DNA疫苗的分子佐剂应用研究进展

DNA疫苗因在动物尤其是大型动物与人类中诱发较低的免疫反应而严重影响其推广应用。介绍提高与调节DNA疫苗诱导反应的策略：（1）以细胞因子表达质控为佐剂;（2）以质粒编码的趋化因子与共刺激分子为佐剂;（3）以CPG ODN为佐剂。     

多种HIVB′/C亚型基因在复制型DNA疫苗中表达及免疫效果研究

为了解多种HIVB′/C亚型基因在复制型DNA疫苗中表达水平及对免疫效果影响,使用复制型DNA疫苗载体pSCK2,分别构建了7种含单种或多种HIVB′/C亚型基因gagpol、gp160和rtn(rev、tat和nef融合基因)的DNA疫苗质粒。免疫荧光检测表明,Gag、Gp160、Rev、Tat和Nef蛋白均能从相应7种DNA疫苗中表达,单基因表达质粒中的基因表达水平和双基因表达质粒中IRES上游的基因表达水平普遍较好。小鼠免疫后,Gag能诱发较高的抗体滴度,Gp160、Pol和RTN的抗体滴度很低;比较研究显示,Gag单独表达和Gag与RTN双表达的质粒均能诱发较好的Gag抗体反应,但Gag与Gp160双表达质粒免疫或含Gag、Gp160和RTN质粒联合免疫的Gag抗体反应均较弱。ELISPOT检测表明,7种DNA疫苗单独或不同组合方式免疫均能诱发针对Gag、Pol、Gp160、Tat和Nef的细胞免疫反应;单基因表达质粒单独免疫诱发的细胞免疫反应最好,含gagpol和gp160双基因表达质粒单独免疫或与含其它基因质粒联合免疫诱发的Gag、Pol和Gp160细胞免疫明显低于含Gagpol或Gp160单基因质粒诱发的相应免疫反应,但诱发的Tat和Nef细胞免疫与相应单基因质粒免疫组无明显差别。本研究结果显示,不同表达构建体的多种HIVB'/C亚型的基因gagpol、gp160和rtn均能从pSCK2质粒中较好地表达;不同基因结构和不同组合免疫的优化,特别是含gag和gp160基因疫苗联合免疫程序的进一步优化对提高其免疫效果是必要的。     

减毒沙门氏菌为载体在Vero细胞中表达传染性法氏囊病病毒多聚蛋白基因

用长距离RT-PCR扩增了传染性法氏囊病病毒（infectious bursal disease virus, IBDV）ZJ2000株多聚蛋白基因,定向克隆入真核表达载体Pci,电转化dam^-和phoP^－双突变的减毒鼠伤寒沙门氏菌ZJ111株,并直接转染Vero细胞。RT-PCR和间接免疫荧光试验可从Vero细胞中检测到阳性信号,SDS-PAGE和West blotting均可检测到41kD的蛋白条带。结果表明减毒沙门氏菌可将外源基因导入Vero细胞,并进行转录和表达,具有免疫反应性,为进一步研制减毒沙门氏菌为载体的IBDV口服DNA疫苗打下基础。     

流感病毒疫苗佐剂研究现状

流行性感冒是一类由流感病毒引起的急性呼吸道传染病。其发病率高、传染性强,因此作为最佳预防手段的流感疫苗关注度日益提升。而佐剂的使用可提升流感疫苗的效果并减少相应抗原的使用量,因此成为研究热点。就应用于流感疫苗中佐剂的研究现状做一综述。     

DNA疫苗免疫佐剂的研究进展

DNA疫苗是最近几年从基因治疗研究领域发展起来的一种新型疫苗,它能诱导机体产生持久的体液免疫和细胞免疫应答,能够抗病毒,细菌和寄生虫的感染,对自身免疫性疾病和过敏性疾病有一定的疗效作用。但与传统的灭活疫苗相比,其免疫效价还比较低,最近的研究表明：联合使用DNA疫苗和疫苗佐剂如细胞因子,协同刺激分子等有助于提高DNA疫苗的免疫效价,这一发现有利于研制更有效的DNA疫苗,本文就通过使用免疫佐剂提高DNA免疫效价的最新进展做一综述。     

