Role of Toll-Like Receptor 4 in the Proinflammatory Response to
            <i>Vibrio cholerae</i>
            O1 El Tor Strains Deficient in Production of Cholera Toxin and Accessory Toxins

Haines, G. Kenneth; Sayed, Blayne A.; Rohrer, Melissa S.; Olivier, Verena; Satchell, K.J.F.

doi:10.1128/iai.73.9.6157-6164.2005

Cited by 23 publications

(29 citation statements)

References 29 publications

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“…Toll-like receptor 4 (TLR4) can be activated by V. cholerae LPS in vitro (18). Also, after nasal infection with V. cholerae lacking proinflammatory toxins CTX, RtxA, and HlyA, morbidity was greater for mice lacking TLR4 expression, suggesting a role for TLR4-mediated inflammation in bacterial containment in the absence of other sources of inflammation (23). Using human epithelial cell lines, TLR5 was implicated in V. cholerae flagellin-induced inflammation (14,15), although the sheath covering the V. cholerae flagellum reduces the potency of TLR5 signaling (24).…”

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confidence: 99%

Vibrio cholerae-Induced Inflammation in the Neonatal Mouse Cholera Model

2014

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Vibrio cholerae is the causative agent of the acute diarrheal disease of cholera. Innate immune responses to V. cholerae are not a major cause of cholera pathology, which is characterized by severe, watery diarrhea induced by the action of cholera toxin. Innate responses may, however, contribute to resolution of infection and must be required to initiate adaptive responses after natural infection and oral vaccination. Here we investigated whether a well-established infant mouse model of cholera can be used to observe an innate immune response. We also used a vaccination model in which immunized dams protect their pups from infection through breast milk antibodies to investigate innate immune responses after V. cholerae infection for pups suckled by an immune dam. At the peak of infection, we observed neutrophil recruitment accompanied by induction of KC, macrophage inflammatory protein 2 (MIP-2), NOS-2, interleukin-6 (IL-6), and IL-17a. Pups suckled by an immunized dam did not mount this response. Accessory toxins RtxA and HlyA played no discernible role in neutrophil recruitment in a wild-type background. The innate response to V. cholerae deleted for cholera toxin-encoding phage (CTX) and part of rtxA was significantly reduced, suggesting a role for CTX-carried genes or for RtxA in the absence of cholera toxin (CTX). Two extracellular V. cholerae DNases were not required for neutrophil recruitment, but DNase-deficient V. cholerae caused more clouds of DNA in the intestinal lumen, which appeared to be neutrophil extracellular traps (NETs), suggesting that V. cholerae DNases combat NETs. Thus, the infant mouse model has hitherto unrecognized utility for interrogating innate responses to V. cholerae infection. Vibrio cholerae is the causative agent of cholera, which remains endemic in many regions of Africa and Asia (1). Sporadic outbreaks can devastate immunologically naïve populations, such as occurred in Haiti in 2010 (2). The O1 serogroup and, to a lesser degree, O139 are the major causes of cholera, and El Tor is currently the circulating O1 biotype (1). Cholera toxin (CTX), encoded by a lysogenic phage (3), is the major cause of the severe secretory diarrhea that is typical of cholera. Without rehydration therapy, cholera results in 25 to 50% mortality, but if treated, cholera will resolve in most patients (4). Unlike diseases such as shigellosis and Salmonella-induced gastroenteritis (5, 6), the pathology of cholera is not immune driven. However, innate immune responses have been observed in cholera patients during the acute phase of infection (7) and likely play a direct and/or indirect role in the resolution of disease. The majority of individuals who survive a bout of cholera will become immune to subsequent infection for at least 3 years (8-10), and some aspects of the observed innate immune response must be required to initiate this protective immunity.Many live attenuated vaccine candidate strains of V. cholerae have been developed in which ctxA, the gene encoding the catalytic subunit of cholera tox...

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Vibrio cholerae-Induced Inflammation in the Neonatal Mouse Cholera Model

2014

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“…In an infant rabbit model of infection, this diarrhea has been specifically linked to expression of flagellin that may be functioning by increasing inflammatory signaling through TLR5 (20,46,47). Studies using lung infection in mice have also linked proinflammatory signaling from CT-negative strains to LPS-dependent signaling through TLR4 (18), whereas lipoprotein has been shown in vitro to stimulate inflammation via TLR1/TLR2 (16,25). Thus, the prevailing models suggest that bacterial factors induce a proinflammatory response that then causes significant diarrhea, resulting in either serious clinical symptoms during natural infection with nontoxigenic strains or reactogenic symptoms in vaccine studies.…”

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Neutrophils Are Essential for Containment of Vibrio cholerae to the Intestine during the Proinflammatory Phase of Infection

