Worldwide, 3.575 million people die each year from water-related diseases. The water and sanitation crisis claims more lives than any warfare and is predicted to be one of the biggest global challenges of this century. The rapid, accurate detection of viral pathogens from environmental samples is an ongoing and pertinent challenge in biological engineering. Currently employed methods are lacking in either efficiency or specificity. Here we explore a novel method for virus detection and concurrently use this method to learn more about the very early stages of the virus infection process. The method combines Fourier transform infrared (FTIR) spectroscopy, a method of visualizing molecules based on changes in vibration of particles, and mammalian cells as the biosensor. This method is used to detect and investigate viruses from the family picornaviridae, chosen due to their public health burden and their widespread presence in environmental samples, especially water sources. This family includes the Polioviruses, echoviruses and Coxsackieviruses, among others, many of which are human pathogens.The research outlined in this dissertation is aimed at developing and implementing a new cell-based biosensor that combines the advantages of FTIR spectroscopy with the ability of buffalo green monkey kidney (BGMK) cells to sense diverse stimuli, including infective enteroviruses. The goal of developing this biosensor is outlined in the first paper. The second paper focuses on the application of advanced statistical methods to analyze the spectra to discriminate different viral infections in BGMK cells. Finally, we designed a non-reactive metal biochamber to use with attenuated total reflectance-FTIR. This allowed near-continuous acquisition of real-time spectral data for the study of biochemical changes in mammalian cells caused by poliovirus (PV1) infection. This system is capable of tracking changes in cell biochemistry in minute intervals for many hours at a time.This work demonstrates the feasibility of FTIR spectroscopy in combination with the broad sensitivity of mammalian cells for potential use in the detection of infective viruses from environmental samples. We envision this method being extended to high throughput, automated systems to screen for viruses or other toxins in drinking water systems and medical applications.

This diploma thesis deals with a development of a strategy for data evaluation generated by next-generation sequencing. Using bioinformatics tools such as Galaxy, Velvet and Enterovirus genotyping tool new aproach of data processing was optimized. There were 22 samples analyzed which of 10 were grown on cell culture. Remaining 12 were obtained from real stool samples. All samples were taken from children at the highest genetic risk of type 1 diabetes. All of them were enterovirus positive. Enteroviruses and their following infections have been suspecting to be involved in ehiology of type 1 diabetes for a long time. That's a disease resulting to an absolut insulin deficiency due to autoimmune destruction of pancreatic beta cells. Genetic components seems to be relatively well defined (the HLA, INS, STLA4, PTPN22, CTLA4, IFIH1 and numerous other genes), the environmental part of the etiology remains obscured. We were able to assemble 22 genomes de novo. However, there were numerous gaps among the particular contigs. For the first nine samples these gaps were complemented by Sanger sequencing. Nine full-length genomes were assempled this way. The main contribution of this work was to create a universal process of analyzing data from next-generation sequencing. This has already been using for further...

近年来肠病毒71亚型（EV71）的大规模流行已成为全世界特别是亚太地区的一个严重的公共卫生问题。EV71感染可以引起腹泻，皮疹，手足口病等等一些自愈性疾病。然而在部分儿童患者中，EV71可能导致严重的神经性疾病。目前，关于EV71感染后宿主细胞的反应机制的报导比较少。在本次研究中，我们运用蛋白组学方法对EV71感染后的人横纹肌瘤细胞的蛋白表达情况进行了分析，最终发现了42个差异表达的蛋白（>2倍的变化，P <0.05），其中21个下调， 21个上调。进一步分析表明，这些蛋白主要参与了细胞内代谢，生物学调控，细胞构建，信息传递和细胞死亡的调控。 接下来我们选择了其中一个变化比较大的蛋白：HSP27，对其功能进行了深入分析。我们的研究结果显示：EV71感染的早期阶段，HSP27在转录和翻译水平上都有明显上调。降低HSP27表达可以减少EV71的复制，过表达HSP27则可以提高病毒复制。通过使用特异的磷酸化蛋白抗体，我们发现HSP27第15位以及78位的丝氨酸有明显的磷酸化修饰，而82位的丝氨酸则没有发生改变。使用p38激酶抑制剂预先处理细胞可以降低HSP27的磷酸化修饰，从而抑制EV71的复制。进一步分析表明，HSP27可以帮助EV71蛋白酶2A对真核翻译起始因子eIF4G的剪切，从而加强病毒自身蛋白的翻译，最终促进了病毒的感染。这项研究结果阐明了宿主细胞EV71的反应机制，有利于我们对病毒致病机制的研究，并为EV71的抗病毒研究提供了一个新的药物靶标。 / The outbreaks of enterovirus 71 (EV71) infections have become a major public health issue worldwide, especially in the Asia-Pacific region. EV71 infection can be asymptomatic or cause diarrhea, rashes, and hand, foot, and mouth disease (HFMD). However, EV71 can also cause severe neurological disease even death. To date, little is known about the molecular mechanisms of the host response to EV71 infection. In this study, the expression patterns of host genes in EV71 infected human rhabdomyosarcoma cells were analyzed by using two-dimensional proteomics assays. In total, 42 protein spots were found to be differentially expressed (>2 fold changes, p<0.05) in three pairs of gels, of which 21 proteins were found to be down-regulated while 21 were up-regulated. Data analysis suggested that proteins associated with metabolic process, biological regulation, cellular component organization, cell communication and death were most modified. HSP27, one of the most altered proteins during EV71 infection, was selected to determine its fundamental roles upon EV71 infection. We show that HSP27 is rapidly up-regulated both at the transcriptional and the translational levels at the early stage of EV71 infection. Depleting cellular HSP27 expression reduced EV71 replication, while over-expression of HSP27 greatly enhanced viral infection. By using the phosphorylated specific antibodies, serine residues 15, 78, but not the 82 were found to be phosphorylated during EV71 infection. The phosphorylation depended on the activation of the mitogen-activated protein kinase p38 signaling pathway. After treating with p38 kinase inhibitors, EV71 replication was coordinately decreased. Further analysis showed that HSP27 affected the protease 2A mediated eIF4G cleavage and assisted the IRES driven translation, thus facilitated the EV71 replication. The findings in this work not only provided a global view of the host responses to EV71 infection, but demonstrated HSP27 to be a valid target for anti-EV71 drug development. / Detailed summary in vernacular field only. / Yi, Lina. / "September 2012." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 94-103). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgement --- p.iv / Publications --- p.v / Table of Contents --- p.vii / List of Tables and Figures --- p.x / List of Abbreviation --- p.xii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Enterovirus 71 --- p.2 / Chapter 1.1.1 --- Clinical features --- p.2 / Chapter 1.1.2 --- Molecular epidemiology of EV71 --- p.5 / Chapter 1.1.3 --- The virology of EV71 --- p.8 / Chapter 1.1.4 --- Pathogenesis --- p.18 / Chapter 1.1.5 --- Treatment of EV71 infection --- p.20 / Chapter 1.2 --- The heat shock protein 27 --- p.23 / Chapter 1.2.1 --- Properties of HSP27 --- p.23 / Chapter 1.2.2 --- Functions of Hsp27 --- p.26 / Chapter 1.2.5 --- Phosphorylation of Hsp27 --- p.28 / Chapter 1.2.6 --- Hsp27 and Viral infection --- p.31 / Chapter 1.3 --- Thesis hypothesis and objective --- p.33 / Chapter Chapter 2 --- Materials and Methods --- p.34 / Chapter 2.1 --- Cells and Virus propagation --- p.35 / Chapter 2.2 --- Viral infection --- p.35 / Chapter 2.3 --- 2-DE and image analysis --- p.36 / Chapter 2.4 --- MALDI-TOF-MS --- p.37 / Chapter 2.5 --- Database analysis --- p.38 / Chapter 2.6 --- Bioinformatic analysis --- p.38 / Chapter 2.7 --- Plasmids --- p.39 / Chapter 2.8 --- siRNA synthesis --- p.41 / Chapter 2.9 --- Transfection and cell treatment --- p.41 / Chapter 2.10 --- RNA extraction and cDNA synthesis --- p.41 / Chapter 2.11 --- Real-Time Quantitative PCR --- p.42 / Chapter 2.12 --- Western Blotting analysis --- p.44 / Chapter 2.13 --- Luciferase assays --- p.44 / Chapter 2.14 --- Statistical Analysis --- p.45 / Chapter Chapter 3 --- Proteomic analysis of cellular protein alterations in response to EV71 infection --- p.46 / Chapter 3.1 --- Introduction --- p.47 / Chapter 3.2 --- Results --- p.48 / Chapter 3.2.1 --- EV71 infection of the RD cells --- p.48 / Chapter 3.2.2 --- 2-DE profiling of EV71 infected and non-infected RD cells --- p.49 / Chapter 3.2.3 --- Identification of differentially expressed proteins --- p.50 / Chapter 3.2.4 --- Functional classification --- p.52 / Chapter 3.2.5 --- GO enrichment analysis --- p.54 / Chapter 3.2.6 --- Protein validation by Western blot --- p.56 / Chapter 3.3 --- Discussion --- p.57 / Chapter Chapter 