Comparative immunochemistry of lipopolysaccharides from typable and polyagglutinable Pseudomonas aeruginosa strains isolated from patients with cystic fibrosis

Immune Response to Biofilm Growing Pulmonary Pseudomonas aeruginosa Infection

Biofilm infections are tolerant to the host responses and recalcitrance to antibiotic drugs and disinfectants. The induced host-specific innate and adaptive immune responses by established biofilms are significantly implicated and contributes to the course of the infections. Essentially, the host response may be the single one factor impacting the outcome most, especially in cases where the biofilm is caused by low virulent opportunistic bacterial species. Due to the chronicity of biofilm infections, activation of the adaptive immune response mechanisms is frequently experienced, and instead of clearing the infection, the adaptive response adds to the pathogenesis. To a high degree, this has been reported for chronic Pseudomonas aeruginosa lung infections, where both a pronounced antibody response and a skewed Th1/Th2 balance has been related to a poorer outcome. In addition, detection of an adaptive immune response can be used as a significant indicator of a chronic P. aeruginosa lung infection and is included in the clinical definitions as such. Those issues are presented in the present review, along with a characterization of the airway structure in relation to immune responses towards P. aeruginosa pulmonary infections.

Lipid-Protein and Protein-Protein Interactions in the Pulmonary Surfactant System and Their Role in Lung Homeostasis

Pulmonary surfactant is a lipid/protein complex synthesized by the alveolar epithelium and secreted into the airspaces, where it coats and protects the large respiratory air–liquid interface. Surfactant, assembled as a complex network of membranous structures, integrates elements in charge of reducing surface tension to a minimum along the breathing cycle, thus maintaining a large surface open to gas exchange and also protecting the lung and the body from the entrance of a myriad of potentially pathogenic entities. Different molecules in the surfactant establish a multivalent crosstalk with the epithelium, the immune system and the lung microbiota, constituting a crucial platform to sustain homeostasis, under health and disease. This review summarizes some of the most important molecules and interactions within lung surfactant and how multiple lipid–protein and protein–protein interactions contribute to the proper maintenance of an operative respiratory surface.

The O-specific polysaccharide lyase from the phage LKA1 tailspike reduces Pseudomonas virulence

Pseudomonas phage LKA1 of the subfamily Autographivirinae encodes a tailspike protein (LKA1gp49) which binds and cleaves B-band LPS (O-specific antigen, OSA) of Pseudomonas aeruginosa PAO1. The crystal structure of LKA1gp49 catalytic domain consists of a beta-helix, an insertion domain and a C-terminal discoidin-like domain. The putative substrate binding and processing site is located on the face of the beta-helix whereas the C-terminal domain is likely involved in carbohydrates binding. NMR spectroscopy and mass spectrometry analyses of degraded LPS (OSA) fragments show an O5 serotype-specific polysaccharide lyase specificity. LKA1gp49 reduces virulence in an in vivo Galleria mellonella infection model and sensitizes P. aeruginosa to serum complement activity. This enzyme causes biofilm degradation and does not affect the activity of ciprofloxacin and gentamicin. This is the first comprehensive report on LPS-degrading lyase derived from a Pseudomonas phage. Biological properties reveal a potential towards its applications in antimicrobial design and as a microbiological or biotechnological tool.

Imminent Angiotensin-converting Enzyme Inhibitor from Microbial Source for Cancer Therapy

Background

Drugs targeting Angiotensin I-converting enzyme (ACE) have been used broadly in cancer chemotherapy. The recent past coupled with our results demonstrates the effective use of ACE inhibitors (ACEi) as anticancer agents, and they are potentially relevant in deriving new inhibitors.

Methods

Bacterial strains were isolated from cow milk collected in Coimbatore, Tamil Nadu, India and plated on nutrient agar medium. The identity of the strain was ascertained by 16s rRNA gene sequencing method and was submitted to the NCBI GenBank nucleotide database. Various substrates were screened for ACEi production by the fermentation with the isolated strain. ACEi was purified by sequential steps of ethanol precipitation, ion exchange column chromatography and gel filtration column chromatography. The apparent molecular mass was determined by SDS-PAGE. The anticancer property was analyzed by studying the cytotoxicity effects of ACEi using Breast cancer MCF-7 cell lines.

Results

The isolate coded as BUCTL09 was selected and identified as Micrococcus luteus. Among the seven substrates, only beef extract fermented broth showed an inhibition of 79% and was reported as the best substrate. The peptide was purified and molecular mass was determined. The IC50 value of peptide was found to be 59.5 μg/ml. The purified peptide has demonstrated to induce apoptosis of cancer cell.

Conclusions

The results of this study revealed that Peptide has been determined as an active compound that inhibited the activity of ACE. These properties indicate the possibilities of the use of purified protein as a potent anticancer agent.

Purification and characterization of lipopolysaccharides

Lipopolysaccharides are the major components on the surface of most Gram-negative bacteria, and recognized by immune cells as a pathogen-associated molecule. They can cause severe diseases like sepsis and therefore known as endotoxins. Lipopolysaccharide consists of lipid A, core oligosaccharide and O-antigen repeats. Lipid A is responsible for the major bioactivity of endotoxin. Because of their specific structure and amphipathic property, purification and analysis of lipopolysaccharides are difficult. In this chapter, we summarize the available approaches for extraction, purification and analysis of lipopolysaccharides.

Immunoglobulin allotypes and IgG subclass antibody response to Pseudomonas aeruginosa antigens in chronically infected cystic fibrosis patients

Chronic Pseudomonas aeruginosa lung infection is the leading cause of death in patients with cystic fibrosis (CF). Poor prognosis correlates with a high number of anti-pseudomonas precipitins and with high levels of IgG2 and IgG3 anti-pseudomonas antibodies. Reports of several highly significant associations between certain Gm (genetic markers of IgG on human chromosome 14) and Km (k-type light chain determinants on chromosome 2) phenotypes and immune responsiveness to various antigens suggest that allotype-linked immune response genes do exist in man. Furthermore correlation between Gm types and IgG subclass levels has been reported. A group of 143 CF patients were investigated (31 non-infected and 112 chronic infected). The IgG subclass antibodies to three different P. aeruginosa antigens (P. aeruginosa standard antigen (St-Ag), alginate and LPS) were determinated. Immunoglobulin allotypes were determined by haemagglutination inhibition. Samples were typed for G1m(1,2,3, and 17), G2m(23), G3m(5,21), and Km(1,3). Statistical analysis of our data demonstrate that IgG3 anti-pseudomonas antibody levels and Gm markers are related. IgG3 antibody levels to all investigated P. aeruginosa antigens are significantly higher in sera homozygous for Gm(3;5), somewhat lower in heterozygous sera, and significantly lower in sera homozygous for Gm(1,2,17;21). We suggest that genetic differences between the patients may explain the present differences in subclass patterns.

