Infect Immun, February 1998, p. 656-663, Vol. 66, No. 2
0019-9567/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Department of Pediatrics and Communicable
Diseases,
Received 29 August 1997/Returned for modification 28 October
1997/Accepted 26 November 1997
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.
*
Corresponding author. Mailing address: Department of
Pediatrics and Communicable Diseases, The University of Michigan, 109 S. Observatory St., SPH I/Rm. 2030, Ann Arbor, MI 48109-2029. Phone:
(313) 647-3943. Fax: (313) 764-3192. E-mail:
dclemans{at}sph.umich.edu.
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