Neisseria meningitidis C114 contains silent, truncated pilin genes that are homologous to Neisseria gonorrhoeae pil sequences

Abstract

Neisseria meningitidis pili can be classified into two groups: those (referred to here as class I pili) which are similar to gonococcal pili in that they react with monoclonal antibody SM1 and those that are dissimilar to gonococcal pili in that they lack the SM1-reactive epitope (class II pili). Pilus expression in N. meningitidis C114, a class II pilus-producing isolate, was investigated. The sole genomic segment of this strain that bore extensive homology with the pilE locus of Neisseria gonorrhoeae P9 was cloned in Escherichia coli. The production of the pilus structural subunit (pilin) from this meningococcal segment could not be detected by immunological and coupled in vitro transcription-translation analyses. Nucleotide sequence analysis revealed the presence in the C114 genome of two variant, tandemly arranged pilin genes (copies 1 and 2). Copies 1 and 2 are partial pilin genes that constitute part of a silent meningococcal pilin gene (pil gene) region, designated pilS. Both copies are truncated, corresponding to variable domains of the gonococcal pilE gene but lacking homologous N-terminal coding sequences. Located within sequences surrounding copies 1 and 2 were several classes of repeated elements that are associated with pil loci in N. gonorrhoeae.

Identification of Epitopes Recognized by Monoclonal Antibodies SM1 and SM2 Which React with All Pili of Neisseria gonorrhoeae but Which Differentiate between Two Structural Classes of Pili Expressed by Neisseria meningitidis and the Distribution of Their Encoding Sequences in the Genomes of Neisseria spp.

“…It is likely from hybridization and sequence data that the structural gene for class I1 pilin will possess only limited nucleotide sequence homology to the class I pilE gene (Perry et al, 1988). The current studies reveal that differences between the two classes of meningococcal pilin are likely to be extensive and not simply the result of the deletion of a limited number of amino acids in a single domain.…”

“…residues 54-114) in which amino acid substitutions occur, and a hypervariable (HV) region at the carboxy-terminus in which insertions and deletions of up to four amino acids occur Nicolson et al, 1987 b ;Swanson et al, 1987). Sequence analysis of cloned class I meningococcal pilE (Potts & Saunders, 1988) and pilS (Perry et al, 1988) loci suggest that pilins produced by most strains of N. meningitidis also conform to this model, with complete homology between amino acids 1-55. In each case the sequence between residues 49 and 53 is preserved and the pili react with antibody SM1.…”

“…No background hybridization was observed with DNA from strain C114 (Fig. 4, A), which expresses class I1 pili and possesses truncated silent class I pilin sequences that do not include the coding sequence for the SM1-reactive epitope (Perry et al, , 1988. Meningococcal strain C311, which expressed class I pili, showed strong hybridization with the oligonucleotide PS1, while a non-piliated variant derived from it gave a much weaker signal (Fig.…”

“…Other strains produce pilins that fail to react with either mAb but react with polyclonal antisera raised against gonococcal pili to reveal pilins with apparent M , in the range 13000-16000 Perry et al, 1987a). These two types of meningococcal pili have been given a variety of designations by different authors, namely group 1 and group 2 , SMl-reactive and SM2-nonreactive (Achtman et al, 1988) and class I and class I1 (Perry et al, 1988); the last has subsequently been adopted as the recognized nomenclature (Hitchcock, 1989).…”

“…The presence of DNA sequences homologous to the entire structural gene for gonococcal pilin (pilE) appears to be limited to the pathogenic members of the genus Neisseria (Ah0 et al, 1987). Despite failing to encode class I pili, the chromosomes of two independently isolated class I1 pilus-producing meningococci have been shown to contain silent pi1 sequences that are homologous to regions of the central semivariable (SV) and carboxy-terminal hypervariable (HV) coding portions of the gonococcalpilEpilin structural gene (Ah0 & Cannon, 1988 ;Perry et al, 1988). mAbs SM1 and SM2 have been used in several studies of meningococcal piliation to detect expression, to differentiate between the two classes of pili and to examine pilus antigenic variation Olafson et al, 1985;Achtman et al, 1988;Potts & Saunders, 1988).…”