Accelerate Vaccine Development Research Articles

Controlled human infection with RSV: The opportunities of experimental challenge

Despite the recent explosion in RSV vaccine development, there remain substantial hurdles to overcome before licensing of effective vaccines will allow widespread use, particularly in high-risk populations. Incomplete understanding of mechanisms and correlates of protection against RSV mean that, for the time being, successful RSV vaccines must directly demonstrate efficacy, which necessitates large and costly clinical trials in naturally infected patients. To mitigate the risks inherent in progressing to these late-stage trials, experimental human RSV infection studies have recently been re-established, representing the interface between pre-clinical models and observational studies of patients. Not only can they be used for early proof-of-concept clinical trials to test vaccine efficacy, but human challenge studies also offer the potential to better understand protective immunity against RSV infection to improve vaccine design and delivery. In the past, controlled human infection studies with RSV have been instrumental in elucidating the influence of factors such as route of infection and type of inoculum on the course of disease. Recently, efficacy trials of novel RSV antiviral drugs have also been successfully undertaken. Now, with advances in technology, detailed investigations of human mucosal immunity in the RSV-infected airway are possible. These have indicated defects in RSV-induced humoral and CD8+ T cell immunity that may contribute to the recurrent symptomatic infection that occurs throughout life and should be circumvented by optimal vaccines. Here, we discuss the insights derived from RSV human challenge models; the major impediments to their more widespread uptake; and their potential benefit in accelerating vaccine development, including future directions to further enhance the relevance of these models to at-risk patient populations.

Development of World Health Organization (WHO) recommendations for appropriate clinical trial endpoints for next-generation Human Papillomavirus (HPV) vaccines

The World Health Organization (WHO) serves as a key organization to bring together experts along the continuum of vaccine development and regulatory approval, among its other functions. Using the revision of WHO's guidelines on prophylactic human papillomavirus (HPV) vaccine as an example, we describe the process by which (1) a need to revise the guidelines was identified; (2) a group of stakeholders with complementary expertise and key questions were identified; (3) a scientific review was conducted; (4) consensus on revisions was achieved; (5) guidelines were updated, reviewed widely, and approved. This multi-year process resulted in the consensus that regulatory agencies could consider additional endpoints, such as persistent HPV infection or immune equivalence, depending on the design of the HPV vaccine trials. Updating the guidelines will now accelerate vaccine development, reduce costs of clinical trials, and lead to faster regulatory approval.

Bovine Tuberculosis in Cattle: Vaccines, DIVA Tests, and Host Biomarker Discovery.

Bovine tuberculosis remains a major economic and animal welfare concern worldwide. Cattle vaccination is being considered as part of control strategies. This approach, used alongside conventional control policies, also requires the development of vaccine-compatible diagnostic assays to distinguish vaccinated from infected animals (DIVA). We discuss progress made on optimizing the only potentially available vaccine, bacille Calmette Guérin (BCG), and on strategies to improve BCG efficacy. We also describe recent advances in DIVA development based on the detection of host cellular immune responses by blood-testing or skin-testing approaches. Finally, to accelerate vaccine development, definition of host biomarkers that provide meaningful stage-gating criteria to select vaccine candidates for further testing is highly desirable. Some progress has also been made in this area of research, and we summarize studies that defined either markers predicting vaccine success or markers that correlate with disease stage or severity.

Plug-and-Display: decoration of Virus-Like Particles via isopeptide bonds for modular immunization.

