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Gern, Lise

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

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  • Publication
    Accès libre
    Ecologie de 'Borrelia burgdorferi' sensu lato en Suisse: dynamique saisonnière de la tique 'Ixodes ricinus', sa relation avec les rongeurs, et implication des modes de transmission de 'B. afzelii' entre rongeurs et tiques sur la diversité du gène ospC chez 'B.afzelii'
    (2012)
    Pérez Bertoni, David
    ;
    Gern, Lise 
    En Europe, les agents de la Borréliose de Lyme (BL) sont maintenus dans la nature via un cycle de transmission impliquant la tique Ixodes ricinus (I. ricinus) et des hôtes réservoirs. Le gène codant pour l’ « Outer Surface Protein C » (OspC), une lipoprotéine plasmidique exprimée par les spirochètes lors du repas sanguin de la tique et lors de la dissémination chez l’hôte, est un marqueur génétique pouvant être associé à la pathogénèse et à la sévérité d’une BL. L’analyse du gène ospC a permis de classifier des isolats de Borrelia. burgdorferi sensu lato (B. burgdorferi sl) en groupes ospC.
    De 2003 à 2005, nous avons prélevé de façon mensuelle des tiques libres dans 2 sites du plateau suisse, les Portes-Rouges (PR) et le Staatswald (SW). Parallèlement, les micromammifères ont été piégés afin de rechercher la présence de stades immatures d’I. ricinus et l’infection des rongeurs a été vérifiée par xénodiagnose. La typisation des génoespèces de B. burgdorferi sl chez les tiques libres, les tiques des rongeurs et les tiques de xénodiagnose a été réalisée par « Polymerase Chain Reaction » (PCR) et « Restriction Fragment Length Polymorphism » (RFLP). Les isolats de B. afzelii, génoespèce associée aux rongeurs, obtenus de ces 3 populations de tiques, ont été analysés par « Single Stranded Conformational Polymorphism » (SSCP) et classifiés par groupes ospC.
    Nous avons observé durant les 3 années des variations dans l’évolution saisonnière de la densité de tiques libres. La densité de nymphes en quête était plus importante au PR alors que la proportion de rongeurs infestés par des stades immatures d’I. ricinus était similaire dans les 2 sites. Des tiques ont été observées sur les rongeurs en automne et en été alors que la densité de tiques libres était faible voire inexistante. Les rongeurs du SW présentaient des infestations par des immatures d’I. ricinus élevées et 28% étaient infestés par des nymphes et des larves (11% au PR). Cette nutrition simultanée de tiques regroupées sur un hôte porte le nom de co-feeding et permet la transmission de pathogènes entre tiques infectées et tiques non-infectées, sans présence d’infection systémique chez l’hôte. Malgré une situation favorable de co-feeding, principalement au SW, seul B. afzelii et B. bavariensis ont été transmises des rongeurs aux tiques laissant supposer que le co-feeding ne contribue pas au maintien de la diversité des génoespèces de B. burgdorferi sl présentes chez les tiques libres.
    L’analyse du gène ospC nous a permis de classer les isolats de B. afzelii provenant des différentes populations de tiques en 10 groupes ospC, dont 8 déjà décrits (A1, A2, A3, A4, A5, A6, A8, VS461) et 2 nouveaux (ME et YU). La plus grande diversité de groupes ospC a été observée chez les tiques en quête. Les isolats de B. afzelii obtenus à partir de larves d’I. ricinus s’étant nourries en co-feeding avec des nymphes présentaient une diversité de groupes ospC plus importante que celles s’étant nourries seules. Ce travail montre pour la première fois l’importance du co-feeding dans le maintien de la diversité intraspécifique de B. afzelii dans la nature.
