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Myron M Levine - One of the best experts on this subject based on the ideXlab platform.
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manipulation of salmonella typhi gene expression impacts innate cell responses in the human intestinal mucosa
Frontiers in Immunology, 2018Co-Authors: Rosângela Salernogoncalves, Myron M Levine, James E Galen, Alessio Fasano, Marcelo B SzteinAbstract:Although immunity induced by typhoid fever is moderated and short-lived, typhoid vaccination with the attenuated Ty21a Oral Vaccine generates long-lasting protection rates reaching up to 92%. Thus, there are important differences on how wild-type Salmonella and typhoid Vaccine strains stimulate host immunity. We hypothesize that Vaccine strains with different mutations might affect gut inflammation and intestinal permeability by different mechanisms. To test this hypothesis, we used an in vitro organotypic model of the human intestinal mucosa composed of human intestinal epithelial cells, lymphocytes/monocytes, endothelial cells, and fibroblasts. We also used six Salmonella enterica serovar Typhi (S. Typhi) strains: the licensed Ty21a Oral Vaccine, four typhoid Vaccine candidates (i.e., CVD 908, CVD 909, CVD 910, and CVD 915) and the wild-type Ty2 strain. We found that genetically engineered S. Typhi Vaccine strains elicit differential host changes not only in the intestinal permeability and secretion of inflammatory cytokines, but also in the phenotype and activation pathways of innate cells. These changes were distinct from those elicited by the parent wild-type S. Typhi and depended on the genetic manipulation. In sum, these results emphasize the importance of carefully selecting specific manipulations of the Salmonella genome in the development of typhoid Vaccines.
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Data_Sheet_2_Manipulation of Salmonella Typhi Gene Expression Impacts Innate Cell Responses in the Human Intestinal Mucosa.PDF
2018Co-Authors: Rosângela Salerno-gonçalves, Myron M Levine, James E Galen, Alessio Fasano, Marcelo B SzteinAbstract:Although immunity induced by typhoid fever is moderated and short-lived, typhoid vaccination with the attenuated Ty21a Oral Vaccine generates long-lasting protection rates reaching up to 92%. Thus, there are important differences on how wild-type Salmonella and typhoid Vaccine strains stimulate host immunity. We hypothesize that Vaccine strains with different mutations might affect gut inflammation and intestinal permeability by different mechanisms. To test this hypothesis, we used an in vitro organotypic model of the human intestinal mucosa composed of human intestinal epithelial cells, lymphocytes/monocytes, endothelial cells, and fibroblasts. We also used six Salmonella enterica serovar Typhi (S. Typhi) strains: the licensed Ty21a Oral Vaccine, four typhoid Vaccine candidates (i.e., CVD 908, CVD 909, CVD 910, and CVD 915) and the wild-type Ty2 strain. We found that genetically engineered S. Typhi Vaccine strains elicit differential host changes not only in the intestinal permeability and secretion of inflammatory cytokines, but also in the phenotype and activation pathways of innate cells. These changes were distinct from those elicited by the parent wild-type S. Typhi and depended on the genetic manipulation. In sum, these results emphasize the importance of carefully selecting specific manipulations of the Salmonella genome in the development of typhoid Vaccines.
