Ruminant alphaherpesviruses related to bovine herpesvirus 1 (BoHV-1) are a cluster of viruses antigenically and genetically closely related. The prototype of this cluster, BoHV-1, is a major pathogen of cattle associated with various clinical manifestations including infectious bovine rhinotracheitis (IBR) and infectious pustular vulvovaginitis (IPV). IBR is a disease of major economic concern in many parts of the world and especially in Europe, both in countries where this infection has been eradicated and in those where the control of IBR is currently or will be undertaken. The massive use of vaccination allowed a significant reduction of the number of IBR clinical cases. However, the existence of closely related viruses to BoHV-1 is a threat for IBR eradication programmes. Consequently, the main objective of the present work is dedicated to afford a better knowledge of the interaction between alphaherpesviruses and their ruminant hosts in order to contribute to improve the control of IBR. To meet the objective, two approaches have been developed: the study of the viral diversity aiming to extend both epidemiological and virological data about ruminant alphaherpesviruses related to BoHV-1 and the study of the heterologous protection aiming to protect minor ruminant species by the concept of the cascade vaccination. Illustrating the problematic of the cluster of ruminant alphaherpesviruses related to BoHV-1, an original situation has been described recently in Belgium. During 2001 and 2002 hunting seasons, 28.9% of red deer were detected seropositive to BoHV-1. Due to an apparent lack of contact between cattle and red deer, it was suggested that a BoHV-1 related virus was spreading in the Belgian red deer population. Thus, the first isolation of cervid herpesvirus 1 (CvHV-1) in wild fauna is reported, which brings the opportunity to deeper analyse the antigenic, genomic and genetic relationship between BoHV-1 and its related ruminant alphaherpesviruses. This isolation demonstrates that a ruminant can be strongly identified as BoHV-1 positive while in actual fact it is infected with a related but distinct alphaherpesvirus and this ruminant will be declared as false positive. The problem is even greater when these viruses become latent allowing their possible reactivation and persistence for a very long time in their ecological niches. It is necessary to have tests which can differentiate related alphaherpesviruses that infect different ruminant species. The control of IBR relies on the use of BoHV-1 gB and gE blocking enzyme linked immunosorbent assays (ELISA) in order to differentiate infected and gE-negative vaccinated animals. Knowing that CpHV-1 is the most distant virus from BoHV-1, it can be hypothesised that a BoHV-1 gB blocking ELISA detects CpHV-1 but that CpHV-1 infection could be discriminated by a BoHV-1 gE blocking ELISA. CpHV-1 being mainly distributed in the Mediterranean part of Europe as Greece, Spain and Italy, the analysis was performed with field serums collected in France with the aim to update the epidemiological situation of the infection in Europe. Besides BoHV-1, CpHV-1 is the most relevant infection in Europe but is sadly neglected. The first reason is that economic losses are restricted to a herd level in contrast with IBR that brings an economical impact at a country level. The second reason is that goat is considered as a minor species. In this context, the problem is still not big enough for commercial interest towards vaccine development. The European Union has recently pointed out the problem of minor uses and minor species and allowed off label use of veterinary medicinal products or the use of a product licensed for a major species when an authorised veterinary medicinal product is not available (cascade principle). Goat being a minor species and CpHV-1 sharing close antigenic and genetic properties with BoHV-1, a live attenuated gE-negative BoHV-1 vaccine has been assessed in goats to protect against either a nasal or a genital CpHV-1 infection.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / Vaccines with antigenic markers also known as differential vaccines have been largely used for control and prevention of bovine herpesvirus 1 (BoHV-1) infection. With this purpose, a Brazilian BoHV-1 isolate (SV56/90) was submitted to deletion of the glycoprotein E (gE) gene for a potential use in vaccines. BoHV-1 gE gene deletion was performed by homologous recombination, being the gE gene replaced by the green fluorescent protein (GFP) gene for selection. Upon co-transfection of MDBK cells with genomic viral DNA plus the GFP-bearing gE-deletion plasmid, three fluorescent recombinant clones were obtained (and nominated as BoHV-1ΔgE). The recombinant