Murine Wound Model Research Articles

In Vitro and In Vivo Activities of a New Cephalosporin, FR264205, against Pseudomonas aeruginosa

FR264205 is a novel parenteral 3'-aminopyrazolium cephalosporin. This study evaluated the in vitro and in vivo activities of FR264205 against Pseudomonas aeruginosa. The MIC of FR264205 at which 90% of 193 clinical isolates of P. aeruginosa were inhibited was 1 microg/ml, 8- to 16-fold lower than those of ceftazidime (CAZ), imipenem (IPM), and ciprofloxacin (CIP). FR264205 also exhibited this level of activity against CAZ-, IPM-, and CIP-resistant P. aeruginosa. The reduction in the susceptibility of FR264205 by AmpC beta-lactamase was lower than that of CAZ, indicating a relatively high stability of FR264205 against AmpC beta-lactamase, the main resistance mechanism for cephalosporins. Neither expression of efflux pumps nor deficiency of OprD decreased the activity of FR264205. No spontaneous resistance mutants were selected in the presence of FR264205, and the reduction in susceptibility to FR264205 was lower than that to CAZ, IPM, and CIP after serial passage, suggesting that FR264205 has a low propensity for selecting resistance. In murine pulmonary, urinary tract, and burn wound models of infection caused by P. aeruginosa, the efficacy of FR264205 was superior or comparable to those of CAZ and IPM. These results indicate that FR264205 should have good potential as an antibacterial agent for P. aeruginosa.

Closure of mid-gestational excisional wounds in a novel fetal mouse model

INTRODUCTION: Studies utilizing mid-gestational wounds have been used to improve our understanding of excisional wound healing with mixed results; rabbit wounds expand while lamb wounds contract. We developed a murine excisional wound model and theorized that mid-gestational wounds would expand with minimal alphasmooth muscle actin(aSMA) expression, a marker for myofibroblasts, when compared with late-gestational wounds.

Efficacy of Antibodies against the N-Terminal of Pseudomonas aeruginosa Flagellin for Treating Infections in a Murine Burn Wound Model

In an era of increasing drug resistance, immunotherapy is a desirable treatment against Pseudomonas aeruginosa infections. The flagellum, which is an important pseudomonal virulence factor, was targeted for immunotherapy. The aim of the study was to evaluate the efficacy of polyclonal immunotherapy targeted against the N-terminal of flagellin (anti-N'-fla-b) for treating severe P. aeruginosa infection in a murine burn wound model. Groups of 12 mice were infected (subeschar) with P. aeruginosa strain PA01, and were treated either with systemic anti-N'-fla-b immunoglobulin G (IgG), nonspecific IgG, or imipenem. The control groups included mice with burn alone, mice with untreated infected burn, and mice without burn infected with P. aeruginosa. Three separate regimens were examined: prophylaxis (preinfection), therapeutic (postinfection), and combined. The efficacy of anti-N'-fla-b was evaluated by monitoring the mortality and morbidity (relative weight loss) during a period of 2 weeks. Anti-N'-fla-b IgG immunotherapy significantly decreased the mortality rate of infected burned mice followed by severe P. aeruginosa infection. The mortality rate in the anti-N'-fla-b-treated groups ranged from 0 to 17 percent compared with 58 to 83 percent in nontreated groups infected with 2 to 5 x 10(6) colony-forming units of P. aeruginosa (p < 0.05). The mortality rate in the anti-N'-fla-b-treated groups was similar to that of groups treated with imipenem. The three tested regimens yielded similar results. Morbidity paralleled survival results. Histopathologic examination revealed an earlier reepithelialization of the infected wound in the anti-N'-fla-b-treated mice compared with untreated mice. Immunotherapy with anti-N'-fla-b IgG, given either as prophylaxis or therapeutically, effectively reduced mortality and morbidity and improved wound healing in a severely P. aeruginosa-infected murine burn model.

