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J T Poolman

Publications and source records attributed to J T Poolman.

At least 37 records · Page 2Linked to original sources
PubMed1996

Sequence variability of FrpB, a major iron-regulated outer-membrane protein in the pathogenic neisseriae.

The FrpB protein from pathogenic neisseriae is a 77 kDa iron-regulated outer-membrane protein that belongs to the family of TonB-dependent receptors and may have potential as a vaccine component. Comparison between the frpB gene from three different meningococcal strains and a published gonococcal one revealed that the region from residues 350 to 390 displays pronounced sequence variability. In a model for the topology of FrpB in the outer membrane, this region corresponds to loop 7, the longest of the predicted 13 surface-exposed loops. Binding of four out of a total of eight bactericidal monoclonal antibodies to synthetic peptides corresponding to loop 7 showed that their epitopes are located here. The frpB genes from five additional meningococcal strains were cloned and sequenced in this region. Pairwise comparisons showed different degrees of similarity.

Amino Acid Sequence↗
PubMed1996

T-cell responses to outer membrane proteins of Neisseria meningitidis: comparative study of the Opa, Opc, and PorA proteins.

Former studies have shown that the class 5 outer membranes proteins (Opa and Opc proteins) of Neisseria meningitidis are at least as immunogenic as meningococcal porin proteins. High antibody titers to class 5 proteins have been observed in sera obtained during convalescence after meningococcal infection. A strong increase in anti-class 5 antibodies has also been observed in vaccinees who received a meningococcal outer membrane vesicle preparation. The enhanced B-cell response to class 5 proteins may be due to the presence of immunodominant helper T-cell epitopes in these proteins. In order to investigate this hypothesis, we tested purified Opa, Opc, and class 1 proteins for recognition by human T cells. a hierarchy of T-cell immunogenicity was observed among the outer membrane proteins, the Opa protein being more immunogenic than the other proteins. In most cases, the proliferative responses elicited by Opc were higher than the responses observed for the class 1 protein. The epitopes recognized by the immune T cells were identified by using overlapping synthetic peptides spanning the protein sequences of OpaB, Opa5d, and Opc.

Adult↗
PubMed1996

Monoclonal antibodies against conserved epitopes of a 46-kDa protein from Neisseria meningitidis.

The purpose of the present study was to generate monoclonal antibodies (mAbs) against conserved epitopes of B meningococcus which could be applicable to the immunoscreening of bacterial meningitis. Three mAbs reactive to a 46-kDa protein conserved in eight sero-groups and several sero(sub)types of Neisseria meningitidis were selected for the present study. No reaction was detected with whole-cell lysates of Staphylococcus aureus. Streptococcus pneumoniae, Haemophilus influenzae type b or Escherichia coli. Two of these mAbs recognized 46-kDa epitopes in four other Neisseria spp, and the third, MC3.13, cross-reacted only with N. lactamica. All mAbs reacted with whole-cell lysates from a N. meningitidis mutant strain lacking the class 1 outer membrane protein (43-47 kDa). Immunoelectron microscopy revealed a cytoplasmic location for the 46-kDa protein. The MC3.13 monoclonal antibody is potentially applicable to a rapid screening of bacterial meningitis.

Animals↗
PubMed1995

The purification and protective capacity of Bordetella pertussis outer membrane proteins.

The whole cell vaccine (WCV) of Bordetella pertussis is protective in the intracerebral (i.c.) mouse protection assay. We found a correlation between the i.c. mouse protection assay potency and the presence of the virulence-associated outer membrane proteins (OMPs) in outer membrane complexes (OMC). The virulence-associated 92, 32 and 30 kDa OMPs were purified and the N-terminal amino acid sequences were determined. The N-terminal amino acid sequences of the 30 and 32 kDa OMPs show homology with the C-terminal fragment of the P.93 precursor of the 69 kDa OMP (pertactin). The purified 32 kDa OMP was protective in the i.c. test when presented as mixed protein-detergent micelles. The 92 kDa OMP became a protective antigen when nonprotective levels of pertussis toxin were added. We found a correlation between the i.c. mouse protection value and the 92 kDal38 kDa (porin) ratio in OMC preparations.

