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Infection and Immunity, January 1999, p. 187-192, Vol. 67, No. 1
Departments of
Pediatrics1 and
Pathology,3 University of Texas Medical
Branch, Galveston, Texas, and
Otological Research Laboratories,
Department of Otolaryngology, Ohio State University, Columbus,
Ohio2
Received 19 August 1998/Returned for modification 17 September
1998/Accepted 8 October 1998
Respiratory syncytial virus (RSV) infection is known to predispose
children to otitis media and sinusitis due to bacteria such as
nontypeable Haemophilus influenzae (NTHI). In this study, we investigated the role of NTHI surface outer membrane protein P5-homologous fimbriae (P5-fimbriae) in attachment to RSV-exposed A549
epithelial cells. Analysis by fluorescence flow cytometry showed that a
live P5-fimbriated NTHI strain (NTHIF+) attached to a
higher proportion of RSV-exposed A549 cells than to control cells
(mean, 68% for RSV versus 29% for control; P = 0.008), while attachment of the P5-fimbriae-deficient isogenic mutant strain (NTHIF
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Fimbria-Mediated Enhanced Attachment of Nontypeable
Haemophilus influenzae to Respiratory Syncytial
Virus-Infected Respiratory Epithelial Cells


) was significantly lower than in
control cells and rose only slightly following RSV exposure (mean, 17%
for RSV versus 10% for control, P = 0.229).
Attachment of NTHIF+ did not correlate with the amount of
RSV antigen expressed by A549 cells. Furthermore,
paraformaldehyde-fixed NTHIF+ also demonstrated an enhanced
binding to RSV-exposed cells. Observations by transmission electronic
microscopy showed that the mean number of bacteria attached per 100 RSV-exposed A549 cells was higher for NTHIF+ than
NTHIF
(99 versus 18; P < 0.001). No
intracellular bacteria were identified. UV-irradiated conditioned
supernatants collected from RSV-infected A549 cultures (UV-cRSV) also
enhanced the attachment of NTHIF+ to A549, suggesting the
presence of a preformed soluble mediator(s) in UV-cRSV that enhances
the expression of receptors for P5-fimbriae on A549 cells. In summary,
RSV infection significantly enhances NTHI attachment to respiratory
epithelial cells. P5-fimbria is the critical appendage of NTHI that
participates in this attachment. In clinical settings, blocking of the
P5-fimbria-mediated attachment of NTHIF+ by passive or
active immunity may reduce the morbidity due to NTHI during RSV infection.
*
Corresponding author. Mailing address: Division of
Pediatric Infectious Diseases, Children's Hospital at the University
of Texas Medical Branch, 301 University Blvd., Galveston, TX
77555-0371. Phone: (409) 772-2798. Fax: (409) 747-1753. E-mail:
janak.patel{at}utmb.edu.
Present address: Tomakomai City General Hospital, Tomakomai, Japan.
Present address: Gateway Community Health Center, Laredo, Tex.
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