The Experts below are selected from a list of 276 Experts worldwide ranked by ideXlab platform

Myron M Levine - One of the best experts on this subject based on the ideXlab platform.

  • A tale of two bacterial enteropathogens and one multivalent Vaccine
    Cellular Microbiology, 2019
    Co-Authors: Eileen M. Barry, Myron M Levine
    Abstract:

    : Shigella and enterotoxigenic Escherichia coli (ETEC) are among the top four enteric pathogens that cause diarrheal illness in young children in developing countries and are major etiologic agents of travellers' diarrhoea. A single Vaccine that could target both of these pathogens would have significant public health impact. In this review, we highlight the many pivotal contributions of Phillippe Sansonetti to the identification of molecular mechanisms of pathogenesis of Shigella that paved the way for the development of rationally designed, novel Vaccines candidates. The CVD developed a series of live attenuated Shigella Vaccine strains based on the most prevalent serotypes associated with disease. Shigella Vaccine strains were engineered to express critical ETEC antigens to form a broadly protective Shigella-ETEC multivalent Vaccine.

  • gut homing conventional plasmablasts and cd27 plasmablasts elicited after a short time of exposure to an oral live attenuated Shigella Vaccine candidate in humans
    Frontiers in Immunology, 2014
    Co-Authors: Franklin R Toapanta, Eileen M. Barry, Karen L. Kotloff, Marcela F Pasetti, Jakub K Simon, Myron M Levine, Marcelo B Sztein
    Abstract:

    Currently, there is no licensed Shigella Vaccine; however, various promising live attenuated Vaccine candidates have emerged, including CVD1208S (ΔguaBA, Δset, Δsen S. flexneri 2a), which was shown to be safe and immunogenic in Phase 1 clinical trials. Here we report the immune responses elicited in an outpatient Phase 2 clinical trial in which subjects were vaccinated with CVD 1208S. Oral immunization with CVD 1208S elicited high anti-S. flexneri 2a LPS and IpaB antibody responses, as well as an acute plasmablast (PB) infiltration in peripheral blood 7 days after immunization. PB sorted based on their expression of homing molecules confirmed that cells expressing integrin α4β7 alone or in combination with CD62L were responsible for antibody production (as measured by ELISpot). Furthermore, using high-color flow-cytometry, on day 7 after immunization, we observed the appearance of conventional PB (CPB, CD19dim CD20- CD27+high CD38+high CD3-), as well as a PB population that did not express CD27 (CD27- PB; pre-plasmablasts). The pattern of individual or simultaneous expression of homing markers (integrin α4β7, CD62L, CXCR3 and CXCR4) suggested that CPB cells homed preferentially to the inflamed gut mucosa. In contrast, ~50% CD27- PB cells appear to home to yet to be identified peripheral lymphoid organs or were in a transition state preceding integrin α4β7 upregulation. In sum, these observations demonstrate that strong immune responses, including distinct PB subsets with the potential to home to the gut and other secondary lymphoid organs, can be elicited after a short time of exposure to a Shigella oral

  • effect of wild type Shigella species and attenuated Shigella Vaccine candidates on small intestinal barrier function antigen trafficking and cytokine release
    PLOS ONE, 2014
    Co-Authors: Maria Fiorentino, Marcelo B Sztein, Myron M Levine, Alessio Fasano
    Abstract:

    Bacterial dysentery due to Shigella species is a major cause of morbidity and mortality worldwide. The pathogenesis of Shigella is based on the bacteria's ability to invade and replicate within the colonic epithelium, resulting in severe intestinal inflammatory response and epithelial destruction. Although the mechanisms of pathogenesis of Shigella in the colon have been extensively studied, little is known on the effect of wild-type Shigella on the small intestine and the role of the host response in the development of the disease. Moreover, to the best of our knowledge no studies have described the effects of apically administered Shigella flexneri 2a and S. dysenteriae 1 Vaccine strains on human small intestinal enterocytes. The aim of this study was to assess the coordinated functional and immunological human epithelial responses evoked by strains of Shigella and candidate Vaccines on small intestinal enterocytes. To model the interactions of Shigella with the intestinal mucosa, we apically exposed monolayers of human intestinal Caco2 cells to increasing bacterial inocula. We monitored changes in paracellular permeability, examined the organization of tight-junctions and the pro-inflammatory response of epithelial cells. Shigella infection of Caco2 monolayers caused severe mucosal damage, apparent as a drastic increase in paracellular permeability and disruption of tight junctions at the cell-cell boundary. Secretion of pro-inflammatory IL-8 was independent of epithelial barrier dysfunction. Shigella Vaccine strains elicited a pro-inflammatory response without affecting the intestinal barrier integrity. Our data show that wild-type Shigella infection causes a severe alteration of the barrier function of a small intestinal cell monolayer (a proxy for mucosa) and might contribute (along with enterotoxins) to the induction of watery diarrhea. Diarrhea may be a mechanism by which the host attempts to eliminate harmful bacteria and transport them from the small to the large intestine where they invade colonocytes inducing a strong inflammatory response.

