通用流感疫苗研发进展

流感病毒感染在世界范围内引起较高的发病率和死亡率。接种流感疫苗是预防和控制流感病毒感染及其严重并发症的有效手段,但由于流感病毒抗原的变异性,导致疫苗毒株与当年的流行毒株的抗原性并不完全匹配,造成流感疫苗的有效性降低,不能有效预防季节性和大流行流感,因此研发通用疫苗成为当前的主要趋势。本文综述了流感疫苗的发展及通用流感疫苗的研发平台,为未来新型流感疫苗的设计和开发提供参考。     

基于流感病毒保守抗原的广谱流感疫苗研究进展

流感是由流感病毒感染引起的严重急性呼吸道传染病,接种流感疫苗是预防流感最经济、安全且有效的措施。目前广泛应用的传统流感疫苗的保护效果受到疫苗株与流行株表面抗原匹配程度的明显影响,难以有效应对因流感病毒发生抗原漂移或抗原转换而产生的无法预料的流行或大流行。因而开发能够诱导广谱和持久免疫的广谱流感疫苗是新型流感疫苗研发的重要方向。流感病毒基质、核蛋白和血凝素茎部结构域作为流感病毒的保守抗原,是当前广谱流感疫苗的主要靶抗原。此文就近年来基于流感病毒保守抗原的广谱流感疫苗的抗原选择、免疫保护制剂、临床研究进展做一综述。     

大流行流感疫苗研发和质量管理中一些问题的探讨

季节性流感疫苗是公认的预防流行性感冒的有力武器,主要预防人流感病毒同型变异株造成的流行和感染.而大流行流感通常由新的流感病毒亚型引起,因此,大流行流感疫苗是一种全新的预防性疫苗.比较季节性流感和大流行流感的产生原因,进而从毒种制备、生产基质、抗原含量、佐剂、免疫效果评价、质控方法、生物安全等各个方面阐述大流行流感疫苗研制中面临的技术问题,同时介绍国外在质量管理方面的技术法规.     

关于诱导广谱和持久免疫的流感疫苗开发的第二次会议报告

能防御不同流感病毒和诱导广谱和持久免疫的新型流感疫苗可以克服现有流感疫苗需每年接种的难题,特别适用于发展中国家,可用来控制流感流行和大流行。WHO于2005年12月在日内瓦召开了咨询会议,回顾了这种流感疫苗的研究现状,并确定了疫苗的研发日程。本文介绍会议的主要结论和建议。     

甲型流感病毒交叉免疫的研究进展

流感是重大的公共卫生问题,可发生全球大流行.研制安全有效的流感疫苗对控制流感至关重要.然而,由于流感病毒的交叉免疫及其机制尚未完全阐明,对研制疫苗带来不利影响.对甲型流感病毒交叉免疫的深入研究必将有助于更好地研制流感疫苗,对预防和控制甲型流感具有重要意义.此文对甲型流感病毒交叉免疫、免疫机制、不同亚型免疫的评价等研究进展进行综述.     

流感病毒血凝素在多种系统中表达的研究进展

流感疫苗是预防流感病毒感染最有效的方法。传统灭活流感疫苗通过在鸡胚中培养病毒后经纯化获得。流感每年都会发生季节性流行,流感病毒高度多变的特性使生产有效疫苗成为一项挑战。为了克服流感疫苗生产对鸡胚的依赖,需要开发新的流感疫苗生产策略。由于血凝素是流感病毒主要表面抗原之一,重组血凝素亚单位疫苗为流感疫苗的生产提供了一个方案。本文将对流感病毒血凝素在大肠埃希菌、毕赤酵母、昆虫细胞、哺乳动物细胞多种系统中表达的研究进行综述。     

广谱流感疫苗

英国Acambis公司正在研制一种广谱流感疫苗,这种疫苗能提供永久的抗流感保护作用,而且还能预防流感大流行。现行的流感疫苗需每年接种,而且每年要调整流感疫苗来针对当前的流行株,而将要包含在疫苗中的毒株则是在前一个流感流行季节结束时选定的,变异株漂移或制造问题可能导致疫苗无效或短缺。Acambis公司参加了一项合作研究,并批准了与佛兰德大学校际生物技术研究所(VIB)的协议。合作研究旨在生产能预防甲、乙型流感病毒的候选疫苗,更重要的是,将不需每年改变疫苗配方。合作将利用A-cambis公司的甲型流感候选疫苗(从美国Apovia公司获得)…     

