1,721,219 research outputs found
Study of the African form of malignant catarrhal fever induced by alcelaphine herpesvirus 1
No full textMalignant catarrhal fever (MCF) is an usually lethal pathology which has been described in a large number of ruminant species. Based on the etiology, two main forms of MCF have been described, i.e., the European and the African forms due to ovine herpesvirus 2 (OvHV-2) and alcelaphine herpesvirus 1 (AlHV-1), respectively. The present study was devoted to the African form of MCF (AF-MCF) and to its causative agent AlHV-1. AlHV-1 belongs to the Gammaherpesvirinae subfamily of the Herpesviridae family. Wildebeests (Connochaetes spp) carry AlHV-1, which is lethal for a large number of ruminant species, while apparently harmless to its natural host. Here, we first reproduced AF-MCF using the rabbit as animal model. Macroscopic and microscopic lesions induced by AlHV-1 infection were characteristic of AF-MCF described in cattle. Next, we undertook the cloning of AlHV-1 genome as an bacterial artificial chromosome (BAC). The molecular tools required were produced. They should allow the production of a AlHV-1-BAC shortly. The rabbit animal model together with the BAC technology will allow further studies to address AF-MCF pathogenesis
Infection de l'anguille européenne par l'Anguillid herpesvirus 1: de la recherche fondamentale aux programmes de conservation
No full textThe European eel (Anguilla Anguilla) is a culturally and commercially important fish species and along with other members of the genus Anguilla, they are flagship species for aquatic conservation efforts. Anguillid eels have a fascinating and complex life cycle involving different life stages and extended migration through both marine and freshwater environments. The lifecycle of the European eel begins in the Atlantic Ocean. After hatching, leptocephali larvae drift thousands of kilometres across the ocean to reach continental coastal waters where they metamorphose into glass eels. These juvenile eels then migrate upstream towards freshwater habitats where they grow into yellow eels and remain there for several years. Finally, they fully mature into silver eels and migrate back to their place of birth, where they reproduce before dying. Within the last 50 years, the European eel population has dramatically decline and the species is now critically endangered. The reason for this steep decline in population is likely to be multifactorial, with one potential major factor being infectious diseases. In terms of viral diseases, Anguillid herpesvirus 1 (AngHV 1) is the causative agent of a haemorrhagic disease affecting freshwater eels (Anguilla spp.), and is one of the most frequently detected viruses from European eels, especially in fish farms. This herpesvirus is a member of the genus cyprinivirus of the family Alloherpesviridae.
As a consequence of this decline, the European Commission has established the “Eel Recovery Plan” within member states with the aim of protecting and restoring the population of European eel. One of the main measures of this plan relies on restocking. This process involves the active transfer of eels to inland areas where eel populations have declined. Although this restocking is widely practiced in Europe, additional studies are still needed to evaluate and improve its effectiveness.
The broad objective of the present thesis was to contribute to the conservation of the critically endangered European eel, through focusing on infectious diseases as one of the potential causative factors of its decline. Firstly, we investigated the sanitary status of wild caught glass eels entering estuaries and aimed to develop quarantine stations that would facilitate the implementation of therapeutic and prophylactic measures prior to their reintroduction into the wild. Our results showed that glass eels were negative for AngHV-1 before their reintroduction into Belgian rivers. We also established that under certain conditions, a two-week pre-release quarantine period could be implemented without major impact on important metrics such as eel survival rate, sanitary status, health and morphology.
One of the major goals of this PhD project was to gain insights into AngHV-1 pathogenesis using recombinant viral strains combined with in vivo bioluminescent imaging (IVIS). As a prerequisite for the study of AngHV 1 pathogenesis, we sequenced the entire genome of seven strains of AngHV-1 from different geographic origins and compared their biological properties in vitro, which also provided insights into the evolution of this virus. Based on this, we selected 4 strains representative of the viral species, compared their properties in vivo and produced recombinants expressing luciferase and a copepod green fluorescent protein (here after named LucGFP). Characterization of these recombinants revealed that they are appropriate for the study of AngHV-1 with no detectable negative effect associated with the insertion of the transgene. As all strains expressed comparable properties in vivo, the UK LucGFP strain was selected for the next steps of the project.
