Cover Page

Contents

Title Page

List of Contributors

Murrium Ahmad, PhD

The John van Geest Cancer Research Centre, School of Science and Technology, Nottingham Trent University, Nottingham, UK

Sir Roy M. Anderson, FRS, FMedSci

Chair in Infectious Disease Epidemiology

Division of Epidemiology, Public Health and Primary Care, School of Public Health, London, UK

Antony N. Antoniou, PhD

Senior Research Fellow Department of Infection and Immunity/Centre of Rheumatology, University College London, London, UK

Victor Appay

INSERM UMR S 945, Infections and Immunity, Avenir Group, Université Pierre et Marie Curie (UPMC), Sorbonne Universités, and Hôpital Pitié-Salpétrière, Paris, France

Carolina Arancibia-Cárcamo, PhD

Translational Gastroenterology Unit, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK

Helen S. Atkins, BSc, PhD

Department of Biomedical Sciences, Defence Science and Technology Laboratory, Porton Down, UK

R. Bruce Aylward, MD, MPH

Assistant Director-General, Polio, Emergencies and Country Collaboration, World Health Organization, Geneva, Switzerland

Lorne A. Babiuk, OC, SOM, PhD, DSc, FRSC

Office of Vice President Research, University of Alberta, Edmonton, Canada

Graham Ball

The John van Geest Cancer Research Centre, School of Science and Technology, Nottingham Trent University, and CompanDX Ltd, Nottingham, UK

Janine Bilsborough, PhD

Inflammation Research, Amgen, Thousand Oaks, CA, USA

Marie-Claude Boily, PhD

Senior Lecturer in Infectious Disease Ecology

Division of Epidemiology, Public Health and Primary Care, School of Public Health, London, UK

Diane L. Bolton

Vaccine Research Center, National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH), Bethesda, MD, USA

Catharine M. Bosio, PhD

Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT, USA

Marc Brisson, PhD

Unité de Recherche en Santé des Populations, Centre de Recherche Fonds de la Recherche en Santé du Québec du Centre Hospitalier affilié Universitaire de Québec, Canada

Victoria Byers

NJM European Economic & Management Consultants Ltd, Gosforth, Newcastle Upon Tyne, UK

Claudio Carini, MD, PhD

Boston Biotech Clinical Research, Cambridge, MA, USA

Miles W. Carroll, PhD

Microbiology Division, Health Protection Agency, Porton Down, UK

Darrick Carter, PhD

Protein Advances, Inc., Seattle, WA, and Infectious Disease Research Institute, Seattle, WA, USA

Bryce Chackerian, PhD

Department of Molecular Genetics and Microbiology, University of New Mexico School of Medicine, Albuquerque, NM, USA

Dipshikha Chakravortty, PhD

Department of Microbiology and Cell Biology, Center for Infectious Disease Research and Biosafety Laboratories, Indian Institute of Science, Bangalore, India

Robert T. Chen, MD, MA 

Division of HIV/AIDS Prevention, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention (CDC), Atlanta, GA, USA

Zhengrong Cui

Pharmaceutics Division, College of Pharmacy, University of Texas-Austin, Austin, USA

Julie M. Curtsinger, PhD

Department of Laboratory Medicine & Pathology, Center for Immunology, University of Minnesota, Minneapolis, MN, USA

Priyanka Das

Department of Microbiology and Cell Biology, Center for Infectious Disease Research and Biosafety Laboratories, Indian Institute of Science, Bangalore, India

Nelson Cesar Di Paolo, PhD

Department of Medicine, Division of Medical Genetics, University of Washington, Seattle, WA, USA

Candida Fratazzi, MD

Boston Biotech Clinical Research, Cambridge, MA, USA

Volker Gerdts, DVM

Vaccine & Infectious Disease Organization, Saskatoon; Department of Veterinary Microbiology, University of Saskatchewan, Saskatoon, SK, Canada

Jane Gidudu MD, MPH

Immunization Safety Office, Division of Healthcare Quality Promotion, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention (CDC), Atlanta, GA, USA