A Multitargeted Receptor Tyrosine Kinase Inhibitor, SU6668, Does Not Affect the Healing of Cutaneous Full-Thickness Incisional Wounds in SKH-1 Mice

Disturbances of angiogenesis have been suggested to result in the impaired healing of skin wounds. Using a murine incisional wound model, we evaluated the effects of SU6668, an inhibitor of the receptors for vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF), and fibroblast growth factor (FGF), on the healing of skin wounds. Mice were administered vehicle, SU6668 (100 or 400 mg/kg/day, b.i.d.), or dexamethasone (1 mg/kg/day, b.i.d.), and wound healing was monitored histologically and using a tensiometer. SU6668 at a fully efficacious dose of 100 mg/kg/day had no significant effect on the healing process, while at a supratherapeutic dose of 400 mg/kg/day, there were subtle transient histologic changes and slight decreases in tensile strength, suggesting a slight delay in the wound healing process. In conclusion, these data indicate that inhibition of the receptors for VEGF, PDGF, and FGF at levels necessary to inhibit tumor growth in mouse xenograft models does not affect the healing of incisional wounds in mice. Redundant pathways likely compensate for inhibition of VEGF, PDGF, and FGF signaling pathways in the skin healing process.

The Effect of AgK114 on Wound Healing

AgK114 is a newly isolated membrane-associated protein which is expressed on keratinocytes. Its expression is restricted to dermal sheath cells near sebaceous glands in normal skin. However, it is transiently induced by UV exposure or injury stimulation (Tatefuji T. et al., Biol. Pharm. Bull., 27, 1742-1749, 2004). Thus, the expression pattern of AgK114 suggested its potential role in wound healing response. We report here that expression of AgK114 is induced in the initial 24 h at the edge keratinocytes during keratinocyte migration, followed by disappearance once epithelialization is completed in the murine excisional wound model. We also demonstrate that exogenous recombinant mouse AgK114FL promoted wound healing process. Mouse AgK114FL up-regulated pro-matrix-metalloproteinase-9, vascular endothelial growth factor, transforming growth factor-beta, IL-6, and IL-1beta production in the early stage of wound tissue. Moreover, mouse AgK114FL induced the matrix-metalloproteinase-9 activity of wound fibroblasts prepared from impaired skin in the presence of proinflammatory cytokines. These results suggest that the AgK114 participates in the wound response during the healing process, and promotes wound repair.

Transplantation of Endothelial Progenitor Cells Accelerates Dermal Wound Healing with Increased Recruitment of Monocytes/Macrophages and Neovascularization

Endothelial progenitor cells (EPCs) act as endothelial precursors that promote new blood vessel formation and increase angiogenesis by secreting growth factors and cytokines in ischemic tissues. These facts prompt the hypothesis that EPC transplantation should accelerate the wound-repair process by facilitating neovascularization and the production of various molecules related to wound healing. In a murine dermal excisional wound model, EPC transplantation accelerated wound re-epithelialization compared with the transplantation of mature endothelial cells (ECs) in control mice. When the wounds were analyzed immunohistochemically, the EPC-transplanted group exhibited significantly more monocytes/macrophages in the wound at day 5 after injury than did the EC-transplanted group. This observation is consistent with enzyme-linked immunosorbent assay results showing that EPCs produced in abundance several chemoattractants of monocytes and macrophages that are known to play a pivotal role in the early phase of wound healing. At day 14 after injury, the EPC-transplanted group showed a statistically significant increase in vascular density in the granulation tissue relative to that of the EC-transplanted group. Fluorescence microscopy revealed that EPCs preferentially moved into the wound and were directly incorporated into newly formed capillaries in the granulation tissue. These results suggest that EPC transplantation will be useful in dermal wound repair and skin regeneration, because EPCs both promote the recruitment of monocytes/macrophages into the wound and increase neovascularization.

Hyperoxia improves microvascular perfusion in a murine wound model

There is a need for a noninvasive method that measures wound angiogenesis. Hyperoxia is known to increase the appearance of new blood vessels in wounds, yet no study has confirmed increases in wound bed perfusion with periodic hyperbaric oxygen (HBO) exposure. This study investigates whether laser Doppler imaging is able to detect and quantify the enhancement of wound angiogenesis that is known to occur with intermittent HBO treatments. Full-thickness dorsal dermal wounds were created on mice randomized to hyperoxic (n = 14) and control (n = 15) groups. Hyperbaric oxygen was administered twice daily for 90 minutes each at 2.1 atmospheres for 7 days. Wound bed perfusion was measured by laser Doppler imaging on days 0, 7, and 10 postwounding. Wound blood flow increased significantly over baseline on day 7 and 10 in the hyperoxic group, but only on day 10 in the control group. Comparison between groups showed a 20% statistically significant increase in wound perfusion in HBO-treated animals compared to control on day 10 (p = 0.05). Laser Doppler imaging was able to detect and quantify the increase in wound bed perfusion resulting from intermittent HBO treatments and shows promise as a noninvasive measure of angiogenesis and wound healing.