Detection of antibodies to Pseudomonas aeruginosa in serum and oral fluid from patients with cystic fibrosis

Cystic fibrosis (CF) patients who are chronically infected withPseudomonas aeruginosamake serum antibodies to bacterial surface LPS as well as other pseudomonas antigens. This study investigated the feasibility of using oral fluid samples for the detection of pseudomonas antibodies in CF patients and compared these results with corresponding serum antibodies. Most strains ofP. aeruginosaproduce two forms of LPS molecule, termed A-band (described as a common antigen) and B-band (O-serotype-specific antigen), apparently bound to a common core oligosaccharide moiety. A-band LPS was demonstrated in 45 out of 49 clinical isolates ofP. aeruginosaby SDS-PAGE and immunoblotting with a specific antibody. Oral fluids were collected from 17 adult CF patients, all of whom were sputum culture positive forP. aeruginosa(13 also provided serum samples), 11 primary ciliary dyskinesia (PCD) patients and 37 healthy volunteers. Antibodies to A-band LPS were detected by immunoblotting in all of the CF patients’ oral fluids but 10 of the volunteer samples gave weak reactions with immunoblotting. Six of the PCD patients gave a weak reaction with A-band antibodies and only one demonstrated antibodies to core LPS. In a quantitative ELISA, 15 of the 17 CF patients’ oral fluids were shown to contain antibodies to A-band LPS, whilst none of the volunteer samples contained antibodies to A-band LPS. All serum samples from the CF patients were positive by both methods. Thus this is a sensitive procedure for the detection of antibodies to A-band LPS ofP. aeruginosain oral fluid and serum from patients with CF.

Physicochemical properties of bacterial glycopolymers in relation to bioactivity

An overview is given on the physicochemical properties of bacterial glycopolymers, i.e., pure oligo- and polysaccharides as well as glycolipids. Data from analysis of the chemical and physicochemical properties of various sugar polymers are summarized. Furthermore, data are presented on the thorough characterization of the most important class of bacterial glycopolymers, the lipopolysaccharides (LPS). These data comprise the chemical characterization, the gel to liquid crystalline phase transition behaviour of their acyl chains, the ultrastructural studies of their morphology, and the investigation of the types of aggregate structures present above the critical micellar concentration (CMC). Furthermore, the relevance of these data with respect to an understanding of the various biological effects elicited by LPS is discussed.

Dynamics of bacterial colonisation in the respiratory tract of patients with cystic fibrosis

Mutations in the human genome may result in altered phenotypes. The cystic fibrosis (CF) patient, for instance, suffers from an aberrant composition of the epithelial lining of the gastrointestinal and respiratory tract. In this particular case, a single point mutation in the cystic fibrosis conductance regulator (CFTR) gene results in major physiological changes resulting in ecological changes that generate a niche particularly attractive to a selected set of microbial pathogens. We here present a review on the dynamics of the bacterial populations inhabiting the CF lung. Studies focusing on Staphylococcus aureus, Haemophilus influenzae and Pseudomonas aeruginosa will be summarised and discussed, whereas the technology used for microbial characterisation will be shortly highlighted. Emphasis, however, will be on those studies that assessed the genetic diversity among clinical isolates that were obtained over prolonged periods of time, enabling the distinction between persistent colonisation versus frequent re-infection by the selected pathogens. Evolutionary adaptation of pathogens to the CF lung is a common theme in many of these studies.

Genetics of O-antigen biosynthesis in Pseudomonas aeruginosa

Pathogenic bacteria produce an elaborate assortment of extracellular and cell-associated bacterial products that enable colonization and establishment of infection within a host. Lipopolysaccharide (LPS) molecules are cell surface factors that are typically known for their protective role against serum-mediated lysis and their endotoxic properties. The most heterogeneous portion of LPS is the O antigen or O polysaccharide, and it is this region which confers serum resistance to the organism. Pseudomonas aeruginosa is capable of concomitantly synthesizing two types of LPS referred to as A band and B band. The A-band LPS contains a conserved O polysaccharide region composed of D-rhamnose (homopolymer), while the B-band O-antigen (heteropolymer) structure varies among the 20 O serotypes of P. aeruginosa. The genes coding for the enzymes that direct the synthesis of these two O antigens are organized into two separate clusters situated at different chromosomal locations. In this review, we summarize the organization of these two gene clusters to discuss how A-band and B-band O antigens are synthesized and assembled by dedicated enzymes. Examples of unique proteins required for both A-band and B-band O-antigen synthesis and for the synthesis of both LPS and alginate are discussed. The recent identification of additional genes within the P. aeruginosa genome that are homologous to those in the A-band and B-band gene clusters are intriguing since some are able to influence O-antigen synthesis. These studies demonstrate that P. aeruginosa represents a unique model system, allowing studies of heteropolymeric and homopolymeric O-antigen synthesis, as well as permitting an examination of the interrelationship of the synthesis of LPS molecules and other virulence determinants.

Complex serology and immune response of mice to variant high-molecular-weight O polysaccharides isolated from Pseudomonas aeruginosa serogroup O2 strains

The O antigen of the Pseudomonas aeruginosa lipopolysaccharide is the optimal target for protective antibodies, but the unusual and complex nature of their sugar substituents has made it difficult to define the range of these structures needed in an effective vaccine. Most clinical isolates of P. aeruginosa can be classified into 10 O-antigen serogroups, but slight chemical differences among O polysaccharides within a serogroup give rise to subtype epitopes. These epitopes could impact the reactivity of O-antigen-specific antibodies, as well as the susceptibility of a target strain to protective, opsonic antibodies. To define parameters of serogroup and subtype-epitope immunogenicity, antigenicity, and surface expression on P. aeruginosa cells, we prepared high-molecular-weight O-polysaccharide vaccines from strains of P. aeruginosa serogroup O2, for which eight structurally variant O antigens expressing six defined subtype epitopes (O2a to O2f) have been identified. A complex pattern of immune responses to these antigens was observed following vaccination of mice. The high-molecular-weight O polysaccharides were generally more immunogenic at low doses (1 and 10 microg) than at a high dose (50 microg) and usually elicited antibodies that opsonized the homologous strain for phagocytic killing. Some of the individual polysaccharides elicited cross-opsonic antibodies to a variable number of strains that express all of the defined serogroup O2 subtype epitopes. Combination into one vaccine of two antigens that individually elicited cross-reactive opsonic antibodies to most members of the O2 serogroup inhibited, instead of enhanced, the production of antibodies broadly reactive with most serogroup O2 subtype strains. Thus, immune responses to P. aeruginosa O antigens may be restricted to a limited range of epitopes on structurally complex O antigens, and combining multiple related antigens into a single vaccine formulation may inhibit the production of those antibodies best able to protect against most P. aeruginosa strains within a given O-antigen serogroup.

Use of pulsed-field gel electrophoresis as an epidemiologic tool during an outbreak of Pseudomonas aeruginosa lung infections in an intensive care unit

OBJECTIVE

A retrospective study was performed to evaluate the use of DNA polymorphism analysis by pulsed-field gel electrophoresis (PFGE) in assessing the rate of exogenous contamination during an outbreak of Pseudomonas aeruginosa lung infections in an intensive care unit ICU. Another goal was to determine the risk factors, involved in the outbreak.

DESIGN

Rectal swabs and tracheal secretions were cultured from all patients upon admission and thereafter once a week throughout their stay in the ICU. Resistance patterns were determined in all P. aeruginosa isolates. We determined the serotypes, pyocin types, plasmid profiles and total DNA macrorestriction patterns for isolates. The restriction fragment length polymorphism (RFLP) of Dra I total DNA digest was studied by PFGE. A retrospective case-control study was performed to determine the risk factors for P. aeruginosa bronchopulmonary colonization.

SETTING

The study was carried out in the medical ICU of Besancon University Hospital (France).