4 --- HSP27 effects on EV71 infection --- p.62 / Chapter 4.1 --- Introduction --- p.63 / Chapter 4.2 --- Results --- p.64 / Chapter 4.2.1 --- Increased Hsp27 expression in EV71 infected cells --- p.64 / Chapter 4.2.2 --- Suppression of Hsp27 inhibits EV71 replication --- p.65 / Chapter 4.2.3 --- Over-expression of Hsp27 increases EV71 replication --- p.66 / Chapter 4.2.4 --- Hsp27 is rapidly phosphorylated during EV71 infection --- p.67 / Chapter 4.2.5 --- Pathways involved in Hsp27 phosphorylation --- p.68 / Chapter 4.2.6 --- Role of Hsp27 phosphorylation during EV71 infection --- p.68 / Chapter 4.3 --- Discussion --- p.70 / Chapter Chapter 5 --- HSP27 facilitate EV71 IRES driven translation --- p.75 / Chapter 5.1 --- Introduction --- p.76 / Chapter 5.2 --- Results --- p.79 / Chapter 5.2.1 --- Hsp27 increase viral IRES activity --- p.79 / Chapter 5.2.2 --- Hsp27 affects EV71 2A mediated eIF4G cleavage --- p.80 / Chapter 5.3 --- Discussion --- p.82 / Chapter Chapter 6 --- Summary and Perspectives --- p.87 / Chapter 6.1 --- Summary --- p.88 / Chapter 6.2 --- Perspectives --- p.89 / Reference --- p.93

Lu, Jing. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 119-138). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

<p>Enterovirus (EV) infections have been associated with the pathogenesis of Type 1 Diabetes (T1D). However, the pathway(s) by which EV may induce or accelerate diabetes is not well understood. The purpose of this thesis was to obtain new information on the mechanism by which EV infections, with different strains of EV, could cause damage to the insulin-producing β-cells in isolated human islets and in a rat insulin-producing cell line (RINm5F). </p><p>Infection with EV strains isolated from T1D patients revealed replication/cell destruction in human islets and EV-like particles in the cytoplasm of the β-cell and infection with the isolates affected the release of insulin in response to glucose stimulation as early as three days post infection, before any decrease in cell viability was observed. A decrease in the induction/secretion of the chemokine RANTES in human islets during EV infection was also detected. When islets were cultured with nicotinamide (NA) the secretion of RANTES was increased irrespectively if the islets were infected or not. In addition, the degree of virus-induced cytolysis of human islets was reduced by NA, suggesting an antiviral effect of NA. Infection with EV strains revealed permissiveness to islet-derived cells. </p><p>All EV strains used for infection were able to replicate in the RIN cell clusters (RCC) but not in the RIN cells that were cultured as a monolayer. This might be due to the differences in expression of the Coxsackie-adenovirus receptor (CAR), which only could be detected on the RCC. Infection of RCC with a CBV-4 strain did not affect cell viability and did not induce nitric oxide (NO) production alone or with the addition of IFN-γ. This was in contrast to the results obtained with synthetic dsRNA, poly(IC), which induced NO, suggesting that synthetic dsRNA does not mimic enteroviral intermediate dsRNA.</p><p>During analyses performed with the samples from a family where the mother and one son where diagnosed with T1D on the same day, the results showed that the whole family had a proven EV infection at the time diagnosis.</p><p>To conclude, the ability of EV strains to replicate in RIN cells is dependent on the growth pattern of the cells and this may be due to the upregulation and/or changed expression pattern of CAR in these cells. In the RIN cells, contrary to artificial dsRNA, viral dsRNA does not induce NO. The isolated EV virus strains used were able to infect and affect human pancreatic islets in vitro. The chemokine RANTES is reduced during an EV infection of human pancreatic islets and NA causes upregulation of RANTES in infected and uninfected islets. </p>