viruses formed smaller plaques in MDBK cells yet with similar kinetics and grew to similar titers to those of the parental virus, showing that gE deletion had no deleterious effect on the replication efficiency in vitro. Thirteen calves inoculated intramuscularly (IM) with the recombinant BoHV-1ΔgE developed virus neutralizing (VN) antibodies at day 42pi (titers from 2 to 16), demonstrating his ability to replicate and to induce a serological response in vivo. Furthermore, the serological response induced by the recombinant virus could be differentiated from that induced by wild-type BoHV-1 by the use of an anti-gE antibody ELISA kit. Experiments to determine the safety, immunogenicity and protection were performed with the BoHV-1ΔgE candidate vaccine strain. In the safety test, five three months-old calves were inoculated with approximately 10-100 times the usual vaccine dose (108.5TCID50 per animal). The inoculated animals remained healthy and did not shed virus, confirmed by the absence of virus in nasal secretions and lack of seroconversion by sentinel calves kept in contact. In addition, the recombinant virus was not shed upon dexamethasone administration (at day 42pi) showing the inability of reactivation and/or shedding after attempts of reactivation of latent infection. In the immunogenicity test, calves (8 to 10 months-old) were vaccinated once IM (group I, n=8) or subcutaneously (group II, n=9) with live BoHV-1ΔgE or twice (30 days apart) with inactivated virus plus aluminum hydroxide (group IV, n=13) or MontanideTM Gel 1 (Seppic - group V, n=14). As controls, three animals (group III) were vaccinated once IM with the parental virus. All calves vaccinated with live virus developed VN titers of 2 to 8 (group I, GMT: 2; group II, GMT: 1.65; group III, GMT: 1.65) at day 42pv. Animals of groups IV and V developed VN titers of 2 to 16 (GMT: 2.45) and 2 to 128 (GMT: 3.9), respectively. All calves vaccinated with the BoHV-1ΔgE remained negative in the gE ELISA. In a vaccination-challenge experiment, six calves (three to four-months-old) were vaccinated with live virus (107.3TCID50/animal) and four calves were kept as controls. Forty-seven days after vaccination, the calves were challenged with a heterologous BoHV-1 strain (107.5TCID50/animal) by the intranasal route. Vaccinated animals developed only mild and transient nasal signs comparing with the control calves. Virus shedding by vaccinated animals was also significantly reduced compared to controls. These results demonstrate that the recombinant BoHV-1ΔgE is safe/attenuated, immunogenic for calves both in a live or inactivated, adjuvanted vaccine formulation. Moreover, it induces a humoral response that can be distinguished from that induced by the wild type virus. Thus, the recombinant BoHV-1ΔgE presents suitable properties to be used in vaccine formulations. / Vacinas com marcadores antigênicos também denominadas vacinas diferenciais tem sido amplamente utilizadas no controle e prevenção da infecção pelo herpesvírus bovino tipo 1 (BoHV-1). Com este objetivo, uma amostra brasileira de BoHV-1 (SV56/90) foi submetida à deleção do gene da glicoproteína E (gE) para potencial uso em vacinas. A deleção do gene da gE foi realizada por recombinação homóloga, sendo o gene da gE substituído por um marcador para seleção (green fluorescent protein, GFP). Após co-transfecção de plasmídio de deleção e DNA genômico viral em células MDBK, três recombinantes expressando a GFP foram obtidos (e denominados BoHV-1ΔgE). Os vírus recombinantes produziram placas menores em células MDBK, porém com cinética e em títulos semelhantes ao vírus parental, demonstrando que a deleção da gE não afetou negativamente a sua capacidade replicativa in vitro. Treze bezerros inoculados pela via intramuscular (IM) com o recombinante BoHV-1ΔgE desenvolveram anticorpos neutralizantes (títulos entre 2 e 16), demonstrando a sua capacidade replicativa e imunogênica in vivo. Além disso, a resposta sorológica induzida pelo recombinante pode ser diferenciada daquela induzida pelo vírus parental pelo uso de um teste ELISA específico para anticorpos anti-gE. Posteriormente, o vírus recombinante foi submetido a testes de segurança/atenuação, de imunogenicidade e de proteção frente a desafio in vivo. No teste de segurança, cinco bezerros de três meses de idade foram inoculados pela via IM com o recombinante em uma dose aproximadamente 10-100 vezes a dose contida em vacinas comerciais (108,5TCID50 por animal). Os animais inoculados permaneceram saudáveis e não excretaram o vírus, confirmado pela ausência de vírus em secreções nasais e pela ausência de soroconversão em bezerros sentinelas mantidos em contato. O vírus recombinante também não foi excretado após administração de