RESULTS

The typability, stability and reproducibility of phenotypic markers were not completely satisfactory. Only the RFLP profile satisfied all the criteria for a good typing technique. In four of the 17 patients, P. aeruginosa strains with the same DNA pattern were found. Among the previously reported risk factors for hospital-acquired bronchopulmonary infections, only invasive procedures were determined by multivariate analysis to be significant in our study group. The oropharynx and the bronchial tract are the most likely endogenous sources.

CONCLUSION

PFGE-RFLP is a valuable tool for the epidemiologic study of P. aeruginosa. This typing method revealed that exogenous contamination is not always the major source of P. aeruginosa lung infections in mechanically ventilated patients in ICUs.

Identification of outer membrane proteins as target antigens of Pseudomonas aeruginosa Homma serotype M

Pseudomonas aeruginosa is routinely serotyped in Japan by using the Homma scheme. The serotypes (O serotypes) are based on the chemical structure of the O-polysaccharide portion of the lipopolysaccharide (LPS). However, the nature of the Homma serotype M antigen has remained obscure because strains classified as serotype M usually have the rough phenotype. I characterized the target antigen of serotype M. The results of Western blotting (immunoblotting) showed that commercially available typing monoclonal antibody (MAb) against serotype M specifically bound to outer membrane protein (Opr) G and that typing rabbit antiserum specific for serotype M mainly contained antibodies against Oprs F and H2. These Oprs were distributed among all P. aeruginosa strains tested, including the serotype standard, serotype M and nontypeable strains, and a series of LPS-core-defective mutants derived from strain PAC1. However, the rough mutants derived from strain PAC1 agglutinated with the anti-serotype M antibodies, whereas the smooth strains did not. LPS preparations from serotype M strains possessed few or no polysaccharide chains. These strains had higher levels of binding activity with anti-serotype M MAb, as well as with anti-lipid A MAb, which specifically bound to the cell surface of the rough-natured gram-negative bacterial strains with high activity. The anti-serotype M antiserum also contained rough-LPS-specific antibodies, but the epitope was distributed among only a few strains. The results suggested that the Oprs acted as the serotype M antigen and that LPS did not. In conclusion, the rough strains agglutinated with anti-Opr antibodies and were distinguished as serotype M from the smooth strains of other serotypes, because the antibodies were accessible to the cell surface lacking O polysaccharides. I supposed that Homma serotype M is an index of the rough nature of P. aeruginosa strains rather than one of the O serotypes.

The rfb locus from Pseudomonas aeruginosa strain PA103 promotes the expression of O antigen by both LPS-rough and LPS-smooth isolates from cystic fibrosis patients

Strains of Pseudomonas aeruginosa initially isolated from patients with cystic fibrosis (CF) often express a smooth lipopolysaccharide (LPS) containing many long O side-chain antigens, but once a chronic infection is established, strains recovered from these patients express little or no LPS O antigen. The genetic basis for this loss of O antigen expression by P. aeruginosa CF isolates is unknown. We report here that 20 CF isolates of P. aeruginosa, 13 of which are LPS-rough, were each capable of expressing serogroup O11 antigen when provided with the rfb locus from P. aeruginosa serogroup O11 strain PA103 on the recombinant plasmid pLPS2. Eight of the thirteen LPS-rough isolates co-expressed another, presumably endogenous, O antigen when they contained pLPS2. Different subcloned regions of pLPS2 complemented distinct strains to restore endogenous O antigen expression. These data suggest that the loss of O antigen expression by P. aeruginosa CF isolates results from alterations specific to the rfb region, and is not due to mutations involving other loci or ancillary LPS genes.

Correlation between specific IgG subclass antibodies to Pseudomonas aeruginosa and opsonic activity in serum from patients with cystic fibrosis

Heat-stable opsonins from sera of patients with cystic fibrosis (CF) non-CF patients with chronic Pseudomonas aeruginosa infection, healthy children, and adults were investigated for their ability to promote phagocytosis of 35S-labeled P. aeruginosa by human polymorphonuclear neutrophils. Healthy children had significantly lower levels of opsonic activity than adults. Sera from patients with CF without chronic P. aeruginosa lung infection showed significantly higher levels of opsonic activity compared to healthy children. Sera from patients with CF in the early stage of chronic infection had similar opsonic activity as non-CF patients with chronic infection. Sera from patients with CF in the late stage of chronic infection had higher opsonic activity than other infected patients, but not different from adult controls. An inverse correlation was found between levels of specific antibodies to P. aeruginosa and opsonic activity in the group of patients in a late stage of infection. An inverse correlation was also found between levels of IgG1 and IgG3 to P. aeruginosa St-Ag and opsonic activity during the late stage of infection. Infection with P. aeruginosa in CF did not induce significantly increased opsonic activity. It seems that antibodies to P. aeruginosa may have inhibitory opsonic activity.

Enhancement of lipopolysaccharide-induced tumor necrosis factor secretion by hyperimmune serum from chronic infected patients

Patients with cystic fibrosis (CF) and chronic Pseudomonas aeruginosa lung infection have a very high load of endotoxins in their lungs. However, sepsis practically never occurs in this group of patients and the presence of tumor necrosis factor (TNF)-alpha (one of the mediators of septic shock) in serum from chronically infected CF patients is contentious. The purpose of this study was to investigate the effect of hyperimmune serum from patients with CF on lipopolysaccharide (LPS, endotoxin)-induced TNF secretion from human peripheral blood mononuclear cells (PBMC). PBMC were purified from healthy donors and stimulated with a mixture of purified LPS from P. aeruginosa and serum from chronically infected CF patients or healthy controls. TNF in the cell supernatants was detected by an enzyme-linked immunosorbent assay method. CF sera showed a pronounced potentiating effect on TNF secretion from human PBMC induced by LPS from P. aeruginosa. In comparison, serum from healthy controls did not have this effect. By contrast, CF serum and serum from healthy controls showed only little potentiating effect when using LPS from Salmonella abortus equi at concentrations above 0.01 microgram/ml per 2 x 10(6) PBMC. This indicates a specific interaction between P. aeruginosa LPS and CF serum which enhances TNF secretion. The TNF responses varied depending on the sera used in the preincubation with LPS, and correlated positively to the specific IgG, IgA, and IgM anti-P. aeruginosa LPS titers of the sera. However, since TNF is hardly detectable in sera from these patients another LPS- and/or TNF-inhibitory activity may be present in these sera.

Specific IgG2 antibodies to Pseudomonas aeruginosa lipid A and lipopolysaccharide are early markers of chronic infection in patients with cystic fibrosis

The IgG subclass antibody response to the two parts of Pseudomonas aeruginosa lipopolysaccharide; endotoxic lipid A and the O-polysaccharide, were investigated in a retrospective longitudinal study involving 16 patients with cystic fibrosis and chronic P. aeruginosa lung infection. The purpose of the study was to see if any of the IgG subclasses of either specificity could be used as prognostic markers in the development and subsequent course of the lung disease. IgG2 anti-lipid A, IgG3 anti-lipid A, and IgG2 anti-polysaccharide showed a significant positive correlation with deteriorating pulmonary function already before chronic P. aeruginosa lung infection was diagnosed as well as in subsequent years. The findings suggest antigenic exposure of the patient before chronic infection is detected by routine sputum examinations, and further support our previous findings of a critical role of the IgG subclass response in modulating the course of inflammatory lung damage in these patients.