  • Progress and pitfalls in Shigella Vaccine research
    Nature Reviews Gastroenterology & Hepatology, 2013
    Co-Authors: Eileen M. Barry, Karen L. Kotloff, Marcela F Pasetti, Marcelo B Sztein, Alessio Fasano, Myron M Levine
    Abstract:

    Shigella infection continues to be a leading cause of morbidity and mortality, exerting the greatest burden in children in less-industrialized countries Epidemiological studies (for example, Global Enteric Multicenter Study) confirmed the distribution of multiple serotypes in geographical regions as important causes of infection Studies on Shigella pathogenesis have revealed new virulence factors, which might serve as targets for attenuation in live Vaccine strains or as potential Vaccine antigens Vaccine strategies can be divided into serotype-targeted or conserved protein antigen approaches and multiple candidates are in various stages of development and evaluation New immunological measurements are shedding light on important protective responses Multiple barriers (such as insufficient funding to accelerate and complete clinical trials) exist that are impeding the pace of Shigella Vaccine development Renewed awareness of the substantial morbidity and mortality that Shigella infection causes among young children in developing countries, combined with technological innovations in vaccinology, has led to the development of novel Vaccine strategies in the past 5 years. Along with advancement of classic Vaccines in clinical trials and new sophisticated measurements of immunological responses, much new data has been produced, lending promise to the potential for production of safe and effective Shigella Vaccines. Herein, we review the latest progress in Shigella Vaccine development within the framework of persistent obstacles. Shigella infection continues to have a high disease burden worldwide, especially in young children in developing countries. Here, the latest progress in Shigella Vaccine research is reviewed—including the identification of new Vaccine antigens and technological advances in Vaccine design and manufacture—as well as the barriers that impede the development of a successful Shigella Vaccine.

  • progress and pitfalls in Shigella Vaccine research
    Nature Reviews Gastroenterology & Hepatology, 2013
    Co-Authors: Eileen M. Barry, Karen L. Kotloff, Marcela F Pasetti, Marcelo B Sztein, Alessio Fasano, Myron M Levine
    Abstract:

    Shigella infection continues to have a high disease burden worldwide, especially in young children in developing countries. Here, the latest progress in Shigella Vaccine research is reviewed—including the identification of new Vaccine antigens and technological advances in Vaccine design and manufacture—as well as the barriers that impede the development of a successful Shigella Vaccine.

Malabi M Venkatesan - One of the best experts on this subject based on the ideXlab platform.

  • Oral Shigella Vaccines
    Mucosal Vaccines, 2019
    Co-Authors: Marcela F Pasetti, Malabi M Venkatesan, Eileen M. Barry
    Abstract:

    Abstract Shigella is a major cause of diarrhea and dysentery worldwide; the people who are most affected are young children living in poor areas of the world. The most advanced Vaccine approaches employ oral immunization with inactivated or live attenuated organisms or parenteral immunization with O-polysaccharide conjugates and/or bacterial proteins. Oral delivery of whole organisms has been sought to reproduce host immune responses induced after natural infection, which is known to confer protective immunity. The simplicity of manufacturing whole cell Vaccines and the practicality of oral vaccination would facilitate implementation in poor areas and allow to reach the most vulnerable groups. Recent global estimates of diarrheal disease have emphasized the burden of Shigella in childhood long-term morbidity and death and have invigorated efforts by public health authorities, scientists, and funding agencies to accelerate Vaccine development efforts. This chapter reviews the progress of Shigella Vaccine development with a focus on clinically advanced oral Vaccine candidates. It summarizes recent information on disease burden, advances in research on animal models of Vaccine evaluation, and the current understanding of human immunity resulting from infection and vaccination. It concludes with a discussion of gaps in knowledge, technological advances, and the coordinated efforts to achieve a successful Vaccine.

  • A study of different buffers to maximize viability of an oral Shigella Vaccine.
    Vaccine, 2015
    Co-Authors: Lakshmi Chandrasekaran, Lillian Van De Verg, Malabi M Venkatesan
    Abstract:

    Abstract Live, whole cell killed and subunit Vaccines are being developed for diarrheal diseases caused by V. cholerae, Shigella species, ETEC, and Campylobacter. Some of these Vaccines can be administered orally since this route best mimics natural infection. Live Vaccines administered orally have to be protected from the harsh acidic gastric environment. Milk and bicarbonate solutions have been administered to neutralize the stomach acid. For many Shigella Vaccine trials, 100–120 ml of a bicarbonate solution is ingested followed by the live Vaccine candidate, which is delivered in 30 ml of bicarbonate, water or saline. It is not clear if maximum bacterial viability is achieved under these conditions. Also, volumes of neutralizing buffer that are optimal for adults may be unsuitable for children and infants. To address these questions, we performed studies to determine the viability and stability of a Shigella sonnei Vaccine candidate, WRSS1, in a mixture of different volumes of five different buffer solutions added to hydrochloric acid to simulate gastric acidity. Among the buffers tested, bicarbonate solution, rotavirus buffer and CeraVacx were better at neutralizing acid and maintaining the viability of WRSS1. Also, a much smaller volume of the neutralizing buffer was sufficient to counteract stomach acid while maintaining bacterial viability.