dexametasona (dia 42pi), demonstrando a incapacidade de reativar e/ou ser excretado após tentativa de reativação de infecção latente. No teste de imunogenicidade, bezerros com 8 a 10 meses de idade foram vacinados uma vez pela via IM (grupo I, n=8) ou subcutânea (SC, grupo II, n=9) com o recombinante BoHV-ΔgE viável, ou duas vezes (30 dias de intervalo) com o vírus inativado, conjugado com hidróxido de alumínio (grupo IV, n= 13) ou com MontanideTM Gel 1 (Seppic - grupo V, n=14). Como controle, três animais (grupo III) foram vacinados com o vírus parental (uma dose pela via IM). Todos os bezerros vacinados com o vírus viável desenvolveram anticorpos neutralizantes em títulos de 2 a 8 (grupo I, GMT: 2; grupo II, GMT: 1,65; grupo III, GMT: 1,65) no dia 42pv. Os demais animais desenvolveram títulos de 2 a 16 (grupo IV, GMT: 2,45) e de 2 a 128 (grupo V, GMT: 3,9). Todos os animais vacinados com o BoHV-1ΔgE permaneceram negativos no teste ELISA anti-gE. No teste de vacinação com desafio, seis bezerros (3-4 meses de idade) foram vacinados com o recombinante BoHV-1ΔgE viável na dose de 107,3TCID50/animal e quatro foram mantidos como controle. No dia 47pv, os animais foram submetidos a desafio com uma cepa heteróloga do BoHV-1 (dose de 107,5TCID50/animal) pela via intranasal. Os animais vacinados desenvolveram sinais clínicos mais brandos e por período mais curto e, excretaram vírus em menores títulos e por menos tempo do que os controles. Esses resultados demonstram que o vírus recombinante BoHV-1ΔgE é seguro/atenuado e imunogênico para bezerros, tanto na forma replicativa quanto na forma inativada. Além disso, induz resposta sorológica capaz de ser diferenciada daquela induzida pelo vírus parental. Sendo assim, o BoHV-1ΔgE apresenta propriedades adequadas para ser usado em formulações vacinais.

La fièvre aphteuse (FMD pour Foot-and-mouth disease en anglais) est une maladie très contagieuse touchant les animaux biongulés. Elle provoque des dégâts économiques considérables sur toute la surface du globe. La fièvre aphteuse est provoquée par un virus, le FMDV. Il s'agit d'un virus à ARN simple brin, de polarité positive appartenant au genre Aphtovirus dans la famille Picornaviridae. Ce virus se réplique et se propage dans l'hôte très rapidement. Dans les zones infectées, les deux principales stratégies de contrôle utilisées sont l'abattage systématique des animaux infectés et la vaccination. A l'inverse, les vaccins ne sont pas utilisés dans les zones sans FMDV, mais l'apparition d'une épidémie nécessite des stratégies pour arrêter ou au moins limiter la diffusion du virus. Actuellement, les vaccins inactivés sont les vaccins les plus utilisés pour prévenir la maladie. Cependant, ils requièrent une production à grande échelle du virus, et malgré les mesures mises en place (laboratoire sécurisé, etc), des épidémies ont été provoquées par le passé du fait de la fuite de virus FMDV. De plus, il est difficile de distinguer les animaux infectés des vaccinés (DIVA). Il est donc nécessaire de développer de nouveaux vaccins. Au cours de l'infection, la polyprotéine du virus est clivée par des protéases virales en précurseurs structural (P1) et non structuraux (P2 et P3). La protéase 3C est responsable de la majorité des clivages ; ainsi, le précurseur P1 est clivé par la 3C en trois protéines structurales, VP1, VP3 et VP0, formant le protomère de FMDV, l'unité de base de la capside virale. La protéine VP1 joue des rôles importants dans l'attachement, la protection et le sérotypage. Du fait de la présence d'un site antigénique linéaire suffisant à la protection par production d'anticorps neutralisants, VP1 est considérée comme la protéine la plus immunogénique du virus. Dans cette étude, nous avons développé un nouveau vaccin contre la FMD, basé sur l'adénovirus canin de type 2 (Cav2). L'évaluation du transfert de gène médié par Cav2 chez le porc et le bétail in vitro montre des résultats prometteurs pour le développement de vaccins pour ces espèces, notamment l'expression des antigènes de FMDV par les candidats vaccins Cav2-FMDV. L'immunogénicité de ces candidats vaccins a été montrée chez les modèles murins et cobayes. De plus, des résultats encourageants ont été observés chez le cobaye, suggérant que la réponse immunitaire élicitée par les vecteurs recombinants pouvait conduire à une protection partielle des animaux après épreuve. Cependant, une optimisation de l'immunisation doit être faite dans le but de confirmer ces résultats. Ce type de vaccin peut de plus être utilisé comme vaccin marqueur, car il ne contient aucune protéine non structurale. / Foot-and-mouth disease (FMD) is a highly contagious and economically devastating disease affecting cloven-hoofed livestock worldwide. Foot-and-mouth disease