WHO发布1997/1998流感疫苗组成

在WHO日内瓦总部召开的国际专家会议上发布了1997—1998年流感疫苗的组成。科学家们一直致力于识别流感病毒主要流行株,以便每年能制备出有效的疫苗。与去年推荐的疫苗组成相比,流感疫苗的三种成分中,有一种已被改变。 在2月19日的每年例会上,流感专家建议各国卫生当局和制药公司用三个选定的病毒株生产下一次流感流行季节的疫苗。而建议的时间是相当长的,以使在新流感流行季节开始前制药公司有     

基于神经氨酸酶的流感疫苗研究进展

当前广泛使用的季节性流感疫苗的主要抗原成分包括2个重要的流感病毒表面糖蛋白,血凝素和神经氨酸酶(neuraminidase,NA).研究表明NA抑制性抗体虽然不能防止流感病毒感染,但能有效抑制病毒扩散,因此基于NA设计的疫苗开始受到重视.NA的相对保守性也使此类疫苗有潜力成为广谱流感疫苗.目前基于NA的多种形式流感疫苗,包括DNA疫苗、病毒样颗粒疫苗、重组载体疫苗、重组亚单位疫苗以及联合其他流感病毒蛋白的疫苗等,在动物模型中均表现出诱导交叉保护的能力.此文综述了近年来发表的有关基于NA的流感病毒疫苗的研究.     

细胞培养物作为生产流感疫苗的基质

流感一直是严重的全球性公共卫生问题,近一百年来曾发生过三次大流行。免疫接种是控制流感大流行的最有效措施。鉴于快速大量生产流感疫苗需用受精鸡蛋来培养病毒,因此迫切需要一种可在发生流行时快速、大批量生产疫苗的替代的细胞培养系统。1995年2月16日世界卫生组织(WHO)在日内瓦召开了关于细胞培养物作为生产流感疫苗的基质的会议,讨论了几个实验室关于流感病毒在稳定细胞系中培养的研究结果,并对下一步工作提出了建议。     

流感疫苗的研究进展

流感是我国每年秋冬季常见的呼吸道传染病。接种疫苗是防控流感最为有效的措施。目前,多种类型的流感疫苗正在研发之中或已上市,同时,流感疫苗规模化生产的基质也逐渐从鸡胚转为哺乳动物细胞。此文介绍了流感疫苗的研究进展以及疫苗生产基质的变迁。     

Human Genetics and Responses to Influenza Vaccination

Influenza A and B viruses are negative-strand RNA viruses that cause regular outbreaks of respiratory disease and substantially impact on morbidity and mortality. Our primary defense against the influenza virus infection is provided by neutralizing antibodies that inhibit the function of the virus surface coat proteins hemagglutinin and neuraminidase. Production of these antibodies by B lymphocytes requires help from CD4+ T cells. The most commonly used vaccines against the influenza virus comprise purified preparations of hemagglutinin and neuraminidase, and are designed to induce a protective neutralizing antibody response. Because of regular antigenic change in these proteins (drift and shift mutation), the vaccines have to be administered on an annual basis. Current defense strategies center on prophylactic vaccination of those individuals who are considered to be most at risk from the serious complications of infection (principally individuals aged >65 years and those with chronic respiratory, cardiac, or metabolic disease).The clinical effectiveness of influenza virus vaccination is dependent on several vaccine-related factors, including the quantity of hemagglutinin within the vaccine, the number of doses administered, and the route of immunization. In addition, the immunocompetence of the recipient, their previous exposure to influenza virus and influenza virus vaccines, and the closeness of the match between the vaccine and circulating influenza virus strains, all influence the serologic response to vaccination.However, even when these vaccines are administered to young fit adults a proportion of individuals do not mount a significant serologic response to the vaccine. It is not clear whether these nonresponding individuals are genetically pre-programmed to be nonresponders or whether failure to respond to the vaccine is a random event. There is good evidence that nonresponsiveness to hepatitis B vaccine, another purified protein vaccine, is at least partially modulated by an individual's human leucocyte antigen (HLA) alleles. Because CD4+ T cells, which control the neutralizing antibody response to influenza virus, recognize antigens in association with HLA class II molecules, we recently conducted a small study to investigate whether there was any association between HLA class II molecules and nonresponsiveness to influenza virus vaccination. This work revealed that the HLA-DRB1*0701 allele was over represented among persons who fail to mount a neutralizing antibody response. This preliminary finding is important because it potentially identifies a group who may not be protected by current vaccination strategies. Further investigation into the role of HLA polymorphisms and nonresponse to influenza virus vaccination, and vaccination against viruses in general, is clearly required.     

