Endogenous and exogenous interleukin-12 augment the protective immune response in mice orally challenged with Salmonella dublin

Identification and functional characterization of interleukin-12 receptor beta 1 and 2 in grass carp (Ctenopharyngodon idella)

Interleukin 12 (IL-12) binds its receptor complex of IL-12 receptor beta 1 (IL-12Rβ1) and IL-12Rβ2 to transduce cellular signaling in mammals. In teleosts, the function of Il-12 is drawing increasing attention, but molecular and functional features of Il-12 receptors remain obscure. Especially, the existence of multiple Il-12 isoforms in some fish species elicits the requirement to clarify their receptors. In this study, we isolated three cDNA sequences as Il-12 receptor candidates from grass carp, entitled as grass carp Il-12rβ1 (gcIl-12rβ1), gcIl-12rβ2a and gcIl-12rβ2b. In silico analysis showed that gcIl-12rβ1 and gcIl-12rβ2a shared the conserved gene locus and similar structure characteristics with their orthologues of zebrafish, frog, chicken, mouse and human, respectively. However, the Il-12rβ2b of grass carp and zebrafish was similar to IL-27Ra in non-fish species. Further locally installed BLAST and gene synteny analysis uncovered three gcIl-12 receptors being single copied genes. Tissue distribution assay revealed that gcil12rβ1 and gcil12rβ2a transcripts were predominantly expressed in head kidney, differing from the even distribution of gcil12rβ2b transcripts in all detected tissues. Subsequently, the binding ability and antagonistic effects of recombinant extracellular region of gcIl-12rβ1 with recombinant grass carp Il-12 (rgcIl-12) isoforms were explored, providing functional evidence of the newly cloned gcIl-12rβ1 being genuine orthologues of mammalian IL-12Rβ1. Moreover, our data showed that gcIl-12rβ1 and gcIl-12rβ2a but not gcIl-12rβ1 and gcIl-12rβ2b mediated the effects of rgcIl-12 isoforms on ifn-γ promoter activity, thereby revealing Il-12 receptor signaling in fish. These results identified grass carp Il-12 receptors, thereby advancing our understanding of Il-12 isoform signaling in fish.

Humoral Immunity vs. Salmonella

In primary infection with Salmonella, it has been reported—without consideration of Salmonella's functions—that humoral immunity plays no role in the clearance of bacteria. In fact, Salmonella targets and suppresses several aspects of humoral immunity, including B cell lymphopoiesis, B cell activation, and IgG production. In particular, the suppression of IgG-secreting plasma cell maintenance allows the persistence of Salmonella in tissues. Therefore, the critical role(s) of humoral immunity in the response to Salmonella infection, especially at the late phase, should be re-investigated. The suppression of IgG plasma cell memory strongly hinders vaccine development against non-typhoidal Salmonella (NTS) because Salmonella can also reduce humoral immune memory against other bacteria and viruses, obtained from previous vaccination or infection. We propose a new vaccine against Salmonella that would not impair humoral immunity, and which could also be used as a treatment for antibody-dependent autoimmune diseases to deplete pathogenic long-lived plasma cells, by utilizing the Salmonella's own suppression mechanism of humoral immunity.

Protective efficacy of a Salmonella Typhimurium ghost vaccine candidate constructed with a recombinant lysozyme-PMAP36 fusion protein in a murine model

A Salmonella Typhimurium ghost vaccine was constructed with the use of a recombinant fusion protein consisting of lysozyme and porcine myeloid antimicrobial peptide 36 expressed by the Escherichia coli overexpression system. After confirmation of its effectiveness by transmission electron microscopy the vaccine was evaluated in a murine model. Of the 60 BALB/c mice equally divided into 4 groups, group A mice were intramuscularly inoculated with 100 μL of sterile phosphate-buffered saline, and the mice in groups B, C, and D were intramuscularly inoculated with approximately 1.0 × 10⁴, 1.0 × 10⁵, or 1.0 × 10⁶ cells of the S. Typhimurium ghost vaccine, respectively, in 100-μL amounts. The serum IgG titers against S. Typhimurium outer membrane proteins were significantly higher in groups B to D than in group A, as were the concentrations of interleukin-10 and interferon gamma in supernatants of harvested splenocytes. After challenge with wild-type S. Typhimurium, all the vaccinated groups showed significant protection compared with group A, notably perfect protection in groups C and D. Overall, these results show that intramuscular vaccination with 1.0 × 10⁵ cells of this ghost vaccine candidate provided efficient protection against systemic infection with virulent S. Typhimurium.

Role of Substance P Neuropeptide in Inflammation, Wound Healing, and Tissue Homeostasis

Substance P (SP) is an undecapeptide present in the CNS and the peripheral nervous system. SP released from the peripheral nerves exerts its biological and immunological activity via high-affinity neurokinin 1 receptor (NK1R). SP is also produced by immune cells and acts as an autocrine or paracrine fashion to regulate the function of immune cells. In addition to its proinflammatory role, SP and its metabolites in combination with insulin-like growth factor-1 are shown to promote the corneal epithelial wound healing. Recently, we showed an altered ocular surface homeostasis in unmanipulated NK1R^-/- mice, suggesting the role of SP-NK1R signaling in ocular surface homeostasis under steady-state. This review summarizes the immunobiology of SP and its effect on immune cells and immunity to microbial infection. In addition, the effect of SP in inflammation, wound healing, and corneal epithelial homeostasis in the eye is discussed.

Molecular cloning of the rabbit interleukin 6 promoter: Functional characterization of rabbit hemorrhagic disease virus response elements in RK-13 cells

Infection with rabbit hemorrhagic disease virus (RHDV) can cause acute liver failure (ALF), leading to severe mortality in rabbits. Inflammatory response, especially the expression of inflammatory cytokines such as interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and IL-6, may play major roles in mediating and amplifying the ALF. Among these cytokines, IL-6 is a multifunctional cytokine with a central role in various physiological inflammatory and immunological processes. In this study, we found that RHDV infection significantly upregulated IL-6 gene expression in vivo. Next, the rabbit IL-6 promoter was cloned and analyzed. Transfection of full-length RHDV cDNA in RK-13 cells upregulated the activity of the IL-6 promoter. A series of 5' deletion constructs demonstrated that AP-1 (activator protein 1), NF-IL6 (nuclear factor interleukin-6), and NF-κB (nuclear factor kappa B) elements were critical for RHDV-induced IL-6 transcription. Besides, the CREB (cAMP-response element binding protein) element may also play an accessory effect on RHDV-induced IL-6 transcription. Collectively, the results elucidate the mechanism of IL-6 induction, and enrich the RHDV pathogenesis in rabbit.

Type 1 fimbriae are important factors limiting the dissemination and colonization of mice by Salmonella Enteritidis and contribute to the induction of intestinal inflammation during Salmonella invasion

We have recently shown that Salmonella Gallinarum type 1 fimbriae with endogenous mannose-resistant (MR) variant of the FimH protein increase systemic dissemination of S. Gallinarum and colonization of internal organs in comparison to the S. Gallinarum fimH knockout strain or the mutant expressing mannose-sensitive (MS) FimH variant from S. Enteritidis. Elaborating from these studies, we proposed that MS variants of FimH are advantageous in gastrointestinal infections, in contrast to MR FimH variants which decrease intestinal colonization and promote their systemic spreading. To support our hypothesis, we carried out in vivo studies using mice infected with wild-type S. Enteritidis and its fimH knockout strain (S. Enteritidis), which was characterized by significantly lower adhesion and invasiveness of murine ICE-1 intestinal cells. Using bioluminescence imaging, we observed that the loss of MS FimH adhesin correlates well with the highly increased colonization of mice by these bacteria. The appearance of the mutant strain was observed much earlier than wild-type Salmonella, and mice infected with 10⁴–10⁷S. Enteritidis fimH::kan CFUs had significantly (P < 0.05) shorter infection-free time than animals inoculated with wild-type S. Enteritidis. Infections caused by non-typhoid Salmonella, such as S. Enteritidis, are associated with massive inflammation of the lamina propria and lymph nodes in the intestinal tract. Therefore, we evaluated the role of MS type 1 fimbriae in the induction of cytokine expression and secretion, using murine ICE-1 intestinal cells. We showed that the expression, as well as secretion, of Il-1b, Il-6, Il-10, and Il-12b was significantly higher in cells infected with wild-type S. Enteritidis compared to cells infected with the mutant strain. Based on our results, we propose that type 1 fimbriae may play an important role in the pathogenicity of S. Enteritidis and may contribute to an intestinal inflammatory response.