  • editorial commentary a Shigella Vaccine against prevalent serotypes
    Clinical Infectious Diseases, 2014
    Co-Authors: Lillian Van De Verg, Malabi M Venkatesan
    Abstract:

    Dysentery due to Shigella is a severe, intensely inflammatory infection that disproportionately affects the very young in less developed parts of the world where there is little to no access to clean water and sanitation. Mortality due to shigellosis has decreased significantly in the last 2 to 3 decades, arguably due, in large part, to the virtual disappearance of major epidemics of S. dysenteriae 1. However, the incidence of diarrheal disease due to other Shigellae has remained high.Worldwide, Shigella is estimated to cause 80– 120million episodes of diarrhea andmore than 100 000 deaths annually, mostly in children aged 70 years residing in 6 countries in East, Southeast, and South Asia [10]. In both studies, S. dysenteriae and S. boydii were infrequently isolated (generally approximately 5% overall). There is less information on South America, where endemic Shigella disease may also be found but where large-scale epidemiological data are not available. However, available reports do indicate that S. sonnei and S. flexneri 2a are predominant there as well [11]. Indeed, the earliest live attenuated Shigella Vaccines tested in the field over 40 years ago by Mel included S. sonnei and S. flexneri 2a in the formulation Received 2 June 2014; accepted 5 June 2014. Invited Commentary to article by Livio et al “Shigella Isolates from the Global Enteric Multicenter Study (GEMS) Inform Vaccine Development”. Correspondence: Lillian L. Van De Verg, PhD, Shigella Scientific Officer, Enteric Vaccine Initiative, Vaccine Development Global Program, PATH, 455 Massachusetts Ave. NW, Washington, DC 20001-2621 (lvandeverg@path.org). Clinical Infectious Diseases © The Author 2014. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals. permissions@oup.com. DOI: 10.1093/cid/ciu471

  • evaluation of an intragastric challenge model for Shigella dysenteriae 1 in rhesus monkeys macaca mulatta for the pre clinical assessment of Shigella Vaccine formulations
    Apmis, 2014
    Co-Authors: Dilara Islam, Malabi M Venkatesan, Nattaya Ruamsap, Patchariya Khantapura, Ajchara Aksomboon, Apichai Srijan, Boonchai Wongstitwilairoong, Ladaporn Bodhidatta, Montip Gettayacamin, Carl J Mason
    Abstract:

    Shigellosis is a worldwide disease, characterized by abdominal pain, fever, vomiting, and the passage of blood- and mucus-streaked stools. Rhesus monkeys and other primates are the only animals that are naturally susceptible to shigellosis. A suitable animal model is required for the pre-clinical evaluation of Vaccines candidates. In this study, the minimal dose of Shigella dysenteriae1 1617 strain required to produce dysentery in four of five (80% attack rate) monkeys using an escalating dose range for three groups [2 × 108, 2 × 109 and 2 × 1010 colony forming unit (CFU)] was determined. In addition, the monkeys were re-infected. The identified optimal challenge dose was 2 × 109 CFU; this dose elicited 60% protection in monkeys when they were re-challenged with a one log higher dose (2 × 1010 CFU). The challenge dose, 2 × 1010 CFU, produced severe dysentery in all monkeys, with one monkey dying within 24 h, elicited 100% protection when re-challenged with the same dose. All monkeys exhibited immune responses. This study concludes that the rhesus monkey model closely mimics the disease and immune response seen in humans and is a suitable animal model for the pre-clinical evaluation of Shigella Vaccine candidates. Prior infection with the 1617 strain can protect monkeys against subsequent re-challenges with homologous strains.

