Abstract: We describe a regulated antigen delivery system (RADS) that has (a) a vector that includes (1) a gene encoding a desired gene product operably linked to a control sequence, (2) an origin of replication conferring vector replication using DNA polymerase III, and (3) an origin of replication conferring vector replication using DNA polymerase I, where the second origin of replication is operably linked to a control sequence that is repressible by a repressor. The RADS microorganism also has a gene encoding a repressor, operably linked to an activatible control sequence. The RADS described provide high levels of the desired gene product after repression of the high copy number origin of replication is lifted. The RADS are particularly useful as live bacterial vaccines. Also described is a delayed RADS system, in which there is a delay before the high copy number origin is expressed after the repression is lifted. The delayed RADS is also particularly useful for live bacterial vaccines.

Abstract: The present invention relates to immunogenic compositions comprising a live attenuated derivative of a pathogenic Enterobacteriaceae bacteria. The attenuated derivative of a pathogenic Enterobacteriaceae bacteria comprises a polynucleotide that encodes a foreign antigen. The attenuated derivative of the pathogenic Enterobacteriaceae bacteria has increased expression of Type 1 fimbriae relative to the pathogenic Enterobacteriaceae bacteria from which the attenuated derivative was derived. The present invention also relates to immunogenic compositions that elicit an enhanced Th2 immune response in an individual. The present invention further provides a method of modulating the immune response of an individual comprising administering to said individual the immunogenic compositions of the present invention.

Abstract: Disclosed are vaccines and immunogenic compositions which use live attenuated pathogenic bacteria, such as Salmonella, to deliver ectopic antigens to the mucosal immune system of vertebrates. The attenuated pathogenic bacteria are engineered to secrete the antigen into the periplasmic space of the bacteria or into the environment surrounding the bacteria. The vertebrate mounts a Th2-mediated immune response toward the secreted antigen.

Abstract: Disclosed is an Environmentally Limited Viability System (ELVS) for microorganisms based on differences between permissive and non-permissive environments. Viability of the microorganisms are limited to a permissive environment by specifically expressing one or more essential genes only in the permissive environment, and/or expressing one or more lethal genes only in the non-permissive environment. Temporary viability in a non-permissive environment can be achieved by temporarily expressing one or more essential genes in a non-permissive environment, and/or temporarily delaying expression of one or more lethal genes in the non-permissive environment. Environmentally Limited Viability Systems are also disclosed involving coordinate expression of a combination of essential genes and lethal genes. Microorganisms containing an Environmentally Limited Viability System are useful for release into permissive and non-permissive environments.

Abstract: Attenuated immunogenic bacteria having an RpoS+ phenotype, in particular, Salmonella enterica serotype Typhi having an RpoS+ phenotype and methods therefor are disclosed. The Salmonella have in addition to an RpoS+ phenotype, an inactivating mutation in one or more genes which render the microbe attenuated, and a recombinant gene capable of expressing a desired protein. The Salmonella are attenuated and have high immunogenicity so that they can be used in vaccines and as delivery vehicles for genes and gene products. Also disclosed are methods for preparing the vaccine delivery vehicles.

Abstract: Attenuated immunogenic bacteria having an RpoS+ phenotype, in particular, Salmonella enterica serotype Typhi having an RpoS+ phenotype and methods therefor are disclosed. The Salmonella have in addition to an RpoS+ phenotype, an inactivating mutation in one or more genes which render the microbe attenuated, and a recombinant gene capable of expressing a desired protein. The Salmonella are attenuated and have high immunogenicity so that they can be used in vaccines and as delivery vehicles for genes and gene products. Also disclosed are methods for preparing the vaccine delivery vehicles.

Abstract: Avirulent immunogenic Salmonella enterica serotype Typhi and methods therefor are disclosed. The Salmonella have an RpoS.sup.+ phenotype, an inactivating mutation in one or more genes which renders the microbe avirulent, and a recombinant gene capable of expressing a desired protein. The Salmonella are avirulent and have high immunogenicity so that they can be used in vaccines and as delivery vehicles for the desired antigen. Also disclosed are methods for preparing the Salmonella and vaccine delivery vehicles therefor.

Abstract: This invention relates to a vaccine for the immunization of a vertebrate, comprising:an avirulent derivative of a pathogenic microbe that expresses a recombinant gene derived from a pathogen of said vertebrate it being provided that said avirulent microbe does not normally exchange genetic material with said pathogen, to produce an antigen capable of inducing an immune response in said vertebrate against said pathogen.

Abstract: This invention provides immunogenic compositions for the immunization of a vertebrate or invertebrate comprising an avirulent derivative of S. typhi. The derivatives having a mutation of the cya and/or crp and/or cdt genes. The invention also provides immunogenic compositions for the immunization of a vertebrate and invertebrate comprising an avirulent derivative of the above type which is capable of expressing a recombinant gene derived from a pathogen of said vertebrate or invertebrate individual to produce an antigen capable of inducing an immune response against said pathogen. Other embodiments of the invention include methods of preparing immunogenic compositions from these strains, and strains useful in the preparation of the immunogenic compositions, as well as methods of stimulating the immune system to respond to an immunogenic antigen of S. typhi by administration of the immunogenic composition.

Abstract: This invention provides immunogenic compositions for the immunization of a vertebrate or invertebrate comprising an avirulent derivative of S. typhi. The derivatives having a mutation of the cya and/or crp and/or cdt genes. The invention also provides immunogenic compositions for the immunization of a vertebrate and invertebrate comprising an avirulent derivative of the above type which is capable of expressing a recombinant gene derived from a pathogen of said vertebrate or invertebrate individual to produce an antigen capable of inducing an immune response against said pathogen. Other embodiments of the invention include methods of preparing immunogenic compositions from these strains, and strains useful in the preparation of the immunogenic compositions, as well as methods of stimulating the immune system to respond to an immunogenic antigen of S. typhi by administration of the immunogenic composition.

