Interleukin-15 and NK1.1+ Cells Provide Innate Protection against Acute Salmonella enterica Serovar Typhimurium Infection in the Gut and in Systemic Tissues

ABSTRACT Control of bacterial colonization at mucosal surfaces depends on rapid activation of the innate immune system. Interleukin-15 (IL-15) directs the development, maturation, and function of a population of cells positive for NK1.1, such as natural killer (NK) cells, which are critical components of the innate immune defense against several viral and bacterial pathogens. Using IL-15-deficient mice, in vivo depletion of NK1.1+ cells from wild-type mice, and in vivo overexpression of IL-15 from a recombinant adenovirus, we tested the role of IL-15 and NK1.1+ cells in innate protection of the murine gut and reticuloendothelial system from Salmonella enterica serovar Typhimurium infection. IL-15 and the NK1.1+ cell population provided innate protection from serovar Typhimurium in mice at the enteric mucosae and in the reticuloendothelial system during murine typhoid. Interestingly, serovar Typhimurium extensively colonized the gut of IL-15−/− mice and wild-type C57BL/6 mice depleted of NK1.1+ cells prior to infection, even though the animals were not pretreated with antibiotics to reduce colonization resistance and there was an absence of overt inflammation in the colon and cecum. Enhanced dissemination of Salmonella from the gut of mice depleted of NK1.1+ cells correlated with a localized disruption of IL-17 in the colon. These data suggest a relationship between the gut ecosystem and the innate mucosal immune system, which may be linked via IL-15 and NK1.1+ cells.

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Novel Salmonella enterica Serovar Typhimurium Protein That Is Indispensable for Virulence and Intracellular Replication

Infection and Immunity ◽

10.1128/iai.69.12.7413-7418.2001 ◽

2001 ◽

Vol 69 (12) ◽

pp. 7413-7418 ◽

Cited By ~ 11

Author(s):

Tahar van der Straaten ◽

Angela van Diepen ◽

Kitty Kwappenberg ◽

Sjaak van Voorden ◽

Kees Franken ◽

...

Keyword(s):

Amino Acid ◽

Protein Function ◽

Salmonella Enterica ◽

Host Cells ◽

Wild Type ◽

Intracellular Replication ◽

Oxygen Intermediates ◽

Serovar Typhimurium

ABSTRACT Upon contact with host cells, the intracellular pathogenSalmonella enterica serovar Typhimurium promotes its uptake, targeting, and survival in intracellular niches. In this process, the bacterium evades the microbicidal effector mechanisms of the macrophage, including oxygen intermediates. This study reports the phenotypic and genotypic characterization of an S. enterica serovar Typhimurium mutant that is hypersusceptible to superoxide. The susceptible phenotype is due to a MudJ insertion-inactivation of a previously undescribedSalmonella gene designated sspJ that is located between 54.4 and 64 min of the Salmonellachromosome and encodes a 392-amino-acid protein. In vivo, upon intraperitoneal injection of 104 to 107bacteria in C3H/HeN and 101 to 104 bacteria in BALB/c mice, the mutant strain was less virulent than the wild type. Consistent with this finding, during the first hour after ingestion by macrophage-like J774 and RAW264.7 cells in vitro, the intracellular killing of the strain carrying sspJ::MudJ is enhanced fivefold over that of wild-type microorganisms. Wild-type salmonellae displayed significant intracellular replication during the first 24 h after uptake, but sspJ::MudJ mutants failed to do so. This phenotype could be restored to that of the wild type by sspJ complementation. The SspJ protein is found in the cytoplasmic membrane and periplasmic space. Amino acid sequence homology analysis did reveal a leader sequence and putative pyrroloquinoline quinone-binding domains, but no putative protein function. We excluded the possibility that SspJ is a scavenger of superoxide or has superoxide dismutase activity.