细胞因子作为DNA疫苗佐剂的研究进展

细胞因子是机体细胞(主要指免疫细胞)产生的一类具有广泛生物学活性的异质性肽类调节因子,在体内能激活免疫活性细胞,对免疫应答的产生和调节有重要作用。近年来,大量研究表明细胞因子可作为DNA疫苗佐剂来增强疫苗的免疫效果。简要综述了细胞因子作为DNA疫苗免疫佐剂的研究进展。     

性疟原虫DNA疫苗免疫效果的评估

以霍乱毒素Ｂ亚基（ＣＴＢ）为载体,由其基因构建了含有不同时期不同抗原表位的恶性疟原虫的融合基因ＣＴＢ～ＡＷＴＥ、ＣＴＢ～ＮＡＮＰ,前者除含有恶性疟原虫裂殖子表面主要抗原表位杂合多肽基因ＳＰｆ６６外,还含有很强的Ｔ辅助细胞表位ＣＳＴ３和Ｔｃ细胞表位,后者含有子孢子期的Ｂ、Ｔｈ细胞表位。将纯化的质粒免疫Ｂａｌｂ／ｃ纯系小鼠,３次免疫后诱导机体产生了体液免疫和细胞免疫,免疫的小鼠进行疟原虫子孢子攻击实验,保护率为６０％一８０％。将纯化的质粒混合后免疫恒河猴,３次免疫后诱导机体产生了体液免疫和细胞免疫,免疫的恒河猴进行食蟹疟原虫攻击实验,显示了一定的保护作用。     

Prion疾病疫苗研究策略

朊病毒病是一类侵袭人类及多种动物中枢神经系统的致死性退行性脑病,目前缺乏有效的预防和治疗方法。朊病毒病的重组蛋白亚单位疫苗、DNA疫苗、合成肽疫苗、病毒样颗粒疫苗、树突状细胞疫苗、黏膜免疫疫苗等已取得一定进展,但现有的免疫策略仅能部分克服免疫耐受,诱导较低或中等滴度的抗体,对PrPSc感染动物模型只能提供部分保护,Prion疫苗研究任重而道远。     

Intranasal and oral vaccination with protein-based antigens: advantages,challenges and formulation strategies

pathogens initiate their infections at the human mucosal surface. Therefore, mucosal vaccination, especially through oral or intranasal administration routes, is highly desired for infectious diseases. Meanwhile, protein-based antigens provide a safer alternative to the whole pathogen or DNA based ones in vaccine development. However, the unique biopharmaceutical hurdles that intranasally or orally delivered protein vaccines need to overcome before they reach the sites of targeting, the relatively low immunogenicity, as well as the low stability of the protein antigens, require thoughtful and fine-tuned mucosal vaccine formulations, including the selection of immunostimulants, the identification of the suitable vaccine delivery system, and the determination of the exact composition and manufacturing conditions. This review aims to provide an up-to-date survey of the protein antigen-based vaccine formulation development, including the usage of immunostimulants and the optimization of vaccine delivery systems for intranasal and oral administrations.     

Fish DNA vaccine against infectious hematopoietic necrosis virus: efficacy of various routes of immunisation

The DNA vaccine, pIHNVw-G, contains the gene for the glycoprotein (G) of the rhabdovirus infectious hematopoietic necrosis virus (IHNV), a major pathogen of salmon and trout. The relative efficacy of various routes of immunisation with pIHNVw-G was evaluated using 1.8 g rainbow trout fry vaccinated via intramuscular injection, scarification of the skin, intraperitoneal injection, intrabuccal administration, cutaneous particle bombardment using a gene gun, or immersion in water containing DNA vaccine-coated beads. Twenty-seven days after vaccination neutralising antibody titres were determined, and 2 days later groups of vaccinated and control unvaccinated fish were subjected to an IHNV immersion challenge. Results of the virus challenge showed that the intramuscular injection and the gene gun immunisation induced protective immunity in fry, while intraperitoneal injection provided partial protection. Neutralising antibodies were not detected in sera of vaccinated fish regardless of the route of immunisation used, suggesting that cell mediated immunity may be at least partially responsible for the observed protection.     

