The nucleoside phosphonates cidofovir (CDV) and (S)-9-[3-hydroxy-(2-phosphonomethoxy)propyl]adenine [(S)-HPMPA] are analogs of dCMP and dAMP, respectively. Collectively these drugs are effective inhibitors of a wide range of DNA viruses, RNA viruses, and retroviruses. Because they are nucleotide analogs, the drugs are thought to target viral polymerases and inhibit viral genome replication. However, the precise mechanism by which these drugs block viral growth remains unclear. We have studied the mechanism of action of these antivirals against three viral polymerases, vaccinia virus DNA polymerase and the reverse transcriptases from human immunodeficiency virus type 1 (HIV-1) and Moloney murine leukemia virus (MMLV). In vitro experiments using the active intracellular metabolites of CDV and (S)-HPMPA, CDV diphosphate (CDVpp) and (S)-HPMPA diphosphate [(S)-HPMPApp], respectively, showed that the drugs are substrates for each enzyme and can be incorporated into DNA without causing chain termination, although the rate of DNA elongation catalyzed by the vaccinia virus and MMLV polymerases is slowed. We have also found that incorporation of CDV or (S)-HPMPA blocked the 3′-to-5′ proofreading exonuclease activity of the vaccinia virus DNA polymerase. In addition, we determined that when these drugs are incorporated into a template DNA strand, they inhibited replication across the drug lesion. These results indicate that although CDV and (S)-HPMPA can inhibit some enzymes when incorporated into the primer strand, the main effects of drug action occur when they are incorporated into the template strand. Our findings point to a new avenue of targeted drug design, one in which nucleoside or nucleotide analogues are efficient substrates for the viral nucleic acid polymerase, do not inhibit primer strand elongation, but exert their effects in subsequent rounds of nucleic acid synthesis. / Virology

abstract: The concept of vaccination dates back further than Edward Jenner's first vaccine using cowpox pustules to confer immunity against smallpox in 1796. Nevertheless, it was Jenner's success that gave vaccines their name and made vaccinia virus (VACV) of particular interest. More than 200 years later there is still the need to understand vaccination from vaccine design to prediction of vaccine efficacy using mathematical models. Post-exposure vaccination with VACV has been suggested to be effective if administered within four days of smallpox exposure although this has not been definitively studied in humans. The first and second chapters analyze post-exposure prophylaxis of VACV in an animal model using v50ΔB13RMγ, a recombinant VACV expressing murine interferon gamma (IFN-γ) also known as type II IFN. While untreated animals infected with wild type VACV die by 10 days post-infection (dpi), animals treated with v50ΔB13RMγ 1 dpi had decreased morbidity and 100% survival. Despite these differences, the viral load was similar in both groups suggesting that v50ΔB13RMγ acts as an immunoregulator rather than as an antiviral. One of the main characteristics of VACV is its resistance to type I IFN, an effect primarily mediated by the E3L protein, which has a Z-DNA binding domain and a double-stranded RNA (dsRNA) binding domain. In the third chapter a VACV that independently expresses both domains of E3L was engineered and compared to wild type in cells in culture. The dual expression virus was unable to replicate in the JC murine cell line where both domains are needed together for replication. Moreover, phosphorylation of the dsRNA dependent protein kinase (PKR) was observed at late times post-infection which indicates that both domains need to be linked together in order to block the IFN response. Because smallpox has already been eradicated, the utility of mathematical modeling as a tool for predicting disease spread and vaccine efficacy was explored in the last chapter using dengue as a disease model. Current modeling approaches were reviewed and the 2000-2001 dengue outbreak in a Peruvian region was analyzed. This last section highlights the importance of interdisciplinary collaboration and how it benefits research on infectious diseases. / Dissertation/Thesis / Ph.D. Molecular and Cellular Biology 2011

Les virus oncolytiques sont une nouvelle classe d’agents thérapeutiques pouvant être une alternative au traitement des cancers. Plusieurs virus oncolytiques sont actuellement développés en clinique, néanmoins de nombreuses améliorations sont à apporter afin de créer une nouvelle classe de virus plus efficaces et moins toxiques. Le premier objectif de cette thèse a été d’améliorer la spécificité tumorale du virus de la vaccine via le ciblage de l’antigène MUC1 présenté à la surface des cellules tumorales. Pour cela un virus recombinant présentant à sa surface un fragment d’anticorps (scFv) dirigé contre l’antigène tumoral MUC1 a été construit et produit. Les tests in vitro n’ont toutefois pas permis de mettre en évidence un ciblage spécifique du