  • Publication
    Métadonnées seulement
    A comparison of two DNA extraction approaches in the detection of Borrelia burgdorferi sensu lato from live Ixodes ricinus ticks by PCR and reverse line blotting
    (2007)
    Cadenas, Francisca Moran
    ;
    Schneider, Helene
    ;
    Lommano, Elena 
    ;
    Burri, Caroline
    ;
    Moret, Jacqueline
    ;
    Gern, Lise 
    We tested two approaches to extract Borrelia DNA from live Ixodes ricinus ticks before polymerase chain reaction (PCR) and reverse line blotting (RLB): DNA extraction of one half of the tick after incubation in BSK medium and DNA extraction of the other half of the tick directly, using ammonium hydroxide. Among 2079 ticks, 31.2% (n = 649) were found to be Borrelia-infected by PCR-RLB test using at least one of the DNA extraction methods. Five hundred four ticks (24.2%) were found infected after incubation in BSK and 481 (23.1%) after direct DNA extraction from the tick. The difference was not significant. However, these prevalences were significantly lower when only one method was applied (23.1% and 24.2%) compared to the prevalence obtained by the use of both methods (31.2%). In 313 infected ticks discordant results were obtained, i.e., one half of the tick was found to be infected whereas the other half was uninfected. Among these ticks, B. garinii and B. burgdorferi sensu stricto (ss) were significantly more frequently identified in the half tick incubated in BSK. No significant differences were observed for B. burgdorferi ss, B. valaisiana, and for undetermined Borrelia species.
  • Publication
    Métadonnées seulement
    Borrelia burgdorferi persists in the brain in chronic lyme neuroborreliosis and may be associated with Alzheimer disease
    (2004)
    Miklossy, Judith
    ;
    Khalili, Kamel
    ;
    Gern, Lise 
    ;
    Ericson, Rebecca L
    ;
    Darekar, Pushpa
    ;
    Bolle, Lorie
    ;
    Hurlimann, Jean
    ;
    Paster, Bruce J
    The cause, or causes, of the vast majority of Alzheimer's disease cases are unknown. A number of contributing factors have been postulated, including infection. It has long been known that the spirochete Teponema pallidum, which is the infective agent for syphilis, can in its late stages cause dementia, chronic inflammation, cortical atrophy and amyloid deposition. Spirochetes of unidentified types and strains have previously been observed in the blood, CSF and brain of 14 AD patients tested and absent in 13 controls. In three of these AD cases spirochetes were grown in a medium selective for Borrelia burgdorferi. In the present study, the phylogenetic analysis of these spirochetes was made. Positive identification of the agent as Borrelia burgdorferi sensu stricto was based on genetic and molecular analyses. Borrelia antigens and genes were co-localized with beta-amyloid deposits in these AD cases. The data indicate that Borrelia burgdorferi may persist in the brain and be associated with amyloid plaques in AD. They suggest that these spirochetes, perhaps in an analogous fashion to Treponema pallidum, may contribute to dementia, cortical atrophy and amyloid deposition. Further in vitro and in vivo studies may bring more insight into the potential role of spirochetes in AD.
  • Publication
    Métadonnées seulement
    Artificial-infection protocols allow immunodetection of novel Borrelia burgdorferi antigens suitable as vaccine candidates against Lyme disease
    (2003)
    Wallich, Reinhard
    ;
    Jahraus, Oliver
    ;
    Stehle, Thomas
    ;
    Tran, Thi Thanh Thao
    ;
    Brenner, Christiane
    ;
    Hofmann, Heidelore
    ;
    Gern, Lise 
    ;
    Simon, Markus M
    Vaccination with recombinant outer surface protein A (OspA) from Borrelia burgdorferi provides excellent antibody-mediated protection against challenge with the pathogen in animal models and in humans. However, the bactericidal antibodies are ineffective in the reservoir host, since OspA is expressed by spirochetes only in the vector, but rarely, if at all, in mammals. Using an artificially generated immune serum (anti-10(8) spirochetes) with high protective potential for prophylactic and therapeutic treatment, we have now isolated from an expression library of B. burgdorferi (strain ZS7) three novel genes, zs7.a36, zs7.a66 and zs7.a68. All three genes are located, together with ospA/B, on the linear plasmid lp54, and are expressed in vitro and in ticks. At least temporarily two of them, ZS7.A36 and ZS7.A66, are also expressed during infection. The respective natural antigens are poorly immunogenic in infected normal mice but elicited antibodies in Lyme disease patients. We show that recombinant preparations of ZS7.A36, ZS7.A66 and ZS7.A68 induce functional antibodies in rabbits capable of protecting immunodeficient mice against subsequent experimental infection. These findings suggest that all three recombinant antigens represent potential candidates for a 'second generation' vaccine to prevent and/or cure Lyme disease.
