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Copy number of pilus gene clusters in Haemophilus influenzae and variation in the hifE pilin gene.

ABSTRACT: Brazilian purpuric fever (BPF)-associated Haemophilus influenzae biogroup aegyptius strain F3031 contains two identical copies of a five gene cluster (hifA to hifE) encoding pili similar to well-characterized Hif fimbriae of H. influenzae type b. HifE, the putative pilus tip adhesin of F3031, shares only 40% amino acid sequence similarity with the same molecule from type b strains, whereas the other four proteins have 75 to 95% identity. To determine whether pilus cluster duplication and the hifE(F3031) allele were special features of BPF-associated bacteria, we analyzed a collection of H. influenzae strains by PCR with hifA- and hifE-specific oligonucleotides, by Southern hybridization with a hifC gene probe, and by nucleotide sequencing. The presence of two pilus clusters was limited to some H. influenzae biogroup aegyptius strains. The hifE(F3031) allele was limited to H. influenzae biogroup aegyptius. Two strains contained one copy of hifE(F3031) and one copy of a variant hifE allele. We determined the nucleotide sequences of four hifE genes from H. influenzae biogroup aegyptius and H. influenzae capsule serotypes a and c. The predicted proteins produced by these genes demonstrated only 35 to 70% identity to the three published HifE proteins from nontypeable H. influenzae, serotype b, and BPF strains. The C-terminal third of the molecules implicated in chaperone binding was the most highly conserved region. Three conserved domains in the otherwise highly variable N-terminal putative receptor-binding region of HifE were similar to conserved portions in the N terminus of Neisseria pilus adhesin PilC. We concluded that two pilus clusters and hifE(F3031) were not specific for BPF-causing H. influenzae, and we also identified portions of HifE possibly involved in binding mammalian cell receptors.

SUBMITTER: Read TD

PROVIDER: S-EPMC108097 | biostudies-literature | 1998 Apr

REPOSITORIES: biostudies-literature

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Copy number of pilus gene clusters in Haemophilus influenzae and variation in the hifE pilin gene.

Read T D TD Satola S W SW Opdyke J A JA Farley M M MM

Infection and immunity 19980401 4

Brazilian purpuric fever (BPF)-associated Haemophilus influenzae biogroup aegyptius strain F3031 contains two identical copies of a five gene cluster (hifA to hifE) encoding pili similar to well-characterized Hif fimbriae of H. influenzae type b. HifE, the putative pilus tip adhesin of F3031, shares only 40% amino acid sequence similarity with the same molecule from type b strains, whereas the other four proteins have 75 to 95% identity. To determine whether pilus cluster duplication and the hif ...[more]

PMID: 9529090

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Project description:Adherence of Haemophilus influenzae to epithelial cells plays a central role in colonization and is the first step in infection with this organism. Pili, which are large polymorphic surface proteins, have been shown to mediate the binding of H. influenzae to cells of the human respiratory tract. Earlier experiments have demonstrated that the major epitopes of H. influenzae pili are highly conformational and immunologically heterogenous; their subunit pilins are, however, immunologically homogenous. To define the extent of structural variation in pilins, which polymerize to form pili, the pilin genes (hifA) of 26 type a to f and 16 nontypeable strains of H. influenzae were amplified by PCR and subjected to restriction fragment length polymorphism (RFLP) analysis with AluI and RsaI. Six different RFLP patterns were identified. Four further RFLP patterns were identified from published hifA sequences from five nontypeable H. influenzae strains. Two patterns contained only nontypeable isolates; one of these contained H. influenzae biotype aegyptius strains F3031 and F3037. Another pattern contained predominantly H. influenzae type f strains. All other patterns were displayed by a variety of capsular and noncapsular types. Sequence analysis of selected hifA genes confirmed the 10 RFLP patterns and showed strong identity among representatives displaying the same RFLP patterns. In addition, the immunologic reactivity of pili with antipilus antisera correlated with the groupings of strains based on hifA RFLP patterns. Those strains that show greater reactivity with antiserum directed against H. influenzae type b strain M43 pili tend to fall into one RFLP pattern (pattern 3); while those strains that show equal or greater reactivity with antiserum directed against H. influenzae type b strain Eagan pili tend to fall in a different RFLP pattern (pattern 1). Sequence analysis of representative HifA pilins from typeable and nontypeable H. influenzae identified several highly conserved regions that play a role in bacterial pilus assembly and other regions with considerable amino acid heterogeneity. These regions of HifA amino acid sequence heterogeneity may explain the immunologic diversity seen in intact pili.

Project description:A subset of nontypeable Haemophilus influenzae (NTHI) biotype IV isolates from the human genital tract or from infected newborn infants forms a cryptic genospecies characterized by, among other features, the presence of peritrichous pili. The objective of this study was to determine the similarity of these pili to hemagglutinating, HifA- and HifE-containing pili expressed by respiratory H. influenzae isolates. For this analysis, the presence of hifA and hifE and their gene products in NTHI biotype IV strains was assessed, the binding of H. influenzae biotype IV strains to human epithelial cells was characterized, possible genital tissue tropism of these isolates was explored, and the role of HifA- and HifE-possessing pili in the adhesion of NTHI biotype IV strains to human epithelial cells was determined. None of the six biotype IV NTHI isolates tested agglutinated human red blood cells, nor could they be enriched for hemagglutinating variants. Although hifA, which encodes the major structural subunit of hemagglutinating pili, and hifE, which encodes the tip adhesin of hemagglutinating pili, were detected by PCR from six and five, respectively, of the six biotype IV strains tested, neither HifA nor HifE (the gene products of hifA and hifE) were detected in any of these strains by Western blot analysis using antisera that recognize HifA and HifE of respiratory strains. Transmission electron microscopy showed no surface pili on the two biotype IV H. influenzae isolates examined; strain 4162 containing an insertional mutation in hifA also showed no surface pili, whereas strain 1595 containing an insertional mutation in hifB showed pilus-like structures that were shorter and thicker than hemagglutinating pili of the respiratory strains AAr176 and M43. In enzyme-linked immunosorbent assays, biotype IV strains adhered to 16HBE14o(-) and HEp-2 cells of respiratory origin as well as to ME180 and HeLa cells of genital origin. This adherence was not pilus specific, however, as GM-1, a known pilus receptor analog, did not inhibit binding of biotype IV strains to ME180, HEp-2, or HeLa cells, and GM-1 inhibition of binding to 16HBE14o(-) cells did not correlate with the presence of hifE. While both nonpiliated variants and hifA and hifB (encoding the pilus chaperone) mutants of respiratory strain AAr176 showed reduced binding (64 to 87% of that of piliated AAr176) to 16HBE14o(-) and ME180 cells, hifA and hifB mutants of the biotype IV strains showed minimal reduction in binding to these cell lines (91 to 98% of that of wild-type strains). Thus, although biotype IV H. influenzae isolates of the cryptic genospecies possess the genes that code for HifA- and HifE-containing hemagglutinating pili, epithelial cell adherence exhibited by these strains is not mediated by expression of hemagglutinating pili.

Dataset Information

Copy number of pilus gene clusters in Haemophilus influenzae and variation in the hifE pilin gene.

Publications

Copy number of pilus gene clusters in Haemophilus influenzae and variation in the hifE pilin gene.

Similar Datasets

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