Aerosolized adenovirus-vectored vaccine as an alternative vaccine delivery method

Conventional parenteral injection of vaccines is limited in its ability to induce locally-produced immune responses in the respiratory tract, and has logistical disadvantages in widespread vaccine administration. Recent studies suggest that intranasal delivery or vaccination in the respiratory tract with recombinant viral vectors can enhance immunogenicity and protection against respiratory diseases such as influenza and tuberculosis, and can offer more broad-based generalized protection by eliciting durable mucosal immune responses. Controlled aerosolization is a method to minimize vaccine particle size and ensure delivery to the lower respiratory tract. Here, we characterize the dynamics of aerosolization and show the effects of vaccine concentration on particle size, vector viability, and the actual delivered dose of an aerosolized adenoviral vector. In addition, we demonstrate that aerosol delivery of a recombinant adenoviral vaccine encoding H1N1 hemagglutinin is immunogenic and protects ferrets against homologous viral challenge. Overall, aerosol delivery offers comparable protection to intramuscular injection, and represents an attractive vaccine delivery method for broad-based immunization campaigns.     

On vaccine efficacy and reproduction numbers

We consider the impact of a vaccination programme on the transmission potential of the infection in large populations. We define a measure of vaccine efficacy against transmission which combines the possibly random effect of the vaccine on individual susceptibility and infectiousness. This definition extends some previous work in this area to arbitrarily heterogeneous populations with one level of mixing, but leads us to question the usefulness of the concept of vaccine efficacy against infectiousness. We derive relationships between vaccine efficacy against transmission, vaccine coverage and reproduction numbers, which generalize existing results. In particular we show that the projected reproduction number RV does not depend on the details of the vaccine model, only on its overall effect on transmission. Explicit expressions for RV and the basic reproduction number R0 are obtained in a variety of settings. We define a measure of projected effectiveness of a vaccination programme PE=1-(RV/R0) and investigate its relationship with efficacy against transmission and vaccine coverage. We also study the effective reproduction number Re(t) at time t. Monitoring Re(t) over time is an important aspect of programme surveillance. Programme effectiveness PE is less sensitive than RV or the critical vaccination threshold to model assumptions. On the other hand Re(t) depends on the details of the vaccine model.     

Requisite elements in vaccine immunity to Blastomyces dermatitidis: plasticity uncovers vaccine potential in immune-deficient hosts

Understanding fundamental mechanisms of vaccine immunity will allow proper use and optimization of vaccines. Vaccination with a genetically engineered, live, attenuated strain of Blastomyces dermatitidis carrying a targeted deletion at the BAD1 locus confers sterilizing immunity against experimental lethal pulmonary infection. We found in this study that alphabeta T cells are requisite for durable vaccine immunity, whereas other T and B cells are dispensable. In immune-competent animals, CD4(+) T-cell derived cytokines TNF-alpha and IFN-gamma mediate vaccine immunity. Surprisingly, these factors are dispensable in immune-deficient animals, which rely on alternate mechanisms for robust vaccine immunity, yet still require O(2)(-) production rather than generation of NO. Our results clarify the cellular and molecular bases behind the first genetically engineered fungal vaccine. They also illustrate a sharp difference in vaccine mechanisms between immune-competent and immune-deficient hosts, which underscores the plasticity of residual immune elements in compromised hosts, and points to the feasibility of developing vaccines against invasive fungal infection in this fast growing patient population.     

Experimental vaccine strategies for cancer immunotherapy

Recently, cancer immunotherapy has emerged as a therapeutic option for the management of cancer patients. This is based on the fact that our immune system, once activated, is capable of developing specific immunity against neoplastic but not normal cells. Increasing evidence suggests that cell-mediated immunity, particularly T-cell-mediated immunity, is important for the control of tumor cells. Several experimental vaccine strategies have been developed to enhance cell-mediated immunity against tumors. Some of these tumor vaccines have generated promising results in murine tumor systems. In addition, several phase I/II clinical trials using these vaccine strategies have shown extremely encouraging results in patients. In this review, we will discuss many of these promising cancer vaccine strategies. We will pay particular attention to the strategies employing dendritic cells, the central player for tumor vaccine development.     

