Evidence for an extrinsic immunogen in effective ribosomal vaccines from Salmonella typhimurium

A broadly applicable approach to T cell epitope identification: application to improving tumor associated epitopes and identifying epitopes in complex pathogens

Epitopes are a hallmark of the antigen specific immune response. The identification and characterization of epitopes is essential for modern immunologic studies, from investigating cellular responses against tumors to understanding host/pathogen interactions especially in the case of bacteria with intracellular residence. Here, we have utilized a novel approach to identify T cell epitopes exploiting the exquisite ability of particulate antigens, in the form of beads, to deliver exogenous antigen to both MHC class I and class II pathways for presentation to T cell hybridomas. In the current study, we coupled this functional assay with two distinct protein expression libraries to develop a methodology for the characterization of T cell epitopes. One set of expression libraries containing single amino acid substitutions in a defined epitope sequence was interrogated to identify epitopes with enhanced T cell stimulation for a MHC class I epitope. The second expression library is comprised of the majority of open reading frames from the intracellular pathogen and potential biowarfare agent, Francisella tularensis. By automating aspects of this technology, we have been able to functionally screen and identify novel T cell epitopes within F. tularensis. We have also expanded upon these studies to generate a novel expression vector that enables immunization of recombinant protein into mice, which has been utilized to facilitate T cell epitope discovery for proteins that are critically linked to Francisella pathogenicity. This methodology should be applicable to a variety of systems and other pathogens.

Polysaccharide nature of O antigen in protective ribosomal preparations from Shigella: experimental evidence and implications for the ribosomal vaccine concept

Shigella ribosomal vaccine (SRV) was previously shown to be highly active in induction of mucosal and systemic O-antibody response and protection against Shigella infection in guinea pigs and monkeys. In this study, the O-specific component (OSC) was isolated from the SRV by affinity chromatography using rabbit O antibodies coupled to CNBr-Sepharose. The results of the reaction with carbocyanine dye as well as chemical data show that ribosomal OSC is devoid of lipid A and KDO, which are characteristic of classical LPS. The comparison of OSC with various LPS-related substances led to the conclusion that ribosomal OSC is similar to and probably identical with cytoplasmic O polysaccharide (L hapten), an O-side-chain polymer which accumulates in cytoplasm. It is hypothesized that the extremely high immunogenicity of SRV depends on a cooperative action of OSC, representing an epitope-specific part of the vaccine, and a ribosomal particle which serves as a vector, providing amplification of the immunogenic effect. The data obtained indicate the presence of a non-covalent link between the two components of the ribosomal vaccine.

Salivary immunoglobulin A and serum antibodies to Streptococcus mutans ribosomal preparations in dental caries-free and caries-susceptible human subjects

Caries-free subjects or individuals with low caries susceptibility exhibited significantly higher (P less than 0.001) levels of naturally occurring salivary immunoglobulin A (IgA) and serum IgG, IgA, and IgM antibodies to a Streptococcus mutans ribosomal preparation than subjects with high caries susceptibility. Absorption of saliva and serum samples with S. mutans ribosomal preparations, but not with other S. mutans antigens or with Escherichia coli and Neisseria gonorrhoeae ribosomal preparations, removed the antibody activity. Absorption with Streptococcus sanguis ribosomes and NH4Cl-washed S. mutans ribosomes partially removed the anti-S. mutans ribosome antibody activity. These results provide evidence that naturally occurring salivary and serum antibodies to the S. mutans ribosomal preparation correlate with susceptibility to dental caries.

Immunogenicity of transfer RNA isolated from a two-heptose rough mutant of Salmonella typhimurium LT2 in mouse typhoid infection

Transfer ribonucleic acid (tRNA) was isolated from a two-heptose mutant of Salmonella typhimurium LT2 (strain SL1004) and was found to afford 100% mouse protection against challenge with 1000 LD50 of strain LT2. The intraperitoneal minimum effective dose of tRNA was 5 micrograms RNA per mouse and this dose was significantly lower than that of ribosomal RNA for ddY mouse strain. The protective immunity was independent of the presence of antibodies to cell-surface antigens, and was transferred mainly by T cells. The protective moiety of tRNA was sensitive to ribonuclease digestion which resulted in 85% reduction in the mouse survival rate, but was completely resistant to protease digestion. The present study demonstrates that the immunogenic activity of salmonella RNA is present in both ribosomal RNA and tRNA.

