Monoclonal antibodies specific for Escherichia coli J5 lipopolysaccharide: cross-reaction with other gram-negative bacterial species

Prevention of lethal endotoxemia in actinomycin D-sensitized mice by incubation of Salmonella minnesota R595 lipopolysaccharide with monoclonal antibodies to R595

Murine monoclonal antibodies reacting with lipopolysaccharide (LPS) of Salmonella minnesota strain R595 (Re chemotype) were prepared, and tested for their ability to protect actinomycin D-sensitized mice against lethal endotoxemia. Protection was found with some antibodies up to a 90-fold increase in LD50, whereas others exhibited no protection. The various protective antibodies did not all bind to the same epitope. The same applied for non-protective clones. Protective and non-protective clones could not be discriminated by ELISA. One protective monoclonal antibody (clone 20) was specific for ketodeoxyoctonate, a structural element common to various LPS. These findings show that the involvement of lipid A in the binding site of monoclonal antibodies is no prerequisite for protection.

Elastase regulates the synthesis of its inhibitor, alpha 1-proteinase inhibitor, and exaggerates the defect in homozygous PiZZ alpha 1 PI deficiency

The net balance of neutrophil elastase, an enzyme that degrades many components of the extracellular matrix, and its inhibitor, alpha-1-proteinase inhibitor (alpha 1 PI), is thought to be a critical determinant in the development of destructive lung disease, especially in individuals with homozygous alpha 1 PI deficiency. Synthesis and secretion of alpha 1 PI has been recently demonstrated in cells of mononuclear phagocyte lineage, including peripheral blood monocytes and tissue macrophages. In this study we show that alpha 1 PI gene expression in human monocytes and bronchoalveolar macrophages is affected by a novel mechanism, whereby elastase directly regulates the synthesis of its inhibitor. In nanomolar concentrations, neutrophil or pancreatic elastase mediates a dose- and time-dependent increase in steady state levels of alpha 1 PI mRNA and in the rate of synthesis of alpha 1 PI in human monocytes and bronchoalveolar macrophages. Antisera to neutrophil elastase or pretreatment of elastase with the serine proteinase inhibitor diisopropylfluorophosphate abrogates the effect of elastase on alpha 1 PI expression. Elastase also stimulates the synthesis of alpha 1 PI in monocytes from homozygous PiZZ alpha 1 PI-deficient individuals, but has no effect on the rate of secretion; hence, the enzyme mediates an effect on alpha 1 PI that increases the intracellular accumulation of inhibitor and exaggerates the intrinsic defect in secretion of alpha 1 PI that characterizes the homozygous PiZZ alpha 1 PI deficiency.

Monoclonal antibodies to salmonella lipopolysaccharide: functional analysis of anti-lipid A antibodies

We have produced monoclonal antibodies (MoAb) to the Rb core and lipid A regions of Salmonella lipopolysaccharide (LPS) and have assessed their ability to inhibit LPS-mediated mitogenic responses in vitro, and to protect against LPS toxicity and lethal Salmonella infection in vivo. Monoclonal antibodies RC-8 and RC-16 were specific for LPS Rb core determinants, and MoAb LA-1, LA-2, LA-3, LA-4 and LA-5 were specific for lipid A. Anti-lipid A MoAb LA-2, LA-3 and LA-5 were found to abrogate mitogenic responses of C3H/HeN spleen cells to smooth S. typhimurium LPS (S LPS) and to rough S. minnesota R595 LPS (Re LPS). Monoclonal antibody LA-5 was effective in extending the median length of survival of C3H/HeN mice challenged with a lethal dose of either S LPS or Re LPS. Antibody LA-2 could extend the median length of survival of C3H/HeJ mice challenged with Re LPS but not with S LPS, and failed to extend significantly the length of survival of S LPS-challenged C3H/HeN and DBA/2 mice. Neither 20 micrograms of anti-Rb core or anti-lipid A MoAb nor 200 micrograms of anti-lipid A MoAb were able to protect C3H/HeN or BALB/c mice, respectively, against lethal infection with S. typhimurium SR-11. These results suggest that the importance of anti-lipid A antibodies in host defence may lie more in their ability to neutralize pathological effects of LPS, than in their ability to protect against bacterial infection.

Thin-layer chromatography of endotoxins, their derivatives and contaminants

Thin-layer chromatographic (TLC) separation techniques were used to analyze the heterogeneity of various preparations which included smooth and rough endotoxins (ET), Lipid A precipitates and synthetic Lipid A samples and a novel cytotoxic bacterial lipid. Furthermore, carbohydrate-rich split products (PS) of ET were also separated on commercial silica-coated plates. Satisfactory results were obtained by two-dimensional TLC or by the combination of chromatography followed by high-voltage electrophoresis in the separation of PS of ET cleaved by mild acetic hydrolysis. Several spray reagents were found which were eminently suitable to detect carbohydrate containing compounds. Less specific but generally useful spray reagents were also developed which gave strong color reactions with lipids, proteinaceous and carbohydrate containing split products of the ET preparations. Improved chromatographic resolution has also revealed substantial heterogeneity in both rough and smooth ET samples. Three biological activities of the separated components could be determined. These were antigenicity detected by reactivity with monoclonal antibodies on the TLC plates, endotoxicity, determined by the Limulus amoebocyte lysate (LAL) test and direct cytotoxicity of P815 cells in vitro. Considerable amounts of non-endotoxic and non-antigenic contaminants could be detected in all preparations tested. Significant amounts of free Lipid A were also found in smooth ETs. Thus a new level of complexity is recognized by TLC within these preparations.

