Are immune complexes a factor in the pathogenesis of otitis media with effusion?

Detection of genomic sequences of respiratory syncytial virus in otitis media with effusion in children

The reverse transcriptase-polymerase chain reaction and the nested polymerase chain reaction were used for detection of respiratory syncytial virus (RSV) sequences in middle ear effusions collected from children with otitis media. Sequences of RSV were detected in 21 of 34 samples tested. These samples were collected during and/or after natural outbreaks of RSV infection in the community. In those patients from whose nasopharynges RSV was isolated, the viral sequences were highly detectable (75%) in the effusions. These observations suggest RSV as an important factor in the pathogenesis of otitis media with effusion.

Immune-mediated otitis media with effusion

This study was designed to clarify the role of immune reaction in otitis media with effusion (OME). Immune-mediated OME was induced in chinchillas, and characteristics of the disease were evaluated biochemically, cytologically, and histologically. OME was induced by a single intratympanic inoculation of keyhole limpet hemocyanin (KLH) in animals which had a high serum anti-KLH IgG titer. In addition, OME was maintained for 3 weeks in seven of 17 chinchillas, boosted by intradermal and intratympanic injections at 1-week intervals. Cells in the middle ear effusion (MEE) consisted substantially of neutrophils, a few macrophages, and other cells. The mean histamine and prostaglandin E2 levels in the MEE significantly exceeded the levels in corresponding sera. The lining membrane of the bullae was edematous and thickened due to dilatation and rupture of blood capillaries and cell infiltration. Next, the animals were inoculated with immune complex into the tympanic cavity. MEE appeared in all treated ears within three days after injection. Biochemical, cytologic, and histologic findings of the immune complex-induced OME resembled those of immune-mediated OME. An immune peroxidase method demonstrated that neutrophils in MEE phagocytose immune complexes. Our findings suggest that a perpetual cycle of inflammatory substances may maintain an inflammatory condition in the middle ear.

Recurrence of antigen-induced otitis media by thiol compound

Reduced glutathione (GSH), a potential factor in the chronicity of human otitis media, was tested to determine its potency in the recurrence of antigen-induced otitis media in chinchillas sensitized with human serum albumin (HSA). GSH instillation into the healing middle ear bulla reproduced a level of otitis media similar to the original antigen-induced otitis media with cellular involvement occurring earlier, according to cytologic analyses. This study indicates that GSH is probably a factor in recurrent antigen-induced otitis media, controlling the balance between thiol proteases and thiol protease inhibitors during middle ear inflammation.

A rat model for pneumococcal otitis media

The middle ears of 29 male Sprague-Dawley rats were injected with viable pneumococci, type 3 or 6A, and changes were monitored by otomicroscopy and analysis of bacterial samples from middle ear effusions, blood, and the nasopharynx. Depending on the type of pneumococci and its concentration, three responses were noted: otitis media with purulent effusion, otitis media with serous effusion, or no reaction. The mortality rate was low and the animals recovered without permanent deterioration or otomicroscopically discernable change. The results of this study show the rat to be a suitable animal model for the study of bacterial otitis media.

Antiinflammatory effects of a corticosteroid and protease inhibitor agents on antigen-induced otitis media in chinchillas

Using an antigen-induced otitis media (OM) model in chinchillas sensitized with human serum albumin (HSA), we studied the antiinflammatory effect of a corticosteroid (triamcinolone) and a protease (kallikrein) inhibitor (aprotinin) by conducting both biochemical and cytologic analyses of middle ear fluid (MEF). The levels of HSA, alpha 1-antitrypsin, alpha 2-macroglobulin, and total protein concentration were measured in the MEF to evaluate the degree of OM. Both vascular leakage and leukocyte infiltration were significantly reduced by corticosteroid and inhibitor treatments. HSA levels in the MEF were markedly reduced after HSA challenge, and both treatments reduced the drop in HSA levels. In conclusion, the kallikrein-kinin system is related to the early stage of antigen-induced OM. Both corticosteroid and inhibitor treatments effectively reduce the degree of antigen-induced OM in chinchillas, suggesting that both may be useful local therapeutic agents in the treatment of human OM.