Amino Acid Sequence↗
PubMed1995

Construction of Neisseria meningitidis strains carrying multiple chromosomal copies of the porA gene for use in the production of a multivalent outer membrane vesicle vaccine.

Starting with Neisseria meningitidis strain H44/76, a set of strains was constructed for use in production of a multivalent outer membrane vesicle vaccine. The aim was to remove unwanted outer membrane components and at the same time to improve the range of protection. This was accomplished through transformation with plasmid constructs made in Escherichia coli and their homologous recombination into the meningococcal chromosome. Deletion of the cps locus resulted in loss of expression of the group B capsular polysaccharide as well as the lacto-N-neotetraose structure in lipopolysaccharide. Deletion of the porB gene abolished expression of the class 3 outer membrane protein. Additional copies of the porA gene, encoding the immunodominant class 1 outer membrane protein, were inserted into one of the opa genes and into the rmpM gene encoding the class 4 outer membrane protein. This construction was done with three sets of porA alleles, resulting in three trivalent strains, each of which expressed a different combination of class 1 epitopes.

Bacterial Vaccines↗
PubMed1995

Serotypes and subtypes of Neisseria meningitidis: results of an international study comparing sensitivities and specificities of monoclonal antibodies.

An international study supported by the World Health Organization comparing monoclonal antibodies for serotyping and serosubtyping of Neisseria meningitidis strains was performed and the results were assessed in 1992. A collection of 6 serotype-specific (1, 2a, 2b, 4, 14, and 15) and 12 serosubtype-specific (P1.1, P1.2, P1.4, P1.5, P1.6, P1.7, P1.9, P1.10, P1.12, P1.14, P1.15, and P1.16) monoclonal antibodies was provided to 11 participating laboratories throughout the world. Monoclonal antibodies were tested on 85 Neisseria meningitidis strains with known reference results. Whole-cell enzyme-linked immunosorbent assay was used for analysis in 10 of 11 laboratories. The sensitivities and specificities of individual serotype- and subtype-specific monoclonal antibodies were evaluated. Differences in individual laboratories and with individual monoclonal antibodies were assessed. Relatively large differences in sensitivities were achieved in individual laboratories. On the contrary, the specificities remained at high levels in all laboratories. The sensitivities of serotype-specific monoclonal antibodies ranged from 72.0 to 100%. Individual serosubtype-specific monoclonal antibodies showed sensitivities ranging from 64.1 to 98.1%. The most frequent reason for the incorrect results obtained with the monoclonal antibodies were false-negative results. The collaborative study demonstrated that some monoclonal antibodies are not very sensitive. Another study to define the most suitable monoclonal antibodies is planned.

Antibodies, Bacterial↗
PubMed1994

Molecular characterization of the structural gene for the lactoferrin receptor of the meningococcal strain H44/76.

The meningococcal lactoferrin receptor is a promising vaccine candidate since it seems to be antigenically rather stable. Monoclonal antibodies against this protein reacted with more than 50% of the strains tested. To gain further insight in its variability, the IbpA gene from strain H44/76, encoding this protein, was cloned and sequenced. This strain does not cross-react with monoclonal antibodies that recognize LbpA of strain BNCV. The deduced amino acid sequence was found to be 95% homologous to the previously established sequence of LbpA of strain BNCV. A topology model was proposed for LbpA, making use of the sequence comparisons and some general rules for the folding of outer membrane proteins. The protein is supposed to traverse the membrane 26 times in a beta-sheet conformation. The epitope recognized by the monoclonals was mapped and found to reside in the largest predicted surface-exposed loop. No iron-regulation of LbpA expression was found in E. coli, probably because IbpA is located in an operon, the promoter of which was not cloned. Upstream of IbpA, a part of an open reading frame was found. Whereas the LbpA protein shows homology to the transferrin-binding protein 1 (Tbp1), the putative protein encoded by the open reading frame upstream of IbpA shows extensive homology to Tbp2, suggesting that iron-acquisition from lactoferrin, like from transferrin, requires two specific proteins in the outer membrane. The upstream open reading frame is tentatively designated IbpB.