virus (FMDV) is the causative agent of FMD and one of the most infectious known animal viruses. FMDV is a positive-sense, single-stranded RNA virus belonging to the Aphthovirus genus in the Picornaviridae family. FMDV replicates and spreads in the host extremely rapidly. Slaughter and vaccination are the two major strategies used to control FMD in infected countries. In FMDV-free countries, vaccines are not used, and once the disease breaks out in these areas, strategies are required to stop or at least slow the spread of the virus. Currently, inactivated vaccines are by far the most commonly used vaccines to prevent FMD. Such vaccines, however, require large-scale production of virus, and despite the use of bio-safety facilities, vaccine production has led to inadvertent virus release and FMDV outbreak. Another limitation of inactivated vaccines is the difficulty in distinguishing between infected and vaccinated animals (DIVA). Therefore, improved vaccines need to be developed.During infection, the FMDV polyprotein is cleaved into structural (P1) and non-structural (P2 and P3) precursors by a viral protease. The non-structural 3C protein is the protease that is responsible for most of the maturation events. The P1 precursor is processed by 3C protease into three structural proteins, VP1, VP3 and VP0, forming the FMDV protomer. The VP1 protein plays important roles in attachment, protective immunity and serotype specificity. VP1 is considered to be the major immunogenic protein, as it contains a linear antigenic site that is able to induce neutralizing antibodies that suffice to protect animals against the disease.In this project, we developed a novel vaccine against FMD, based on canine adenovirus type 2 (Cav2). In vitro evaluation of Cav2 mediated gene transfer in pigs and cattle showed that the Cav2 vector holds promise for the development of vaccines for pigs and cattle. Study of these recombinant viruses indicated that Cav2-FMDV supported expression of FMDV capsid proteins in vitro. The immunogenicity of these recombinant viruses was evidenced in mouse and guinea pig models, and encouraging results in guinea pigs suggested that the immune response elicited against FMD by recombinant virus could afford partial protection against FMDV challenge. In the future, immunization with Cav2-derived vector should be optimized to confirm these preliminary results. This type of vaccine, when designed to express capsid but not non-structural proteins of FMDV, can serve as a marker vaccine against FMD.

The expanding aquaculture industry continues to encounter major challenges in the form of highly contagious aquatic viruses. Control and eradication measures targeting the most lethal and economically damaging virus-induced diseases, some of which are notifiable, currently involve ‘stamping out’ policies and surveillance strategies. These approaches to disease control are performed through mass-culling followed by restriction in the movement of fish and fish products, resulting in considerable impacts on trade. Although effective, these expensive, ethically complex measures threaten the sustainability and reputation of the aquatic food sector, and could possibly be reduced by emulating innovative vaccination strategies that have proved pivotal in maintaining the success of the terrestrial livestock industry. DIVA ‘differentiating infected from vaccinated animal’ strategies provide a basis to vaccinate and contain disease outbreaks without compromising ‘disease-free’ status, as antibodies induced specifically to infection can be distinguished from those induced in vaccinated animals. Various approaches were carried out in this study to assess the feasibility of marker/DIVA vaccination for two of the most important disease threats to the global Atlantic salmon and common carp/koi industries, i.e. infectious salmon anaemia (ISA) and koi herpesvirus disease (KHVD), respectively. Antibody responses of Atlantic salmon (Salmo salar L.), following immunisation with an ISA vaccine, administered with foreign immunogenic marker antigens (tetanus toxoid (TT), fluorescein isothiocyanate (FITC) and keyhole limpet hemocyanin (KLH)) were assessed by antigen-specific enzyme linked immunosorbent assay (ELISA). Although antibodies were induced to some markers, these were unreliable and may have been affected by temperature and smoltification. Detectable antibodies to ISAV antigen were also largely inconsistent despite low serum dilutions of 1/20 being employed for serological analysis. The poor antibody responses of salmon to the inactivated ISA vaccine suggested that DIVA vaccination is not feasible for ISA. A similar approach for KHV, utilising green fluorescent protein (GFP) as the marker, similarly failed