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Biomedical subjects

M S Blake

Publications and source records attributed to M S Blake.

At least 19 recordsLinked to original sources
PubMed1992

Gonococcal porin vaccine evaluation: comparison of Por proteosomes, liposomes, and blebs isolated from rmp deletion mutants.

The gonococcal major outer membrane protein, Por (protein I), is a potential vaccine candidate. A large-scale animal trial compared the immunogenicity of Por inserted in liposomes (mimicking its in vivo structure) with previously used vaccines containing Por. Por was purified from Rmp (protein III)-negative gonococcal mutants and made into five different formulations: proteosomes, proteosomes absorbed to alum, liposomes, gonococcal membrane blebs, and gonococcal membrane blebs absorbed to alum. Por liposomes induced the greatest amount of Por antibodies; proteosomes and both preparations of blebs induced minimal amounts of Por antibodies. Proteosomes absorbed to alum induced slightly lower amounts of Por antibodies than did liposomes, especially when protein IA was used. Whole-organism absorption studies revealed that a significantly greater percentage of liposome-induced Por antibodies recognized exposed portions of the protein than did proteosome- or proteosome/alum-induced antibodies.

Adjuvants, Immunologic↗
PubMed1992

Antibodies against IgA1 protease are stimulated both by clinical disease and asymptomatic carriage of serogroup A Neisseria meningitidis.

IgA1 protease was purified from a strain of serogroup A Neisseria meningitidis subgroup IV-1, representative of bacteria that caused an epidemic of meningococcal meningitis in The Gambia in 1982-1983. ELISAs and immunoblot assays were done using this protease as antigen with paired acute- and convalescent-phase sera from patients from that epidemic and from one in Finland caused by other serogroup A meningococci. Paired sera were also tested from healthy Gambians who were persistent nasopharyngeal carriers, persistent noncarriers, or persons who became carriers after the first serum sample was taken. The results correlated well between the two methods: Antibodies were stimulated by disease or acquisition of carriage, and they remained at a constant level upon continued carriage.

Antibodies, Bacterial↗
PubMed1992

Gonococcal lipooligosaccharide sialylation prevents complement-dependent killing by immune sera.

Previous investigators have demonstrated that a sialic acid residue is added to the terminal galactose moiety of gonococcal lipooligosaccharide (LOS) when incubated with 5'-CMP-N-acetylneuraminic acid. When this in vitro sialylation occurs, gonococci become resistant to the bactericidal activity of normal human serum. This is believed to result because the added sialic acid residue blocks the binding of bactericidal anti-LOS antibodies present in normal human serum. We extend these studies by demonstrating that sialylated gonococci also become resistant to the bactericidal effect of immune sera containing antibodies that recognize exposed components of the outer membrane besides LOS. Prevention of antibody binding to the organism was not the cause, since the same percentage of bactericidal antibodies to the major outer membrane protein, Protein I, can be absorbed with sialylated organisms as with wild-type organisms. In addition, gonococcal sialylation prevents opsonophagocytosis by antigonococcal antisera. The negative effect of sialic acid on the complement pathway might be the reason for the findings in this study.

Antigens, Bacterial↗
PubMed1991

Studies on the gonococcal IgA1 protease II. Improved methods of enzyme purification and production of monoclonal antibodies to the enzyme.

Two types of extremely active proteases that cleave human IgA1 are produced by pathogenic Neisseria in minute concentrations. To study the antigenicity of these enzymes, a simplified method is described to purify these enzymes from large batch cultures to obtain a sufficient quantity of these IgA1 proteases to study these characteristics. In addition, we describe the production of both rabbit polyclonal and mouse monoclonal antibodies to one of these enzymes. One such monoclonal antibody seemed directed toward the active site of the IgA1 protease and inhibited its enzymatic activity.

Animals↗
PubMed1989

Colony morphology of piliated Neisseria meningitidis.

An association between piliation and colony morphology has not been observed for the meningococcus. We have found that growth of meningococci overnight at 30 degrees C in a candle extinction jar allows observation of distinct colonial phenotypes correlated to the presence or absence of piliation and the expression of opacity-associated proteins. These phenotypes are similar to those observed in gonococci grown overnight at 37 degrees C.

Antibodies, Monoclonal↗
PubMed1989

The construction and characterization of Neisseria gonorrhoeae lacking protein III in its outer membrane.