This thesis focuses on enteroviral effects on human pancreatic islets. Most knowledge of viral effects on host cells relies on studies of immortalized cell lines or animal models. The islets represent a fundamentally different and less well studied cellular host. Also, enterovirus has been implicated in the etiology of type 1 diabetes (T1D). We show that when enterovirus replicates in human islets it activates innate immunity genes and induces secretion of the chemokines MCP-1 and IP-10. An important difference in activation of innate immunity by replicating EV and synthetic dsRNA is suggested, since the chemokine secretion induced by EV infection but not by dsRNA is reduced by female sex hormone. We also demonstrate a direct antiviral effect of nicotinamide, and even though this substance failed to prevent T1D in a large-scale study, this finding could have implications for the treatment/prevention of virus- and/or immune-mediated disease. We also had access to human pancreata from two organ donors with recent onset T1D and several donors with T1D-related autoantibodies, which gave us the opportunity to study ongoing pathogenic processes at and before the onset of T1D. Despite this, we could neither confirm nor reject the hypothesis that EV is involved in T1D development. Several observations, such as ultrastructural remodeling of the beta cell, activation of innate immunity, and immunopositivity to EV capsid protein 1, supported an ongoing virus infection, but direct evidence is still lacking. An interesting finding in the donors with recent onset T1D was that the islets were positively stained for insulin, but did not secrete insulin in response to glucose-stimulation. A similar effect was observed in EV-infected islets in vitro; EV destroyed islet function and insulin gene expression, but the islets still stained positive for insulin. This may be indicative of that a functional block in addition to beta cell destruction is involved in T1D pathogenesis. In conclusion, these studies of EV in isolated human islets in vitro support that this virus can cause T1D in vivo, but future studies will have to show if and how frequently this happens.

Enterovirus (EV) infections have been associated with the pathogenesis of Type 1 Diabetes (T1D). However, the pathway(s) by which EV may induce or accelerate diabetes is not well understood. The purpose of this thesis was to obtain new information on the mechanism by which EV infections, with different strains of EV, could cause damage to the insulin-producing β-cells in isolated human islets and in a rat insulin-producing cell line (RINm5F). Infection with EV strains isolated from T1D patients revealed replication/cell destruction in human islets and EV-like particles in the cytoplasm of the β-cell and infection with the isolates affected the release of insulin in response to glucose stimulation as early as three days post infection, before any decrease in cell viability was observed. A decrease in the induction/secretion of the chemokine RANTES in human islets during EV infection was also detected. When islets were cultured with nicotinamide (NA) the secretion of RANTES was increased irrespectively if the islets were infected or not. In addition, the degree of virus-induced cytolysis of human islets was reduced by NA, suggesting an antiviral effect of NA. Infection with EV strains revealed permissiveness to islet-derived cells. All EV strains used for infection were able to replicate in the RIN cell clusters (RCC) but not in the RIN cells that were cultured as a monolayer. This might be due to the differences in expression of the Coxsackie-adenovirus receptor (CAR), which only could be detected on the RCC. Infection of RCC with a CBV-4 strain did not affect cell viability and did not induce nitric oxide (NO) production alone or with the addition of IFN-γ. This was in contrast to the results obtained with synthetic dsRNA, poly(IC), which induced NO, suggesting that synthetic dsRNA does not mimic enteroviral intermediate dsRNA. During analyses performed with the samples from a family where the mother and one son where diagnosed with T1D on the same day, the results showed that the whole family had a proven EV infection at the time diagnosis. To conclude, the ability of EV strains to replicate in RIN cells is dependent on the growth pattern of the cells and this may be due to the upregulation and/or changed expression pattern of CAR in these cells. In the RIN cells, contrary to artificial dsRNA, viral dsRNA does not induce NO. The isolated EV virus strains used were able to infect and affect human pancreatic islets in vitro. The chemokine RANTES is reduced during an EV infection of human pancreatic islets and NA causes upregulation of RANTES in infected and uninfected islets.