Nanocapsules loaded with iron-saturated bovine lactoferrin have antimicrobial therapeutic potential and maintain calcium, zinc and iron metabolism

AIM

This study aimed to evaluate the potential antimicrobial efficacy of alginate gel-encapsulated ceramic nanocarriers loaded with iron-saturated bovine lactoferrin (Fe-bLf) nanocarriers/nanocapsules (AEC-CP-Fe-bLf NCs).

MATERIALS & METHODS

The antimicrobial activities of non-nanoformulated apo (iron free), Fe-bLf and native forms of Australian bLf against pathogenic Salmonella typhimurium (wild strain) were studied in vitro. The efficacy of AEC-CP-Fe-bLf NCs were checked in vivo using Balb/c mice model.

RESULTS

The study revealed that native bLf is more effective in combating infection than the conventional drug ciprofloxacin (0.4 mg/ml). The efficacy of the drug was also revealed in vivo when BALB/c mice that, after being challenged with S. typhimurium (200 μl of 10(8) CFU/ml suspension), were fed orally with a nanoformulated bLf diet and the infection was observed to be eliminated. However, chronic infection developed in the group of infected mice that did not receive any drug treatment, as well as the mice treated with ciprofloxacin. The immune response to bacterial infection and to various drug treatments thereafter was studied in the mice.

CONCLUSION

The study concludes that bLf and nanoformulated Fe-bLf are more effective in the treatment of Salmonella-infected mice than ciprofloxacin.

Risks for infection in patients with asthma (or other atopic conditions): is asthma more than a chronic airway disease?

Most of the research effort regarding asthma has been devoted to its causes, therapy, and prognosis. There is also evidence that the presence of asthma can influence patients' susceptibility to infections, yet research in this aspect of asthma has been limited. There is additional debate in this field, with current literature tending to view the increased risk of infection among atopic patients as caused by opportunistic infections secondary to airway inflammation, especially in patients with severe atopic diseases. However, other evidence suggests that such risk and its underlying immune dysfunction might be a phenotypic or clinical feature of atopic conditions. This review argues (1) that improved understanding of the effects of asthma or other atopic conditions on the risk of microbial infections will bring important and new perspectives to clinical practice, research, and public health concerning atopic conditions and (2) that research efforts into the causes and effects of asthma must be juxtaposed because they are likely to guide each other.

Impact of Asthma on the Severity of Serious Pneumococcal Disease

We recently reported an increased risk of serious pneumococcal disease (SPD) in asthmatics. Little is known about the impact of asthma status on the severity of SPD. We compared the severity of serious pneumococcal disease (SPD) between patients with asthma and those without asthma. The study subjects were Rochester, Minnesota residents who developed SPD between 1964 and 1983. SPD and asthma status were ascertained by using explicit predetermined criteria Severity of SPD was assessed using intensive care unit (ICU) admission rate and total days of ICU stay and hospitalization associated with treatment for SPD. We found that there were no significant differences in severity outcomes between asthmatics (n=11) and non-asthmatics (n=163). Asthma status may increase the risk of SPD but not influence its severity. However, given a small sample size of our study, a larger study needs to be considered to clarify the relationship between asthma and severity of SPD.

Neuropeptide signaling activates dendritic cell-mediated type 1 immune responses through neurokinin-2 receptor

Neurokinin A (NKA), a neurotransmitter distributed in the central and peripheral nervous system, strictly controls vital responses, such as airway contraction, by intracellular signaling through neurokinin-2 receptor (NK2R). However, the function of NKA-NK2R signaling on involvement in immune responses is less-well defined. We demonstrate that NK2R-mediated neuropeptide signaling activates dendritic cell (DC)-mediated type 1 immune responses. IFN-γ stimulation significantly induced NK2R mRNA and remarkably enhanced surface protein expression levels of bone marrow-derived DCs. In addition, the DC-mediated NKA production level was significantly elevated after IFN-γ stimulation in vivo and in vitro. We found that NKA treatment induced type 1 IFN mRNA expressions in DCs. Transduction of NK2R into DCs augmented the expression level of surface MHC class II and promoted Ag-specific IL-2 production by CD4(+) T cells after NKA stimulation. Furthermore, blockade of NK2R by an antagonist significantly suppressed IFN-γ production by both CD4(+) T and CD8(+) T cells stimulated with the Ag-loaded DCs. Finally, we confirmed that stimulation with IFN-γ or TLR3 ligand (polyinosinic-polycytidylic acid) significantly induced both NK2R mRNA and surface protein expression of human PBMC-derived DCs, as well as enhanced human TAC1 mRNA, which encodes NKA and Substance P. Thus, these findings indicate that NK2R-dependent neuropeptide signaling regulates Ag-specific T cell responses via activation of DC function, suggesting that the NKA-NK2R cascade would be a promising target in chronic inflammation caused by excessive type 1-dominant immunity.

Increased risk of pertussis in patients with asthma

BACKGROUND

The recent pertussis outbreak in California highlights the effect of pertussis on public health. In 2004, a pertussis outbreak occurred in Olmsted County, Minnesota, despite a high vaccine uptake. This outbreak provided a natural experiment to assess the relationship between asthma and pertussis.

OBJECTIVE

We sought to determine whether asthmatic subjects have a higher risk of pertussis than nonasthmatic subjects.

METHODS

We conducted a population-based case-control study. There were 223 pertussis cases identified by means of PCR in 2004 and 2005. We identified age- and sex-matched control subjects from 5537 patients with negative test results for pertussis. We conducted a comprehensive medical record review and applied predetermined criteria to ascertain asthma status. Conditional logistic regression was fit to assess the effect of asthma status on the risk of pertussis.

RESULTS

Of the 223 subjects, 164 were eligible for the study, and 328 matched control subjects (1:2 matching) were enrolled. Of these 164 subjects, 50% were male, and 82% were white. The median age at the index date of pertussis was 14 years. Sixty-two (38%) of the 164 cases had asthma before the index date of pertussis compared with 85 (26%) of the 328 control subjects (odds ratio, 1.73; 95% CI, 1.12-2.67; P = 013). The population attributable risk percentage of asthma for risk of pertussis was 17%.

CONCLUSIONS

Given the high prevalence of asthma and the ongoing risk of pertussis throughout the United States, consideration of defining asthmatic subjects as a target group for pertussis vaccination (eg, replacing decennial tetanus-diphtheria booster with tetanus, diphtheria, and acellular pertussis vaccine for adolescents and adults) should be given.

Influence of asthma status on serotype-specific pneumococcal antibody levels

BACKGROUND

Asthma has been reported to be associated with an increased risk of invasive pneumococcal disease (IPD).

OBJECTIVE

We compared serotype-specific antibody responses with pneumococcal polysaccharide antigens of individuals with and without asthma.

METHODS

A cross-sectional study was conducted for 16 subjects with asthma and 14 subjects without asthma from the community of Rochester, MN. Asthma was determined by predetermined criteria based on comprehensive medical record reviews. Serotype-specific antibody to 23 pneumococcal polysaccharide antigens was measured by enzyme-linked immunosorbent assay, and seropositivity was considered ≥ 1.3 μg/mL. Interferon-γ (IFN-γ) and interleukin-5 (IL-5) were measured from peripheral blood mononuclear cells cultured with house dust mites and staphylococcal enterotoxin B.

RESULTS

Of the 30 subjects, 16 (53%) were male, 21 (70%) were white, and the median age was 26 years. The median numbers of positive serotype-specific antibodies for asthmatics and nonasthmatics were 8.5 and 15.5, respectively (P = 0.034). There was an inverse relationship between the ratio of log-transformed IL-5/IFN-γ and the number of positive serotype-specific antibodies (r = -0.36; P = 0.052). As potential covariates and confounders, a history of pneumococcal vaccination (P = 0.84), having a high-risk condition for IPD (P = 0.68), and taking asthma medications, including inhaled/systemic corticosteroids (P = 0.79), were not associated with the number of positive serotype-specific antibodies.

CONCLUSION

Asthmatics had significantly lower serotype-specific pneumococcal antibody levels than nonasthmatics. House dust mite-induced T-helper 2 (Th2) cytokine immune profile may be related to the association. This may account for an increased risk of IPD in asthmatics and deserves further investigation.