Production of monoclonal antibodies against surface antigenic determinants of Klebsiella pneumoniae

The production of four murine monoclonal antibodies (Kp26, Kp53, Kp62 and Kp71) to Klebsiella pneumoniae surface antigen(s) is described. The binding of all four monoclonal antibodies to K. pneumoniae was inhibited by F(ab')2 fragments of normal human serum IgG, suggesting that the antigenic determinants of K. pneumoniae detected by the four monoclonal antibodies may be similar to those recognized by human serum IgG. The antigen identified by Kp62 was purified from a deoxycholate-solubilized bacterial fraction using immunoaffinity chromatography. The molecular weight of the antigen was determined by sodium dodecyl sulphate polyacrylamide gel electrophoresis to be 50,000-70,000.

Therapy of suspected septicemia in neonatal foals using plasma-containing antibodies to core lipopolysaccharide (LPS)

Equine antiserum to core lipopolysaccharide (LPS) was evaluated in a double-blind prospective study for therapeutic benefit in suspected septicemia in neonatal foals. Forty foals younger than 7 days of age were included in the study by satisfaction of clinical and laboratory criteria, suggestive of gram-negative septicemia. Twenty-two foals were treated with core LPS antiserum (plasma produced from horses which were hyperimmunized with rough gram-negative mutant bacterin) and 18 foals received "nonimmune" plasma (from horses prior to immunization against core LPS). All foals received antimicrobials, fluids, and other supportive care measures, depending on clinical signs and according to accepted current practice. The clinical and laboratory data of each foal were monitored and recorded daily for 14 days after plasma treatment or until death. The overall survival rate of these 40 foals with septicemia was 52.5%. The most prevalent diagnoses in addition to septicemia were enteritis and pneumonia. Of 30 positive bacterial cultures, 93% were due to gram-negative organisms. There was no statistically significant increase in survival rate in the 22 foals given core LPS antiserum (P greater than 0.05).

Production and specificity of monoclonal antibodies and polyclonal antibodies to Escherichia coli

Monoclonal antibodies were produced to whole cells of heat-treated Escherichia coli. Balb/c mice were immunized with a pool of five strains of heat-treated E. coli, and the resulting hybridomas were screened by indirect immunoassay. E. coli strains other than those used for immunization were used for screening to detect hybridomas producing antibody that reacted with a large number of E. coli strains. Of 864 hybridomas, 32 reacted strongly with either two or all three of the strains used for screening; 15 were successfully cloned. Antibody from hybridoma 6H2 reacted with 35 of 68 (51%) E. coli; of 13 non-E. coli tested, only Enterobacter agglomerans was weakly positive. Hybridoma 9B12 antibody reacted with all six E. coli tested. Hybridoma 9B12, however, stopped producing antibody. Five hybridomas produced antibody which reacted with a majority of the bacteria tested whereas antibodies from two other hybridomas reacted with several E. coli and non-E. coli. Polyclonal antibodies produced to two strains of E. coli varied in the numbers of E. coli with which they reacted; both antisera cross-reacted with several non-E. coli.

Lipopolysaccharide modulates the expression of alpha 1 proteinase inhibitor and other serine proteinase inhibitors in human monocytes and macrophages

alpha 1 Proteinase inhibitor (PI) is the principle inhibitor of neutrophil elastase, an enzyme that degrades many components of the extracellular matrix. Expression and regulation of alpha 1 PI, therefore, affects the delicate balance of elastase and antielastase, which is critical to turnover of connective tissue during homeostasis, tissue injury, and repair. In this study we show that expression of alpha 1 PI in human monocytes and macrophages is regulated during activation by LPS. LPS mediates a concentration- and time-dependent increase in the rate of synthesis of alpha 1 PI in mononuclear phagocytes. There is a 4.5-8.7-fold increase in functionally active inhibitor delivered to the cell culture fluid of monocytes. The effect of LPS is specific in that it is neutralized by an mAb to the lipid A moiety. The increase in expression of alpha 1 PI mediated by LPS occurs in the context of other specific changes in the expression of serine proteinase inhibitor genes in mononuclear phagocytes. There is an increase in the rate of synthesis of C1 inhibitor and a decrease in synthesis of alpha 2 macroglobulin. Regulation of alpha 1 PI by LPS is distinctive in that it is largely determined by a change in the efficiency of translation of alpha 1 PI mRNA. LPS has no effect on the rate of posttranslational processing and/or secretion of alpha 1 PI and, therein, causes greater intracellular accumulation of alpha 1 PI in mononuclear phagocytes from individuals with homozygous PiZZ alpha 1 PI deficiency.