to induce sufficiently detectable antibody responses in vaccinated carp (Cyprinus carpio L.). However, as high anti-KHV antibody titres were obtained with an inactivated KHV vaccine (≥1/3200), alternative approaches were carried out to assess the feasibility of DIVA vaccination for carp. Investigations of early KHV pathogenesis in vivo and antigen expression kinetics in vitro (0-10 days post infection (dpi)) provided valuable data for the diagnostics necessary for DIVA surveillance strategies. Following viral infection, molecular methods were shown to be the most effective approach for early detection of KHV infected fish prior to sero-conversion, during which time antibodies are not detectable. An experimental immersion challenge with KHV, however, revealed complications in molecular detection during early infection. The KHV DNA was detected in external biopsies of skin and gills, but also internally in gut and peripheral blood leukocytes ≤ 6 hours post infection (hpi), suggesting rapid virus uptake by the host. The gills and gut appeared to be possible portals of entry, supported by detection of DNA in cells by in situ hybridisation (ISH). However, many false negative results using organ biopsies occurred during the first 4 dpi. The gills were the most reliable lethal biopsy for KHV detection by various polymerase chain reaction (PCR) assays, with a PCR targeting a glycoprotein-gene (ORF56) and a real-time PCR assay being the most sensitive of the 7 methods investigated. Importantly, non-lethal mucus samples reduced the number of false negative results obtained by all KHV PCR assays during the earliest infection stages with large levels of viral DNA being detected in mucus (up to 80,000 KHV DNA genomic equivalents 200 μL-1). KHV DNA was consistently detected in the mucus as a consequence of virus being shed from the skin. Determining the expression kinetics of different viral structural proteins can be useful for DIVA serological tests. Analysis of KHV antigen expression in tissues by immunohistochemistry and indirect fluorescent antibody test was inconclusive, therefore 2 novel semi-quantitative immunofluorescence techniques were developed for determining KHV antigen expression kinetics in susceptible cell lines. During the course of KHV infection in vitro, a greater abundance of capsid antigen was produced in infected cells compared to a glycoprotein antigen (ORF56), as determined by detection with antigen-specific monoclonal antibodies (MAbs). The capsid antigen was characterised as a ~100 kDa protein by SDS-PAGE and identified as a product of KHV ORF84 by matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOF/TOF MS). This antigen was subsequently detected in the serum of >25% of KHV infected/exposed carp (6/17), as well as in carp vaccinated with a live attenuated vaccine (3/4), but not with an inactivated vaccine (0/7), by Western blot making it a potential DIVA target for an inactivated vaccine. Attempts were made to improve the sensitivity of KHV serological testing by taking advantage of recombinant proteins specific for KHV (CyHV-3), rORF62 and rORF68 and eliminating any interference by cross-reacting antibodies to carp pox (CyHV-1). These proteins successfully reacted with anti-KHV antibodies. The feasibility of DIVA strategies for KHVD was determined using these recombinant antigens to coat ELISA plates. Differential antibody responses were detected from carp sera to an internal virus tegument protein (rORF62) and external region of a transmembrane protein (rORF68). Fish vaccinated with an inactivated vaccine produced significantly lower antibody responses to rORF62 than to rORF68, whereas infected, exposed and live attenuated vaccinated fish recognised both proteins allowing differentiation between vaccinated and infected carp. However, the sensitivity of the assay was limited, possibly by high levels of natural antibodies detected at the relatively low serum dilutions (1/200) used. As the capsid antigen (ORF84) and tegument protein (ORF62) are derived from internal KHV structural proteins, they induce non-neutralising antibodies, which may be useful for DIVA strategies. Such antibodies are longer lasting than neutralising antibodies and often comprise the majority of fish anti-viral antibodies. This was noted in a fish surviving experimental challenge, which had an antibody titre of 1/10,000, but neutralising titre of 1/45. Such antigens may therefore hold potential for developing effective serological diagnostic tests for KHV and provide the potential for DIVA strategies against KHVD. Natural antibodies will, however, continue to present a challenge to the development of sensitive and reliable KHV serological tests, and hence the application of DIVA strategies.