Gregory M. Glenn

Intercell USA, Inc., Gaithersburg, MD, USA

David B. Guiliano

Division of Infection and Immunity/Centre for Rheumatology, Windeyer Institute of Medical Science, University College London, London, UK

Patrick Guirnalda, PhD

Department of Microbiology, University of Pennsylvania, Philadelphia, PA, USA

Yper Hall, BSc

Microbiology Division, Health Protection Agency, Porton Down, UK

David L. Heymann, MD, DTM&H

Professor and Chair, Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, UK

Maria Candela Iglesias

INSERM UMR S 945, Infections and Immunity, Avenir Group, Université Pierre et Marie Curie (UPMC), Sorbonne Universités, and Hôpital Pitié-Salpétrière, Paris, France

John Iskander, MD, MPH

Office of the Associate Director for Science, Centers for Disease Control and Prevention (CDC), Atlanta, GA, USA

Camilla Jandus, MD, PhD

Division of Clinical Onco-Immunology, Ludwig Institute for Cancer Research, Lausanne, Switzerland

Sylvia Janetzki, MD

Zellnet Consulting, Inc., Fort Lee, NJ, USA

Ross M. Kedl, PhD

Department of Immunology, University of Colorado Denver, Denver, CO, USA

Amit Lahiri

Department of Microbiology and Cell Biology, Center for Infectious Disease Research and Biosafety Laboratories, Indian Institute of Science, Bangalore, India

Stephen M. Laidlaw

Department of Virology, Imperial College London Faculty of Medicine, London, UK

Yvette Latchman, PhD

The Puget Sound Blood Center, Seattle, WA, USA

Ed C. Lavelle, PhD

Adjuvant Research Group, School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College, Dublin, Ireland

Stephanie Laversin

The John van Geest Cancer Research Centre, School of Science and Technology, Nottingham Trent University, Nottingham, UK

F. Eun-Hyung Lee, MD

Emory University Department of Medicine, Division of Pulmonary, Allergy, and Critical Care Medicine, Atlanta, GA, USA

Izabela Lenart

Division of Infection and Immunity/Centre for Rheumatology, Windeyer Institute of Medical Science, University College London, London, UK

André Lieber, MD, PhD

Department of Medicine, Division of Medical Genetics, and Department of Pathology, University of Washington, Seattle, WA, USA

Margaret A. Liu, MD

ProTherImmune, Lafayette, CA, USA

Amit A. Lugade, PhD

Department of Immunology, Roswell Park Cancer Institute, Buffalo, NY, USA

Megan MacLeod, PhD

Integrated Department of Immunology, Howard Hughes Medical Institute, National Jewish Health, Denver, CO, USA

Philippa Marrack, PhD

Integrated Department of Immunology, Howard Hughes Medical Institute, National Jewish Health, Denver, CO, USA

Preston A. Marx Jr, PhD

Tulane National Primate Research Center, Tulane University, Covington, LA, USA

Matthew F. Mescher, PhD

Department of Laboratory Medicine & Pathology, Center for Immunology, University of Minnesota, Minneapolis, MN, USA

Benoit Mâsse, PhD

Public Health Sciences Division, Biostatistics, Fred Hutchinson Cancer Research Center, Seattle, Washington, USA

Arnaud Moris

INSERM UMR S 945, Infections and Immunity, Avenir Group, Université Pierre et Marie Curie (UPMC), Sorbonne Universités, and Hôpital Pitié-Salpétrière, Paris, France

Cliff Murray, PhD

Source BioScience, Nottingham, UK

George K. Mutwiri, DVM, PhD

Vaccine & Infectious Disease Organization, Saskatoon; School of Public Health, University of Saskatchewan, Saskatoon, SK, Canada

Scott Napper, PhD

Vaccine & Infectious Disease Organization, Saskatoon; Department of Biochemistry, University of Saskatchewan, Saskatoon, SK, Canada

Derek T. O’Hagan, PhD

Global Head, Vaccine Delivery and Formulation, Novartis Vaccines and Diagnostics, Inc., Cambridge, MA, USA