Analysis of cell wall and membrane contamination of ribosomal preparations from Streptococcus mutans

A ribosomal preparation from a cariogenic strain of Streptococcus mutans was examined for cell wall and membrane contamination. A biochemical characterization established that the preparation contained 61.0% RNA and 39.0% protein. Carbohydrate was not detected by phenol-sulfuric acid or methyl pentose assays. Glucosyltransferase and D-succinate dehydrogenase, which are cell wall- and membrane-associated enzymes, respectively, were not found. However, D-lactate dehydrogenase, another membrane-associated enzyme, was present in the preparation. A comparison of two-dimensional gel electropherograms of a mixture of cell walls and membranes and the S. mutans ribosomal preparation revealed contamination of the latter sample with at least six cell wall- or membrane-associated proteins. Adsorption of a rabbit antiserum raised against the ribosomal preparation with whole S. mutans cells abrogated antibodies directed against at least two proteins from the ribosomal preparation. Immunodiffusion plates showed reactivity of this antiserum against preparations of purified lipoteichoic acid from Streptococcus pyogenes and S. mutans. Adsorption of rat and rabbit antisera against the ribosomal preparation with the cell wall-derived materials glucosyltransferase, lipoteichoic acid, glucan, and a Rantz-Randall extract reduced the concentration of antibodies against the ribosomes by as much as 10-fold. These data indicated that the preparation was contaminated with at least six cell wall proteins, one cell membrane-associated enzyme, and lipoteichoic acid.

Immunogenic dialyzable factor derived from a ribosomal fraction of Salmonella typhimurium. II. Isolation and characterization of the protective moiety in the dialyzable factor

An immunogenic dialyzable factor was obtained by dialysis of the freeze-thawed ribosomal fraction derived from a smooth virulent strain (LT2) of Salmonella typhimurium. Ion exchange chromatography of the dialyzable factor on Dowex 1-X2 (Cl- form) demonstrated the presence of four peaks and the fourth peak eluted with 0.4 M NaCl in 0.005 N HCl was found to be necessary for protection. This effective peak was not obtained by chromatography of nonprotective dialyzable factors such as an RNase digest. Dowex chromatography of the dialyzable factors isolated from rough mutants of strain LT2 revealed that the dialyzable factor of strain SL1004 whose live vaccine is capable of inducing protective immunity contained fairly large amounts of peak IV. DEAE-cellulose for two-dimensional thin layer chromatography was used to identify the composition of the dialyzable factor and peak IV. Eight spots were located under ultraviolet light and seven spots were characterized by their absorption ratios. In peak IV, four nucleotides were located and identified by comparison with a map of the original dialyzable factor. The data show that the effective components of the dialyzable factor are mixed nucleotides and may be unique to ribonucleic acids of strains of S. typhimurium in which live vaccines are capable of affording mouse protection.

Immunogenic dialyzable factor derived from a ribosomal fraction of Salmonella typhimurium. I. Preparation of the protective dialyzable factor from the ribosomal fraction by the freeze-thaw procedure

The preparation, properties, and immunogenicity of the dialyzable factor from a ribosomal fraction of Salmonella typhimurium are described. The ribosomal fraction was purified to eliminate O-antigenic components, by affinity chromatography (Sepharose-anti-O antibody conjugates used as immunoadsorbent). The dialyzable factor was obtained in the concentrated dialysate of the purified ribosomal fraction which was alternately frozen in dry-ice acetone and thawed in an 80 C water bath, for a total of five or six cycles. When this preparation was tested for its ability to protect mice against challenge with 1,000 LD50 of the homologous bacteria, it afforded 100% protection at a dose equivalent to 5.0 micrograms of RNA. The protection conferred by this factor was mainly cell mediated but immune serum enhanced this immunity despite the fact that no antibodies were detected in it. The protective activity of this factor was sensitive to RNase digestion but resistant to proteolytic enzymes. Ion exchange chromatography of this factor with DEAE-Sephadex A-25 (in 7 M Urea-0.02 M Tris-HCl buffer, pH 7.5) resulted in a single A260 peak which was found to be immunogenic. Chemical analysis of this peak after it was concentrated and desalted revealed that this immunogenic fraction was composed mainly of mixed nucleotides. The data indicate that protective immunity conferred by a ribosomal vaccine is associated with RNA but may not require the intact RNA molecule.