Pseudomonas aeruginosa lipopolysaccharide: evidence that the O side chains and common antigens are on the same molecule

We investigated whether Pseudomonas aeruginosa produces two distinct lipopolysaccharides (LPS) containing either serologically variable O side chains or a neutral polysaccharide common antigen, designated A bands, that reacts with monoclonal antibody (MAb) E87. Immunoprecipitation of LPS and free O side chains with O-side-chain-specific antibodies or MAb E87 resulted in coprecipitation of both polysaccharides when antibody of either specificity was employed. Chromatography of LPS and free O side chains in a disaggregating deoxycholate buffer indicated the two polysaccharide antigens cochromatograph when eluates were analyzed by sensitive and specific enzyme-linked immunosorbent assay inhibitions. The LPS from a mutant of strain PAO1 that lacks polymerized O side chains but retains the common antigen eluted in fractions containing smaller LPS molecules, indicating the necessity of polymerized O side chains for elution in early fractions containing large LPS monomers. A phosphomannomutase mutant of P. aeruginosa PAO1 makes a rough LPS lacking both O side chains and common antigen but still produces a small (< 6-kDa) common antigen component detectable in cell lysates. Introduction of the cloned pmm gene into this strain restored production of a smooth LPS expressing large MAb E87-reactive common antigen. Destruction with NaOH of O side chains on recombinant LPS molecules eluting early from the molecular sieve column resulted in a shift of the MAb E87-reactive antigen to the late-eluting fractions. These results indicate that on most P. aeruginosa LPS molecules, O side chains and neutral polysaccharide common antigens are both present.

Antibodies from chronically infected cystic fibrosis patients react with lipopolysaccharides extracted by new micromethods from all serotypes of Pseudomonas aeruginosa

Micromethods were developed to extract lipopolysaccharide (LPS, endotoxin) from single bacterial colonies of the 20 recognized Pseudomonas aeruginosa type strains. The appearance of these LPSs in polyacrylamide gel electrophoresis (PAGE) and their reactivity with serum of cystic fibrosis (CF) patients chronically infected with P. aeruginosa was studied. Silver staining of LPS after PAGE showed that 13 of the P. aeruginosa LPSs had high numbers of O-repeating units arranged in 1-4 clusters of banding. Low-molecular-weight LPS fractions were more prominent in six of the serotype strains, of which O:7 and O:14 appeared semi-rough. Corresponding immunoblots using the CF sera showed LPS patterns very similar to the silver-stained appearance, indicating an immune reaction to all P. aeruginosa LPS including that from the newly discovered O:18, O:19 and O:20. This was unexpected since only a few serotype strains (mostly O:3, O:6 and O:9) had been isolated from the patients. Absorption experiments using purified and chemically defined P. aeruginosa rough LPS and smooth LPS suggested these immune reactions were due to antibodies cross-reactive to core/lipid A as well as to lower molecular weight O-polysaccharides or "A-bands". However, in some cases O:3, O:6, and O:9 LPSs were also found to contain additional distinct O-epitopes. Immune recognition of various polyagglutinable P. aeruginosa LPSs seemed also to be caused by cross-reactive antibodies. The described microextraction methods, followed by PAGE and silver staining or immunoblotting, are easy and convenient techniques with which to study antibodies against LPS epitopes and to screen for LPS phenotypic appearance using only a few bacterial colonies from larger numbers of Gram-negative bacterial strains.

Immunoglobulin allotypes and IgG subclass antibody response to Pseudomonas aeruginosa antigens in chronically infected cystic fibrosis patients

Chronic Pseudomonas aeruginosa lung infection is the leading cause of death in patients with cystic fibrosis (CF). Poor prognosis correlates with a high number of anti-pseudomonas precipitins and with high levels of IgG2 and IgG3 anti-pseudomonas antibodies. Reports of several highly significant associations between certain Gm (genetic markers of IgG on human chromosome 14) and Km (k-type light chain determinants on chromosome 2) phenotypes and immune responsiveness to various antigens suggest that allotype-linked immune response genes do exist in man. Furthermore correlation between Gm types and IgG subclass levels has been reported. A group of 143 CF patients were investigated (31 non-infected and 112 chronic infected). The IgG subclass antibodies to three different P. aeruginosa antigens (P. aeruginosa standard antigen (St-Ag), alginate and LPS) were determined. Immunoglobulin allotypes were determined by haemagglutination inhibition. Samples were typed for G1m(1,2,3, and 17), G2m(23), G3m(5,21), and Km(1,3). Statistical analysis of our data demonstrate that IgG3 anti-pseudomonas antibody levels and Gm markers are related. IgG3 antibody levels to all investigated P. aeruginosa antigens are significantly higher in sera homozygous for Gm(3;5), somewhat lower in heterozygous sera, and significantly lower in sera homozygous for Gm(1,2,17;21). We suggest that genetic differences between the patients may explain the present differences in subclass patterns.

Immunosuppressive effects induced by the polysaccharide moiety of some bacterial lipopolysaccharides

The immunomodulatory properties of several lipopolysaccharides (LPS) derived from clinical isolates of Pseudomonas aeruginosa, Branhamella catarrhalis, and Bordetella pertussis were evaluated for their capacity to influence the magnitude of the antibody response to type III pneumococcal polysaccharide (SSS-III), which is known to be regulated by suppressor and amplifier T cells (Ts and Ta, respectively). The administration of LPS, two days after immunization resulted in a significant increase in the antibody response. Such enhancement may be due mainly to the ability of the lipid A moiety of LPS to abolish the negative effects of activated Ts, thereby enabling Ta function to be more fully expressed; however, B cell mitogenicity of the LPS molecule also may be involved. By contrast, treatment with LPS at the time of immunization with SSS-III induces significant suppression of the SSS-III-specific antibody response; such suppression is not induced by LPS or lipid A derived from Escherichia coli and Salmonella minnesota, and is independent of the capacity of LPS to activate B cells polyclonally, an activity generally attributed to the lipid A fraction of LPS. Studies conducted with the LPS of P. aeruginosa indicated that the suppression induced is T cell dependent and mediated by the polysaccharide (PS) fraction of LPS; it appears to be due-at least in part-to the capacity of PS to expand or increase the size of the precursor pool of Ts, activated in response to SSS-III. The significance of these findings to the pathogenesis of certain gram-negative infections is discussed.

Immunoglobulin G antibodies to Helicobacter pylori in patients with dyspeptic symptoms investigated by the western immunoblot technique

Helicobacter pylori is a gram-negative, curved, rod-shaped bacterium known to cause gastritis and to be an important factor in the pathogenesis of peptic ulcers. Serological testing has recently been proposed as an aid in diagnosis of H. pylori infections. In this study, we used the Western immunoblot technique to evaluate the possibility of using one or more of the antigens from H. pylori for this purpose. Thirteen major bands and about 30 minor bands could be identified by Western blotting when sera from 53 consecutive dyspeptic patients, 27 healthy children, and 25 blood donors were evaluated. Antibodies against most of the major bands were found significantly more frequently in patients with H. pylori infections than in patients without such infections. However, antibodies against a single polypeptide were not produced by all patients with H. pylori infection. Polypeptides with molecular masses of 120, 50, and between 19 and 36 kDa seem to be the most specific polypeptides for the diagnosis of H. pylori infections. This study showed only minor differences in antigenic composition between different clinical isolates of H. pylori, and serological cross-reactions with other bacteria were limited. Major serological cross-reactions were found only with Campylobacter jejuni and with bacterial lipopolysaccharide. However, one band at 60 kDa reacted with antiserum to the Legionella micdadei common antigen, which may indicate a cross-reaction with common antigen from several other bacteria. This study demonstrates that a number of bands may be useful as antigens in serological tests after isolation and purification.