Using the UK LucGFP strain and the IVIS, we investigated major questions related to the pathogenesis of AngHV-1 infection in its natural host: These experiments led to the following observations: (i) Glass eels are not susceptible to AngHV-1 infection through the natural route tested. (ii) Inoculation of elvers led to few positive subjects expressing bioluminescence on their cephalic part, mainly gills and jaws, with no spreading of the infection between subjects according to time. (iii) Inoculation of yellow eels led to infection of all subjects expressing bioluminescence signal associated with strong clinical signs. Morbidity and cumulated mortality reached 100% and 20% respectively. (iv) The gills and the periodontal mucosa represented major portals of entry of the virus into naïve subjects. (v) Two modes of transmission of AngHV-1 were highlighted in this study, i.e. direct transmission through interspecific agonistic interactions (e.g. biting) between fish, and indirect transmission through environmental water. Our results indicate that AngHV 1 transmission via contaminated water requires a high density of subjects and virions, and is thus probably restricted to intensive aquaculture conditions. On the other hand, AngHV-1 infection mediated by biting appears highly efficient and is likely to be facilitated in environments with either high or low host density. We hypothesize that viral transmission mediated by interspecific agonistic interactions may partially explain the high prevalence of AngHV 1 in the wild despite the low infectivity of AngHV-1 in water, the low and declining host population density, the solitary behaviour of the host, and the strong ability of fish skin mucus to neutralize pathogens such as AngHV 1.
In conclusion, this project contributed to recommendations for optimization of glass eel restocking practices in Belgium and highlighted major aspects of AngHV 1 pathogenesis. The findings create ample scope for future projects in relation to eel conservation, AngHV 1 evolution, host-pathogen dynamics in aquatic environments as well as setting the groundwork for AngHV 1 vaccine development
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Contributions to the Study of the Evolutive Relationship between two Herpesviruses Infecting African Artiodactyls: Bovine Herpesvirus 4 and Alcelaphine Herpesvirus 1
No full textAlcelaphine herpesvirus 1 (AlHV 1), carried by wildebeest asymptomatically, causes malignant catarrhal fever (MCF) when cross species transmitted to a variety of susceptible species of the Artiodactyla order. There is no available vaccine against AlHV-1. Several studies suggested that the African buffalo (Syncerus caffer) rather than cattle should be considered as the natural host species of bovine herpesvirus 4 (BoHV 4), an apathogenic gammaherpesvirus that is antigenically related to AlHV 1. Rossiter and co-workers (1989) suggested that an evolutionary relationship exists between AlHV 1 and BoHV 4. This hypothesis proposes that the serological antigenic relationship existing between BoHV 4 and AlHV 1 could confer to BoHV 4 infected buffaloes a protective immune response against lethal AlHV 1 infection. In this work, our goal was to generate information and tools that are required to test this hypothesis in the future. Our results are presented as three original studies:
(i) Cloning of the alcelaphine herpesvirus 1 genome as an infectious and pathogenic bacterial artificial chromosome
Journal of General Virology (2005), in press
Dewals B., Boudry C., Gillet L, Markine-Goriaynoff N., de Leval L., Haig D.M. & Vanderplasschen A.
Alcelaphine herpesvirus 1 (AlHV 1), carried by wildebeest asymptomatically, causes malignant catarrhal fever (MCF) when cross species transmitted to a variety of susceptible species of the Artiodactyla order. The study of MCF pathogenesis has been impeded by an inability to produce recombinant viruses, due mainly to the fact that AlHV 1 becomes attenuated during passage in culture. In this study, we have overcome these difficulties by cloning the entire AlHV 1 genome as a stable, infectious and pathogenic bacterial artificial chromosome (BAC). A modified loxP flanked BAC cassette was inserted in one of the two large non-coding regions of the AlHV 1 genome. This insertion allowed the production of an AlHV 1 BAC clone stably maintained in bacteria and able to regenerate virions when transfected into permissive cells. The loxP-flanked BAC cassette was excised from the genome of reconstituted virions by growing them in permissive cells stably expressing Cre recombinase. Importantly, BAC derived AlHV 1 virions replicated comparably to the virulent (low passage) AlHV 1 parental strain and induced MCF in rabbits that was indistinguishable from that of the virulent parental strain. The availability of the AlHV 1 BAC is an important advance for the study of MCF that will allow the identification of viral genes involved in MCF pathogenesis as well as the production of attenuated recombinant candidate vaccines.