Yvonne Paterson, PhD

Department of Microbiology, University of Pennsylvania, Philadelphia, PA, USA

Andrew A. Potter, PhD, FCAHS

Vaccine & Infectious Disease Organization, Saskatoon; Department of Veterinary Microbiology, University of Saskatchewan, Saskatoon, SK, Canada

Simon J. Powis, PhD

School of Medicine, University of St Andrews, St Andrews, Fife, UK

Robert Rees

The John van Geest Cancer Research Centre, School of Science and Technology, Nottingham Trent University, Nottingham, and CompandX Ltd, Nottingham, UK

Mario Roederer, PhD

Vaccine Research Center, National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH), Bethesda, MD, USA

Pedro Romero

Division of Clinical Onco-Immunology, Ludwig Institute for Cancer Research, Lausanne, Switzerland

Iñaki Sanz, MD

Division of Allergy, Immunology, and Rheumatology, University of Rochester Medical Center, Rochester, NY, USA

Aaron K. Sato, PhD

OncoMed Pharmaceuticals, Redwood City, CA, USA

John T. Schiller, PhD

Laboratory of Cellular Oncology, National Cancer Institute, Bethesda, MD, USA

Matthew Seavey, PhD

Department of Microbiology, University of Pennsylvania, Philadelphia, PA, USA

Robert C. Seid Jr

Intercell USA, Inc., Gaithersburg, MD, USA

Fiona A. Sharp, PhD

Fahmy Research Group, Department of Biomedical Engineering, School of Engineering and Applied Science, Yale University, New Haven, CT, USA

Dmitry Shayakhmetov, PhD

Department of Medicine, Division of Medical Genetics, University of Washington, Seattle, WA, USA

Michael A. Skinner

Department of Virology, Imperial College London Faculty of Medicine, London, UK

Brian R. Sloat

Pharmaceutics Division, College of Pharmacy, University of Texas-Austin, Austin, USA

Kalathil Suresh, PhD

Department of Immunology, Roswell Park Cancer Institute, Buffalo, NY, USA

Rudolf H. Tangermann, MD

Global Polio Eradication Initiative, World Health Organization, Geneva, Switzerland

Yasmin Thanavala, PhD

Department of Immunology, Roswell Park Cancer Institute, Buffalo, NY, USA

Richard W. Titball, BSc, PhD, DSc, FRCPath

School of Biosciences, University of Exeter, Exeter, UK

Hugh Townsend, DVM, MSc

Vaccine & Infectious Disease Organization, Saskatoon; Department of Large Animal Clinical Sciences, University of Saskatchewan, Saskatoon, SK, Canada

Hoi K. Tran

Department of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, OR, USA

Sylvia van Drunen Littel-van den Hurk, PhD

Vaccine & Infectious Disease Organization, Saskatoon; Department of Microbiology and Immunology, University of Saskatchewan, Saskatoon, SK, Canada

Claudia Vellozzi, MD, MPH

Division of Healthcare Quality Promotion, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention (CDC), Atlanta, GA, USA

Joanne L. Viney, PhD

Inflammation Research, Amgen, Thousand Oaks, CA, USA

Alexander F. Voevodin, MD, PhD, DSc, FRCPath

Vir&Gen, Toronto, ON, Canada

Andreas Wack

Division of Immunoregulation, National Institute for Medical Research, London, UK

Britta Wahren, MD, PhD

Department of Virology, Karolinska Institutet and Swedish Institute for Infectious Disease Control, Stockholm, Sweden

Heather L. Wilson, PhD

Vaccine & Infectious Disease Organization, Saskatoon; Department of Biochemistry, University of Saskatchewan, Saskatoon, SK, Canada

Peter Wilson, PhD, MBA, LLB

NJM European Economic & Management Consultants Ltd, Gosforth, Newcastle Upon Tyne, UK

Laurence Wood, PhD

Department of Microbiology, University of Pennsylvania, Philadelphia, PA, USA

Preface

“Vaccinology” is a term that encompasses the whole process of producing vaccines – from basic research and preclinical demonstration of efficacy, to approval and clinical trial in humans. While there are many excellent books that detail the various steps, such as antigen discovery or delivery systems, there are fewer that also cover so called “downstream development,” such as the design of clinical trials, or their regulation in the United States and the European Union. In this book we have aimed to fill this gap by providing the reader with a comprehensive and authoritative reference that describes the design and construction of vaccines from first principles to implementation. We hope it will appeal both to scientists engaged in vaccine research and development, and to clinicians, or indeed anyone, with an interest in the opportunities and challenges facing the development of new vaccines.