Interactions of surfactant protein D with bacterial lipopolysaccharides. Surfactant protein D is an Escherichia coli-binding protein in bronchoalveolar lavage

Surfactant protein D (SP-D) is a collagenous glycoprotein that is secreted into the pulmonary airspaces by alveolar type II and nonciliated bronchiolar cells. SP-D exhibits Ca(++)-dependent carbohydrate binding in vitro and is structurally related to the collagenous C-type lectins, including serum conglutinin, serum mannose-binding proteins, and surfactant protein A. Preliminary studies showed calcium- and saccharide-dependent binding of fluorescein-conjugated or radioiodinated SP-D to a variety of microorganisms, including Gram-negative bacteria and fungi. A laboratory strain of Escherichia coli (Y1088) was chosen to further examine the mechanism(s) of binding. Binding of SP-D to Y1088 was time dependent, saturable, and inhibited by cold SP-D or competing saccharides; Scatchard analysis gave a Kd of 2 x 10(-11) M. At higher concentrations, SP-D also caused Ca(++)-dependent agglutination of Y1088 that was inhibited by alpha-glucosyl-containing saccharides, antisera to the carbohydrate-binding domain of SP-D, or Y1088 LPS. Lectin blots showed specific binding of 125I-SP-D to Y1088 LPS, as well as LPS from other several strains of enteric Gram-negative bacteria. Immunogold studies demonstrated strong and uniform surface labeling of the bacteria. Rat and human bronchoalveolar lavage (BAL) caused Ca(++)-dependent agglutination of E. coli that was dose dependent and inhibited by competing saccharides or anti-SP-D. SP-D was selectively and efficiently adsorbed from rat BAL by incubation with E. coli, and incubation of E. coli with radiolabeled rat type II cell medium revealed that SP-D is the major E. coli-binding protein secreted by freshly isolated cells in culture. We suggest that SP-D plays important roles in the lung's defense against Gram-negative bacteria.

Antibody responses to lipid A, core, and O sugars of the Pseudomonas aeruginosa lipopolysaccharide in chronically infected cystic fibrosis patients

Enzyme-linked immunosorbent assays were developed separately for the three main parts of the Pseudomonas aeruginosa lipopolysaccharide (LPS) molecule, namely, lipid A, core, and O polysaccharide. Anti-lipid A, anticore, and anti-O polysaccharide antibodies were measured in serum samples from 12 patients with cystic fibrosis (CF) in a longitudinal study covering the period before P. aeruginosa infection was established through at least 5 years of chronic infection. The serum antibody response to all parts of the P. aeruginosa LPS molecule increased during the course of chronic infection. The increase in anti-lipid A antibodies was specific for P. aeruginosa lipid A, since no increase in anti-Escherichia coli lipid A antibodies was seen. Immunoglobulin G, A, and M (IgG, IgA and IgM) antibodies were all involved in the specific systemic response to P. aeruginosa lipid A, core, and the O polysaccharides. IgG and IgA levels in particular increased during the course of infection and were significantly higher than the antibody increase seen with age in a healthy control group. The local immune response in the lungs was investigated by measuring IgG, IgA, and IgM antibodies to the separate parts of the P. aeruginosa LPS molecule in sputum samples from 18 CF patients with at least a 5-year history of chronic P. aeruginosa infection. Antibodies detected in sputum were mainly anti-lipid A and anti-O polysaccharide antibodies of the IgG and IgA isotypes. Very high IgA anti-lipid A titers were detected in sputum samples from some CF patients.

Polyacrylamide gel electrophoresis analysis of lipopolysaccharide from Pseudomonas aeruginosa growing planktonically and as biofilm

Lipopolysaccharide (LPS, endotoxin) was extracted from biofilm and planktonically grown monoagglutinable (1118) and polyagglutinable (258 and 15703) strains of Pseudomonas aeruginosa isolated from cystic fibrosis patients with chronic pulmonary infections. Analysis by polyacrylamide gel electrophoresis (PAGE) followed by immune-detection of LPS fractions showed an S-form appearance of strain 1118 and 258 with three distinct clusters of high molecular weight bands, whereas 15703 appeared semi-rough. LPS of semi-rough cells grown planktonically and as biofilm showed a very similar PAGE pattern; however, the core/lipid A R-LPS fraction was more prominent in biofilm-LPS than in planktonic-LPS extracted from the S-form bacteria (1118 and 258). The apparent change in LPS sub-unit components of the bacteria when grown as biofilm may reflect changes in the outer membrane structure that contribute to the altered physico-chemical properties of biofilm bacteria in foreign-device associated infections and chronic P. aeruginosa lung infection in cystic fibrosis patients.

Comparative immunochemistry of lipopolysaccharides from Branhamella catarrhalis strains

Lipopolysaccharides (LPS) were extracted and purified from the type strain and from a clinical isolate of Branhamella catarrhalis. Chemical analysis revealed the presence of glucose, galactose, and glucosamine in different molar proportions in the LPS from these two isolates, whereas there was no difference between the two isolates in the ratios of ketodeoxyoctonate, phosphate, and the fatty acids C12, 3-OH-C12, and 3-OH-C11 present. Heptose or 3-OH-C14 was not detectable in either preparation. LPS from both strains appeared semirough according to sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, presenting a core polysaccharide plus one repeating unit. Immunoblotting, passive hemolysis, and hemolysis inhibition assays using anti-LPS antibodies from immunized rabbits demonstrated cross-reactivity between the LPS preparations; however, antigenic dissimilarities were also found, suggesting that more than one serotype may exist. The lipid A isolated from the two LPS was serologically identical and exhibited cross-reactivity with lipid A of members of the family Enterobacteriaceae. The B. catarrhalis LPS were biologically active, causing lethality in D-galactosamine-sensitized C57/BL6 mice and inducing Limulus amoebocyte lysate gelation.

Structural characterization of the lipid A component of Pseudomonas aeruginosa wild-type and rough mutant lipopolysaccharides

The structure of the lipid A component of lipopolysaccharides isolated from two wild-type strains (Fisher 2 and 7) and one rough mutant (PAC 605) of Pseudomonas aeruginosa was investigated using chemical analysis, methylation analysis, combined gas-liquid chromatography/mass spectrometry, laser-desorption mass spectrometry and NMR spectroscopy. The lipid A backbone was found to consist of a pyranosidic beta 1,6-linked D-glucosamine disaccharide [beta-D-GlcpN-(1----6)-D-GlcpN], phosphorylated in positions 4' and 1. Position 6' of the beta-D-GlcpN-(1----6)-D-GlcpN disaccharide was identified as the attachment site of the core oligosaccharide and the hydroxyl group at C-4 was not substituted. Lipid A of the three P. aeruginosa strains expressed heterogeneity with regard to the degree of acylation: a hexaacyl as well as a pentaacyl component were structurally characterized. The hexaacyl lipid A contains two amide-bound 3-O-acylated (R)-3-hydroxydodecanoic acid groups [12:0(3-OH)] at positions 2 and 2' of the GlcN dissacharide and two ester-bound (R)-3-hydroxydecanoic acid groups [10:0(3-OH)] at positions 3 and 3'. The pentaacyl species, which represents the major lipid A component, lacks one 10:0(3-OH) residue, the hydroxyl group in position 3 of the reducing GlcN residue being free. In both hexa- and pentaacyl lipid A the 3-hydroxyl group of the two amide-linked 12:0(3-OH) residues are acylated by either dodecanoic (12:0) or (S)-2-hydroxydodecanoic acid [12:0(2-OH)], the lipid A species with two 12:0(2-OH) residues, however, being absent. The presence of only five acyl residues in the major lipid A fraction may account for the low endotoxic activity observed with P. aeruginosa lipopolysaccharide.

