转基因番茄口服疫苗的研究进展

<正>第1例转基因烟草表达链球菌变异株SpaA(surface protein antigen A)蛋白疫苗的成功研制[1],开启了利用植物表达动物病原抗原蛋白的新纪元。1992年,Mason等[2]提     

Development of a plant-derived subunit vaccine candidate against hepatitis C virus

Summary.  Hepatitis C virus (HCV) is a major cause of acute and chronic hepatitis with over 180 million cases worldwide. Vaccine development for HCV has been difficult. Presently, the virus cannot be grown in tissue culture and there is no vaccine or effective therapy against this virus. In this research, we describe the development of an experimental plant-derived subunit vaccine against HCV. A tobamoviral vector was engineered to encode a consensus sequence of hypervariable region 1 (HVR1), a potential neutralizing epitope of HCV, genetically fused to the C-terminal of the B subunit of cholera toxin (CTB). This epitope was selected from among the amino acid sequences of HVR1 “mimotopes” previously derived by phage display technology. The nucleotide sequence encoding this epitope was designed utilizing optimal plant codons. This mimotope is capable of inducing cross-neutralizing antibodies against different variants of the virus. Plants infected with recombinant tobacco mosaic virus (TMV) engineered to express the HVR1/CTB chimeric protein, contained intact TMV particles and produced the HVR1 consensus peptide fused to the functionally active, pentameric B subunit of cholera toxin. Plant-derived HVR1/CTB reacted with HVR1-specific monoclonal antibodies and immune sera from individuals infected with virus from four of the major genotypes of HCV. Intranasal immunization of mice with a crude plant extract containing the recombinant HVR1/CTB protein elicited both anti-CTB serum antibody and anti-HVR1 serum antibody which specifically bound to HCV virus-like particles. Using plant-virus transient expression to produce this unique chimeric antigen will facilitate the development and production of an experimental HCV vaccine. A plant-derived recombinant HCV vaccine can potentially reduce expenses normally associated with production and delivery of conventional vaccines. Accepted June 2, 2000 Received March 27, 2000     

Oral transgenic plant-based vaccine for hepatitis B

In addition to improving vaccine formulations in order to elicit robust and long-lasting immune responses, there is also an increasing need for improving the manner in which these vaccines are delivered. As most current vaccines are administered by injection by a health care giver, there is the ever-present danger of needlestick injuries. Therefore, needle-free vaccinations are a viable option toward limiting needle-associated injuries and additionally increasing compliance with vaccination schedules, as both children and adults have an aversion to injections. Noninvasive methods of vaccination will also facilitate speed of vaccine delivery and likely also reduce cost, both important factors for health care in developing countries. One alternative to current injectable immunizations is orally delivered vaccines. A specific approach that we and others are evaluating is the use of transgenic plant tissue that expresses vaccine antigens for oral immunization. Herein, we review the development of an oral HBV vaccine expressed in transgenic potato tubers and the immune responses generated in human subjects given this novel vaccine.     

Specific safety and immunogenicity of a subunit vaccine against hepatitis B

The results of trials of a subunit vaccine against hepatitis B in volunteers are presented. The active substance of the vaccine was HBsAg isolated from the plasma of asymptomatic antigen carriers. The preparation under study is highly immunogenic, shows poor reactogenicity, and safety in use.     

可食性转基因植物疫苗的免疫学特性研究

转基因植物疫苗是疫苗研究的一个新热点,本文综述了转基因植物疫苗在体诱导的免疫学特点,包括实验动物和人免疫应答情况,讨论了未来转基因植物疫苗研究重点及将面临的问题和解决对策,并对其应用前景提出展望.     

乙肝疫苗增强细胞因子诱导的杀伤细胞对于转乙型肝炎病毒基因小鼠的治疗作用

目的 观察乙肝疫苗是否增强细胞因子诱导的杀伤细胞(cytokine-induced killer cell,CIK)对于乙型肝炎病毒转基因小鼠(hepatitis B virus transgenic mice,HBV-Tg)的抗病毒作用.方法 给予HBV-Tg腹腔注射CIK细胞,皮下注射乙肝疫苗,用荧光定量PCR检测外周血中HBV DNA水平变化,流式细胞仪检测外周血中T淋巴细胞亚群,并用HE染色观察肝脏的组织病理改变.结果 CIK细胞降低了HBV-Tg鼠外周血中病毒载量,血中CD3~+、CD4~+及CD8~+细胞增多,乙肝疫苗和CIK细胞联合应用后,这种作用增强.结论 乙肝疫苗增强了CIK对于HBV-Tg小鼠的治疗作用,这种增强作用是否通过增加体内CD3~+、CD4~+及CD8~+细胞,尤其是CD8~+细胞而实现,有待进一步研究.     