Veterinary and human vaccine evaluation methods

Despite the universal importance of vaccines, approaches to human and veterinary vaccine evaluation differ markedly. For human vaccines, vaccine efficacy is the proportion of vaccinated individuals protected by the vaccine against a defined outcome under ideal conditions, whereas for veterinary vaccines the term is used for a range of measures of vaccine protection. The evaluation of vaccine effectiveness, vaccine protection assessed under routine programme conditions, is largely limited to human vaccines. Challenge studies under controlled conditions and sero-conversion studies are widely used when evaluating veterinary vaccines, whereas human vaccines are generally evaluated in terms of protection against natural challenge assessed in trials or post-marketing observational studies. Although challenge studies provide a standardized platform on which to compare different vaccines, they do not capture the variation that occurs under field conditions. Field studies of vaccine effectiveness are needed to assess the performance of a vaccination programme. However, if vaccination is performed without central co-ordination, as is often the case for veterinary vaccines, evaluation will be limited. This paper reviews approaches to veterinary vaccine evaluation in comparison to evaluation methods used for human vaccines. Foot-and-mouth disease has been used to illustrate the veterinary approach. Recommendations are made for standardization of terminology and for rigorous evaluation of veterinary vaccines.     

痢疾菌苗研究进展

痢疾是全世界范围内流行的肠道传染病。随着分子生物学技术的发展,迄今已构建了新一代预防痢疾的疫苗,其中包括:具有侵袭力和不具侵袭力的单价口服活菌苗候选株;它们与大肠杆菌、伤寒沙门氏菌和血清型不同的痢疾杆菌组成的双价和三价菌苗候选株;以及以脂多糖和核糖体为基础的不经胃肠的组分菌。猴体和人体试验证明它们安全有效。预计在未来的10年中,将会有一个或几个安全有效的痢疾疫苗投放市场。     

Optimizing vaccine development

Optimizing the development of modern molecular vaccines requires a complex series of interdisciplinary efforts involving basic scientists, immunologists, molecular biologists, clinical vaccinologists, bioinformaticians and epidemiologists. This review summarizes some of the major issues that must be carefully considered. The intent of the authors is to briefly describe key components of the development process to give the reader an overview of the challenges faced from vaccine concept to vaccine delivery. Every vaccine requires unique features based on the biology of the pathogen, the nature of the disease and the target population for vaccination. This review presents general concepts relevant for the design and development of ideal vaccines protective against diverse pathogens.     

Approaches to HIV vaccine design.

Contemporary vaccines are relying increasingly on modern biotechnology and a vaccine against the AIDS virus is expected to depend even more on new technological advances. Four basic areas of vaccine development are discussed in this context: (1) selection and preparation of candidate immunogens; (2) presentation of immunogens to the immune system; (3) pre-clinical testing of vaccine candidates; and (4) monitoring of vaccine clinical trials.     

细菌芽胞—— 一种新型的疫苗载体

杆菌属的芽胞作为益生菌已经应用于人和动物的食品生产和细菌疗法.目前,芽胞作为一种新型的疫苗载体,开始用于破伤风、炭疽等疫苗的研究.与目前的第二代疫苗相比,细菌芽胞热稳定性好,遗传操作方便,是一种理想的疫苗载体.本文就其作为疫苗载体的相关研究进行综述.     

