Wyatt Linda S, Earl Patricia L, Eller Leigh Anne, Moss Bernard
Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892-0445, USA.
Proc Natl Acad Sci U S A. 2004 Mar 30;101(13):4590-5. doi: 10.1073/pnas.0401165101. Epub 2004 Mar 11.
Modified vaccinia virus Ankara (MVA), developed >30 years ago as a highly attenuated candidate smallpox vaccine, was recloned from a 1974 passage and evaluated for safety and immunogenicity. Replication of MVA is impaired in most mammalian cells, and we found that mice with severe combined immunodeficiency disease remained healthy when inoculated with MVA at 1,000 times the lethal dose of vaccinia virus derived from the licensed Dryvax vaccine seed. In BALB/c mice inoculated intramuscularly with MVA, virus-specific CD8+ T cells and antibodies to purified virions and membrane protein components of the intracellular and extracellular infectious forms of vaccinia virus were induced in a dose-dependent manner. After one or two inoculations of MVA, the T cell numbers and antibody titers equaled or exceeded those induced by percutaneous injection of Dryvax. Antibodies induced by MVA and Dryvax were neutralizing and inhibited virus spread in cultured cells. Furthermore, vaccinated mice were protected against lethal intranasal challenge with a pathogenic vaccinia virus. B cell-deficient mice unable to generate antibodies and beta2-microglobulin-deficient mice unable to express MHC class I molecules for a CD8+ T cell response were also protectively vaccinated by MVA. In contrast, mice with decreased CD4 or MHC class II expression and double-knockout mice deficient in MHC class I- and II-restricted activities were poorly protected or unprotected. This study confirmed the safety of MVA and demonstrated that the overlapping immune responses protected normal and partially immune-deficient animals, an encouraging result for this candidate attenuated smallpox vaccine.
安卡拉痘苗病毒（MVA）于30多年前被开发为一种高度减毒的天花疫苗候选株，它是从1974年传代毒株中重新克隆出来的，并对其安全性和免疫原性进行了评估。MVA在大多数哺乳动物细胞中的复制能力受损，我们发现，接种剂量为源自已获许可的Dryvax疫苗种子的痘苗病毒致死剂量1000倍的MVA时，患有严重联合免疫缺陷病的小鼠仍保持健康。在肌肉注射MVA的BALB/c小鼠中，病毒特异性CD8⁺ T细胞以及针对痘苗病毒细胞内和细胞外感染形式的纯化病毒粒子和膜蛋白成分的抗体呈剂量依赖性诱导产生。接种一到两次MVA后，T细胞数量和抗体滴度等于或超过经皮注射Dryvax所诱导的水平。MVA和Dryvax诱导产生的抗体具有中和作用，并能抑制病毒在培养细胞中的传播。此外，接种疫苗的小鼠能够抵御致病性痘苗病毒的致死性鼻内攻击。无法产生抗体的B细胞缺陷小鼠以及无法表达用于CD8⁺ T细胞应答的MHC I类分子的β2-微球蛋白缺陷小鼠也通过MVA获得了保护性接种。相比之下，CD4表达降低或MHC II类表达降低的小鼠以及缺乏MHC I类和II类限制活性的双敲除小鼠受到的保护较差或未得到保护。本研究证实了MVA的安全性，并表明重叠的免疫反应可保护正常和部分免疫缺陷动物，这对于这种减毒天花疫苗候选株来说是一个令人鼓舞的结果。