To tackle this vast subject we have organized the chapters into sections. We start with an examination of the concept and scope of modern vaccines. We follow this with the basic tenets of the immune system that govern our thinking about vaccines, with chapters on innate immunity, antigen processing and presentation, mucosal immunity, immunological memory in T and B cells, and the utility of mouse and nonhuman primate models for testing vaccine efficacy. In the following section we explore antigen discovery in the postgenomic era, during which there has been remarkable progress in proteomic mining for potential vaccine antigens, and powerful predictive algorithms and high-throughput assay and display technologies. Together these offer unprecedented opportunities for the rapid development of new vaccines. This is then followed by a selection of chapters on antigen engineering and delivery: attenuated microbe vaccines, virus-like particles, recombinant viruses (orthopox, avipox, lentivirus, and adenovirus) and bacteria, DNA vaccines, and artificial cells. In parallel we explore methods for antigen delivery, with chapters on transcutaneous vaccination, needle-free jet delivery, and oral vaccines. The need to potentiate otherwise inert proteins is the subject of the next section, with chapters on designing adjuvants, particulate delivery systems such as PLGs and microspheres, co-administration of co-stimulatory moieties, and the role of TLR signaling in adjuvanticity. We then transition from basic research to vaccine implementation. The first of these sections discusses regulatory considerations, with chapters on working with the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA), developmental pipelines, the design of clinical trials, immune monitoring and biomarkers, and vaccine safety. This is followed by chapters on mass immunization strategies, and mathematical models and epidemiological monitoring.

This book would not be possible without the impressive array of experts who have contributed chapters. We wish to thank every one of you for making this possible and bearing with us on this ambitious project. Finally we wish to thank the production team at John Wiley, especially Julie Elliott, Maria Khan, and Michael Bevan. This has been a team effort, but ultimately any omissions or errors are the responsibility of the editors. We welcome comments and feedback for future editions of this book.

W. John W. Morrow
Nadeem A. Sheikh
Clint S. Schmidt
D. Huw Davies

PART 1

Introduction

CHAPTER 1

Concept and Scope of Modern Vaccines

D. Huw Davies1, Clint S. Schmidt2, & Nadeem A. Sheikh3

1School of Medicine, University of California at Irvine, Irvine CA, USA
2NovaDigm Therapeutics, Inc., Grand Forks, ND, USA
3Clinical Immunology, Research, Dendreon Corporation, Seattle, WA, USA

Introduction

Historically, vaccination has probably had the greatest impact on human health of any medical intervention technique. Immunization is the only cost effective solution that can arrest and even eradicate infectious diseases. The science of vaccinology can be traced to the ancient Chinese, who protected against smallpox by the process of variolation, in which small quantities of scabs from a lesion of an infected person were intranasally inoculated [1]. This process was revived in the early 18th century when Lady Mary Montagu, who had observed variolation being practiced in Turkey, advocated its use to prevent smallpox. Modern vaccinology started as a proper scientific endeavor by Edward Jenner's findings that cowpox pustules would prevent smallpox infection [2]. His work was the first to be evaluated scientifically and established the scientific basis for using a related but less dangerous pathogen to engender immune responses that are cross-protective against the more virulent pathogen [3]. The seminal work and findings of Jenner lay unexploited for nearly a century until Louis Pasteur demonstrated that chickens could be protected from cholera by inoculation with attenuated bacteria [4]. Similar experiments also showed that sheep could be protected from anthrax [5]. This concept of weakening a pathogen to invoke the immune system to produce a response forms the basis of immunity elicited by the Bacille Calmette-Guérin (BCG) tuberculosis vaccine, first administered in 1921 [6] and still in wide use today.