virus recombinant. Un deuxième aspect de cette thèse a été de tester le potentiel oncolytique de virus de la famille des Poxviridae. Durant ce travail de thèse, les capacités oncolytiques de douze poxvirus, appartenant à 8 genres différents, ont été étudiés. Leurs effets sur la prolifération de cellules cancéreuses humaines ont été évalués. Les virus caractérisés par un effet oncolytique élevé ont été, par la suite, modifiés et armés par ingénierie virale afin d’augmenter leur efficacité. La dernière partie de cette thèse a été consacrée à la génération et la sélection de virus chimériques basées sur la méthode d’évolution dirigée. Cette méthode est utilisée pour mimer le processus naturel de sélection évolutif. Appliqué à la virothérapie oncolytique, ce procédé nous a permis de générer un nouveau virus oncolytique chimérique caractérisé par un potentiel anti-cancéreux amélioré. En résumé, cette thèse a permis, par des techniques d’ingénierie virale, par un criblage de nouveaux virus et par la méthode d’évolution dirigée, de créer et de sélectionner une nouvelle génération de poxvirus oncolytiques présentant une activité thérapeutique accrue avec un profil de toxicité atténué et pouvant être utilisés dans diverses indications thérapeutiques. / Oncolytiques viruses are a new class of therpeutic agents which could be an alternative for cancer treatment. Currently, several oncolytic viruses are evaluated in clinical trial, nevertheless improvements are needed to create a new class of more efficiente and less toxic viruses. The first objective of this thesis was to improved the vaccinia virus specificity through the targeting of the tumor-associated antigen MUC1. To address this goal, a recombinant virus expressing an scFv targeting the MUC1-protein was engineered and produced. However, in vitro, the demonstration of a specific targeting by the recombinant virus was not possible. A second aspect of this thesis work was to evaluate the oncolytic potential of Poxviridae family viruses. Oncolytic capacities of twelve viruses, belonging to eight genera, were evaluated. Their impact on human cancer cells was tested. In order to increase their efficacity, viruses with the highest oncolytic capacities were then modified and armed by genetic engineering. The third part of this work was devoted to the generation of chimeric viruses based on directed evolution process. This methodology is used to mimic the natural process of evolutionary selection. Applied to oncolytic virotherapy, this technique allowed the generation of a new chimeric oncolytic virus caracterised by an enhanced antitumoral potential. In summary, this thesis has allowed, through viral engineering, poxviruses screening and directed evolution methodology, the creation and selection of a new generation of oncolytic poviruses. These viruses demonstrate an increased therpeutic activity and greatest safety profil enabling their application in several therapeutic indication.

Please read the abstract in the section 00front of this document / Thesis (PhD (Genetics))--University of Pretoria, 2007. / Genetics / unrestricted

Several wild-type poxviruses have emerged as potential oncolytic viruses (OVs), including orf virus (OrfV), and vaccinia virus (VV). Oncolytic VVs have been modified to include attenuating mutations that enhance their tumour selective nature, but these mutations also reduce overall viral fitness in cancer cells. Previous studies have shown that a VV (Western Reserve) with its E3L gene replaced with the E3L homologue from, OrfV (designated VV-E3LOrfV), maintained its ability to infect cells in vitro, but was attenuated compared to its parental VV in vivo. Our goal was to determine the safety and oncolytic potential VV-E3LOrfV, compared to wild type VV and other attenuated recombinants. VV-E3LOrfV, was unable to replicate to the same titers and was sensitive to IFN compared to its parental virus and other attenuated VVs in normal human fibroblast cells. The virus was also less pathogenic when administered in vivo. Viral replication, spread and cell killing, as measures of oncolytic potential in vitro, along with in vivo efficacy, were also observed.. The Parapoxvirus, OrfV has been shown to have a unique immune-stimulation profile, inducing a number of pro-inflammatory cytokines, as well as potently recruiting and activating a number of immune cells. Despite this unique profile, OrfV is limited in its ability to replicate and spread in human cancer cells. Various strategies were employed to enhance the oncolytic efficacy of wild-type OrfV. A transient transfection/infection screen was created to determine if any of the VV host-range genes (C7L, K1L, E3L or K3L) would augment OrfV oncolysis. Combination therapy, including the use of microtubule targeting agents, Viral Sensitizer (VSe) compounds and the addition of soluble VV B18R gene product were employed to see if they also enhance OrfV efficacy. Unfortunately, none of the strategies mentioned were able to enhance OrfV.

