricinus anticomplement (IRAC) protein I and II, are coexpressed constitutively in I. ricinus salivary glands and are upregulated during blood feeding. Also, we demonstrated that they are the products of different genes and not of alleles of the same locus. Finally, phylogenetic analyses demonstrate that ticks belonging to the Ixodes ricinus complex encode a family of relatively small anticomplement molecules undergoing diversification by positive Darwinian selection.
  • Publication
    Métadonnées seulement
    Presence of potentially pathogenic Babesia sp for human in Ixodes ricinus in Switzerland
    (2006)
    Casati, Simona
    ;
    Sager, Heinz
    ;
    Gern, Lise 
    ;
    Piffaretti, Jean-Claude
    We have designed and performed a new PCR method based on the 18S rRNA in order to individuate the presence and the identity of Babesia parasites. Out of H 59 Ixodes ricinus (Acari: Ixodidae) ticks collected in four areas of Switzerland, nine were found to contain Babesia DNA. Sequencing of the short amplicon obtained (411 452 bp) allowed the identification of three human pathogenic species: Babesia microti, B. divergens, for the first time in Switzerland, Babesia sp. EU1. We also report coinfections with B. sp. EU1-Borrelia burgdoferi sensu stricto and Babesia sp. EU1-B. afzelii.
  • Publication
    Métadonnées seulement
    Diversity of the population of Tick-borne encephalitis virus infecting Ixodes ricinus ticks in an endemic area of central Switzerland (Canton Bern)
    (2006)
    Casati, Simona
    ;
    Gern, Lise 
    ;
    Piffaretti, Jean-Claude
    Tick-borne encephalitis virus (TBEV), a member of the genus Flavivirus, has a positive-strand RNA genome containing a single open reading frame flanked by non-coding regions (NCRs). Ixodes ricinus ticks (n = 307) were collected from vegetation in a natural TBEV focus in Belp, Switzerland. The presence and identity of the virus were determined by nested RT-PCR followed by sequencing of the 5'-terminal region that comprises the 5' NCR and the capsid-encoding region (C). The presence of the western European TBEV subtype (W-TBEV) genome was detected in 14.3% of the ticks. Nucleotide sequence analysis revealed a high variability of 55.5%. In particular, four DNA fragments (CS 'A', CS 'B', the folding-stem structure and the start codon) showed substantial heterogeneity, which has the potential of compromising replication, translation and packaging of the viral genome. This variability may reflect a viral strategy to select the fittest RNA molecule to produce a viral infection in the different vertebrate hosts that may be encountered by the ticks. It may also indicate a possible ancient introduction of TBEV to the Belp site. In addition, it may contribute to explaining the annual low incidence of tick-borne encephalitis in the natural focus of Belp, despite the high prevalence of TBEV genomes in ticks.