Lipopolysaccharide tightly bound to porin monomers and trimers from Escherichia coli K-12

Lipopolysaccharide (LPS) bound to isolated porin was detected on polyacrylamide gels by using a carbohydrate-specific silver stain and on Western blots by using anti-lipid A monoclonal antibodies. Porin was isolated from Escherichia coli JF733 (Ra chemotype) and D21f2 (Re chemotype). Isolated porin was separated from loosely associated LPS by polyacrylamide gel electrophoresis (PAGE) in sodium dodecyl sulfate (SDS). Unheated porin traveled on gels as aggregates, presumably trimers, with an apparent molecular weight of 78,000 to 83,000. After heating to 100 degrees C for 2 min in SDS, the porin traveled as a monomer with a molecular weight of 36,000. The unheated, high-molecular-weight trimer band reacted in the gel with the carbohydrate-specific silver stain, while the heated monomer band showed no staining. In contrast, lipid A-specific monoclonal antibodies showed reactivity on Western blots to the 36,000-molecular-weight band but not to the trimer. Finally, both monomer and trimer bands were isolated from gels and rerun by SDS-PAGE. LPS was released from the trimer preparation when the sample was heated, but the monomer band that was formed by heating the trimer isolate still reacted with anti-lipid A antibodies. Quantitative Limulus amebocyte lysate analysis revealed an approximately equal molar ratio of LPS to protein in the electroeluted porin monomer. Thus, some but not all of the LPS could be released from trimer complexes by boiling in SDS. The isolated monomer did not release more LPS on boiling in SDS a second time but still had LPS tightly bound, as detected by lipid A-specific monoclonal antibodies.

A direct enzyme-linked immunosorbent assay (ELISA) for antibodies to enterobacterial Re core glycolipid and lipid A. Results in healthy subjects and in patients infected by gram-negative bacteria

We have developed an ELISA for IgM and IgG antibodies to the core glycolipid (CGL) of the Re mutant Salmonella minnesota R 595, and to lipid A. Anti-CGL antibodies have been detected in sera from 37% of healthy blood donors, whereas anti-lipid A activities were found in 13% of individuals only. The anti-CGL and anti-lipid A activities were examined in patients in a surgical intensive care unit, selected on the basis of a definite risk of infectious complications due to Gram-negative bacteria. Of the patients who developed such infections, the rate of favourable outcome was significantly higher in patients with either stable positive or increasing anti-CGL activities than in patients found to be negative. Our results provide clear evidence that anti-CGL antibodies contribute to host defence against various Gram-negative bacteria.

Human monoclonal antibodies that recognize conserved epitopes in the core-lipid A region of lipopolysaccharides

Epstein-Barr virus (EBV)-transformed human B lymphocytes were fused with a murine-human heteromyeloma to produce stable hybrid cell lines that secreted human monoclonal antibodies (mAbs) of the IgM class that recognized conserved epitopes in the core-lipid A region of lipopolysaccharides (LPS). Three of the mAbs reacted with epitopes on the lipid A moiety, while a fourth recognized a determinant in the core oligosaccharide. The lipid A-specific mAbs cross-reacted with heterologous rough LPS and with lipid As released by acid hydrolysis of different intact (smooth) LPS. Carbohydrate groups in the O-side chain and core oligosaccharide of isolated, smooth LPS restricted antibody access to antigenic sites on lipid A. Yet, one lipid A-reactive mAb recognized its epitope on the surfaces of a variety of intact bacteria. These findings confirm the presence of highly conserved epitopes in the core-lipid A complex and prove the existence of human B cell clones with the potential for secreting high avidity IgM antibodies that react with these widely shared determinants. Such human mAbs might provide protective activity against disease caused by diverse gram-negative bacteria.

Conservation and diversity of Campylobacter pyloridis major antigens

Infection with Campylobacter pyloridis has been strongly associated with gastritis in humans although its etiologic significance is currently undefined. We examined the structure and antigenicity of whole-cell, outer-membrane, acid-extractable surface protein, and proteinase K-treated whole cell lysate preparations from eight C. pyloridis strains by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting with homologous and heterologous immune rabbit serum. Whole-cell and outer-membrane profiles observed in all strains of C. pyloridis were nearly identical; none were similar to those of C. jejuni and C. fetus. Major whole-cell bands migrated at 26,000, 29,000, 56,000, and 62,000 molecular weights. The acid-extracted protein profiles of all C. pyloridis strains also were similar to one another and showed similarities with acid-extracted proteins from C. jejuni, with major bands migrating at 29,000, 48,000 to 53,000, and 62,000. All proteinase K-treated lysates showed different lipopolysaccharide (LPS) profiles, ranging from rough to smooth with multiple repeating side chains. Immunoblots of whole-cell and proteinase K-treated preparations of the C. pyloridis strains showed that there was antigenic cross-reactivity of proteins migrating at 62,000 and 56,000, but not in other regions, and cross-reactivity between LPS core regions but not side chains. These results suggest that C. pyloridis has both protein and core LPS group antigens and strain-specific protein and LPS side chain antigens.