Queen

Satchell

2012

Infect Immun

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Cholera is classically considered a noninflammatory diarrheal disease, in comparison to invasive enteric organisms, although there is a low-level proinflammatory response during early infection with Vibrio cholerae and a strong proinflammatory reaction to live attenuated vaccine strains. Using an adult mouse intestinal infection model, this study examines the contribution of neutrophils to host defense to infection. Nontoxigenic El Tor O1 V. cholerae infection is characterized by the upregulation of interleukin-6 (IL-6), IL-10, and macrophage inflammatory protein 2 alpha in the intestine, indicating an acute innate immune response. Depletion of neutrophils from mice with anti-Ly6G IA8 monoclonal antibody led to decreased survival of mice. The role of neutrophils in protection of the host is to limit the infection to the intestine and control bacterial spread to extraintestinal organs. In the absence of neutrophils, the infection spread to the spleen and led to increased systemic levels of IL-1␤ and tumor necrosis factor alpha, suggesting the decreased survival in neutropenic mice is due to systemic shock. Neutrophils were found not to contribute to either clearance of colonizing bacteria or to alter the local immune response. However, when genes for secreted accessory toxins were deleted, the colonizing bacteria were cleared from the intestine, and this clearance is dependent upon neutrophils. Thus, the requirement for accessory toxins in virulence is negated in neutropenic mice, which is consistent with a role of accessory toxins in the evasion of innate immune cells in the intestine. Overall, these data support that neutrophils impact disease progression and suggest that neutrophil effectiveness can be manipulated through the deletion of accessory toxins. G lobal pandemics of the diarrheal disease cholera have occurred throughout human history. The disease is caused by ingestion of the Gram-negative bacterium Vibrio cholerae in contaminated water. Cholera is typified by symptoms of severe, watery diarrhea that leads to life-threatening dehydration and loss of electrolytes (48). There have been seven cholera pandemics in recorded history. The first six were caused by V. cholerae O1 of the classical biotype. The seventh and currently ongoing pandemic began in 1961, when V. cholerae O1 strains of the El Tor biotype began to predominate and spread throughout the world (22). Recent whole-genome analysis of single-nucleotide polymorphisms revealed that the seventh pandemic consists of three distinct waves of transmission from the pandemic center in South Asia. Strain diversification has resulted from continuous local evolution punctuated by sporadic long-range transmission to countries where this pathogen is not endemic, such as in the case of Haiti in 2010 (34). It is estimated that 1.4 billion people worldwide are at risk for cholera, with approximately 2.8 million cholera cases occurring in areas of endemicity each year (1).The innate immune response to V. cholerae infection is poorly understood. Recent studies i...

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“…However, little is known about their role in vivo as no overt defects in mutants in relevant animal models have been observed. A role for accessory toxins in pathogenesis in a pulmonary infection model was indicated previously (12,16); however, as the lung is not the natural site of infection, the relevance of these studies was questioned. In this study, we established a new model for the intestinal infection of 4-to 6-week-old C57BL/6 mice with V. cholerae.…”

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“…Indeed, a strain in which the genes for CT and all three accessory toxins were deleted was avirulent after intranasal infection, and the colonizing bacteria were cleared from the lung (12). Yet this multitoxin-deficient strain stimulated the innate immune response in a classical fashion through multiple pathways both dependent upon and independent of Toll-like receptor 4 (16). These results suggested that accessory toxins function coordinately to enable the bacteria to evade the host immune response and prevent clearance of the colonizing bacteria during the early stages of infection.…”

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confidence: 99%

“…As further barriers to the use of infant mice for the study of accessory toxins, the intestines are not fully developed, either anatomically or immunologically, and experiments are often limited to less than 24 h since animals are removed from their mothers' care (10,17,23). Thus, infant mice are not ideal for analyses of alterations in host immune responses, tissue damage, or long-term colonization-all processes that may be affected by the accessory toxins (14,16).…”

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Prolonged Colonization of Mice by Vibrio cholerae El Tor O1 Depends on Accessory Toxins

2007

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Cholera epidemics caused by Vibrio cholerae El Tor O1 strains are typified by a large number of asymptomatic carriers who excrete vibrios but do not develop diarrhea. This carriage state was important for the spread of the seventh cholera pandemic as the bacterium was mobilized geographically, allowing the global dispersion of this less virulent strain. Virulence factors associated with the development of the carriage state have not been previously identified. We have developed an animal model of cholera in adult C57BL/6 mice wherein V. cholerae colonizes the mucus layer and forms microcolonies in the crypts of the distal small bowel. Colonization occurred 1 to 3 h after oral inoculation and peaked at 10 to 12 h, when bacterial loads exceeded the inoculum by 10-to 200-fold, indicating bacterial growth within the small intestine. After a clearance phase, the number of bacteria within the small intestine, but not those in the cecum or colon, stabilized and persisted for at least 72 h. The ability of V. cholerae to prevent clearance and establish this prolonged colonization was associated with the accessory toxins hemolysin, the multifunctional autoprocessing RTX toxin, and hemagglutinin/protease and did not require cholera toxin or toxin-coregulated pili. The defect in colonization attributed to the loss of the accessory toxins may be extracellularly complemented by inoculation of the defective strain with an isogenic colonization-proficient V. cholerae strain. This work thus demonstrates that secreted accessory toxins modify the host environment to enable prolonged colonization of the small intestine in the absence of overt disease symptoms and thereby contribute to disease dissemination via asymptomatic carriers.

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Role of Toll-Like Receptor 4 in the Proinflammatory Response to Vibrio cholerae O1 El Tor Strains Deficient in Production of Cholera Toxin and Accessory Toxins

Cited by 23 publications

References 29 publications

Vibrio cholerae-Induced Inflammation in the Neonatal Mouse Cholera Model

Vibrio cholerae-Induced Inflammation in the Neonatal Mouse Cholera Model

Neutrophils Are Essential for Containment of Vibrio cholerae to the Intestine during the Proinflammatory Phase of Infection

Prolonged Colonization of Mice by Vibrio cholerae El Tor O1 Depends on Accessory Toxins

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