Both hemolytic anemia and malaria parasite-specific factors increase susceptibility to Nontyphoidal Salmonella enterica serovar typhimurium infection in mice

Severe pediatric malaria is an important risk factor for developing disseminated infections with nontyphoidal Salmonella serotypes (NTS). While recent animal studies on this subject are lacking, early work suggests that an increased risk for developing systemic NTS infection during malaria is caused by hemolytic anemia, which leads to reduced macrophage microbicidal activity. Here we established a model for oral Salmonella enterica serotype Typhimurium challenge in mice infected with Plasmodium yoelii nigeriensis. Initial characterization of this model showed that 5 days after coinoculation, P. yoelii nigeriensis infection increased the recovery of S. Typhimurium from liver and spleen by approximately 1,000-fold. The increased bacterial burden could be only partially recapitulated by antibody-mediated hemolysis, which increased the recovery of S. Typhimurium from liver and spleen by 10-fold. These data suggested that both hemolysis and P. yoelii nigeriensis-specific factors contributed to the increased susceptibility to S. Typhimurium. The mechanism by which hemolysis impaired resistance to S. Typhimurium was further investigated. In vitro, S. Typhimurium was recovered 24 h after infection of hemophagocytic macrophages in 2-fold-higher numbers than after infection of mock-treated macrophages, making it unlikely that reduced macrophage microbicidal activity was solely responsible for hemolysis-induced immunosuppression during malaria. Infection with P. yoelii nigeriensis, but not antibody-mediated hemolysis, reduced serum levels of interleukin-12p70 (IL-12p70) in response to S. Typhimurium challenge. Collectively, studies establishing a mouse model for this coinfection suggest that multiple distinct malaria-induced immune defects contribute to increased susceptibility to S. Typhimurium.

Effect of a BIOcocktail on the Immune Response at the Early Postoperative Period in Mice

Since human subjects and laboratory animals may develop impaired immune response during surgery and the postoperative period, efforts have been made to preserve normal immune functions following surgery by the administration of nutritional supplements and probiotics. The present study was designed to examine the effect of a new nutritional supplement, BIOcocktail, on immune parameters in mice exposed to surgery. Forty mice were assigned to 4 groups containing 10 animals each. Two control groups (with and without subsequent sham laparotomy) were given tap water for 45 min every day for 2 weeks. The remaining 2 groups, with and without laparotomy, received BIOcocktail given orally for the same period of time. The proliferative response of splenic cells (splenocytes) stimulated with phytohemagglutinin (PHA), concanavalin A (Con A) and lipopolysaccharide (LPS) was determined by [3H]thymidine uptake. Cytokine levels were measured in splenocyte supernatants and sera using enzyme-linked immunosorbent assay (ELISA) kits. Natural killer cell activity of splenocytes was evaluated by 51Cr-release assay. Laparotomy, without BIOcocktail administration, was followed by a decreased proliferative response of splenocytes to PHA, Con A, and LPS and an increase in interleukin (IL)-6 serum level. In addition, a decreased secretion of IL-1beta, IL-12 and tumor necrosis factor (TNF)-alpha by the splenocytes was observed. Mice treated with BIOcocktail before laparotomy maintained a preoperative level of splenocyte proliferative response and serum concentrations of IL-12. It is concluded that BIOcocktail administered to mice for 2 weeks before operation resulted in the preservation of T- and B-cell proliferative response to mitogens and in the prevention of postoperative decrease in IL-12 serum level.

Allergic airway inflammation and susceptibility to pneumococcal pneumonia in a murine model with real-time in vivo evaluation

The relationship between allergic airway inflammation and pneumococcal pneumonia is not well understood. We assessed susceptibility to experimental pneumococcal pneumonia in mice with and without allergic airway inflammation. Susceptibility to pneumococcal pneumonia was evaluated by challenging mice with a bioluminescent Streptococcus pneumoniae strain after sensitization with ovalbumin (OVA), with subsequent monitoring of pneumococcal infection using real-time photonic imaging. Of 46 OVA-sensitized mice challenged with pneumococci, 13 (28%) developed imaging findings consistent with pneumococcal pneumonia. In comparison, 28 (57%) of 49 non-sensitized control mice developed pneumococcal pneumonia (P = 0.005). While none of the control group developed meningitis (0%, none of 28), two mice in the OVA-sensitized group developed meningitis (15.4%, two of 13) (P = 0.09). The mean bacterial count in the lung was significantly lower in the OVA-sensitized than the non-sensitized group (8.26 +/- 0.69 versus 9.21 +/- 0.67 log(10) colony-forming units (CFU)/g, P = 0.002). There was a trend towards the mean bacterial count in the spleen being higher in the OVA-sensitized versus the non-sensitized group (8.14 +/- 0.89 versus 7.45 +/- 1.07 log(10) CFU/g, P = 0.071). A high level of interleukin (IL)-4 in lung homogenates was associated with risk of pneumococcal infection independent of sensitization with OVA (odds ratio: 49.7, 95% confidence interval 2.92-846.5, per increment of 1.0 pg/ml). In the murine model studied, acute allergic airway inflammation reduced susceptibility to pneumococcal pneumonia. IL-4 may increase the risk of pneumococcal pneumonia independently of allergic airway inflammation.

Interactions between human NK cells and macrophages in response to Salmonella infection

NK cells play a key role in host resistance to a range of pathogenic microorganisms, particularly during the initial stages of infection. NK cell interactions with cells infected with viruses and parasites have been studied extensively, but human bacterial infections have not been given the same attention. We studied crosstalk between human NK cells and macrophages infected with intracellular Salmonella. These macrophages activated NK cells, resulting in secretion of IFN-gamma and degranulation. Reciprocally, NK cell activation led to a dramatic reduction in numbers of intramacrophagic live bacteria. We identified three elements in the interaction of NK cells with infected macrophages. First, communication between NK cells and infected macrophages was contact-dependent. The second requirement was IL-2- and/or IL-15-dependent priming of NK cells to produce IFN-gamma. The third was activation of NK cells by IL-12 and IL-18, which were secreted by the Salmonella-infected macrophages. Adhesion molecules and IL-12Rbeta2 were enriched in the contact zone between NK cells and macrophages, consistent with contact- and IL-12/IL-18-dependent NK activation. Our results suggest that, in humans, bacterial clearance is consistent with a model invoking a "ménage à trois" involving NK cells, IL-2/IL-15-secreting cells, and infected macrophages.

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Production of IL-12 and IFN-γ secretion are important components of the protective host response against the intracellular bacterial pathogen, Salmonella typhimurium. While infection with Salmonella does elicit this T helper type 1 response, its magnitude does not appear to be sufficient to prevent infection or limit pathogenesis. Therefore we have investigated factors which might limit a T helper type 1 response following infection. Previously we found that infection of antigen presenting cells with Salmonella dramatically increases cyclooxygenase-2 (COX-2) activity, resulting in high levels of prostaglandin E₂ (PGE₂). Since PGE₂ production can have profound effects on initiation of T helper type 1 responses, we questioned whether this mediator might limit antigen-specific T cell activation. Here we show that blockage of COX-2 activity with the selective inhibitor celecoxib leads to enhancement of the T helper type 1 components stimulated by Salmonella infection. In vitro studies demonstrate the induction of IL-12 and IFN-γ upon Salmonella exposure, which are further increased following COX-2 inhibition. Taken together these in vitro studies suggest that COX-2 activity can limit a salmonella-initiated T helper type 1 response.

Increased risk of serious pneumococcal disease in patients with asthma

BACKGROUND

Individuals with asthma have been reported to be at increased risk of invasive pneumococcal disease (IPD). These findings need to be confirmed in a different population-based study setting.

OBJECTIVE

We assessed whether serious pneumococcal disease (SPD), defined as an IPD, pneumococcal pneumonia, or both, was associated with asthma status.

METHODS

This is a retrospective case-control study using criteria-based methods for ascertaining SPD, as well as asthma. Subjects were residents of Rochester, Minnesota, who had SPD between 1964 and 1983 (the primarily pre-pneumococcal vaccine era) and their age- and sex-matched control subjects using 1:2 matching. Potential cases and control subjects were identified by using the Rochester Epidemiology project database and confirmed by medical record reviews. All cases and control subjects were merged with the database comprising the entire pool of Rochester residents with and without asthma between 1964 and 1983.

RESULTS

A total of 3941 records of potential patients with SPD were reviewed, and we identified 174 cases of SPD (51% male subjects and 94% white subjects). SPD was associated with a history of asthma among all ages (odds ratio, 2.4; 95% CI, 0.9-6.6; P = .09) and among adults (odds ratio, 6.7; 95% CI, 1.6-27.3; P = .01), controlling for high-risk conditions for IPD and smoking exposure. The population-attributable risk percentage was 17% in the adult population.

CONCLUSION

Adults with asthma might be at increased risk of SPD.