Le virus de la variole ovine est omniprésent dans les élevages de petits ruminants dans les pays d’Afrique du Nord et particulièrement en Tunisie malgré les campagnes de vaccination annuelles mises en place par les autorités vétérinaires du pays. L’optimisation de la souche vaccinale utilisée passe par le développement de vaccins dits de nouvelle génération tels que les vaccins sous unitaires utilisant des protéines reconnues pour induire une réponse humorale protectrice chez l’animal immunisé. Ceci pourrait être une alternative aux stratégies de lutte actuelles permettant de limiter la dissémination du virus en Tunisie. Peu de données existent sur les antigènes protecteurs spécifiques des virus du genre Capripoxvirus. Ce travail de thèse a ciblé, par homologie aux protéines du virus de la vaccine, quatre protéines du genre Capripoxvirus appartenant au virus de la dermatose nodulaire contagieuse potentiellement immuno-dominantes nommées LSDV60, LSDV117, LSDV122 etLSDV141 respectivement homologues des protéines L1, A27, A33 et B5. En premier lieu, une analyse structurale in silico a permis d’identifier les domaines essentiels de chaque protéine et de vérifier le taux de conservation de ces protéines parmi différents virus appartenant à la famille des poxvirus. Une analyse structurale approfondie mettant en évidence la structure primaire, secondaire et tertiaire de la protéine A27 a été réalisée. Suite à cette étude structurale, les protéines ont été produites dans deux systèmes d’expression différents ; le système eucaryote et le système baculovirus-cellules d’insectes afin de caractériser leur antigénicité vis-à-vis de sérums provenant d’animaux immunisés ou éprouvés.La reconnaissance des protéines d’intérêt en vecteur d’expression eucaryote n’a pas été concluante. En revanche, le système d’expression BEVS a permis la production de la protéine A27 (L1, A33 et B5 encours) avec succès sous forme soluble qui a été correctement reconnue par des sérums provenant de caprins naïfs challengés. La mise en évidence de formes trimériques et hexamériques confirment sonantigénicité. Une immunodétection des peptides correspondants à la protéine A27 synthétisés surmembranes (PepScan) combinée à une analyse in silico ont permis d'identifier des zones susceptibles de constituer des régions épitopiques reconnues situés majoritairement en partie N terminale de la protéine. / The sheep pox virus is omnipresent in small ruminant farms in North African countries andparticularly in Tunisia despite the annual vaccination campaigns set up by the Tunisian veterinaryauthorities. The optimization of the used vaccine strain involves the development of the so-called newgeneration vaccines such as subunit vaccines and this, using proteins recognized to induce a protectivehumoral response in the immunized animal. This could be considered as an alternative to currentcontrol strategies limiting virus spread in Tunisia. Few data exist on protective antigens specific toviruses in the genus Capripoxvirus. By homology to vaccinia virus proteins, this thesis work hastargeted four proteins in the genus Capripoxvirus belonging to the potentially immuno-dominantcontagious nodular dermatosis virus named LSDV60, LSDV117, LSDV122 and LSDV141respectively homologues of proteins L1, A27, A33 and B5. First, an in silico structural analysis hasallowed to identify the essential domains of each protein and to check the conservation rate of theseproteins among different viruses belonging to the poxvirus family. A thorough structural analysisidentifying the primary, secondary and tertiary structure of the A27 protein was conducted. Followingthis structural study, the proteins were produced in two different expression systems, namely theeukaryotic system and the baculovirus-insect cell system, in order to characterize their antigenicity tosera from immunized or proven animals. The recognition of the proteins of interest in the eukaryoticexpression vector has not been conclusive. On the other hand, the BEVS expression systemsuccessfully allowed the production of the A27 protein (L1, A33 and B5 in progress) in a solubleform, which was correctly recognized by sera from challenged naïve goats. Identifying trimeric andhexameric forms confirms its antigenicity. An immunodetection of the peptides corresponding toprotein A27 synthesized on membranes (PepScan) combined with an in silico analysis led to identifyzones capable of constituting recognized epitopic regions located predominantly in part N-terminal ofthe protein.

