Morikawa Shigeru, Sakiyama Tokuki, Hasegawa Hideki, Saijo Masayuki, Maeda Akihiko, Kurane Ichiro, Maeno Go, Kimura Junko, Hirama Chie, Yoshida Teruhiko, Asahi-Ozaki Yasuko, Sata Tetsutaro, Kurata Takeshi, Kojima Asato
Department of Virology, National Institute of Infectious Diseases, Toyama, Tokyo, Japan.
J Virol. 2005 Sep;79(18):11873-91. doi: 10.1128/JVI.79.18.11873-11891.2005.
The potential threat of smallpox bioterrorism has made urgent the development of lower-virulence vaccinia virus vaccines. An attenuated LC16m8 (m8) vaccine was developed in 1975 from the Lister strain used in the World Health Organization smallpox eradication program but was not used against endemic smallpox. Today, no vaccines can be tested with variola virus for efficacy in humans, and the mechanisms of immune protection against the major intracellular mature virion (IMV) and minor extracellular enveloped virion (EEV) populations of poxviruses are poorly understood. Here, we determined the full-genome sequences of the m8, parental LC16mO (mO), and grandparental Lister (LO) strains and analyzed their evolutionary relationships. Sequence data and PCR analysis indicated that m8 was a progeny of LO and that m8 preserved almost all of the open reading frames of vaccinia virus except for the disrupted EEV envelope gene B5R. In accordance with this genomic background, m8 induced 100% protection against a highly pathogenic vaccinia WR virus in mice by a single vaccination, despite the lack of anti-B5R and anti-EEV antibodies. The immunogenicity and priming efficacy with the m8 vaccine consisting mainly of IMV were as high as those with the intact-EEV parental mO and grandparental LO vaccines. Thus, mice vaccinated with 10(7) PFU of m8 produced low levels of anti-B5R antibodies after WR challenge, probably because of quick clearance of B5R-expressing WR EEV by strong immunity induced by the vaccination. These results suggest that priming with m8 IMV provides efficient protection despite undetectable levels of immunity against EEV.
天花生物恐怖主义的潜在威胁使得开发低毒力痘苗病毒疫苗变得紧迫。1975年，从世界卫生组织天花根除计划中使用的李斯特菌株开发出了减毒的LC16m8（m8）疫苗，但未用于应对地方性天花。如今，无法用人痘病毒测试疫苗的疗效，而且针对痘病毒主要细胞内成熟病毒粒子（IMV）和次要细胞外被膜病毒粒子（EEV）群体的免疫保护机制仍知之甚少。在此，我们测定了m8、亲本LC16mO（mO）和祖代李斯特（LO）菌株的全基因组序列，并分析了它们的进化关系。序列数据和PCR分析表明，m8是LO的后代，并且m8保留了痘苗病毒几乎所有的开放阅读框，除了被破坏的EEV包膜基因B5R。根据这一基因组背景，尽管缺乏抗B5R和抗EEV抗体，但m8通过单次接种可在小鼠中诱导对高致病性痘苗WR病毒的100%保护。主要由IMV组成的m8疫苗的免疫原性和启动效力与完整EEV的亲本mO和祖代LO疫苗一样高。因此，用10^7 PFU的m8接种的小鼠在受到WR攻击后产生的抗B5R抗体水平较低，这可能是因为接种诱导的强大免疫力迅速清除了表达B5R的WR EEV。这些结果表明，尽管对EEV的免疫水平无法检测到，但用m8 IMV进行启动仍可提供有效的保护。
