New Approaches To Passive And Active Immunoprophylaxis

HVS与比利时Rixensart的葛兰素史克公司合作，开发了几种候选的甲型肝炎减毒活疫苗。此外，人类免疫研究所还开发了一种前景看好的候选重组戊型肝炎疫苗，目前正在进行临床试验。为了进一步确定这种候选戊型肝炎疫苗的特性，我们进行了广泛的临床前试验，以确定疫苗的效力、保护期、最佳给药方案、对同源和异种病毒株的保护效力、预防感染和肝炎的能力以及有效预防感染和肝炎的最低抗体滴度。HVS正在研究DNA疫苗的技术，并建立了一个基于乙肝疫苗的模型系统，HVS在乙肝疫苗方面已经有了丰富的经验。我们测试了一种免疫刺激剂(CpG)作为DNA疫苗和蛋白质疫苗佐剂的有效性。此外，还探讨了DNA疫苗在丙型肝炎病毒控制中的应用。一种基于丙型肝炎病毒E2包膜蛋白的DNA疫苗在小鼠和猕猴中被证明具有高度的免疫原性，在黑猩猩中具有中等的免疫原性，但当黑猩猩受到活的丙型肝炎病毒攻击时，它们并没有得到完全保护。类似的方法也被用于基于丙型肝炎病毒包膜蛋白的DNA疫苗的研究：将不同结构的E1基因制备成DNA疫苗(表达载体质粒)和载体疫苗(重组痘苗)，并在小鼠身上进行测试。这些小鼠对DNA疫苗和牛痘疫苗都有很好的免疫反应。在其他研究中，重组的丙型肝炎病毒包膜糖蛋白正在黑猩猩身上作为免疫预防和免疫治疗疫苗进行测试。被动免疫预防也是一种重要的公共卫生工具。例如，正常的免疫球蛋白在预防甲型肝炎方面一直很重要。然而，单抗制剂可能更有效，为特定的中和表位量身定做，效力高度一致。我们从实验中先后感染了五种人类肝炎病毒的黑猩猩的骨髓中制备了组合文库。黑猩猩的球蛋白与人类的免疫球蛋白几乎完全相同，这使它们成为免疫预防和免疫治疗药物的诱人选择。到目前为止，我们已经分离出与甲型肝炎病毒、乙肝病毒、丁型肝炎病毒和戊型肝炎病毒发生反应的单抗免疫球蛋白。在其他研究中，我们已经恢复了与丙型肝炎病毒反应的人类单抗。上面描述的许多单抗是中和的，它们的生产正在扩大规模，用于对黑猩猩进行被动免疫预防测试。对实验感染登革热病毒1至4和诺沃克病毒的黑猩猩，正在进行类似的骨髓组合文库构建。我们现在已经将这些研究扩展到其他感兴趣的病毒和细菌，这些病毒和细菌可以在黑猩猩身上进行实验。例如，为了应对对生物恐怖主义的新关切，我们正在准备中和牛痘病毒的单抗，作为免疫预防/免疫治疗剂，用于那些需要牛痘免疫但容易受到这种免疫副作用影响的人。同样，我们正在用炭疽毒素的三种成分免疫黑猩猩，试图制造出能够立即在体内中和炭疽的单抗。我们还在制备针对三种血清型脊髓灰质炎病毒、狂犬病病毒、日本脑炎病毒、西尼罗河病毒和森林脑炎病毒复合体的黑猩猩单抗。最近，我们加入了肉毒杆菌和SARS病毒的七种毒素，其中一些在对抗生物恐怖主义方面有潜在的效用，在对抗新出现和重新出现的病原体方面都具有免疫预防和免疫治疗的潜力。

The HVS in collaboration with GlaxoSmithKline, Rixensart, Belgium, has developed several candidate live attenuated HAV vaccines. In addition, the HVS has developed a candidate recombinant hepatitis E vaccine that is highly promising and that is currently in clinical trials. In studies to further characterize this candidate hepatitis E vaccine, we have performed extensive pre-clinical trials to determine the potency of the vaccine, the duration of protection, the optimum regimen for administration, its protective efficacy against homologous versus heterologous virus strains, its ability to prevent infection as well as hepatitis and the minimum antibody titer that was effective in preventing infection and hepatitis, respectively. The HVS is studying the technology of DNA vaccines with a model system based upon hepatitis B virus (HBV) vaccine, a vaccine with which the HVS has had extensive experience. We have tested the efficacy of an immunostimulant (CpG) as an adjuvant for DNA vaccines, as well as for protein vaccines. In addition, the utility of DNA vaccines for the control of hepatitis C virus (HCV) has been explored. A DNA vaccine based on the E2 envelope protein of HCV proved to be highly immunogenic in mice and rhesus monkeys and moderately immunogenic in chimpanzees, but the chimpanzees were not fully protected when they were challenged with live HCV. A similar approach has been utilized in the study of a DNA vaccine based on the E1 envelope protein of HCV: various constructs of the E1 gene were prepared as DNA vaccines (expression vector plasmids) and as vectored vaccines (recombinant vaccinia) and tested in mice. The mice had excellent immune responses to the DNA vaccine as well as to the vaccinia boost. In other studies, recombinant HCV E1 envelope glycoprotein is being tested in chimpanzees as an immunoprophylactic and immunotherapeutic vaccine. Passive immunoprophylaxis has also been an important public health tool. For example, normal immunoglobulin has been important in the prevention of hepatitis A. However, monoclonal preparations could be more potent, tailored to specific neutralization epitopes and highly consistent in potency. We have prepared combinatorial libraries from the bone marrow of chimpanzees that had been experimentally infected in sequence with each of the five human hepatitis viruses. Chimpanzee globulins are virtually identical to human immunoglobulins, making them attractive choices for immunoprophylactic and immunotherapeutic agents. To date, we have isolated monoclonal immunoglobulins that react with HAV, HBV, HDV and HEV. In other studies, we have recovered human monoclonal antibodies that react with HCV. Many of the monoclonal antibodies described above are neutralizing and their production is being scaled up for tests of passive immunoprophylaxis in chimpanzees. Similar construction of combinatorial libraries from bone marrow is being carried out for chimpanzees that have been experimentally infected with dengue viruses 1 through 4 and the Norwalk virus. We have now extended these studies to other viruses and bacteria of interest that can be experimentally administered to chimpanzees. For example, in response to new concerns about bioterrorism, we are preparing neutralizing monoclonal antibodies to vaccinia virus for use as an immunoprophylactic/immunotherapeutic agent in those who require immunization with vaccinia but who are susceptible to the side-effects of such immunization. Similarly, we are immunizing chimpanzees with the three components of anthrax toxin, in an attempt to make monoclonal antibodies that could immediately neutralize anthrax in vivo. We are also preparing chimpanzee monoclonal antibodies to the three serotypes of poliovirus, to rabies virus, Japanese encephalitis virus, to West Nile virus and to the tick-borne encephalitis virus complex. Most recently we have added the seven toxins of Clostridium botulinum and the SARS virus.Some of these will have potential utility in efforts to counteract bioterrorism and all will have immunoprophylactic and immunotherapeutic potential in the battle against emerging and re-emerging pathogens.