2001 Fiscal Year Final Research Report Summary
Elucidation of molecular-biological dynamics in the onset of otitis media
| Project/Area Number |
11671688
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Otorhinolaryngology
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| Research Institution | OITA MEDICAL UNIVERSITY |
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Principal Investigator |
SUZUKI Masashi Oita Medical University, Otolaryngology Professor, 医学部, 教授 (60211314)
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| Co-Investigator(Kenkyū-buntansha) |
MOGI Goro Oita Medical University, Vice-President, 医学部, 副学長 (20035190)
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| Project Period (FY) |
1999 – 2001
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| Keywords | Haemophilus influenzae / Outer membrane protein / P6 / Otitis media / Mucosal immune response / IgA / Adenoid / NALT / middle ear mucosa / Intranasal vaccine / cytokine / Virus |
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| Research Abstract |
1) Role of child adenoids in otitis media with effusion (OME) :
In order to investigate whether the adenoid is an active agent of OME, the adenoids of children with and without OME were compared regarding the macroscopic size, the bacteriological examination, reticular formation of the epithelium, and the percent of ciliated epithelium. There was no significant difference in the size of adenoids. Nontypeable H. influenzas (NTHi) was cultured more frequently in adenoid specimens from children with OME. A tendency toward increased stratified squamous epithelium and decreased ciliated epithelium was apparent in children with OME. Reticular epithelium extension was greater in children with than without OME. These findings suggested that adenoid inflammation is implicated in the pathogenesis of OME and the adenoids have an important role in the cause of OME by being a reservoir for NTHi.
2) Effects of influenza A virus on nasopharyngeal bacterial colonization :
To clarify the role of viral inf
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ection in otitis media, influenza virus was inoculated mice and examined histologic changes in the nasopharynx. Live bacteriae were injected into the nasopharynx after virus inoculation, and the clearance of bacteria from the nasopharynx was examined. Staining of the mucous blanket and epithelial cell surfaces in the nasopharynx with peanut agglutinin, succinyl wheat-germ agglutinin and Bandeiraea simplicifolia aggulutinin was significantly enhanced with intranasal virus inoculation when compared with that in control animals. The nasopharynx was moderately stained with Maachia amurensis aggulutinin and wheat-germ agglutinin in control animals, and the staining was enhanced after virus inoculation. These findings were most remarkable 5 and 9 days after virus inoculation. The numbers of bacteria cultured from the nasopharynx were significantly increased when bacteria were injected 5 days after virus inoculation. These results suggest that an alteration in the glycoconjugate structure lining the nasopharyngeal mucosa caused by the influenza virus might be associated with the reduction hi bacterial clearance.
3) Role of IL-1β in a OME model
To clarify the role of IL-β in the pathogenesis of OME, a murine OME model was developed and examined. Mice received intratympanic injections of endotoxin. Three days after injection, middle ear effusions were observed. Similar pathological changes were observed after inoculation with recombinat IL-1β. Anti- IL-1 receptor antibodies inhibited the pathological changes induced by the endotoxin. In situ hybridization showed expression of IL-1β messenger RNA in the epithelium of the middle ear mucosa. These results suggest that IL-1β might be associated with endotoxin-induced iflammation in the middle ear and might play an important role in the induction of OME.
4) Mucosal immunity of the middle ear
In order to clarify the characteristics of the middle ear mucosa with respect to immune potential, lymphocyte subsets, mRNA of cytokines, and induction of antigen-specific IgA-producing cells in the middle ear mucosa were investigated in specific pathogen-free mice. Flow cytometric analysis showed a certain amount of γδT cells among CD3_+ T cells. P6-specific IgA-producing cells were induced by intranasal immunization with P6 together with choleratoxin. RT-PCR assay of mucosal T cells detected mRNA of Th2 type cytokined. These findings support the fact that the middle ear is a potentially an effector site of the mucosal immunity.
5) Induction of specific mucosal immune responses to NTHi in middle ear mucosa
To elucidate the possibility of developing a nasal vaccine against NTHi, mice were immunized intranasally with the P6 of NTHi and mucosal immune responses in the middle ear were examined. The P6 specific IgA titier in ear wash was significantly elevated. An increase in P6-specific IgA-producing cells in middle ear mucosa was detected. In vitro stimulation with P6 resulted in proliferation of purified CD4_+ T cells from immunized mice, and these T cells expressed Th2 cytokine mRNA. These results indicated that P6-specific IgA-B-cell immune responses and selected Th2 cytokine expressing Th cells were induced in middle ear mucosa by intranasal immunization.
6) Clearance of NTHi from the middle ear by intranasal immunization
To assess the effect of intranasal immunization with P6 for the protection against NTHi-induced otitis media, mice were immunized intranasally with the P6 and one week after the immunization a suspension of live of live NTHi was injected into the tympanic cavity to induce experimental OM. Immunized mice showed enhanced clearance of NTHi from the middle ear. Less stimulation of TNF-α production in the middle ear was shown after challenge. These results indicated that intranasal immunization affords protection against experimental otitis media. Less
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Research Products
(14 results)
