IL-17 is a critical component of vaccine-induced protection against lung infection by lipopolysaccharide-heterologous strains of Pseudomonas aeruginosa

In a murine model of acute fatal pneumonia, we previously showed that nasal immunization with a live-attenuated aroA deletant of Pseudomonas aeruginosa strain PAO1 elicited LPS serogroup-specific protection, indicating that opsonic Ab to the LPS O Ag was the most important immune effector. Because P. aeruginosa strain PA14 possesses additional virulence factors, we hypothesized that a live-attenuated vaccine based on PA14 might elicit a broader array of immune effectors. Thus, an aroA deletant of PA14, denoted PA14DeltaaroA, was constructed. PA14DeltaaroA-immunized mice were protected against lethal pneumonia caused not only by the parental strain but also by cytotoxic variants of the O Ag-heterologous P. aeruginosa strains PAO1 and PAO6a,d. Remarkably, serum from PA14DeltaaroA-immunized mice had very low levels of opsonic activity against strain PAO1 and could not passively transfer protection, suggesting that an antibody-independent mechanism was needed for the observed cross-serogroup protection. Compared with control mice, PA14DeltaaroA-immunized mice had more rapid recruitment of neutrophils to the airways early after challenge. T cells isolated from P. aeruginosa DeltaaroA-immunized mice proliferated and produced IL-17 in high quantities after coculture with gentamicin-killed P. aeruginosa. Six hours following challenge, PA14DeltaaroA-immunized mice had significantly higher levels of IL-17 in bronchoalveolar lavage fluid compared with unimmunized, Escherichia coli-immunized, or PAO1DeltaaroA-immunized mice. Antibody-mediated depletion of IL-17 before challenge or absence of the IL-17 receptor abrogated the PA14DeltaaroA vaccine's protection against lethal pneumonia. These data show that IL-17 plays a critical role in antibody-independent vaccine-induced protection against LPS-heterologous strains of P. aeruginosa in the lung.     

Human C-reactive protein does not protect against acute lipopolysaccharide challenge in mice

The physiological and pathophysiological functions of C-reactive protein (CRP), the classical acute-phase protein, are not well established, despite many reports of biological effects of CRP in vitro and in model systems in vivo. Limited, small scale experiments have suggested that rabbit and human CRP may both protect mice against lethal toxicity of Gram-negative bacterial LPS. However, in substantial well-controlled studies in C57BL/6 mice challenged with Escherichia coli O111:B4 LPS, we show in this work that significant protection against lethality was conferred neither by an autologous acute-phase response to sterile inflammatory stimuli given to wild-type mice 24 h before LPS challenge, nor by human CRP, whether passively administered or expressed transgenically. Male mice transgenic for human CRP, which mount a major acute-phase response of human CRP after LPS injection, were also not protected against the lethality of LPS from either E. coli O55:B5 or Salmonella typhimurium. Even when the acute-phase human CRP response was actively stimulated in transgenic mice before LPS challenge, no protection against LPS toxicity was observed. Indeed, male mice transgenic for human CRP that were pretreated with casein to stimulate an acute-phase response 24 h before LPS challenge suffered significantly greater mortality than unstimulated human CRP transgenic controls. Rather than being protective in this situation, human CRP may thus have pathogenic proinflammatory effects in vivo.     

Experimental studies on bacterial product cantastim derived from Pseudomonas aeruginosa. VI. Protection in tolerant mice

Endotoxin tolerance is defined as a hyporesponsiveness state to a second stimulation with lipopolysaccharide (LPS). This refractory state is primarily associated with an attenuated cytokine production. Whether this down-regulation of cytokine production results in an increased susceptibility to infection remains a matter of controversy. The aim of this study was to investigate the resistance of tolerant mice to a subsequent bacterial infection and the role of bacterial immunomodulator CANTASTIM (CS) in this experimental model. We have shown that the LPS-tolerant mice (intraperitoneally inoculated with LPS Salmonella typhimurium 10 microg/mouse, daily for two days) were protected against a challenge with Pseudomonas aeruginosa (LD 100) administered 24 h later. On the contrary, when the animals were challenged 1 h after the last LPS injection, they did not survive. However if these animals were pre-treated with CS 3 days before LPS treatment, they became resistant to a subsequent bacterial challenge. More interestingly, if the treatment with LPS was substituted with CS (same schedule, route of administration and doses) there was a significant increase in the survival of mice challenged with Pseudomonas aeruginosa after either 1 h or 24 h. In this case, the increase in the rate of survival was correlated with an enhanced production of IL-10 in the peritoneal cavities of CS treated mice as compared to LPS treated mice.     