Isolation and characterization of murine monoclonal antibodies specific for gram-negative bacterial lipopolysaccharide: association of cross-genus reactivity with lipid A specificity

Somatic cell hybrids secreting monoclonal antibodies against the core-glycolipid portion of enterobacterial endotoxin were derived from mice immunized with Escherichia coli J5 or Salmonella minnesota R595 heat-killed organisms or lipopolysaccharide (LPS). Eight antibodies were selected for their ability to cross-react with several members of a panel of gram-negative bacterial antigens in a radioimmunoassay. This panel represented five genera and two families of organisms: E. coli O111:B4, E. coli O55:B5, Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella minnesota, and Serratia marcescens. The binding sites for six of the antibodies were unequivocally localized within the lipid A moiety of the endotoxin molecule by using the radioimmunoassay on LPS and free lipid A. The anti-lipid A antibodies were further characterized for their ability to interact with LPS variants by using a sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunostaining procedure. The monoclonal antibodies bound almost exclusively to the low-molecular-weight species of LPS on the polyacrylamide gel. These components corresponded to LPS isolated from rough strains of organisms (strains which lack O-specific carbohydrate). These results suggested that the cross-reactive component of antisera raised against rough mutants of gram-negative bacteria contain antibodies of lipid A specificity. Moreover, the determinant within the lipid A moiety of LPS may have been accessible to the monoclonal antibodies only in those endotoxin molecules on the outer membrane surface which lack the O-specific carbohydrate.

Vaccines and antibody immunotherapy in surgical patients

Immunoprophylaxis of infectious complications in surgical patients is currently practiced and is efficacious for disease caused by Clostridium tetani, rabies virus, Streptococcus pneumoniae, and hepatitis B virus. Evidence exists that immunoprophylaxis and treatment of herpes viruses as well as gram-negative pathogens is possible, although extensive clinical testing will be required to establish immunotherapy as a effective clinical treatment modality for the control of disease caused by these agents. Advances in our understanding of the host immune response and the ways in which it may be stimulated or supplemented should provide the means to further reduce the morbidity and mortality caused by a variety of pathogenic microbial agents.

Antibody immunotherapy of gram-negative bacterial sepsis

Gram-negative bacterial sepsis continues to represent a significant cause of morbidity and mortality in hospitalized patients. Currently available medical therapy (antimicrobial agents, hemodynamic monitoring, aggressive fluid resuscitation, and nutritional support) for this disease process has reduced but not eliminated the severe consequences that may ensue. Recent investigations have demonstrated the ability of antibody directed against gram-negative bacterial lipopolysaccharide (LPS or endotoxin) to afford protection during experimental gram-negative bacillary sepsis. The core LPS-lipid A portion of endotoxin represents a determinant shared by many common gram-negative microorganisms that is luxuriantly expressed on the cell surface of rough mutants of Escherichia coli and Salmonella minnesota. These organisms or the outer membrane LPS isolated from them thus represent suitable immunogens for the development of cross-protective antibody preparations. Large quantities of highly cross-reactive antibody may potentially be obtained from several sources: murine or human monoclonal antibodies, immunization of large animals or humans with subsequent plasmapharesis and antibody isolation, affinity purification of large amounts of normal antibody, and pooling of prescreened lots of normal animal or human antibody that react to a particular bacterial antigen.

Cross-reactive antibody in immunity to colisepticemia in calves

Cattle were immunized with a uridine diphosphate galactose epimerase deficient mutant of Escherichia coli to prepare antiserum cross-reactive with different serotypes of E. coli. Hypogammaglobulinemic calves were given bovine anti-J5 serum before oral challenge with virulent E. coli derived from a septicemic calf. Passively immunized calves had delayed and decreased bacteremia compared with calves given saline before challenge. Calves given antiserum also lived longer than control calves. A second experiment using ampicillin and antibody to treat colisepticemia also showed increased survival in anti-serum-treated calves. Decreased bacteremia was probably not due to the killing of the challenge strain by antibody and complement, as the strain was serum-resistant. However, anti-J5 serum did increase phagocytosis of the challenge strain of E. coli (JL9) by bovine neutrophils. Thus, partial protection by antiserum was probably due to increased clearance of bacteria as well as neutralization of endotoxin.

Monoclonal antibodies reacting selectively with core and O-polysaccharide of Yersinia enterocolitica O:3 lipopolysaccharide

In order to obtain specific tools for studying the alterations of the immunochemical structure of Yersinia enterocolitica lipopolysaccharide in various conditions, we have produced monoclonal antibodies reacting with core and O-polysaccharide chains of Yersinia enterocolitica O:3 LPS. Immunizations were made with whole bacterial cells and outer membrane preparation, respectively. Monoclonal antibody 2B5 reacted in enzyme immunoassay with purified core-lipid A complex, and its binding was not inhibited by Polymyxin B, suggesting that the target determinant is in the outer core. 2B5 recognized 100% of all tested Y. enterocolitica O:3 strains (n = 152) and reacted to some extent also with many other gram-negative bacteria. In immunoblotting with 2B5, a band corresponding to core-lipid A complex was visualized both with Y. enterocolitica, Brucella abortus and Haemophilus influenzae. In immunofluorescence assay, the only positive reaction was seen with Y. enterocolitica. Monoclonal antibody A6 reacted in enzyme immunoassay with purified O-polysaccharide chains, recognized 100% of tested Y. enterocolitica O:3 strains, and showed no cross-reactions with other bacteria. A typical ladder pattern was not seen in the immunoblotting analysis with A6. This suggests that the O-chain of Y. enterocolitica O:3 may be different from those in other gram-negative bacteria. These two antibodies will make it possible to study the structural variations of Yersinia enterocolitica LPS more precisely than described before, because of their fine specificity against important immunogenic components of LPS. They will also be useful in serology measuring the immune response against the target determinants of these antibodies.