Vaccines are defined as immunogenic preparations of a pathogen that evoke an immune response without causing disease. While attenuation and inactivation of pathogens are conventional approaches, and are still used, modern vaccines also exploit recent developments in immunology, genomics, bioinformatics, and structural and protein chemistry. At the heart of all vaccines is antigen – the ligand of the receptors of T and B lymphocytes. Lymphocytes are the effector cells of the adaptive immune system that mediate immunologic memory responses – the very hallmark of vaccination – which set vaccination apart from other forms of modern immune system manipulation, such as broad-spectrum immunopotentiators, cytokine therapy, or passive transfer of specific hyperimmune globulins derived from human plasma.

Incidence of disease and the year of peak rate in the USA prior to and after mass immunization programs were initiated.

Table 1-1

The scope of modern and future vaccines has widened considerably since the empirical approaches of the pre-genomic era. Vaccines can now be designed rationally, even customized to individual needs. Developments in many areas of vaccinology, from adjuvants, proteomics, expression library immunizations (ELI), and sub-unit vaccines, to innovative funding and philanthropy, continue to reach new milestones. However, there are challenges in the road ahead. The vaccines that have not yet been made either exceed the limits of current technology or there is a lack of incentive. Here we outline the limitations of current vaccine technology and, through the following chapters, identify technologies that may help the field of vaccinology to advance.

Triumphs and limitations of current vaccination

After access to affordable nutrition, clean drinking water, and sanitation, low cost vaccines are the single most cost effective healthcare measure that can be taken to protect human health. This is highlighted by the fact that mass immunization programs have directly resulted in the control of several infectious diseases. For example, rates of incidence of diphtheria, measles, mumps, pertussis, and a number of other common diseases have been reduced by over 99% in the United States (). In the case of smallpox, global eradication was achieved through a concerted effort led by the World Health Organization (WHO). For polio, a concerted eradication program has reduced the incidence year after year from approximately 35 000 cases annually to fewer than 4000 in 1996 (). Similarly, as the number of immunizations against measles has risen over the past two decades, the number of reported measles infections has fallen ().

Impact of polio eradication program upon cases of polio infection worldwide. Each year there has been a gradual decrease in the numbers of polio cases reported. Adapted from Vaccine & Immunization News No. 5, 1997 (WHO Publications).

nc01f001.eps

Impact of measles eradication program upon cases of measles infection worldwide. Shaded bars, coverage; line, number of deaths. Each year there has been a gradual decrease in the numbers of deaths due to measles. Adapted from Vaccine & Immunization News No. 4, 1997 (WHO Publications).

nc01f002.eps

In addition, by controlling infections, vaccines reduce expenditure on future treatment (). Such costs are highlighted by the Centers for Disease Control (CDC) [8], which estimates that for every dollar invested in immunization, between $2 and $29 are saved. In addition the entire cost of the global smallpox eradication program, approximately $32 million, is returned every 20 days in not having to vaccinate travelers. A specific case in point is made by the combined measles, mumps, and rubella (MMR) vaccine. Immunization with this combined MMR vaccine was estimated to provide $5.1 billion direct and indirect cost savings in the USA for 1992 alone [9].

Cost effectiveness of childhood vaccines in the United States and the estimated returned savings, both direct and indirect, from vaccination.

Savings per “vaccine dollar” invested
Vaccine Direct medical savings Direct and indirect savings
DTP $6.0 $29.1
MMR $15.3 $21.3
OPV $3.4 $6.1
Integrated (DTP, MMR, OPV) $7.4 $25.5
Haemophilus influenza type b $1.4 $2.2
Hepatitis B (perinatal/infant) $0.5 $2.0
Varicella $0.9 $5.4
DTP, diphtheria, tetanus, pertussis; MMR, measles, mumps, rubella; OPV, oral polio vaccine.
Data from National Immunization Program, Centers for Disease Control and Prevention.