Involvement of the liver, but not of IL-6, in IL-1-induced desensitization to the lethal effects of tumor necrosis factor.

C57BL/cnb mice were found to be protected against a lethal combination of recombinant murine (m) TNF and GalN by pretreatment with several cytokines. At certain doses, rmTNF and human (h) TNF protected completely. The clearest protection was induced by rIL-1: all four rIL-1 species (both m and h, as well as alpha and beta) protected when given 12 h before the challenge. LPS and rmIFN-gamma protected weakly, whereas rmIL-6 and rhIL-6 did not protect at all. Also adrenocorticotropic hormone, dexamethasone, or dexamethasone in combination with rhIL-6 could not protect. A single IL-1 injection also completely protected mice against a lethal dose of mTNF in the absence of GalN sensitization. The desensitization by IL-1 cannot be explained by a faster clearance of the challenge TNF. In addition, we demonstrate that the IL-1-induced desensitization was only observed when a functioning liver was present, that IL-1-pretreated animals did not show decreased numbers of hepatocyte TNF receptors, and that the amount of TNF-induced IL-6 was not reduced.     

Enhanced cell-mediated protection against fatal Escherichia coli septicemia induced by treatment with recombinant IL-2

Administration of rIL-2 to BALB/c mice induces a rapid, cell-mediated response that is sufficient to protect mice from a lethal i.p. dose of Escherichia coli. Mice were protected from septic death if IL-2 was administered i.p. within 1 h after the bacterial challenge. Optimal protection was provided by treating the lethally challenged mice with rIL-2 at 1 and 5 h or 1, 5, and 10 h after the bacterial challenge and was dose-dependent (greater than or equal to 5.0 x 10(5) U/kg). Furthermore, treatment of mice with anti-IL-2R antibody abolished the protective effect induced by rIL-2 administration. These data suggest that the rIL-2-induced protection against septic death in mice is mediated by a cell type expressing a functional IL-2R. One potentially important therapeutic application of rIL-2 may be to modulate the course of sepsis once the host has been exposed to potentially lethal microbial pathogens.     

Cutting edge: bacterial lipoprotein induces endotoxin-independent tolerance to septic shock

Tolerance to bacterial cell wall components is an adaptive host response. Endotoxin/LPS tolerance is characterized by a survival advantage against subsequent lethal LPS challenge. However, it is uncertain whether LPS tolerance can afford protection against other septic challenges. In this study, we show that tolerance induced by bacterial lipoprotein (BLP) protects mice against not only BLP-induced lethality, but also LPS-, live bacteria-, and polymicrobial sepsis-induced lethality. In contrast, LPS tolerance offers no survival benefit against the latter two challenges. Furthermore, induction of BLP tolerance results in overexpression of complement receptor type 3 and FcgammaIII/IIR on neutrophils (polymorphonuclear neutrophils) and peritoneal macrophages, with increased bacterial recognition and bactericidal activity, whereas LPS-tolerized mice exhibit an impaired ability to ingest and to kill bacteria. These results indicate that BLP tolerance is a novel adaptive host response associated with a unique protective effect during septic shock.     

BCG-induced susceptibility of mice to challenge with Pseudomonas aeruginosa

Mice infected with Mycobacterium bovis, BCG, were shown to be highly susceptible to subsequent challenge with Pseudomonas aeruginosa. The susceptibility was characterized by the enhanced mortality and shortened survival after challenge with P. aeruginosa. BCG-treated mice did not show any enhanced susceptibility to challenge with Gram-positive bacteria such as Staphylococcus aureus or Listeria monocytogenes. BCG-treated mice eliminated P. aeruginosa from their organs in a pattern similar to that in untreated mice. There was no significant difference in the bactericidal activities of polymorphonuclear cells and macrophages between BCG-treated and untreated mice. An equal amount of endotoxin was detected by the Limulus lysate assay in the blood of both BCG-treated and untreated mice after challenge with P. aeruginosa. The enhanced susceptibility induced by BCG pretreatment could be decreased when the mice were rendered LPS-tolerant by injections of small amounts of LPS. These results suggest that BCG-induced susceptibility to P. aeruginosa can be ascribed to an enhanced susceptibility to the lethal effect of LPS produced by challenge bacteria, and not to the impairment of the ability to eliminate infected bacteria.     

