Chimeric hepatitis B virus/hepatitis C virus envelope proteins elicit broadly neutralizing antibodies and constitute a potential bivalent prophylactic vaccine.

International audienceThe development of a prophylactic vaccine against hepatitis C virus (HCV) has become an important medical priority, because 3-4 million new HCV infections are thought to occur each year worldwide. Hepatitis B virus (HBV) is another major human pathogen, but infections with this virus can be prevented with a safe, efficient vaccine, based on the remarkable ability of the envelope protein (S) of this virus to self-assemble into highly immunogenic subviral particles. Chimeric HBV-HCV envelope proteins in which the N-terminal transmembrane domain of S was replaced with the transmembrane domain of the HCV envelope proteins (E1 or E2) were efficiently coassembled with the wild-type HBV S protein into subviral particles. These chimeric particles presented the full-length E1 and E2 proteins from a genotype 1a virus in an appropriate conformation for formation of the E1-E2 heterodimer. Produced in stably transduced Chinese hamster ovary cells and used to immunize New Zealand rabbits, these particles induced a strong specific antibody (Ab) response against the HCV and HBV envelope proteins in immunized animals. Sera containing anti-E1 or anti-E2 Abs elicited by these particles neutralized infections with HCV pseudoparticles and cell-cultured viruses derived from different heterologous 1a, 1b, 2a, and 3 strains. Moreover, the anti-hepatitis B surface response induced by these chimeric particles was equivalent to the response induced by a commercial HBV vaccine. Conclusions: Our results provide support for approaches based on the development of bivalent HBV-HCV prophylactic vaccine candidates potentially able to prevent initial infection with either of these two hepatotropic viruses. (HEPATOLOGY 2013)

Vaccination against toxoplasmosis in farm animals

Toxoplasmosis is a worldwide zoonotic disease caused by the protozoa Toxoplasma gondii. It is transmitted to man by the ingestion of contaminated and undercooked meat. In sheep and goats, toxoplasmosis causes numerous abortions. A thorough analysis of the seroprevalence of toxoplasmosis in different animal species will help consumer information and thus limit the risks of transmission. The vaccination of farm animals may help reduce the transmission to man, as well as prevent abortion in ewes. A naturally attenuated live T. gondii vaccine is available for the prevention of abortions in ewes, but its virulence is not fully controlled, and there is a risk of reversion to a pathogenic strain. Molecular biology techniques have lead to the development of attenuated strains through the deletion of targeted genes, which are unlikely to revert to their initial virulence. A strain called Mic1-3KO was shown to be effective against congenital and chronic toxoplasmosis in mice. It is also effective against congenital toxoplasmosis in ewes. This vaccine approach remains promising.La toxoplasmose est une zoonose mondialement répandue. Chez l'homme, elle apparaît après l'ingestion de viandes insuffisamment cuites d'animaux contaminés. Chez le mouton et la chèvre, elle est à l'origine de nombreux avortements. Une étude approfondie de sa séroprévalence chez les différentes espèces animales peut permettre de mieux informer les consommateurs et ainsi de limiter les risques de transmission. La vaccination des animaux semble être une alternative intéressante puisqu'elle pourrait diminuer la transmission à l'homme mais également prévenir les avortements chez les brebis. L'utilisation d'une souche naturelle de Toxoplasma gondii incomplète, présentant une virulence atténuée, a montré son efficacité dans la protection contre l'avortement des brebis. Cependant, sa virulence n'est pas bien contrôlée, et le risque de réversion vers la forme virulente existe. Les techniques de biologie moléculaire ont permis d'obtenir des souches atténuées par la délétion de gènes ciblés, qui ne sont pas susceptibles de retrouver leur virulence d'origine. L'une d'elles, appelée Mic1-3KO, a montré son efficacité dans un modèle murin contre la toxoplasmose chronique et congénitale. Elle est également efficace contre la toxoplasmose congénitale chez la brebis. Cette démarche vaccinale reste prometteuse. De plus, l'utilisation du toxoplasme comme vecteur vaccinal reste une perspective intéressante, puisque ce parasite est capable d'exprimer des protéines étrangères

Mic1-3 Knockout Toxoplasma gondii is a good candidate for a vaccine against T. gondii-induced abortion in sheep