Humoral and cell-mediated responses to a ribosomal preparation from Streptococcus mutans

Streptococcus mutans 6715 ribosomes disrupted in a Braun homogenizer were isolated in sodium dodecyl sulfate by differential centrifugation. This preparation contained 80% RNA and 20% protein, and carbohydrate was not detected by phenol-sulfuric acid and methyl pentose assays. The sedimentation coefficient of the ribosomes was 70S. After dialysis in 0.01 M phosphate buffer containing 10(-4) M MgCl2, the ribosomes dissociated into 54S and 32S particles. Leukocytes from rabbits immunized intramuscularly with the ribosomal preparation showed transformation and migration indices of 13.0 and 0.71, which were significantly different (P less than 0.05) from the respective indices of 0.9 and 0.98 in nonimmunized animals. Hyperimmune serum from these rabbits agglutinated representative Formalin-killed strains of all seven serotypes of S. mutans, inhibited adherence of live S. mutans 6715 to glass, and agglutinated S. mutans 6715 ribosomes adsorbed upon erythrocytes. These findings suggested that animals immunized with S. mutans ribosomes may be protected from caries caused by any of the seven serotypes of this organism.

The protein-lipopolysaccharide complex extracted with trichloracetic acid from Salmonella typhimurium effective in protection of mice against S. typhimurium infection

A protein-lipopolysaccharide complex has previously been postulated as necessary to protect susceptible mice against Salmonella typhimurium infection. Lipopolysaccharide attached to non-specific proteins, bovine serum albumin or methylated BSA, gave a specific delayed-type hypersensitivity (DTH) reaction when injected into the footpad of mice sensitized with sublethal doses of S. typhimurium. However, immunization of BALB/c mice with the complex gave no survivors after challenge with 100 LD50 S. typhimurium. Trichloracetic acid extraction of bacterial cultures produced lipopolysaccharide with attached protein. This method gave simple and convenient production of an active factor, demonstrating few major protein bands after electrophoresis. The complex elicited specific DTH reactions in sensitized mice and protected 37% of BALB/c mice against 100 LD50 S. typhimurium. Combinations of protein:lipopolysaccharide were used in DTH experiments to determine the relative importance of the components. A minimum requirement for both was demonstrated, although the ratio was not critical. Use of O-antigenic mutant strains of Salmonella indicated a role for protein in the specificity of activity of the complex.

Immunoprotective activity of capsular polysaccharide in Klebsiella pneumoniae ribosomal preparations does not involve ribonucleic acid

Two peaks were obtained by cesium chloride density gradient ultracentrifugation of Klebsiella pneumoniae ribosomal preparations. Peak I contained capsular polysaccharide, lipopolysaccharide, protein, and less than 0.5% ribonucleic acid. Peak II consisted mainly of ribonucleic acid, with low amounts of protein and capsular polysaccharide. Expressed as capsular polysaccharide content, the 50% protective dose of peak I and of nonfractionated ribosomal preparations was nearly constant (2.6 and 1.2 ng, respectively). Since peak I contained less than 0.5% ribonucleic acid, these results provide evidence that ribosomal ribonucleic acid is not required for protection of mice by K. pneumoniae capsular polysaccharide which contaminates ribosomal preparations.

Role of outer envelope contamination in protection elicited by ribosomal preparations against Neisseria gonorrhoeae infection

A recent report (Cooper et al., Infect. Immun. 28:92-100, 1980) demonstrated that immunization of guinea pigs with ribosomal preparations was protective (approximately 90%) against chamber infections with Neisseria gonorrhoeae. Similar protection has been demonstrated with other cellular immunogens such as outer membranes (OM) (92%) or purified lipopolysaccharide (LPS) (83%). Protection of LPS (5 to 100 micrograms) was dose dependent (83% with 100 micrograms). Treatment of LPS with pronase reduced the protection by 50%. Ribosomal preparations contained LPS contamination (3.9%) based on dry weight determinations by 2-keto-3-deoxyoctonate analysis. Analysis of ribosomal preparations isolated from cells after lactoperoxidase-mediated 125I labeling indicated a major OM contamination (Protein I). The ribosomal preparation also contained low levels of succinic and lactic dehydrogenase. Passive hemagglutination tests revealed that sera from guinea pigs immunized with ribosomal preparations also demonstrated antibody to OM proteins and LPS. LPS was able to absorb one line of precipitation seen in immunodiffusion reactions as well as the bactericidal activity of such sera. OM preparations were unable to absorb the remaining precipitin line or remove the bactericidal activity. It appears that LPS is the major antigen responsible for the bactericidal activity seen in ribosome-immune sera.

Antigenic modification: its relation to protective host resistance in murine salmonellosis

Both the physical state of the immunogen and the route of immunization were found to be extremely important in inducing effective host resistance against salmonellosis.

