Abstract: The invention features a nontoxigenic genetically stable mutant strain of V. cholerae which lacks any functional attRS1 sequences is useful as a live, oral vaccine for inducing immunological protection against cholera and a method for making same. The invention also features a killed, oral cholera vaccine comprising at least a first and a second V. cholerae strain, wherein at least one of the strains is a different serotype, and the vaccine also contains cholera toxin B subunit, produced by at least one of the serotypes.

Abstract: A vector capable of integrating into the chromosome of Salmonella including a first DNA sequence encoding a heterologous protein, a second DNA sequence encoding a marker, and a third DNA sequence encoding a phoP regulatory region regulated gene product necessary for virulence, the third DNA sequence being mutationally inactivated.

Abstract: A reporter system relating to in vivo expression technology was devised to aid in the identification and study of genes that display temporal or spatial patterns of expression during infection of host tissues. The method of this invention comprises constructing a strain or pool of strains of a microorganism which contains an artificial cointegrate comprising a reporter gene flanked by direct repeats of sequences to which a resolvase enzyme binds, thus catalyzing excision of the reporter gene, and further contains a coding sequence under the control of a promoter sequence which encodes transcripts, the expression of which are easily monitored in vitro and which result in a permanent genetic change, excision of the reporter gene, that is heritable and easily detectable subsequent to induction of the synthetic operon.

Abstract: A reporter system relating to in vivo expression technology was devised to aid in the identification and study of genes that display temporal or spatial patterns of expression during infection of host tissues. The method of this invention comprises integrating a site-specific DNA recombinase expression vector, and a reporter gene that is permanently removable by the recombinase, by way of homologous recombination into a microorganism's chromosome and inducing the expression of a synthetic operon which encodes transcripts, the expression of which are easily monitored in vitro and which result in a permanent genetic change, excision of the reporter gene, that is heritable and easily detectable subsequent to induction of the synthetic operon.

Abstract: A genetic system termed in vivo expression technology was devised that positively selects for microbial genes that are specifically induced when microbes infect their host. The method of this invention comprises complementing the growth of an auxotrophic or antibiotic sensitive microorganism by integrating an expression vector by way of homologous recombination into the auxotrophic or antibiotic sensitive microorganism's chromosome and inducing the expression of a synthetic operon which encodes transcripts, the expression of which are easily monitored both in vitro and in vivo.

Abstract: The gene encoding the TcpA pilus has been cloned. It encodes a protein useful in live, killed-cell, and synthetic vaccines. Protein production is enhanced by specific medium conditions.

Abstract: The gene encoding the TcpA pilus has been cloned. It encodes a protein useful in live, killed-cell, and synthetic vaccines. Protein production is enhanced by specific medium conditions.

Abstract: A genetically stable nontoxinogenic form of the Ogawa 395 strain of Vibrio cholerae which has a deletion mutation in both copies of the A.sub.1 -peptide-encoding gene, resulting in the loss of a gene sequence required for expression of a toxic A.sub.1 peptide is disclosed, as well as plasmids and methods for making the strain. The strain is useful as a live or dead oral vaccine.