RESUMO
The literature on sero-epidemiological studies of flaviviral infections in the African continent is quite scarce. Much of the viral epidemiology studies have been focussing on diseases such as HIV/AIDS because of their sheer magnitude and impact on the lives of people in the various affected countries. Increasingly disease outbreaks caused by arboviruses such as the recent cases of chikungunya virus, dengue virus and yellow fever virus have prompted renewed interest in studying these viruses. International agencies from the US, several EU nations and China are starting to build collaborations to build capacity in many African countries together with established institutions to conduct these studies. The Tofo Advanced Study Week (TASW) was established to bring the best scientists from the world to the tiny seaside town of Praia do Tofo to rub shoulders with African virologists and discuss cutting-edge science and listen to the work of researchers in the field. In 2015 the 1st TASW focussed on Ebola virus. The collections of abstracts from participants at the 2nd TASW which focused on Dengue and Zika virus as well as presentations on other arboviruses are collated in this chapter.
Assuntos
Infecções por Arbovirus/epidemiologia , Arbovírus/isolamento & purificação , África/epidemiologia , Animais , Anticorpos Antivirais/sangue , Infecções por Arbovirus/sangue , Infecções por Arbovirus/virologia , Arbovírus/genética , Arbovírus/imunologia , Humanos , Estudos SoroepidemiológicosRESUMO
Two biotypes of pestiviruses, cytopathogenic (cp) and noncp viruses, can be distinguished by their effects on tissue culture cells. Identification of cp bovine viral diarrhea virus (BVDV) has been frequently reported since antigenically closely related noncp and cp BVDV can be isolated from cattle with fatal mucosal disease (MD) and are called a virus pair. In contrast to the BVDV system, only few cp border disease virus (BDV) and cp classical swine fever virus (CSFV) strains have been described. Serological analyses and sequence comparison studies showed that cp pestiviruses arise from noncp viruses by mutation. Elaborate studies during the last 10 years revealed that in most cases RNA recombination is responsible for the generation of the cp viruses. Recent results showed a second way for the development of a cp pestivirus which is based on the introduction of a set of point mutations within the NS2 gene.
Assuntos
Efeito Citopatogênico Viral , Pestivirus/genética , Pestivirus/patogenicidade , Animais , Doença das Mucosas por Vírus da Diarreia Viral Bovina/genética , Doença das Mucosas por Vírus da Diarreia Viral Bovina/virologia , Bovinos , Peste Suína Clássica/genética , Peste Suína Clássica/virologia , Vírus da Febre Suína Clássica/genética , Vírus da Febre Suína Clássica/patogenicidade , Vírus da Diarreia Viral Bovina/genética , Vírus da Diarreia Viral Bovina/patogenicidade , Genoma Viral , Suínos , Proteínas Estruturais Virais/genéticaRESUMO
Cytopathogenicity of Bovine viral diarrhea virus (BVDV) is correlated with expression of the nonstructural protein NS3, which can be generated by processing of a fusion protein termed NS2-3. For the cytopathogenic (cp) BVDV strain Oregon, NS2-3 processing is based on a set of point mutations within NS2. To analyze the correlation between NS2-3 cleavage and cytopathogenicity, a full-length cDNA clone composed of cDNA from BVDV Oregon and the utmost 5'- and 3'-terminal sequences of a published infectious BVDV clone was established. After transfection of RNA transcribed from this cDNA clone, infectious virus with similar growth characteristics to wild-type BVDV Oregon could be recovered that also exhibited a cytopathic effect. Based on this cDNA construct and published cp and noncp infectious clones, chimeric full-length cDNA clones were constructed. Analysis of the recovered viruses demonstrated that the presence of the NS2 gene of BVDV Oregon in a chimeric construct is sufficient for NS2-3 processing and a cp phenotype. Since previous studies had revealed that the amino acid serine at position 1555 of BVDV Oregon plays an important role in efficient NS2-3 cleavage, mutants of BVDV Oregon with different amino acids at this position were constructed. Some of these mutants showed NS2-3 cleavage efficiencies in the range of the wild-type sequence and allowed the recovery of viruses that behaved similarly to wild-type virus with regard to growth characteristics and cytopathogenicity. In contrast, other mutants with considerably reduced NS2-3 cleavage efficiencies propagated much more slowly and reverted to viruses expressing polyproteins with sequences allowing efficient NS2-3 cleavage. These viruses apparently induced cytopathic effects only after reversion.
Assuntos
Efeito Citopatogênico Viral/genética , Vírus da Diarreia Viral Bovina/genética , Mutação Puntual , Proteínas não Estruturais Virais/genética , Animais , Sequência de Bases , Bovinos , Linhagem Celular , Clonagem Molecular , Primers do DNA , DNA Complementar , Vírus da Diarreia Viral Bovina/patogenicidade , Mutagênese Sítio-DirigidaRESUMO
Bovine viral diarrhea virus (BVDV) isolates can either be cytopathogenic (cp) or noncytopathogenic (noncp). While both biotypes express the nonstructural protein NS2-3, generation of NS3 strictly correlates with the cp phenotype. The production of NS3 is usually caused by cp specific genome alterations, which were found to be due to RNA recombination. Molecular analyses of the cp BVDV strain Oregon revealed that it does not possess such genome alterations but nevertheless is able to generate NS3 via processing of NS2-3. The NS3 serine protease is not involved in this cleavage, which, according to protein sequencing, occurs between amino acids 1589 and 1590 of the BVDV Oregon polyprotein. Transient-expression studies indicated that important information for the cleavage of NS2-3 is located within NS2. This was verified by expression of chimeric constructs containing cDNA fragments derived from BVDV Oregon and a noncp BVDV. It could be shown that the C-terminal part of NS2 plays a crucial role in NS2-3 cleavage. These data, together with results obtained by site-specific exchanges in this region, revealed a new mechanism for NS2-3 processing which is based on point mutations within NS2.
Assuntos
Vírus da Diarreia Viral Bovina/metabolismo , Peptídeo Hidrolases , Processamento de Proteína Pós-Traducional , RNA Helicases , Proteínas não Estruturais Virais/metabolismo , Sequência de Aminoácidos , Animais , Sequência de Bases , Bovinos , Linhagem Celular , Quimotripsina/genética , Quimotripsina/metabolismo , Cricetinae , DNA Viral , Vírus da Diarreia Viral Bovina/genética , Expressão Gênica , Genoma Viral , Dados de Sequência Molecular , Mutação Puntual , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Proteínas não Estruturais Virais/genéticaRESUMO
After cDNA cloning of the genome of bovine viral diarrhea virus (BVDV) isolate CP7, a full-length cDNA clone was constructed. RNA transcribed in vitro from this construct was shown to direct the generation of infectious BVDV upon transfection into bovine cells. To confirm the de novo generation of infectious BVDV from cloned cDNA a genetically tagged virus was constructed. In comparison with parental BVDV, the recombinant virus was slightly retarded in growth. The NS2 coding region of the CP7 genome contains a duplication of 27 nucleotides which is not present in the genome of its noncytopathogenic counterpart, NCP7. Exchange of a small fragment harboring this insertion against the corresponding part of the NCP7 sequence led to recovery of noncytopathogenic BVDV. Alteration of the construct by introduction of a fragment derived from a cytopathogenic BVDV defective interfering particle resulted in a chimeric defective interfering particle which exhibits a cytopathogenic phenotype. These findings confirm the hypothesis that the recombination-induced alterations in the genomes of cytopathogenic BVDV are responsible for the induction of cell lysis.