乙型肝炎病毒多表位抗原DNA疫苗的免疫原性

目的 :探讨HBV复合多表位DNA疫苗诱导体液及细胞免疫的可行性。方法 :将HBV多表位抗原基因BPT克隆到真核表达载体pcDNA3.1中 ,构建重组真核表达载体pcDNA3.1/BPT。将其通过肌肉注射免疫BALB/c小鼠 ,用间接免疫ELISA法、CTL杀伤功能检测和淋巴细胞增殖试验 ,检测特异性体液免疫和细胞免疫的水平 ,并观察其对免疫小鼠的毒副作用。结果 :用重组质粒pcDNA3.1/BPT免疫BALB/c小鼠后 ,在效靶比为 10 0∶1时 ,可诱导显著地特异性CTL应答 (P <0 .0 5 )。ELISA检测免疫小鼠血清特异性IgG的水平明显升高 (P <0 .0 5 )。在BPT基因原核表达蛋白的刺激下 ,免疫小鼠脾淋巴细胞增殖显著 (P <0 .0 5 )。RT PCR分析表明 ,IL 12mRNA的水平亦明显升高。结论 :HBV多表位基因疫苗可诱发特异性免疫应答 ,为预防、治疗性HBV疫苗的研制提供了一定的实验依据     

Production of a vaccine against hepatitis B in Africa: the problems and prospects

Much has been achieved in the field since the time of the development, manufacture, and release of a vaccine against hepatitis B based on the purification and inactivation of hepatitis B surface antigen (HBsAg). Subsequent clinical and field trials demonstrated the immunogenic potency and efficacy of this vaccine and it was hoped that the vaccine would protect millions of people not only from hepatitis B (HB) but possibly also from its sequelae including primary carcinoma of the liver (PCL). This form of liver carcinoma is known to be most prevalent among malignant diseases in men residing in South-East Asia and Africa. The high price of the vaccine is the only obstacle in the way of its large-scale use and achievement of the effective control of this infection. Currently, several South-East Asian countries investigate different approaches to reduce the price of the vaccine against HB to a level acceptable for the population. These approaches include collaboration with reliable companies or institutions of other continents which have the necessary funds and scientific technology. Some of these countries already manufacture a cheaper vaccine against HB or they are just starting it. This paper analyses the attitudes of some African countries to the latest achievements and their efforts directed at the vaccine preparation as well as discusses the situation in them as compared with that in South-East Asia.     

Reactivity and immunogenicity of Engerix B, the recombinant DNA vaccine against hepatitis B

A group of 67 health workers with no markers indicating previous hepatitis B infection were vaccinated against hepatitis B with a new DNA recombinant vaccine, Engerix B (commercially manufactured by Smith-Kline-RIT, Belgium). Three injections were given according to the 0-1-6 schedule. One month after the last injection the vaccinees were tested for anti-HBs antibodies by the enzyme-linked assay. Antibody titers equal or less than 10 mIU/ml were found only in three subjects or in 4.5% of them. Titers ranging from 11 to 99 mIU/ml were found in 7 subjects (10.4%), from 100 to 999 mIU/ml in 28 (41.8%) and those equal or more than 1000 mIU/ml in 29 subjects (43.3%). It is inferred that the seroconversion rate is 95.5%. Only one subject did not develop detectable antibodies but three subjects had titers over 10000 mIU/ml. No one developed overt hepatitis B during the trial nor did the high responders experienced inapparent infections. They were tested for anti HBc with negative results. Postvaccinal reactions were mild and almost exclusively local. There were no complications. For its high immunogenicity and acceptable reactogenicity the Engerix B vaccine has a promising future.     