On the immunogenicity of ribosomes and ribosomal proteins isolated from Klebsiella pneumoniae and Streptococcus pneumoniae

The two pathogenic species Streptococcus pneumoniae and Klebsiella pneumoniae were used to analyze the immunogenic role of proteins in ribosomal preparations. The protective activity of ribosomes prepared from either strain and further purified by washing with high-salt concentrations, followed or not by sucrose gradient separation of the particles, was identical to that of crude unwashed ribosomes. Similarly, no substantial alteration of the level of protection was observed after treatment with the antibiotic puromycin. Therefore, the immunizing efficacy of ribosomes does not appear to be due either to the nonribosomal proteins adsorbed at the surface of organelles or to the growing polypeptide chain. It seems rather to be attributable to the structural ribosomal proteins themselves, which were indeed shown to induce alone a significant level of protection.

Direct evidence for the involvement of capsular polysaccharide in the immunoprotective activity of Klebsiella pneumoniae ribosomal preparations

Previous work has demonstrated the capsular serotypic specificity of the protection conferred on mice by Klebsiella pneumoniae ribosomal preparations. The data in these studies support the hypothesis that capsular polysaccharide plays at least some role in the specificity of the protection conferred by ribosomal preparations. In this investigation, the presence of capsular polysaccharide and lipopolysaccharide in K. pneumoniae ribosomal preparations was demonstrated by using immunodiffusion tests. Lipopolysaccharide content was determined for mice treated with actinomycin D. The serotype of O antigen did not play a role in the orientation of the specificity of the protection. The possibility that lipopolysaccharide might act as an adjuvant was not unlikely since the ribosomal preparations which contained the greatest amounts of lipopolysaccharide appeared to be the most immunoprotective preparations. Ribosomal preparations extracted from a noncapsulated mutant of K. pneumoniae did not protect mice. This finding suggested that capsular polysaccharide might play a role in the immunoprotective activity of ribosomes. This hypothesis was tested by using K. pneumoniae K2 bacteriophage-associated-glycanase, which specifically hydrolyzed K. pneumoniae K2 capsular polysaccharide and thereby suppressed the immunoprotective activity of K. pneumoniae K2 ribosomal preparations. In contrast, the K2 bacteriophage-associated glycanase did not interfere with the immunoprotective activity of K. pneumoniae K1 ribosomal preparations. These results clearly demonstrate that capsular polysaccharide, which is an extraribosomal antigen, is involved in the immunoprotective activity of K. pneumoniae ribosomal preparations.

O-antigenic specificity of the protective supernatant factor from Salmonella typhimurium effective in S. typhimurium-infected mice

A supernatant factor (SF) prepared from cultures of Salmonella typhimurium protected naturally susceptible inbred mice against challenge with S. typhimurium subcutaneously injected (s.c.i.), but not against Salmonella enteritidis, suggesting tha the relevant specificity involved lipopolysaccharide. Further experiments were performed with two transductant strains of S. typhimurium. Strain SH6701 has O-antigen 4 from S. typhimurium and SH6703 had O-antigen 9 from S. enteritidis. Immunization with SF from SH6701 protected 95% BALB/c mice challenged with 100 LD50 S. typhimurium s.c.i., whereas SH6703 immunization had no effect on survival or mean survival time. SH 6703 SF gave some protection against homologous challenge. Antibody titres and delayed-type hypersensitivity reactions were also tested in immunized mice. The SF was, therefore, specific in that O-antigen 4 was necessary to protect mice against S. typhimurium challenge. Since we have previously demonstrated protein to be necessary for protection by SF, the active factor may be in the form of a protein-lipopolysaccharide complex.

Immunogenicity of ribosomal preparations from Neisseria gonorrhoeae

Protection against gonococcal infection was obtained by immunization with ribosomal preparations from Neisseria gonorrhoeae. Ribosomes were isolated from disrupted cells by differential ultracentrifugation and treatment of the microsomal fraction with 0.25% sodium dodecyl sulfate. The isolated ribosomal preparations contained 55% ribonucleic acid, 39% protein, and 0.35% carbohydrate. The ribosomal preparations contained small amounts of endotoxin as determined by thiobarbituric acid- and lead acetate-sensitized mice assays. Guinea pigs immunized subcutaneously with ribosomal preparations were challenged intrachamberially with 10(7) colony-forming units of N. gonorrhoeae, and protection was assessed by clearance of the organism from subcutaneous chambers. The ribosomal preparations elicited significant protection, which was enhanced by incoporation of the immunogen into adjuvant. This protection was comparable to that obtained with whole cells. Treatment with proteolytic enzymes destroyed the protective effect of the ribosomal preparations, but ribonuclease had no measurable effect. Passive hemagglutination and immunodiffusion tests with sera from immunized animals demonstrated the presence of antibody to the ribosomal antigens. Results of adsorption of antiribosomal sera with enzyme-treated ribosomal preparations also indicated the protein nature of the immunogen. These results indicate that protein associated with the gonococcal ribosomal preparation is the major protective immunogen. The role of endotoxin contamination in the immunogenicity of gonococcal ribosomal preparations warrants further investigation.

