Summary auto-generated
This study identified the epitopes recognized by monoclonal antibodies SM1 and SM2, which react with pili from Neisseria gonorrhoeae but differentiate between two structural classes of Neisseria meningitidis pili. Using synthetic peptide synthesis, researchers determined that SM1 recognizes a linear pentapeptide epitope (EYYLN, residues 49-53) in conserved regions of pilin, while SM2 recognizes a conformational epitope around cysteine residue 120 at the carboxy-terminus. DNA hybridization analysis using oligonucleotide probe PS1 and a carboxy-terminal pilin gene probe revealed that all N. gonorrhoeae strains and N. meningitidis class I pilus producers harbored sequences encoding the SM1 epitope. Class II pilus-producing meningococci showed variable reactivity with the PS1 probe, suggesting differences in silent pilin gene sequences. Notably, commensal Neisseria species and unrelated bacteria failed to react with SM1 antibody or DNA probes, confirming that 'gonococcal' pilin sequences are restricted to pathogenic neisseriae. These findings establish the molecular basis for distinguishing meningococcal pilus classes and clarify the distribution of pilin genes across Neisseria species.
Key findings
- SM1 monoclonal antibody recognizes a linear pentapeptide epitope EYYLN (residues 49-53) in the conserved region of gonococcal pilin
- SM2 antibody recognizes a conformational epitope in the carboxy-terminal region around cysteine residue 120
- All N. gonorrhoeae and N. meningitidis class I pilus producers contain DNA sequences encoding the SM1 epitope, while class II meningococci show variable hybridization patterns
- Possession of 'gonococcal' pilin sequences is limited to pathogenic Neisseria species, with commensal species and unrelated bacteria lacking these sequences
This summary was generated automatically from the article PDF and is not part of the original publication. Refer to the PDF for the authoritative text.
Abstract
Summary: The pili expressed by all isolates of Neisseria gonorrhoeae react with two monoclonal antibodies, SM1 and SM2. In contrast, although many isolates of Neisseria meningitidis also express pili (class I) which react with antibodies SM1 and SM2, a proportion express pili (class II) which fail to react. In order to define the epitopes recognized by these antibodies, a series of overlapping peptides corresponding to the amino acid sequence of conserved regions of gonococcal pili have been synthesized. The minimum epitope recognized by antibody SM1 was found to comprise a linear peptide EYYLN, corresponding to residues 49-53 of mature pilin. In contrast, antibody SM2 reacted with a number of peptides from around the cysteine residue (Cys 1) at position 120, suggesting that an extended region may contribute to a conformational epitope recognized by this antibody in the native protein. The identification of the two epitopes defines structural differences between the classes of pili expessed by meningococci. In order to determine the distribution of pilin gene sequences in Neisseria we used as hybridization probes an oligonucleotide (PS1) with the sequence 5'-GAGTATTACCTGAATCA-3' which spans the coding region for the SM1 epitope, and a fragment of the 3' end of the gonococcal pilE gene which contains conserved sequences flanking the two Cys codons and encodes the SM2 epitope. All strains of N. gonorrhoeae and N. meningitidis tested, regardless of piliation phenotype, harboured DNA sequences homologous to those encoding the carboxy-terminus of meningococcal class I pilin. Furthermore, all gonococci and all meningocococci producing class I pili hybridized with oligonucleotide probe PS1. Non-reverting non-piliated derivatives of previously class I pilus-producing strains showed reduced hybridization signals with this probe, but nevertheless retained sequences homologous to the coding sequence for the SM1 epitope. However, meningococci producing class II pili could be divided into two groups on the basis of their reaction with the PS1 probe: half the strains tested failed to react, which is consistent with our previous analysis of silent class I pilin sequences; the remainder reacted (relatively weakly) with the probe, suggesting that the silent pil sequences in these strains extend further towards the 5' end of the pilin gene than in strains studied previously. Some strains of Neisseria lactamica reacted weakly with both types of probe but failed to produce SM1-reactive pili. In contrast,