Characterization and immunogenicity of a candidate subunit vaccine against varicella-zoster virus

This study describes the properties of an inactivated subunit antigen preparation from varicella-zoster virus (VZV)-infected MRC-5 cells by treatment with detergent and formaldehyde, ultracentrifugation over sucrose and acetone precipitation. The method preserved the antigenicity of VZV proteins and several VZV-specific glycoproteins, while virus DNA was less than 20 pg/250 g protein — a putative vaccine dose. The vaccine was immunogenic in rabbits and stimulated antibodies to the major capsid protein as well as to glycoproteins; an immunoprecipitin was shared with a known immune human serum. The preparation contained no infectious VZV with no evidence of side effects in a rabbit or in five human vaccinees during a follow-up period of 6–10 years.     

Phase I/II study of a candidate vaccine designed against the B and E subtypes of HIV-1

A phase I/II trial of a candidate vaccine to prevent HIV infection was carried out in Bangkok, Thailand, testing AIDSVAX B/E (VaxGen, Inc., Brisbane, CA), a bivalent subunit vaccine prepared by combining recombinant gp120 from a subtype B virus (HIV-1MN) with gp120 from a subtype E virus (HIV-1A244) in alum adjuvant. The studies provide human data on the immunogenicity of various dose combination of non-subtype B vaccine antigens. The results suggest that AIDSVAX B/E is safe and immunogenic in humans. The optimal dose for humans in developing countries was 300 microg of each antigen (B and E). Clade E responses were measurably increased by immunizing with gp120 B/E over B alone. Using the B/E combination did not interfere with the response to either clade. Antibodies to AIDSVAX B/E were able to bind to oligomeric gp120 on the surface of cells infected with primary isolates of HIV-1.     

Immunological and epidemiological effectiveness of the HEVAC B vaccine against hepatitis B in a group at enhanced risk of infection

The immunological and epidemiological effectiveness of HEVAC B vaccine against hepatitis B (Pasteur Institute, France) was studied in 215 medical workers of Moscow who had contacts with the blood or preparations thereof. A control group consisted of 155 medical workers. The groups were formed randomly but both included the subjects without HBsAg and anti-HBs. The HEVAC B vaccine was found to be characterized by high immunologic efficacy. Administration of the vaccine induced seroconversion after the 1st, 2nd, and 3rd vaccinations in 36.3%, 77.2%, and 93.9% vaccinees, respectively. In the course of immunization, a marked rise of specific antibody levels was observed. Among the vaccinees no cases of hepatitis B with jaundice were recorded, while in the control group there were 2 cases (1.3%). The vaccine has a low reactogenicity and is safe for use.     

Active pre-exposure immunisation against hepatitis B virus: immunogenicity of hepatitis B vaccine in healthy Thai adults and children

The immunogenicity of plasma derived hepatitis B vaccine (Hevac B) was studied for active pre-exposure immunisation in 176 healthy volunteer adults and 162 randomised children who had no hepatitis B virus markers. All subjects received three injections of 5 micrograms of hepatitis B vaccine intramuscularly at one month intervals. Seroconversion at 2 months after the third dose of vaccine was 96.30 percent in the children and 92.00 percent in the adults with mean anti-HBs titres of 800 mlU/ml and 353 mlU/ml respectively. The difference of anti-HBs levels between these two groups was statistically significant (p less than 0.05). Female adults had exhibited higher immune response to HB vaccine than male adults but there was no seroconversion difference between boys and girls. There were no serious local or systemic side effects of hepatitis B vaccination. It was concluded that active immunisation with plasma derived hepatitis B vaccine in non-immune children and adults is highly effective without any serious side effects or complications. The prevention of horizontal transmission of hepatitis B virus should be done by vaccination in children since they have a much better immune response to hepatitis B vaccine than adults.     