Integrin alphaDbeta2 is dynamically expressed by inflamed macrophages and alters the natural history of lethal systemic infections

The leukocyte integrins have critical roles in host defense and inflammatory tissue injury. We found that integrin alphaDbeta2, a novel but largely uncharacterized member of this family, is restricted to subsets of macrophages and a small population of circulating leukocytes in wild-type mice in the absence of inflammatory challenge and is expressed in regulated fashion during cytokine-induced macrophage differentiation in vitro. alphaDbeta2 is highly displayed on splenic red pulp macrophages and mediates their adhesion to local targets, identifying key functional activity. In response to challenge with Plasmodium berghei, a malarial pathogen that models systemic infection and inflammatory injury, new populations of alphaD+ macrophages evolved in the spleen and liver. Unexpectedly, targeted deletion of alphaD conferred a survival advantage in P. berghei infection over a 30-day observation period. Mechanistic studies demonstrated that the increased survival of alphaD-/- animals at these time points is not attributed to differences in magnitude of anemia or parasitemia or to alterations in splenic microanatomy, each of which is a key variable in the natural history of P. berghei infection, and indicated that an altered pattern of inflammatory cytokines may contribute to the difference in mortality. In contrast to the outcome in malarial challenge, death of alphaD-/- animals was accelerated in a model of Salmonella sepsis, demonstrating differential rather than stereotyped roles for alphaDbeta2 in systemic infection. These studies identify previously unrecognized and unique activities of alphaDbeta2, and macrophages that express it, in host defense and injury.

Virulent Salmonella enterica infections can be exacerbated by concomitant infection of the host with a live attenuated S. enterica vaccine via Toll-like receptor 4-dependent interleukin-10 production with the involvement of both TRIF and MyD88

During systemic disease in mice, Salmonella enterica grows intracellularly within discrete foci of infection in the spleen and liver. In concomitant infections, foci containing different S. enterica strains are spatially separated. We have investigated whether functional interactions between bacterial populations within the same host can occur despite the known spatial separation of the foci and independence of growth of salmonellae residing in different foci. In this study we have demonstrated that bacterial numbers of virulent S. enterica serovar Typhimurium C5 strain in mouse tissues can be increased by the presence of the attenuated aroA S. Typhimurium SL3261 vaccine strain in the same tissue. Disease exacerbation does not require simultaneous coinjection of the attenuated bacteria. SL3261 can be administered up to 48 hr after or 24 hr before the administration of C5 and still determine higher tissue numbers of the virulent bacteria. This indicates that intravenous administration of a S. enterica vaccine strain could potentially exacerbate an established infection with wild-type bacteria. These data also suggest that the severity of an infection with a virulent S. enterica strain can be increased by the prior administration of a live attenuated vaccine strain if infection occurs within 48 hr of vaccination. Exacerbation of the growth of C5 requires Toll-like receptor 4-dependent interleukin-10 production with the involvement of both Toll/interleukin-1 receptor-domain-containing adaptor inducing interferon-beta and myeloid differentiation factor 88.

Pregnancy impairs the innate immune resistance to Salmonella typhimurium leading to rapid fatal infection

Typhoid fever and gastroenteritis caused by Salmonella enterica species are increasing globally. Pregnancy poses a high risk, but it is unclear how maternal immunity to infection is altered. In mice, susceptible strains die of S. enterica serovar typhimurium (ST) infection within 7 days whereas resistant mice (129 x 1/SvJ) develop a chronic infection. We found that virulent ST infection during pregnancy, in normally resistant 129 x 1/SvJ mice, evoked approximately 100% fetal loss and surprisingly >60% host fatality, with a median survival of 6 days. Splenic bacterial load was 1000-fold higher in pregnant mice. This correlated to a diminished splenic recruitment/expansion of innate immune cells: dendritic cells, neutrophils, and NK cells. In particular, the splenic expansion and activation of NK cells postinfection seen in nonpregnant mice was lacking in pregnancy. Most notably, pregnant-infected mice had decreased production of serum IL-12 and increased IL-6 levels. Moreover, uteroplacental tissue of pregnant-infected mice exhibited an approximately 40-fold increase in IL-6 mRNA expression relative to noninfected placenta, whereas IL-12p40 was not increased. In vivo blocking of IL-6 significantly reduced the splenic bacterial burden in pregnant mice yet failed to prevent fetal loss. Fetal demise correlated to the rapidity of infection; by 14 h, ST expanded to >10(5) in the placenta and had reached the fetus. Therefore, the preferential placental expansion of ST plausibly altered the inflammatory response toward IL-6 and away from IL-12, reducing the recruitment/activation of splenic innate immune cells. Thus, highly virulent pathogens may use placental invasion to alter systemic host resistance to infection.

Gamma interferon-independent effects of interleukin-12 on immunity to Salmonella enterica serovar Typhimurium

Interleukin-12 (IL-12) and IL-18 are both central to the induction of gamma interferon (IFN-gamma), and various roles for IL-12 and IL-18 in control of intracellular microbial infections have been demonstrated. We used IL-12p40(-/-) and IL-18(-/-) mice to further investigate the role of IL-12 and IL-18 in control of Salmonella enterica serovar Typhimurium. While C57BL/6 and IL-18(-/-) mice were able to resolve attenuated S. enterica serovar Typhimurium infections, the IL-12p40(-/-) mice succumbed to a high bacterial burden after 60 days. Using ovalbumin (OVA)-specific T-cell receptor transgenic T cells (OT-II cells), we demonstrated that following oral infection with recombinant S. enterica serovar Typhimurium expressing OVA, the OT-II cells proliferated in the mesenteric lymph nodes of C57BL/6 and IL-18(-/-) mice but not in IL-12p40(-/-) mice. In addition, we demonstrated by flow cytometry that equivalent or increased numbers of T cells produced IFN-gamma in IL-12p40(-/-) mice compared with the numbers of T cells that produced IFN-gamma in C57BL/6 and IL-18(-/-) mice. Finally, we demonstrated that removal of macrophages from S. enterica serovar Typhimurium-infected C57BL/6 and IL-12p40(-/-) mice did not affect the bacterial load, suggesting that impaired control of S. enterica serovar Typhimurium infection in the absence of IL-12p40 is not due to reduced macrophage bactericidal activities, while IL-18(-/-) mice did rely on the presence of macrophages for control of the infection. Our results suggest that IL-12p40, but not IL-18, is critical to resolution of infections with attenuated S. enterica serovar Typhimurium and that especially the effects of IL-12p40 on proliferative responses of CD4+ T cells, but not the ability of these cells to produce IFN-gamma, are important in the resolution of infection by this intracellular bacterial pathogen.

Interleukin-12, interleukin-23, and psoriasis: Current prospects

The clinical phenotype of psoriasis results from infiltration of T cells in the skin and elaboration of inflammatory cytokines. Interleukin (IL)-12 and, more recently, IL-23 have been implicated in the pathogenesis of psoriatic lesions. New therapies, including a monoclonal antibody against a subunit shared by IL-12 and IL-23, have been developed to treat psoriasis. Our purpose was to review the literature on IL-12 and IL-23 as a basis for understanding the use of anti-IL-12/IL-23 therapy for psoriasis. A review of English-language articles was performed using PubMed to identify articles pertaining to IL-12, IL-23, and psoriasis. IL-12 and IL-23 share a common subunit (p40) and have a distinct subunit (p35 and p19, respectively). Transgenic mice that overexpress IL-12 p40 develop inflammatory skin lesions. Both IL-12 knockout mice, which are deficient in IL-12, and human beings with a genetic IL-12 deficiency show increased susceptibility to intracellular pathogens and defective delayed-type hypersensitivity responses. These genetic deficiency states suggest the potential for adverse side effects from clinical administration of anti IL-12 p40 therapy. IL-12 p40 antibody was well tolerated in a phase I clinical trial with few adverse events and substantial improvements in psoriasis in most individuals. There was dose-dependent efficacy and substantial improvement in a larger cohort of patients in a phase II clinical trial. Larger and longer trials of anti IL-12/IL-23 therapies are needed to assess their clinical use and potential for infection and other adverse events.

Primary macrophages from HIV-infected adults show dysregulated cytokine responses to Salmonella, but normal internalization and killing

BACKGROUND

Adults with advanced HIV are susceptible to invasive and recrudescent infections with nontyphoidal salmonellae.

OBJECTIVES

To examine whether persistence and recurrence of salmonella infection results from HIV-related defects in macrophage internalization and intracellular killing or from ineffective type 1 cytokine responses. Such defects could be a direct consequence of macrophage HIV infection or secondary to reduced enhancement of macrophage effector functions by interferon-gamma (IFNgamma) as CD4 cell count falls.