猪瘟疫苗研究进展

猪瘟是猪的一种重要传染病,给世界养猪业造成了巨大的经济损失。疫苗免疫是预防该病的主要手段。本文综述了猪瘟流行现状、传统疫苗、亚单位疫苗、活载体疫苗、标记疫苗、核酸疫苗的研究进展,并对它们的发展趋势作了初步探讨和展望。     

Augmentation of antigen-specific immune responses using DNA-fusogenic liposome vaccine

In an attempt to enhance the immunological efficacy of genetic immunization, we investigated a new biological means for delivering antigen gene directly to the cytoplasm via membrane fusion. In this context, we investigated fusogenic liposome (FL) encapsulating DNA as a possible genetic immunization vehicle. RT-PCR analysis indicated that a FL could introduce and express encapsulating OVA gene efficiently and rapidly in vitro. Consistent with this observation, an in vitro assay showed that FL-mediated antigen-gene delivery can induce potent presentation of antigen via the MHC class I-dependent pathway. Accordingly, immunization with FL containing the OVA-gene induced potent OVA-specific Th1 and Th2 cytokine production. Additionally, OVA-specific CTL responses and antibody production were also observed in systemic compartments including the spleen, upon immunization with the OVA-gene encapsulating FL. These findings suggest that FL is an effective genetic immunization carrier system for the stimulation of antigen-specific immune responses against its encoding antigen.     

Enhanced Liposomal Vaccine Formulation and Performance: Simple Physicochemical and Immunological Approaches

The Dtxd (Diphtheria toxoid) was the first antigen encapsulated within liposomes, their adjuvant properties were discovered (their capacity to enhance the vaccine immunogenicity). The point here is not to propose a new method to prepare this lipossomal vaccine. The central idea is to give new dresses for old vaccines by using classical and well-established liposome preparation method changing only the encapsulation pH and the immunization protocol.

The most appropriate method of Dtxd encapsulation within liposome was based on lipid film hydration in 100 mM citrate buffer, pH 4.0. This was accompanied by changes on protein hydrophobicity, observed by CD and fluorescence spectroscopies. Whenever the Dtxd exposed its hydrophobic residues at pH 4.0, it interacted better with the lipossomal (observed by electrophoretic mobility) film than when its hydrophobic residues were buried (pH 9.0). The Dtxd partition coefficient in Triton-X114 and the acrylamide fluorescence quenching were also pH dependent. Both were bigger at pH 4.0 than at pH 9.0. The relationship protein structure and lipid interaction was pH dependent and now it can be easily maximized to enhance encapsulation of antigens in vaccine development.

Mice were primed with formulations containing 5 μg of Dtxd within liposomes prepared in pH 4.0 or 7.0 or 9.0. The boosters were done 38 or 138 days after the first immunization. The IgM produced by immediate response of all lipossomal formulations were higher than the control (free protein). The response patterns and the immune maturity were measured by IgG₁ and IgG_2a titrations. The IgG₁ titers produced by both formulations at pH 4.0 and 7.0 were at least 2² higher than those produced by mice injected lipossomal formulation at pH 9.0. When the boosters were done, 138 days after priming the mice produced a IgG_2a titer of 2⁹ and the group that received the booster 30 days after priming produced a titer of 2⁵. The strongest antibody production was the neutralizing antibody (2⁴⁵ higher than the control) produced by those mice injected with lipossomal formulation at pH 4.0 with the booster done 138 days after priming. The simple change on lipossomal pH formulation and timing of the booster enhanced both antibody production and selectivity.     

Nanovaccine: A novel approach in immunization

Despite great advances in the field of vaccination, there are still needs for novel and effective vaccines because still no effective vaccines have been produced for some diseases such as malaria, acquired immune deficiency syndrome (AIDS), and tuberculosis. Furthermore, many of the existing vaccines have disadvantages such as failure to stimulate completely the immune system, in vivo instability, high toxicity, the need for cold chain, and multiple administrations. Nanotechnology has been raised as a powerful tool for solving these problems in this regard. Generally, nanovaccines are a new generation of vaccines using nanoparticles (NPs) as carriers and/or adjuvants. Due to the similar scale (size) between the NPs and pathogens, the immune system can be stimulated well, resulting in triggered cellular and humoral immunity responses. Other benefits of the nanovaccines include their better stability in blood flow to increase the shelf life in blood, enhanced immune system stimulation, no need for booster doses, no need to maintain the cold chain, and ability to create active targeting. In addition, nanovaccines have raised the hope to treat diseases such as rheumatoid arthritis, AIDS, malaria, and chronic autoimmune, and so forth.     