  • Publication
    Accès libre
    Early detection of Borrelia burgdorferi sensu lato infection in Balb/c mice by co-feeding Ixodes ricinus ticks
    (2003)
    Hu, Chang Min
    ;
    Cheminade, Yves
    ;
    Perret, Jean-Luc
    ;
    Weynants, Vincent
    ;
    Lobet, Yves
    ;
    Gern, Lise 
    In Europe, Borrelia burgdorferi is transmitted by Ixodes ricinus to animals and human. When infected and uninfected ticks co-feed on a host, spirochetes are transmitted from ticks to animal and also to uninfected ticks. Here, we used uninfected ticks to co-feed with infected ticks on mice to evaluate this method to detect early infection in mice. A total of 128 mice were challenged by infected nymphs placed in capsules glued on the back of the mice. Three days later uninfected larvae were added in the capsule to co-feed with infected nymphs and were examined for Borrelia infection after natural detachment. Infection in mice was also determined by xenodiagnosis and by spirochete isolation from ear skin biopsy and back skin biopsy taken at the tick attachment site one month after infection. A total of 111 mice were found to be infected by at least one of these four methods. Borrelia infection was observed in 95% of mice by the co-feeding method, in 92% of mice by xenodiagnosis, in 69% and in 68% of mice by cultivation of ear and back skin biopsies, respectively. Our results demonstrate that the co-feeding method is a very sensitive method which can be used to detect very early infection in mice infected by tick bites.
  • Publication
    Métadonnées seulement
    Lyme disease
    (2000)
    Gern, Lise 
    ;
    Falco, Richard C
    Lyme borreliosis, the most common vector-borne disease in the northern hemisphere, is caused by bacteria belonging to the Borrelia burgdorferi complex. The disease is multisystemic, affecting main ly the skin, nervous system, heart and joints. in Europe, the vector of the disease is the tick Ixodes ricinus, whereas in the United States of America, two primary tick vectors exist, namely: I. scapularis in the north-eastern and mid-western regions and I. pacificus on the west coast. Several species of small and medium-sized mammals and ground-feeding birds serve as reservoirs for the bacteria in endemic areas. The prognosis for patients with Lyme borreliosis is excellent, particularly when diagnosed and treated early in the course of infection. Prevention of Lyme borreliosis can be achieved using two approaches, either prevention of infection by immunisation, or prevention of tick bites through avoidance, personal protection and tick control.
  • Publication
    Métadonnées seulement
    Infection of Ixodes ricinus (Acari : Ixodidae) by Borrelia burgdorferi sensu lato in North Africa
    (1999)
    Zhioua, Elyes
    ;
    Bouattour, Ali
    ;
    Hu, Chang Min
    ;
    Gharbi, Mohamed
    ;
    Aeschliman, Andre
    ;
    Ginsberg, Howard S
    ;
    Gern, Lise 
    Free-living adult Ixodes ricinus. were collected in Amdoun, situated in the Kroumiry mountains in northwestern Tunisia (North Africa). Using direct fluorescence antibody assay, the infection rate of field-collected I. ricinus bq Borrelia burgdorferi sensu late was 30.5% (n = 72). No difference in infection rate was observed between male and female ticks. Spirochetes that had been isolated from I. ricinus from Ain Drahim (Kroumiry Mountains) in 1988 were identified as Borrelia lusitaniae (formerly genospecies PotiB2). This is the first identification of a genospecies of Borrelia burgdorferi sensu lato from the continent of Africa.