Use of synthetic antigens to determine the epitope specificities of monoclonal antibodies against the 3-deoxy-D-manno-octulosonate region of bacterial lipopolysaccharide

Mouse monoclonal antibodies were raised against heat-killed bacteria of the Re mutant R595 of Salmonella minnesota and characterized by the passive hemolysis and passive hemolysis inhibition tests and by double immunodiffusion experiments using lipopolysaccharide (LPS) from different rough mutants of S. minnesota and synthetic antigens. The latter were copolymerization products of acrylamide with the alpha- and beta-allylglycosides of 3-deoxy-D-manno-octulosonic acid (KDO) and the alpha-2,4-linked KDO disaccharide [poly-alpha-KDO, poly-beta-KDO, and poly-(alpha-KDO)2, respectively], and sodium (3-deoxy-D-manno-octulopyranosyl)onate-(2----6)-(2-deoxy-2-[ (R)-3- hydroxytetradecanoylamino]- beta-D-glucopyranosyl)-(1----6)-(2-deoxy-2-[(R)-3-hydroxytetradecanoy lam ino]-D-glucose) [alpha-KDO-(GlcNhm)2], representing a part structure of Re LPS. One antibody (clone 20, immunoglobulin M) was found to recognize a terminal alpha-linked KDO residue, since it reacted in the passive hemolysis assay with alpha-KDO-(GlcNhm)2 and all LPS tested, it was inhibited by all synthetic antigens containing alpha-linked KDO residues, and it gave a reaction of identity with poly-alpha-KDO and poly-(alpha-KDO)2 in double immunodiffusion experiments. A second antibody (clone 25, immunoglobulin G3) was identified as specific for an alpha-2,4-linked KDO disaccharide, since it reacted in immunodiffusion exclusively with synthetic poly-(alpha-KDO)2 and not with the monosaccharide derivatives in either anomeric configuration, and it was inhibited only with poly-(alpha-KDO)2 and with LPS from S. minnesota R595 (Re) and R345 (Rb2). The reaction of this antibody with R345 LPS is attributed to the quantitative substitution with KDO disaccharide present as a side chain, which is not present in stoichiometric amounts in the other LPS.

Immune responses to the lipopolysaccharides and capsular polysaccharides of Haemophilus pleuropneumoniae in convalescent and immunized pigs

The immunologic responses to a smooth-type lipopolysaccharide (LPS) (HpS-LPS), a rough-type LPS (HpR-LPS), and a capsular-enriched polysaccharide preparation (HpC-PS) purified from Haemophilus pleuropneumoniae were determined in pigs immunized with a commercial H. pleuropneumoniae cellular vaccine, in pigs experimentally infected with H. pleuropneumoniae, in control pigs, and in immunized rabbits. The ability of the preparations to induce lymphocyte blastogenesis and B-cell activation was determined in the pigs and compared with the responses induced by the LPS of Escherichia coli O111:B4 and the LPS of Salmonella minnesota Re595. All the LPS preparations acted to induce proliferation of peripheral blood lymphocytes (PBL) from all pigs. The blastogenic response of PBL from H. pleuropneumoniae-infected pigs to HpS-LPS and HpR-LPS was significantly (P less than 0.05) greater than that of PBL from immunized and control pigs. HpC-PS did not induce a blastogenic response in the PBL of control pigs but did in PBL from H. pleuropneumoniae-infected pigs and to a greater degree in immunized pigs. An increase in the response of PBL to the S. minnesota LPS occurred only in the H. pleuropneumoniae-infected pigs. Significantly more (P less than 0.05) immunoglobulin-secreting cells (ISC) were induced in a reverse hemolytic plaque assay by stimulation with HpS-LPS and HpC-PS of PBL isolated from pigs infected with H. pleuropneumoniae than of PBL from immunized pigs. Increasing the number of T cells increased the number of ISC induced by HpS-LPS in control and immunized pigs, but not in convalescent pigs. The presence of macrophages reduced activation of ISC by HpS-LPS in control pigs and to a lesser degree in immunized pigs, whereas in H. pleuropneumoniae-infected pigs macrophages enhanced the induction of ISC by HpS-LPS. In immunized pigs, macrophages acted to inhibit the ability of HpC-PS to induce ISC. Serologic studies indicate that HpC-PS contains strain- and serotype-specific antigens; that HpS-LPS has both serotype-specific and cross-reacting species-specific antigens; and that HpR-LPS does not contain detectable serotype-specific antigens but does have both non species- and species-specific antigens. These studies show that the serotype-specific protection provided by immunization of pigs with an H. pleuropneumoniae cellular vaccine is principally the result of immunity to capsular antigens and that a weak cellular immune response occurs as compared with that induced by infection with H. pleuropneumoniae.(ABSTRACT TRUNCATED AT 400 WORDS)

Mechanisms involved in protection provided by immunization against core lipopolysaccharides of Escherichia coli J5 from lethal Haemophilus pleuropneumoniae infections in swine