Vaccines against enteric infections for the developing world

Since the first licensure of the Sabin oral polio vaccine more than 50 years ago, only eight enteric vaccines have been licensed for four disease indications, and all are given orally. While mucosal vaccines offer programmatically attractive tools for facilitating vaccine deployment, their development remains hampered by several factors:

• — limited knowledge regarding the properties of the gut immune system during early life;
• — lack of mucosal adjuvants, limiting mucosal vaccine development to live-attenuated or killed whole virus and bacterial vaccines;
• — lack of correlates/surrogates of mucosal immune protection; and
• — limited knowledge of the factors contributing to oral vaccine underperformance in children from developing countries.

There are now reasons to believe that the development of safe and effective mucosal adjuvants and of programmatically sound intervention strategies could enhance the efficacy of current and next-generation enteric vaccines, especially in lesser developed countries which are often co-endemic for enteric infections and malnutrition. These vaccines must be safe and affordable for the world''s poorest, confer long-term protection and herd immunity, and must be able to contain epidemics.     

酶联免疫斑点法在新发传染病疫苗研究中的应用

酶联免疫斑点法(ELISPOT)是一项具有较高敏感性和特异性的细胞免疫学检测技术,目前常用于疫苗开发中评价疫苗诱发的细胞免疫效应。我们就ELISPOT技术的原理、具体实验操作、技术优势,及其在新发传染病疫苗研究中的应用等进行综述。     

抗禽流感病毒多表位DNA疫苗的构建及其免疫效力研究

多表位DNA疫苗是建立在常规DNA疫苗基础上的一种新型疫苗。它是用表位作免疫原,这样就比较容易在一个表达载体上克隆病原体的多个抗原基因中具有免疫活性的部分。本试验以H5N1亚型禽流感病毒的HA和NP基因及其表位为基础构建了4个重组质粒：1 pIRES/HA（表达全长的HA基因）;2 pIRES/tHA（只表达HA基因的主要抗原表位区）;3 pIRES/tHANpep（融合表达HA基因的抗原表位区和NP基因的3个CTL表位）;4 pIRES/tHANpep-IFN-γ（用鸡的IFN-γ基因取代质粒pIRES/tHANpep中的neo基因）。分别用这4个重组质粒和空载体质粒pIRES1neo肌注免疫30日龄SPF鸡。免疫3次,间隔为2周,每次每只鸡的剂量为200μg。第3次免疫后两周以高致病性禽流感病毒H5N1强毒攻击,免疫及攻毒前后均采血检测HI抗体效价和外周血CD4⁺、CD8⁺T细胞的变化。结果发现,攻毒前各质粒免疫组均检测不到HI抗体,攻毒后1周存活鸡HI抗体效价迅速升高到64～256。流式细胞仪检测显示外周血CD4⁺、CD8⁺T细胞在疫苗免疫后都有不同程度的升高。空载体质粒对照组鸡（10只）在攻毒后3～8 d内全部死亡,其他各重组质粒免疫组鸡都获得了部分保护,保护率分别是：pIRES/HA组为545%（6/11）,pIRES/tHA组为30%（3/10）,pIRES/tHANPep组为36.3%（4/11）, pIRES/tHANPepIFNγ组为50%（5/10）。这些结果表明我们构建的多表位DNA疫苗能够诱导机体产生特异性免疫应答,并在同型禽流感强毒攻击时对鸡只提供了一定的保护。     

口蹄疫新型疫苗研究进展

口蹄疫(FMD)是一种严重威胁畜牧业发展的重要传染病,目前世界上许多国家和地区都有该病的流行与发生.其控制措施主要是疫苗免疫,虽然传统疫苗在该病的防控中起了重要的作用,但也存在着诸多的缺点.因此研制新型的FMD疫苗是今后的发展方向.本文结合实验室在FMD新型疫苗研究方面所开展的探索性研究工作,综述了国内外在FMD基因工程弱毒苗或灭活苗、蛋白质和合成肽疫苗、空衣壳疫苗、细胞因子增强型疫苗等研究领域所取得的进展.