No description available.

The overall theme of this dissertation is the genomic analysis of poxviruses using bioinformatics. The first analysis presented in this dissertation (Chapter 2) focuses on a new method for predicting which open reading frames (ORFs) in poxviruses are likely to be expressed. A measure that takes into account the amino acid and purine content of all predicted open reading frames (ORFs) in the genome was developed and when used on the vaccinia virus (VACV) strain Copenhagen genome (training case), the measure had a success rate of 94%. Using the measure on an extremely adenine and thymine rich entomopoxvirus (test case), 241 ORFs were found to be potentially expressed and 51 ORFs were likely not expressed although further biochemical experiments will be required to confirm this result. The second analysis of this dissertation (Chapter 3) focuses on determining the nature of an interesting background pattern similar to a set of stripes that was observed while analyzing a self-dotplot of the molluscum contagiosum virus genome. These stripe regions were further analyzed and were found to have a nucleotide composition and amino acid usage that was different to the remainder of the genome. Given this differing nucleotide and amino acid usage, the genes contained in these stripe regions are thought to have been recently acquired from the host or another virus, making these regions similar to bacterial pathogenicity islands. The third analysis of this dissertation (Chapter 4) focuses on predicting the function of “unknown” poxvirus proteins by using a hidden Markov model (HMM) comparison search tool to scan all “unknown” proteins in the VACV genome looking for any database matches that may have been missed by conventional approaches (BLASTp and PSI-BLAST). One protein, the VACV G5R protein, in this scan showed a promising hit (96% probability) to an archaeal flap endonuclease (FEN-1) protein. A structural model of the G5R protein was created and subsequently compared to the crystal structure of the human FEN-1 protein and was found to be highly conserved in both secondary and tertiary structure and with three of the five main features of the FEN-1 protein including the active site suggesting that the G5R protein should be classified as a flap endonuclease protein. Related to the analysis in Chapter 4, are the results presented in Chapter 5 of this dissertation that focus on locating a protein encoded by the VACV genome that is similar to proliferating cell nuclear antigen (PCNA). Knowing that the FEN-1 protein requires PCNA as an intermediary to contact DNA, the genome of VACV was scanned using InterProScan in order to identify any potential proteins that were similar to PCNA. One protein (VACV G8R) was identified and subsequently modeled and compared to the crystal structure of the human PCNA protein. The secondary and tertiary structure was highly conserved between the two proteins suggesting that the G8R protein should be classified as a sliding clamp similar to human PCNA.

In dieser Arbeit wurden Vektorimpfstoffe auf der Basis rekombinanter Vacciniaviren hinsichtlich ihrer Eignung zur Immunisierung gegen Infektionen mit Respiratorischen Synzytialviren (RSV) untersucht. Hierfür standen genetisches Material und Viruspräparationen des Respiratorischen Synzytialvirus des Rindes (BRSV, Stamm Odijk) sowie des Respiratorischen Synzytialvirus des Menschen (HRSV, Subtyp A2) sowie rekombinante Vacciniaviren MVA-HRSV-F bzw. MVA-HRSV-G zur Verfügung. Rekombinante MVA-Viren, welche die Gene der BRSV-Oberflächenproteine G und F (MVA-BRSV-F, MVA-BRSV-G, MVA-BRSV-Gneu), sowie Viren in welchen die Fremdgensequenzen durch Deletion wieder entfernt sind (Revertante Viren MVA-∆BRSV-F und MVA-∆BRSV-G), wurden gentechnologisch hergestellt. Alle rekombinanten MVA-Viren wurden molekular-virologisch charakterisiert und dienten zur Gewinnung und Prüfung von Testimpfstoffen im Tiermodell. Die Untersuchungen zeigen: 1. Alle neu konstruierten rekombinanten MVA-BRSV-Viren produzierten nach Infektion von Zellkulturen die erwünschten Zielantigene, die BRSV-Glykoproteine F und G. Für das durch MVA-Expression hergestellte BRSV-F-Glykoprotein konnte außerdem die biologische Funktionalität in einem Fusionstest in infizierten HeLa-Zellen nachgewiesen werden. 