Microbiology of airway disease in patients with cystic fibrosis

Individuals with cystic fibrosis have abbreviated life spans primarily due to chronic airway infection. A limited number of types of organisms are responsible for these infections, with Staphylococcus aureus and Pseudomonas aeruginosa being of primary importance. In the pre-antibiotic era, greater than 90% of deaths due to infection were caused by S. aureus and death usually occurred in the first 2 years of life. With the advent of effective antistaphylococcal therapy, life spans increased and P. aeruginosa became the pathogen of primary importance. P. aeruginosa isolates recovered from patients with cystic fibrosis have a unique phenotypic characteristic referred to as "mucoid." The mucoid phenotype is due to the production of a mucoid exopolysaccharide. A mucoid exopolysaccharide is believed to play a central role in the establishment of chronic pseudomonal lung infection in these patients. A third organism, Pseudomonas cepacia, has recently been detected in the airways of older patients with cystic fibrosis and is associated with increased mortality. The virulence of P. cepacia is not understood, but the organism is extremely refractory to antimicrobial therapy. Other bacteria, including Haemophilus influenzae and members of the family Enterobacteriaceae, appear to play a secondary role in airway infection. Aspergillus fumigatus is the most important fungal agent causing allergic bronchopulmonary disease. The role of viruses has only recently been examined. At least in some patients with cystic fibrosis, respiratory syncytial virus may be important in predisposing to subsequent bacterial infections.

Structural studies of lipid A from Pseudomonas aeruginosa PAO1: occurrence of 4-amino-4-deoxyarabinose

Lipid A derived from Pseudomonas aeruginosa PAO1 contains a biphosphorylated 1-6-linked glucosamine disaccharide backbone. The reducing glucosamine has an unsubstituted glycosidically linked phosphate at C-1. The nonreducing glucosamine has an ester-bound phosphate at C-4' which is nonstoichiometrically substituted with 4-amino-4-deoxyarabinose. Induction of 4-amino-4-deoxyarabinose was dependent on cultural conditions. No pyrophosphate groups were detected. Acyloxyacyl diesters are formed by esterification of the amide-bound 3-hydroxydodecanoic acid with dodecanoic acid and 2-hydroxydodecanoic acids in an approximate molar ratio of 2:1. Dodecanoic and 3-hydroxydecanoic acids are esterified to positions C-3 and C-3' in the sugar backbone. All hydroxyl groups of the glucosamine disaccharide except C-4 and C-6' are substituted. Lipopolysaccharide chemical analyses measured glucose, rhamnose, heptose, galactosamine, alanine, phosphate, and glucosamine. The proposed lipid A structure differs from previous models. There are significant differences in acyloxyacyl diesters, and the proposed model includes an aminopentose substituent.

Modification of the silver staining technique to detect lipopolysaccharide in polyacrylamide gels

A silver staining method used routinely for detecting bacterial lipopolysaccharide (LPS) in sodium dodecyl sulfate-polyacrylamide gels (C. Tsai and E. Frasch, Anal. Biochem. 119:115-119, 1982) appeared to be inappropriate for visualizing certain LPS preparations. It did not stain S-form fractions of polyagglutinable Pseudomonas aeruginosa LPS or several partly deacylated (alkali-treated) S-form LPS after sodium dodecyl sulfate-polyacrylamide gel electrophoresis. However, these LPS preparations could be detected by anti-LPS sera after electroblotting onto nitrocellulose, thereby confirming their integrity and presence in the polyacrylamide gel. This is because LPS fractions containing a low number of fatty acids are washed out of the gel during the initial fixing step (40% ethanol-4% acetic acid, overnight). By omitting this fixing step, which was originally developed for detecting proteins, and by increasing the LPS oxidation time (from 5 to 20 min), we restored the ability to detect LPS fractions that otherwise would not be stained. These modifications did not affect the detection of other S- and R-form LPSs. Thus, differences in the number of fatty acids present in polyagglutinable P. aeruginosa LPS may result in a selective loss of fatty acid-deficient S-form LPS in these apparent R-form LPS preparations. This modified procedure provides a fast, simple, and sensitive way to analyze LPS in polyacrylamide gels despite the number of acyl groups present.

Quantitation and biological activities of native tumour necrosis factor from LPS-stimulated human monocytes

Human mononuclear cells (MNC) were stimulated in culture with LPS to produce tumour necrosis factor (TNF). The natural tumour necrosis factor (nTNF) was quantitated by ELISA and immunoblotting using rabbit antibodies to human recombinant TNF (rTNF) and the biotin-avidin-peroxidase system. Biologically active nTNF was determined by its cytotoxic activity for actinomycin-D treated mouse fibroblasts and by its lethal effect in D-galactosamine sensitized endotoxin-resistant mice. Two different LPS preparations (Salmonella abortus equi and Pseudomonas aeruginosa) induced the formation of comparable amounts of nTNF. MNC from different donors, however, showed large variations in their ability to produce nTNF. The amount of nTNF induced in response to LPS could be enhanced by priming the MNC with interferon. The amounts of nTNF determined by ELISA generally correlated well with the activity of the nTNF in the two biological assays. On a weight basis, the lethal activity of nTNF in D-galactosamine treated mice was very similar to that of human rTNF. Immunoblotting revealed a single band of nTNF with the same molecular weight (17 kD) as human rTNF. The lethality induced by nTNF was inhibited by rabbit anti-human rTNF antibodies.

Growth-dependent alterations in production of serotype-specific and common antigen lipopolysaccharides in Pseudomonas aeruginosa PAO1

Pseudomonas aeruginosa PAO1 was grown in various media and at different temperatures, and the heterogeneity of the extracted lipopolysaccharide (LPS) was characterized by polyacrylamide gel electrophoresis. The size distributions of the serotype-specific LPS and the common antigen LPS were analyzed on Western blots (immunoblots). Cells grown at high, near-growth-limiting temperatures, at low pH, in low concentrations of phosphate, or in high concentrations of NaCl, MgCl2, glycerol, or sucrose produced decreased amounts of the very long chain population of O-antigen LPS molecules. Lower temperatures and lowered glycerol, lowered sucrose, low sulfate, lower salt concentrations, and elevated pH did not significantly affect the level of this LPS population. The size and amount of common antigen LPS was either unaffected or increased slightly when the cells were grown under the above stress conditions. Cells grown under normal, nonstressed conditions were agglutinated only by serotype-specific antibodies. In contrast, cells grown under stress conditions, in which the long-O-polymer LPS was absent, were agglutinated by both serotype-specific and common antigen-specific antibodies. The results indicate that the long O polymers cover and mask the shorter common antigen. However, specific growth conditions limit the production of the long O polymer, allowing the exposure and reactivity of the common antigen on the cell surface.