Development of Stable Influenza Vaccine Powder Formulations: Challenges and Possibilities

Influenza vaccination represents the cornerstone of influenza prevention. However, today all influenza vaccines are formulated as liquids that are unstable at ambient temperatures and have to be stored and distributed under refrigeration. In order to stabilize influenza vaccines, they can be brought into the dry state using suitable excipients, stabilizers and drying processes. The resulting stable influenza vaccine powder is independent of cold-chain facilities. This can be attractive for the integration of the vaccine logistics with general drug distribution in Western as well as developing countries. In addition, a stockpile of stable vaccine formulations of potential vaccines against pandemic viruses can provide an immediate availability and simple distribution of vaccine in a pandemic outbreak. Finally, in the development of new needle-free dosage forms, dry and stable influenza vaccine powder formulations can facilitate new or improved targeting strategies for the vaccine compound. This review represents the current status of dry stable inactivated influenza vaccine development. Attention is given to the different influenza vaccine types (i.e. whole inactivated virus, split, subunit or virosomal vaccine), the rationale and need for stabilized influenza vaccines, drying methods by which influenza vaccines can be stabilized (i.e. lyophilization, spray drying, spray-freeze drying, vacuum drying or supercritical fluid drying), the current status of dry influenza vaccine development and the challenges for ultimate market introduction of a stable and effective dry-powder influenza vaccine.     

Recombinant influenza B virus HA and NA antigens administered in equivalent amounts are immunogenically equivalent and induce equivalent homotypic and broader heterovariant protection in mice than conventional and live influenza vaccines

Influenza B virus is an important cause of acute upper respiratory disease in humans. Vaccination is the primary method of control of influenza related disease, yet vaccine methodology and production technology have not changed in over 40 years. In this study, we compare the efficacy of recombinant baculovirus produced protein based neuraminidase containing influenza B vaccines with conventional inactivated influenza vaccine (CIV) and live-attenuated influenza vaccine (LAIV) in a murine model. All HA containing vaccines stimulated antibody and protected against an infectious challenge with homotypic virus (B/Harbin/7/94), only recombinant protein based (rHA + rNA and rNA) vaccines containing immunogenic amounts of influenza neuraminidase (NA) protected against challenge with a significantly antigenically different heterovariant virus (B/Beijing/243/1997), as measured by a reduction in mean pulmonary virus titers. This report demonstrates with influenza B virus, in a side-by-side comparison with CIV and LAIV in a murine model system the superiority of vaccines containing immunogenic NA over currently approved CIV and LAIV vaccines.     

Immunogenicity and protection of oral influenza vaccines formulated into microparticles

Influenza is a deadly disease affecting humans and animals. It is recommended that every individual should be vaccinated annually against influenza. Considering the frequency of administration of this vaccine, we have explored the oral route of vaccination with a microparticulate formulation. Microparticles containing inactivated influenza A/PR/34/8 H1N1 virus with Eudragit S and trehalose as a matrix were prepared using the Buchi spray dryer. Particle size distribution of microparticles was measured and the bioactivity of vaccine in a microparticle form was analyzed using a hemagglutination activity test. Furthermore, the efficacy of microparticle vaccines was evaluated in vivo in Balb/c mice. Analysis of serum samples showed that microparticles resulted in enhanced antigen‐specific immunoglobulin G (IgG), IgG1, and IgG2a antibodies. Upon challenge with homologous and heterologous influenza viruses, microparticle vaccines showed significantly increased levels of protection. Use of microparticles to deliver vaccines could be a promising tool for the development of an oral influenza vaccine.     

