Vaccine Delivery Strategies Chapter Abstracts
Chapter 1
Bacterial Polysaccharide Conjugate Vaccines
Matthias Frosch
Abstract
Bacterial polysaccharide conjugate vaccines are defined as delivery systems composed of bacterial capsular polysaccharide or lipopolysaccharide antigens, which are coupled to protein carrier molecules. The application of isolated polysaccharides results in a T-cell independent immune response, which is not boostable and elicits low-affinity IgM antibodies. Due to the immature immune system of infants, plain polysaccharides are non-immunogenic below the age of 18 months. However, by conjugation to a T-cell dependent protein carrier molecule, the polysaccharides become T-cell dependent and boostable, and protective
antibody responses are elicited even in infants. This strategy was most successfully applied for the design of a
vaccine against Haemophilus influenzae type b infections. Since the introduction of this vaccine, severe and invasive infections caused by this pathogen almost completely disappeared in those countries that included the vaccine in their national vaccination programmes. The prinicple of conjugate vaccines is currently propagated especially for the prevention against infections caused by Streptococcus pneumoniae and Neisseria meningitidis.
Chapter 2
Novel Adjuvants
Mariagrazia Pizza, Elisabetta Monaci, Derek O'Hagan and Rino Rappuoli
Abstract
The ideal vaccine has to be safe and able to induce an immune response that is strong and effective. Most of the vaccines currently available were generated a long time ago and are based on killed or live-attenuated microorganisms, or on purified antigens derived from these microorganisms. These vaccines are highly protective, but sometimes they are reactogenic. New generation vaccines, mainly based on highly purified material are safer than traditional vaccines, but are often poorly immunogenic. Therefore, the use of an adjuvant is crucial in rendering the vaccine able to induce an immune response. In the last years
considerable efforts have been directed toward the development of new and improved vaccine adjuvants. Many
new molecules have been proposed and some of them have been evaluated in clinical trials. In this chapter
we will describe the properties of some of the novel adjuvants that are promising for the development of
new vaccines. These include immunostimulatory adjuvants such as LPS derivatives, saponins,
CpG oligonucleotides, cytokines, and vaccine delivery systems such as emulsions, iscoms, liposomes,
and microparticles. Particular emphasis will be given to mucosal adjuvants such as genetically
detoxified derivatives of cholera and heat-labile enterotoxins that have significant potential for the future
development of mucosally delivered vaccines.
Chapter 3
Transcutaneous Immunization
Gregory M. Glenn
Abstract
Transcutaneous immunization (TCI) is a novel immunization strategy by which antigen and adjuvant are applied topically to induce potent antibody and cell-mediated immune responses specific for both the antigen and the adjuvant. TCI therefore combines the advantages of needle-free delivery with targeting of the immunologically rich milieu of the skin. In animal studies, this simple technique induces robust systemic and mucosal immune responses against vaccine antigens. The first clinical studies confirmed that large antigens can be delivered to the skin to induce systemic immune responses, and that the adjuvant plays
a critical role in the induction of robust responses in conjunction with delivery of antigens in a patch.
These results provide an excellent basis for further development of TCI for use in humans.
Chapter 4
Virosomes and Liposomes in Vaccinology
Rinaldo Zurbriggen
Abstract
Liposomes and virosomes have been used for the delivery of a wide range of vaccines. Liposomes are vesicular structures limited by a bilayer membrane composed of phospholipids and cholesterol and were successfully employed the delivery of subunit vaccines. Recently, a novel vaccine antigen delivery system, so-called virosomes, has been developed by incorporating the hemagglutinin from influenza virus into liposomes. This influenza virus surface glycoprotein guides the virosomes to antigen-presenting cells and leads to fusion with their endosomal membrane. This
process provides optimal processing and
presentation of the antigens to immunocompetent cells and results in the elicitation of humoral and cellular
immune responses.