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Interaction of Antibiotics with Innate Host Defense Factors against Salmonella enterica Serotype Newport

mSphere ◽

10.1128/msphere.00410-17 ◽

2017 ◽

Vol 2 (6) ◽

Cited By ~ 15

Author(s):

George Sakoulas ◽

Monika Kumaraswamy ◽

Armin Kousha ◽

Victor Nizet

Keyword(s):

Innate Immunity ◽

Immune System ◽

Innate Immune System ◽

Salmonella Enterica ◽

Clinical Performance ◽

Innate Immune ◽

Content Type ◽

Antimicrobial Assay

ABSTRACT It is becoming increasingly understood that the current paradigms of in vitro antimicrobial susceptibility testing may have significant shortcomings in predicting activity in vivo. This study evaluated the activity of several antibiotics alone and in combination against clinical isolates of Salmonella enterica serotype Newport (meningitis case) utilizing both conventional and physiological media. In addition, the interactions of these antibiotics with components of the innate immune system were evaluated. Azithromycin, which has performed quite well clinically despite high MICs in conventional media, was shown to be more active in physiological media and to enhance innate immune system killing. Alternatively, chloramphenicol did not show enhanced immune system killing, paralleling its inferior clinical performance to other antibiotics that have been used to treat Salmonella meningitis. These findings are important additions to the building understanding of current in vitro antimicrobial assay limitations that hopefully will amount to future improvements in these assays to better predict clinical efficacy and activity in vivo. This study examines the pharmacodynamics of antimicrobials that are used to treat Salmonella with each other and with key components of the innate immune system. Antimicrobial synergy was assessed using time-kill and checkerboard assays. Antimicrobial interactions with innate immunity were studied by employing cathelicidin LL-37, whole-blood, and neutrophil killing assays. Ceftriaxone and ciprofloxacin were found to be synergistic in vitro against Salmonella enterica serotype Newport. Ceftriaxone, ciprofloxacin, and azithromycin each demonstrated synergy with the human cathelicidin defense peptide LL-37 in killing Salmonella. Exposure of Salmonella to sub-MICs of ceftriaxone resulted in enhanced susceptibility to LL-37, whole blood, and neutrophil killing. The activity of antibiotics in vivo against Salmonella may be underestimated in bacteriologic media lacking components of innate immunity. The pharmacodynamic interactions of antibiotics used to treat Salmonella with each other and with components of innate immunity warrant further study in light of recent findings showing in vivo selection of antimicrobial resistance by single agents in this pathogen. IMPORTANCE It is becoming increasingly understood that the current paradigms of in vitro antimicrobial susceptibility testing may have significant shortcomings in predicting activity in vivo. This study evaluated the activity of several antibiotics alone and in combination against clinical isolates of Salmonella enterica serotype Newport (meningitis case) utilizing both conventional and physiological media. In addition, the interactions of these antibiotics with components of the innate immune system were evaluated. Azithromycin, which has performed quite well clinically despite high MICs in conventional media, was shown to be more active in physiological media and to enhance innate immune system killing. Alternatively, chloramphenicol did not show enhanced immune system killing, paralleling its inferior clinical performance to other antibiotics that have been used to treat Salmonella meningitis. These findings are important additions to the building understanding of current in vitro antimicrobial assay limitations that hopefully will amount to future improvements in these assays to better predict clinical efficacy and activity in vivo.

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Single passage in mouse organs enhances the survival and spread of Salmonella enterica

Journal of The Royal Society Interface ◽

10.1098/rsif.2015.0702 ◽

2015 ◽

Vol 12 (113) ◽

pp. 20150702 ◽

Cited By ~ 7

Author(s):

Richard Dybowski ◽

Olivier Restif ◽

Alexandre Goupy ◽

Duncan J. Maskell ◽

Piero Mastroeni ◽

...