Photonic Monitoring in Real Time of Vascular Endothelial Growth Factor Receptor 2 Gene Expression under Relaxin‐Induced Conditions in a Novel Murine Wound Model

Relaxin is known to promote vascular endothelial growth factor (VEGF) expression in reproductive tissue, and successful wound healing depends on good vascularization of wound sites, a process that relaxin may facilitate. Thus, the objective of this study was to evaluate the efficacy of relaxin on the development of vascular tissue at wound sites in a novel VEGF receptor 2-luc (VEGFR2-luc) transgenic mouse wound model by monitoring the rate of VEGFR2-luc-mediated gene expression using bioluminescence and real-time imaging. To this end, 12 FVB/N VEGFR2-luc transgenic male mice were assigned to treatments (six per group): saline alone or relaxin (1 g/6 h/14 days) administered intraperitoneally (i.p.). On day 0, a set of full-thickness wounds (6-mm punch) were generated under anesthesia on the dorsal aspect of each mouse. Photonic emissions were recorded (5-min collection of photons) from wound sites 10 min after the administration of luciferin (150 mg/kg i.p.) on day 0 and on days 1, 2, 4, 7, 9, 11, and 14 postwounding to quantify luciferase activity using an IVIS 100 biophotonic imaging system. Animals were sacrificed (three per group) on day 7 or 14, and wound tissue specimens were recovered for molecular and histologic analyses. Although photonic emission from wound sites increased (P < .001) over time with peak values obtained by day 7, no significant (P > .05) effect of relaxin treatment on VEGFR2-luc gene expression was noted at wound sites. Whereas measuring relaxin's effect on angiogenesis indirectly via the VEGFR2 model was not successful, photonic imaging provides an exciting new tool using alternative models (i.e., VEGF-luc mouse) to study relaxin-induced gene expression in normal (i.e., wound healing) or tumorigenic tissues in real time.

The effect of topical tretinoin on tissue strength and skin components in a murine incisional wound model

Vitamin A derivatives modulate the inflammatory phase in wound healing. Retinoic acid can restore decreased tensile strength and collagen content in steroid- or diabetes-impaired wounds. It is hypothesized that retinoic acid can lead to accelerated healing with improved breaking strength in unimpaired incisional wounds. Skin incisions were made in 45 CD-1 mice. The sutured wounds were treated once daily with topical all-trans-retinoic acid 0.1% (n = 15), vehicle ointment (n = 15), or left untreated (n = 15). Skin biopsies at 1-, 2-, and 3-week intervals were examined using hematoxylin and eosin (H&E), Masson's trichrome, and immunoperoxidase staining methods. Wound breaking strength was determined by biomechanical analysis. Incisions treated with retinoic acid exhibited a significantly reduced breaking strength at week 1 when compared to the vehicle and control group. Histologic examination showed a prolonged inflammatory reaction with abundant deposition of granulation tissue. Despite an increased fibroplastic proliferation in the tretinoin-treated wounds, the production of collagen was diminished. Topical retinoic acid does not enhance the healing of unimpaired incisional wounds. The inadequate tensile strength in the early phase of the healing process is possibly the result of an increased dermal inflammatory response and the decreased collagen content. Although these adverse effects disappeared by 3 weeks postwounding, we found no discernible benefit of supplemental retinoic acid in unimpaired wounds.

Aberrant mucosal wound repair in the absence of secretory leukocyte protease inhibitor.

Secretory leukocyte protease inhibitor (SLPI) is a cationic serine protease inhibitor with anti-microbial and anti-inflammatory properties found in large quantities in mucosal fluids, including saliva. SLPI is expressed during cutaneous wound healing, however, its role in oral wound repair is unknown. We have used a novel approach involving a murine buccal mucosal acute wound model to investigate the role of SLPI in oral healing. In parallel to the observed cutaneous healing phenotype, an absence of SLPI results in markedly impaired oral wound healing associated with increased inflammation and raised elastase activity. Moreover, matrix deposition was decreased, while MMP activity was enhanced in the oral SLPI null wounds suggesting deregulated proteolysis. Intriguingly, regardless of genotype, reduced collagen deposition was observed in oral compared to dermal wounds, associated with reduced TGF-beta expression and decreased fibroblast collagen expression in vitro. We propose that SLPI is a pivotal endogenous factor necessary for optimal tissue repair including intra-oral wound healing. In addition, our model provides a unique opportunity to delineate the cellular and molecular mechanisms underlying the differences between dermal scarring and oral scar-free healing.