In an investigation of the potential protective effects of immunity against common lipopolysaccharide core antigens of gram-negative bacteria during a severe gram-negative infection in the natural host, we induced Haemophilus pleuropneumoniae infections in weanling pigs immunized with a vaccine of an Rc mutant of Escherichia coli (strain J5). To help define the mechanism involved in J5-mediated protection, we compared the clinical, hematologic, bacteriologic, and serologic responses following an H. pleuropneumoniae infection in J5-immunized pigs with those following an H. pleuropneumoniae infection in nonimmunized control animals. As a result of an intranasal inoculation, all of the control animals and the J5-immunized animals were infected with H. pleuropneumoniae. However, while 80% (4 of 5) of the nonimmunized pigs died within 24 h as a result of the infection, no deaths occurred in the J5-immunized animals. In the immunized group, J5 titers dropped during the acute stages of the infection and rebounded to well above the prechallenge levels during convalescence. The J5 titer also increased in the single surviving control animal. These findings suggest that antibodies against common subsurface components of gram-negative bacterial cell walls correlate with protection from an otherwise lethal challenge of H. pleuropneumoniae but do not prevent infection. Important growth-phase-dependent antigenic changes have been recognized to occur during the growth of H. pleuropneumoniae in cultures (R. Nielson, Nord. Veterinaermed. 28:337-348, 1976). In a study of these changes and during an inquiry into the mechanism of J5 antibody-mediated protection, measured quantities of H. pleuropneumoniae were removed from a broth culture at hourly intervals and used to absorb hyperimmune equine J5 antiserum. Significantly greater amounts of J5-specific antibodies were absorbed during the log phase of bacterial growth than during the early or late phase. The availability of epitopes recognized by J5 antibodies appears to be closely related to the rate of bacterial multiplication. The results of these experiments suggest a mechanism of protection provided by increased immunity to E. coli J5 during gram-negative infections.

Characterization of murine monoclonal antibodies to Escherichia coli J5

Twenty-eight independently derived monoclonal antibodies (MAb) directed against Escherichia coli J5 endotoxin were produced and characterized. Each MAb exhibited a specific titer by both radioimmunoassay and passive hemagglutination assay. Most of the MAb were of the immunoglobulin G isotype; however, several immunoglobulin M antibodies and one immunoglobulin A antibody were produced. When characterized for their capacity to cross-react with purified endotoxin preparations from several gram-negative bacteria, 22 MAb exhibited no cross-reactivity; 6 demonstrated a limited capacity to cross-react with other endotoxin preparations. When characterized for their capacity to react with the intact organism instead of the purified endotoxin the pattern of cross-reactivity was quite different. Most of the MAb were able to react with Salmonella minnesota Re595. Eighteen were able to react with E. coli O111:B4 (the parent strain of E. coli J5), 13 MAb reacted weakly with Pseudomonas aeruginosa, and 3 reacted weakly with Klebsiella pneumonia. The data imply that MAb generated against E. coli J5 endotoxin demonstrate greater cross-reactivity when assayed against the whole bacterium than when assayed against the corresponding purified endotoxin. We were unable to demonstrate that any of the 28 MAb could passively protect mice against lethal endotoxin challenge.

Lipopolysaccharide structures in Enterobacteriaceae, Pseudomonas aeruginosa, and Vibrio cholerae are immunologically related to Campylobacter spp

To determine whether lipopolysaccharide (LPS) structures of Campylobacter species are immunologically related to those of 11 other gram-negative organisms, we immunoblotted from polyacrylamide gels the LPS of these strains with immune rabbit serum raised against six Campylobacter jejuni strains and two Campylobacter fetus strains. The LPS studied were from Salmonella minnesota wild type and Ra to Re mutants, Salmonella typhi, Escherichia coli, Yersinia enterocolitica, Vibrio cholerae, and Pseudomonas aeruginosa. None of the 11 LPS preparations was recognized by the eight antisera, but antisera to each of the Campylobacter strains recognized core determinants of some LPS preparations. Antiserum directed against the most serum-sensitive C. jejuni strain, 79-193, was the only antiserum sample that recognized core regions of the rough Salmonella mutants. In converse experiments, when LPS preparations from five Campylobacter strains were blotted with antiserum to Salmonella lipid A, recognition of core structures of each was shown; data from an enzyme-linked immunosorbent assay confirmed this result. In contrast, antiserum to Salmonella typhimurium Re LPS showed no reactivity. We conclude that LPS of Campylobacter strains share lipid A antigenic determinants with the core region of LPS of several other gram-negative organisms.

Current and Future Applications of Monoclonal Antibodies against Bacteria in Veterinary Medicine

This chapter discusses the current and future applications of monoclonal antibodies against bacteria in veterinary medicine. It discusses the existing applications of monoclonal antibodies, including the use of pilus-specific monoclonal antibodies for passive immunization of calves and piglets against enteropathogenic E. coli (EPEC) infections as well as the development of rapid diagnostic test kits for field diagnosis of EPEC infections. The potential applications of monoclonal antibodies for passive immunization against a variety of veterinary pathogens are passive immunization against Moraxella bovis (pinkeye), Bacteroides nodosus (foot rot), EPEC enterotoxin (enteric colibacillosis), Pasteurella haemolytica (pneumonic pasteurellosis), and Streptococcus equi (strangles). Three main areas of application for monoclonal antibodies against bacterial antigens in veterinary medicine are passive immunization, improved immunodiagnostics, and immunotherapy. Monoclonal antibodies, because of their specificity, unlimited availability, and high titer, represent excellent passive immunizing agents. However, their potential usefulness in preventing infection must be evaluated on a case-by-case basis.