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helicobacter pylori infection affects immune responses following vaccination of typhoid naive us adults with attenuated salmonella typhi Oral Vaccine cvd 908 htra
The Journal of Infectious Diseases, 2014Co-Authors: Khitam Muhsen, Marcela F Pasetti, Mardi Reymann, David Y Graham, Myron M LevineAbstract:Improved sanitation, access to treated water, and vaccination constitute the key preventive measures to control endemic typhoid fever [1], a persisting public health problem in many developing countries. Currently, there are 2 recommended licensed typhoid Vaccines, parenteral purified Vi capsular polysaccharide [2, 3] and Oral attenuated strain Ty21a [3–5]. Both Vaccines are well tolerated and confer approximately 65% efficacy [4, 5], but their uptake in typhoid-endemic developing countries has been disappointingly low, perhaps in part due to their limitations. For example, while Ty21a confers long-lived protection [5], it requires 3 spaced doses (approximately 48 hours apart). Vi polysaccharide, administered as a single dose, is a T-independent antigen that confers relatively short-lived immunity (<3 years) and does not elicit immunologic memory [3]. Finally, neither Vaccine is recommended for children less than 2 years of age. One strategy to improve typhoid vaccination is to administer a recombinant attenuated S. Typhi strain that is similarly well tolerated as Ty21a but is markedly more immunogenic so that a single Oral dose suffices [6–10]. Live Vaccine candidate CVD 908-htrA was derived by creating 3 independent attenuating deletions in aroC and aroD (which render the Vaccine strain dependent on 2,3 dihydroxybenzoate, a substrate not available in human tissues) and in htrA (which encodes a serine protease stress protein) [6, 7]. CVD 908-htrA was clinically well tolerated and immunogenic in US adults following administration of a single dose in Phase I and II clinical trials [6, 7]. Despite the potential advantages of Oral immunization over parenteral vaccination, licensed Oral enteric Vaccines to prevent rotavirus, poliovirus and Vibrio cholerae O1 illness have often exhibited lower immunogenicity and efficacy when given to persons living in developing countries compared to subjects in industrialized countries [11, 12]. In contrast, Ty21a Vaccine has demonstrated a credible level of efficacy in subjects residing in endemic areas [4, 5, 13], suggesting that live Oral typhoid Vaccines may behave differently. In previous studies we have shown that small-bowel bacterial overgrowth and helminthic infections can affect the immunogenicity of Oral V. cholerae O1 Vaccine CVD 103-HgR [14, 15]; thus, we pondered whether preexisting chronic gastrointestinal infections may affect the success of Oral immunization with the new generation of single-dose typhoid Vaccines. Of particular interest is H. pylori, a bacterium that persistently colonizes gastric mucosa, typically resulting in progressive gastric inflammation. Occasional H. pylori–infected adults progress to develop peptic ulcer disease and, rarely, gastric lymphoma and adenocarcinoma ensue [16]. H. pylori can also induce hypochlorhydria [17, 18], which can facilitate the passage of bacterial pathogens through the stomach so that they reach the small intestine in larger numbers, thereby increasing the risk of clinically overt enteric illness from acid-sensitive bacterial enteropathogens such as Salmonella spp. Indeed, case-control studies from India [19] and Indonesia [20] have demonstrated a significant increased likelihood of culture-confirmed typhoid fever among H. pylori–infected subjects versus uninfected persons [19, 20]. However, since these typhoid studies were undertaken in typhoid-endemic regions [19, 20], it is difficult to decipher if the observed association was due to common exposures for both H. pylori and S. Typhi or to enhanced passage of pathogen through the gastric barrier facilitated by the physiologic consequences of H. pylori colonization, or to both. Independent evidence incriminating hypochlorhydria as a risk factor comes from epidemiologic studies undertaken in the United States showing that consumption of antacids increases the risk of salmonellosis due to nontyphoidal serovars S. Typhimurium [21], S. Dublin [22], and S. Enteritidis [23]. Based on the above observations, we hypothesized that H. pylori infection may impact the immune response to Oral attenuated typhoid Vaccines. To address this question initially in a population that is not exposed to the potentially confounding effect of repetitive prior exposure to S. Typhi (as occurs in a typhoid-endemic area), we took advantage of the Oral immunization of typhoid-naive US adults with CVD 908-htrA Vaccine to examine the association between underlying H. pylori infection, serum pepsinogens (PGs) as markers of gastritis, and the immune response to this live Oral Vaccine.
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duration of efficacy of ty21a attenuated salmonella typhi live Oral Vaccine
Vaccine, 1999Co-Authors: Myron M Levine, Catterine Ferreccio, Paulina Abrego, Oriana San Martin, Edith Ortiz, S J CryzAbstract:Currently, two different formulations of Ty21a live Oral typhoid Vaccine are commercialized. The enteric-coated capsule formulation was licensed based on results of three years of follow-up of a randomized, placebo-controlled, double-blind field trial in Area Occidente, Santiago, Chile, which demonstrated that three doses of this formulation, given on an every other day immunization schedule, conferred the best protection among several options evaluated. Subsequently, a liquid formulation (lyophilized Vaccine organisms reconstituted with buffer and water into a Vaccine cocktail) was commercialized after it was shown to provide superior protection than enteric-coated capsules over three years of follow-up in a randomized, placebo-controlled field trial in Area Sur Oriente and Area Norte, Santiago. Surveillance in the Area Occidente trial was continued for four additional years (i.e., total seven years of follow-up) and in the Area Sur Oriente/Area Norte trial for two additional years (i.e., a total of five years of follow-up). These additional surveillance data, which were analyzed to ascertain the longevity of protection conferred by these formulations of Ty21a, revealed that three doses of Ty21a in enteric-coated capsules (every other day schedule) conferred 67% protection over three years and 62% protection over seven years of follow-up, whereas three doses of liquid formulation (every other day schedule) elicited 77% protection over three years and 78% over five years of follow-up. Based on its excellent clinical acceptability, ease of Oral administration, proven practicality in school-based mass immunization, and long-term efficacy enduring at least seven years, it is proposed that school-based immunization with Ty21a be utilized as a control measure in areas where the incidence of typhoid fever is high and Salmonella typhi are antibiotic-resistant.