2. Die Charakterisierung der Genome aller MVA-BRSV- sowie MVA-HRSV-Vektorviren bestätigte die exakte Insertion der Fremdgensequenzen im anvisierten Genombereich und zeigte die genetische Stabilität der Virusisolate nach Passagierung. 3. Bei der Untersuchung des Wachstumsverhaltens von MVA-BRSV-F und MVA-BRSV-G zeigte sich die eingeschränkte Vermehrungsfähigkeit des Virus MVA-BRSV-G. Die Konstruktion und Untersuchung der revertanten Viren MVA-∆BRSV-F und MVA-∆BRSV-G belegte die Koproduktion des G-Proteins als Ursache des verminderten Replikationsvermögens. Dieser für ein mögliches Impfvirus erhebliche Nachteil konnte durch die Verwendung eines moderateren Vacciniavirus-Promotors zur Fremdgenexpression (rekombinantes Virus MVA-BRSV-Gneu) behoben werden. 4. Die Prüfung von Testimpfstoffen auf der Grundlage der rekombinanten MVA-HRSV-Viren in einem Maus-HRSV-Infektionsmodell zeigte, dass MVA-HRSV-Impfstoffe, im Gegensatz zu Impfstoffen aus mit Formalin-inaktiviertem HRSV, Immunantworten mit einem ausgewogenen TH1/TH2-assoziierten Zytokinprofil induzierten. Eine infolge von Immunisierung verstärkte Einwanderung eosinophiler Zellen (Marker für Immunpathogenese) in die Lungen HRSV-infizierter Tiere, konnte nach MVA-Impfung nicht beziehungsweise in nur sehr geringem Ausmaß festgestellt werden (OLSZEWSKA et al. 2004). 5. Wichtige erste Daten hinsichtlich der Verträglichkeit, Immunogenität und Schutzwirkung rekombinanter Impfstoffe auf der Basis von MVA-BRSV-F und MVA-BRSV-G konnten in einem Kälber BRSV-Infektionsmodell erhoben werden. Die zweimalige Immunisierung mit MVA-Impfstoff verlief bei allen Tieren ohne feststellbare Nebenwirkungen und die Anregung Vaccinia- bzw. BRSV-F-spezifischer Antikörper bestätigte die Immunogenität der Vektorvakzinen. Schließlich belegten klinische Daten, insbesondere die fehlende Fieberreaktion bei Impflingen nach BRSV-Belastungsinfektion, die Schutzwirkung der MVA-BRSV-Impfstoffe. Insgesamt unterstützen die erzielten Ergebnisse dieser Arbeiten die weitere präklinische und klinische Untersuchung von MVA-Vektorimpfstoffen zur wirksameren und sichereren Bekämpfung von Infektionen mit Respiratorischen Synzytialviren. / This study investigated vector vaccines based on recombinant vaccinia virus MVA for their suitability to immunize against infections with respiratory syncytial viruses. Genetic material and virus stocks of bovine respiratory syncytial virus (BRSV, Strain Odijk) and human respiratory syncytial virus (HRSV, Strain A2) and recombinant vaccinia viruses MVA-HRSV-F and MVA-HRSV-G were provided and used in this study. The project work included the genetical engineering of recombinant MVA expressing gene sequences encoding the BRSV surface proteins G and F (MVA-BRSV-F, MVA-BRSV-G, MVA-BRSV-Gneu) and the secondary generation of mutant viruses in which recombinant gene sequences have been removed (revertant viruses MVA-∆BRSV-F, MVA-∆BRSV-G). All recombinant MVA were carefully characterized in in vitro experiments and served for generation of vaccine preparations being tested in animal model systems. The investigations demonstrate: 1. All recombinant MVA-BRSV viruses produced the target antigens (BRSV-F and -G proteins) upon tissue culture infections. Functional activity of BRSV-F protein was demonstrated in a cell fusion assay using virus-infected HeLa cells. 2. The characterization of the genomes of all MVA recombinant viruses confirmed the correct insertion of foreign gene sequences into the target site of the MVA genome and demonstrated the genetic stability of the vector viruses upon tissue culture passage. 