Loss of hemolysin expression in Staphylococcus aureus agr mutants correlates with selective survival during mixed infections in murine abscesses and wounds

During the screening of a Staphylococcus aureus signature-tagged mutagenesis library, it was noted that nonhemolytic bacteria became more abundant as time passed in murine abscess and wound models, but not within organ tissues associated with systemic infections. To examine this further, a mixed population of hyperhemolytic, hemolytic, and nonhemolytic S. aureus strain RN6390 cells were inoculated into mice using abscess, wound, and systemic models of infection. After 7 days in the abscess, the hyperhemolytic group markedly declined, whereas the nonhemolytic population increased significantly. A similar phenomenon occurred in murine wounds, but not during the systemic infection. Sequencing of several of the signature-tagged mutants indicated mutations in the agrC gene or within the agrA–agrC intergenic region. Both α-hemolysin and δ-hemolysin activity was curtailed in these mutants, but β-hemolysin activity was unaffected. Single strain comparisons between wild-type strain 8325-4 and strain DU1090 ( hla-) as well as between strain RN6911 ( agr) and wild-type strain RN6390 were performed using the same three animal models of infection. The agr mutant strain and the hla mutant strain showed no difference in bacterial counts in murine wounds compared to their respective parent strains. The same held true in murine abscesses at day 4, but strain RN6911 counts then declined at day 7. Considerable clearing of the hla mutant strain and the agr mutant strain occurred in the systemic model of infection. Mixed infections with the DU1090 and 8325-4 strains in the abscess model showed a slight advantage given to the DU1090 population, but a distinct selection for the parental 8325-4 strain in the liver. These results suggest that agr mutations cause reductions in the expression of several secreted proteins, including α- and δ-hemolysin, which in turn contribute to a growth advantage of this agr mutant group within a mixed population of S. aureus cells residing in abscesses and wounds.

Bacterial Colonization and the Expression of Inducible Nitric Oxide Synthase in Murine Wounds

The expression of inducible nitric oxide synthase (iNOS) in two different murine wound models was investigated. Animals were subjected to either full-thickness linear skin incision with subcutaneous implantation of sterile polyvinyl alcohol sponges, or to 1.5 x 1.5-cm dorsal skin excision. Reverse transcriptase-polymerase chain reaction detected iNOS mRNA in all cell samples retrieved from the sponges. Immunoblotting of lysates of inflammatory cells harvested from the sponges failed to detect iNOS protein, and immunohistochemistry of the incisional wound was mildly positive. Inflammatory cells of excisional wounds stained strongly positive for iNOS. Cutaneous wounds were found to be colonized with Staphylococcus aureus. The detection of iNOS in cells from sponges inoculated in vivo with heat-killed bacteria and the reduction of immunohistochemical signal for iNOS in excisional wounds of animals treated with antibiotics support a role of bacteria in the induction of iNOS in wounds. The expression of iNOS in excisional wounds requires interferon-gamma and functional lymphocytes because interferon-gamma knockout and SCID-Beige mice exhibited attenuated iNOS staining in excisional wounds. The expression of iNOS in the inflammatory cells of murine wounds is a response to bacterial colonization and not part of the normal repair process elicited by sterile tissue injury.

Nicotine Accelerates Angiogenesis and Wound Healing in Genetically Diabetic Mice

Recently, we have discovered an endogenous cholinergic pathway for angiogenesis mediated by endothelial nicotinic acetylcholine receptors (nAChRs). Since angiogenesis plays a major role in wound repair, we hypothesized that activation of nAChRs with nicotine would accelerate wound healing in a murine excisional wound model. In genetically diabetic and control mice full-thickness skin wounds (0.8 cm) were created on the dorsum and topically treated over 7 days with either vehicle (phosphate-buffered saline, PBS) or nicotine (10(-8) mol/L, 10(-9) mol/L; each, n = 5). Wound size was measured over 14 days followed by resection, histological analysis, and quantitation of vascularity. In diabetic animals an agonist (epibatidine, 10(-10) mol/L) or antagonist (hexamethonium, 10(-4) mol/L) of nAChRs as well as the positive control basic fibroblast growth factor (bFGF, 25 microg/kg) were also tested. To further study the role of endothelial nAChRs in angiogenesis, we used an ex vivo vascular explant model. In diabetic mice wound healing was markedly impaired. Nicotine significantly accelerated wound healing as assessed by closure rate and histological score. The effects of nicotine were equal to bFGF and were mimicked by epibatidine and blocked by hexamethonium. Histomorphometry revealed increased neovascularization in animals treated with nicotine. Furthermore, capillary-like sprouting from vascular explants was significantly enhanced by nicotine. In conclusion, agonist-induced stimulation of nAChRs accelerates wound healing in diabetic mice by promoting angiogenesis. We have discovered a cholinergic pathway for angiogenesis that is involved in wound healing, and which is a potential target for therapeutic angiogenesis.