(ii) Antibodies against bovine herpesvirus 4 are highly prevalent in wild African buffaloes throughout eastern and southern Africa
Veterinary Microbiology, 2005, 110, 209-220
Dewals B., Gillet L., Gerdes T., Taracha E.L.N., Thiry E. & Vanderplasschen A.
Bovine herpesvirus 4 (BoHV 4) has been isolated from cattle throughout the world. Interestingly, a survey of wild African buffaloes mainly from the Maasai Mara Game Reserve in Kenya revealed that 94 % of the animals tested had anti BoHV 4 antibodies (Rossiter et al., Res. Vet. Sci., 1989, 46, 337 343). These authors also proposed that the serological antigenic relationship existing between BoHV 4 and alcelaphine herpesvirus 1 (AlHV 1) could confer to BoHV 4 infected buffaloes a protective immune response against lethal AlHV 1 infection. In the present study, we addressed two questions related to Rossiter et al. paper. Firstly, to investigate the role of the African buffalo as a natural host species of BoHV 4, the seroprevalence of anti BoHV 4 antibodies was analysed in wild African buffaloes throughout eastern and southern Africa. A total of 400 sera was analysed using two complementary immunofluorescent assays. These analyses revealed that independently of their geographical origin, wild African buffaloes exhibit a seroprevalence of anti BoHV 4 antibodies higher than 68 %. This result is by far above the seroprevalence generally observed in cattle. Our data are discussed in the light of our recent phylogenetic study demonstrating that the BoHV 4 Bo17 gene has been acquired from a recent ancestor of the African buffalo. Secondly, we investigated the humoral antigenic relationship existing between BoHV 4 and AlHV 1. Our results demonstrate that among the antigens expressed in AlHV 1 infected cells, epitope(s) recognized by anti BoHV 4 antibodies are exclusively nuclear, suggesting that the putative property of BoHV 4 to confer an immune protection against AlHV 1 relies on a cellular rather than on a humoral immune response.
(iii) Phylogenetic analysis of Bovine herpesvirus 4 strains isolated from cattle and from African buffalo
In preparation
Dewals B., Thirion M., Markine-Goriaynoff N., Gillet L., de Fays K., Minner F., Daix V., Sharp P.M. & Vanderplasschen A.
Bovine herpesvirus 4 (BoHV 4) is a gammaherpesvirus which has been isolated from cattle throughout the world. Virological and serological studies have demonstrated that the African buffalo is also a natural host species of BoHV-4. Interestingly, our phylogenetic study on the BoHV 4 Bo17 gene revealed that this gene has been acquired from an ancestor of the African buffalo around 1.5 million years ago. Study of the Bo17 gene also suggested a relatively ancient transmission of BoHV-4 from the ancestor of the African buffalo to the Bos primigenius lineage, followed by a host-dependent split between zebu and taurine BoHV-4 strains. In the present study, we pursued our investigations on the evolution of BoHV 4. To investigate the phylogenetic relationship existing between BoHV 4 strains isolated from African buffalo in Kenya and from cattle throughout the world, nine strains representative of the BoHV 4 species were compared based on six different regions distributed across the genome. Our phylogenetic analyses led to the following conclusions: (i) BoHV 4 strains from African buffalo and from cattle form clades which have split approximately 700,000 years ago. (ii) Since this divergence, inter clade and intra-clade recombination events occurred at different time in the past. (iii) the topology of the tree formed by zebu and taurine BoHV 4 strains is incompatible with a co-speciation process between BoHV 4 and domestic cattle implying that the latter have been contaminated through recent cross-species transmission. A scenario is proposed to explain how BoHV 4 has been transmitted from African buffalo to cattle and how the virus has reached a world wide distribution in the latter host species.