Abstract: The invention encompasses methods of maintaining desired recombinant genes in a genetic population of cells expressing the recombinant gene. The methods utilize mutant cells which are characterized by a lack of a functioning native gene encoding an enzyme which is essential for cell survival, wherein this enzyme catalyzes a step in the biosynthesis of an essential cell wall structural component and the presence of a first recombinant gene encoding an enzyme which is a functional replacement for the native enzyme, wherein the first recombinant gene cannot replace the defective chromosomal gene. The first recombinant gene is structurally linked to a second recombinant gene encoding a desired product. Loss of the first recombinant gene causes the cells to lyse when the cells are in an environment where a product due to the expression of the first recombinant gene is absent. The invention also encompasses methods of creating and isolating mutant cells with the above characteristics.

Abstract: The invention is directed to transgenic plants expressing colonization and/or virulence antigens specified by genes from pathogenic microorganisms. It is also directed to the use of such transgenic plants for oral immunization of humans and other animals to elicit a secretory immune response which inhibits colonization of or invasion by such pathogenic microorganisms through a mucosal surface of humans or other animals.

Abstract: The invention is directed to transgenic plants expressing colonization and/or virulence antigens specified by genes from pathogenic microorganisms. It is also directed to the use of such transgenic plants for oral immunization of humans and other animals to elicit a secretory immune response which inhibits colonization of or invasion by such pathogenic microorganisms through a mucosal surface of humans or other animals.

Abstract: The invention encompasses methods of maintaining desired recombinant genes in a genetic population of cells expressing the recombinant gene. The methods utilize mutant cells which are characterized by a lack of a functioning native gene encoding an enzyme which is essential for cell survival, wherein this enzyme catalyzes a step in the biosynthesis of an essential cell wall structural component and the presence of a first recombinant gene encoding an enzyme which is a functional replacement for the native enzyme, wherein the first recombinant gene cannot replace the defective chromosomal gene. The first recombinant gene is structurally linked to a second recombinant gene encoding a desired product. Loss of the first recombinant gene causes the cells to lyse when the cells are in an environment where a product due to the expression of the first recombinant gene is absent. The invention also encompasses methods of creating and isolating mutant cells with the above characteristics.

Abstract: Avirulent microbes which include a recombinant expression system encoding a gamete-specific antigen, are disclosed. The microbes can be used in compositions to immunize a vertebrate subject against the gamete-specific antigen, thereby preventing or reducing conception rates in the subject to which they are administered.

Abstract: The invention is directed to transgenic plants expressing colonization and/or virulence antigens specified by genes from pathogenic microorganisms. It is also directed to the use of such transgenic plants for oral immunization of humans and other animals to elicit a secretory immune response which inhibits colonization of or invasion by such pathogenic microorganisms through a mucosal surface of humans or other animals.

Abstract: This invention provides a vaccine for the immunization of a vertebrate or invertebrate comprising an avirulent derivative of S. choleraesuis. The derivatives being substantially incapable of producing functional adenylate cyclase and/or cyclic AMP receptor protein. The invention also provides a vaccine for the immunization of a vertebrate and invertebrate comprising a virulent derivative of a pathogenic microbe said derivative being substantially incapable of producing functional adenylate cyclase and/or cyclic AMP receptor protein while being capable of expressing a recombinant gene derived from a pathogen of said vertebrate to produce an antigen capable of inducing an immune response in said vertebrate against said pathogen.

Abstract: The phoP gene and its equivalents are of a type which have "global regulation of pathogenicity", i.e., they coordinately regulate a number of genes including those that encode bacterial virulence factors. In Salmonella, the phoP gene product also controls the expression of non-specific acid phosphatase from the phoN gene. A central feature of the invention are microorganisms which are avirulent as a result, in whole or in part, of a mutation in phoP, but which retain their immunogenicity. These cells are suitable as components of live vaccines.

Abstract: This invention provides immunogenic compositions for the immunization of a vertebrate or invertebrate comprising an avirulent derivative of S. typhi. The derivatives having a mutation of the cya and/or crp and/or cdt genes. The invention also provides immunogenic compositions for the immunization of a vertebrate and invertebrate comprising an avirulent derivative of the above type which is capable of expressing a recombinant gene derived from a pathogen of said vertebrate or invertebrate individual to produce an antigen capable of inducing an immune response against said pathogen. Other embodiments of the invention include methods of preparing immunogenic compositions from these strains, and strains useful in the preparation of the immunogenic compositions, as well as methods of stimulating the immune system to respond to an immunogenic antigen of S. typhi by administration of the immunogenic composition.

Abstract: This invention provides immunogenic compositions for the immunization of a vertebrate or invertebrate comprising an avirulent derivative of S. typhi. The derivatives having a mutation of the cya and/or crp and/or cdt genes. The invention also provides immunogenic compositions for the immunization of a vertebrate and invertebrate comprising an avirulent derivative of the above type which is capable of expressing a recombinant gene derived from a pathogen of said vertebrate or invertebrate individual to produce an antigen capable of inducing an immune response against said pathogen. Other embodiments of the invention include methods of preparing immunogenic compositions from these strains, and strains useful in the preparation of the immunogenic compositions, as well as methods of stimulating the immune system to respond to an immunogenic antigen of S. typhi by administration of the immunogenic composition.