Virus-like particles (VLPs) are non-infectious self-assembling nanoparticles, useful in medicine and nanotechnology. Their repetitive molecularly-defined architecture is attractive for engineering multivalency, notably for vaccination. However, decorating VLPs with target-antigens by genetic fusion or chemical modification is time-consuming and often leads to capsid misassembly or antigen misfolding, hindering generation of protective immunity. Here we establish a platform for irreversibly decorating VLPs simply by mixing with protein antigen. SpyCatcher is a genetically-encoded protein designed to spontaneously form a covalent bond to its peptide-partner SpyTag. We expressed in E. coli VLPs from the bacteriophage AP205 genetically fused to SpyCatcher. We demonstrated quantitative covalent coupling to SpyCatcher-VLPs after mixing with SpyTag-linked to malaria antigens, including CIDR and Pfs25. In addition, we showed coupling to the VLPs for peptides relevant to cancer from epidermal growth factor receptor and telomerase. Injecting SpyCatcher-VLPs decorated with a malarial antigen efficiently induced antibody responses after only a single immunization. This simple, efficient and modular decoration of nanoparticles should accelerate vaccine development, as well as other applications of nanoparticle devices.

A CRISPR/Cas9 and Cre/Lox system-based express vaccine development strategy against re-emerging Pseudorabies virus.

Virus evolves rapidly to escape vaccine-induced immunity, posing a desperate demand for efficient vaccine development biotechnologies. Here we present an express vaccine development strategy based on CRISPR/Cas9 and Cre/Lox system against re-emerging Pseudorabies virus, which caused the recent devastating swine pseudorabies outbreak in China. By CRISPR/Cas9 system, the virulent genes of the newly isolated strain were simultaneously substituted by marker genes, which were subsequently excised using Cre/Lox system for vaccine safety concern. Notably, single cell FACS technology was applied to further promote virus purification efficiency. The combination of these state-of-art technologies greatly accelerated vaccine development. Finally, vaccination and challenge experiments proved this vaccine candidate’s protective efficacy in pigs and the promise to control current pseudorabies outbreak. This is, to our knowledge, the first successful vaccine development based on gene edit technologies, demonstrating these technologies leap from laboratory to industry. It may pave the way for future express antiviral vaccine development.

The use of systems biology and immunological big data to guide vaccine development.

Editorial summaryHigh-throughput technologies applied to the analysis of vaccine responses are likely to reveal the mechanisms responsible for vaccine-induced protection, aid understanding of vaccine safety and help accelerate vaccine development and clinical trials.

New approaches to understanding the immune response to vaccination and infection

The immune system is a network of specialized cell types and tissues that communicates via cytokines and direct contact, to orchestrate specific types of defensive responses. Until recently, we could only study immune responses in a piecemeal, highly focused fashion, on major components like antibodies to the pathogen. But recent advances in technology and in our understanding of the many components of the system, innate and adaptive, have made possible a broader approach, where both the multiple responding cells and cytokines in the blood are measured. This systems immunology approach to a vaccine response or an infection gives us a more holistic picture of the different parts of the immune system that are mobilized and should allow us a much better understanding of the pathways and mechanisms of such responses, as well as to predict vaccine efficacy in different populations well in advance of efficacy studies. Here we summarize the different technologies and methods and discuss how they can inform us about the differences between diseases and vaccines, and how they can greatly accelerate vaccine development.

MicroRNA expression profiling of PPD-B stimulated PBMC from M. bovis-challenged unvaccinated and BCG vaccinated cattle

There is an urgent need to identify additional diagnostic biomarkers for bovine TB to complement existing read-out systems such as interferon-gamma and for predictive markers of vaccine efficacy to accelerate vaccine development. To evaluate the potential of miRNAs as such biomarkers, we have analysed their expression in bovine PPD stimulated PBMC isolated from unvaccinated and BCG vaccinated cattle before and following Mycobacterium bovis (M. bovis) infection. Using a bovine microRNA microarray, miR-155 was found to show a significant up-regulation in expression in early (week 2) and late (week 11) M. bovis post-infection samples from unvaccinated cattle, while in BCG vaccinated cattle up-regulation was observed only in late post-infection samples. No differential expression of miR-155 was observed in pre-infection samples from unvaccinated and vaccinated cattle. These observations suggest that miR-155 could be exploited as a marker distinguishing vaccinated from infected animals (DIVA). Analysis by TaqMan RT-PCR, verified the up-regulation of miR-155 in unvaccinated cattle post-infection. Significant correlation was found between the degree of pathology and miR-155 induction in the experimentally infected cattle, suggesting miR-155 is a biomarker of disease development and/or severity. Induction of miR155 expression in cattle sourced from farms with confirmed bTB that tested positive in the tuberculin skin or interferon-gamma blood test was found to be significantly higher in cattle presenting with more advanced pathology (defined by the presence of visible TB lesions) compared to infected cattle without visible pathology and thus likely to be of lower infectivity than those with more advanced disease. In conclusion, our data indicate that miR-155 has potential both as a diagnostic and prognostic biomarker that could be used to identify animals with advanced pathology and as a DIVA test read-out. Its role in the immune biology of bovine TB will also be discussed.