3. In vitro studies on virus growth revealed a reduced replicative capacity of the recombinant virus MVA-BRSV-G. Construction and growth analysis of revertant viruses MVA-∆BRSV-F and MVA-∆BRSV-G demonstrated that over expression of BRSV-G protein caused this replication deficiency which could be avoided by using a more moderate vaccinia virus promoter for transcriptional control of recombinant gene expression (recombinant virus MVA-BRSV-Gneu). 4. Upon characterization in a mouse-HRSV challenge model candidate vaccines based on recombinant MVA-HRSV viruses, in contrast to formalin inactivated HRSV, and induced a well balanced TH1 and TH2 cytokine profile. In addition, none of the MVA-HRSV-F vaccinated animals and only two of the MVA-HRSV-G immunized mice showed low-level eosinophilia in the lungs after HRSV challenge infection (OLSZEWSKA et al. 2004). 5. Vaccination experiments in the calf-BRSV challenge model generated first relevant data on safety, immunogenicity and protective capacity of MVA-BRSV recombinant vaccines. The repeated application of MVA vaccine was well tolerated by all vaccinated animals and the induction of vaccinia- and BRSV-F-specific antibody responses confirmed the immunogenicity of the MVA vector vaccines. Moreover, clinical data (lack of fever response in vaccines) suggested the protective capacity of MVA-BRSV immunization upon BRSV challenge. The obtained results from these studies clearly support further preclinical and clinical evaluation of recombinant MVA candidate vaccines to immunize against disease caused by RSV infections in cattle and humans.

In dieser Arbeit wurden Vektorimpfstoffe auf der Basis rekombinanter Vacciniaviren hinsichtlich ihrer Eignung zur Immunisierung gegen Infektionen mit Respiratorischen Synzytialviren (RSV) untersucht. Hierfür standen genetisches Material und Viruspräparationen des Respiratorischen Synzytialvirus des Rindes (BRSV, Stamm Odijk) sowie des Respiratorischen Synzytialvirus des Menschen (HRSV, Subtyp A2) sowie rekombinante Vacciniaviren MVA-HRSV-F bzw. MVA-HRSV-G zur Verfügung. Rekombinante MVA-Viren, welche die Gene der BRSV-Oberflächenproteine G und F (MVA-BRSV-F, MVA-BRSV-G, MVA-BRSV-Gneu), sowie Viren in welchen die Fremdgensequenzen durch Deletion wieder entfernt sind (Revertante Viren MVA-∆BRSV-F und MVA-∆BRSV-G), wurden gentechnologisch hergestellt. Alle rekombinanten MVA-Viren wurden molekular-virologisch charakterisiert und dienten zur Gewinnung und Prüfung von Testimpfstoffen im Tiermodell. Die Untersuchungen zeigen: 1. Alle neu konstruierten rekombinanten MVA-BRSV-Viren produzierten nach Infektion von Zellkulturen die erwünschten Zielantigene, die BRSV-Glykoproteine F und G. Für das durch MVA-Expression hergestellte BRSV-F-Glykoprotein konnte außerdem die biologische Funktionalität in einem Fusionstest in infizierten HeLa-Zellen nachgewiesen werden. 2. Die Charakterisierung der Genome aller MVA-BRSV- sowie MVA-HRSV-Vektorviren bestätigte die exakte Insertion der Fremdgensequenzen im anvisierten Genombereich und zeigte die genetische Stabilität der Virusisolate nach Passagierung. 3. Bei der Untersuchung des Wachstumsverhaltens von MVA-BRSV-F und MVA-BRSV-G zeigte sich die eingeschränkte Vermehrungsfähigkeit des Virus MVA-BRSV-G. Die Konstruktion und Untersuchung der revertanten Viren MVA-∆BRSV-F und MVA-∆BRSV-G belegte die Koproduktion des G-Proteins als Ursache des verminderten Replikationsvermögens. Dieser für ein mögliches Impfvirus erhebliche Nachteil konnte durch die Verwendung eines moderateren Vacciniavirus-Promotors zur Fremdgenexpression (rekombinantes Virus MVA-BRSV-Gneu) behoben werden. 4. Die Prüfung von Testimpfstoffen auf der Grundlage der rekombinanten MVA-HRSV-Viren in einem Maus-HRSV-Infektionsmodell zeigte, dass MVA-HRSV-Impfstoffe, im Gegensatz zu Impfstoffen aus mit Formalin-inaktiviertem HRSV, Immunantworten mit einem ausgewogenen TH1/TH2-assoziierten Zytokinprofil induzierten. Eine infolge von Immunisierung verstärkte Einwanderung eosinophiler Zellen (Marker für Immunpathogenese) in die Lungen HRSV-infizierter Tiere, konnte nach MVA-Impfung nicht beziehungsweise in nur sehr geringem Ausmaß festgestellt werden (OLSZEWSKA et al. 2004). 