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D Hone

Publications and source records attributed to D Hone.

24 records · Page 2Linked to original sources
PubMed1988

A chromosomal integration system for stabilization of heterologous genes in Salmonella based vaccine strains.

We have developed a system whereby heterologous DNA encoding an antigen from an enteropathogen may be recombined into the chromosome of an attenuated Salmonella carrier strain. The system involves two steps: (i) integration of a hisOG deletion mutation into the chromosome; (ii) replacement of the hisOG deletion by the complete hisOG region and the segment of heterologous DNA which encodes the antigen of interest. Recombinants may be selected (his+). The system was used to integrate the genes encoding K88 fimbriae from enterotoxigenic Escherichia coli into the chromosome of a galE mutant of Salmonella typhimurium (LT2H1). Recombinants were detected at a frequency of between 1.0 x 10(-3) and 1.5 x 10(-3). A variety of tests confirmed that the K88 genes were integrated into the chromosome of LT2H1 and were expressed. The stability of the recombinant was tested both in vivo and in vitro. When administered orally to mice, the recombinant elicited a serum antibody response to K88, and retained the Salmonella vaccine potential of the vector strain.

Antigens, Bacterial↗
PubMed1987

Construction of defined galE mutants of Salmonella for use as vaccines.

We describe the molecular cloning of the gal operon of Salmonella typhimurium LT2 and the localization of the gal promoter and the genes galE, galT, and galK. The order of the genes and the direction of transcription was the same as in Escherichia coli K12. A restriction enzyme map of the operon was obtained, and the approximate termini of the gal genes were located by using transposon insertion mutagenesis and minicell analysis. We constructed a plasmid that contained a defined 0.4-kilobase deletion in the galE but still expressed galT and galK activities from the gal promoter. This galE deletion was recombined into the chromosomal gal operons of S. typhimurium and Salmonella typhi Ty2. The resulting strains were vigorous, nonreverting galE mutants that were sensitive to galactose-induced lysis at 0.2 mM galactose. The S. typhimurium galE derivatives were avirulent and protective in mice.

Animals↗
PubMedDate not supplied

Clinical and field trials with attenuated Salmonella typhi as live oral vaccines and as "carrier" vaccines.

In recent years there has been a resurgence of research to develop new and improved attenuated strains of Salmonella typhi to function as live oral vaccines against typhoid fever and to serve as "carrier" vaccines to express foreign antigens of other pathogens and deliver them to the immune system. Strain Ty21a has served as a prototype in clinical and field trials to identify the optimal formulations and dosage schedules for live vaccines and to quantitate the duration of protection that can be achieved. Clinical trials with three new attenuated S. typhi candidate vaccines, a Vi+ variant of Ty21a, an aroC,aroD double mutant recombinant strain and a cya,crp double mutant, are underway or will be initiated shortly.

Administration, Oral↗
PubMedDate not supplied

Vaccination against enteric bacterial diseases.

We review evidence that the systemic and mucosal immune systems of the body are compartmentalized. The development of immunity against an antigen at one mucosal surface may lead to the appearance of that immunity at other mucosal surfaces. In order to attain good protective immunity against a bacterial enteropathogen, it may be necessary to induce such immunity through the mucosal immune system of the gut. Earlier attempts to elicit protective immunity against bacterial enteropathogens by parenteral vaccination are reviewed. The modern approach involves oral administration of antigen. Such antigen may consist of killed bacteria or--more effectively--live, attenuated bacteria bearing antigens of interest. Such bacteria may be enteropathogens attenuated by mutation, either general or site-directed, or hybrid strains in which a bacterial carrier expresses an antigenic determinant of interest from cloned DNA. While good progress has been made in the comprehension of the requirements for effective vaccination against enteropathogenic bacteria, future work will produce more effective carrier strains than are currently available.

Administration, Oral↗