The human dengue challenge experience at the Walter Reed Army Institute of Research.

Recent discordance between measured levels of serotypes of dengue virus neutralizing antibody and clinical outcomes suggests a need to reevaluate the process of prescreening dengue vaccine candidates to better predict their clinical benefit before initiation of large-scale human vaccine trials. In the absence of a reliable animal model for dengue, a human dengue virus challenge model (ie, a controlled live dengue virus infectious challenge study) may prove useful and timely to elucidate mechanisms that underlie protection (as well as virulence), thus facilitating down-selection of vaccine candidates before beginning advanced field trials. Dengue challenge studies were safely used in prior decades to study the vector biology, clinical spectrum of illness, and reactogenicity of candidate live dengue virus vaccines of uncertain attenuation. Redeveloping the human dengue challenge model following current regulatory guidance, good manufacturing practice, and good clinical practice could streamline and accelerate vaccine development by offering a time- and resource-efficient method to evaluate the safety and potential efficacy of dengue vaccine and therapeutic candidates. In this article, the development of such a challenge model and its subsequent application is summarized from 2 recent reports.

Evidence for a Role for Interleukin-17, Th17 Cells and Iron Homeostasis in Protective Immunity against Tuberculosis in Cynomolgus Macaques

Tuberculosis (TB) remains a major global public health problem. The only vaccine, BCG, gives variable protection, especially in adults, so several new vaccines are in clinical trials. There are no correlates of protective immunity to TB; therefore vaccines progress through lengthy and expensive pre-clinical assessments and human trials. Correlates of protection could act as early end-points during clinical trials, accelerating vaccine development and reducing costs. A genome-wide microarray was utilised to identify potential correlates of protection and biomarkers of disease induced post-BCG vaccination and post-Mycobacterium tuberculosis challenge in PPD-stimulated peripheral blood mononuclear cells from cynomolgus macaques where the outcome of infection was known. Gene expression post BCG-vaccination and post challenge was compared with gene expression when the animals were naïve. Differentially expressed genes were identified using a moderated T test with Benjamini Hochberg multiple testing correction. After BCG vaccination and six weeks post-M. tuberculosis challenge, up-regulation of genes related to a Th1 and Th17 response was observed in disease controllers. At post-mortem, RT-PCR revealed an up-regulation of iron regulatory genes in animals that developed TB and down-regulation of these genes in disease controllers, indicating the ability to successfully withhold iron may be important in the control of TB disease. The induction of a balanced Th1 and Th17 response, together with expression of effector cytokines, such as IFNG, IL2, IL17, IL21 and IL22, could be used as correlates of a protective host response.