Immunogenicity of ribosomes from enzymatically lysed Streptococcus pyogenes

Ribosomal fractions isolated from Streptococcus pyogenes by physical and enzymatic disruption of the cell wall were found to provide protection in mice against challenge with the homologous M type. Although ribosomal fractions isolated by physical disruption of the cells also provided protection against challenge with several heterologous M types, ribosomal fractions from enzymatically lysed cells did not provide protection against any of the heterologous M types. Ribosomes isolated by either method were found to be contaminated with cell surface proteins. Chemical analysis of the ribosomes showed a greater protein:ribonucleic acid ratio in ribosomes from physically disrupted cells than in ribosomes from enzymatically disrupted cells (2:1 versus 1:1). Antisera to ribosomes isolated from physically disrupted cells detected many more antigenic determinants on ribosomes isolated from enzymatically disrupted cells than did the corresponding homologous antisera. Immunodiffusion analysis suggested that ribosomes isolated from physically disrupted cells may contain cell wall antigenic determinants which are present on ribosomes isolated from enzymatically disrupted cells in a partially degraded form. Washing of ribosomes in high-molarity salt solutions suggested that some of the contaminating cell wall proteins are tightly bound to the ribosomes.

Immunogenicity of the ribosomal fraction of Salmonella typhimurium: analysis of humoral immunity

The ribosomal fraction prepared from Salmonella typhimurium LT2 was further purified by gel filtration of Sepharose 4B and afforded excellent protection against homologous challenge. The highly effective immunogens were composed of several fractions which could give different types of protection to mice. The first type of protection was heat-labile antigens which could induce humoral immunity, and the second type of protection was heat-stable antigens capable of evoking cellular resistance in mice. The former were different from O-antigens and the latter were free of endotoxin and rich in ribonucleic acid. The third type of protection was heat-resistant substances of cell wall components, which were mainly composed of O-antigens. The high immunogenicity observed in this study could be obtained only by the heat-stable antigens rich in ribonucleic acid, and the immunity conferred by this kind of antigen was due to the cellular type of protection.

Immunization of mice with Trypanosoma cruzi polyribosomes

Studies were carried out with a polyribosomal fraction isolated from Trypanosoma cruzi Y epimastigotes, with the intention to determine both its immunogenic activity and the degree of protection it could induce against experimental T. cruzi infection. This fraction was assayed in four groups of mice by using different schedules of vaccination and varying the dose, intervals, and route of administration. Seven days after the last dose, the animals were sacrificed for immunological studies or subjected to challenge with T. cruzi trypomastigotes. The results obtained in all schedules showed that our polyribosomal fraction only induced a weak antibody response, but was capable of evoking an expressive cellular response. It was also shown that this fraction has the capacity of inducing a high degree of protection against T. cruzi infection, as determined by the decrease of parasitemia and the prolonged survival time of immunized animals.

Role of interferon in mice in protection against influenza A virus by bacterial ribosomes together with membranal glycoproteins of Klebsiella pneumoniae as adjuvant

Nonspecific protection against infectious aerosols of influenza A virus was obtained in Swiss mice after vaccination by aerosols of bacterial ribosomes together with membranal glycoproteins extracted from Klebsiella pneumoniae as the adjuvant. It was shown that repeated stimulant aerosols were necessary to obtain this protection. Routine estimation of serum interferon levels after administration of the association of ribosomes plus membranal glycoproteins to the animals by aerosol or intravenous route showed that there was no correlation between protection and the presence of serum interferon. It was shown that the serum interferon-inducer activity was due to ribosomes. No induction of serum interferon was obtained with membranal glycoproteins used separately. Local liberation of interferon in the mucous membrane of the upper respiratory tract was not investigated.

Identification of protective cell surface proteins in ribosomal fractions from Salmonella typhimurium

Cell surface antigen preparations from Salmonella typhimurium SR-11 prepared by either trichloroacetic acid extraction or boiling in sodium dodecyl sulfate were able to protect C3H/HeJ, C3H/HeDub, and A/J mice. Some of the proteins found in these preparations were shown to exist in the protective ribosomal fraction isolated from S. typhimurium SR-11. Passage of ribosomes isolated from S. typhimurium SR-11 and 6707 through a Sepharose 2B column removed the protective immunogen from 6707 ribosomes but did not completely remove it from SR-11 ribosomes. Immunity to salmonella infection in C3H/HeJ mice induced by ribosomal vaccines may be dependent on the presence of cell surface proteins in the ribosomal fraction.