Dennis J Kopecko - One of the best experts on this subject based on the ideXlab platform.
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stable chromosomal expression of shigella flexneri 2a and 3a o antigens in the live salmonella Oral Vaccine vector ty21a
Clinical and Vaccine Immunology, 2017Co-Authors: Madushini N Dharmasena, Manuel Osorio, Scott Stibitz, Kazuyo Takeda, Dennis J KopeckoAbstract:We have been exploring the use of the live, attenuated, Salmonella enterica serovar Typhi Ty21a Vaccine strain as a versatile Oral Vaccine vector for the expression and delivery of multiple foreign antigens, including Shigella O-antigens. In this study, we separately cloned genes necessary for the biosynthesis of the S. flexneri serotype 2a and 3a O-antigens, which have been shown previously to provide broad cross-protection to multiple, disease-predominant S. flexneri serotypes. The cloned S. flexneri 2a rfb operon along with, bgt and gtrII, encoded on the SfII bacteriophage were sufficient in Ty21a to express the heterologous S. flexneri 2a O-antigen containing the 3,4 antigenic determinants. Further, this rfb operon along with gtrA, gtrB and gtrX encoded on the Sfx bacteriophage and oac encoded on the Sf6 bacteriophage were sufficient to express S. flexneri 3a O-antigen containing the 6, 7, and 8 antigenic determinants.Ty21a carrying these plasmid-encoded or chromosomally-inserted genes demonstrated simultaneous and stable expression of homologous S. Typhi O-antigen plus the heterologous S. flexneri O-antigen. Candidate Ty21a Vaccine strains expressing heterologous S. flexneri 2a or 3a LPS elicited significant serum antibody responses against both homologous S. Typhi and heterologous Shigella LPS and protected mice against virulent S. flexneri 2a or 3a challenges. These new S. flexneri 2a and 3a expressing Ty21a Vaccine strains, together with our previously constructed Ty21a strains expressing S. sonnei or S. dysenteriae 1 O-antigens have the potential to be used together for simultaneous protection against the predominant causes of shigellosis worldwide as well as against typhoid fever.
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stable expression of shigella dysenteriae serotype 1 o antigen genes integrated into the chromosome of live salmonella Oral Vaccine vector ty21a
Pathogens and Disease, 2016Co-Authors: Madushini N Dharmasena, Manuel Osorio, Svetlana Filipova, Christina Marsh, Scott Stibitz, Dennis J KopeckoAbstract:Typhoid fever and shigellosis cause high morbidity and mortality worldwide, yet no anti- Shigella Vaccine is currently available. However, to protect against typhoid fever, an approved Vaccine, based on the attenuated Salmonella enterica serovar Typhi strain Ty21a is available. We have investigated Ty21a as a live Oral Vaccine vector for expression of heterologous foreign antigens to protect against other diseases (e.g. shigellosis, anthrax, and plague). Shigella LPS is a potent Vaccine antigen for serotype-specific protection against Shigellae. We previously reported the construction of a Ty21a derivative expressing S. sonnei O-antigen by insertion of a large (∼12.5 kb) operon comprising the S. sonnei O-antigen biosynthetic genes into a targeted site within the Ty21a chromosome using modified λ red recombineering methods. In the current study, S. dysenteriae 1 O-antigen biosynthetic genes from 2 separate genetic loci, rfp and rfb were assembled and inserted into the Ty21a chromosome by λ red -mediated recombineering to construct strain Ty21a-Sd. To obtain a high level of heterologous LPS expression, the native upstream promoter was replaced with the constitutive lpp promoter, which resulted in Ty21a-Sdl with enhanced heterologous LPS expression. Both Ty21a-Sd and Ty21a-Sdl elicited significant serum antibody responses in mice against both Ty21a and this heterologous Shigella LPS, and conferred protection against virulent S. dysenteriae 1 challenge. This work represents progress toward the goal of a safe and effective Vaccine against Shigella .