Keyword(s):

Salmonella Enterica ◽

Probability Generating Function ◽

Systemic Infection ◽

Original Method ◽

Wild Type ◽

Immigration Process ◽

Serovar Typhimurium ◽

Intravenous Inoculation

Intravenous inoculation of Salmonella enterica serovar Typhimurium into mice is a prime experimental model of invasive salmonellosis. The use of wild-type isogenic tagged strains (WITS) in this system has revealed that bacteria undergo independent bottlenecks in the liver and spleen before establishing a systemic infection. We recently showed that those bacteria that survived the bottleneck exhibited enhanced growth when transferred to naive mice. In this study, we set out to disentangle the components of this in vivo adaptation by inoculating mice with WITS grown either in vitro or in vivo . We developed an original method to estimate the replication and killing rates of bacteria from experimental data, which involved solving the probability-generating function of a non-homogeneous birth–death–immigration process. This revealed a low initial mortality in bacteria obtained from a donor animal. Next, an analysis of WITS distributions in the livers and spleens of recipient animals indicated that in vivo -passaged bacteria started spreading between organs earlier than in vitro -grown bacteria. These results further our understanding of the influence of passage in a host on the fitness and virulence of Salmonella enterica and represent an advance in the power of investigation on the patterns and mechanisms of host–pathogen interactions.

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Role of B7 Costimulatory Molecules in Mediating Systemic and Mucosal Antibody Responses to Attenuated Salmonella enterica Serovar Typhimurium and Its Cloned Antigen

Infection and Immunity ◽

10.1128/iai.72.10.5824-5831.2004 ◽

2004 ◽

Vol 72 (10) ◽

pp. 5824-5831 ◽

Cited By ~ 4

Author(s):

Carlos A. Garcia ◽

Michael Martin ◽

Suzanne M. Michalek

Keyword(s):

Salmonella Enterica ◽

Immunoglobulin A ◽

Costimulatory Molecules ◽

Antibody Responses ◽

Wild Type ◽

Igg Antibody ◽

Functional Roles ◽

Serovar Typhimurium

ABSTRACT The purpose of the present study was to evaluate the ability of an attenuated Salmonella enterica serovar Typhimurium vaccine strain to up-regulate B7-1 and B7-2 on antigen-presenting cells and to examine the functional roles these costimulatory molecules play in mediating immune responses to Salmonella and to an expressed cloned antigen, the saliva-binding region (SBR) of antigen I/II. In vitro stimulation of B cells (B220+), macrophages (CD11b+), and dendritic cells (CD11c+) with S. enterica serovar Typhimurium induced an up-regulation of B7-2 and, especially, B7-1 expression. The in vivo functional roles of B7-1, B7-2, and B7-1/2 were evaluated in BALB/c wild-type and B7-1, B7-2, and B7-1/2 knockout (KO) mice following intranasal immunization with the Salmonella expressing the cloned SBR. Differential requirements for B7-1 and B7-2 were observed upon primary and secondary immunizations. Compared to wild-type controls, B7-1 and B7-2 KO mice had reduced mucosal and systemic anti-Salmonella antibody responses after a single immunization, while only B7-1 KO mice exhibited suppressed anti-Salmonella antibody responses following the second immunization. Mucosal and systemic antibody responses to SBR were reduced following the primary immunization, whereas a compensatory role for either B7-1 or B7-2 was observed after the second immunization. B7-1/2 double KO mice failed to induce detectable levels of mucosal or systemic immunoglobulin A (IgA) or IgG antibody responses to either Salmonella or SBR. These findings demonstrate that B7-1 and B7-2 can play distinct as well as redundant roles for mediating mucosal and systemic antibody responses, which are likely dependent upon the nature of the antigen.

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Effect of Inactivation of degS on Salmonella enterica Serovar Typhimurium In Vitro and In Vivo

Infection and Immunity ◽

10.1128/iai.73.1.459-463.2005 ◽

2005 ◽

Vol 73 (1) ◽

pp. 459-463 ◽

Cited By ~ 23

Author(s):

Gary Rowley ◽

Andrew Stevenson ◽

Jan Kormanec ◽

Mark Roberts

Keyword(s):