  • oral administration of live Shigella Vaccine candidates in rhesus monkeys show no evidence of competition for colonization and immunogenicity between different serotypes
    Vaccine, 2014
    Co-Authors: Ryan T Ranallo, Robert W. Kaminski, Shoshana Barnoy, Tara L Boren, Shahida Baqar, M Dutta, L A Lugoroman, Malabi M Venkatesan
    Abstract:

    Live oral monovalent Shigella flexneri 2a Vaccine candidates as well as bivalent formulations with Shigella sonnei were evaluated in a rhesus monkey model for colonization and immunogenicity. Freshly harvested suspensions of S. flexneri 2a Vaccine candidates WRSf2G12 and WRSf2G15 as well as S. sonnei Vaccine candidate WRSs3 were nasogastrically administered to groups of rhesus monkeys, Macaca mulatta, either in a monovalent form or when combined with each other. The animals were monitored daily for physical well-being, stools were subjected to quantitative colony immunoblot assays for bacterial excretion and blood and stools were evaluated for humoral and mucosal immune responses. No clinical symptoms were noted in any group of animals and the Vaccine candidates were excreted robustly for 48–72 h without significant changes in either the magnitude or duration of excretion when given as a monovalent or as bivalent mixtures. Similarly, immunological interferences were not apparent in the magnitude of humoral and mucosal immune responses observed toward Shigella-specific antigens when monkeys were fed monovalent or bivalent formulations. These results predict that a multivalent live oral Vaccine of more than one serotype can have a favorable outcome for protection against shigellosis.

Eileen M. Barry - One of the best experts on this subject based on the ideXlab platform.

  • Oral Shigella Vaccines
    Mucosal Vaccines, 2019
    Co-Authors: Marcela F Pasetti, Malabi M Venkatesan, Eileen M. Barry
    Abstract:

    Abstract Shigella is a major cause of diarrhea and dysentery worldwide; the people who are most affected are young children living in poor areas of the world. The most advanced Vaccine approaches employ oral immunization with inactivated or live attenuated organisms or parenteral immunization with O-polysaccharide conjugates and/or bacterial proteins. Oral delivery of whole organisms has been sought to reproduce host immune responses induced after natural infection, which is known to confer protective immunity. The simplicity of manufacturing whole cell Vaccines and the practicality of oral vaccination would facilitate implementation in poor areas and allow to reach the most vulnerable groups. Recent global estimates of diarrheal disease have emphasized the burden of Shigella in childhood long-term morbidity and death and have invigorated efforts by public health authorities, scientists, and funding agencies to accelerate Vaccine development efforts. This chapter reviews the progress of Shigella Vaccine development with a focus on clinically advanced oral Vaccine candidates. It summarizes recent information on disease burden, advances in research on animal models of Vaccine evaluation, and the current understanding of human immunity resulting from infection and vaccination. It concludes with a discussion of gaps in knowledge, technological advances, and the coordinated efforts to achieve a successful Vaccine.

  • A tale of two bacterial enteropathogens and one multivalent Vaccine
    Cellular Microbiology, 2019
    Co-Authors: Eileen M. Barry, Myron M Levine
    Abstract:

    : Shigella and enterotoxigenic Escherichia coli (ETEC) are among the top four enteric pathogens that cause diarrheal illness in young children in developing countries and are major etiologic agents of travellers' diarrhoea. A single Vaccine that could target both of these pathogens would have significant public health impact. In this review, we highlight the many pivotal contributions of Phillippe Sansonetti to the identification of molecular mechanisms of pathogenesis of Shigella that paved the way for the development of rationally designed, novel Vaccines candidates. The CVD developed a series of live attenuated Shigella Vaccine strains based on the most prevalent serotypes associated with disease. Shigella Vaccine strains were engineered to express critical ETEC antigens to form a broadly protective Shigella-ETEC multivalent Vaccine.

  • Shigella isolates from the global enteric multicenter study inform Vaccine development
    Clinical Infectious Diseases, 2014
    Co-Authors: Sofie Livio, Eileen M. Barry, Nancy A Strockbine, Sandra Panchalingam, Sharon M Tennant, Mark E Marohn, Martin Antonio, Anowar Hossain, Inacio Mandomando, John B Ochieng
    Abstract:

    BACKGROUND: Shigella, a major diarrheal disease pathogen worldwide, is the target of Vaccine development. The Global Enteric Multicenter Study (GEMS) investigated burden and etiology of moderate-to-severe diarrheal disease in children aged <60 months and matched controls without diarrhea during 3 years at 4 sites in Africa and 3 in Asia. Shigella was 1 of the 4 most common pathogens across sites and age strata. GEMS Shigella serotypes are reviewed to guide Vaccine development. METHODS: Subjects' stool specimens/rectal swabs were transported to site laboratories in transport media and plated onto xylose lysine desoxycholate and MacConkey agar. Suspect Shigella colonies were identified by biochemical tests and agglutination with antisera. Shigella isolates were shipped to the GEMS Reference Laboratory (Baltimore, MD) for confirmation and serotyping of S. flexneri; one-third of isolates were sent to the Centers for Disease Control and Prevention for quality control. RESULTS: Shigella dysenteriae and S. boydii accounted for 5.0% and 5.4%, respectively, of 1130 Shigella case isolates; S. flexneri comprised 65.9% and S. sonnei 23.7%. Five serotypes/subserotypes comprised 89.4% of S. flexneri, including S. flexneri 2a, S. flexneri 6, S. flexneri 3a, S. flexneri 2b, and S. flexneri 1b. CONCLUSIONS: A broad-spectrum Shigella Vaccine must protect against S. sonnei and 15 S. flexneri serotypes/subserotypes. A quadrivalent Vaccine with O antigens from S. sonnei, S. flexneri 2a, S. flexneri 3a, and S. flexneri 6 can provide broad direct coverage against these most common serotypes and indirect coverage against all but 1 (rare) remaining subserotype through shared S. flexneri group antigens.