DESIGN

Ex-vivo scientific case-control study.

METHODS

Primary ex-vivo human alveolar macrophages (huAM) from HIV-negative and HIV-positive subjects were challenged with Salmonella typhimurium under unprimed and IFNgamma-primed conditions to study internalization and intracellular killing of bacteria and cytokine responses of huAM.

RESULTS

Priming of huAM with IFNgamma reduced bacterial internalization but enhanced microbicidal activity against intracellular salmonellae. HuAM from HIV-positive subjects showed unimpaired internalization and intracellular killing of salmonellae, with and without IFNgamma priming. Opsonic and mannose receptor (CD206)-mediated entry was not required for optimal internalization. HuAM from HIV-positive subjects, however, exhibited increased secretion of tumour necrosis factor alpha (TNFalpha), interleukin (IL)-10 and IL-12 in response to S. typhimurium challenge, regardless of IFNgamma priming. This cytokine dysregulation showed a trend to a curvilinear relationship with peripheral CD4 cell count, with marked decline at values < 250 cell/mul.

CONCLUSIONS

Dysregulation of proinflammatory cytokine release, including IL-12, by macrophages during salmonella infection may underlie the susceptibility to severe salmonellosis in patients with AIDS. This defect was not reversed by IFNgamma and may represent a proinflammatory effect of HIV infection upon the macrophage or the alveolar milieu.

Production of IL-12, IL-23 and IL-27p28 by bone marrow-derived conventional dendritic cells rather than macrophages after LPS/TLR4-dependent induction by Salmonella Enteritidis

Induction of the interleukin-12 (IL-12) cytokine family comprising IL-12, IL-23, IL-27, and IL-12p40 by intracellular pathogens is required for orchestration of cell-mediated immune responses. Macrophages (MPhi) have been shown to be a source of IL-12 following TLR4-dependent activation by Salmonella (S.). In this study another antigen-presenting cell type, the conventional dendritic cell (cDC), was analyzed and its cytokine responses compared with those of MPhi. We generated bone marrow-derived conventional dendritic cells (BMDC) and macrophages (BMMPhi) by incubating murine bone marrow cells with supernatants containing granulocyte/macrophage colony-stimulating factor (GM-CSF) or macrophage colony-stimulating factor (M-CSF), respectively. Stimulation of BMDC and BMMPhi with S. enterica serovar Enteritidis (SE) or LPS resulted in the release of IL-12 and IL-23 by BMDC but not by BMMPhi. Furthermore, BMDC secreted approx. 20-fold more IL-12p40 and IL-27p28 than BMMPhi. However, BMDC and BMMPhi produced similar levels of IL-10. Using BMDC originating from wild-type (wt), TLR2(def) and TLR4(def) mice, we show that in BMDC the induction of IL-12, IL-23, and IL-27p28 by SE is dependent on TLR4, whereas low-level production of p40 is also mediated by pattern recognition receptors (PRR) other than TLR4. Interestingly, LPS- and SE-provoked responses of BMDC were remarkably similar indicating that LPS is the primary danger molecule of SE. Taken together, our results point to cDC rather than MPhi as the major producers of the IL-12 family members during in vitro infection with SE. The mechanisms of recognition of SE, however, appear to be the same for cDC and MPhi.

Lipopolysaccharide desensitizes monocytes-macrophages to CD40 ligand stimulation

Polymicrobial sepsis induces the suppression of macrophage function as determined by a reduction of pro-inflammatory cytokine production upon re-exposure to lipopolysaccharide (LPS) in vitro. Here, we examined whether macrophages were refractory to only LPS or if they were unable to respond to other stimuli such as CD40 ligand (CD40L). Monocytic cells exposed in vitro to LPS showed a dose-dependent reduction of their ability to produce interleukin-12 and tumour necrosis factor-alpha upon subsequent CD40L stimulation, as compared to cells stimulated with CD40L alone. Similarly, LPS interfered with the up-regulation of CD40, CD80 and CD86 induced by CD40L in monocytic cells. The effect of LPS on the response of monocytes to CD40L was similar whether these cells were directly exposed to LPS or cocultured with LPS-pretreated cells, indicating that soluble factors released by LPS stimulation could mediate tolerance to CD40L. We also show that the functional alterations induced by LPS in monocytes can be reversed by indomethacin, thus suggesting a role for inducible cyclooxygenase in mediating the LPS-induced hyporesponsive state of monocytes to CD40L. In conclusion, we propose that in vitro CD40L tolerance may be an appropriate model of monocyte alteration observed during septic immunosuppression and may help in the development of novel therapeutic strategies.

Immunomodulatory properties of substance P: the gastrointestinal system as a model

Communication between nerves and immune and inflammatory cells of the small and large intestine plays a major role in the modulation of several intestinal functions, including intestinal motility, ion transport, and mucosal permeability. Neuroimmune interactions at intestinal sites have been associated with the pathophysiology of infectious and enterotoxin-mediated diarrhea and intestinal inflammation, including inflammatory bowel disease (IBD). During the past 20 years the neuropeptide substance P (SP) has been identified as an important mediator in the development and progress of intestinal inflammation by binding to its high-affinity neurokinin-1 receptor (NK-1R). This peptide, released from enteric nerves, sensory neurons, and inflammatory cells of the lamina propria during intestinal inflammation, participates in gut inflammation by interacting, directly or indirectly, with NK-1R expressed on nerves, epithelial cells, and immune and inflammatory cells, such as mast cells, macrophages, and T cells. SP-dependent activation of these cells leads to the release of cytokines and chemokines as well as other neuropeptides that modulate diarrhea, inflammation, and motility associated with the pathophysiology of several intestinal disease states. The recent development of specific nonpeptide NK-1R antagonists and NK-1R-deficient mice helped us understand the functional importance of the SP-NK-1R system in mediating intestinal neuroimmune interactions and to identify the particular cells and signaling pathways involved in this response. This review summarizes our understanding on the immunomodulatory properties of SP and its receptor in the intestinal tract with particular focus on their involvement in intestinal physiology as well as in the pathophysiology of several intestinal disease states at the in vivo and cell signaling level.

Enhanced resistance to Salmonella enterica serovar Typhimurium infection in mice after coumarin treatment

Coumarin and its derivatives are naturally occurring substances with multiple biological activities. Here we demonstrate that prophylactic peroral administration of coumarin or 7-hydroxycoumarin (7-OHC) enhances resistance to subsequent lethal Salmonella enterica Serovar Typhimurium infection in mice. 7-OHC decreased bacterial load in liver and spleen, and enhanced phagocytosis and bacterial killing by macrophages when applied in vitro and in vivo. 7-OHC treatment induced significant NO release in peritoneal macrophage cultures. The observed protective effect correlated with the induction of Th1-associated cytokines, such as IL-12, IFN-gamma, and TNF-alpha. These data demonstrate a clear immunomodulatory potential of coumarins which might have important therapeutic implications to enhance resistance to infection.

Childhood asthma and measles vaccine response

BACKGROUND

Asthmatic patients have a TH2-predominant milieu that is associated with humoral immunity. However, little is known about whether humoral immune responses to viral antigens differ between asthmatic and nonasthmatic children.

OBJECTIVE

To determine whether humoral immune response differs in asthmatic patients vs nonasthmatic patients.

METHODS

Measles virus specific IgG antibody levels were determined for the Rochester Family Measles Study cohort (n = 876), a convenience sample of healthy children 5 to 12 years of age in Rochester, MN. We conducted comprehensive medical record reviews of 838 children who were eligible for this study. We determined the child's asthma status at the time of determination of antibody levels by applying predetermined criteria for asthma. Comparisons were made using the 2-sample t test or chi2 test.

RESULTS

Of the 838 children, 156 (18.6%) had asthma at the time of the determination of antibody levels and were not taking systemic steroids within 14 days of specimen collection. Among those with a nonequivocal antibody reading, the seropositive response rates were similar in asthmatic patients and nonasthmatic patients (89.7% vs 90.3%, respectively; P = .83). However, the equivocal response rates were slightly higher among asthmatic patients than nonasthmatic patients (6.4% vs 4.7%, respectively).

CONCLUSION

Asthmatic children seem to have similar humoral immune responses to measles vaccine as those without asthma. Although the findings reassure health care practitioners, whether this finding is generalizable to other vaccines and whether asthmatic patients with low antibody levels have normal cell-mediated immunity need to be elucidated in future studies.