Enteroviruses belong to the Picornaviridae family and are small icosahedral viruses with RNA genomes of positive polarity, containing a single open reading frame. They mostly cause mild or asymptomatic infections, but also a wide array of diseases including: poliomyelitis, encephalitis, gastroenteritis, aseptic meningitis, myocarditis, hand-foot-and-mouth disease, hepatitis and respiratory diseases, ranging from severe infections to the common cold. The projects described in this thesis have been carried out through reverse genetic studies of Enterovirus B and Rhinovirus C.                   In Papers I and II, a cassette vector was used to study recombination and translation of the RNA genome. It was found that the non-structural coding region could replicate when combined with the structural protein-coding region of other viruses of the same species. Furthermore, the genome could be translated and replicated without the presence of the structural protein-coding region. Moreover, it was found that when two additional nucleotides were introduced, shifting the reading frame, the virus could revert to the original reading frame, restoring efficient replication. In Paper III, a vector containing the genome of echovirus 5 was altered to produce an authentic 5’end of the in vitro transcribed RNA, which increased efficiency of replication initiation 20 times. This result is important, as it may lead to more efficient oncolytic virotherapy. An authentic 5’end was further used in Paper IV, where replication of Rhinovirus C in cell lines was attempted. Although passaging of the virus was unsuccessful, the genome was replicated and cytopathic effect induced after transfection. The restriction of efficient replication was therefore hypothesized to lie in the attachment and entry stages of the replication cycle. In Paper V, a cytolytic virus was found to have almost 10 times larger impact on gene expression of the host cell than a non-cytolytic variant. Furthermore, the lytic virus was found to build up inside the host cell, while the non-cytolytic virus was efficiently released.                   As a whole, this thesis has contributed to a deeper understanding of replication of enteroviruses, which may prove important in development of novel vaccines, antiviral agents and oncolytic virotherapies.

Human enterovirus 71 (HEV71) is a member of the Human Enterovirus A species within the Family Picornaviridae. Since 1997, HEV71 has emerged as a major cause of epidemics of hand, foot and mouth disease (HFMD) associated with severe neurological disease in the Asia-Pacific region. At the present time, little is known about the pathogenesis of acute neurological disease caused by HEV71. The major aim of this study was to generate infectious cDNA clones of HEV71 and use them as tools for investigating the biology of HEV71 and molecular genetics of HEV71 virulence and pathogenesis. Two infectious cDNA clones of HEV71 clinical isolates, 26M (genotype B3) and 6F (genotype C2) were successfully constructed using a low copy number plasmid vector and an appropriate bacterial host. Transfection of cDNA clones or RNA transcripts derived from these clones produced infectious viruses. Phenotypic characterisation of clone-derived viruses (CDV-26M and CDV-6F) was performed, and CDV-26M and CDV-6F were found to have indistinguishable phenotypes compared to their wild type viruses. Strains HEV71-26M and HEV71-6F were found to have distinct cell culture growth phenotypes. To identify the genome regions responsible for the growth phenotypes of the two strains a series of chimeric viruses were constructed by exchanging the 5„S untranslated region (5„S UTR), structural protein (P1), and nonstructural protein (P2 and P3) gene regions using infectious cDNA clones of both virus strains. Analysis of reciprocal virus chimeras revealed that the 5„S UTR of both strains were compatible but not responsible for the observed phenotypes. Both the P1 and P2-P3 genome regions influence the HEV71 growth phenotype in cell culture, phenotype expression is dependent on specific P1/P2-P3 combinations and is not reciprocal. In the previous study, in order to investigate the pathogenesis of HEV71 infection, a mouse HEV71 model was developed using a mouse-adapted variant of HEV71-26M. Mouse-adapted strain MP-26M caused fore- and/or hindlimb paralysis in mice, whereas HEV71-26M-infected mice did not develop clinical signs of infection at any virus dose or route of inoculation tested. In this study, the molecular basis of mouse adaptation by HEV71 was identified. Nucleotide sequence analysis of HEV71-26M and MP-26M revealed three point mutations in the open reading frame, each resulting in an amino acid substitution in the VP1, VP2 and 2C proteins; no mutations were identified in the untranslated regions of the genome. To determine which of the three amino acid mutations were responsible for the adaptation and virulence of HEV71-26M in mice, recombinant cDNA clones containing one, or a combination of two or three mutations, were constructed. Mouse virulence assays of the mutated viruses clearly demonstrated that a non-conservative amino acid substitution (G710„_E) in the capsid protein VP1 alone was sufficient to confer the mouse virulence phenotype on HEV71. In addition, a mouse oral infection model was established in this study. Oral inoculation with the mouse-adapted HEV71 virus, MP-26M, induced fore-or hindlimb paralysis in newborn mice in an age- and dose-dependent manner. As oral transmission is the natural route of HEV71 infection, this murine HEV71 oral infection model will provide a suitable tool for studying HEV71 pathogenesis, for defining neurological determinants, and for testing vaccine efficacy and immunogenicity in the future.