Protein III (PIII) is a highly conserved, antigenically stable gonococcal outer membrane protein that is closely associated with the major outer membrane protein, protein I (PI). We have previously reported the cloning of the PIII gene. This gene was inserted into the Eco RI site of the runaway plasmid pMOB45. The beta-lactamase (beta la) Bam HI restriction fragment from the gonococcal plasmid pFA3 was inserted at the Xba I site in the PIII gene. The plasmid construct was Hae III methylated and the PIII/beta la insert was excised with Eco RI and used to transform gonococcal strain F62. One beta la+, ampicillin-resistant transformant was isolated and designated 2D. A Western blot of 2D whole cell lysate was probed with affinity-purified polyclonal PIII antisera. No PIII reactivity was detected. Southern blot analysis was performed on F62 and 2D chromosomal DNA that were cut with Eco RI or Cla I. A PIII DNA probe hybridized with fragments 2.2 kb larger in strain 2D than strain F62. This corresponds to the size of the beta la insert. A beta la-specific probe hybridized with the same 2D restriction fragments as above, but did not react with any F62 fragments, confirming that homologous recombination had occurred. There were minimal phenotypic changes between 2D and its parent strain, F62. Chromosomal DNA from 2D was able to transform gonococcal strains F62, UU1, and Pgh 3-2, rendering these PIII-. 2D and other PIII- transformants can now be used to study the role of PIII in gonococcal physiology, metabolism, membrane structure, and pathogenesis. Moreover, we now have organisms from which we can purify gonococcal proteins without PIII contamination.

Ampicillin Resistance↗
PubMed1989

Sequence of the structural gene (rmpM) for the class 4 outer membrane protein of Neisseria meningitidis, homology of the protein to gonococcal protein III and Escherichia coli OmpA, and construction of meningococcal strains that lack class 4 protein.

The structural gene (rmpM) of the class 4 outer membrane protein of Neisseria meningitidis has been cloned and sequenced. The derived amino acid sequence reveals a 218-amino-acid protein following a 22-amino-acid signal peptide. The protein shows 94.2% homology with protein III of Neisseria gonorrhoeae and shares its two potential disulfide loops. The protein also shares limited homology with Escherichia coli OmpA. N. gonorrhoeae protein III has been shown to elicit blocking antibodies that prevent the killing of serum-resistant strains by immune sera (P. A. Rice, H. E. Vayo, M. R. Tam, and M. S. Blake, J. Exp. Med. 164:1735-1748, 1986). The very close homology of meningococcal class 4 protein with gonococcal protein III suggests that meningococcal outer membrane preparations containing class 4 protein may similarly stimulate blocking antibodies. In order to investigate the role of the class 4 protein in the pathogenesis of meningococcal infection, we have used an erythromycin resistance gene in developing two meningococcal strains that lack class 4 protein.

Amino Acid Sequence↗
PubMed1988

Characterization and specificity of antibodies to protein I of Neisseria gonorrhoeae produced by injection with various protein I-adjuvant preparations.

A major goal of gonococcal research is the development of a gonorrheal vaccine. A vaccine candidate is the major outer membrane protein (PI) of the gonococcus, which has limited antigenic variability. Two main subtypes, PIA and PIB, and nine main serotypes have been described. To avoid raising anti-protein III (PIII)-blocking antibodies and limit potential lipooligosaccharide toxicity, PI was chromatographically isolated with minimal PIII contamination (less than 1%) from Pgh 3-2 (PIB), a serum-sensitive gonococcal strain and UU1 (PIA), a serum-resistant gonococcal strain. Alum was used as an adjuvant and the antibodies raised in rabbits did not agglutinate the organisms, were not opsonic, and bactericidal titers were not increased. To present PI in a form mimicking its in vivo disposition, it was inserted into liposomes. The resulting antisera did agglutinate the organism and contained opsonic and bactericidal activity greater than the preimmune sera or alum-generated sera. The PIB liposome antisera also had higher ELISA titers to a synthetic peptide equivalent to an exposed portion of PIB and a higher percentage of antibodies absorbed by whole organisms than the PIB alum antisera. We speculate that when PI is presented in liposomes, the antibodies raised are mainly to surface-exposed epitopes of the protein as opposed to when PI is presented absorbed to alum, where the antibodies are produced mainly to buried epitopes.

