- Email: [email protected]
Live Salmonella as vaccines and carriers of heterologous antigens to the mammalian immune system
Conference Abstracts
Live Salmonella as vaccines and carriers of heterologous antigens to the mammalian immune system Steve Chatfield Medeva Group Research Ltd. Vaccine Research Unit, Wellcome Research Laboratories, South Eden Park Road, Beckenham, Kent, UK Salmonella species can be rationally attenuated by introducing non-reverting defined mutations into the chromosome to produce live oral vaccine strains. Several genes have been identified which when mutated will attenuate Salmonellae. In particular salmonella strains harbouring mutations in genes involved in the pre-chorismate biosynthetic pathway make excellent oral vaccines evoking strong humoral, local and cellular immune responses in the host. Because of the spectrum of immune responses induced by live vaccine strains they have the potential to be used for delivery of heterologous antigens to
the mammalian immune system. A number of other antigens from other bacteria, viruses and parasites have been expressed in live Salmonella strains. Such hybrid strains have the potential to be used as multivalent vaccines against a number of infectious diseases. In particular we have constructed a candidate oral typhoid vaccine based on an attenuated Salmonella typhi strain expressing fragment C, a C terminal non-toxic protein of tetanus toxin. It is hoped that such bivalent strains may offer important advances against such infectious diseases.
Oral vaccination of mice with Lactobacillus-immunogenconjugates Wim J.A. Boersma, Koen Gerritse, Marijke Kottenhage, Mark Posno and Eric Claassen TNO Medical Biological Laboratory, POB 45, 2280 AA, Rijswijk, The Netherlands Ideally, vaccines should be given orally, as this route of administration is convenient and inexpensive. However, oral immunization is generally inefficient in generating systemic antibody responses and it requires large quantities of the immunogen. On the other hand, oral immunization does result in high IgA responses in mucosal tissues and secretions. Recently, we showed that Lactobacillus provides T-cell help for surface associated antigenic determinants (carrier effect) and additionally functions as an adjuvant, resulting in systemic IgM, IgG and IgA responses. These results provide promising new opportunities for the development of effective oral vaccines. Lactobacillus is a GRAS (Generally Recognized As Safe) organism, which can function as a vector for the delivery o f foreign antigens, expressed by DNA-recombinant technology,
to the gastro-intestinal tract. In this study we compare the use of dead Lactobacilli vs. a live vector and the use of non-colonizing vs. colonizing strains as carrier for immunogens from pathogens. Furthermore, we present a new method for the detection of these and other bacteria in vivo, using lipophilic carbocyanin dyes. We provide an integral histological and immunological image of the routing of the antigen in the gut-associated lymphoid system, the development of local and systemic antigen-specific antibody and the formation of memory, using Lactobacillus-immunogen conjugates and genetically engineered Lactobacillus-strains. This approach aims to develop a safe, effective oral delivery system that can accommodate antigens from different pathogens for large scale vaccination programs.
Session 4: Non-living delivery systems
Non-living antigen delivery systems Timothy R. Hirst The Biological Laboratory, University of Kent at Canterbury, Canterbury, CT2 7NJ, UK In the past few years there have been astonishing advances in both the molecular characterization of virulence factors, and in the analysis of the cellular and humoral immune responses to them. These developments provide the prospect of: ( 1 ) being able to identify the precise epitopes or whole antigens that are capable of eliciting protective immunity to particular pathogens and (2) in obtaining sufficient quantities of such epitopes or antigens using peptide synthesis or recombinant DNA techniques to enable the production of highly defined subunit vaccines. These developments should eliminate any of the unwanted side-effects of killed or attenuated vaccines and provide a large and ready source of an immunogen, which it may not be possible to purify from the original pathogen. Such developments have also resulted in the design of new antigen delivery systems in which the antigen or epitope is attached to a carrier or matrix support. These include, for example, the use of ISCOMS, liposomes, microparticles, solid matrix antibody-
antigen complexes and protein carriers. We have focussed on the potential of a multivalent protein-based carrier, the non-toxic B subunit of heat-labile enterotoxin (EtxB) from Escherichia coli, which is easily manipulated for either the genetic or chemical attachment of antigens or epitopes. EtxB, for reasons that are not completely understood, is an inherently potent immunogen that elicits high-titre serum antibody responses when given systemically, even in the absence of an adjuvant, and it induces local immune responses in the gut and sero-conversion when administered orally. We have engineered multiple defined epitopes and antigens onto EtxB, including a small heat-stable enterotoxin (ST) that is normally produced by certain diarrhoeagenic strains of E. coli. The structural and immunological properties of these fusions including EtxB-ST, and the prospect of using EtxB as a carrier for stimulating gut mucosal immune responses to the attached antigen will be discussed.