  • gut homing conventional plasmablasts and cd27 plasmablasts elicited after a short time of exposure to an oral live attenuated Shigella Vaccine candidate in humans
    Frontiers in Immunology, 2014
    Co-Authors: Franklin R Toapanta, Eileen M. Barry, Karen L. Kotloff, Marcela F Pasetti, Jakub K Simon, Myron M Levine, Marcelo B Sztein
    Abstract:

    Currently, there is no licensed Shigella Vaccine; however, various promising live attenuated Vaccine candidates have emerged, including CVD1208S (ΔguaBA, Δset, Δsen S. flexneri 2a), which was shown to be safe and immunogenic in Phase 1 clinical trials. Here we report the immune responses elicited in an outpatient Phase 2 clinical trial in which subjects were vaccinated with CVD 1208S. Oral immunization with CVD 1208S elicited high anti-S. flexneri 2a LPS and IpaB antibody responses, as well as an acute plasmablast (PB) infiltration in peripheral blood 7 days after immunization. PB sorted based on their expression of homing molecules confirmed that cells expressing integrin α4β7 alone or in combination with CD62L were responsible for antibody production (as measured by ELISpot). Furthermore, using high-color flow-cytometry, on day 7 after immunization, we observed the appearance of conventional PB (CPB, CD19dim CD20- CD27+high CD38+high CD3-), as well as a PB population that did not express CD27 (CD27- PB; pre-plasmablasts). The pattern of individual or simultaneous expression of homing markers (integrin α4β7, CD62L, CXCR3 and CXCR4) suggested that CPB cells homed preferentially to the inflamed gut mucosa. In contrast, ~50% CD27- PB cells appear to home to yet to be identified peripheral lymphoid organs or were in a transition state preceding integrin α4β7 upregulation. In sum, these observations demonstrate that strong immune responses, including distinct PB subsets with the potential to home to the gut and other secondary lymphoid organs, can be elicited after a short time of exposure to a Shigella oral

  • progress and pitfalls in Shigella Vaccine research
    Nature Reviews Gastroenterology & Hepatology, 2013
    Co-Authors: Eileen M. Barry, Karen L. Kotloff, Marcela F Pasetti, Marcelo B Sztein, Alessio Fasano, Myron M Levine
    Abstract:

    Shigella infection continues to have a high disease burden worldwide, especially in young children in developing countries. Here, the latest progress in Shigella Vaccine research is reviewed—including the identification of new Vaccine antigens and technological advances in Vaccine design and manufacture—as well as the barriers that impede the development of a successful Shigella Vaccine.

Marcelo B Sztein - One of the best experts on this subject based on the ideXlab platform.

  • a clinically parameterized mathematical model of Shigella immunity to inform Vaccine design
    PLOS ONE, 2018
    Co-Authors: Courtney L Davis, Jakub K Simon, Franklin R Toapanta, Rezwanul Wahid, Marcelo B Sztein
    Abstract:

    We refine and clinically parameterize a mathematical model of the humoral immune response against Shigella, a diarrheal bacteria that infects 80-165 million people and kills an estimated 600,000 people worldwide each year. Using Latin hypercube sampling and Monte Carlo simulations for parameter estimation, we fit our model to human immune data from two Shigella EcSf2a-2 Vaccine trials and a rechallenge study in which antibody and B-cell responses against Shigella′s lipopolysaccharide (LPS) and O-membrane proteins (OMP) were recorded. The clinically grounded model is used to mathematically investigate which key immune mechanisms and bacterial targets confer immunity against Shigella and to predict which humoral immune components should be elicited to create a protective Vaccine against Shigella. The model offers insight into why the EcSf2a-2 Vaccine had low efficacy and demonstrates that at a group level a humoral immune response induced by EcSf2a-2 Vaccine or wild-type challenge against Shigella′s LPS or OMP does not appear sufficient for protection. That is, the model predicts an uncontrolled infection of gut epithelial cells that is present across all best-fit model parameterizations when fit to EcSf2a-2 Vaccine or wild-type challenge data. Using sensitivity analysis, we explore which model parameter values must be altered to prevent the destructive epithelial invasion by Shigella bacteria and identify four key parameter groups as potential Vaccine targets or immune correlates: 1) the rate that Shigella migrates into the lamina propria or epithelium, 2) the rate that memory B cells (BM) differentiate into antibody-secreting cells (ASC), 3) the rate at which antibodies are produced by activated ASC, and 4) the Shigella-specific BM carrying capacity. This paper underscores the need for a multifaceted approach in ongoing efforts to design an effective Shigella Vaccine.