Effect of extracellular products of Pseudoalteromonas atlantica on the edible crab Cancer pagurus

Previous studies have shown that injection of extracellular products (ECP) of Pseudoalteromononas atlantica isolated from shell disease-infected edible crabs (Cancer pagurus) into healthy crabs causes rapid death. In this study we examined the nature of the active lethal factor(s) in ECP. Injection of ECP into crabs caused a rapid decline in the total number of circulating hemocytes (blood cells), and the crabs died within 60 to 90 min. The individuals that died showed eyestalk retraction, limb paralysis, and lack of antennal sensitivity, suggesting that the active factor(s) targeted the nervous system. Histopathological investigations showed that affected crabs had large aggregates of hemocytes in the gills, and there was destruction of the tubules in the hepatopancreas. The active factor in ECP was not sensitive to heat treatment (100 degrees C for 30 min) and proteinase K digestion. As lipopolysaccharide (LPS) was a potential candidate for the lethal factor, it was purified from whole P. atlantica bacteria or ECP and subsequently injected into crabs. These crabs had all of the external symptoms observed previously with ECP, such as limb paralysis and eyestalk retraction, and they died within 90 min after challenge, although no significant decline in the number of circulating hemocytes was observed. Similarly, in vitro incubation of hemocytes with purified LPS (1 to 20 microg) from P. atlantica did not result in the clumping reaction observed with ECP but did result in a degranulation reaction and eventual cell lysis. Injection of crabs with Escherichia coli or Pseudomonas aeruginosa LPS (1 microg g of body weight(-1)) did not cause any of the characteristic symptoms observed following exposure to P. atlantica LPS. No mortality of crabs followed the injection of E. coli LPS, but P. aeruginosa LPS caused ca. 80% mortality at 2 h after injection. Overall, these results show that the main virulence factor of P. atlantica for edible crabs is LPS either alone or in combination with other heat-stable factors.     

Pharmacodynamic and protective properties of a murine lipopolysaccharide-specific monoclonal antibody in experimental Pseudomonas aeruginosa pneumonia in mice.

We employed a Pseudomonas aeruginosa mouse pneumonia model to evaluate the ability of a murine monoclonal antibody (MAb) specific for the O-side chain of P. aeruginosa Fisher Immunotype-1 lipopolysaccharide (LPS) to achieve and sustain therapeutic levels in plasma and lung tissue, reduce bacterial populations in the lung, and prevent pneumonia-associated mortality. An IgG3 MAb (Y1-5A4) administered to mice i.v. over a dose range of 125-1,000 micrograms/mouse produced plasma and lung tissue levels at 2 hr of 61-507 micrograms/ml and 4.3-150 micrograms/g, respectively. The 1,000 micrograms MAb dose reduced bacterial counts in lung tissue (log10 cfu/g +/- S.D.) and blood (log10 cfu/ml +/- S.D.) 20 hr post-treatment (18 hr post-challenge) from 10.00 +/- 0.66 to 7.66 +/- 0.91 (P less than 0.01) and from 4.39 +/- 0.81 to less than 3.0, respectively. Administration of MAb to mice in doses of 125-500 micrograms 2 hr prior to a 3 x 50% lethal bacterial challenge produced significant protection against death, with a calculated 50% protective dose of 167 micrograms. Protection was noted following administration of 1,000 micrograms of MAb up to 6 hr after bacterial challenge (P less than 0.05, compared with untreated control). Histological examination of lung tissue from infected mice revealed less acute inflammation, necrosis, and hemorrhage in MAb-treated compared with untreated control animals and greater localization of Pseudomonas antigen within the phagocytic cells in alveolar space. These findings document the in vivo therapeutic efficacy of an LPS-specific IgG MAb in a murine model of acute P. aeruginosa pneumonia, based in part upon the achievability of effective MAb concentrations in plasma and lung tissue.     