Rationale and safety of anti-interleukin-23 and anti-interleukin-17A therapy

PURPOSE OF REVIEW

Interleukin-12 is a heterodimeric cytokine and an important mediator of the cellular immune response. The recent discovery of the novel cytokine interleukin-23 has led to a re-evaluation of interleukin-12 biology, as both cytokines use a common p40 subunit. This review discusses understanding of what distinguishes these related cytokines and the infection risks associated with targeting these cytokine pathways during treatment of inflammatory diseases.

RECENT FINDINGS

Recent work has shown that interleukin-23 stimulates the development of a distinct subset of effector T cells that produce interleukin-17A. These interleukin-17A-producing cells are critical mediators of the inflammatory response in several mouse models of autoimmunity. Although it is well established that interleukin-12 is a critical mediator of host defense, the role of the interleukin-23/interleukin-17A axis during infections has only recently been evaluated.

SUMMARY

Interleukin-12 and interleukin-23 have distinct roles in mediating host defense and autoimmune inflammation. Although targeting interleukin-12 and interleukin-23 simultaneously against the common p40 subunit is efficacious in clinical trials for human autoimmune diseases, targeting of interleukin-23 alone or the downstream effector cytokine interleukin-17A may be an effective treatment strategy for organ-specific autoimmune diseases. It is likely that targeting interleukin-23 or interleukin-17A alone, as opposed to targeting interleukin-12 and interleukin-23 together, will reduce the patients' risk of developing treatment-related infections.

Increased sensitivity to Salmonella enterica serovar Typhimurium infection in mice undergoing withdrawal from morphine is associated with suppression of interleukin-12

We have shown previously that withdrawal from morphine induces immunosuppression in mice. The present study reports the effects of morphine withdrawal on infection with Salmonella enterica serovar Typhimurium. Mice were made dependent on morphine by the implantation of a slow-release morphine pellet for 96 h. Controls received a placebo pellet. Withdrawal was induced by pellet removal. Mice were inoculated intraperitoneally with Salmonella 24 h postwithdrawal. Morphine withdrawal sensitized mice to Salmonella infection, as evidenced by increased mortality, shortened mean survival time, and increased bacterial load in the blood, spleen, and liver. Examination of the levels of a panel of proinflammatory cytokines in sera of infected, morphine-withdrawn mice showed that morphine withdrawal inhibited the elevation of interleukin-12p70 (IL-12p70). The production of IL-12p40 in morphine withdrawal mice was also suppressed. The administration of exogenous IL-12 significantly decreased the bacterial burden in morphine-withdrawn mice. These studies show a correlation between the suppression of IL-12 production and a heightened susceptibility to Salmonella infection in mice undergoing withdrawal from morphine.

The chemokine CCL2 is required for control of murine gastric Salmonella enterica infection

Salmonella enterica is a gram-negative intracellular pathogen that can cause a variety of diseases ranging from gastroenteritis to typhoid fever. The Typhimurium serotype causes gastroenteritis in humans; however, infection of mice results in an enteric fever that resembles human typhoid fever and has been used as a model for typhoid fever. The present study examined the role of the chemokine CCL2 in the control of Salmonella infection. Upon infection with salmonellae, mucosal expression of CCL2 is rapidly up-regulated, followed by systemic expression in the spleen. CCL2(-/-) mice became moribund earlier and had a higher rate of mortality compared to wild-type C57BL/6 mice. Moreover, CCL2(-/-) mice had significantly higher levels of bacteria in the liver compared to wild-type controls. Mucosal and serum interleukin-6 and tumor necrosis factor alpha levels were elevated in CCL2(-/-) mice compared to wild-type mice. In vitro analysis demonstrated that CCL2(-/-) macrophages infected with salmonellae resulted in dysregulated cytokine production compared to macrophages derived from wild-type mice. These data are the first to directly demonstrate CCL2 as a critical factor for immune responses and survival following S. enterica infection.

Interleukin-12 and -18 Levels in Peritoneal Dialysate Effluent Correlate With the Outcome of Peritonitis in Patients Undergoing Peritoneal Dialysis: Implications for the Type I/Type II T-Cell Immune Response

BACKGROUND

We previously showed that a positive impact of peritoneal defense response on the outcome of peritoneal dialysis (PD)-related peritonitis is characterized by an increased pattern of peritoneal CD4/CD8 T-cell ratio with a predominant CD4(+)-T helper subtype 1 phenotype. To further explore longitudinal changes in peritoneal immunity during PD-related peritonitis, we examined the production of interleukin 12 (IL-12), IL-18, and interferon gamma (IFN-gamma) in peritoneal dialysate effluent (PDE) and kinetic expression of the transcription factors T box expressed in T cells (T-bet) and guanine adenine thymine adenine (GATA) binding protein 3 (GATA-3) in peritoneal T cells during peritonitis. Correlations between these observations and responses to antibiotics were analyzed.

METHODS

IL-12, IL-18, and IFN-gamma protein and IFN-gamma, T-bet, and GATA-3 messenger RNA (mRNA) were measured in PDE during various phases of peritonitis in 40 patients undergoing PD. Patients were divided into 2 groups according to whether they had a rapid versus delayed response to antibiotic treatment.

RESULTS

In the early phase of peritonitis, IL-12, IL-18, and IFN-gamma levels in PDE were significantly greater in the rapid-response group (P < 0.05). Changes in peritoneal IL-12 and IL-18 levels preceded changes in IFN-gamma levels. The kinetics of IFN-gamma, T-bet, and GATA-3 mRNA expression in peritoneal T cells, measured by means of real-time polymerase chain reaction, differed between the 2 groups. In the rapid-response group, IFN-gamma and T-bet mRNA expression increased, whereas that of GATA-3 decreased over time. Results were opposite in the delayed-response group, with IFN-gamma and T-bet levels decreasing and GATA-3 levels increasing over time.

CONCLUSION

These data suggest that local IL-12 and IL-18 production is part of a protective early immune response to PD-related peritonitis. High IL-12 and IL-18 levels in PDE during the early phase of peritonitis correlated with a predominant type 1 immune response and favorable outcome.

Gamma interferon enhances internalization and early nonoxidative killing of Salmonella enterica serovar Typhimurium by human macrophages and modifies cytokine responses

Gamma interferon (IFN-gamma) is a critical cytokine in host defense against salmonella infections, but its role in phagocytic killing of intracellular Salmonella spp. has been investigated mainly in animal rather than human cells. We measured the effect of recombinant IFN-gamma (rIFN-gamma) priming on bacterial internalization, intracellular killing, oxidative burst, and cytokine release during phagocytosis of Salmonella enterica serovar Typhimurium by human monocyte-derived macrophages (MDM). Eleven-day-old MDM, primed for 72 h with rIFN-gamma (100 ng/ml) exhibited an increased proportion of cells with associated bacteria (31% versus 26%, P = 0.036) and a 67% increase in internalized bacteria per cell compared to unprimed cells (P = 0.025). Retrieval of viable bacteria following internalization was reduced 3.6-fold in 72-h primed versus unprimed MDM (interquartile range, 3.1 to 6.4) at 0.5 h due to enhanced early intracellular killing, and this difference was maintained up to 24 h. In contrast, cells primed for only 24 h exhibited no increase in early killing. MDM were competent to produce an early oxidative burst when stimulated with phorbol myristate acetate, which was fully abrogated by the respiratory burst inhibitor diphenyleneiodonium chloride (DPI), but infection of MDM with S. enterica serovar Typhimurium did not cause an increase in the early respiratory burst under unprimed or primed conditions, and DPI had no effect on the early killing of bacteria by primed or unprimed MDM. During 24 h following infection, rIFN-gamma-primed MDM released more interleukin-12 (IL-12) and less IL-10 relative to unprimed cells. We conclude that 72-h priming with rIFN-gamma increases the efficiency of internalization and nonoxidative early intracellular killing of S. enterica serovar Typhimurium by human macrophages and modifies subsequent cytokine release.

Osteoblast responses to bacterial pathogens: a previously unappreciated role for bone-forming cells in host defense and disease progression

Although the primary roles of osteoblasts are to synthesize the components of bone matrix and to regulate the activity of bone resorbing osteoclasts, there is growing realization that osteoblasts have an additional function during bone diseases, such as osteomyelitis. Based on our recent studies, we propose a novel role for osteoblasts during bacterial infections of bone, namely, the initiation and maintenance of inflammatory immune responses. In this article, we describe how these nonleukocytic cells can perceive bacterial pathogens of bone to initiate the production of an array of immune regulatory molecules. This pattern of expression is one that could promote the recruitment of leukocytes to sites of bacterial challenge, initiate antigen-specific activation of infiltrating cells, and facilitate the development of cell-mediated host responses to intracellular pathogens of bone tissue, thereby identifying this cell type as a previously unappreciated component in host responses.