5. Wichtige erste Daten hinsichtlich der Verträglichkeit, Immunogenität und Schutzwirkung rekombinanter Impfstoffe auf der Basis von MVA-BRSV-F und MVA-BRSV-G konnten in einem Kälber BRSV-Infektionsmodell erhoben werden. Die zweimalige Immunisierung mit MVA-Impfstoff verlief bei allen Tieren ohne feststellbare Nebenwirkungen und die Anregung Vaccinia- bzw. BRSV-F-spezifischer Antikörper bestätigte die Immunogenität der Vektorvakzinen. Schließlich belegten klinische Daten, insbesondere die fehlende Fieberreaktion bei Impflingen nach BRSV-Belastungsinfektion, die Schutzwirkung der MVA-BRSV-Impfstoffe. Insgesamt unterstützen die erzielten Ergebnisse dieser Arbeiten die weitere präklinische und klinische Untersuchung von MVA-Vektorimpfstoffen zur wirksameren und sichereren Bekämpfung von Infektionen mit Respiratorischen Synzytialviren. / This study investigated vector vaccines based on recombinant vaccinia virus MVA for their suitability to immunize against infections with respiratory syncytial viruses. Genetic material and virus stocks of bovine respiratory syncytial virus (BRSV, Strain Odijk) and human respiratory syncytial virus (HRSV, Strain A2) and recombinant vaccinia viruses MVA-HRSV-F and MVA-HRSV-G were provided and used in this study. The project work included the genetical engineering of recombinant MVA expressing gene sequences encoding the BRSV surface proteins G and F (MVA-BRSV-F, MVA-BRSV-G, MVA-BRSV-Gneu) and the secondary generation of mutant viruses in which recombinant gene sequences have been removed (revertant viruses MVA-∆BRSV-F, MVA-∆BRSV-G). All recombinant MVA were carefully characterized in in vitro experiments and served for generation of vaccine preparations being tested in animal model systems. The investigations demonstrate: 1. All recombinant MVA-BRSV viruses produced the target antigens (BRSV-F and -G proteins) upon tissue culture infections. Functional activity of BRSV-F protein was demonstrated in a cell fusion assay using virus-infected HeLa cells. 2. The characterization of the genomes of all MVA recombinant viruses confirmed the correct insertion of foreign gene sequences into the target site of the MVA genome and demonstrated the genetic stability of the vector viruses upon tissue culture passage. 3. In vitro studies on virus growth revealed a reduced replicative capacity of the recombinant virus MVA-BRSV-G. Construction and growth analysis of revertant viruses MVA-∆BRSV-F and MVA-∆BRSV-G demonstrated that over expression of BRSV-G protein caused this replication deficiency which could be avoided by using a more moderate vaccinia virus promoter for transcriptional control of recombinant gene expression (recombinant virus MVA-BRSV-Gneu). 4. Upon characterization in a mouse-HRSV challenge model candidate vaccines based on recombinant MVA-HRSV viruses, in contrast to formalin inactivated HRSV, and induced a well balanced TH1 and TH2 cytokine profile. In addition, none of the MVA-HRSV-F vaccinated animals and only two of the MVA-HRSV-G immunized mice showed low-level eosinophilia in the lungs after HRSV challenge infection (OLSZEWSKA et al. 2004). 5. Vaccination experiments in the calf-BRSV challenge model generated first relevant data on safety, immunogenicity and protective capacity of MVA-BRSV recombinant vaccines. The repeated application of MVA vaccine was well tolerated by all vaccinated animals and the induction of vaccinia- and BRSV-F-specific antibody responses confirmed the immunogenicity of the MVA vector vaccines. Moreover, clinical data (lack of fever response in vaccines) suggested the protective capacity of MVA-BRSV immunization upon BRSV challenge. The obtained results from these studies clearly support further preclinical and clinical evaluation of recombinant MVA candidate vaccines to immunize against disease caused by RSV infections in cattle and humans.