The purpose of this study is to characterise Australian isolates of bovine enterovirus (BEV) and develop a suitable isolate as a replication-limited vaccine vector. Advantages of using BEV as a vector are that it both elicits mucosal immunity and has naturally occurring temperature stable isolates so that a BEV vector could be administered orally to elicit a protective immune response in the host and should not require cold storage to maintain vaccine efficacy. Furthermore, wildtype BEV causes no or only mild clinical symptoms in its host and if BEV is used as a vaccine vector, reversion to wildtype phenotype would not cause deleterious effects in vaccinated cattle. To date many of the viruses used as vaccine vectors are produced by modifying the structural proteins of the virion so that they contain heterologous sequences. However, each of the four BEV structural proteins are essential and it is not possible to insert large sequences without disrupting the virion. While this study looks at potential insertion sites within the BEV virion, the main focus for the development of BEV as a vaccine vector is through using a replication-limited BEV vector. The development of a replication-limited vector requires the deletion of an essential viral gene that is then replaced in vitro using an expression vector. When the replication-limited vector and its complementing expression cassette are co-transfected into a permissive cell line all the proteins required for viral assembly are produced but only replication deficient genomes are available to be encapsidated. The physically intact but replication deficient viral particles produced in vitro can then infect permissive cells in vivo, resulting in the production of all but the deleted viral protein. Moreover, the deleted portion of the viral genome can be replaced with heterologous sequences within the replication-limited BEV vector. These heterologous sequences can then be expressed in vivo where they can be recognised by the host immune system. Three BEV isolates representing the Australian subserotypes were used in this study: K2577, SL305 and 66/27. The full-length sequences of K2577 and SL305 were obtained as well as partial sequence from the third isolate, 66/27. Sequence homology and phylogenetic analysis showed all three isolates were more closely related to BEV-1 subserotypes than BEV-2. This is the first report to indicate that Australian BEV isolates can be classified as BEV-1. Analysis of the 5’-untranslated region (5’-UTR) indicated that BEV isolates were recombinants with each other and that these recombinant regions correspond to the duplicated cloverleaf structure which is present in BEV 5’-UTR but absent from other enteroviruses. While BEV was initially reported to be stable at higher temperatures, later studies showed that this property varied between isolates and this is also true of the three isolates used in this study. Since it is important not only to ensure that the isolate used as a vaccine vector is temperature stable but also the resulting vaccine vector, the molecular basis of BEV temperature stability was also studied. Using sequence data from the Australian isolates, regions of variation were located and hybrid BEV created. Unfortunately, all of the hybrid BEV produced in this study were non-infectious and could not be used to for further characterisation of BEV temperature stability. Preparatory to constructing replication-limited BEV, a system for full-length amplification of BEV was developed. By including sequences for the bacterial promoter T7 on the positive sense primer used for full-length amplification of BEV, it was possible to prepare full-length transcripts of the amplified product and these were shown to produce infectious BEV particles when transfected into to cell lines that supported BEV growth. Subsequent cloning of the K2577 amplification product resulted in infectious clones for this BEV isolate and these clones were used to prepare replication-limited BEV constructs. To test the replication-limited system BEV structural genes were replaced with a reporter gene to produce replication deficient infectious clones. Complementary constructs containing only the deleted structural genes were also prepared to express the deleted genes. While it was expected that these expression vector would be able to complement the replication deficient BEV in vivo, co-transfection of the replication-limited construct with its complementing expression vector did not produce viable BEV.