Sigma Factor ◽

Salmonella Enterica ◽

Salmonella Enterica Serovar Typhimurium ◽

Wild Type ◽

Alternative Pathways ◽

E Coli ◽

Mammalian Tissues ◽

Serovar Typhimurium

ABSTRACT The alternative sigma factor (RpoE σE) enables Salmonella enterica serovar Typhimurium to adapt to stressful conditions, such as oxidative stress, nutrient deprivation, and growth in mammalian tissues. Infection of mice by Salmonella serovar Typhimurium also requires σE. In Escherichia coli, activation of the σE pathway is dependent on proteolysis of the anti-sigma factor RseA and is initiated by DegS. DegS is also important in order for E. coli to cause extraintestinal infection in mice. We constructed a degS mutant of the serovar Typhimurium strain SL1344 and compared its behavior in vitro and in vivo with those of its wild-type (WT) parent and an isogenic rpoE mutant. Unlike E. coli degS strains, the Salmonella serovar Typhimurium degS strain grew as well as the WT strain at 42°C. The degS mutant survived very poorly in murine macrophages in vitro and was highly attenuated compared with the WT strain for both the oral and parenteral routes of infection in mice. However, the degS mutant was not as attenuated as the serovar Typhimurium rpoE mutant: 100- to 1,000-fold more degS bacteria than rpoE bacteria were present in the livers and spleens of mice 24 h after intraperitoneal challenge. In most assays, the rpoE mutant was more severely affected than the degS mutant and a σE-dependent reporter gene was more active in the degS mutant than the rpoE strain. These findings indicate that degS is important for activation of the σE pathway in serovar Typhimurium but that alternative pathways for σE activation probably exist.

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Salmonella enterica Serovar Typhimurium Exploits Toll-Like Receptor Signaling during the Host-Pathogen Interaction

Infection and Immunity ◽

10.1128/iai.00545-09 ◽

2009 ◽

Vol 77 (11) ◽

pp. 4750-4760 ◽

Cited By ~ 14

Author(s):

Christine E. Wong ◽

Subash Sad ◽

Brian K. Coombes

Keyword(s):

Immune System ◽

Type Iii Secretion ◽

Innate Immune System ◽

Salmonella Enterica ◽

Type Iii Secretion System ◽

Secretion System ◽

Innate Immune ◽

Type Iii ◽

Infection Dynamics ◽

Serovar Typhimurium

ABSTRACT Salmonella survives and replicates in host cells by using a type III secretion system to evade host immune defenses. The innate immune system plays an important role as a first line of defense against pathogens and is mediated in part by Toll-like receptors (TLRs); however, the infection dynamics of Salmonella enterica serovar Typhimurium within macrophages stimulated with TLR ligands is poorly understood. We studied the infection dynamics of Salmonella in murine macrophages previously exposed to TLR ligands and report that treatment of macrophages with four different TLR agonists resulted in their increased phagocytic capacity toward Salmonella but not fluorescent microspheres. Further analysis revealed that the intracellular replication of Salmonella was enhanced in TLR-stimulated macrophages in a manner requiring a functional type III secretion system and enhanced transcriptional activity of the sseA virulence gene operon. Studies of mice that normally resolve an acute primary infection with Salmonella revealed that pretreatment of animals with CpG DNA had a detrimental effect on disease outcome. CpG-treated mice infected with Salmonella all succumbed to infection and had higher bacterial loads in the spleen than did control animals. These data suggest that Salmonella can exploit macrophages activated via the innate immune system for increased intracellular survival.

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Salmonella enterica Serovar Typhimurium NiFe Uptake-Type Hydrogenases Are Differentially Expressed In Vivo

Infection and Immunity ◽

10.1128/iai.00741-08 ◽

2008 ◽

Vol 76 (10) ◽

pp. 4445-4454 ◽

Cited By ~ 27

Author(s):

Andrea L. Zbell ◽

Susan E. Maier ◽

Robert J. Maier

Keyword(s):