Chapter 5
Enhancing DNA Vaccine Efficacy by Stress Protein-Facilitated Antigen Expression
Reinhold Schirmbeck and Jörg Reimann
Abstract
In nucleic acid-based vaccination plasmid DNA containing antigen-encoding sequences is delivered in a way, that supports in vivo expression and immunogenic presentation of the protein. DNA vaccines are attractive candidates for the specific immunotherapy of extra- and intracellular pathogens and cancer because they prime neutralizing antibody and cytotoxic T cell responses. Antigen expressed from a DNA vaccine adopts its correct three-dimensional conformation (or oligomerization), ensuring the integrity of conformational epitopes binding neutralizing antibodies. DNA vaccines stimulate T cell responses to peptides generated in (endogenous or exogenous) processing pathways (without interference by viral proteins). Currently, DNA vaccines are developed that codeliver intrinsic adjuvants to enhance and/or modulate the
immune response. We have developed a technology for the expression of heat shock protein (hsp)-bound
chimeric proteins and their immunogenic delivery as DNA-based vaccines that is described in this review. This
system illustrates the versatility of the DNA vaccination that offers exciting prospects for preclinical
(experimental) and clinical (applied) immunotherapy protocols.
Chapter 6
CpG Motifs in Vaccination
Stefan Zimmermann and Klaus Heeg
Abstract
Bacterial DNA has been recognized as pathogen associated molecular pattern (PAMP) that activates innate immune cells. Bacterial DNA differs from mammalian DNA due to the abundance of unmethylated CpG dinucleotides. This difference is sensed by innate immune cells via Toll-like receptor 9. Synthetic oligonucleotides comprising a certain DNA motif (CpG motif) mimic bacterial DNA and are immunostimulatory in vitro and in vivo. These CpG oligonucleotides are potent agents that could be used as an adjuvant to aid humoral as well as cellular immune responses. Due to its marked ability to induce interleukin (IL)-12 and IL-18, CpG DNA directs the immune response to a Th1 phenotype. Moreover, synthetic oligonucleotides are chemically and structurally well defined and can be manufactured with high
quality. These features of CpG DNA characterize it as a universal and versatile adjuvants in combination
with various antigens and delivery systems.
Chapter 7
Bacterial Ghosts as Carrier and Targeting Systems for Antigen Delivery
Wolfgang Jechlinger, Wolfgang Haidinger, Susanne Paukner, Peter Mayrhofer, Eva Riedmann, Jürgen Marchart, Ulrike Mayr, Christoph Haller, Gudrun Kohl, Petra Walcher, Pavol Kudela, Jozef Bizik, Diana Felnerova, Ewald M.B. Denner, Alexander Indra, Alexander Haslberger, Michael Szostak, Stephanie Resch, Francis Eko, Tatiana Schukovskaya, Vladimir Kutyrev, Andreas Hensel, Sonja Friederichs, Tobias Schlapp, and Werner Lubitz
Abstract
The application of new strategies to develop effective delivery vehicles is essential in modern vaccine design. The bacterial ghost system is a novel vaccine delivery system endowed with intrinsic adjuvant properties as well as carrier and targeting functions. This new platform technology improves vaccine design by facilitating the efficient delivery of target antigens to promote effective mucosal and systemic immunity.
Bacterial ghosts are non-living bacterial cells devoid of cytoplasmic contents while maintaining their
cellular morphology and native surface antigenic structures including bioadhesive properties. They are produced
by PhiX174 protein E-mediated lysis of Gram-negative bacteria. The retention by ghosts of the
morphological characteristics and structural integrity of their living counterparts make them attractive for use as
vaccines. The intrinsic adjuvant properties of bacterial ghost preparations enhance immune responses against
target antigens, including enhanced T-cell activation and mucosal immunity. Since multiple proteins can be
expressed on these ghosts in a deliberately controlled manner, high levels of the antigen or antigens can be presented
to the immune system simultaneously to produce effective combination vaccines against multiple agents.
This extended bacterial ghost system is an alternative to living bacterial delivery systems and may have an
added advantage because of its safety and flexibility. Furthermore, the specificity of ghosts for targeting
primary antigen presenting cells, the simplicity of the method of production and its versatility in entrapping
and packaging various antigens in different compartments make recombinant ghosts particularly suitable for
use as combination vaccines. The endotoxin component of the Gram-negative outer membrane does not
limit the use of ghosts as vaccine candidates because of the minimal toxicity of the
cell-associated lipopolysaccharide compared to the free soluble form.