Safety and immunogenicity of a recombinant hepatitis B vaccine

A hepatitis B vaccine produced in yeast by recombinant DNA technology was evaluated using 5-micrograms and 10-micrograms doses in a randomized trial lasting 7 months in 110 male armed forces recruits aged 17-19 years. Results were compared to those of an identical trial of a plasma-derived vaccine. No allergic reactions were observed, and the rate of mild side effects was similar to the plasma-derived vaccine. Seroconversion rates in the first month were 60% (33/55) and 67% (37/55) with the 5-micrograms and 10-micrograms doses of the recombinant vaccine, respectively. All participants seroconverted by 3 months, and none lost antibody. These results are very similar to those for plasma-derived vaccine. Comparison of titres of antibody to hepatitis B surface antigen (anti-HBs) showed a slightly higher level with the 10-micrograms than with the 5-micrograms dose of the recombinant vaccine. Geometric mean titres of anti-HBs after the booster dose were similar in the 5-micrograms and 10-micrograms dose recombinant vaccine groups (2,620 and 2,748 IU/l, respectively) and in the 5-micrograms plasma-derived vaccine group (3,591 IU/l) but significantly higher (9,227 IU/l) with the 10-micrograms dose of the plasma-derived vaccine. These results confirm the safety and immunogenicity of the recombinant vaccine, although further study is needed on the duration of immunity.     

Highly immunogenic and protective recombinant vaccine candidate expressed in transgenic plants

Vaccine development has been hampered by difficulties in developing new and safe adjuvants, so alternative technologies that offer new avenues forward are urgently needed. The goal of this study was to express a monoclonal recombinant immune complex in a transgenic plant. A recombinant protein consisting of a tetanus toxin C fragment-specific monoclonal antibody fused with the tetanus toxin C fragment was designed and expressed. Immune complex formation occurred between individual fusion proteins to form immune complex-like aggregates that bound C1q and FcgammaRIIa receptor and could be targeted to antigen-presenting cells. Unlike antigen alone, the recombinant immune fusion complexes were highly immunogenic in mice and did not require coadministration of an adjuvant (when injected subcutaneously). Indeed, these complexes elicited antibody titers that were more than 10,000 times higher than those observed in animals immunized with the antigen alone. Furthermore, animals immunized with only 1 mug of recombinant immune complex without adjuvant were fully protected against lethal challenge. This the first report on the use of a genetic fusion between antigen and antibody to ensure an optimal expression ratio between the two moieties and to obtain fully functional recombinant immune complexes as a new vaccine model.     

Live nonpathogenic parasitic vector as a candidate vaccine against visceral leishmaniasis

To date, there are no proven vaccines against any form of leishmaniasis. The development of live attenuated vectors shows promise in the field of Leishmania vaccination because these organisms mimic more effectively the course of real infections and can elicit potent activation of the immune system. In the present study, we investigated the potential of a parasitic protozoan that is nonpathogenic to humans, Leishmania tarentolae, as a live candidate vaccine that efficiently targets dendritic cells and lymphoid organs, thus enhancing antigen presentation and consequently influencing the magnitude and quality of T-cell immune responses. We demonstrated that L. tarentolae activates the dendritic cell maturation process and induces T-cell proliferation and the production of gamma interferon, thus skewing CD4(+) T cells toward a Th1 cell phenotype. More importantly, we found that a single intraperitoneal injection of L. tarentolae could elicit a protective immune response against infectious challenge with Leishmania donovani in susceptible BALB/c mice. These results suggest that the use of L. tarentolae as a live vaccine vector may represent a promising approach for improving the effectiveness and safety of candidate live vaccines against Leishmania infections and possibly other intracellular pathogens for which T-cell mediated responses are critical for the development of protective immunity.     

乙型肝炎卡介苗联合疫苗与单价乙型肝炎疫苗免疫效果的比较

目的：比较乙型肝炎卡介苗联合疫苗与单价乙型肝炎疫苗的免疫效果。方法：实验动物采用豚鼠，按0、1、2月三针免疫程序接种，并于每针免疫后1个月采血，ELISA方法检测血清抗体滴度。实验分三部分进行。实验一：三种不同规格的联合疫苗与单价乙型肝炎疫苗的比较；实验二：同一规格连续三批联合疫苗与单价乙型肝炎疫苗的比较；实验三：联合疫苗与两种单价疫苗同时免疫的比较。结果：在三个实验中，联合疫苗组第一针血清抗体滴度均低于对照组，但无统计学差异：联合疫苗组第二、三针血清抗体滴度均高于对照组，也无统计学差异，实验组各组之间无明显差异。结论：联合疫苗组三针免疫程序的HBsAg的效力与单价乙型肝炎疫苗组相似。