Beneficial effects of antibacterial peptide PR-39 in a neonatal murine model of endotoxic shock

The lethal effects occurring in neonatal (< 24-h old) BALB/c mice after challenge with E. coli lipopolysaccharide (LPS) were significantly counteracted by pretreatment with antibacterial peptide PR-39. Neonatal mice protection was probably related to the depressive effect of PR-39 on production of TNF-alpha known to be the major mediator of the lethal effects of neonatal endotoxic shock. Indeed, TNF-alpha plasmatic levels were consistently lower in pups pretreated with PR-39 compared with controls. Administration 24 h after challenge was no longer effective. Although PR-39 and anti-TNF-alpha doses were ineffective alone, when combined at different ratios protected neonatal mice. The present experiments show the potential use of peptide PR-39 in preventing neonatal endotoxic shock.     

Protective activities of ribosomal ribonucleic acid and lipopolysaccharide of Pseudomonas aeruginosa: a comparative study

Ribosomal ribonucleic acid (RNA) and lipopolysaccharide (LPS) from P. aeruginosa were compared with respect to their protective activities in mice against an infection with P. aeruginosa. This study is concentrated on the protective activity of RNA. RNA isolated from purified ribosomes did not contain LPS as determined with the Limulus test. Injection of RNA with the adjuvant dimethyldioctadecylammonium bromide (DDA) protected mice against P. aeruginosa without inducing LPS-specific antibodies. C₃H/HeJ mice which are relatively insensitive to the protective activity of LPS could be protected with RNA. The protective activities of RNA and LPS from a mutant strain of P. aeruginosa, PAC 605, containing defective lipopolysaccharide, were compared with the protective activities of RNA and LPS from the parent strain, PAC IR. The protective activity of LPS from PAC 605 was 1000 fold lower than the protective activity of LPS from PAC IR. RNA preparations of both strains induced similar percentages of survival. The protective activity of ribosomal RNA from P. aeruginosa was nonspecific since mice were also protected against a heterologous serotype of P. aeruginosa and against Escherichia coli. RNA from ribosomes of P. aeruginosa, E. coli and the non-lipopolysaccharide containing Saccharomyces cerevisiae had similar protective activities. No protection was obtained with the ribonucleic acid from the E. coli phage MS 2. It is concluded that ribosomal RNA has protective activities distinct from those of LPS.     

Increase of resistance to Pseudomonas aeruginosa infection in mice caused by Staphylococcus aureus]

In our study of opportunistic pathogens, we have some indication that Staphylococcus aureus can increase resistance in mice against Pseudomonas aeruginosa. Intraperitoneal injections of sublethal doses of S. aureus had a protective effect in mice against lethal doses of P. aeruginosa, more so if living and coagulase-positive S. aureus strains were injected. This protective effect was obtained both with laboratory and freshly isolated hospital strains. The interval between these infections can be extended from 2 h up to 1 week and it is still possible to observe the resistance phenomenon. The increased resistance was accompanied by a decrease in viable units of P. aeruginosa in the peritoneal cavity of mice 6 h after the injection of this species. There was no protection by S. aureus against Candida albicans in similar experimental conditions. These observations indicate that intermicrobial ecology, understood here as the previous presence of another species in a host, may be a significant factor in the resistance to infection with opportunistic pathogens such as P. aeruginosa.     

A comparison of the prophylactic and therapeutic effects of poly I:C and endotoxin in mice infected with Mengo virus.

We have compared the protective effect in AKR mice of poly I:C and bacterial endotoxins against lethal doses of Mengo virus. Administered intravenously or intraperitoneally, both interferon inducers protected mice to about the same extent from virus challenges of 2-3 LD50's. Endotoxin, however, was unable to protect the mice effectively against higher challenge doses of virus. Evidence is presented that the level of protection afforded by both inducers is related to the level of circulating interferon produced. We have also shown that a single intravenous dose of poly I:C results in the appearance of two distinct bursts of interferon activity, with maxima at about 2 h and 9 h post injection. Endotoxin, on the other hand, produced only one peak of activity, at 2 h post injection.     