Bacterial otitis media: current vaccine development strategies

Otitis media is the most common reason for children less than 5 years of age to visit a medical practitioner. Whilst the disease rarely results in death, there is significant associated morbidity. The most common complication is loss of hearing at a critical stage of the development of speech, language and cognitive abilities in children. The cause and pathogenesis of otitis media is multifactorial. Among the contributing factors, the single most important are viral and bacterial infections. Infection with respiratory syncytial virus, influenza viruses, para-influenza viruses, enteroviruses and adenovirus are most commonly associated with acute and chronic otitis media. Streptococcus pneumoniae, non-typeable Haemophilus influenzae and Moraxella catarrhalis are the most commonly isolated bacteria from the middle ears of children with otitis media. Treatment of otitis media has largely relied on the administration of antimicrobials and surgical intervention. However, attention has recently focused on the development of a vaccine. For a vaccine to be effective against bacterial otitis media, it must, at the very least, contain antigens that induce a protective immune response in the middle ear against the three most common infecting bacteria. Whilst over the past decade there has been significant progress in the development of vaccines against invasive S. pneumoniae disease, these vaccines are less efficacious for otitis media. The search for candidate vaccine antigens for non-typeable H. influenzae are well advanced whilst less progress has been made for M. catarrhalis. No human studies have been conducted for non-typeable H. influenzae or M. catarrhalis and the concept of a tribacterial vaccine remains to be tested in animal models. Only when vaccine antigens are determined and an understanding of the immune responses induced in the middle ear by infection and immunization is gained will the formulation of a tribacterial vaccine against otitis media be possible.     

Waiting for the vaccine: sporozoite vaccine research entails important progress in malaria epidemiology.

The research efforts aimed at developing a vaccine against malaria, although failing thus far in their main objective, have produced molecular tools of great utility for epidemiological studies. For example, monoclonal antibodies directed against the repeats of Plasmodium circumsporozoite (CS) protein allowed the 2-site assay for detecting sporozoites in mosquitoes to be established. This immunoassay is advantageous compared with the conventional method of salivary gland dissection and microscopic examination, for it makes the identification of the sporozoite species possible, thanks to species-specific aminoacid sequences of the CS repeats. Other examples of vaccine research-derived tools are synthetic peptides reproducing the repetitive part of the CS protein, which allow antibodies to sporozoites, in individuals exposed to malaria, to be detected. Antibodies to the CS repeats of Plasmodium (Laverania) falciparum proved to be a reliable indicator of the intensity of malaria transmission and, therefore, were suitable for monitoring the impact of malaria control programmes. Finally, a project is outlined that, relying on the application of these tools, will aim at characterizing the transmission of Plasmodium (Plasmodium) malariae and at unveiling the possible relationship among different species thriving in the same distribution area, an issue which may become of relevance in view of the likely introduction of a vaccine directed against a single species.     

Comparative immunogenecity of foot and mouth disease virus antigens in FMD-haemorrhagic septicaemia combined vaccine and FMD vaccine alone in buffalo calves

Humoral immune response was evaluated by monitoring the serum antibody titres and virus specific IgM titres against Foot and Mouth Disease (FMD) virus antigens in serum samples obtained from different groups of calves inoculated with combined vaccine or FMD vaccine alone, on 0, 7, 14, 21, 28, 42 and 56 days post-vaccination (DPV). The cellular immune response was monitored by MTT based lymphoproliferation in peripheral blood mononuclear cell cultures. Higher liquid phase blocking (LPB) ELISA antibody titres were observed in calves receiving combined vaccine as compared to calves immunized with FMD vaccine alone with the peak titres in both the groups obtained on 21 days post-vaccination. However, the virus specific IgM titres were significantly higher in group of calves inoculated with combined vaccine than FMD vaccine alone. The lymphoproliferative responses against FMDV types O, A22 and Asia 1 in the groups receiving combined vaccine and FMD vaccine alone started increasing gradually after day 14 and reached peak levels on 28 DPV followed by a gradual decline subsequently. The group receiving combined vaccine showed higher proliferative responses on in vitro stimulation with FMD virus type O, whereas, with FMD virus type Asia 1, the responses were significantly higher on 14 and 21 DPV as compared to the group immunized with FMD vaccine alone. However, in the group receiving combined vaccine, the responses on in vitro stimulation with FMD virus type A22 were significantly higher than FMD vaccine alone group on all DPV except on 42 DPV.     