Chapter 8
Attenuated Salmonella and Shigella Live Vectors
Myron M. Levine, James E. Galen, Eileen Barry, Marcela F. Pasetti, Carol O. Tacket, Marcelo B. Sztein,
Abstract
Attenuated strains of Salmonella enterica serovar Typhi (S. typhi) or Typhimurium (S. typhimurium) and Shigella can serve as mucosally administered live vectors that express foreign protein or polysaccharide antigens and deliver them to the immune system, eliciting protective immune responses. Multiple factors influence the immunogenicity of these bacterial vectors, including the robustness of the vector strain itself, the nature of the foreign antigen, the promoter controlling expression, gene copy number, whether the foreign antigen gene is stabilized, the site of foreign antigen accumulation and the type of immune response that is desired. Extensive studies in animal models and limited human clinical trials emphasize the importance of optimizing these parameters in order to enhance the immunogenicity of the vector construct. Attenuated strains of Salmonella and Shigella can also carry plasmids with foreign genes under control of eukaryotic expression systems (DNA vaccines) and, following mucosal administration, can deliver those plasmids to antigen presenting cells. The immune response to foreign antigens stimulated by live vectors carrying either prokaryotic or eukaryotic expression systems can be modulated by having the bacteria concomitantly carry genes encoding relevant cytokines. The extraordinary versatility of
Salmonella and Shigella live vectors makes them a promising live antigen delivery system.
Chapter 9
Use of the a-Hemolysin Secretion System (TypeI) of Escherichia coli in Vaccine Development
Ivaylo Gentschev, Guido Dietrich, Juergen Hess and Werner Goebel
Abstract
Many gram-negative bacteria use a type I secretion machinery for the translocation of proteins across the two membranes into the extracellular surroundings (e. g. pore-forming toxins, proteases, lipases and S-layer proteins). This work is a review on the application of the a-hemolysin secretion system (type I) of
Escherichia coli for development of live vaccines on the basis of attenuated bacteria.
Chapter 10
Use of Type III Secretion Systems toInduce MHC Class I-Restricted Immune Responses
Holger Rüssmann
Abstract
The chapter will focus on the use of the type III secretion system of Salmonella and Yersinia to target heterologous antigens directly to the cytosol of eukaryotic cells. Type III secretion systems are currently discovered in an increasing number of taxonomically diverse Gram-negative animal and plant pathogens. These systems are specialized for the export of bacterial virulence factors delivered directly into the cytosol of target cells to modulate host cellular functions. Certain Salmonella and Yersinia type III effector proteins with defined secretion and translocation domains can be used for delivery of large protein fragments derived from immunodominant viral and bacterial heterologous antigens into the MHC class I-restricted antigen processing pathway. In orally immunized mice, this novel vaccination strategy results in the induction of pronounced peptide-specific cytotoxic CD8 T cell responses.
Chapter 11
Live Mycobacterial Vaccine Candidates
Jürgen Hess
Abstract
Vaccination provides the most potent measure against infectious diseases and recombinant (r)-live antigen carriers expressing defined pathogen-derived proteins represent promising candidates for future vaccination trials. Novel techniques in genome manipulation allow the construction of virulence-attenuated Mycobacterium tuberculosis and r-Mycobacterium bovis Bacille Calmette-Guérin (BCG) strains that could be used as homologous vaccines or as heterologous antigen delivery systems, respectively, for priming pathogen-specific immunity against infectious diseases, including tuberculosis (TB). On the basis of recent achievements in complete genome analysis of various target-pathogens, combined with a better understanding of protective pathogen-specific immune responses, rational design of a novel mycobacterial vaccine generation against a multitude of infectious diseases has become possible.
Chapter 12
Delivery of Protein Antigens and DNA Vaccines by Listeria monocytogenes
Guido Dietrich, Ivaylo Gentschev and Werner Goebel
Abstract
In recent years, the facultative intracellular bacterium Listeria monocytogenes has been employed for the delivery of subunit vaccines. Due to its ability to gain access to the cytosol of infected host cells, L. monocytogenes is an ideally suited carrier for the introduction of protein antigens or DNA vaccines to the cytosol of professional antigen presenting cells (APC). L. monocytogenes was attenuated by the deletion of virulence genes or by the construction of auxotrophic mutant strains. Such attenuated recombinant strains of L. monocytogenes have proven to be highly suitable for the elicitation of cell-mediated immunity.