Salmonella carrier state in chicken: comparison of expression of immune response genes between susceptible and resistant animals

Asymptomatic Salmonella enterica serovar Enteritidis carrier state in poultry has serious consequences on food safety and public health due to the risks of food poisoning following consumption of contaminated products. An understanding the mechanisms of persistence of Salmonella in the digestive tract of chicken can be achieved by a better knowledge of the defects in the control of infection in susceptible versus resistant animals. The gene expression of innate immune response factors including anti-microbial molecules, inflammatory and anti-infectious cytokines was studied in the caecal lymphoid tissue associated with the carrier state. Expression levels of these genes were assessed by real-time PCR and were compared in two inbred lines of chickens differing in resistance to the carrier state following oral inoculation of S. enterica serovar Enteritidis at 1 week of age. No correlation was observed between resistance/susceptibility to caecal carrier state and level of interleukin (IL)-1beta, IL-8, IL-18, inducible NO synthase (iNOS) and natural resistance associated macrophage protein 1 (NRAMP1). A high baseline level of defensin gene expression was recorded in young animals from the susceptible line. In contrast, a significantly low expression of interferon-gamma (IFN-gamma) gene was observed in these susceptible infected animals in comparison to resistant ones and healthy counterparts. IFN-gamma expression level represents a valuable indication of immunodeficiency associated with persistence of Salmonella in the chicken digestive tract, and IFN-gamma thus represents a factor to consider in the development of prophylactic measures for the reduction of Salmonella carrier state.

Cytokines in Salmonellosis

The recruitment and activation of phagocytic cells in infected tissues and the induction of T-cell- and B-cell-dependent acquired immunity are crucial for the control and resolution of Salmonella infections. These complex processes require the interaction of bacteria with a multitude of cell surface receptors and the controlled production of soluble mediators. The mechanisms of cytokine induction in response to Salmonella and the role of cytokine networks in Salmonella infections are the main foci of this review. Pathogen-associated molecular pattern receptors play an important role in recognition of bacteria by the host. Effective immunity against the bacterium therefore relies on the ability of the host to recruit phagocytes in the tissues and to enhance the antibacterial functions of these inflammatory cells. TNF-a, IFN-?, IL12, IL15, and IL18 are needed for the full expression of innate host resistance to Salmonella. The genes for mammalian cytokines can be cloned into suitable vectors and expressed in Salmonella as functional proteins. The in vivo production of cytokines by Salmonella carriers can have therapeutic applications and can modulate immune functions in the host. The possibility to modulate antigen-specific immune responses by expressing cytokines in Salmonella is illustrated by the increase in Salmonella-specific IgA responses induced by administration of IL-5-expressing bacteria. The same cytokines that are responsible for endotoxic shock are elevated in the late stages of lethal Salmonella infections, indicating that the toxicity of Salmonella lipopolysaccharide (LPS) may actually be contributing to the death of the host.

Immunomodulatory role of CXCR2 during experimental septic peritonitis

The loss of CXCR2 expression by neutrophils is a well-described, but poorly understood, consequence of clinical sepsis. To address the potential impact of this CXCR2 deficit during the septic response, we examined the role of CXCR2 in a murine model of septic peritonitis provoked by cecal ligation and puncture (CLP). CLP-induced mouse mortality was significantly attenuated with i.v. or i.p. administration of an affinity-purified murine CXCR2-specific polyclonal Ab. Mouse survival required Ab administration before and every 2 days following CLP. Furthermore, mice deficient in CXCR2 (CXCR2(-/-)) were significantly protected against CLP-induced mortality compared with control (CXCR2(+/+)) mice. The anti-CXCR2 Ab treatment delayed, but did not completely inhibit, the recruitment of leukocytes, specifically neutrophils, into the peritoneal cavity. Peritoneal macrophages from anti-CXCR2 Ab-treated mice exhibited markedly increased RNA and protein levels of several key proinflammatory cytokines and chemokines. Specifically, isolated preparations of these cells released approximately 11-fold more CXCL10 protein compared with peritoneal macrophages from control-treated or naive mice. CXCR2(-/-) mice had higher resting and CLP-induced levels of peritoneal CXCL10 compared with CXCR2(+/+) mice. Administration of a neutralizing, affinity-purified, murine CXCL10-specific polyclonal Ab before CLP in wild-type mice and every 2 days after surgery significantly increased mortality compared with control Ab-treated mice. Anti-CXCL10 treatment in CXCR2(-/-) mice negated the protective effect associated with the absence of CXCR2. In summary, these data demonstrate that the absence of CXCR2 protects mice from septic injury potentially by delaying inflammatory cell recruitment and enhancing CXCL10 expression in the peritoneum.

Intracellular adhesion molecule 1 plays a key role in acquired immunity to salmonellosis

This study investigated the role of intracellular adhesion molecule 1 (ICAM-1) during Salmonella enterica serovar Typhimurium infection of mice. We show that ICAM-1 is expressed in and around granulomas on day 4 of infection in wild-type mice. However, when naive ICAM-1(-/-) mice were challenged with a sublethal dose of serovar Typhimurium, there were no detectable differences in systemic bacterial burden over the first 9 days of infection compared to wild-type control mice. When mice were immunized with the S. enterica serovar Typhimurium vaccine strain SL2361 and then challenged with the virulent S. enterica serovar Typhimurium strain C5, 100% of the ICAM-1(-/-) mice succumbed to infection, compared to 30% of wild-type mice. T-cell responses, as measured by activation via interleukin-2 production, as well as antibody responses were comparable in the ICAM-1(-/-) and wild-type mice. Following challenge, counts in organs were significantly higher in the ICAM-1(-/-) mice, and histological examination of organs showed pathological differences. Strain SL3261-immunized wild-type mice had cellular infiltrate and normal granuloma formation in the liver and spleen on days 5 and 10 after challenge with strain C5. ICAM-1(-/-) mice had a similar infiltrate on day 5, whereas on day 10 the infiltrate was more widespread and there were fewer macrophages associated with the granulomas. High circulating levels of tumor necrosis factor alpha and gamma interferon, as well as a high burden of strain C5 in the blood, accompanied the differences in histopathology. In this study we show that ICAM-1 plays a critical role during rechallenge of immunized mice with virulent S. enterica serovar Typhimurium.

Bacterial infection induces expression of functional MHC class II molecules in murine and human osteoblasts

A growing body of evidence has shown that bacterially challenged osteoblasts can play a significant role in the initiation of inflammatory immune responses at sites of bone disease. We have recently demonstrated the surprising ability of osteoblasts exposed to bacteria to express CD40, a molecule that plays a critical costimulatory role in the activation of T lymphocytes. In the present study, we have extended our investigations into the ability of osteoblasts to interact with CD4+ T lymphocytes by determining the expression of antigen-presenting major histocompatibility complex (MHC) class II molecules in murine and human osteoblasts following exposure to two common pathogens of bone, Staphylococcus aureus and Salmonella. Cultured osteoblasts were found to respond rapidly to bacterial challenge by induction of mRNA encoding MHC class II molecules or its transcriptional regulator. Increased mRNA expression translated into expression of MHC class II proteins in murine and human osteoblasts as determined by Western blot analysis and by immunohistochemical and immunofluorescent microscopy. Furthermore, the increased surface expression of these molecules on osteoblasts exposed to bacteria was confirmed by FACS analysis. Finally, we show that bacterial challenge results in the elevated functional expression of MHC class II molecules on osteoblasts by demonstrating the enhanced ability of these cells to interact with T lymphocytes and to initiate antigen-specific T cell activation. Taken together, these data suggest a previously unappreciated role for osteoblasts in the initiation of T lymphocyte activation at sites of bacterial infection in bone tissue.

Induction of antimicrobial pathways during early-phase immune response to Salmonella spp. in murine macrophages: gamma interferon (IFN-gamma) and upregulation of IFN-gamma receptor alpha expression are required for NADPH phagocytic oxidase gp91-stimulated oxidative burst and control of virulent Salmonella spp

The effect of gamma interferon (IFN-gamma) on elevation of reactive oxygen species and the viability of virulent wild-type and avirulent mutants of Salmonella enterica serovar Typhimurium and S. enterica serovar Infantis was studied in a murine macrophage cell line (J774.2 cells). S. enterica serovar Typhimurium 14028 phoP and a rough lipopolysaccharide mutant of S. enterica serovar Infantis 1326/28 (phi(r)) (avirulent mutants) induced NADPH phagocytic oxidase gp91 (gp91(phox)) activity and a significant (P < 0.05) elevation of reactive oxygen species within 12 h without coculture with IFN-gamma. This coincided with reduced survival of S. enterica serovar Typhimurium14028 phoP or stasis of S. enterica serovar Infantis phi(r). Fluorometric studies indicated that expression of IFN-gamma on infected J774.2 cells was not significantly (P > 0.05) elevated. However, studies with the virulent S. enterica serovar Typhimurium strains showed that a comparable level of control of bacterial numbers could only be achieved by coculture with IFN-gamma. This coincided with significant upregulation of IFN-gamma receptor alpha expression on the surface of J774.2 cells and was completely abolished by N-acetyl-L-cysteine captopril (an inhibitor of reactive oxygen species). Delay in reactive oxygen species induction due to a requirement for IFN-gamma and upregulation of IFN-gamma receptor alpha in macrophages infected with virulent salmonellae may result in greater dissemination of virulent salmonellae in host tissue.