Adjuvants, Immunologic↗
PubMed1988

Protein I, a translocatable ion channel from Neisseria gonorrhoeae, selectively inhibits exocytosis from human neutrophils without inhibiting O2- generation.

Protein I, the major outer membrane protein of Neisseria gonorrhoeae, is a voltage-dependent anion channel which can translocate from the gonococcus into human cells. Since granule exocytosis from neutrophils is regulated by ion fluxes, we examined the effect of protein I on neutrophil activation. Pretreatment with protein I (250 nM) impaired degranulation from neutrophils: beta-glucuronidase release decreased to 27 +/- 6% S.E. of cells treated with N-f-Met-Leu-Phe (fMLP, 0.1 microM) and to 13 +/- 4% of cells treated with leukotriene B4 (LTB4, 0.1 microM); lysozyme release decreased to 52 +/- 17% of fMLP-treated cells and 22 +/- 9% of LTB4-treated cells. Morphometric analysis was consistent: control neutrophils increased their surface membrane after fMLP (43.3 +/- 5.6 microns relative perimeter versus 71.4 +/- 3.7 microns) while protein I-treated neutrophils did not (29.4 +/- 2 (S.E.) microns relative perimeter versus 34 +/- 4 microns). Enzyme release after exposure to phorbol myristate acetate was not affected (lysozyme: 86 +/- 27% of control). Cell/cell aggregation in response to fMLP was inhibited by treatment with protein I. However, generation of O2 was not affected. Protein I altered the surface membrane potential (Oxonol V): protein I evoked a transient membrane hyperpolarization which was not inhibited by furosemide. After exposure to fMLP, protein I-treated neutrophils underwent a furosemide-sensitive hyperpolarization rather than the usual depolarization. Protein I did not alter increments in [Ca]i (Fura-2) stimulated by fMLP (460 +/- 99 nM (S.E.) versus 377 +/- 44 nM) nor decrements in [pH]i (7.22 +/- 0.04 S.E. versus 7.22 +/- 0.02, bis-(carboxy-ethyl)carboxyfluorescein). The results suggest that degranulation and O2 generation have separate ionic requirements and that protein I interrupts the activation sequence proximal to activation of protein kinase C.

Benzofurans↗
PubMed1987

The DNA sequence of the structural gene of gonococcal protein III and the flanking region containing a repetitive sequence. Homology of protein III with enterobacterial OmpA proteins.

The insert of a lambda gt11 clone expressing gonococcal protein III was sequenced. The deduced amino acid sequence showed a coding frame of 236 amino acids with a typical 22-amino-acid signal peptide, followed by the known NH2-terminal sequence of PIII. The mature protein has a molecular weight of 23,298. It was found that PIII had extensive and very striking homology to the carboxy-terminal portion of enterobacterial OmpA proteins. The homology encompasses the OmpA domain that is believed to be located in the periplasmic space. If the disposition of PIII across the OM is analogous, then the surface-exposed domain consists of less than 40 amino acids. These include a potential 15-amino-acid disulfide loop, a feature not found in OmpA proteins. Hybridization studies with the sequenced insert indicated that it contained a repetitive sequence that occurred at least 20 times in the genome. By additional hybridization studies the area containing the repetitive sequence was narrowed to a region of 43 bp. This region contained an exact copy of the consensus sequence of a 26-bp repetitive sequence recently described. An analogous sequence recurs in an inverted orientation 53 bp downstream.

Amino Acid Sequence↗
PubMed1987

Gonococcal protein III. Purification and chemical characterization of the protein, and the DNA sequence of the structural gene.

We have purified protein III (PIII) from several strains of gonococcus by extractions with Zwittergent 3,14 followed by cation exchange chromatography and gel filtration. The pI of 8.6 determined by isoelectric focusing was in keeping with the high content of basic amino acids found. PIII from two strains had identical N-terminal sequence. In contrast to PIII in vivo, purified PIII was highly susceptible to proteolysis. Rabbit antibodies raised with purified antigen reacted with PIII of all strains tested as well as meningococcal protein 4. Furthermore, intact gonococci or meningococci could absorb 80% of antibodies raised by immunization with the purified PIII. The structural gene of PIII was cloned and the DNA sequenced. The predicted primary structure is strongly homologous to the OmpA proteins of Enterobacteria.

Amino Acid Sequence↗
PubMed1987

Mechanisms of stable serum resistance of Neisseria gonorrhoeae.