Chapter 13
Transfer of Eukaryotic Expression Plasmids to Mammalian Host Cells by Gram-negative Bacteria
Siegfried Weiss and Trinad Chakraborty
Abstract
The concept of transkingdom transfer of DNA from bacteria to other organisms has recently been extended to include eucaryotic host cells. Attenuated intracellular bacteria or non-pathogenic bacteria equipped with adhesion and invasion properties have now been demonstrated to transfer eukaryotic expression plasmids to mammalian host cells in vitro and in vivo. Here, we review the use of Gram-negative bacteria for induction of immune responses towards protein antigens encoded by the plasmid, their use to complement genetic defects or deliver immunotherapeutic proteins. Plasmid transfer is effected by bacterial death within the host cell usually resulting from metabolic attenuation. It is also possible that bacterial macromolecule
secretion machineries direct DNA transfer to the infected host cell. Plasmid transfer has been reported for
Shigella flexneri, Salmonella typhimurium and S. typhi, S. choleraesuis, Yersinia pseudotuberculosis and Escherichia coli, but clearly this property can be extended to include any bacterial species as has recently been demonstrated with Agrobacterium tumefaciens. Gene transfer in vivo attempts were mainly directed towards vaccination strategies using Shigella and Salmonella as carrier where this type of immunization was more efficacious than either direct application of antigen, using the same bacterium as a heterologous carrier expressing the antigen via a prokaryotic promoter, or vaccination with naked DNA. The efficacy of induction of protective immune responses by such DNA carriers and ease of generating these vehicles for gene transfer using technology validated for mass vaccination programs makes this a highly attractive area for further
research and development.
Chapter 14
Recombinant Intra-cellular Bacteria as Carriers for Tumor Antigens
George R. Gunn, III, Abba C. Zubair and Yvonne Paterson
Abstract
It is about 100 years since William Coley first used bacteria as non-specific stimulators of the immune system for tumor therapy. With the discovery of antigens associated with tumors to which a specific immune response can be directed, bacteria can now be engineered to target antigens to the immune system in addition to providing adjuvant properties. Intra-cellular bacteria are particularly attractive candidate vectors of this class of antigens because of their ability to induce strong cell mediated immunity that can target tumor cells regardless of the cytosolic localization of the tumor antigen. In addition the propensity of
intra-cellular bacteria to infect phagocytic cells aids delivery of the antigens directly to professional antigen
presenting cells, which express co-stimulatory molecules and stimulate efficient priming of a T cell response. In
addition bacteria may be safer vectors for tumor antigens than viral vectors because of the wide spectrum of
antibiotics to which they are susceptible in the event of unforeseen susceptibility by the patient. The potent
Th1-type immune response induced by intra-cellular bacteria, the readily available genetic tools to manipulate
the bacteria's phenotype and the potential safety advantages inherent in bacteria provide the rationale
for investigating them as potential vaccine vectors for targeting tumor antigens. Here we will review the
history and recent use of three intra-cellular bacterial vectors,
Listeria monocytogenes, Salmonella typhimurium and the BCG vaccine strain of Mycobacterium bovis.
Chapter 15
Dendritic Cell-Based Vaccination against Tumors and Infectious Diseases
Christof Berberich, Wolfgang Strittmatter and Heidrun Moll
Abstract
Recent insights into the pivotal functions of dendritic cells (DCs) for the initiation and regulation of immune responses have provided the basis to design DC-based cellular vaccines for immune interventions against tumors and infectious diseases. Data collected from pre-clinical and clinical studies document that DC-based vaccination protocols can induce high levels of protective immunity and may exhibit immunotherapeutical potential. Although some obstacles to this novel approach must still be overcome, the development of methods to generate large numbers of DCs from precursor cells has paved the way for
their clinical applications.
Chapter 16
Edible Vaccines
Jie Yu, James E. Carter and William H.R. Langridge
Abstract
Advances in plant molecular biology over the past two decades have resulted in the expression of foreign genes in an increasing variety of plant species. Transgenic plants expressing recombinant proteins are becoming more effective production systems for vaccines. Inoculation with edible plants producing pathogen and self proteins has shown promising results for protective immunization against infectious diseases and induction of immune tolerance against autoimmune diseases. Ease of administration and the reduced cost of vaccine production provided by recombinant plant technology may soon enable a global
immunization program.
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