Amino Acid Sequence↗
PubMed1994

Non-specific modulation of the immune response with liposomal meningococcal lipopolysaccharide: role of different cells and cytokines.

The immunomodulating action of Neisseria meningitidis lipopolysaccharide (LPS) incorporated into liposomes and the activation of different populations of immunocompetent cells or the secretion of cytokines were studied. LPS stimulated an anti-sheep red blood cell (SRBC) plaque-forming cell response in the spleen of mice after simultaneous injection of LPS and SRBC but if LPS was administered 3 days before the immunization with SRBC the response to SRBC was strongly suppressed. After the incorporation of LPS into liposomes the stimulation index was increased from 6 to 19 and the liposomal LPS did not suppress the immune response to SRBC. The incorporation of LPS into liposomes leads to enhancement of B-mitogenic properties of LPS, as liposomal LPS stimulated the proliferation of splenocytes in mice better than free LPS and has no influence on the thymocytes. The liposomal LPS induced more prolonged and significant accumulation of IgM-secreting cells in the spleen of mice in comparison with the free LPS. Liposomal LPS also induced more active accumulation of IFN-gamma in human peripheral blood mononuclear cells and less active accumulation of monokines, contributing to the realization of the toxic properties of endotoxin (IL-1 alpha, TNF-alpha, IL-6 and GM-CSF). These results demonstrated that the incorporation of N. meningitidis LPS into liposomes dramatically changed its immunomodulating activity. The data obtained are important for the construction of an adjuvant formulation for synthetic immunogens capable of inducing genetically unrestricted immune responses.

Adjuvants, Immunologic↗
PubMed1994

Phenotypic and genotypic changes in a new clone complex of Neisseria meningitidis causing disease in The Netherlands, 1958-1990.

To characterize the phenotypic and genotypic changes that occurred in a new clone lineage of Neisseria meningitidis (lineage III) in the Netherlands, the electrophoretic type (ET) was determined for 79 serogroup B isolates of serotype 4 or subtype P1.4 (or both) obtained between 1958 and 1990 from patients with systemic meningococcal disease. Thirty-five previously described isolates were also included. After its appearance in 1980, lineage III started homogeneously with regard to both genotype (ET-24) and phenotype (B:4:P1.4). After 1984, other clones appeared in the lineage, and the various clones acquired other serotypes (serotypes 14 and 15) and subtypes (P1.2, P1.7, and P1.12), indicating frequent exchange of genetic material between clones. These results indicate that basing a serogroup B vaccine on outer membrane components from a single strain is not a valid strategy for the prevention of meningococcal disease.

Cloning, Molecular↗
PubMed1994

Lipo-oligosaccharide immunotyping of Neisseria meningitidis by a whole-cell ELISA with monoclonal antibodies.

To assess the applicability of a whole-cell ELISA (WCE) with monoclonal antibodies (MAbs) for lipo-oligosaccharide (LOS) immunotyping of Neisseria meningitidis, 675 meningococcal isolates obtained in 1989 and 1990 in the Netherlands and 57 isolates collected in 1974, of which the immunotype had been determined previously by microprecipitation, were analysed. Despite the lack of specific MAbs for L2 and L4, an algorithm was developed for the assignment of immunotypes on the basis of the reaction patterns of the reference strains and these isolates to a combination of 14 MAbs. The immunotypes found by WCE were in accordance with those obtained by microprecipitation and the results from WCE were reproducible. The distribution of immunotypes among isolates of the various serogroups in the Netherlands in 1989-1990 is presented. Based on the reaction patterns of the isolates, two main categories of related immunotypes could be distinguished among isolates of serogroups B and C: L2/L4 and L3/L1/L8. Some isolates of the latter category were of one immunotype, but many isolates expressed one or two additional immunotypes, either strongly or weakly, indicating that the differences in this category are quantitative rather than qualitative. The results of this study have demonstrated that the WCE method for LOS immunotyping is easily applicable and provides better definition of test strains for in-vitro bactericidal assays and research into pathogenesis.