Evaluation of a ribosomal vaccine against pertussis

A crude ribosomal vaccine derived from Bordetella pertussis administered to ICR and N:NIH (SW) strains of mice protected them effectively against a standardized intracranial challenge. The dose of vaccine that protected half the mice was less for N:NIH (SW) than for ICR mice and compared favorably with a killed reference vaccine. Ribosomes prepared from bacteria ground with washed sea sand were more immunogenic than those obtained by rupture with alumina or with a Braun homogenizer. The protective effect of the crude ribosomes was not an innate part of the organelle but was due to a substance or substances that could be removed from them by a 1 M NH4Cl wash. The material in the wash was highly immunogenic and retained both the histamine-sensitizing and leukocytosis-promoting properties. It lost much of the dermonecrotic activity and was poorly pyrogenic in rabbits. The most potent pyrogen was present in the washed ribosomes, which apparently, retained the endotoxic components of the cell wall. The best vaccines permitted acceptable weight gain in the immunized mice.

Capsular serotypic specificity of the protection conferred on mice by Klebsiella pneumoniae ribosomal preparations

Klebsiella pneumoniae ribosomal preparations protect mice immunized by the subcutaneous route against an intraperitoneal challenge of 100 50% lethal doses. The minimal protective doses are 5 and 0.4 micrograms of proteins for preparations extracted from strains of capsular serotypes 1 and 2, respectively. This difference in protective activity is also found in bacteria killed by Formalin. The protective activity of these preparations is not diminished by their purification on sucrose gradient, which eliminates most of the membrane vesicles which are visible by electron microscopy. The use of four strains of K. pneumoniae belonging to capsular serotypes 1 and 2 allowed us to show that the immunoprotective capacity of the ribosomal preparations was specific to the capsular serotype of the origin strain. This was confirmed by experiments in which the serum of immunized mice was transferred passively. The experimental data favor the presence in the ribosomal preparation of antigens belonging to the bacterial surface and resisting elimination by ultracentrifugation on sucrose gradient. Those surface antigens (possibly capsular polysaccharide) at least play a role in the orientation of the specificity of the protection induced by the ribosomal preparations.

Regulation of the immune response by macrophages

Regulation of the immune response by macrophages was studied with cellular resistance to Listeria monocytogenes as parameter. The use of agents which suppress macrophage activity during the induction-phase of immunity enabled the induction of protective immunity with killed listeria. Fractionation of the cell content of listeria yielded an RNA'se sensitive fraction which in a dose of 300 ng and in combination with the cationic surfactant dimethyl dioctadecyl ammonium bromide induced protective immunity against listeria.

Passive immunization against Pseudomonas with a ribosomal vaccine-induced immune serum and immunoglobulin fractions

Passive protection of mice against Pseudomonas aeruginosa using specific antisera and immunoglobulin fractions induced by immunizing rabbits with a ribosomal vaccine is reported. The results demonstrated that protection by the ribosomal vaccine against challenge with live organisms can be serum mediated. Previous work has shown that the vaccine can be separated into two components on the basis of molecular weight and that both higher (peak A)- and lower (peak B)-molecular-weight fractions were capable of inducing active immunity in mice. The present report indicates that both fractions are also capable of eliciting the production of mouse-protective antibody in rabbits. Agar gel diffusion with antisera to peaks A and B or unfractionated vaccine indicated a common antigenic component among them in addition to an extra antigen in unfractionated vaccine not present in peak B. Passive hemagglutination with antisera to peaks A and B demonstrated high-titer agglutinating antibody only with antiserum to peak A when a method of erythrocyte sensitization for lipopolysaccharide antigens was used. Also, passive hemagglutination was greatly inhibited by small amounts of lipopolysaccharide prepared from the same organism from which the vaccine was made. Both antisera to peaks A and B fixed complement with either A or B antigens. Antisera to peaks A and B, when reacted with peak B antigen, had about the same complement fixation titer (as determined by a quantitative complement fixation test). However, when peak A antigen was used, antiserum to peak A had about twice the complement fixation titer that antiserum to peak B had. These results are consistent with previous observations which suggest that the ribosomal vaccine contains lipopolysaccharide in addition to an unidentified immunogenic principle associated with ribosomes. Furthermore, this immunogen was present in both peaks A and B, but detectable amounts of lipopolysaccharide were present only in peak A. The relative importance of the immunoglobulin G (IgG) and IgM classes of antibodies was also compared. The results indicated that both IgG and IgM isolated from immune rabbit serum are protective in mice. Only IgG precipitated with the vaccine in agar gel diffusion, but both IgG and IgM were active in passive hemagglutination and in complement fixation. The passive hemagglutination titer of the IgM was higher than that of the IgG, but the complement fixation titer of the IgG was higher than that of the IgM. The mouse-protective capability of the IgG and IgM was about the same.

