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P F Sparling

Publications and source records attributed to P F Sparling.

At least 19 recordsLinked to original sources
PubMed1992

Antibodies to N-terminal peptides of gonococcal porin are bactericidal when gonococcal lipopolysaccharide is not sialylated.

Six synthetic 25-mer peptides corresponding to certain presumed surface-exposed regions of gonococcal porin protein I (PI) were made from strains FA19 (PIA) and MS11 (PIB). Four peptides were immunogenic in rabbits. Affinity-purified antisera against both PIA and PIB N-terminal peptides were bactericidal for homologous gonococci and many heterologous PI serovars. However, sialylation of gonococcal lipopolysaccharide (LPS) by growth of gonococci in the presence of cytidine monophosphate-neuraminic acid (CMP-NANA) abrogated the bactericidal activity of these antisera. Binding of anti-PI monoclonal antibodies to whole gonococci was reduced two- to fourfold by sialylation of LPS, suggesting that sialylation may inhibit bactericidal activity by masking porin epitopes. However, binding of anti-PII (Opa) monoclonal antibodies was not inhibited, yet complement-mediated killing was inhibited by sialylated LPS. Binding of complement components C3 and C9 was inhibited in the presence of either anti-PI or anti-PII monoclonals when gonococci were grown in the presence of CMP-NANA. Thus sialylation inhibited both anti-PI antibody binding and complement deposition, with a resultant decrease in bactericidal activity.

Amino Acid Sequence↗
PubMed1992

Gonococcal transferrin-binding protein 1 is required for transferrin utilization and is homologous to TonB-dependent outer membrane receptors.

The pathogenic Neisseria species are capable of utilizing transferrin as their sole source of iron. A neisserial transferrin receptor has been identified and its characteristics defined; however, the biochemical identities of proteins which are required for transferrin receptor function have not yet been determined. We identified two iron-repressible transferrin-binding proteins in Neisseria gonorrhoeae, TBP1 and TBP2. Two approaches were taken to clone genes required for gonococcal transferrin receptor function. First, polyclonal antiserum raised against TBP1 was used to identify clones expressing TBP1 epitopes. Second, a wild-type gene copy was cloned that repaired the defect in a transferrin receptor function (trf) mutant. The clones obtained by these two approaches were shown to overlap by DNA sequencing. Transposon mutagenesis of both clones and recombination of mutagenized fragments into the gonococcal chromosome generated mutants that showed reduced binding of transferrin to whole cells and that were incapable of growth on transferrin. No TBP1 was produced in these mutants, but TBP2 expression was normal. The DNA sequence of the gene encoding gonococcal TBP1 (tbpA) predicted a protein sequence homologous to the Escherichia coli and Pseudomonas putida TonB-dependent outer membrane receptors. Thus, both the function and the predicted protein sequence of TBP1 were consistent with this protein serving as a transferrin receptor.

Amino Acid Sequence↗
PubMed1991

Species-specific uptake of DNA by gonococci is mediated by a 10-base-pair sequence.

Piliated Neisseria gonorrhoeae are known to be transformed less readily if transforming DNA competes with DNA containing the 10-bp sequence GCCGTCTGAA. It has been postulated that the 10-bp sequence is a recognition sequence which is required for efficient DNA uptake. We show that the presence of various forms of this 10-bp sequence results in increased uptake of double-stranded DNA into a DNase-resistant state and allows genetic transformation by an otherwise nontransformable plasmid.

Base Sequence↗
PubMed1990

Construction of isogenic gonococci with variable porin structure: effects on susceptibility to human serum and antibiotics.

Protein I (PI) is the most abundant protein on the gonococcal cell surface and besides its porin function it may have important properties contributing to pathogenicity. By allelic exchange using cloned PI genes from FA19 (PIA) and MS11 (PIB) and a selectable marker introduced closely downstream of these genes, we constructed sets of isogenic gonococcal strains that differ only in their PI gene. Analysis revealed that PI has a major effect on stable resistance to normal human serum, and a slight effect on low-level resistance to antibiotics. All PIA/B hybrids were hypersusceptible to serum, suggesting a possible explanation for why such hybrids do not occur in nature.