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genome sequence of salmonella enterica serovar typhi Oral Vaccine strain ty21a
Genome Announcements, 2013Co-Authors: Deqi Xu, Madushini N Dharmasena, Patricia Guerry, Frederic Poly, Jason Albanese, Jinghua Yang, John O Cisar, Dennis J KopeckoAbstract:ABSTRACT Attenuated Salmonella enterica serovar Typhi strain Ty21a is an important Vaccine for controlling typhoid fever and serves as an Oral vector for delivering heterologous antigens. The key attenuating features of this randomly mutated strain remain in question. Genome sequencing has revealed 679 single nucleotide polymorphisms (SNPs), and will help define alterations contributing to Ty21a safety and immunogenicity.
Frana Oise Norel - One of the best experts on this subject based on the ideXlab platform.
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the rpos mutant allele of salmonella typhi ty2 is identical to that of the live typhoid Vaccine ty21a
Fems Microbiology Letters, 1999Co-Authors: Va Ronique Robbesaule, Frana Oise NorelAbstract:Salmonella requires its alternative sigma factor σS (RpoS) for virulence in mice. rpoS mutants can be frequently isolated from highly passaged Salmonella laboratory strains. In particular, the live typhoid Oral Vaccine Salmonella typhi Ty21a and its parental strain Ty2, a ‘wild-type’ strain widely used for Vaccine development, are rpoS mutants. Here, we show that the nucleotide sequence of the rpoS mutant allele of Ty2 is identical to that of the rpoS mutant allele of Ty21a. This demonstrates that the rpoS mutation arose in Ty2 before the isolation of Ty21a in 1975, an observation that may have implications for Vaccine research.
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the live Oral typhoid Vaccine ty21a is a rpos mutant and is susceptible to various environmental stresses
Fems Microbiology Letters, 1995Co-Authors: Va Ronique Robbesaule, Colette Coynault, Frana Oise NorelAbstract:The rpoS (katF) gene, which encodes a RNA polymerase σ factor (σs), regulates the virulence of Salmonella typhimurium in mice. In the present study, we show that rpoS mutants can be frequently found among laboratory strains of Salmonella. In addition, a rpoS mutation was identified in the S. typhi live Oral Vaccine Ty21a. Introduction of a wild-type rpoS gene in Ty21a allowed the bacteria to survive better under starvation conditions and increased their resistance to other stresses. These results contribute to a better understanding of the genetic background of the live typhoid Oral Vaccine Ty21a and suggest that the rpoS mutation may contribute to the safety of this strain in humans.
Madushini N Dharmasena - One of the best experts on this subject based on the ideXlab platform.
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stable chromosomal expression of shigella flexneri 2a and 3a o antigens in the live salmonella Oral Vaccine vector ty21a
Clinical and Vaccine Immunology, 2017Co-Authors: Madushini N Dharmasena, Manuel Osorio, Scott Stibitz, Kazuyo Takeda, Dennis J KopeckoAbstract:We have been exploring the use of the live, attenuated, Salmonella enterica serovar Typhi Ty21a Vaccine strain as a versatile Oral Vaccine vector for the expression and delivery of multiple foreign antigens, including Shigella O-antigens. In this study, we separately cloned genes necessary for the biosynthesis of the S. flexneri serotype 2a and 3a O-antigens, which have been shown previously to provide broad cross-protection to multiple, disease-predominant S. flexneri serotypes. The cloned S. flexneri 2a rfb operon along with, bgt and gtrII, encoded on the SfII bacteriophage were sufficient in Ty21a to express the heterologous S. flexneri 2a O-antigen containing the 3,4 antigenic determinants. Further, this rfb operon along with gtrA, gtrB and gtrX encoded on the Sfx bacteriophage and oac encoded on the Sf6 bacteriophage were sufficient to express S. flexneri 3a O-antigen containing the 6, 7, and 8 antigenic determinants.Ty21a carrying these plasmid-encoded or chromosomally-inserted genes demonstrated simultaneous and stable expression of homologous S. Typhi O-antigen plus the heterologous S. flexneri O-antigen. Candidate Ty21a Vaccine strains expressing heterologous S. flexneri 2a or 3a LPS elicited significant serum antibody responses against both homologous S. Typhi and heterologous Shigella LPS and protected mice against virulent S. flexneri 2a or 3a challenges. These new S. flexneri 2a and 3a expressing Ty21a Vaccine strains, together with our previously constructed Ty21a strains expressing S. sonnei or S. dysenteriae 1 O-antigens have the potential to be used together for simultaneous protection against the predominant causes of shigellosis worldwide as well as against typhoid fever.