Protective effects of a supernatant factor from Salmonella typhimurium on Salmonella typhimurium infection of inbred mice

A supernatant factor prepared from 48-h cultures of Salmonella typhimurium has been used to immunize mice against subsequent challenge with normally lethal doses of S. typhimurium. The mouse strains used, C57BL and BALB/c, were sensitive to S. typhimurium with 50% lethal doses of less than 50 organisms. Two doses of supernatant factor, given intraperitoneally 20 days apart, protected mice against a subcutaneous challenge dose 10 days later of 100 50% lethal doses of S. typhimurium, resulting in 50 to 80% survival. The viable counts were reduced initially in organs of immunized mice compared with controls, and the multiplication of bacteria was delayed, although the final levels found in the organs would normally have been lethal. Protection obtained was specific for S. typhimurium in that no increased survival was shown after Salmonella enteritidis challenge of immunized mice. Although lipopolysaccharide was demonstrated in the supernatant factor, lipopolysaccharide alone did not protect challenged mice. Supernatant factor produced delayed-type hypersensitivity reactions in mice sensitized with nonlethal doses of Salmonella. The nature of the active factor, found to be partially protein, has yet to be elucidated.

Pseudomonas ribosomal vaccines: preparation, properties, and immunogenicity

The preparation, properties, and immunogenicity of ribosomal vaccines from Pseudomonas aeruginosa are described. These preparations, containing protein and RNA, were tested for immunogenicity by active immunization of mice and subsequent challenge with homologous, live bacteria. The results demonstrated that vaccines prepared from a majority of serotypes used were immunogenic, i.e., afforded 60 to 100% mouse protection against a challenge inoculum containing 8 to 50 50% lethal doses. In some cases vaccine doses as low as 1 microgram of RNA provided 100% mouse protection. Molecular sieve chromatography of a highly immunogenic ribosomal preparation on Sepharose 4B demonstrated the presence of two molecular weight fractions: (i) peak A, an excluded peak (thus having a molecular weight of at least 2 times 10(7)), and (ii) peak B, considerably retarded, with an elution position corresponding to a molecular weight of about 2.2 X 10(6), approximating that of typical 70S ribosomes. Both peaks A and B were immunogenic; however, the immunogenicity of peak A was greater (i.e., a smaller immunizing dose was required) than that of peak B. Peak A was shown to contain components of lipopolysaccharide in addition to protein and RNA (which comprised 80% of the dry weight of peak A). On the other hand, peak B was shown to be free of lipopolysaccharide, and 100% of its dry weight consisted of protein and RNA.

Immuno-stimulation by a ribosomal vaccine associated with a bacterial cell wall adjuvant in humans

We have studied a new vaccine of ribosomal nature associated with glycoprotein cell walls from Klebsiella pneumoniae which served as an immunoadjuvant. Thus vaccine was administered by the aerosol route to working men free of any important disease, especially of respiratory disease. A total of 104 men working for the Commissariat à l'Energie Atomique, all volunteers, were randomly placed into two groups. During the first period, 51 patients (group I) were vaccinated three times a week during 5 weeks, and the second group was used as control. During the second period, which started on day 225, the control group received the vaccine, and the first group was revaccinated. Results of this experience show a significant difference in the immunity of the two groups. The specific antibodies increased with vaccination as illustrated by chi-square test (Yates correction), which corresponds to an independent probability equal to 0 (P = 0.5 X 10-4).

Immunogenic capacity of ribosomes of Salmonella typhi interfered with a flagellin-like material contaminant

The double-immunodiffusion technique and sodium dodecyl sulfate-polyacrylamide electrophoresis were used to demonstrate the presence of flagellin-like material strongly attached to ribosomes of Salmonella typhi Ty 2. This flagellin-like material contaminating the ribosome preparation interferes with the induction of antiribosome serum promoting the formation of antisera reacting either only with flagellin or in some cases with flagellin and ribosomes, but giving a very weak reaction with the latter. The interference is also observed when purified ribosomes from a nonflagellated mutant of S. typhi (S. typhi O-901) mixed with purified S. typhi Ty 2 flagellin are utilized as antigens. The antiribosome sera obtained with ribosomes from S. typhi O-901 have a considerably higher titer than those that are interfered with. These sera were able to react with ribosomes obtained from several related species and did not react with flagella-derived flagellin of S. typhi Ty 2.