In conclusion, this work generated key information and reagents to test in a near future the hypothesis proposed by Rossiter et al. (1989). The results of this work show the complexity of the interactions existing between viruses and their hosts throughout evolution
Etude des rôles du gène ORF134 dans la biologie de l’infection de l’Herpèsvirus cyprin 3
Get PDFThe common carp is one of the most important freshwater fish species in aquaculture, and its colourful subspecies koi is grown for personal pleasure and competitive exhibitions. Both two subspecies are economically important. In the late 1990s, a highly contagious and lethal pathogen called koi herpesvirus (KHV) or cyprinid herpesvirus 3 (CyHV-3) began to cause severe financial losses in these two carp industries worldwide. In 2005, CyHV-3 has been classified in the Alloherpesviridae family of the order Herpesvirales. Because of its economic importance and its numerous original biological properties, CyHV 3 became rapidly an attractive subject for applied and fundamental research. However, to date, there is a little information on the roles of individual CyHV-3 genes in the biology of CyHV-3 infection or its pathogenesis. Moreover, there is a lack of safe and efficacious vaccine for the control of CyHV-3 disease. The goal of this thesis was to study the roles of CyHV-3 ORF134 encoding an IL-10 homologue in the biology of the infection.
CyHV-3 ORF134 has been predicted to contain an 84 bp intron flanked by 2 exons encoding together a 179 amino acid product. Transcriptomic analyses reveal that ORF134 is expressed as a spliced early-late gene. The identification of the CyHV-3 secretome was achieved using 2D-LC MS/MS proteomic approach. This method led to the identification of 5 viral and 46 cellular proteins in concentrated infected cell culture supernatant. CyHV-3 ORF12 and ORF134 were amongst the most abundant proteins detected. To investigate the roles of ORF134 in the biological of the infection, a strain deleted for ORF134 and a derived revertant strain were produced by using BAC cloning and prokaryotic recombination technologies. Comparison of these strains demonstrated that CyHV-3 ORF134 does not contribute significantly to viral growth in vitro or to virulence in vivo in the present laboratory setting. The present study addressed for the first time the in vivo role of a vIL-10 encoded by a member of the family Alloherpesviridae. This study has been published in Veterinary Research.
During the course of the first study, we obtained an unexpected recombination event while we were reconstituting infectious virus from mutated BAC plasmids. To generate a revertant ORF134 Del galK strain, CCB cells were co-transfected with the FL BAC ORF134 Del galK plasmid and the pGEMT-TK vector to remove the BAC cassette inserted in the ORF55 locus (encoding thymidine kinase). One of the clones obtained had an unexpected recombination leading to the deletion of ORF56 and ORF57 in addition to the expected deletion of ORF134. Unexpectedly, this triple deleted strain replicated efficiently in vitro, exhibited an attenuated phenotype in vivo and was proved to confer in a dose dependent manner an immune protection against a lethal challenge. The goal of the second experimental chapter was to investigate the role of the ORF56-57 and ORF134 deletions in the observed safety/efficacy profile of the triple deleted recombinant. To reach this goal, a collection of recombinant strains were produced using BAC cloning technologies, characterized and tested in vivo for their safety/efficacy profile. The results obtained demonstrated that the ORF56-57 deletion is responsible for the phenotype observed and that ORF134 deletion does not contribute to this phenotype significantly. Finally, the immune protection conferred by ORF56-57 deleted recombinant was investigated by challenging immunized fish with a wild type strain expressing luciferase as a reporter gene. In vivo imaging system (IVIS) analyses of immunized and challenged fish demonstrated that the immune response induced by the ORF56-57 deleted strain was able to prevent subclinical infection of the challenge strain.
In conclusion, the present thesis addressed both fundamental and applied aspects of CyHV-3. For the first time, it investigated in vivo the roles of a viral IL-10 homologue encoded by a member of the family Alloherpesviridae. Importantly, it identified the ORF56-57 loci as target for production of safe and efficacious attenuated recombinant vaccines
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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