Wound-induced angiogenesis and its pharmacologic inhibition in a murine model

A novel synthetic compound, SU5416, inhibits subcutaneous tumor growth of cells. Because angiogenesis in tumor growth and wound healing involves similar mechanisms, we examined whether SU5416 inhibits wound-induced angiogenesis. Sixteen female BALB/c mice were randomized to receive either SU5416 (n = 8) or vehicle alone (n = 8) on day -2. On day 0, transparent window chambers were implanted into the dorsal skin flap. Treatment was stopped on day 7. On days 1, 7, and 14, micrographs of the windows were taken and microvessel density was estimated. On day 1, no statistically significant difference was noted between the microvessel density in controls and treatments. After the mice underwent treatment from day -2 to day 7 and microvessel densities were analyzed on day 7, angiogenesis was significantly inhibited in the SU5416 group (P <.001). Seven days after cessation of treatment, however, the SU5416 group showed complete recovery in angiogenesis. The increase in microvessel density in the SU5416 group on day 14 from day 7 was not significantly different from that of the control group (P >.05). We observed that SU5416, a known inhibitor of tumor-induced angiogenesis, also inhibited wound-induced angiogenesis in our murine wound model. This inhibitory effect is significant while the mice are undergoing treatment.

Locally delivered antibodies combined with systemic antibiotics confer synergistic protection against antibiotic-resistant burn wound infection.

Nosocomially derived gram-negative infections, particularly from antibiotic-resistant pathogens, are a cause of morbidity in patients with severe burn wounds. Locally delivered polyclonal antibodies and systemically infused ceftazidime were combined in a lethal murine burn wound model against a virulent Pseudomonas aeruginosa strain that exhibits intermediate resistance to ceftazidime. Survival was synergistically enhanced in cohorts of burned mice treated both locally (subeschar) with pooled polyclonal human immunoglobulin G (1-mg dose) and intravenously with infused ceftazidime (0.44 mg dose). Enhancement of survival correlated with reduced bacterial quantitation in local and systemic tissue observed in separate burned cohorts. Burned, infected mice treated prophylactically with either individual treatment at the same dose or a combination of both treatments administered systemically showed no survival enhancement as compared with the untreated control group. Treatment of antibiotic-resistant burn wound infections with antibiotics together with locally delivered immunoglobulins may improve antibiotic protective effects against antibiotic-resistant pathogens.

Is human fracture hematoma inherently angiogenic?

This study attempts to explain the cellular events characterizing the changes seen in the medullary callus adjacent to the interfragmentary hematoma during the early stages of fracture healing. It also shows that human fracture hematoma contains the angiogenic cytokine vascular endothelial growth factor and has the inherent capability to induce angiogenesis and thus promote revascularization during bone repair. Patients undergoing emergency surgery for isolated bony injury were studied. Raised circulating levels of vascular endothelial growth factor were seen in all injured patients, whereas the fracture hematoma contained significantly higher levels of vascular endothelial growth factor than did plasma from these injured patients. However, incubation of endothelial cells in fracture hematoma supernatant significantly inhibited the in vitro angiogenic parameters of endothelial cell proliferation and microtubule formation. These phenomena are dependent on a local biochemical milieu that does not support cytokinesis. The hematoma potassium concentration is cytotoxic to endothelial cells and osteoblasts. Subcutaneous transplantation of the fracture hematoma into a murine wound model resulted in new blood vessel formation after hematoma resorption. This angiogenic effect is mediated by the significant concentrations of vascular endothelial growth factor found in the hematoma. This study identifies an angiogenic cytokine involved in human fracture healing and shows that fracture hematoma is inherently angiogenic. The differences between the in vitro and in vivo findings may explain the phenomenon of interfragmentary hematoma organization and resorption that precedes fracture revascularization.

Role of alpha(v) integrins and angiogenesis during wound repair.