Alleles↗
PubMed1990

Genetic evidence that Neisseria gonorrhoeae produces specific receptors for transferrin and lactoferrin.

Transferrin (TF) and lactoferrin (LF) are probably the major sources of iron (Fe) for Neisseria gonorrhoeae in vivo. We isolated mutants of N. gonorrhoeae FA19 that were unable to grow with Fe bound to either TF (TF-) or LF (LF-) or to both TF and LF ([TF LF]-). The amount of Fe internalized by each of the mutants was reduced to background levels from the relevant iron source(s). The wild-type parent strain exhibited saturable specific binding of TF and LF; receptor activity was induced by Fe starvation. The TF(-)-specific or LF(-)-specific mutants were almost completely lacking in receptor activity for TF or LF, respectively, whereas the [TF LF]- mutants bound both TF and LF as well as the wild-type strain. All mutants utilized citrate and heme normally as Fe sources. These results demonstrate that ability to bind TF or LF is essential for gonococci to scavenge appreciable amounts of Fe from these sources in vitro. In addition, the TF and LF Fe acquisition pathways are linked by the mutual use of a nonreceptor gene product that is essential to Fe scavenging from both of these sources; this gene product is not required for Fe acquisition from other sources.

Binding, Competitive↗
PubMed1990

Gonococci are survivors.

Gonococci are capable of prolonged survival in untreated infection, and frequently reinfect persons with repeated and recent infection, despite considerable mucosal and systemic immune response to infection. Multiple mechanisms help to explain how this is achieved, including variations in surface antigen expression; production of an extracellular IgA protease; employment of antigens that preferentially stimulate host production of antibodies that block the killing activity of other antibodies; masking of critical epitopes by chemical modification of surface structures; molecular mimicry of host antigens; shedding of antigens in the form of outer membrane blebs; and, subverting certain nonimmunological antimicrobial defenses to the use of the bacterium. Moreover, gonococci are capable of considerable phenotypic adaptation to changing environmental conditions in vivo. This paper briefly reviews these concepts.

Adaptation, Physiological↗
PubMed1979

Transformation-derived Neisseria gonorrhoeae plasmids with altered structure and function.

Plasmid deoxyribonucleic acid from Neisseria gonorrhoeae containing a 7.1-kilobase (kb) (4.7-megadalton) penicillinase (Pcr) plasmid transformed homogenic gonococci to penicillinase production at a low frequency. About 25% of the penicillinase-producing gonococcal transformants contained Pcr plasmids which were either larger or smaller than the 7.1 kb donor plasmid; these Pcr plasmids varied in size from 3.45 to 42 kb. Some of these altered plasmids differed from the donor plasmid in stability or in frequency of mobilization by a 36-kb (24-megadalton) conjugative plasmid. A restriction endonuclease cleavage map of the 7.1-kilobase Pcr plasmid and several of the smaller deleted plasmids was constructed. The most common size of altered Pcr plasmid was 5.1 kb (3.4 megadaltons). A Pcr plasmid isolated from a gonococcus in London, England, was identical with these 5.1-kb transformant plasmids in both size and restriction endonuclease cleavage profiles, suggesting that the 5.1-kb Pcr plasmid could have arisen from a 7.1-kb Pcr plasmid by a transformation-associated deletion in nature.

Conjugation, Genetic↗
PubMed1978

Familial deficiency of the seventh component of complement associated with recurrent bacteremic infections due to Neisseria.

The serum of a 29-year old woman with a recent episode of disseminated gonococcal infection and a history of meningococcal meningitis and arthritis as a child was found to lack serum hemolytic complement activity. The seventh component of complement (C7) was not detected by functional or immunochemical assays, whereas other components were normal by hemolytic and immunochemical assessment. Her fresh serum lacked complement-mediated bactericidal activity against Neisseria gonorrhoeae, but the addition of fresh normal serum or purified C7 restored bactericidal activity as well as hemolytic activity. The absence of functional C7 activity could not be accounted for on the basis of an inhibitor. Opsonization and generation of chemotactic activity functioned normally. Complete absence of C7 was also found in one sibling who had the clinical syndrome of meningococcal meningitis and arthritis as a child and in this sibling's clinically well eight-year-old son. HLA histocompatibility typing of the family members did not demonstrate evidence for genetic linkage of C7 deficiency with the major histocompatibility loci. This report represents the first cases of C7 deficiency associated with infectious complications and suggests that bactericidal activity may be important in host defense against bacteremic neisseria infections.

