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myfinalway木虫 (正式写手)
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诚心求助疫苗翻译（本人金币不足，可以后面补上或者其他帮助作为感谢）
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本人金币不够，但可以以后补上，管理员可以监督。也可以用其他帮助作为感谢。希望好心人不吝帮助，万分感激！！！！！ One limitation in the use of regular vaccines against AIV or NDV is that vaccinated poultry frequently cannot be differentiated from naturally infected birds, making serological surveillance dif- ficult to perform. However, vaccination of birds with a bivalent vaccine like rNDV_F3aa-chimericH7, which induces an immune response against H7 HA and NDV in chickens, makes serological surveillance against avian influenza possible because vaccinated animals lack immune responses against antigens present in whole influenza. Therefore, our bivalent vaccine would be suitable for use as a ‘‘differentiating infected from vaccinated animals’’ (DIVA) vaccine. NDV vaccines based on lentogenic strains of NDV are widely used in poultry. A chimeric NDV_AIV bivalent vaccine would be administered in the same way as the conventional NDV vaccines, but would confer protection against both NDV and AIV. Velogenic NDV strains are able to spread efficiently to neighboring cells upon infection of a variety of cells in the absence of exogenous proteases. This property is partially mediated by the F protein of the virus. The F protein of NDV is synthesized as an inactive precursor (F0) that needs to be cleaved into a heterodimer (F1–F2) to be functional. Cleavage of the F protein is mediated by a host protease that recognizes a cleavage site between the F1 and F2 subunits. When the F1–F2 heterodimer is expressed on the surface of infected cells, it induces fusion between the infected cell and the neighboring cells, resulting in the formation of syncytia. Because the induction of syncytia helps the spread of the virus from cell to cell, the use of a vaccine with a velogenic NDV-derived F cleavage site in poultry may raise potential safety concerns. However, when we introduced a multibasic cleavage site in the F protein of the highly attenuated rNDV_B1, the resulting viruses did not acquire the characteristics typical of velogenic strains with MDTs of _60 hr in chicken embryos. We postulated that enhanced incorporation of the H7 HA protein into rNDV virions may afford a better humoral immune response, resulting in higher levels of protection in chickens against highly pathogenic AIV. However, it was previously observed that virion incorporation of an influenza virus WSN HA protein expressed from rNDV was lower than the homologous HA protein expressed from influenza virus (21). If the H7 HA protein contained the cytoplasmic tail and transmembrane domains of the NDV envelope glycoprotein (F), which are required for efficient viral assembly, in place of its own, this resulted in enhanced incorporation of HA into the viral particle and in improved immunogenicity of the virus. Indeed, the use of an improved NDV vector that had enhanced cell-to-cell transmission and allowed for efficient incorporation of the avian HA into virus particles resulted in 90% protection against challenge with type A HPAI strains and complete protection against velogenic NDV. In summary, the use of reverse genetics systems for the construction of chimeric influenza or NDV viruses provides a practical strategy for the protection of poultry against existing and newly emerging viruses of HPAI, as well as against NDV. It is expected that these approaches will also prove useful in the development of bivalent vaccines for other pathogens. |
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zap65535
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2楼2010-01-09 11:39:33
myfinalway
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3楼2010-01-09 14:09:36
myfinalway
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4楼2010-01-11 12:01:52