Angiogenesis, the formation of new blood vessels from pre-existing blood vessels, is thought to be critical for wound repair. Yet few studies have critically examined dermal wound repair in a system in which angiogenesis was impaired. Since alpha(v)-containing integrins are critical for angiogenesis, we administered either an alpha(v) integrin blocking antibody or cyclic Arg-Gly-Asp peptide into a murine excisional wound model to restrict wound angiogenesis. Although both methods markedly decreased wound angiogenesis, decreased angiogenesis had no significant effect on wound epithelization, contraction, or ultimate wound closure. These results suggest that if other cellular components of wound healing are intact, moderate impairment of angiogenesis alone does not necessarily retard normal wound healing.

Efficacy of locally delivered polyclonal immunoglobulin against Pseudomonas aeruginosa infection in a murine burn wound model

The leading cause of morbidity and mortality in severe burn wound patients is infection. Treatment of burn wound infection is complicated by the emergence of antibiotic resistant organisms. A potential therapeutic alternative to antibiotic drugs is the local administration of polyclonal antibodies, termed passive local immunotherapy (PLI), directly to the burned tissue. A mouse burn wound infection model to simulate full thickness burn wound infection was used to evaluate the efficacy of passive local immunotherapy as a viable prophylactic or therapeutic agent. Pooled human immunoglobulins (IgG), delivered locally to the site of infection, are shown to be more effective at preventing fatal burn wound sepsis than treatment by intravenous infusion of IgG. A single 10 mg dose of human IgG administered locally to the burned, infected tissue site, either 24 hours prior to bacterial challenge, or within 3 hours after bacterial challenge, enhanced animal survival significantly ( P<0.001 and P<0.05 respectively) compared to control animals. In addition, reduced levels of bacteria were found in local and systemic tissues of IgG-treated mice compared to control mice ( P<0.05). These data support the local use of polyclonal immunoglobulin preparations as an efficacious and cost effective means to prevent and treat burn wound infections.

Temporal activity of plasminogen activators and matrix metalloproteinases during cutaneous wound repair

Background: Response to tissue injury begins with the deposition of a fibrin-rich clot or the provisional matrix. The provisional matrix consists of plasma-borne matrix molecules that serve as scaffolding for the ensuing migration of cells. During wound repair multiple cell types must migrate through the clot-matrix scaffolding. The migration of these cells through the matrix is dependent on the activity of the fibrinolytic and proteolytic systems, which include the plasminogen activator (PA) system and matrix metalloproteinases (MMP). The aim of this study was to better understand the temporal activity of these enzymes during normal wound repair. Methods: We used the murine excisional wound model and extracted proteins under nonreducing conditions. With use of gelatin and casein zymography, we determined the activity of the MMPs during the course of wound repair. In addition, we quantified the activity of MMP-2 and MMP-9 by a standardized assay. Plasminogen zymograms were used to detect urokinase PA and tissue PA activity. Western blots were used to detect the natural inhibitor of PAs, plasminogen activator inhibitor type 1. Results: Our results demonstrate the temporal activity of MMP-2, MMP-3, MMP-7, and MMP-9 during the course of normal dermal repair. The activity of urokinase PA and tissue PA were also determined; it preceded the activity of the MMPs. Conclusions: We demonstrate the temporal activity of the 2 protease families, MMPs and PAs, in the normal process of cutaneous wound healing. (Surgery 1999;125:587-93.)

Protection against fatal Pseudomonas aeruginosa burn wound sepsis by immunization with lipopolysaccharide and high-molecular-weight polysaccharide.

A murine burn wound model was employed to evaluate the relative efficacy of purified Pseudomonas aeruginosa lipopolysaccharide (LPS) and high-molecular-weight polysaccharide as protective immunogens. LPS was found to be both highly immunogenic and protective. As little as three 0.001-microgram doses elicited good immunoglobulin M and G titers and increased the mean lethal dose more than 1,000-fold. The level of protection against a live challenge correlated with antibody titers and was found to be serotype specific. An immunizing regimen which evoked only an immunoglobulin M response was still found to offer substantial protection. Immunization with a high-molecular-weight polysaccharide was also found to be protective. However, approximately 1,000-fold more high-molecular-weight polysaccharide, as compared with LPS, was needed to protect mice to an equivalent degree. Immunization with LPS was found to promote bacterial clearance and prevent establishment of bacteremia. A multivalent LPS vaccine conferred high levels of protection (110- to 53,000-fold) against eight different challenge strains of various serotypes.