Despite the impact of vaccines on childhood infectious diseases such as measles, diphtheria, polio, and meningitis, there are many infectious diseases that continue to thwart vaccination programs, particularly in resource-poor countries, such as malaria, salmonellosis, and tuberculosis. There are several reasons why we lack vaccines to these diseases:

Modern approaches that impact vaccine design

Genomics

In the pre-genomic era, vaccines were made from animal pathogens, or human pathogens either attenuated by abnormal growth conditions or killed by chemical inactivation. Many successful vaccines were developed using this empirical approach. This gave way to extracts of pathogens – or subunit vaccines – where components of the pathogen were used in place of the whole organism. In the post-genomic era, the production of subunit vaccines has become more rational and the preparations of antigens more precisely controlled. Despite their drawbacks, recombinant protein vaccines have had, and will continue to have, a major impact on diseases caused by simple pathogens, especially viruses, where a single antigen is often enough to provide immunity (e.g., human papilloma virus, HPV). Even for more complex pathogens such as bacteria and parasites, there is still the expectation that recombinant protein vaccines can provide protection, particularly if adjuvanted cocktails of protective antigens are used. Continued progress in this area has been hampered by the identification of candidate antigens. The problem has been the sheer size of the genome and the number of potential antigens available, and until recently the discovery of potential subunit vaccine antigens have been piecemeal and non-systematic.

Modern high throughput approaches to proteome-wide expression and screening technologies promise to revolutionize the discovery of new vaccine antigens for old diseases. A recent antibody profiling study of acquired immunity to malaria in the Gambia, for example, identified antibodies to several antigens present in children with acquired immunity that are absent from children who were still undergoing seasonal bouts of malaria [10]. These antigens would be considered prime targets for vaccine development. Importantly, the same study revealed the antigens currently being evaluated in clinical trials were not among these discriminatory antigens. The conclusion from studies like this is that non-biased screening approaches may lead to the discovery of different antigen sets than conventional “intuitive” approaches. It remains to be determined whether these new antigens lead to better vaccines, and Part 3 of this book focuses on these new tech-nologies.

Improved delivery systems and adjuvants

Recombinant proteins are, for the most part, poorly immunogenic and require delivery in an immunogenic package. The most successful delivery systems for recombinant proteins are often based on macromolecular assembles of one sort or another, and can take the form of immune stimulating complexes (ISCOMs), liposomes, or virus-like particles. Suspensions of antigen bound to inorganic particles such as alum are also immunogenic. It seems dendritic cells are particularly efficient at ingesting and responding to insoluble, particulate antigens, but less so to soluble proteins.

Other steps can be taken to improve the immunogenicity of existing vaccines. For example, peptide vaccines suffer from short half life in vivo, which can be improved by chemical modification to improve stability. Nucleic acid vaccines, although showing great promise in animal models, currently have had less developmental success in humans. The reasons are still unclear but their efficacy can be improved by using live vectors to boost them. The immunogenicity of recombinant vectors such as vaccinia or adenovirus is blunted by pre-existing immunity. This can be overcome by using animal viruses as vectors, such as fowlpox, where pre-existing immunity does not exist. These examples and other antigen engineering technologies are examined in Part 4.

Therapeutic vaccination

Currently none of the licensed traditional vaccines for use in humans are therapeutic, but instead are prophylactic and depend on antibodies to block initial infection. A vaccine administered after infection in order to treat (not prevent) disease is a realistic goal of modern vaccination. Once a pathogen has established an infection, the type of immune response required to eliminate the infection depends largely on whether the pathogen remains extracellular or gains entry into cells, where it becomes inaccessible to antibody. The optimism for therapeutic vaccines comes from great strides in the 1980s and 1990s in understanding T-cell recognition and antigen processing/presentation, and the realization that vaccines specifically targeting cell-mediated immunity could engender protection against pathogens that reside within cells. Both CD8 and CD4 T cells can mediate killing of cells harboring intracellular pathogens, particularly viruses (CD8) and bacteria that reside in endosomal compartments (CD4). Many model systems in animals have shown proof-of-principle of therapeutic vaccination. The bottleneck to translating this to vaccine development is, as with antibody vaccines, the size of the pathogen genome. Uniquely with T cells, the problem is amplified if synthetic peptides are desired for vaccination. Again, high throughput proteomic screening platforms and ever improving predictive algorithms promise to define the antigens needed, while carefully selected delivery vehicles or adjuvants will ensure the correct T cell subset(s) is stimulated.