Pseudomonas hyperimmune globulin passive immunotherapy for pulmonary exacerbations in cystic fibrosis

We studied the effect of an intravenously administered gamma globulin [Ps-ivIG] enriched fivefold over conventional ivIG for Pseudomonas aeruginosa lipopolysaccharide [PA LPS] antibodies on ten patients with cystic fibrosis [CF] aged 19-32 years during hospitalization for pulmonary deterioration. All were colonized with greater than or equal to 1 PA phenotype resistant to all antibiotics at the time of admission and they received 500 mg/kg Ps-ivIG intravenously as a single dose in addition to conventional treatment, including antibiotics and chest physiotherapy. No adverse effects occurred. Circulating immune complexes and complement levels remained unchanged from baseline. Serum levels of anti-PA LPS IgG, as measured by ELISA for eight PA LPS immunotypes, increased to 244 +/- 65% (mean +/- SE) of baseline levels 1 hour post-infusion (P less than 0.01), remained significantly elevated during a mean hospital stay of 17 days, and returned to near baseline by follow-up 4 weeks after hospital discharge. Plasma half-life and clearance values were similar to those of other subjects receiving conventional ivIG. Sputum PA density declined from 3.0 to 1.2 x 10(8) cfu/mL 1 week post-infusion (P approximately equal to 0.05), and returned to baseline at follow-up. Serum anti-PA opsonic activity increased after infusion (P less than 0.01), but returned to baseline by 72 hours. Clinical scores improved from admission to discharge (P less than 0.005) without decline at follow-up. Forced vital capacity [FVC] and forced expiratory volume in one second [FEV1] increased from admission to discharge (P less than 0.01 and P less than 0.05, respectively) without decline at follow-up. Using autologous historical control data, standard hospital therapy without Ps-ivIG resulted in no improvement in FVC or FEV1, and a subsequent decline in these parameters (P less than 0.05 for each) during a similar follow-up period. This occurred despite the fact that half the patients did not have antibiotic-resistant PA on the control admission. We conclude that Ps-ivIG is a safe adjunctive therapy for pulmonary exacerbations in moderately ill cystic fibrosis patients colonized with resistant PA, and may be associated with both greater and more prolonged improvement in pulmonary function than standard therapy alone.

Nonopsonic antibodies in cystic fibrosis. Pseudomonas aeruginosa lipopolysaccharide-specific immunoglobulin G antibodies from infected patient sera inhibit neutrophil oxidative responses

Antibody opsonins from cystic fibrosis (CF) patients were investigated using nonmucoid and mucoid lipopolysaccharide (LPS) immunotype 1 Pseudomonas aeruginosa as bacterial ligands and PMN phagocytes. CF sera were compared to normal sera, polyvalent PA LPS hyperimmune globulin, and isotype switch variant monoclonal antibodies (MAbs) specific for type 1 PA LPS. Sera from PA-infected CF patients (CF PA+) had elevated levels of PA LPS and alginate IgG antibodies and promoted significantly greater antibody-dependent PMN chemiluminescence responses than sera from uninfected CF patients (CF PA-) or normal human sera (NHS). After adjustment for autologous IgG PA LPS antibody content, however, CF PA+ sera had less antibody-dependent opsonic activity than sera from CF PA- patients (P less than 0.025) or NHS (P less than 0.0025), suggesting qualitative opsonic defects of IgG PA LPS antibodies in CF PA+ sera. Antigen-specific immunoprecipitation of PA LPS antibodies enhanced opsonization by 40% of CF PA+ sera while uniformly reducing that from CF PA- sera (P less than 0.01), indicating LPS-specific nonopsonic antibodies in some CF PA+ sera. Alginate antibodies were not critical opsonins in most uninfected CF patient sera. PA LPS IgG antibodies isolated by immunoaffinity chromatography from NHS, hyperimmune globulin, and CF PA- sources were opsonic and had greater activity at equal antigen-binding concentration than identical antibodies isolated from infected CF patients (P less than 0.01-0.05); the majority of isolates from CF PA+ sera did not promote PMN oxidative responses above nonopsonic baseline. A potential isotypic basis for these findings was supported by differences in PMN responses to PA opsonized with MAbs of identical specificity but differing isotypes. PA LPS-specific IgG antibodies inhibiting PMN oxidative responses in infected patient sera demonstrate antigen-specific immunomodulation of host responses by chronic bacterial parasitism in CF, which may play a role in the pathophysiology of lung disease.

Monoclonal antibody-based enzyme immunoassay for Giardia lamblia antigen in human stool

A visually readable monoclonal antibody-based antigen-capture enzyme immunoassay for the detection of Giardia lamblia antigen in human stool specimens was developed and found to be 97% (30 of 31 stool specimens) sensitive for formalinized stools and 82% (49 of 60 stool specimens) sensitive for unfixed stool specimens by visual reading. The storage of specimens in 10% Formalin resulted in increased absorbance in 20 of 26 G. lamblia-positive specimens tested as both formalinized and unfixed specimens; the increase averaged 1,336%. The assay was specific for antigens of this organism and for antigens derived from the cyst, as opposed to the trophozoite, stage. The assay could detect the antigens of five cysts per well, but could not detect antigen in in vitro-cultured trophozoites. A mouse monoclonal antibody of the immunoglobulin G1 (IgG1) subclass, which was prepared against cysts of G. lamblia, was used as the solid-phase capture antibody. The antibody was reactive with the cyst wall, as determined by immunofluorescence. Polyclonal rabbit anti-cyst IgG was used as the secondary antibody, and peroxidase-labeled goat anti-rabbit IgG was used as the tertiary antibody in the assay format. Maximal capture of antigen from stool specimens occurred by 30 min. Optimal dilution of specimens was in the range of 1:60 to 1:600. Preliminary characterization of affinity-purified antigen recognized by the monoclonal antibody showed that it is heat stable (100 degrees C, 12 min) and resistant to sodium periodate treatment and that it may exist in multiple molecular weights from 45,000 to 110,000.

Determination of the components of immune complexes made in vitro with antigens derived from Pseudomonas aeruginosa

A method for identification of the components of immune complexes would increase our understanding of the pathogenesis of chronic diseases such as Pseudomonas aeruginosa lung infection in cystic fibrosis. Capillary tube, gel diffusion and turbidimetric methods of determining immune complex formation were investigated with antigens from P. aeruginosa and the homologous rabbit antisera. Visible complexes were formed in the first two methods with flagella antigens. Purified lipopolysaccharide from P. aeruginosa would not form visible precipitates and a rapid and economical turbidimetric method was developed with 96-well microtiter plates. Larger quantities of immune complexes were formed in vitro with antigen/antibody ratios determined by the above methods. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting (Western blotting) were evaluated and found to be useful in determining the antigen and antibody components of these immune complexes.

Heterogeneity of the L-rhamnose residue in the outer core of Pseudomonas aeruginosa lipopolysaccharide, characterized by using human monoclonal antibodies

Hybridoma cell lines producing human monoclonal antibodies (MAbs) MH-4H7 and KN-2B11 [immunoglobulin M (lambda)] which bound to the outer core region of Pseudomonas aeruginosa lipopolysaccharide (LPS) were established by cell fusion of human peripheral lymphocytes with human-mouse heteromyeloma SHM D-33. Both binding specificity experiments with a series of LPS-defective mutants derived from P. aeruginosa PAC1R (P. S. N. Rowe and P. M. Meadow, Eur. J. Biochem.132:329-337, 1983) and competitive enzyme immunoassay experiments with monosaccharides demonstrated that alpha-L-rhamnose residues in the outer core of LPS might be in part an epitope. The MAbs specifically bound to clinical isolates belonging to Homma serotypes A, F, G, and K at a frequency of 70 to 86% and to serotypes H and M isolates at about 50%. They did not bind to any isolates of serotype B, E, and I tested. This evidence indicates that L-rhamnose and probably its neighboring residues in the other core of P. aeruginosa are heterogeneous in some association with the O serotype.