Salmonella Enterica ◽

Salmonella Enterica Serovar Typhimurium ◽

Acid Stress ◽

Wild Type ◽

Reverse Transcription Pcr ◽

Serovar Typhimurium ◽

Low Levels ◽

And Function ◽

Mutant Cells

ABSTRACT Salmonella enterica serovar Typhimurium, a common enteric pathogen, possesses three NiFe uptake-type hydrogenases. The results from mouse infection studies suggest that the H2 oxidation capacity provided by these hydrogenases is important for virulence. Since the three enzymes are similar in structure and function, it may be expected that they are utilized under different locations and times during an infection. A recombination-based method to examine promoter activity in vivo (RIVET) was used to determine hydrogenase gene expression in macrophages, polymorphonuclear leukocyte (PMN)-like cells, and a mouse model of salmonellosis. The hyd and hya promoters showed increased expression in both murine macrophages and human PMN-like cells compared to that in the medium-only controls. Quantitative reverse transcription-PCR results suggested that hyb is also expressed in phagocytes. A nonpolar hya mutant was compromised for survival in macrophages compared to the wild type. This may be due to lower tolerance to acid stress, since the hya mutant was much more acid sensitive than the wild type. In addition, hya mutant cells were internalized by macrophages the same as wild-type cells. Mouse studies (RIVET) indicate that hyd is highly expressed in the liver and spleen early during infection but is expressed poorly in the ileum in infected animals. Late in the infection, the hyd genes were expressed at high levels in the ileum as well as in the liver and spleen. The hya genes were expressed at low levels in all locations tested. These results suggest that the hydrogenases are used to oxidize hydrogen in different stages of an infection.

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Invasion Genes Are Not Required for Salmonella enterica Serovar Typhimurium To Breach the Intestinal Epithelium: Evidence That Salmonella Pathogenicity Island 1 Has Alternative Functions during Infection

Infection and Immunity ◽

10.1128/iai.68.9.5050-5055.2000 ◽

2000 ◽

Vol 68 (9) ◽

pp. 5050-5055 ◽

Cited By ~ 70

Author(s):

Rose Ann Murray ◽

Catherine A. Lee

Keyword(s):

Intestinal Epithelium ◽

Salmonella Enterica ◽

Type Strain ◽

Wild Type Strain ◽

Bacterial Colonization ◽

Intestinal Barrier ◽

Pathogenicity Island ◽

Bacterial Invasion ◽

Wild Type ◽

Serovar Typhimurium

ABSTRACT Salmonella enterica serovar Typhimurium invasion genes are necessary for bacterial invasion of intestinal epithelial cells and are thought to allow salmonellae to enter and cross the intestinal epithelium during infection. Many invasion genes are encoded on Salmonella pathogenicity island 1 (SPI1), and their expression is activated by HilA, a transcription factor also encoded on SPI1. We have studied the role ofSalmonella invasion genes during infection of mice following intragastric inoculation. We have found that strains containing a mutation in hilA orinvG were recovered from the intestinal contents, intestinal tissues, and systemic tissues at a lower frequency than their parental wild-type strain. In contrast, a strain in which SPI1 is deleted was recovered from infected mice at a frequency similar to that of its parental wild-type strain. The ΔSPI1 phenotype indicates that S. enterica does not require invasion genes to cross the intestinal epithelium and infect systemic tissues. This result has forced us to reconsider the long-held belief that invasion genes directly mediate bacterial infection of the intestinal mucosa and traversion of the intestinal barrier during infection. Instead, our results suggest that hilA is required for bacterial colonization of the host intestine. The seemingly contradictory phenotype of the ΔSPI1 mutant suggests that deletion of another gene(s) encoded on SPI1 suppresses thehilA mutant defect. We propose a model for S. enterica pathogenesis in which hilA and invasion genes are required for salmonellae to overcome a host clearance response elicited by another SPI1 gene product(s).

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Aggregation via the Red, Dry, and Rough Morphotype Is Not a Virulence Adaptation in Salmonella enterica Serovar Typhimurium

Infection and Immunity ◽

10.1128/iai.01383-07 ◽

2008 ◽

Vol 76 (3) ◽

pp. 1048-1058 ◽

Cited By ~ 44

Author(s):

A. P. White ◽

D. L. Gibson ◽

G. A. Grassl ◽

W. W. Kay ◽

B. B. Finlay ◽

...