Comparative efficacy and toxicity of a ribosomal vaccine, acetone-killed cells, lipopolysaccharide, and a live cell vaccine prepared from Salmonella typhhimurium

The protective and toxic properties of a ribosomal vaccine prepared from Salmonella typhimurium W118-2 were systematicaly compared with those of an acetone-killed whole cell vaccine, purified lipopolysaccharide, and living cells in CD-1 mice. Tests of graded immunizing doses of each vaccine against several challenge doses of live strain W118-2 showed that, although the protection given by ribosomes approached the levels of protection conferred by living organisms, acetone-killed cells administered in appropriate dosages provided levels of protection comparable to that of ribosomes. Lipopolysaccharide was found to be significantly less protective than the other vaccines. On a dry-weight basis, ribosomes were the least toxic with a 50% toxic dose (TD50) of 5,000 microgram; acetone-killed cells had an intermediate TD50 of 1,400 microgram; and lipolysaccharide was the most toxic, with a TD50 of 320 microgram. The dose of each vaccine that protected 50% of the mice against a challenge of 1,00 times the 50% lethal dose was determined and divided by the TD50 to give the therapeutic index. This ratio also indicated that the ribosomes and acetone-killed cells were equally effective, whereas lipopolysaccharide was markedly inferior.

Characterization of the immunoprotective antigen of ribosomal preparations from Haemophilus influenzae

This investigation was designed to characterize the immunoprotective antigen of ribosomal preparations from Haemophilus influenzae. The ribosomes that elicited 80 to 90% protection contained 25% protein and 75% ribonucleic acid but did not contain any detectable hexoses. The immunodiffusion and hemagglutination inhibition tests also failed to demonstrate that the capsular material (polyribose phosphate) was in ribosomal preparations. Treatment of ribosomes with ribonuclease degraded 78% ribonucleic acid but did not affect the immunogenicity of such preparations. The proteolytic enzymes reduced the immunogenicity of ribosomes corresponding to the amount of protein degraded. The protection elicited by ribosomal protein extracted with 2-chloroethanol was comparable to that induced by intact ribosomes. In contrast, the low levels of protection observed by immunization with phenol-extracted ribonucleic acid were dependent on the amounts of contaminating protein. Finally, immunogenicity of ribosomal ribonucleic acid and protein was abrogated by treatment with proteolytic enzymes. These results clearly indicate that the protein associated with Haemophilus ribosomes is the major immunoprotective antigen.

Direct evidence for the presence of lipopolysaccharide components in Pseudomonas ribosomal vaccine

The presence of sugars specific to lipopolysaccharide, glucose, and rhamnose was demonstrated in a Pseudomonas ribosomal vaccine. The detection of these sugars was accomplished by radiological means after paper chromatography of the neutral fraction of acid-hydrolyzed vaccine.

Role of endotoxin contamination in ribiosomal vaccines prepared from Salmonella typhimurium

Ribosomal vaccines prepared from Salmonella typhimurium SR-11 and 6707 an Re mutant bacterium of strain LT2, were effective immunogens in A/J and C3H/HeDub inbred mice. Only SR-11 ribosomes were able to induce significant protection in C3H/HeJ mice. C57BL/6J mice were not protected by either ribosomal preparation. A/J mice were protected against salmonella infection by purified SR-11 endotoxin preparations. Neither the C3H/HeDub, the C3H/HeJ, nor the C57BL/6J mice were protected by the endotoxin preparation. Passive hemagglutination studies showed that C3H/HeJ mice had no antibodies to O antigen but were significantly protected by SR-11 ribosomes. In contrast, C57BL/6J mice, which had the highest titers of O antibodies of the four inbred mouse strains, were not protected by SR-11 ribosomes. Endotoxin cannot totally account for the effectiveness fo ribosomal account for the effectiveness of ribosomal vaccines prepared from S. typhimurium.

Variability of protection in inbred mice induced by a ribosomal vaccine prepared from Salmonella typhimurium

Ribosomal vaccines prepared from Salmonella typhimurium were effective immunogens in A/J inbred mice and C3H/HeTex, inbred mice. However, ribosomal vaccines were not protective in C57BL/6J inbred mice. A/J mice were protected against lethal challenge by attenuated S. typhimurium live-cell, ribosomal, phenol, and heat-killed vaccines. C3H/HeTex mice were protected by live-cell, ribosomal, and phenol vaccines but not the heat-killed vaccine. Only the live-cell vaccine gave significant protection in the C57BL/6J inbred mice. A comparison of the kinetics of infection in sham-immunized mice and mice immunized with ribosomes showed that ribosome preparations elicited protection against Salmonella infection in mice inherently sensitive and resistant to Salmonella.