Susceptibility of human influenza viruses from Australasia and South East Asia to the neuraminidase inhibitors zanamivir and oseltamivir

Human influenza viruses isolated from Australasia (Australia and New Zealand) and South East Asia were analysed to determine their sensitivity to the NA inhibitor drugs, zanamivir and oseltamivir. A total of 532 strains isolated between 1998 and 2002 were tested using a fluorescence-based assay to measure the relative inhibition of NA activity over a range of drug concentrations. Based on median IC50 values, influenza A viruses (with neuraminidase subtypes N1 and N2) were more sensitive to both the NA inhibitors than were influenza B strains. Influenza A viruses with a N1 subtype and influenza B strains both demonstrated a greater sensitivity to zanamivir than to oseltamivir carboxylate, whereas influenza A strains with a N2 subtype were more susceptible to oseltamivir carboxylate. For each of the neuraminidase types, IC50 values for viruses from Australasia and South East Asia were found to be comparable. Based on the data prior to and following the licensing of the drugs into the respective regions, the use of the NA inhibitors did not appear to have a significant impact on the susceptibility of the viruses tested to zanamivir or oseltamivir carboxylate.     

Influenza virosome/DNA vaccine complex as a new formulation to induce intra-subtypic protection against influenza virus challenge

Influenza virosome is one of the commercially available vaccines that have been used for a number of years. Like other influenza vaccines, the efficacy of the virosomal vaccine is significantly compromised when circulating viruses do not have a good match with vaccine strains due to antigenic drift or less frequent emergence of a pandemic virus. A major advantage of virosome over other influenza vaccine platforms is its intrinsic adjuvant activity and potential carrier capability which have been exploited in this study to broaden vaccine protectivity by incorporating a conserved component of influenza virus in seasonal vaccine formulation. Influenza nucleoprotein (NP)-encoding plasmid was adsorbed onto surface of influenza virosomes as a virosome/DNA vaccine complex. Mice were immunized with a single dose of the influenza virosome attached with the NP plasmid or NP plasmid alone where both influenza virosomes and NP gene were derived from influenza A virus H1N1 New/Caledonia strain. Analysis of the cellular immune responses showed that 5μg (10-fold reduced dose) of the NP plasmid attached to the virosomes induced T cell responses equivalent to those elicited by 50μg of NP plasmid alone as assessed by IFN-γ and granzyme B ELISPOT. Furthermore, the influenza virosome/NP plasmid complex protected mice against intra-subtypic challenge with the mouse adapted H1N1 PR8 virus, while mice immunized with the virosome alone did not survive. Results of hemagglutination inhibition test showed that the observed intra-subtypic cross-protection could not be attributed to neutralizing antibodies. These findings suggest that influenza virosomes could be equipped with an NP-encoding plasmid in a dose-sparing fashion to elicit anti-influenza cytotoxic immune responses and broaden the vaccine coverage against antigenic drift.     

Influenza viruses: basic biology and potential drug targets

Influenza A and influenza B viruses are continuing causes of morbidity and mortality on an annual basis. Influenza A viruses have historically caused periodic pandemics in the human population, sometimes with devastating consequences, such as in 1918. Fears of a new pandemic have increased in recent years because of continuing outbreaks of highly pathogenic H5N1 avian influenza viruses in birds with occasional, but often lethal infection of humans. Despite their importance as human pathogens, the antiviral drugs approved to treat influenza virus infections are currently limited to two targets, the viral neuraminidase and the viral ion channel, M2. The use of the M2 inhibitors amantadine and rimantadine is further limited by the propensity of these drugs to select for drug resistant variants. However, the replication cycle of influenza viruses has been intensively studied and is receiving increased attention. New opportunities exist to develop novel antiviral strategies targeting these viruses.     

Vaccination strategies and vaccine formulations for epidemic and pandemic influenza control

Influenza viruses of the H5N1 subtype cause an ever-increasing number of bird-to-human transmissions and a pandemic outbreak caused by these viruses is imminent. Therefore, the availability of safe and effective vaccines is highly desirable and their development considered a priority. However, using production and use of seasonal influenza vaccine as template for the production of pandemic H5N1 vaccines did not yield effective vaccines. High antigen doses were required to induce appreciable antibody responses. In addition, limited production capacity and long production times are other disadvantages of conventional influenza vaccine preparations. Here, we review recent developments that will contribute to a more rapid availability of sufficient doses of highly efficacious and safe pandemic influenza vaccines. The new developments include the establishment of novel methods to prepare vaccine strains, novel production technologies and the use of novel adjuvants and alternative vaccine formulations.