Antilipopolysaccharide antibodies and differential diagnosis of chronic Pseudomonas aeruginosa lung infection in cystic fibrosis

Chronic lung infection in cystic fibrosis is characteristically associated with polyagglutinable, serum-sensitive, mucoid strains of Pseudomonas aeruginosa. Enzyme-linked immunosorbent assay (ELISA) methods for standard-free quantitation of immunoglobulin G (IgG) and IgM antibodies to P. aeruginosa lipopolysaccharides (LPSs) have been developed. We now report the development of assays for quantitation of monomer and dimer total IgA and IgA anti-LPS antibodies. Use of these methods in diagnosis of early chronic P. aeruginosa lung infection was assessed. IgG and IgA anti-LPS levels increased significantly at the onset of chronic infection and continued to increase to very high levels in the later stages of infection. IgM anti-LPS levels also rose at the onset of chronic infection but did not increase further. The function of true- and false-positive rates was illustrated by using various concentrations of IgG, IgA, and IgM anti-LPS for discrimination of patients. Values that gave optimum separations were used for statistical evaluation of the diagnostic sensitivities and specificities of anti-LPS antibody concentrations. The results obtained in these assays were compared with a diagnosis, based on the number of precipitins in crossed immunoelectrophoresis, of serum samples from cystic fibrosis patients. In 64 paired serum samples taken before and immediately after the onset of chronic infection, as defined by crossed immunoelectrophoresis precipitins, the predictive values of a positive ELISA were 86% for IgG and 89% for IgA. The predictive values for a negative ELISA were 98% for IgG and 97% for IgA. Results of the IgM anti-LPS ELISA had a lower predictive value. Immunoblotting and absorption studies showed that IgG anti-LPS antibodies were directed specifically against LPS of P. aeuruginosa. ELISAs were developed to determine the specific IgG sublclasses involved. The increase in IgG anti-LPS involved all four subclasses. Highest anti-LPS titers were seen with IgG1 and IgG4, but the largest relative increases were seen with IgG2 and IgG3.

Purification, characterization, and immunological cross-reactivity of alginates produced by mucoid Pseudomonas aeruginosa from patients with cystic fibrosis

Alginates from nine mucoid Pseudomonas aeruginosa isolates from patients with cystic fibrosis were purified by repeated ethanol precipitation, nuclease digestion, anion-exchange chromatography, dialysis, and lyophilization. Uronic acid constituted 72% of the dry weight when mannuronolactone was used as the internal standard in the carbazole-borate assay for uronic acids. The average degree of acetylation was 16%, and the ratio of mannuronic acid to gluluronic acid was 4.7. No homopolymeric blocks of guluronic acid were found when analyzed by nuclear magnetic resonance spectroscopy. Contaminating proteins were denatured by heating, and during purification the content of protein relative to alginate fell from 566 to 0.9%. The content of lipopolysaccharide was 0.012%. No immunological or biological activity was attributable to the protein or lipopolysaccharide content as estimated by immunoblotting, enzyme-linked immunosorbent assay (ELISA), and a neutrophil chemotaxis assay. Rabbits were hyperimmunized with P. aeruginosa alginates and alginate from the seaweed Laminaria hyperborea, and an ELISA that detected alginate-specific antibodies was developed. Antibodies to P. aeruginosa alginate were detected by ELISA in 1:4,000 dilutions of serum from patients with cystic fibrosis with chronic P. aeruginosa lung infection. The serological cross-reactions between serum from the nine patients with cystic fibrosis and the corresponding P. aeruginosa alginates were investigated and showed considerable heterogeneity. This finding indicates that P. aeruginosa alginate from more than one P. aeruginosa strain should be used in serological tests. There was no serological cross-reactivity between P. aeruginosa and Laminaria hyperborea alginate in either rabbits or patients with cystic fibrosis.

Immunochemical and biological reactivity of human anti-lipopolysaccharide IgG obtained by screening of blood donors

An anti-lipopolysaccharide (LPS) preparation for the intravenous treatment of septic endotoxic shock was prepared by purifying immunoglobulin G (IgG) from pooled serum from Danish blood donors. The sera were selected by the use of an enzyme-linked immunosorbent assay (ELISA) to screen blood donors for high concentrations of antibodies to a mixture of LPS from 11 different Gram-negative bacteria. ELISA was also used for indirect quantification of IgG antibodies to lipid A, and to rough LPS from Escherichia coli Ra and Salmonella minnesota R60 (Ra). The concentration of human antibodies to the LPS mixture correlated with the concentration of antibodies to the E. coli and S. minnesota rough LPS and to lipid A. The specificity of sera with high concentrations of anti-LPS IgG was investigated by immunoblotting. Sera from individual donors reacted with LPS from different bacteria and recognized different sites on the LPS molecules. The range of specificities to different LPS was increased by the pooling of selected sera. The IgG fraction from the high titre donor pool neutralized biological activities of LPS such as activation of the Limulus amoebocyte lysate reaction and induction of tumour necrosis factor secretion from human monocytes.

Longitudinal study of antibody response to lipopolysaccharides during chronic Pseudomonas aeruginosa lung infection in cystic fibrosis

Antibodies to Pseudomonas aeruginosa from 10 cystic fibrosis patients with chronic P. aeruginosa lung infections were quantitatively and qualitatively analyzed. The development of specific antibodies in patient serum was evaluated in a longitudinal study (1972 to 1987). The concentrations and specificities of immunoglobulin G (IgG) and IgM antibodies to purified lipopolysaccharides (LPS) from clinical isolates of P. aeruginosa and to a variety of other gram-negative bacteria were studied by immunoblotting and enzyme-linked immunosorbent assay techniques. Results were compared with the number of immunoprecipitates to P. aeruginosa whole-cell extracts detected by crossed immunoelectrophoresis. IgG, but not IgM, anti-Pseudomonas LPS concentrations increased significantly at the onset of chronic infection and continued to increase during the course of the infection. There was a good positive correlation between the concentration of IgG anti-Pseudomonas LPS antibodies and the number of crossed-immunoelectrophoresis precipitins. The increases in IgG anti-LPS antibody concentrations were much higher to Pseudomonas LPS than to other LPSs. Binding studies demonstrated an increase in binding of IgG anti-Pseudomonas LPS during infection, whereas the binding of other anti-LPS antibodies decreased. Immunoblotting studies confirmed that antibodies reacted strongly with Pseudomonas LPS and weakly with Escherichia coli core-lipid A. The specificity of the reaction with Pseudomonas LPS increased with the duration of infection. It is concluded that anti-LPS response in cystic fibrosis patients during chronic P. aeruginosa infection demonstrates a marked increase in IgG anti-Pseudomonas LPS antibody concentration, specificity, and affinity. The anti-LPS enzyme-linked immunosorbent assay is proposed as a routine test to diagnose and to follow the course of chronic P. aeruginosa lung infection in patients with cystic fibrosis.