Salmonella DNA adenine methylase mutants elicit early and late onset protective immune responses in calves

Salmonellosis is an important disease of livestock and Salmonella contamination of livestock-derived food products and effluents pose a significant risk to human health. Salmonella vaccines currently available to prevent salmonellosis in cattle have limited efficacy. Here we evaluated a Salmonella enterica serovar Typhimurium vaccine strain lacking the DNA adenine methylase (Dam) for safety and efficacy in calves. Vaccination was safe in calves, and following challenge with virulent Typhimurium 4 weeks post-immunization, vaccinated animals exhibited significantly lower mortality, diarrhea, and rectal temperatures, as well as reduced colonization of gastrointestinal tract and visceral organs compared to non-vaccinated control animals. Additionally, early onset protection (competitive exclusion) in vaccinated neonatal calves was demonstrated by attenuated clinical disease (as measured by rectal temperatures and attitude scores) and reduced mortality when challenged with virulent Typhimurium 24h after immunization. Taken together, these data suggest that vaccination with Salmonella Dam mutant strains confer significant protection against Salmonella infections in cattle via both adaptive immunity and competitive exclusion mechanisms.

Anti-cytokine therapeutics and infections

In view of the increasing use of anti-cytokine-based therapies to treat autoimmune diseases, the role of specific cytokines in host defense against infection has become a highly relevant area of investigation. There are over 300,000 patients worldwide being treated with agents that specifically block the biological activities of interleukin-1 (IL-1) or tumor necrosis factor (TNF) for reducing the severity of autoimmune diseases such as rheumatoid arthritis, Crohn's disease or psoriasis. Those patients receiving anti-TNF-alpha or IL-1 blocking therapies are treated on a chronic basis. Studies suggest that other chronic inflammatory diseases will benefit from anti-cytokine therapies. However, there is a growing body of clinical evidence that neutralization of TNF-alpha is associated with an increased risk of opportunistic infections, including mycobacterial diseases. Blockade of IL-1 activity with the IL-1 receptor antagonist (IL-1Ra) appears, at present, to be relatively safe. However, because of physician under reporting (some estimates of reporting being less than 5% of these infections), the true incidence of infections, both serious and non-serious, will remain unknown. Does the increase in infections associated with anti-cytokine-based therapies come as a surprise? Of the two components of host defense, the innate and the acquired responses, which are affected by anti-cytokine therapies? From a wealth of rodent studies using live infection models, the following conclusions can be drawn: (1) neutralization or gene deletion for TNF-alpha is frequently associated with reduction of host defense in models of live Gram-positive or Gram-negative infections as well as infection by intracellular microbes such as Salmonella and Listeria; (2) absence of the IL-1 receptor can also result in decreased resistance to Listeria or Gram-positive bacteria and (3) TNF-alpha and IFN-gamma are required for defense against infection caused by Mycobacterium tuberculosis.

The innate immune response differs in primary and secondary Salmonella infection

This study examines innate immunity to oral Salmonella during primary infection and after secondary challenge of immune mice. Splenic NK and NKT cells plummeted early after primary infection, while neutrophils and macrophages (Mphi) increased 10- and 3-fold, respectively. In contrast, immune animals had only a modest reduction in NK cells, no loss of NKT cells, and a slight increase in phagocytes following secondary challenge. During primary infection, the dominant sources of IFN-gamma were, unexpectedly, neutrophils and Mphi, the former having intracellular stores of IFN-gamma that were released during infection. IFN-gamma-producing phagocytes greatly outnumbered IFN-gamma-producing NK cells, NKT cells, and T cells during the primary response. TNF-alpha production was also dominated by neutrophils and Mphi, which vastly outnumbered NKT cells producing this cytokine. Neither T cells nor NK cells produced TNF-alpha early during primary infection. The TNF-alpha response was reduced in a secondary response, but remained dominated by neutrophils and Mphi. Moreover, no significant IFN-gamma production by Mphi was associated with the secondary response. Indeed, only NK1.1(+) cells and T cells produced IFN-gamma in these mice. These studies provide a coherent view of innate immunity to oral Salmonella infection, reveal novel sources of IFN-gamma, and demonstrate that immune status influences the nature of the innate response.

Inflammatory cytokines and antigen presenting cell activation

Immune responses are stimulated in response to threats against health. In animals, defense against infectious agents, particularly rapidly growing viruses and bacteria, requires an immediate response to limit growth and dissemination, and then stimulation of a more prolonged, specific immunity to prevent re-infection. The process by which animals meet the dual needs of an immediate response to danger and initiation of long-term protection is substantially influenced by inflammatory cytokines produced primarily by macrophages and professional antigen presenting cells (APCs). Inflammatory cytokines mobilize the immune system in response to danger and increase the efficiency of an immune response as effectors of APC function. Here we review the evidence for the involvement of inflammatory cytokines in immune induction and as mediators of APC activity, with a particular emphasis on swine and on the induction of immunity at mucosal surfaces. The vast majority of infections occur at mucosal surfaces of the enteric, respiratory and reproductive tracts, and induction of protective immunity at these sites is particularly challenging. Induction of immunity at mucosal surfaces of the small intestine is greatly facilitated by the oral adjuvant, cholera toxin (CT). CT potentiates inflammatory cytokine and costimulatory molecule expression in macrophages, and stimulates humoral and cell-mediated immune responses both locally and systemically. These observations are consistent with the hypothesis that activation of APCs is a key step in the induction of antigen-specific immunity, and that inflammatory cytokine expression is a hallmark of activated APC function. The efficacy of vaccine adjuvants, particularly in the context of mucosal immunity, may be determined by their ability to induce a controlled inflammatory response in gut-associated lymphoid tissue, characterized by the expression of various costimulatory molecules and inflammatory cytokines. Thus, elucidation of the patterns of inflammatory cytokine expression and features of APC activation will help to facilitate the rational development of more efficacious vaccines.

Fimbriated Salmonella enterica serovar typhimurium abates initial inflammatory responses by macrophages

Oral immunization of mice with a Salmonella vaccine expressing colonization factor antigen I (CFA/I) from enterotoxigenic Escherichia coli results in the rapid onset of interleukin-4 (IL-4) and IL-5 production, which explains the observed elevations in mucosal immunoglobulin A (IgA) and serum IgG1 antibodies. In contrast, oral immunization with the Salmonella vector does not result in the production of Th2-type cytokines. To begin to assess why such differences exist between the two strains, it should be noted that in vitro infection of RAW 264.7 macrophages resulted in the absence of nitric oxide (NO) production in cells infected with the Salmonella-CFA/I vaccine. This observation suggests differential proinflammatory cytokine production by these isogenic Salmonella strains. Upon measurement of proinflammatory cytokines, minimal to no tumor necrosis factor alpha (TNF-alpha), IL-1alpha, IL-1beta, or IL-6 was produced by Salmonella-CFA/I-infected RAW 264.7 or peritoneal macrophages, but production was greatly induced in Salmonella vector-infected macrophages. Only minute levels of IL-12 p70 were induced by Salmonella vector-infected macrophages, and none was induced by Salmonella-CFA/I-infected macrophages. The absence of IL-12 was not due to overt increases in production of either IL-12 p40 or IL-10. CFU measurements taken at 8 h postinfection showed no differences in colonization in RAW 264.7 cells infected with either Salmonella construct, but there were differences in peritoneal macrophages. However, after 24 h, the Salmonella vector strain colonized to a greater extent in RAW 264.7 cells than in peritoneal macrophages. Infection of RAW 264.7 cells or peritoneal macrophages with either Salmonella construct showed no difference in macrophage viabilities. This evidence shows that the expression of CFA/I fimbriae alters how macrophages recognize or process salmonellae and prevents the rapid onset of proinflammatory cytokines which is typical during Salmonella infections.