Strengthening capacity for AIDS vaccine research: analysis of the Pfizer Global Health Fellows Program and the International AIDS Vaccine Initiative

BackgroundIndustry partnerships can help leverage resources to advance HIV/AIDS vaccine research, service delivery, and policy advocacy goals. This often involves capacity building for international and local non-governmental organizations (NGOs). International volunteering is increasingly being used as a capacity building strategy, yet little is known about how corporate volunteers help to improve performance of NGOs in the fight against HIV/AIDS.MethodsThis case study helps to extend our understanding by analyzing how the Pfizer Global Health Fellows (GHF) program helped develop capacity of the International AIDS Vaccine Initiative (IAVI), looking specifically at Fellowship activities in South Africa, Kenya, and Uganda. From 2005–2009, 8 Pfizer GHF worked with IAVI and local research centers to strengthen capacity to conduct and monitor vaccine trials to meet international standards and expand trial activities. Data collection for the case study included review of Fellow job descriptions, online journals, evaluation reports, and interviews with Fellows and IAVI staff. Qualitative methods were used to analyze factors which influenced the process and outcomes of capacity strengthening.ResultsFellows filled critical short-term expert staffing needs at IAVI as well as providing technical assistance and staff development activities. Capacity building included assistance in establishing operating procedures for the start-up period of research centers; training staff in Good Clinical Practice (GCP); developing monitoring capacity (staff and systems) to assure that centers are audit-ready at all times; and strategic planning for data management systems. Factors key to the success of volunteering partnerships included similarities in mission between the corporate and NGO partners, expertise and experience of Fellows, and attitudes of partner organization staff.ConclusionBy developing standard operating procedures, ensuring that monitoring and regulatory compliance systems were in place, training African investigators and community members, and engaging in other systems strengthening activities, the GHF program helped IAVI to accelerate vaccine development activities in the field, and to develop the organization’s capacity to manage change in the future. Our study suggests that a program of sustained corporate volunteering over several years may increase organizational learning and trust, leading to stronger capacity to advance and achieve NGO goals.

An overview of adjuvant formulations and delivery systems

Adjuvants may promote immune responses: by recruiting professional antigen-presenting cells (APCs) to the vaccination site, increasing the delivery of antigens to APCs, or by activating APCs to produce cytokines and by triggering T cell responses. Aluminium salts have been effective at promoting protective humoral immunity; however, they are not effective in generating cell-mediated immunity. A number of different approaches have been developed to potentiate immune response and they have been partially successful. Research has been conducted into vaccine delivery systems (VDS); enhancing cross-presentation by targeting antigens to (APCs). Antigen discovery has increased over the past decade, and consequently, it has accelerated vaccine development demanding a new generation of VDS that combines different types of adjuvants into specific formulations with greater activity. The new approaches offer a wide spectrum of opportunities in vaccine research with direct applications in the near future.

Progress in HIV-1 vaccine development.

In this review, examples of recent progress in HIV-1 vaccine research are discussed. New insights from the immune correlates analyses of the RV144 efficacy trial have accelerated vaccine development with leads to follow in nonhuman primate studies and improved vaccine designs. Several new vaccine vector approaches offer promise in the exquisite control of acute infection and in improving the breadth of T-cell responses. New targets of broadly neutralizing antibodies (BnAbs) have been elucidated, and improved understanding of how the human host controls BnAb development have emerged from BnAb knock-in mice and from analyses of BnAb maturation and virus evolution in individuals followed from the time of HIV-1 transmission to BnAb induction. Based on these observations, it is clear that the development of a successful HIV-1 vaccine will require new vaccine approaches and iterative testing of immunogens in well designed animal and human trials.

Applying Mathematical Tools to Accelerate Vaccine Development: Modeling Shigella Immune Dynamics

We establish a mathematical framework for studying immune interactions with Shigella, a bacteria that kills over one million people worldwide every year. The long-term goal of this novel approach is to inform Shigella vaccine design by elucidating which immune components and bacterial targets are crucial for establishing Shigella immunity. Our delay differential equation model focuses on antibody and B cell responses directed against antigens like lipopolysaccharide in Shigella’s outer membrane. We find that antibody-based vaccines targeting only surface antigens cannot elicit sufficient immunity for protection. Additional boosting prior to infection would require a four-orders-of-magnitude increase in antibodies to sufficiently prevent epithelial invasion. However, boosting anti-LPS B memory can confer protection, which suggests these cells may correlate with immunity. We see that IgA antibodies are slightly more effective per molecule than IgG, but more total IgA is required due to spatial functionality. An extension of the model reveals that targeting both LPS and epithelial entry proteins is a promising avenue to advance vaccine development. This paper underscores the importance of multifaceted immune targeting in creating an effective Shigella vaccine. It introduces mathematical models to the Shigella vaccine development effort and lays a foundation for joint theoretical/experimental/clinical approaches to Shigella vaccine design.