Keyword(s):

In Vivo Imaging ◽

Salmonella Enterica ◽

Salmonella Enterica Serovar Typhimurium ◽

Primary Role ◽

Wild Type ◽

Serovar Typhimurium ◽

Cell Densities ◽

Two Populations

ABSTRACT The Salmonella rdar (red, dry, and rough) morphotype is an aggregative and resistant physiology that has been linked to survival in nutrient-limited environments. Growth of Salmonella enterica serovar Typhimurium was analyzed in a variety of nutrient-limiting conditions to determine whether aggregation would occur at low cell densities and whether the rdar morphotype was involved in this process. The resulting cultures consisted of two populations of cells, aggregated and nonaggregated, with the aggregated cells preferentially displaying rdar morphotype gene expression. The two groups of cells could be separated based on the principle that aggregated cells were producing greater amounts of thin aggregative fimbriae (Tafi or curli). In addition, the aggregated cells retained some physiological characteristics of the rdar morphotype, such as increased resistance to sodium hypochlorite. Competitive infection experiments in mice showed that nonaggregative ΔagfA cells outcompeted rdar-positive wild-type cells in all tissues analyzed, indicating that aggregation via the rdar morphotype was not a virulence adaptation in Salmonella enterica serovar Typhimurium. Furthermore, in vivo imaging experiments showed that Tafi genes were not expressed during infection but were expressed once Salmonella was passed out of the mice into the feces. We hypothesize that the primary role of the rdar morphotype is to enhance Salmonella survival outside the host, thereby aiding in transmission.

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A Superoxide-Hypersusceptible Salmonella enterica Serovar Typhimurium Mutant Is Attenuated but Regains Virulence in p47phox−/− Mice

Infection and Immunity ◽

10.1128/iai.70.5.2614-2621.2002 ◽

2002 ◽

Vol 70 (5) ◽

pp. 2614-2621 ◽

Cited By ~ 19

Author(s):

Angela van Diepen ◽

Tahar van der Straaten ◽

Steven M. Holland ◽

Riny Janssen ◽

Jaap T. van Dissel

Keyword(s):

Salmonella Enterica ◽

Defense Mechanisms ◽

Mononuclear Phagocytes ◽

Wild Type ◽

Phagocytic Cells ◽

Bacterial Counts ◽

Innate Defense ◽

Serovar Typhimurium

ABSTRACT Salmonella enterica serovar Typhimurium is a gram-negative, facultative intracellular pathogen that predominantly invades mononuclear phagocytes and is able to establish persistent infections. One of the innate defense mechanisms of phagocytic cells is the production of reactive oxygen species, including superoxide. S. enterica serovar Typhimurium has evolved mechanisms to resist such radicals, and these mechanisms could be decisive in its ability to survive and replicate within macrophages. Recently, we described a superoxide-hypersusceptible S. enterica serovar Typhimurium mutant strain, DLG294, that carries a transposon in sspJ, resulting in the lack of expression of SspJ, which is necessary for resistance against superoxide and replication within macrophages. Here we show that DLG294, which is a 14028s derivative, hardly induced any granulomatous lesions in the livers upon subcutaneous infection of C3H/HeN (Ityr) mice with 3 × 104 bacteria and that its bacterial counts were reduced by 3 log units compared to those of wild-type S. enterica serovar Typhimurium 14028s on day 5 after infection. In contrast, DLG294 replicated like wild-type S. enterica serovar Typhimurium 14028s and induced a phenotypically similar liver pathology in p47phox−/− mice, which are deficient in the p47phox subunit of the NADPH oxidase complex and which do not produce superoxide. Consistent with these results, DLG294 reached bacterial counts identical to those of wild-type S. enterica serovar Typhimurium 14028s in bone marrow-derived macrophages from p47phox−/− mice and in X-CGD PLB-985 cells at 24 h after challenge. These results indicate that SspJ plays a role in the bacterium's resistance to oxidative stress and in the survival and replication of S. enterica serovar Typhimurium both in vitro and in vivo.

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