Aulinger Benedikt A, Roehrl Michael H, Mekalanos John J, Collier R John, Wang Julia Y
Channing Laboratory, Department of Medicine, Brigham and Women's Hospital, 181 Longwood Avenue, Boston, MA 02115, USA.
Infect Immun. 2005 Jun;73(6):3408-14. doi: 10.1128/IAI.73.6.3408-3414.2005.
Anthrax is caused by the unimpeded growth of Bacillus anthracis in the host and the secretion of toxins. The currently available vaccine is based on protective antigen (PA), a central component of anthrax toxin. Vaccination with PA raises no direct immune response against the bacilli and, being a natural toxin component, PA might be hazardous when used immediately following exposure to B. anthracis. Thus, we have sought to develop a vaccine or therapeutic agent that is safe and eliminates both secreted toxins and bacilli. To that end, we have previously developed a dually active vaccine by conjugating the capsular poly-gamma-d-glutamate (PGA) with PA to elicit the production of antibodies specific for both bacilli and toxins. In the present report, we describe the improved potency of anthrax vaccines through the use of a dominant-negative inhibitory (DNI) mutant to replace PA in PA or PA-PGA vaccines. When tested in mice, DNI alone is more immunogenic than PA, and DNI-PGA conjugate elicits significantly higher levels of antibodies against PA and PGA than PA-PGA conjugate. To explain the enhanced immunogenicity of DNI, we propose that the two point mutations in DNI may have improved epitopes of PA allowing better antigen presentation to helper T cells. Alternatively, these mutations may enhance the immunological processing of PA by altering endosomal trafficking of the toxin in antigen-presenting cells. Because DNI has previously been demonstrated to inhibit anthrax toxin, postexposure use of DNI-based vaccines, including conjugate vaccines, may provide improved immunogenicity and therapeutic activity simultaneously.
炭疽病是由炭疽杆菌在宿主体内不受阻碍地生长并分泌毒素引起的。目前可用的疫苗是基于保护性抗原（PA），它是炭疽毒素的核心成分。用PA进行疫苗接种不会引发针对杆菌的直接免疫反应，而且作为一种天然毒素成分，PA在接触炭疽杆菌后立即使用时可能具有危险性。因此，我们试图开发一种安全的疫苗或治疗剂，既能消除分泌的毒素，又能消除杆菌。为此，我们之前通过将荚膜聚γ-d-谷氨酸（PGA）与PA偶联，开发了一种双活性疫苗，以引发针对杆菌和毒素的特异性抗体的产生。在本报告中，我们描述了通过使用显性负性抑制（DNI）突变体来替代PA-PGA疫苗中的PA，从而提高炭疽疫苗的效力。在小鼠身上进行测试时，单独的DNI比PA更具免疫原性，并且DNI-PGA偶联物比PA-PGA偶联物引发的针对PA和PGA的抗体水平显著更高。为了解释DNI增强的免疫原性，我们提出DNI中的两个点突变可能改善了PA的表位，从而使辅助性T细胞能更好地呈递抗原。或者，这些突变可能通过改变毒素在抗原呈递细胞中的内体运输来增强PA的免疫加工过程。由于DNI此前已被证明能抑制炭疽毒素，暴露后使用基于DNI的疫苗，包括偶联疫苗，可能同时提供更好的免疫原性和治疗活性。