Although the field of therapeutic vaccination is still developing for infectious disease, some promising inroads have been made in the cancer immunotherapy field. These technologies are based on the ex vivo activation [11] and amplification of the specific cellular immune response, followed by re-infusion of immune cells to the patient, as opposed to the in vivo activation hopefully achieved by traditional vaccines. The oncology targets for this approach are many. However, the field is gaining momentum with the FDA approval of Dendreon Corporation's Provenge™ (sipuleucel-T) for asymptomatic, or minimally symptomatic metastatic, androgen-independent prostate adenocarcinoma [12].

A return to attenuated organisms?

With the notable exception of toxoids, the disappointing previous performances of single recombinant protein subunit vaccines against complex pathogens (bacteria, fungi, and parasites) compel us to continue the development of live attenuated vaccines alongside subunit vaccine development, to ensure the highest probability of discovering a successful vaccine against any particular pathogen. Live attenuated vaccines have many advantages over killed or subunit vaccines, although the safety requirements are more stringent owing to the risk of reversion to a pathogenic phenotype. Attenuated live bacterial vaccines currently licensed for human use include Mycobacterium bovis strain Bacille Calmette-Guérin (developed in the 1920s), Salmonella typhi Ty21a (1970s), and Vibrio cholerae CVD 103-HgR (1980s) [13]. The latter was derived by site-directed mutagenesis of the cholera toxin A gene (ctxA), and in some respects it represents the flipside of the traditional cholera toxoid vaccine. Although “low hanging fruit” for an attenuated vaccine, it points toward the rational way in which such vaccines may be made in the future. For most bacteria, multiple virulence factors are linked to pathogenesis. Traditional approaches to attenuation, such as forced adaptation to unusual culture conditions or radiation/chemical mutagenesis, are too “hit and miss” for modern rational approaches. With increasingly rapid annotation of sequenced pathogens comes the potential for systematic identification of virulence factors and their targeting for mutagenesis or deletion. Technologies for screening large numbers of mutants for attenuation and immunogenicity need to be developed, and will likely involve in vitro models.

Allied to this are vaccines based on animal pathogens – the “Jennerian” approach. The smallpox vaccine is often described as the prototype of all vaccines, and the only vaccine to have approached the eradication of a human disease. The principle of the original smallpox vaccine (which was cowpox) is somewhat different to the attenuated and killed vaccines that have followed. Cowpox is not an attenuated version of the human pathogen, but a closely related, less pathogenic, species of orthopoxvirus. The origins of vaccinia are not clear but modern phylogenetic analyses indicate it is a “domesticated” version of cowpox. Although vaccines based on animal pathogens are less pathogenic, attenuated strains are preferable. Replication-competent smallpox vaccines are being replaced by attenuated vaccinia strains such as MVA. The attenuated Mycobacterium bovis strain BCG, first produced as a vaccine against M. tuberculosis in the 1920s, also works on this Jennerian principle. More recent examples include the human-animal “reassortant” rotavirus vaccines that have been developed using animal rotaviruses engineered to contain antigens from the human rotavirus [14].

Improve existing vaccines and vaccine uptake

Most attenuated live organisms have limited efficacy, in part because the attenuation is so severe. Attempts to improve existing vaccines, such as with more potent adjuvants or adjuvant combinations, or improved manufacturing methods, is therefore another approach upon which modern technologies can be brought to bear. Basic research in immunologic processes will undoubtedly continue to reveal novel approaches to improving the immunogenicity of existing vaccines. The discovery of the role of Toll-like receptors [15,16] and the application of contemporary immunologic techniques [17] have helped our understanding of the basis of adjuvanticity. Likewise, our understanding of antigen processing pathways and different regulatory and effector T cell subsets has revealed the importance of antigen delivery in the type of immune response elicited. In the future, immunomodulators that switch off suppressive pathways and promote proinflammatory pathways, or ligands that target antigens to specific cells and tissues of the immune system, may be routinely engineered into vaccines. It is likely that our understanding of other critical processes, such as immunologic memory and immunodominance, will also become clearer in the near future and influence our design of vaccines and the adjuvants used.