  • gut homing conventional plasmablasts and cd27 plasmablasts elicited after a short time of exposure to an oral live attenuated Shigella Vaccine candidate in humans
    Frontiers in Immunology, 2014
    Co-Authors: Franklin R Toapanta, Eileen M. Barry, Karen L. Kotloff, Marcela F Pasetti, Jakub K Simon, Myron M Levine, Marcelo B Sztein
    Abstract:

    Currently, there is no licensed Shigella Vaccine; however, various promising live attenuated Vaccine candidates have emerged, including CVD1208S (ΔguaBA, Δset, Δsen S. flexneri 2a), which was shown to be safe and immunogenic in Phase 1 clinical trials. Here we report the immune responses elicited in an outpatient Phase 2 clinical trial in which subjects were vaccinated with CVD 1208S. Oral immunization with CVD 1208S elicited high anti-S. flexneri 2a LPS and IpaB antibody responses, as well as an acute plasmablast (PB) infiltration in peripheral blood 7 days after immunization. PB sorted based on their expression of homing molecules confirmed that cells expressing integrin α4β7 alone or in combination with CD62L were responsible for antibody production (as measured by ELISpot). Furthermore, using high-color flow-cytometry, on day 7 after immunization, we observed the appearance of conventional PB (CPB, CD19dim CD20- CD27+high CD38+high CD3-), as well as a PB population that did not express CD27 (CD27- PB; pre-plasmablasts). The pattern of individual or simultaneous expression of homing markers (integrin α4β7, CD62L, CXCR3 and CXCR4) suggested that CPB cells homed preferentially to the inflamed gut mucosa. In contrast, ~50% CD27- PB cells appear to home to yet to be identified peripheral lymphoid organs or were in a transition state preceding integrin α4β7 upregulation. In sum, these observations demonstrate that strong immune responses, including distinct PB subsets with the potential to home to the gut and other secondary lymphoid organs, can be elicited after a short time of exposure to a Shigella oral

  • effect of wild type Shigella species and attenuated Shigella Vaccine candidates on small intestinal barrier function antigen trafficking and cytokine release
    PLOS ONE, 2014
    Co-Authors: Maria Fiorentino, Marcelo B Sztein, Myron M Levine, Alessio Fasano
    Abstract:

    Bacterial dysentery due to Shigella species is a major cause of morbidity and mortality worldwide. The pathogenesis of Shigella is based on the bacteria's ability to invade and replicate within the colonic epithelium, resulting in severe intestinal inflammatory response and epithelial destruction. Although the mechanisms of pathogenesis of Shigella in the colon have been extensively studied, little is known on the effect of wild-type Shigella on the small intestine and the role of the host response in the development of the disease. Moreover, to the best of our knowledge no studies have described the effects of apically administered Shigella flexneri 2a and S. dysenteriae 1 Vaccine strains on human small intestinal enterocytes. The aim of this study was to assess the coordinated functional and immunological human epithelial responses evoked by strains of Shigella and candidate Vaccines on small intestinal enterocytes. To model the interactions of Shigella with the intestinal mucosa, we apically exposed monolayers of human intestinal Caco2 cells to increasing bacterial inocula. We monitored changes in paracellular permeability, examined the organization of tight-junctions and the pro-inflammatory response of epithelial cells. Shigella infection of Caco2 monolayers caused severe mucosal damage, apparent as a drastic increase in paracellular permeability and disruption of tight junctions at the cell-cell boundary. Secretion of pro-inflammatory IL-8 was independent of epithelial barrier dysfunction. Shigella Vaccine strains elicited a pro-inflammatory response without affecting the intestinal barrier integrity. Our data show that wild-type Shigella infection causes a severe alteration of the barrier function of a small intestinal cell monolayer (a proxy for mucosa) and might contribute (along with enterotoxins) to the induction of watery diarrhea. Diarrhea may be a mechanism by which the host attempts to eliminate harmful bacteria and transport them from the small to the large intestine where they invade colonocytes inducing a strong inflammatory response.

