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Infection and Immunity, June 2001, p. 3678-3684, Vol. 69, No. 6
Department of Otolaryngology, College of
Medicine and Public Health, The Ohio State University, Columbus, Ohio
Received 3 January 2001/Returned for modification 31 January
2001/Accepted 2 March 2001
To define the role of nontypeable Haemophilus
influenzae (NTHI) lipooligosaccharide (LOS) in the induction of
proinflammatory cytokine gene expression during otitis media, we
compared the abilities of formalin-killed NTHI strain 2019 and its LOS
htrB and rfaD mutants to stimulate human
middle ear epithelial (HMEE) cell cytokine and chemokine gene
expression and production in vitro. Strain DK-1, an rfaD
gene mutant, expresses a truncated LOS consisting of only three
deoxy-D-manno-octulosonic acid residues, a
single heptose, and lipid A. Strain B29, an isogenic
htrB mutant, possesses an altered oligosaccharide core
and an altered lipid A. HMEE cells were incubated with formalin-killed
NTHI 2019, B29, or DK-1. The supernatants and the cells were collected
at 2, 4, 8, and 24 h after stimulation. Expression of genes for
the cytokines tumor necrosis factor alpha (TNF-
0019-9567/01/$04.00+0 DOI: 10.1128/IAI.69.6.3678-3684.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Expression of Cytokine and Chemokine Genes by Human
Middle Ear Epithelial Cells Induced by Formalin-Killed
Haemophilus influenzae or Its Lipooligosaccharide
htrB and rfaD Mutants
), interleukin l
(IL-1
), and IL-6 and for the chemokines macrophage inflammatory
protein 1
(MIP-1
), monocyte chemotactic peptide 1 (MCP-1), and
IL-8 was quantitated by real-time PCR. NTHI B29 did not significantly
stimulate any cytokine or chemokine mRNA expression in HMEE cells. In
striking contrast, NTHI 2019 induced up to 105-, 139-, and 187-fold
increases in HMEE cell expression of IL-1
, TNF-
, and MIP-1
,
respectively (P < 0.01 [2019 versus B29]). NTHI
2019 also induced upregulation of IL-8, IL-6, and MCP-1 mRNA expression
(by 26-, 44-, and 14-fold, respectively [P < 0.05 {2019 versus B29}]). The significant induction of cytokine genes
was confirmed by quantitating the secretion of cytokines in culture
supernatants with an enzyme-linked immunosorbent assay. There were no
significant differences in mRNA expression of IL-8, IL-6, and MCP-1
between the 2019- and DK-1-treated groups. The low levels of gene
transcripts observed after incubation of HMEE cells with B29 indicate
that products of the disrupted NTHI htrB LOS gene may
play a major role in induction of these particular inflammatory mediators.
*
Corresponding author. Mailing address: Department of
Otolaryngology, The Ohio State University, Room 4331 UHC, 456 West 10th Ave., Columbus, OH 43210. Phone: (614) 293-8103. Fax: (614) 293-5506. E-mail: demaria.2{at}osu.edu.
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