Progress and pitfalls in Shigella vaccine research
University of Maryland School of Medicine, Center for Vaccine Development, 685 West Baltimore Street, HSF 480, Baltimore, MD 21201, USA. Nature Reviews Gastroenterology & Hepatology
(Impact Factor: 12.61).
02/2013; 10(4). DOI: 10.1038/nrgastro.2013.12
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.
Available from: journal.frontiersin.org
- "are highly adapted human pathogens that cause shigellosis, a disease that provokes severe bloody and mucous diarrhea, which still remains a major public health concern in developing countries. No safe and effective Shigella vaccine currently exists, and antibiotic-resistant bacteria have recently been observed, increasing the threat of outbreaks due to lack of effective treatments (Barry et al., 2013). Therefore, there is an urgent need to understand the interplay between bacterial infection and host cellular and immune responses in order to develop safe and effective Shigella vaccines or novel treatment. "
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ABSTRACT: Shigella spp. are highly adapted human pathogens that cause bacillary dysentery (shigellosis). Via the type III secretion system (T3SS), Shigella deliver a subset of virulence proteins (effectors) that are responsible for pathogenesis, with functions including pyroptosis, invasion of the epithelial cells, intracellular survival, and evasion of host immune responses. Intriguingly, T3SS effector activity and strategies are not unique to Shigella, but are shared by many other bacterial pathogens, including Salmonella, Yersinia, and enteropathogenic Escherichia coli (EPEC). Therefore, studying Shigella T3SS effectors will not only improve our understanding of bacterial infection systems, but also provide a molecular basis for developing live bacterial vaccines and antibacterial drugs. One of Shigella T3SS effectors, IpaH family proteins, which have E3 ubiquitin ligase activity and are widely conserved among other bacterial pathogens, are very relevant because they promote bacterial survival by triggering cell death and modulating the host immune responses. Here, we describe selected examples of Shigella pathogenesis, with particular emphasis on the roles of IpaH family effectors, which shed new light on bacterial survival strategies and provide clues about how to overcome bacterial infections.
Available from: Didier Hocquet
- "Dysentery caused by Shigella dysenteriae type 1 (Sd1) is a recurrent challenge in many parts of the world. Epidemics of this disease are associated with a high rate of mortality in young children
. Treatment is complicated by the rapid emergence of Sd1 strains resistant to the newest antibiotics
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Shigella dysenteriae type 1 (Sd1) causes recurrent epidemics of dysentery associated with high mortality in many regions of the world. Sd1 infects humans at very low infectious doses (10 CFU), and treatment is complicated by the rapid emergence of antibiotic resistant Sd1 strains. Sd1 is only detected in the context of human infections, and the circumstances under which epidemics emerge and regress remain unknown.
Phylogenomic analyses of 56 isolates collected worldwide over the past 60 years indicate that the Sd1 clone responsible for the recent pandemics emerged at the turn of the 20th century, and that the two world wars likely played a pivotal role for its dissemination. Several lineages remain ubiquitous and their phylogeny indicates several recent intercontinental transfers. Our comparative genomics analysis reveals that isolates responsible for separate outbreaks, though closely related to one another, have independently accumulated antibiotic resistance genes, suggesting that there is little or no selection to retain these genes in-between outbreaks. The genomes appear to be subjected to genetic drift that affects a number of functions currently used by diagnostic tools to identify Sd1, which could lead to the potential failure of such tools.
Taken together, the Sd1 population structure and pattern of evolution suggest a recent emergence and a possible human carrier state that could play an important role in the epidemic pattern of infections of this human-specific pathogen. This analysis highlights the important role of whole-genome sequencing in studying pathogens for which epidemiological or laboratory investigations are particularly challenging.
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The online version of this article (doi: 10.1186/1471-2164-15-355) contains supplementary material, which is available to authorized users.
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ABSTRACT: Shigella species Gram-negative bacteria which cause a diarrheal disease, known as shigellosis, by invading and destroying the colonic
mucosa and inducing a robust inflammatory response. With no vaccine available, shigellosis annually kills over 600,000 children
in developing countries. This study demonstrates the utility of combining high-throughput bioinformatic methods with in vitro and in vivo assays to provide new insights into pathogenesis. Comparisons of in vivo and in vitro gene expression identified genes associated with intracellular growth. Additional bioinformatics analyses identified genes
that are present in S. flexneri isolates but not in the three other Shigella species. Comparison of these two analyses revealed nine genes that are differentially expressed during invasion and that
are specific to S. flexneri. One gene, a DeoR family transcriptional regulator with decreased expression during invasion, was further characterized and
is now designated icgR, for intracellular growth regulator. Deletion of icgR caused no difference in growth in vitro but resulted in increased intracellular replication in HCT-8 cells. Further in vitro and in vivo studies using high-throughput sequencing of RNA transcripts (RNA-seq) of an isogenic ΔicgR mutant identified 34 genes that were upregulated under both growth conditions. This combined informatics and functional approach
has allowed the characterization of a gene and pathway previously unknown in Shigella pathogenesis and provides a framework for further identification of novel virulence factors and regulatory pathways.
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