Algorithms↗
PubMed1994

Simultaneous multiple synthesis and selective conjugation of cyclized peptides derived from a surface loop of a meningococcal class 1 outer membrane protein.

Starting from the alpha-(2,4-dimethoxybenzyl) ester of N-(9-fluorenylmethoxycarbonyl)aspartic acid [Fmoc-Asp-ODmb], side-chain-protected resin-bound Fmoc-peptides containing an N epsilon-1-(4,4-dimethyl-2,6-dioxocyclohexylidene)ethyl lysyl [Lys(Dde)] residue were prepared. The C-terminal dimethoxybenzyl esters of aspartic acid were removed with 1% trifluoroacetic acid and 10% anisole in dichloromethane, followed by Fmoc-cleavage in the usual manner. The resin-bound peptides were then cyclized using 1-benzotriazolyloxy-tris-[N-pyrrolidino]phosphonium hexafluorophosphate (PyBOP) in the presence of N-methylmorpholine. The (dimethyldioxocyclohexylidene)ethyl groups of lysine were removed with 1% hydrazine hydrate in N,N-dimethylacetamide, and the liberated side-chain amino functions were modified by reaction with pentafluorophenyl S-acetylmercaptoacetate (SAMA-OPfp). Finally, the peptides were side-chain deprotected, with exception of the Lys(SAMA) residue, and cleaved from the solid support with trifluoroacetic acid/anisole/water, 95/2.5/2.5. Cyclic peptides comprising 7-14 amino acid residues were obtained employing this procedure. As a model conjugation, cyclo[Thr-Asn-Asn-Asn-Leu-Lys(SAMA)-Thr-Lys-Asp] was coupled with bromoacetamide. The same peptide was also coupled with a bromoacetylpeptide to give a well defined peptide/peptide conjugate. All peptides were conjugated to bromoacetylated tetanus toxoid for immunization purposes.

Amino Acid Sequence↗
PubMed1994

Development, characterization, and biological properties of meningococcal immunotype L3,7,(8),9-specific monoclonal antibodies.

In this study, we characterize the properties of nine monoclonal antibodies (MAbs) that recognize meningococcal lipopolysaccharides (LPS). The following three specific MAbs that had not been described previously were elicited in BALB/c mice by using an immunotype L3,7,9 oligosaccharide-tetanus toxoid conjugate in combination with Quil A: 4D1-B3, 3A12-E1, and 4A8-B2. These MAbs reacted with L3,7,9 LPS on immunoblots and in the LPS enzyme-linked immunosorbent assay (ELISA) and recognised strains containing L3, L3,7, L8 (except 3A12-E1), or L9 LPS in the whole-cell ELISA. The six other MAbs have been described in previous studies (K. Saukkonen, M. Leinonen, H. Abdillahi, and J.T. Poolman, Vaccine 7:325-328, 1989; R.J.P.M. Scholten, B. Kuipers, H.A. Valkenburg, J. Danjert, W.D. Zollinger, and J.T. Poolman, J. Med. Microbiol., in press) and were obtained after immunization with outer membrane protein complexes containing LPS: MN15A11, MN15A8-1, MN15A17-1, MN11A11G, MN14F20-11, and MN14F21-11. MN15A11 was specific for L3,7,9 LPS and displayed properties similar to those of 3A12-E1. MN15A17-1, MN14F20-1, and MN11A11G were cross-reactive, and MN14F21-11 was specific for the L1,8 immunotype. Epitope specificities of MAbs reacting with L3,7,(8),9 strains were analyzed. MAbs 4D1-B3, 3A12-E1, and 4A8-B2 recognized phosphoethanolamine group-containing oligosaccharide-specific epitopes. MN15A11 and MN15A17-1 were probably directed against a conformational epitope, although for MN5A11 recognition of an unknown L3,7,9-specific epitope in the 2-keto-3-deoxyoctulosonic acid (KDO)-lipid A region cannot be excluded. MN15A8-1, a strongly cross-reactive MAb, recognized a determinant which included the KDO-lipid A region and the more terminal saccharides.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Immunization of mice with pneumolysin toxoid confers a significant degree of protection against at least nine serotypes of Streptococcus pneumoniae.