Human and animal vaccine contaminations

Vaccination is one of the most important public health accomplishments. However, since vaccine preparation involves the use of materials of biological origin, vaccines are subject to contamination by micro-organisms. In fact, vaccine contamination has occurred; a historical example of vaccine contamination, for example, can be found in the early days of development of the smallpox vaccine. The introduction of new techniques of vaccine virus production on cell cultures has lead to safer vaccines, but has not completely removed the risk of virus contamination. There are several examples of vaccine contamination, for example, contamination of human vaccines against poliomyelitis by SV40 virus from the use of monkey primary renal cells. Several veterinary vaccines have been contaminated by pestiviruses from foetal calf serum.These incidents have lead industry to change certain practices and regulatory authorities to develop more stringent and detailed requirements. But the increasing number of target species for vaccines, the diversity of the origin of biological materials and the extremely high number of known and unknown viruses and their constant evolution represent a challenge to vaccine producers and regulatory authorities.     

Live bivalent vaccine for parainfluenza and influenza virus infections

Influenza and human parainfluenza virus infections are of both medical and economical importance. Currently, inactivated vaccines provide suboptimal protection against influenza, and vaccines for human parainfluenza virus infection are not available, underscoring the need for new vaccines against these respiratory diseases. Furthermore, to reduce the burden of vaccination, the development of multivalent vaccines is highly desirable. Thus, to devise a single vaccine that would elicit immune responses against both influenza and parainfluenza viruses, we used reverse genetics to generate an influenza A virus that possesses the coding region for the hemagglutinin/neuraminidase ectodomain of parainfluenza virus instead of the influenza virus neuraminidase. The recombinant virus grew efficiently in eggs but was attenuated in mice. When intranasally immunized with the recombinant vaccine, all mice developed antibodies against both influenza and parainfluenza viruses and survived an otherwise lethal challenge with either of these viruses. This live bivalent vaccine has obvious advantages over combination vaccines, and its method of generation could, in principle, be applied in the development of a "cocktail" vaccine with efficacy against several different infectious diseases.     

Protective efficacy of a recombinant plague vaccine when co-administered with another sub-unit or live attenuated vaccine

Vaccines against bioterrorism agents offer the prospect of providing high levels of protection against airborne pathogens. However, the diversity of the bioterrorism threat means that it may be necessary to use several vaccines simultaneously. In this study we have investigated whether there are changes to the protective immune response to a recombinant sub-unit plague vaccine when it is co-administered with other sub-unit or live attenuated vaccines. Our results indicate that the co-administration of these vaccines did not influence the protection afforded by the plague vaccine. However, the co-administration of the plague sub-unit vaccine with a live vaccine resulted in markedly increased levels of IgG2a subclass antibodies, and markedly reduced levels of IgG1 subclass antibodies, to the plague sub-unit vaccine. This finding might have implications when considering the co-administration of other vaccine combinations.     

丙型肝炎病毒（HCV）实验性疫苗的研究进展

丙型肝炎病毒是引起输血相关肝炎及慢性肝炎、肝硬化、肝癌的主要病原,目前尚无有效的治疗与预防手段。本文将综述HCV感染所引起的机体免疫应答及近年来实验性疫苗（主要是DNA疫苗、病毒载体疫苗及联合疫苗）的研究进展。     

Surface-displayed viral antigens on Salmonella carrier vaccine

We have developed a recombinant live oral vaccine using the ice-nucleation protein (Inp) from Pseudomonas syringae to display viral antigens on the surface of Salmonella spp. Fusion proteins containing viral antigens were expressed in the oral vaccine strain, Salmonella typhi Ty21a. Surface localization was verified by immunoblotting and fluorescence-activated cell sorting. The immunogenicity of surface-displayed viral antigens on the recombinant live vaccine strain was assessed in mice inoculated intranasally and intraperitoneally. Inoculation resulted in significantly higher serum antibody level than those induced by viral antigens expressed intracellularly. Thus, this multivalent mucosal live vaccine may provide an effective means for inducing mucosal or systemic immune responses against multiple viral antigens.     