  • applying mathematical tools to accelerate Vaccine development modeling Shigella immune dynamics
    PLOS ONE, 2013
    Co-Authors: Courtney L Davis, Jakub K Simon, Marcelo B Sztein, Franklin R Toapanta, Rezwanul Wahid, Doron Levy
    Abstract:

    We establish a mathematical framework for studying immune interactions with Shigella, a bacteria that kills over one million people worldwide every year. The long-term goal of this novel approach is to inform Shigella Vaccine design by elucidating which immune components and bacterial targets are crucial for establishing Shigella immunity. Our delay differential equation model focuses on antibody and B cell responses directed against antigens like lipopolysaccharide in Shigella’s outer membrane. We find that antibody-based Vaccines targeting only surface antigens cannot elicit sufficient immunity for protection. Additional boosting prior to infection would require a four-orders-of-magnitude increase in antibodies to sufficiently prevent epithelial invasion. However, boosting anti-LPS B memory can confer protection, which suggests these cells may correlate with immunity. We see that IgA antibodies are slightly more effective per molecule than IgG, but more total IgA is required due to spatial functionality. An extension of the model reveals that targeting both LPS and epithelial entry proteins is a promising avenue to advance Vaccine development. This paper underscores the importance of multifaceted immune targeting in creating an effective Shigella Vaccine. It introduces mathematical models to the Shigella Vaccine development effort and lays a foundation for joint theoretical/experimental/clinical approaches to Shigella Vaccine design.

  • progress and pitfalls in Shigella Vaccine research
    Nature Reviews Gastroenterology & Hepatology, 2013
    Co-Authors: Eileen M. Barry, Karen L. Kotloff, Marcela F Pasetti, Marcelo B Sztein, Alessio Fasano, Myron M Levine
    Abstract:

    Shigella infection continues to have a high disease burden worldwide, especially in young children in developing countries. Here, the latest progress in Shigella Vaccine research is reviewed—including the identification of new Vaccine antigens and technological advances in Vaccine design and manufacture—as well as the barriers that impede the development of a successful Shigella Vaccine.

Ryan T Ranallo - One of the best experts on this subject based on the ideXlab platform.

  • development of an aotus nancymaae model for Shigella Vaccine immunogenicity and efficacy studies
    Infection and Immunity, 2014
    Co-Authors: Michael Gregory, Robert W. Kaminski, Ryan T Ranallo, Luis A Lugoroman, Hugo Galvez Carrillo, Drake H Tilley, Christian G Baldeviano, Mark P Simons, Nathanael D Reynolds, Akamol E Suvarnapunya
    Abstract:

    Several animal models exist to evaluate the immunogenicity and protective efficacy of candidate Shigella Vaccines. The two most widely used nonprimate models for Vaccine development include a murine pulmonary challenge model and a guinea pig keratoconjunctivitis model. Nonhuman primate models exhibit clinical features and gross and microscopic colonic lesions that mimic those induced in human shigellosis. Challenge models for enterotoxigenic Escherichia coli (ETEC) and Campylobacter spp. have been successfully developed with Aotus nancymaae, and the addition of a Shigella-Aotus challenge model would facilitate the testing of combination Vaccines. A series of experiments were designed to identify the dose of Shigella flexneri 2a strain 2457T that induces an attack rate of 75% in the Aotus monkey. After primary challenge, the dose required to induce an attack rate of 75% was calculated to be 1 × 1011 CFU. Shigella-specific immune responses were low after primary challenge and subsequently boosted upon rechallenge. However, preexisting immunity derived from the primary challenge was insufficient to protect against the homologous Shigella serotype. A successive study in A. nancymaae evaluated the ability of multiple oral immunizations with live-attenuated Shigella Vaccine strain SC602 to protect against challenge. After three oral immunizations, animals were challenged with S. flexneri 2a 2457T. A 70% attack rate was demonstrated in control animals, whereas animals immunized with Vaccine strain SC602 were protected from challenge (efficacy of 80%; P = 0.05). The overall study results indicate that the Shigella-Aotus nancymaae challenge model may be a valuable tool for evaluating Vaccine efficacy and investigating immune correlates of protection.

  • oral administration of live Shigella Vaccine candidates in rhesus monkeys show no evidence of competition for colonization and immunogenicity between different serotypes
    Vaccine, 2014
    Co-Authors: Ryan T Ranallo, Robert W. Kaminski, Shoshana Barnoy, Tara L Boren, Shahida Baqar, M Dutta, L A Lugoroman, Malabi M Venkatesan
    Abstract:

    Live oral monovalent Shigella flexneri 2a Vaccine candidates as well as bivalent formulations with Shigella sonnei were evaluated in a rhesus monkey model for colonization and immunogenicity. Freshly harvested suspensions of S. flexneri 2a Vaccine candidates WRSf2G12 and WRSf2G15 as well as S. sonnei Vaccine candidate WRSs3 were nasogastrically administered to groups of rhesus monkeys, Macaca mulatta, either in a monovalent form or when combined with each other. The animals were monitored daily for physical well-being, stools were subjected to quantitative colony immunoblot assays for bacterial excretion and blood and stools were evaluated for humoral and mucosal immune responses. No clinical symptoms were noted in any group of animals and the Vaccine candidates were excreted robustly for 48–72 h without significant changes in either the magnitude or duration of excretion when given as a monovalent or as bivalent mixtures. Similarly, immunological interferences were not apparent in the magnitude of humoral and mucosal immune responses observed toward Shigella-specific antigens when monkeys were fed monovalent or bivalent formulations. These results predict that a multivalent live oral Vaccine of more than one serotype can have a favorable outcome for protection against shigellosis.