Neisseria gonorrhoeae that resist complement-dependent killing by normal human serum (NHS) are sometimes killed by immune convalescent sera from patients recovering from disseminated gonococcal infection (DGI). In these studies, killing by immune serum was prevented or blocked by immunoglobulin G (IgG) or F(ab')2 isolated from NHS. Purified human IgG antibodies directed against gonococcal protein III, contained most of the blocking activity in IgG. In addition, immune convalescent DGI serum, which did not exhibit bactericidal activity, was restored to killing by selective immunodepletion of protein III antibodies. Blocking IgG or F(ab')2 prepared from IgG, partially inhibited binding of bactericidal antibody to N. gonorrhoeae. Also, binding of a monoclonal antibody recognizing N. gonorrhoeae outer membrane protein PIII was almost completely inhibited by blocking F(ab')2. Presensitization of N. gonorrhoeae with increasing concentrations of blocking IgG or F(ab')2 before incubation with bactericidal antibody and an antibody free source of complement, increased consumption and deposition of the third component of human complement (C3) and the ninth component of complement (C9) but inhibited killing in dose-related fashion.

Antibodies, Bacterial↗
PubMed1987

Porin protein of Neisseria gonorrhoeae: cloning and gene structure.

The outer membrane porin molecule of Neisseria gonorrhoeae is known as protein I (PI). Among different strains of gonococci there is variability of PI, and two main classes, PIA and PIB, have been recognized. A lambda gt11 bank of gonococcal DNA was screened using monoclonal antibodies directed to a PIB-type porin molecule of N. gonorrhoeae, and three immunoreactive clones were isolated. DNA sequence analysis indicated that each contained only portions of the PI structural gene, but that together they contained the complete gene, and its structure was determined. The DNA sequence predicts a protein of 348 amino acids with a typical 19 amino acid signal peptide. The PI protein resembles Escherichia coli porins in size, lack of long hydrophobic sequences, and absence of cysteine residues. Sequence homologies between PI and the E. coli porins were found, particularly in the 100 N-terminal and the 110 C-terminal amino acids. In addition to the coding sequence of PI, the complementary strand contains a large open reading frame. At the 3' end of the PI gene, immediately following an inverted repeat (probably the transcription terminator), the clone contains an unusual sequence consisting of 31 perfect repeats of the heptamer CTGTTTT. Hybridization analysis suggests that there is a single structural gene for PI and that it is homologous to the gene found in a PIA-bearing strain of gonococcus.

Amino Acid Sequence↗
PubMed1987

Probing the surface of Neisseria gonorrhoeae: simultaneous localization of protein I and H.8 antigens.

Gonococcal outer membrane protein I and the neisserial antigen H.8 are being investigated for inclusion in a gonococcal vaccine. To determine the distribution of immunoaccessible protein I and H.8 molecules on the surface of viable gonococci and to approximate the accessibility of these antigens to vaccine-elicited antibodies, immunologic probes composed of protein I- and H.8-specific antibodies linked to gold spheres were developed. When whole gonococci were exposed to the protein I and H.8 immunologic probes and examined by transmission electron microscopy, gold spheres clearly marked the surface of some of the gonococci, but not the surface of other gonococci from the same culture. The immunologic accessibility of gonococcal protein I or neisserial H.8 varied among gonococci. This diversity may affect the efficacy of a vaccine composed of these surface antigens.

Antibodies, Monoclonal↗
PubMed1986

Immunoglobulin G antibodies directed against protein III block killing of serum-resistant Neisseria gonorrhoeae by immune serum.

Neisseria gonorrhoeae that resist complement-dependent killing by normal human serum (NHS) are sometimes killed by immune convalescent serum from patients recovering from disseminated gonococcal infection (DGI). In these studies, killing by immune serum was prevented or blocked by IgG isolated from NHS. Purified human IgG antibodies directed against gonococcal protein III, an antigenically conserved outer membrane protein, contained most of the blocking activity in IgG. Antibodies specific for gonococcal porin (protein I), the major outer membrane protein, displayed no blocking function. In separate experiments, immune convalescent DGI serum which did not exhibit bactericidal activity was restored to killing by selective depletion of protein III antibodies by immunoabsorption. These studies indicate that protein III antibodies in normal and immune human serum play a role in serum resistance of N. gonorrhoeae.

Antibodies, Bacterial↗