Bacterial Commensal Vector Delivery/Smallpox Vaccine

描述（由申请人提供）：天花被广泛认为是生物战中最严重的威胁。有一种有效的疫苗（牛痘病毒），但由于牛痘病毒相关的严重并发症（包括死亡）的风险虽小但却很大，因此目前不建议进行大规模免疫接种。这使得民众处于故意或意外将致病性痘病毒引入我们环境的风险之中。这项建议的重点是开发一种安全性更高的替代疫苗，用于预防由天花病毒等致病性正痘病毒引起的人类疾病。为了实现这一目标，我们将利用我们新开发的BCV（细菌共生载体）技术。BCV利用革兰氏阳性共生细菌，如戈登链球菌，在其外表面表达感兴趣的异源抗原。I期人体临床试验表明，这种戈多氏链球菌在人体中是安全且耐受性良好的。用表达牛痘病毒A27L蛋白或DSL的戈尔多氏球菌对小鼠粘膜免疫，可引起对致命牛痘攻击的保护。我们相信，通过这种活的细菌载体系统递送选定的牛痘病毒抗原将为预防人类天花提供一种有效和安全的方法。本文提出以下具体目标：1)构建表达保守痘苗抗原的重组gordonii菌株，并将其固定在细菌表面；2)检测gordonir的免疫原性。W重组体局部注入小鼠体内，在小鼠模型中测量抗体反应（IgG和IgA）、抗原特异性CTL反应、病毒中和和/或杀伤，以及对活病毒攻击的保护作用。实验的成功完成将确定一种适合后续临床前验证和开发的BCV天花候选疫苗。

DESCRIPTION (provided by applicant): Smallpox is widely considered to be the most serious threat for use as a potential agent of biowarfare. There is an effective vaccine available (vaccinia virus), but because of a small but significant risk of serious complications (including death) associated with vaccinia virus, mass immunization is not currently advisable. This leaves the populace at risk to the deliberate or accidental introduction of a pathogenic poxvirus into our environment. The focus of this proposal is to develop an alternative vaccine with improved safety for use in preventing human disease caused by pathogenic orthopoxviruses such as variola virus. To accomplish this goal we will utilize our newly-developed BCV (bacterial commensal vector) technology. BCV utilizes gram-positive commensal bacteria, such as Streptococcus gordonii, to express heterologous antigens of interest on its external surface. Phase I human clinical trials indicate that this S. gordonii strain is safe and well-tolerated in humans. Mucosal immunization of mice with S. gordonii expressing either the vaccinia virus A27L protein or DSL elicited protection against lethal vaccinia challenge. We believe that the delivery of selected vaccinia virus antigens via this live bacterial vector system will provide an effective and safe method for prevention of smallpox in humans. The following specific aims are proposed 1) To construct recombinant S. gordonii strains that express conserved vaccinia antigens anchored to the bacterial surface, and 2) To test the immunogenicity of S. gordonir.W recombinants when delivered topically into mice, measuring antibody response (IgG and IgA), antigen-specific CTL responses, viral neutralization and/or killing, and protection against a live viral challenge in a murine model. Successful completion of the proposed  experiments will identify a BCV smallpox vaccine candidate suitable for subsequent preclinical validation and development.