Specific and non-specific mouse protection induced by different chemotypes of the Pseudomonas aeruginosa lipopolysaccharides

Abstract Lipopolysaccharides (LPS) of Pseudomonas aeruginosa were studied by the mouse active, cross-protection test. The primary structure of O-specific polysaccharides (O-repeating units) of different chemotypes was determined and their cross-protective activity demonstrated. Low doses of LPS (0.1–1 μg) stimulated chemotype-specific protection against P. aeruginosa in mice. This immunity was associated with the primary structure of the LPS and it lasted for 14 days after the first or second immunization. High doses of LPS (10–100 μg) induced cross-protection against P. aeruginosa in mice. The cross-protective capacity was caused evidently by the secondary structure or conformation of LPS molecule, i.e. by the common conformational protective determinant. This cross-protection lasted for only 5 days after the first or second immunization.     

Infection-Mediated Priming of Phagocytes Protects against Lethal Secondary Aspergillus fumigatus Challenge

Phagocytes restrict the germination of Aspergillus fumigatus conidia and prevent the establishment of invasive pulmonary aspergillosis in immunecompetent mice. Here we report that immunecompetent mice recovering from a primary A. fumigatus challenge are protected against a secondary lethal challenge. Using RAGγc knock-out mice we show that this protection is independent of T, B and NK cells. In protected mice, lung phagocytes are recruited more rapidly and are more efficient in conidial phagocytosis and killing. Protection was also associated with an enhanced expression of CXCR2 and Dectin-1 on bone marrow phagocytes. We also show that protective lung cytokine and chemokine responses are induced more rapidly and with enhanced dynamics in protected mice. Our findings support the hypothesis that following a first encounter with a non-lethal dose of A. fumigatus conidia, the innate immune system is primed and can mediate protection against a secondary lethal infection.     

Avirulent Marek’s Disease Virus Type 1 Strain 814 Vectored Vaccine Expressing Avian Influenza (AI) Virus H5 Haemagglutinin Induced Better Protection Than Turkey Herpesvirus Vectored AI Vaccine

Background

Herpesvirus of turkey (HVT) as a vector to express the haemagglutinin (HA) of avian influenza virus (AIV) H5 was developed and its protection against lethal Marek’s disease virus (MDV) and highly pathogenic AIV (HPAIV) challenges was evaluated previously. It is well-known that avirulemt MDV type 1 vaccines are more effective than HVT in prevention of lethal MDV infection. To further increase protective efficacy against HPAIV and lethal MDV, a recombinant MDV type 1 strain 814 was developed to express HA gene of HPAIV H5N1.

Methodology/Principal Findings

A recombinant MDV-1 strain 814 expressing HA gene of HPAIV H5N1 virus A/goose/Guangdong/3/96 at the US2 site (rMDV-HA) was developed under the control of a human CMV immediate-early promoter. The HA expression in the rMDV-HA was tested by immunofluorescence and Western blot analyses, and in vitro and in vivo growth properties of rMDV-HA were also analyzed. Furthermore, we evaluated and compared the protective immunity of rMDV-HA and previously constructed rHVT-HA against HPAIV and lethal MDV. Vaccination of chickens with rMDV-HA induced 80% protection against HPAIV, which was better than the protection rate by rHVT-HA (66.7%). In the animal study with MDV challenge, chickens immunized with rMDV-HA were completely protected against virulent MDV strain J-1 whereas rHVT-HA only induced 80% protection with the same challenge dose.

Conclusions/Significance

The rMDV-HA vaccine was more effective than rHVT-HA vaccine for protection against lethal MDV and HPAIV challenges. Therefore, avirulent MDV type 1 vaccine is a better vector than HVT for development of a recombinant live virus vaccine against virulent MDV and HPAIV in poultry.     

Establishment of stable cell lines producing anti-Pseudomonas aeruginosa monoclonal antibodies and their protective effects for the infection in mice.

Human-human hybridomas producing monoclonal antibodies (MoAbs) specific for five major serotypes of Pseudomonas aeruginosa were developed by fusing P. aeruginosa primed and Epstein-Barr virus-transformed cells with human myeloma P109 cells using polyethyleneglycol. The MoAbs which were produced by the hybridomas were protective against lethal intraperitoneal (i.p.) challenge of P. aeruginosa (10 LD50) in mice. The 50% effective dose (ED50) values of MoAbs ranged from 0.5 to 10.2 micrograms/mouse and were 26 to 240 times more protective than a commercial human IgG preparation. MoAb administration to mice promoted bacterial clearance in peritoneal cavity, and prevented bacterial invasion into blood in the way of increasing both the number of bacteria trapped by a macrophage and the ratio of macrophages that trapped bacteria. MoAbs also showed protective effects against lethal infection of P. aeruginosa in the mice which were decreased in polymorphonuclear cells (PMN) by cyclophosphamide (CY). All MoAbs showed serotype-specific binding to the clinical isolates of P. aeruginosa as well as to the immunized strains. The hybridoma cell lines maintained their capacity to produce MoAb continuously for more than 12 months and produced 10 to 60 micrograms MoAbs per 10(6) cells in 24 hr. It is practicable to use these cell lines for large-scale production of anti-P. aeruginosa MoAbs and such MoAbs must be useful for the therapeutics of patients with P. aeruginosa infection.     

