Department of HIV/AIDS Research, State Key Laboratory of Pathogen and Biosecurity, Institute of Microbiology and Epidemiology, Academy of Military Medical Sciences, Beijing 100071, China.
Chin Med J (Engl). 2009 Oct 5;122(19):2339-45.
The adenovirus-based HIV-1 vaccine developed by Merck Company suffered from an unexpected failure in September 2007. This generated a big shift in the strategy of HIV vaccine development with renewed focus on the induction of neutralizing antibodies. A major challenge in developing an HIV-1 vaccine is to identify immunogens and adopt delivery methods that can elicit broadly neutralizing antibodies against primary isolates of different genetic subtypes.
Most circulating HIV-1 isolates in China are composed of clades Thai-B, CRF_BC and CRF01_AE. In order to construct DNA vaccines against these 3 HIV-1 subtypes, DNA vaccines carrying the gp120 regions from HIV-1 isolates of GX48(AE), GX79(AE), NX22(BC), GS22(BC), HN24(Thai-B) were constructed. Expression of gp120 from these DNA vaccines was detected by Western blotting in transiently transfected 293T cells. Pilot immunizations of New Zealand white rabbits were performed using the strategy of "DNA prime plus protein boost" and the neutralizing antibody response was detected in a Tzm-bl cell based assay against different HIV-1 strains.
Response of gp120-specific antibody was relatively low after DNA primes (mean titer = 10(4.72)); however, the titer of gp120-specific antibody went up with 2 protein boosts (mean titer = 10(6.81)). Above all, neutralizing antibody (Nab) titers induced by this combined approach were much better than those elicited by DNA or protein used alone (P < 0.01). Neutralizing activities of immunized rabbit sera against several pseudoviruses and laboratorial strains were evaluated, most rabbit sera primed with monovalent vaccine were capable of neutralizing only 1 of 5 viruses, however, sera primed with the polyvalent DNA vaccines were able to neutralize at least 2 of 5 viruses.
Polyvalent DNA prime plus protein boost is an effective immunization strategy to broaden the neutralization breadth and further research should be performed on the basis of this pilot study.
默克公司研发的基于腺病毒的 HIV-1 疫苗在 2007 年 9 月出人意料地失败了。这使得 HIV 疫苗研发策略发生了重大转变，重新聚焦于诱导中和抗体。开发 HIV-1 疫苗的一个主要挑战是确定免疫原并采用能够诱导针对不同遗传亚型原发性分离株的广泛中和抗体的递送方法。
中国流行的大多数 HIV-1 分离株由泰式-B、CRF_BC 和 CRF01_AE 组构成。为了针对这 3 种 HIV-1 亚型构建 DNA 疫苗，构建了携带 HIV-1 分离株 GX48(AE)、GX79(AE)、NX22(BC)、GS22(BC)和 HN24(泰式-B)gp120 区的 DNA 疫苗。通过瞬时转染 293T 细胞中的 Western blot 检测这些 DNA 疫苗中 gp120 的表达。采用“DNA 初免加蛋白加强”策略对新西兰白兔进行初步免疫接种，并在 Tzm-bl 细胞基础测定中检测针对不同 HIV-1 株的中和抗体反应。
DNA 初免后 gp120 特异性抗体的反应相对较低（平均滴度=10(4.72)）；然而，随着 2 次蛋白加强，gp120 特异性抗体的滴度上升（平均滴度=10(6.81)）。最重要的是，这种联合方法诱导的中和抗体（Nab）滴度明显优于 DNA 或蛋白单独使用（P < 0.01）。评估了免疫兔血清对几种假病毒和实验室株的中和活性，大多数用单价疫苗初免的兔血清仅能中和 5 种病毒中的 1 种，然而，用多价 DNA 疫苗初免的血清至少能中和 5 种病毒中的 2 种。
多价 DNA 初免加蛋白加强是一种有效的免疫策略，可以拓宽中和广度，应在此初步研究的基础上进一步研究。