This study assessed the effectiveness of a mutant strain of Toxoplasma gondii (RH strain) lacking the mic1 and mic3 genes (Mic1-3KO) against Toxoplasma abortion in sheep. Ewes were inoculated subcutaneously with 105 Mic1-3KO tachyzoïtes in three independent experiments. Following vaccination, Mic1-3KO induced a mild febrile response and serum IgG antibodies, which persisted throughout the experiments. Tissue cysts formed in the sheep, but were not, under our experimental conditions, infectious when given orally. Ewes were mated two months after vaccination and were orally challenged with the PRU strain of T. gondii at mid-gestation (400 oocysts in Experiments 1 and 2; 100 oocysts in Experiment 3). Challenge of vaccinated pregnant ewes resulted in a slight febrile response, whereas unvaccinated ewes developed a more severe, characteristic febrile response of longer duration. After challenge, all unvaccinated ewes aborted whereas 62%, 91% and 64% (Experiments 1, 2 and 3 respectively) of the lambs from vaccinated ewes were viable, with no clinical signs of infection. Mic1-3KO was as effective as S48, the strain used as a live vaccine for sheep (Toxovax®). A dose of 105 Mic1-3KO tachyzoites was sufficient to induce protection (versus a dose of 2 × 106). Both subcutaneous and intraperitoneal injections were effective. Moreover, preliminary results showed the potential of Mic1-3KO to reduce the development of tissue cysts in lambs born to vaccinated ewes. This study demonstrates that Mic1-3KO is a potent vaccine candidate

Babesia divergens glycosylphosphatidylinositols modulate blood coagulation and induce Th2-biased cytokine profiles in antigen presenting cells

This work was supported by the the University of Tours (to IDP and FDG), the University of Montpellier (to SD and EC), the Deutsche Forschungsgemeinschaft (to RTS), the Wellcome Trust project grant 093228 (to TKS) and the Campus France/DAAD PHC PROCOPE 24931RE (to RTS and EC). The funding source has no involvement in the conduct of the research and preparation of the article.Glycosylphosphatidylinositols (GPIs) are glycolipids described as toxins of protozoan parasites due to their inflammatory properties in mammalian hosts characterized by the production of interleukin (IL)-1, IL-12 and tumor necrosis factor (TNF)-α. In the present work, we studied the cytokines produced by antigen presenting cells in response to ten different GPI species extracted from Babesia divergens, responsible for babesiosis. Interestingly, B. divergens GPIs induced the production of anti-inflammatory cytokines (IL-2, IL-5) and of the regulatory cytokine IL-10 by macrophages and dendritic cells. In contrast to all protozoan GPIs studied until now, GPIs from B. divergens did not stimulate the production of TNF-α and IL-12, leading to a unique Th1/Th2 profile. Analysis of the carbohydrate composition of the B. divergens GPIs indicated that the di-mannose structure was different from the evolutionary conserved tri-mannose structure, which might explain the particular cytokine profile they induce. Expression of major histocompatibility complex (MHC) molecules on dendritic cells and apoptosis of mouse peritoneal cells were also analysed. B. divergens GPIs did not change expression of MHC class I, but decreased expression of MHC class II at the cell surface, while GPIs slightly increased the percentages of apoptotic cells. During pathogenesis of babesiosis, the inflammation-coagulation auto-amplification loop can lead to thrombosis and the effect of GPIs on coagulation parameters was investigated. Incubation of B. divergens GPIs with rat plasma ex vivo led to increase of fibrinogen levels and to prolonged activated partial thromboplastin time, suggesting a direct modulation of the extrinsic coagulation pathway by GPIs.Publisher PDFPeer reviewe

Blockade of IL-33R/ST2 Signaling Attenuates Toxoplasma gondii Ileitis Depending on IL-22 Expression

Oral T. gondii infection (30 cysts of 76K strain) induces acute lethal ileitis in sensitive C57BL/6 (B6) mice with increased expression of IL-33 and its receptor ST2 in the ileum. Here we show that IL-33 is involved in ileitis, since absence of IL-33R/ST2 attenuated neutrophilic inflammation and Th1 cytokines upon T. gondii infection with enhanced survival. Blockade of ST2 by neutralizing ST2 antibody in B6 mice conferred partial protection, while rmIL-33 aggravated ileitis. Since IL-22 expression further increased in absence of ST2, we blocked IL-22 by neutralizing antibody, which abrogated protection from acute ileitis in ST2 deficient mice. In conclusion, severe lethal ileitis induced by oral T. gondii infection is attenuated by blockade of ST2 signaling and may be mediated in part by endogenous IL-22

Développement d’un vaccin sous-unitaire innovant contre la toxoplasmose des animaux de la faune sauvage en captivité

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New vaccination approaches to control toxoplasmosis

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