Diverse phosphorylation patterns of B cell receptor-associated signaling in naïve and memory human B cells revealed by phosphoflow, a powerful technique to study signaling at the single cell level

Following interaction with cognate antigens, B cells undergo cell activation, proliferation, and differentiation. Ligation of the B cell receptor (BCR) leads to the phosphorylation of BCR-associated signaling proteins within minutes of antigen binding, a process with profound consequences for the fate of the cells and development of effector immunity. Phosphoflow allows a rapid evaluation of various signaling pathways in complex heterogenous cell subsets. This novel technique was used in combination with multi-chromatic flow cytometry (FC) and fluorescent-cell barcoding (FCB) to study phosphorylation of BCR-associated signaling pathways in naïve and memory human B cell subsets. Proteins of the initiation (Syk), propagation (Btk, Akt), and integration (p38MAPK and Erk1/2) signaling units were studied. Switched memory (Sm) CD27+ and Sm CD27− phosphorylation patterns were similar when stimulated with anti-IgA or -IgG. In contrast, naïve and unswitched memory (Um) cells showed significant differences following IgM stimulation. Enhanced phosphorylation of Syk was observed in Um cells, suggesting a lower activation threshold. This is likely the result of higher amounts of IgM on the cell surface, higher pan-Syk levels, and enhanced susceptibility to phosphatase inhibition. All other signaling proteins evaluated also showed some degree of enhanced phosphorylation in Um cells. Furthermore, both the phospholipase C-γ2 (PLC-γ2) and phosphatidylinositol 3-kinase (PI3K) pathways were activated in Um cells, while only the PI3K pathway was activated on naïve cells. Um cells were the only ones that activated signaling pathways when stimulated with fluorescently labeled S. Typhi and S. pneumoniae. Finally, simultaneous evaluation of signaling proteins at the single cell level (multiphosphorylated cells) revealed that interaction with gram positive and negative bacteria resulted in complex and diverse signaling patterns. Phosphoflow holds great potential to accelerate vaccine development by identifying signaling profiles in good/poor responders.

Vaccines and global health

Vaccines have made a major contribution to global health in recent decades but they could do much more. In November 2011, a Royal Society discussion meeting, 'New vaccines for global health', was held in London to discuss the past contribution of vaccines to global health and to consider what more could be expected in the future. Papers presented at the meeting reviewed recent successes in the deployment of vaccines against major infections of childhood and the challenges faced in developing vaccines against some of the world's remaining major infectious diseases such as human immunodeficiency virus (HIV), malaria and tuberculosis. The important contribution that development of more effective veterinary vaccines could make to global health was also addressed. Some of the social and financial challenges to the development and deployment of new vaccines were reviewed. The latter issues were also discussed at a subsequent satellite meeting, 'Accelerating vaccine development', held at the Kavli Royal Society International Centre. Delegates at this meeting considered challenges to the more rapid development and deployment of both human and veterinary vaccines and how these might be addressed. Papers based on presentations at the discussion meeting and a summary of the main conclusions of the satellite meeting are included in this issue of Philosophical Transactions of the Royal Society B.

Accelerating vaccine development and deployment: report of a Royal Society satellite meeting.