Pneumococcal antigens and endotoxin in effusions from patients with secretory otitis media

Counterimmunoelectrophoresis revealed pneumococcus capsular polysaccharide antigen in 16% of 108 effusions from chronic secretory otitis media (SOM). Pneumococci were cultured from the effusion in only 1%. In an additional series of 23 SOM ears, only 4.3% were antigen-positive. Tests by means of pneumococcal coagglutination and C-polysaccharide detection gave identical results. Endotoxin was detected in 76% of the specimens. Control tests with aggregated NHS, IgG and IgA diluted 1: 10 were invariably positive. It appears that endotoxin positivity in SOM fluids results from the presence of activated immunoglobulins, most probably dimeric IgA, in the secretion, and so allows no conclusions as to the bacterial etiology of SOM.

Pneumococcal immune complexes and clinical course of secretory otitis media

One-hundred-and-six children (182 ears) with secretory otitis media (SOM) were included in a follow-up study to determine whether presence of immune complexes to pneumococcal capsular polysaccharides in the middle ear fluid or adenoid suspension was related to the clinical course of SOM. The patients with immune complexes did not differ significantly from those without demonstrable immune complexes as to length of healing period or chronicity. The presence of immune complexes must be seen as evidence of the infectious etiology of SOM (pneumococcal in at least 25%), the immune complexes forming part of the immunological defense system. Poor immune response to serotype 6 can explain why this serotype plays a dominant role in the pneumococcal immune complexes in SOM fluid and adenoid suspension.

Histopathological changes of the eustachian tube in OME animal models

To determine whether or not stimulations of various inflammatory irritants such as endotoxin and/or immune complexes (IC) play a role in the pathogenesis of otitis media with effusion (OME), experimental animal models were examined under light and electron microscopy. Horseradish peroxidase (HRP) was chosen as an antigen and anti-HRP sera were obtained from the animals immunized by emulsions of HRP and Freund's complete adjuvant. Seventy-three albino guinea pigs and 41 chinchillas were used in this experiments. One hundred and fourteen animals were divided into three groups: forty in the active Arthus (AA) group, 61 in the passive Arthus (PA) group and 13 in the control group. According to the chronological changes of the tympanograms, it was confirmed that the pathological changes in the middle ear cleft of the OME animals persisted for at least 10-14 days after the injection, whereas those in the control animals recovered within 3-4 days. Histological examinations of both PA- and AA-group animals revealed that electron-dense HRP-positive cells, most of which were non-ciliated, were widely dispersed in the epithelium. Many inflammatory cells such as polymorphonuclear leukocyte (PMN), macrophage and plasma cells were seen in the lamina propria and some PMNs were attached to the basal lamina. Intra-epithelial infiltration of PMNs and epithelial cell degeneration associated with the disrupted basal lamina were also observed. Most conspicuous changes were found in the Eustachian tube.(ABSTRACT TRUNCATED AT 250 WORDS)

Experimental immune complex otitis media: localization of IgG by protein A-gold technique

Immune complex (IC) was made of bovine serum albumin (BSA) and anti-BSA guinea pig serum, and instilled into the tubotympanic cavity of untreated guinea pigs. The location of IgG was determined by using the protein A-gold technique to trace IC in the tubotympanic mucosa of the otitis media with effusion (OME) caused by the instillation. IgG was found on the effusion, degenerated ciliated cells and on granules of goblet cells. There was no evidence of intense accumulation of IgG on the basement membrane of the mucosal epithelium or the capillaries. It is likely that IC activates complements in the tubotympanic cavity to cause OME.

Observations on immune mechanisms in otitis media with effusion

In this brief review of recent advances in immunological reactivity in otitis media, I have neither attempted to review the field from a historical perspective, nor attempted a critical analysis of the current status and future frontiers of this area. I have, rather, reviewed 5 areas that are being pursued in our laboratory and compare our investigations with those being performed throughout the country and abroad. It is my sincere hope that investigations into these areas will continue and will lead to potentially fruitful and meaningful data that will eventually unravel the mystery of persistent OME.