It is worth remembering we do not need to discover new vaccines to make an impact on global health. The WHO estimates that 2.7 million children die annually from diseases that could be prevented with existing vaccines, almost half of which are caused by rotavirus and Streptococcus pneumoniae [18]. The majority of these are in resource-poor countries. The WHO's Expanded Programme on Immunization (EPI), first introduced in 1974, aims to bring vaccination to children throughout the world. The scheme was recently expanded to cover the world's poorest nations through the Global Alliance for Vaccines and Immunisation (GAVI) (). Complacency and misinformation are problems in developing countries, and threaten to undermine vaccine-induced protection. Simply because a disease is no longer as common as it once was creates the illusion it is eradicated, allowing re-emergence if vaccination is not maintained. Clearly, mandatory childhood vaccination is important but remains essentially optional in most countries. Regardless of whether or not one believes there is a role for the MMR vaccine in the development of autism, the reduction in uptake of the MMR vaccine in response to the recent hysteria had a direct effect on the rise in cases of childhood measles [19].

Hurdles and challenges for the future

Non-infectious diseases as targets for modern vaccines

The identification of autoantigens associated specifically with cancer and autoimmune disease has opened up new opportunities for vaccination. These are predominantly “therapeutic” T cell-based vaccines administered to individuals who already have disease. This considerably extends the concept of a “vaccine” beyond the traditional immunogenic preparation of a pathogenic microorganism, and indeed the recently approved HPV vaccines are a significant advance in the prophylactic vaccination against a virus-associated cancer [20].

Transition from research to trial

The pages of vaccine journals (and indeed this very book) are full of novel and ingenious vaccines, delivery systems, adjuvants, vectors, and scientific methods. Yet only the simplest and safest vaccines are ever considered for clinical trial. The realities of obtaining necessary approvals, producing a vaccine to current good manufacturing practice (cGMP) standards, and finding funding are far removed from most academic laboratories where basic vaccine research is conducted. Even if a candidate is evaluated in Phase I or II clinical studies, the investment required to enter Phase III trial is beyond the scope of most government funding agencies and requires the involvement of industry. For example, it is estimated that the research and development costs of bringing Gardisil™, an HPV vaccine comprising four recombinant proteins, to market was in excess of $1 billion. There have been several attempts to overcome the economic barrier against the development of less lucrative vaccines and diagnostics, such as with tax incentives and guaranteed government purchases. Additionally, non-profit organizations, such as the Wellcome Trust, and more recently the Bill & Melinda Gates Foundation, have become pivotal drivers for vaccine development. Thus, with the cooperation between scientific, industrial, non-profit, and political entities, the field of vaccinology will continue to advance, meeting the world's unmet medical needs.

References

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2 Jenner E. On the Origin of the Vaccine Inoculation. Printed by D. N. Shury, London, 1801.

3 Jenner E. An inquiry into the causes and effects of the variolae vaccinae, a disease discovered in some of the western counties of England, particularly Gloucestershire, and known by the name of the cow pox, London 1798. In CNB Camac (Ed.) Classics of Medicine and Surgery. Dover Press, London, 1959, pp. 213–40.

4 Pasteur L, Chamberland CE, Roux E. Sur la vaccination charbonneuse. CR Acad Sci Paris 1881;92:1378–83.

5 Pasteur L. Une statistique au sujet de la vaccination préventive contre le charbon portant sur quatre-vingt-cinq-mille animaux. CR Acad Sci Paris 1882;95:1250–52.

6 Calmette A. La Vaccination préventive contre la tuberculose par le BCG. Masson, Paris, 1927.

7 Saldarini RJ. For vaccines, the future is now. Nat Med 1998;4:485–91.

8 Bloom BR, Widdus R. Vaccine visions and their global impact. Nat Med 1998;4:480–84.

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PART 2

Principles of Vaccine Design