  • two live attenuated Shigella flexneri 2a strains wrsf2g12 and wrsf2g15 a new combination of gene deletions for 2nd generation live attenuated Vaccine candidates
    Vaccine, 2012
    Co-Authors: Ryan T Ranallo, Robert W. Kaminski, Sejal Thakkar, Suramya Fonseka, Tara L Boren, Lisa Bedford, Malabi M Venkatesan
    Abstract:

    Shigella infections are a major cause of inflammatory diarrhea and dysentery worldwide. First-generation virG-based live attenuated Shigella strains have been successfully tested in phase I and II clinical trials and are a leading approach for Shigella Vaccine development. Additional gene deletions in senA, senB and msbB2 have been engineered into second-generation virG-based Shigella flexneri 2a strains producing WRSf2G12 and WRSf2G15. Both strains harbor a unique combination of gene deletions designed to increase the safety of live Shigella Vaccines. WRSf2G12 and WRSf2G15 are genetically stable and highly attenuated in both cell culture and animal models of infection. Ocular immunization of guinea pigs with either strain induces robust systemic and mucosal immune responses that protect against homologous challenge with wild-type Shigella. The data support further evaluation of the second-generation strains in a phase I clinical trial.

  • characterization of wrss2 and wrss3 new second generation virg icsa based Shigella sonnei Vaccine candidates with the potential for reduced reactogenicity
    Vaccine, 2010
    Co-Authors: Shoshana Barnoy, Ryan T Ranallo, Akamol E Suvarnapunya, Kwangil Jeong, Richard F Helm, Saul Tzipori, Malabi M Venkatesan
    Abstract:

    Live, attenuated Shigella Vaccine candidates, such as Shigella sonnei strain WRSS1, Shigella flexneri 2a strain SC602, and Shigella dysenteriae 1 strain WRSd1, are attenuated principally by the loss of the VirG(IcsA) protein. These candidates have proven to be safe and immunogenic in volunteer trials and in one study, efficacious against shigellosis. One drawback of these candidate Vaccines has been the reactogenic symptoms of fever and diarrhea experienced by the volunteers, that increased in a dose-dependent manner. New, second-generation virG(icsA)-based S. sonnei Vaccine candidates, WRSs2 and WRSs3, are expected to be less reactogenic while retaining the ability to generate protective levels of immunogenicity seen with WRSS1. Besides the loss of VirG(IcsA), WRSs2 and WRSs3 also lack plasmid-encoded enterotoxin ShET2-1 and its paralog ShET2-2. WRSs3 further lacks MsbB2 that reduces the endotoxicity of the lipid A portion of the bacterial LPS. Studies in cell cultures and in gnotobiotic piglets demonstrate that WRSs2 and WRSs3 have the potential to cause less diarrhea due to loss of ShET2-1 and ShET2-2 as well as alleviate febrile symptoms by loss of MsbB2. In guinea pigs, WRSs2 and WRSs3 were as safe, immunogenic and efficacious as WRSS1.

  • immunogenicity and characterization of wrsf2g11 a second generation live attenuated Shigella flexneri 2a Vaccine strain
    Vaccine, 2007
    Co-Authors: Ryan T Ranallo, Sejal Thakkar, Qing Chen, Malabi M Venkatesan
    Abstract:

    Abstract Recent clinical trials involving live attenuated Shigella Vaccine strains SC602 and WRSS1 have revealed that deletion of the virG ( icsA ) gene dramatically reduces virulence in human volunteers. These strains can be given at low oral doses and induce a strong, and in some cases, protective immune responses. However, residual Vaccine associated reactogenicity suggests that further attenuation is required. A recent clinical trial indicated that the set and sen enterotoxin genes contribute to the symptoms of fever and diarrhea observed with live Shigella Vaccine strains. Based on these findings, a Shigella flexneri 2a Vaccine candidate, WRSf2G11, with deletions in the virG ( icsA ), set and sen genes has been constructed using the lambda red recombinase system. The immunogenicity and protective efficacy of WRSf2G11 compares favorably with SC602 following either intranasal (IN) or ocular (OC) immunization of guinea pigs. Taken together, these data indicate that second generation virG -based Shigella Vaccine strains which lack enterotoxin genes, such as WRSf2G11, will likely show lower levels of reactogenicity without hampering the robust immune responses achieved with previous live Vaccines.