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Infection and Immunity, October 1998, p. 4788-4796, Vol. 66, No. 10
Departments of Pediatrics and Communicable
Diseases1 and
Epidemiology,2 University of
Michigan, Ann Arbor, Michigan 48109-0244
Received 4 March 1998/Returned for modification 4 May 1998/Accepted 24 July 1998
Two proteins, HifD and HifE, have been identified as structural
components of Haemophilus influenzae pili. Both are
localized at the pilus tip, and HifE appears to mediate pilus adherence to host cells. In this study we examined the immunologic and structural diversity of these pilus subunits among type b H. influenzae (Hib) and nontypeable H. influenzae (NTHI)
strains. Western immunoblot analysis revealed that antibodies directed
against the C terminus of HifD and HifE from Hib strain Eagan bound to
HifD and HifE proteins, respectively, of all piliated Hib and NTHI
strains tested. Whole-cell enzyme-linked immunosorbent assays showed
that antibodies specific for native HifD or HifE of strain Eagan also
bound to all piliated Hib strains but did not bind to the piliated NTHI strains. Antibodies against HifE of strain Eagan inhibited the binding
of Hib to human erythrocytes but did not inhibit the binding of NTHI
strains. Restriction fragment length polymorphism (RFLP) analysis was
used to determine strain-to-strain structural differences within
hifD and hifE genes, either by PCR or by
nucleotide sequence analysis. DNA and derived amino acid sequence
analyses of HifD and HifE confirmed the uniqueness of the RFLP types.
The hifD and hifE genes of all type b strains
showed identical restriction patterns. Analysis of hifD and
hifE genes from the NTHI strains, however, revealed seven
unique RFLP patterns, suggesting that these genes encode proteins with
diverse primary structures. These results indicate that HifD and HifE
are immunologically and structurally similar among the Hib strains but
vary among the NTHI strains.
0019-9567/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Immunologic and Structural Relationships of the
Minor Pilus Subunits among Haemophilus influenzae
Isolates

*
Corresponding author. Mailing address: F6854 Mott
Children's Hospital, Box 0244, University of Michigan Medical Center,
Ann Arbor, MI 48109-0244. Phone: (734) 763-2440. Fax: (734) 763-7359. E-mail: Gilsdorf{at}umich.edu.
Present address: The Institute of Biosciences and Technology, Texas
A&M University, Houston, TX 77030-3303.
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