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stable expression of shigella dysenteriae serotype 1 o antigen genes integrated into the chromosome of live salmonella Oral Vaccine vector ty21a
Pathogens and Disease, 2016Co-Authors: Madushini N Dharmasena, Manuel Osorio, Svetlana Filipova, Christina Marsh, Scott Stibitz, Dennis J KopeckoAbstract:Typhoid fever and shigellosis cause high morbidity and mortality worldwide, yet no anti- Shigella Vaccine is currently available. However, to protect against typhoid fever, an approved Vaccine, based on the attenuated Salmonella enterica serovar Typhi strain Ty21a is available. We have investigated Ty21a as a live Oral Vaccine vector for expression of heterologous foreign antigens to protect against other diseases (e.g. shigellosis, anthrax, and plague). Shigella LPS is a potent Vaccine antigen for serotype-specific protection against Shigellae. We previously reported the construction of a Ty21a derivative expressing S. sonnei O-antigen by insertion of a large (∼12.5 kb) operon comprising the S. sonnei O-antigen biosynthetic genes into a targeted site within the Ty21a chromosome using modified λ red recombineering methods. In the current study, S. dysenteriae 1 O-antigen biosynthetic genes from 2 separate genetic loci, rfp and rfb were assembled and inserted into the Ty21a chromosome by λ red -mediated recombineering to construct strain Ty21a-Sd. To obtain a high level of heterologous LPS expression, the native upstream promoter was replaced with the constitutive lpp promoter, which resulted in Ty21a-Sdl with enhanced heterologous LPS expression. Both Ty21a-Sd and Ty21a-Sdl elicited significant serum antibody responses in mice against both Ty21a and this heterologous Shigella LPS, and conferred protection against virulent S. dysenteriae 1 challenge. This work represents progress toward the goal of a safe and effective Vaccine against Shigella .
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genome sequence of salmonella enterica serovar typhi Oral Vaccine strain ty21a
Genome Announcements, 2013Co-Authors: Deqi Xu, Madushini N Dharmasena, Patricia Guerry, Frederic Poly, Jason Albanese, Jinghua Yang, John O Cisar, Dennis J KopeckoAbstract:ABSTRACT Attenuated Salmonella enterica serovar Typhi strain Ty21a is an important Vaccine for controlling typhoid fever and serves as an Oral vector for delivering heterologous antigens. The key attenuating features of this randomly mutated strain remain in question. Genome sequencing has revealed 679 single nucleotide polymorphisms (SNPs), and will help define alterations contributing to Ty21a safety and immunogenicity.
S J Cryz - One of the best experts on this subject based on the ideXlab platform.
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duration of efficacy of ty21a attenuated salmonella typhi live Oral Vaccine
Vaccine, 1999Co-Authors: Myron M Levine, Catterine Ferreccio, Paulina Abrego, Oriana San Martin, Edith Ortiz, S J CryzAbstract:Currently, two different formulations of Ty21a live Oral typhoid Vaccine are commercialized. The enteric-coated capsule formulation was licensed based on results of three years of follow-up of a randomized, placebo-controlled, double-blind field trial in Area Occidente, Santiago, Chile, which demonstrated that three doses of this formulation, given on an every other day immunization schedule, conferred the best protection among several options evaluated. Subsequently, a liquid formulation (lyophilized Vaccine organisms reconstituted with buffer and water into a Vaccine cocktail) was commercialized after it was shown to provide superior protection than enteric-coated capsules over three years of follow-up in a randomized, placebo-controlled field trial in Area Sur Oriente and Area Norte, Santiago. Surveillance in the Area Occidente trial was continued for four additional years (i.e., total seven years of follow-up) and in the Area Sur Oriente/Area Norte trial for two additional years (i.e., a total of five years of follow-up). These additional surveillance data, which were analyzed to ascertain the longevity of protection conferred by these formulations of Ty21a, revealed that three doses of Ty21a in enteric-coated capsules (every other day schedule) conferred 67% protection over three years and 62% protection over seven years of follow-up, whereas three doses of liquid formulation (every other day schedule) elicited 77% protection over three years and 78% over five years of follow-up. Based on its excellent clinical acceptability, ease of Oral administration, proven practicality in school-based mass immunization, and long-term efficacy enduring at least seven years, it is proposed that school-based immunization with Ty21a be utilized as a control measure in areas where the incidence of typhoid fever is high and Salmonella typhi are antibiotic-resistant.