Vaccine, Vol. 10, Issue 4, 1992 265
Live Salmonella as vaccines and carriers of heterologous antigens to the mammalian immune system Steve Chatfield Medeva Group Research Ltd. Vaccine Research Unit, Wellcome Research Laboratories, South Eden Park Road, Beckenham, Kent, UK Salmonella species can be rationally attenuated by introducing non-reverting defined mutations into the chromosome to produce live oral vaccine strains. Several genes have been identified which when mutated will attenuate Salmonellae. In particular salmonella strains harbouring mutations in genes involved in the pre-chorismate biosynthetic pathway make excellent oral vaccines evoking strong humoral, local and cellular immune responses in the host. Because of the spectrum of immune responses induced by live vaccine strains they have the potential to be used for delivery of heterologous antigens to
the mammalian immune system. A number of other antigens from other bacteria, viruses and parasites have been expressed in live Salmonella strains. Such hybrid strains have the potential to be used as multivalent vaccines against a number of infectious diseases. In particular we have constructed a candidate oral typhoid vaccine based on an attenuated Salmonella typhi strain expressing fragment C, a C terminal non-toxic protein of tetanus toxin. It is hoped that such bivalent strains may offer important advances against such infectious diseases.
Oral vaccination of mice with Lactobacillus-immunogenconjugates Wim J.A. Boersma, Koen Gerritse, Marijke Kottenhage, Mark Posno and Eric Claassen TNO Medical Biological Laboratory, POB 45, 2280 AA, Rijswijk, The Netherlands Ideally, vaccines should be given orally, as this route of administration is convenient and inexpensive. However, oral immunization is generally inefficient in generating systemic antibody responses and it requires large quantities of the immunogen. On the other hand, oral immunization does result in high IgA responses in mucosal tissues and secretions. Recently, we showed that Lactobacillus provides T-cell help for surface associated antigenic determinants (carrier effect) and additionally functions as an adjuvant, resulting in systemic IgM, IgG and IgA responses. These results provide promising new opportunities for the development of effective oral vaccines. Lactobacillus is a GRAS (Generally Recognized As Safe) organism, which can function as a vector for the delivery o f foreign antigens, expressed by DNA-recombinant technology,
to the gastro-intestinal tract. In this study we compare the use of dead Lactobacilli vs. a live vector and the use of non-colonizing vs. colonizing strains as carrier for immunogens from pathogens. Furthermore, we present a new method for the detection of these and other bacteria in vivo, using lipophilic carbocyanin dyes. We provide an integral histological and immunological image of the routing of the antigen in the gut-associated lymphoid system, the development of local and systemic antigen-specific antibody and the formation of memory, using Lactobacillus-immunogen conjugates and genetically engineered Lactobacillus-strains. This approach aims to develop a safe, effective oral delivery system that can accommodate antigens from different pathogens for large scale vaccination programs.
Session 4: Non-living delivery systems
Non-living antigen delivery systems Timothy R. Hirst The Biological Laboratory, University of Kent at Canterbury, Canterbury, CT2 7NJ, UK In the past few years there have been astonishing advances in both the molecular characterization of virulence factors, and in the analysis of the cellular and humoral immune responses to them. These developments provide the prospect of: ( 1 ) being able to identify the precise epitopes or whole antigens that are capable of eliciting protective immunity to particular pathogens and (2) in obtaining sufficient quantities of such epitopes or antigens using peptide synthesis or recombinant DNA techniques to enable the production of highly defined subunit vaccines. These developments should eliminate any of the unwanted side-effects of killed or attenuated vaccines and provide a large and ready source of an immunogen, which it may not be possible to purify from the original pathogen. Such developments have also resulted in the design of new antigen delivery systems in which the antigen or epitope is attached to a carrier or matrix support. These include, for example, the use of ISCOMS, liposomes, microparticles, solid matrix antibody-
antigen complexes and protein carriers. We have focussed on the potential of a multivalent protein-based carrier, the non-toxic B subunit of heat-labile enterotoxin (EtxB) from Escherichia coli, which is easily manipulated for either the genetic or chemical attachment of antigens or epitopes. EtxB, for reasons that are not completely understood, is an inherently potent immunogen that elicits high-titre serum antibody responses when given systemically, even in the absence of an adjuvant, and it induces local immune responses in the gut and sero-conversion when administered orally. We have engineered multiple defined epitopes and antigens onto EtxB, including a small heat-stable enterotoxin (ST) that is normally produced by certain diarrhoeagenic strains of E. coli. The structural and immunological properties of these fusions including EtxB-ST, and the prospect of using EtxB as a carrier for stimulating gut mucosal immune responses to the attached antigen will be discussed.
Vaccine, Vol. 10, Issue 4, 1992 265