Detection of antibodies against lipopolysaccharides of Escherichia coli and Salmonella R and S strains by immunoblotting

Antisera raised against several smooth and rough strains of Escherichia coli and Salmonella typhimurium were tested against lipopolysaccharides (LPS) of homologous and heterologous strains. The LPS were separated by sodium dodecyl sulfate-gel electrophoresis, transferred to nitrocellulose paper, and overlaid with antisera. The results showed that antisera raised against smooth strains reacted with high- as well as low-molecular-weight bands of their corresponding LPS and showed very few cross-reactions. Anti-E. coli J5 antiserum cross-reacted with few strains in the core region. But, anti-S. typhimurium Ra antiserum cross-reacted with many more strains. When these sera were absorbed with either the homologous- or a heterologous-positive strain, reactions were abolished. It appears that reactions of anti-E. coli J5 antiserum and anti-S. typhimurium Ra antiserum with homologous and heterologous strains were not due to the same antibody. This immunoblotting technique proved to be a useful method to distinguish different antibodies in antiserum raised against LPS of gram-negative bacteria.

Inhibition of lipopolysaccharide mitogenicity with characterized anti-lipid A monoclonal antibodies

Antibodies to lipid A were raised in mice immunized with non-hydrolysed Bordetella pertussis microorganisms, coated with lipid A isolated from the same bacteria. Anti-lipid A activity of immune sera was measured by radioimmunoassay. Four hybrid cell lines that secrete antibodies directed against the hydrophobic region of B. pertussis lipopolysaccharide were produced by cell fusion between myeloma cells and spleen cells from immunized C3H/He-PAS mice. Differences were observed in the potency of the isolated monoclonal antibodies to inhibit B cell proliferation induced by lipopolysaccharide (LPS) or by lipid A, suggesting a selective recognition of effector sites present on the hydrophobic region of LPS.

Monoclonal antibodies against surface antigens of Bacteroides gingivalis

Monoclonal antibodies against the various surface antigens of Bacteroides gingivalis were obtained by the fusion of murine myeloma cells (SP2/0-Ag14) with spleen cells of BALB/c mice immunized with the whole cells. Two monoclonal antibodies reacted with lipopolysaccharide, and the other two reacted strongly with capsule antigen. One showed reactivity with the hemagglutinin of the cells. The five monoclonal antibodies reacted with sonicated antigen from all B. gingivalis strains tested. No cross-reactivity of the monoclonal antibodies with antigens from nine species of other black-pigmented Bacteroids strains was observed. An immunoblotting test involving the use of these monoclonal antibodies indicated that the epitope of B. gingivalis lipopolysaccharide was polysaccharide with a high molecular weight of 40,000 to 60,000. The immunoblotting test also demonstrated that the epitopes of capsule antigen and of hemagglutinin were 27,000- and 40,000-molecular-weight proteins, respectively.

Immunological characterization of Vibrio cholerae O:1 lipopolysaccharide, O-side chain, and core with monoclonal antibodies

Lipopolysaccharide (LPS) was extracted from Vibrio cholerae O:1 strains of the serotypes Ogawa, Inaba, and Hikojima and delipidated by mild-acid hydrolysis. Two polysaccharide fragments with the molecular weights of approximately 9,000 and 900, respectively, were isolated by gel permeation chromatography. The LPS preparations and the polysaccharide fragments were studied in enzyme-linked immunosorbent assay inhibition, rocket immunoelectrophoresis, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by electroblotting with monoclonal antibodies directed against the group-specific antigen A, the type-specific antigens B (Ogawa) and C (Inaba), and the core region. Antigen A was demonstrated in all LPS preparations and all 9,000-molecular-weight fragments tested. The type-specific antigens B and C were demonstrated in LPSs and 9,000-molecular-weight fragments from Ogawa and Inaba, respectively. Furthermore, antigens B and C were both demonstrated in LPSs and 9,000-molecular-weight fragments from two of four Hikojima strains tested. Core antigen was demonstrated in the LPS and in the 9,000- and 900-molecular-weight fragments. The results indicate that the 9,000-molecular-weight fragment represents the complete polysaccharide chain, including group- and type-specific antigens as well as core antigens, whereas the 900-molecular-weight fragment constitutes the main part of the core region.

Monoclonal antibodies to outer membrane antigens of Vibrio cholerae

Hybridoma-derived monoclonal antibodies were prepared against outer membrane antigens of four strains of Vibrio cholerae that were cultivated under iron-limited conditions, and these antibodies were partially characterized. We established a library of 66 hybridomas which produced monoclonal antibodies defining 16 different V. cholerae antigens. Two antigens (molecular weights, 18,000 and 112,000) were heat modifiable, whereas the reacting epitope of a third antigen (40,000-dalton-18,000-dalton doublet) was completely destroyed when it was heated at 100 degrees C. The 112,000-dalton heat-modifiable protein was an iron-regulated outer membrane protein. This protein bound 59Fe in vitro when it was combined with the V. cholerae siderophore-iron complex 59Fe-vibriobactin; it was also found in in vivo grown V. cholerae, as were three other antigens. A total of 26 hybridomas produced antibody to V. cholerae lipopolysaccharide. Of these, 12 were cross-reactive with lipopolysaccharides of other gram-negative bacteria, including 2 which recognized lipid A. Several of these anti-lipopolysaccharide monoclonal antibodies appeared to be lipopolysaccharide region specific. Some membrane antigens were strain specific, whereas others were common to both O group 1 and non-O group 1 vibrios.