Adult↗
PubMed1978

Conjugative plasmids in Neisseria gonorrhoeae.

A conjugation system initially discovered in beta-lactamase-producing gonococci mobilized small non-selftransmissible R plasmids encoding beta-lactamase (penicillinase) production into other gonococci, Neisseria, and Escherichia coli. This conjugation system was mediated by a separate selftransmissible plasmid of 23.9 X 10(6) daltons, pFA2. Conjugative plasmids capable of mobilizing R plasmids were also found in nearly 8% of the non-penicillinase-producing gonococci. These were similar to pFA2 in size, buoyant density, and restriction endonuclease digest patterns but were less efficient than pFA2 in mobilization of the penicillinase plasmid pFA3. The presence of conjugative plasmids in gonococci isolated before the appearance of penicillinase-producing strains indicates that a conjugation system for plasmid transfer predated the appearance of R plasmids in gonococci.

Centrifugation, Density Gradient↗
PubMed1978

Cell envelope alterations in antibiotic-sensitive and-resistant strains of Neisseria gonorrhoeae.

The cell envelopes of antibiotic-resistant and -sensitive isogenic strains of Neisseria gonorrhoeae were analyzed to determine whether acquisition of genetic loci for altered antibiotic sensitivity was accompanied by alterations in cell envelope composition. No differences in the composition of phospholipids and lipopolysaccharides were noted. Acquisition of mtr-2, which results in low-level, nonspecific increased resistance to multiple antibiotics, dyes, and detergents, was accompanied by a sevenfold increase in the amount of a minor, 52,000-molecular-weight outer membrane protein and a 32% increase in the extent of peptidoglycan cross-linking. Subsequent addition of the nonspecific hypersensitivity loci env-1 or env-2 to a strain carrying mtr-2 resulted in reversal of the phenotypic resistance determined by mtr-2 and marked reduction in both the amount of the 52,000-molecular-weight outer membrane protein and the extent of peptidoglycan cross-linking. Introduction of penB2, which results in a fourfold increase in resistance to penicillin and tetracycline, was accompanied by the disappearance of the principal outer membrane protein of the wild-type strain (molecular weight, 36,900) and the appearance of a new species of the principal outer membrane protein (molecular weight, 39,400) in the transformant.

Anti-Bacterial Agents↗
PubMed1977

Conjugal transfer of the gonococcal penicillinase plasmid.

Certain gonococci, which heretofore have lacked a conjugal mating system, can sexually transfer a small plasmid (4.5 x 10)6) daltons) which carries the gene for beta-lactamase production. Frequencies of conjugal transfer were similar into diverse recipients (other gonococci, Neisseria flava, and Escherichia coli), which suggests that gonococci may transfer the plasmid promiscuously in nature.

Conjugation, Genetic↗
PubMed1977

Penicillin sensitivity and serum resistance are independent attributes of strains of Neisseria gonorrhoeae causing disseminated gonococcal infection.

We have determined that isolates of Neisseria gonorrhoeae from patients with disseminated gonococcal infection (DGI) are different from randomly collected isolates from patients with uncomplicated (local) disease. Our comparison was based on the six phenotypic properties of: sensitivity to penicillin (PenS), erythromycin, and streptomycin; resistance to the bactericidal effects of pooled human sera; requirements for arginine, hypoxanthine, and uracil (AHU-); and sensitivity to toxic agar. Although the marked association among these traits made analysis difficult, several factors independently related to virulence were defined. The DGI isolates were significnatly more PenS and resistant to serum, even when the other variables were held constant. An apparent correlation between AHU- auxotype and virulence was shown to be due to the PenS property of most AHU- isolates. Thus, certain mutations to antibiotic resistance as well as susceptibility to sera, may result in loss of virulence in the gonococcus, perhaps through alteration of cell envelope structure.

Agar↗