  • Publication
    Métadonnées seulement
    Longitudinal study of Lyme borreliosis in a high risk population in Switzerland
    (1998)
    Zhioua, Elyes
    ;
    Gern, Lise 
    ;
    Aeschlimann, André 
    ;
    Sauvain, Marie-Josephe
    ;
    Van der Linden, Sjef
    ;
    Fahrer, Heinz
    Orienteers from all parts of Switzerland (n = 416) were included in a longitudinal study for lyme borreliosis. In spring 1986, the seroprevalence was 28.1 %. At the beginning of the study, 84.3 % of orienteers reported a history of tick bite, and 3.8 % reported a past history of lyme borreliosis. During the first (spring 1986-autumn 1986), second (autumn 1986-spring 1987) and third (spring 1987-autumn 1987) period, rates of seroconversion were 0.6 % 2.7 % and 2.1 % respectively. During the first and second period, clinical incidence were 1.0 % and 0.25 % respectively. No active lyme borreliosis was detected during the third period. Among orienteers who seroconverted during the study (n = 16), only two developed clinical symptoms. Hence, Borrelia burgdorferi infection is often asymptomatic.
  • Publication
    Accès libre
    Lyme disease
    Gern, Lise 
    ;
    Falco, R.C
    La borréliose de Lyme qui est, dans l'hémisphère nord, la plus répandue des maladies à transmission vectorielle, est due à des bactéries appartenant au genre Borrelia burgdorferi. Il s'agit d'une maladie plurisystémique qui affecte essentiellement la peau, le système nerveux le cœur et les articulations. En Europe, le vecteur de la maladie est la tique Ixodes ricinus; aux États -Unis d'Amérique les deux vecteurs principaux sont la tique I. scapularis dans les régions du nord-est et du centre-ouest et I. pacificus sur la Côte Ouest. Plusieurs espèces de petits et moyens mammifères ou d'oiseaux terrestres servent de réservoirs à la bactérie dans les zones endémiques. Le pronostic est excellent, surtout lorsque la maladie de Lyme est diagnostiquée en phase initiale et traitée immédiatement. La prophylaxie repose sur deux méthodes: l'immunisation préventive, d'une part, et la mise en œuvre de mesures permettant d'éviter les piqûres de tiques et de lutter contre ces vecteurs, d'autre part., Lyme borreliosis, the most common vector-bome disease in the northern hemisphere, is caused by bacteria belonging to the Borrelia burgdorferi complex. The disease is multisystemic, affecting mainly the skin, nervous system, heart and joints. In Europe, the vector of the disease is the tick Ixodes ricinus, whereas in the United States of America, two primary tick vectors exist, namely: I. scapularis in the north-eastern and mid-western regions and I. pacificus on the west coast. Several species of small and medium-sized mammals and ground-feeding birds serve as reservoirs for the bacteria in endemic areas. The prognosis for patients with Lyme borreliosis is excellent, particularly when diagnosed and treated early in the course of infection. Prevention of Lyme borreliosis can be achieved using two approaches, either prevention of infection by immunisation, or prevention of tick bites through avoidance, personal protection and tick control., De todas las enfermedades vehiculadas por vectores, la borreliosis de Lyme, causada por bacterias pertenecientes al complejo Borrelia burgdorferi, es la más común en el hemisferio norte. Esta enfermedad de carácter multisistémico afecta principalmente la piel, el sistema nervioso, el corazón y las articulaciones. En Europa, el vector de la enfermedad es la garrapata Ixodes ricinus. En los Estados Unidos de América, por su parte, existen dos garrapatas que ejercen de vectores primarios: I.scapularis en las regiones del noreste y el medio oeste, e I.pacificus en la costa oeste. En las áreas endémicas varias especies de mamíferos pequeños y medianos y de aves de alimentación terrestre sirven de reservorio de las bacterias. Los pacientes afectados de borreliosis de Lyme presentan un pronóstico excelente, sobre todo cuando se diagnostica y trata la infección en sus fases iniciales. Para prevenir esta enfermedad caben dos procedimientos distintos: prevenir la infección con medidas de inmunización; o impedir la mordedura de la garrapata previniendo esta posibilidad, protegiéndose del contacto y luchando contra sus poblaciones.