Exchanging ESAT6 with TB10.4 in an Ag85B fusion molecule-based tuberculosis subunit vaccine: efficient protection and ESAT6-based sensitive monitoring of vaccine efficacy

Previously we have shown that Ag85B-ESAT-6 is a highly efficient vaccine against tuberculosis. However, because the ESAT-6 Ag is also an extremely valuable diagnostic reagent, finding a vaccine as effective as Ag85B-ESAT-6 that does not contain ESAT-6 is a high priority. Recently, we identified a novel protein expressed by Mycobacterium tuberculosis designated TB10.4. In most infected humans, TB10.4 is strongly recognized, raising interest in TB10.4 as a potential vaccine candidate and substitute for ESAT-6. We have now examined the vaccine potential of this protein and found that vaccination with TB10.4 induced a significant protection against tuberculosis. Fusing Ag85B to TB10.4 produced an even more effective vaccine, which induced protection against tuberculosis comparable to bacillus Calmette-Guerin vaccination and superior to the individual Ag components. Thus, Ag85B-TB10 represents a new promising vaccine candidate against tuberculosis. Furthermore, having now exchanged ESAT-6 for TB10.4, we show that ESAT-6, apart from being an excellent diagnostic reagent, can also be used as a reagent for monitoring vaccine efficacy. This may open a new way for monitoring vaccine efficacy in clinical trials.     

DTaP-Hib联合疫苗中Hib-TT免疫原性研究

考查DTaP-Hib联合疫苗中Hib-TT的免疫原性,对其剂量、免疫持久性和抗原相容性进行分析。将不同剂量的Hib-TT、DTaP-Hib联合疫苗分别免疫小鼠,设单价的Hib-TT结合疫苗为对照,末次免疫后1、2、4、6、8、10w分别采集血清测定血清中Hib多糖抗体滴度。结果显示,不同剂量的Hib-TT和DTaP疫苗联合后均具有较好的免疫原性,血清中Hib多糖抗体阳转率达100%,并具有剂量效应和较好的免疫持久性。2.5μg剂量Hib-TT的DTaP-Hib联合疫苗免疫小鼠后1~2w诱导产生的Hib多糖抗体水平显著性地低于单价Hib-TT(P<0.05),4~10w,二者的Hib多糖抗体水平无显著性差异(P>0.05)。5μg剂量Hib-TT的DTaP-Hib联合疫苗在免疫小鼠后1w诱导产生的Hib多糖抗体水平与单价2.5μg剂量Hib-TT无显著性差异(P>0.05),免后2~10w则显著性地高于单价2.5μg剂量Hib-TT(P<0.001)。Hib-TT和DTaP疫苗联合后,仍然具有较好的免疫原性、剂量效应和免疫持久性;其抗原性干扰只是暂时的。     

Influence of BCG vaccine strain on the immune response and protection against tuberculosis

The Bacille Calmette–Guérin (BCG) vaccine has been used for more than 80 years to protect against tuberculosis. Worldwide, over 90% of children are immunized with BCG, making it the most commonly administered vaccine, with more than 120 million doses used each year. Although new tuberculosis vaccines are under investigation, BCG will remain the cornerstone of the strategy to fight the worsening tuberculosis pandemic for the foreseeable future. The recent delineation of genetic differences between BCG vaccine strains has renewed interest in the influence of the vaccine strain on the protective efficacy against tuberculosis. This review critically examines the data from animal and human studies comparing BCG vaccine strains. Although there is good evidence to support the notion that the induced immune response and protection afforded against tuberculosis differs between BCG vaccine strains, currently, there are insufficient data to favour or recommend one particular strain. Identifying BCG strains with superior protection would have a dramatic effect on tuberculosis control at a population level: a small increment in protection provided by BCG immunization will prevent large numbers of cases of severe tuberculosis and deaths, particularly in children.