Pneumolysin is the thiol-activated cytolysin produced by Streptococcus pneumoniae. Mice were immunized with a genetically engineered toxoid version of pneumolysin, which was derived from a serotype 2 pneumococcus. The toxoid carried the mutation Trp-433-->Phe. Alum was used as the adjuvant. Immunized mice had significantly increased levels of anti-pneumolysin antibodies, principally immunoglobulin G1. Mice were challenged intraperitoneally or intranasally with 12 strains covering capsular serotypes 1 to 6, 7F, 8, and 18C. Following challenge, the survival rate and/or the time of death of nonsurvivors (survival time) was significantly greater than that of sham-immunized mice for all nine serotypes. However, differences in the degree of protection were noted between different strains. The route of challenge also appeared to influence the degree of protection. Nevertheless, the significant, albeit in some cases partial, protection provided against all nine pneumococcal serotypes supports the conclusion that pneumolysin toxoids warrant consideration for inclusion in a human vaccine.

Adjuvants, Immunologic↗
PubMed1994

Comparison of nonhuman primate antibodies against Haemophilus influenzae type b polysaccharide with human antibodies in oligoclonality and in vivo protective potency.

Nonhuman primates are often used as a model for studying vaccines for humans. However, it is not always clear how closely the antibody responses in these species mimic human responses. Recent studies have characterized the human antibody response to Haemophilus influenzae type b (Hib) in great detail. In this study, we have compared the antibody response to Hib of humans with those of other primates. Studies of isoelectric points and V kappa subgroup usage show that, like humans, nonhuman primates produce oligoclonal antibodies. Also, monkey antibodies to the Hib polysaccharide are as protective as human antibodies in an in vivo model of Hib infection. Thus, we conclude that nonhuman primates produce antibodies to Hib polysaccharide that are structurally and functionally similar to human antibodies and are a good model for testing human vaccines.

Animals↗
PubMed1994

Characterization of strains of Neisseria meningitidis recovered from complement-sufficient and complement-deficient patients in the Western Cape Province, South Africa.

Complement deficiency has been associated with increased susceptibility to meningococcal disease. In order to determine whether special meningococcal strains caused disease in complement-deficient (CD) patients, 17 Neisseria meningitidis strains recovered from patients in the Western Cape Province, South Africa, known to be CD were compared with 124 routine isolates obtained from patients living in the same area. Serogrouping of the strains from the CD subjects revealed that the common serogroups, particularly serogroup B, predominated. However, the prevalence of rare serogroups among isolates from CD subjects was significantly higher than that found among isolates from the control group. Sero- and subtyping of the class 1 and class 2 or 3 outer membrane proteins showed no significant difference between isolates from CD subjects and the routine clinical isolates. Multilocus enzyme electrophoresis of the 141 isolates revealed six clusters of electrophoretic types (ETs) and two unrelated ETs. The same degree of genetic diversity existed in ETs of isolates from CD subjects and the control group. However, the ET-5 complex, which is known to be associated with epidemic disease, was found in 22 (18%) of the routine clinical isolates but in none of the isolates from the CD subjects. This difference was marginally significant. What was highly significant was the finding that 8 of the 17 isolates from CD subjects were in one ET cluster, cluster F, which comprised a total of 20 isolates. Thus, our results show a difference in the clonal compositions of the strains that infect CD subjects in comparison with the clonal compositions of those that cause clinical infections in the population at large.

Adolescent↗