Protective Immunity against Lethal F. tularensis holarctica LVS Provided by Vaccination with Selected Novel CD8+ T Cell Epitopes

Recently we described an unbiased bacterial whole-genome immunoinformatic analysis aimed at selection of potential CTL epitopes located in “hotspots” of predicted MHC-I binders. Applying this approach to the proteome of the facultative intra-cellular pathogen Francisella tularensis resulted in identification of 170 novel CTL epitopes, several of which were shown to elicit highly robust T cell responses. Here we demonstrate that by DNA immunization using a short DNA fragment expressing six of the most prominent identified CTL epitopes a potent and specific CD8+ T cell responses is being induced, to all encoded epitopes, a response not observed in control mice immunized with the DNA vector alone Moreover, this CTL-specific mediated immune response prevented disease development, allowed for a rapid clearance of the bacterial infection and provided complete protection against lethal challenge (10LD₅₀) with F. tularensis holarctica Live Vaccine Strain (LVS) (a total to 30 of 30 immunized mice survived the challenge while all control DNA vector immunized mice succumbed). Furthermore, and in accordance with these results, CD8 deficient mice could not be protected from lethal challenge after immunization with the CTL-polyepitope. Vaccination with the DNA poly-epitope construct could even protect mice (8/10) against the more demanding pulmonary lethal challenge of LVS. Our approach provides a proof-of-principle for selecting and generating a multi-epitpoe CD8 T cell-stimulating vaccine against a model intracellular bacterium.     

Protection of mice against bacterial infection by oral administration of bacterial lipopolysaccharide

The effect of orally administered bacterial lipopolysaccharide (LPS) on host resistance against bacterial infections was studied. LPS orally given for 5 consecutive days prior to infection caused no apparent toxic effect and protected mice against Pseudomonas aeruginosa and Listeria monocytogenes infections.     

Effect of sulfatide on acute lung injury during endotoxemia in rats

Experimental studies have shown that intrapulmonary leukocyte sequestration and activation is implicated in the pathogenesis of acute lung injury during endotoxemia. Selectins are involved in the adhesion of leukocyte to the endothelium. Sulfatide is recognized by P selectin and blocks this adhesion molecule. We studied the effects of sulfatide on endotoxin-induced lung damage in rats. Endotoxin shock was produced in male rats by a single intravenous (i.v.) injection of 20 mg/kg of Salmonella enteritidis lipopolysaccharide (LPS). LPS administration reduced survival rate (0%, 72 h after endotoxin challenge) decreased mean arterial blood pressure (MAP), produced leukopenia (Controls = 11,234+/-231 cells/mL, LPS = 4,567+/-123 cells/mL) and increased lung myeloperoxidase activity (MPO; a marker of leukocyte accumulation) in the lung (Controls = 0.35+/-0.1 U/g/tissue; LPS = 10+/-1.2 U/g/tissue). Furthermore LPS administration markedly impaired the concentration-response curves for acetylcholine and sodium nitroprusside in isolated pulmonary arterial rings. There was also an increased staining for P-selectin in the pulmonary arteries. Sulfatide treatment (10 mg/kg, 30 min. after LPS challenge), significantly protected against LPS-induced lethality (90% survival rate and 70% survival rate 24 h and 72 h after LPS injection), reduced LPS induced hypotension, reverted leukopenia (8,895+/-234 cells/ml) and lowered lung MPO activity (1.7+/-0.9 U/g/tissue). Furthermore sulfatide restored to control values the LPS-induced impairment in arterial pulmonary vasorelaxation and reduced P-selectin immunostaining. Our data indicate that sulfatide attenuates LPS-induced lung injury and protects against endotoxin shock.