Characterization of two different antibody specificities recognizing distinct antigenic determinants in free lipid A of Escherichia coli

Antisera were raised in rabbits with acid-treated Re mutant bacteria from Salmonella minnesota and Escherichia coli and tested in a passive hemolysis assay with di- and monophosphorylated free lipid A of E. coli (LipA-Ac and LipA-HCl, respectively) coated onto sheep erythrocytes. Depending on the acid used to prepare the immunogen (acetic versus hydrochloric acid), different antibody specificities were obtained. Antiserum prepared against HCl-treated bacteria was found to react with both antigens to the same extent (i) in the passive hemolysis test, (ii) in the passive hemolysis inhibition test, and (iii) in absorption experiments, suggesting that antibodies in this antiserum recognize an antigenic determinant equally present in LipA-Ac and LipA-HCl. Antiserum raised against acetic acid-treated bacteria reacted with the homologous antigen (LipA-Ac) in the passive hemolysis and passive hemolysis inhibition test as well as in absorption experiments. However, the antiserum failed to react with the heterologous antigen (LipA-HCl) in the hemolysis test and during absorption, whereas in inhibition studies interaction of this antiserum with both antigens was observed. The inhibiting capacity of LipA-Ac was lower compared with that of LipA-HCl, indicating that the antigenic determinant of LipA-Ac is partly expressed by LipA-HCl in solution, but not when fixed on the surface of sheep erythrocytes. The role of glycosidically linked phosphate in lipid A is discussed with respect to antigenicity.

Antigenic heterogeneity of lipopolysaccharides from Campylobacter jejuni and Campylobacter fetus

The lipopolysaccharide (LPS) structure of Campylobacter spp. can be visualized with polyacrylamide gel electrophoresis by examining proteinase K-treated whole cell lysates. Polyacrylamide gel electrophoresis LPS profiles of C. jejuni strains are rough type with low concentrations of low-molecular-weight polysaccharide side chains, serum-resistant C. fetus strains have smooth-type LPS, and serum-sensitive C. fetus strains have rough-type LPS. We electroblotted the proteinase K-treated whole cell lysates of 17 C. jejuni and 9 C. fetus strains from polyacrylamide gel electrophoresis to nitrocellulose paper to examine antigenicity to immune rabbit sera. There was virtually no antigenic cross-reactivity of C. jejuni and C. fetus LPS. Among C. jejuni strains, core LPS structures were cross-reactive, but the O-polysaccharide side chains were best recognized by homologous antisera. Antisera to several serum-resistant C. fetus strains recognized only the polysaccharide side-chain regions of serum-resistant strains and no part of the LPS from the sensitive strain. Antiserum raised against a serum-sensitive C. fetus strain but not homologous antisera recognized the core region of the LPS of the serum-resistant C. fetus strains. These findings suggest that core LPS antigens are widely shared within C. fetus subsp. fetus strains but that in the serum-resistant strains this core region is not surface exposed and therefore not immunogenic to rabbits infected with whole cells.

Protection against fatal Pseudomonas aeruginosa sepsis by immunization with smooth and rough lipopolysaccharides

The protective capacity of various native and mutant lipopolysaccharide antigens against fatal Pseudomonas aeruginosa burn wound sepsis was evaluated. Immunization with O-polysaccharide-deficient lipopolysaccharides derived from Escherichia coli J5 or Salmonella typhi Ty 21a afforded substantial protection against only one of five Pseudomonas aeruginosa challenge strains of various serotypes. Immunization with both lipopolysaccharide antigens evoked antibody of the immunoglobulin G class which recognized lipopolysaccharide isolated from the challenge strain against which protection was noted. This was not seen for the remaining four challenge strains. Attempts to demonstrate cross-serotype protection using O-antigen-deficient and core-deficient Pseudomonas aeruginosa lipopolysaccharide antigens was, for the most part, unsuccessful. In contrast, high levels of protection against all six serotypes of challenge strains were seen following immunization with homologous lipopolysaccharide.

Monoclonal antibodies against bacterial outer membrane antigens

Monoclonal antibodies have proved to be highly specific tools for defining the antigenic epitopes of Pseudomonas aeruginosa outer membrane macromolecules. In this article we have highlighted the use of monoclonal antibodies in the study of lipopolysaccharide heterogeneity and in particular have demonstrated that single monoclonal antibodies can recognize epitopes on lipid A which are conserved in all Gram negative bacteria tested. Monoclonal antibodies against P. aeruginosa outer membrane proteins have been used to demonstrate the strong conservation of specific antigenic sites in all P. aeruginosa strains tested. In the case of one monoclonal antibody, specific for outer membrane lipoprotein H2, the antigenic site recognized by the antibody was also found to be conserved in all group 1 Pseudomonads. The implications of these monoclonal antibodies to bacterial taxonomy is discussed. Monoclonal antibodies against two separate conserved surface epitopes on outer membrane protein F were isolated and differentiated according to their reactions with 2 mercaptoethanol-reduced protein F and with proteolytic and cyanogen bromide peptide fragments of protein F. One of these protein F-specific monoclonal antibodies has been demonstrated to have immunotherapeutic potential.