The Royal Society convened a meeting on the 17th and 18th November 2010 to review the current ways in which vaccines are developed and deployed, and to make recommendations as to how each of these processes might be accelerated. The meeting brought together academics, industry representatives, research sponsors, regulators, government advisors and representatives of international public health agencies from a broad geographical background. Discussions were held under Chatham House rules. High-throughput screening of new vaccine antigens and candidates was seen as a driving force for vaccine discovery. Multi-stakeholder, small-scale manufacturing facilities capable of rapid production of clinical grade vaccines are currently too few and need to be expanded. In both the human and veterinary areas, there is a need for tiered regulatory standards, differentially tailored for experimental and commercial vaccines, to allow accelerated vaccine efficacy testing. Improved cross-fertilization of knowledge between industry and academia, and between human and veterinary vaccine developers, could lead to more rapid application of promising approaches and technologies to new product development. Identification of best-practices and development of checklists for product development plans and implementation programmes were seen as low-cost opportunities to shorten the timeline for vaccine progression from the laboratory bench to the people who need it.

Identification of genome-derived vaccine candidates conserved between human and mouse-adapted strains of H. pylori

Computational methods accelerate vaccine development by rapid identification of potential vaccine candidates. We screened the Helicobacter pylori J99 and 26695 genomes for T-cell epitopes using the epitope mapping algorithm EpiMatrix and selected 150 sequences for experimental validation in a pre-clinical mouse model. Because strains of H. pylori that infect humans do not generally infect mice, and the sequence of the mouse-adapted “Sydney” strain (SS1) is not publicly available, we used targeted PCR to confirm that epitopes we computationally predicted from the human H. pylori isolates J99 and 26695 are conserved in SS1. Epitopes conserved in SS1 were further analyzed for binding to MHC in vitro and for antigenicity in infected mice to select candidates for an epitope-based vaccine.

High-throughput identification of T-lymphocyte antigens from Anaplasma marginale expressed using in vitro transcription and translation

The ability to rapidly screen a complex pathogen proteome for proteins that elicit recall T-lymphocyte responses from immune individuals would accelerate vaccine development. An outer membrane fraction of the rickettsial pathogen Anaplasma marginale induces protective immunity against infection and disease in cattle. We have used this immunization model to evaluate high-throughput screening of proteins expressed by in vitro transcription and translation (IVTT) for recognition by memory CD4 + T-lymphocytes. Fifty selected vaccine candidate antigens identified from the A. marginale genome were expressed from transcriptionally active PCR products using an Escherichia coli-based IVTT system, and bead-affinity purified using antibodies to His and FLAG epitope tags. IVTT-expressed bead-bound antigens were processed and presented by antigen presenting cells to T-lymphocytes from outer membrane immunized animals and evaluated for immunogenicity in proliferation assays. Antigens that consistently stimulated responses were known T-cell antigens major surface protein (MSP)2, MSP3, VirB9, and VirB10 and newly identified T-cell antigens outer membrane protein (OMP)4, OMP9, elongation factor-Tu, Ana29, and OMA87. Specific T-cell stimulation was achieved even at low antigen concentration, and was highly sensitive when compared with unbound IVTT reaction products. This method allows rapid expression and identification of T-lymphocyte antigens for any pathogen for which the genome sequence is available.

Application of carbohydrate array technology to antigen discovery and vaccine development

Carbohydrate arrays are a new technology developed for high-throughput evaluation of interactions between carbohydrates and proteins, cells or viruses. Carbohydrate arrays contain many different carbohydrate structures on a solid support. The format allows one to probe hundreds or thousands of potential receptor–ligand interactions while using only tiny amounts of material. Recently, carbohydrate arrays have been applied to vaccine development in several ways. First, carbohydrate arrays have been utilized for the discovery and characterization of carbohydrate antigens. Second, they have been used to evaluate immune responses to vaccine candidates. Third, carbohydrate arrays have been used to identify and characterize reagents necessary for vaccine development. Although still at an early stage, carbohydrate array technology has tremendous potential for accelerating vaccine development.