Increasing importance of viruses in acute otitis media

Innate Immunity in the Middle Ear Mucosa

Otitis media (OM) encompasses a spectrum of clinical presentations ranging from the readily identifiable Acute OM (AOM), which is characterised by otalgia and fever, to chronic otitis media with effusion (COME) where impaired hearing due to middle ear effusion may be the only clinical symptom. Chronic suppurative OM (CSOM) presents as a more severe form of OM, involving perforation of the tympanic membrane. The pathogenesis of OM in these varied clinical presentations is unclear but activation of the innate inflammatory responses to viral and/or bacterial infection of the upper respiratory tract performs an integral role. This localised inflammatory response can persist even after pathogens are cleared from the middle ear, eustachian tubes and, in the case of respiratory viruses, even the nasal compartment. Children prone to OM may experience an over exuberant inflammatory response that underlies the development of chronic forms of OM and their sequelae, including hearing impairment. Treatments for chronic effusive forms of OM are limited, with current therapeutic guidelines recommending a "watch and wait" strategy rather than active treatment with antibiotics, corticosteroids or other anti-inflammatory drugs. Overall, there is a clear need for more targeted and effective treatments that either prevent or reduce the hyper-inflammatory response associated with chronic forms of OM. Improved treatment options rely upon an in-depth understanding of OM pathogenesis, particularly the role of the host innate immune response during acute OM. In this paper, we review the current literature regarding the innate immune response within the middle ear to bacterial and viral otopathogens alone, and as co-infections. This is an important consideration, as the role of respiratory viruses as primary pathogens in OM is not yet fully understood. Furthermore, increased reporting from PCR-based diagnostics, indicates that viral/bacterial co-infections in the middle ear are more common than bacterial infections alone. Increasingly, the mechanisms by which viral/bacterial co-infections may drive or maintain complex innate immune responses and inflammation during OM as a chronic response require investigation. Improved understanding of the pathogenesis of chronic OM, including host innate immune response within the middle ear is vital for development of improved diagnostic and treatment options for our children.

Detection of respiratory viruses in nasopharyngeal secretions and middle ear fluid from children with acute otitis media

CONCLUSIONS

Our results suggest that various respiratory viruses contribute to the pathogenesis of acute otitis media (AOM).

OBJECTIVE

AOM is one of the most common complications of viral upper respiratory tract infections in children. Recently, the importance of respiratory viruses has been stressed as causative agents of AOM.

SUBJECTS AND METHODS

A total of 1092 children < or =10 years old (average age 1.38 years) diagnosed as having AOM between 2002 and 2004 were studied. Bacterial and viral cultures of both nasopharyngeal secretions (NPS) and middle ear fluid (MEF) were performed for all 1092 children. Body temperature, changes of the tympanic membrane, and the number of days from the onset of illness were analyzed.

RESULTS

Respiratory viruses were detected in 360 of 1092 NPS specimens, including 157 isolates of respiratory syncytial virus and 88 of influenza virus. Among 1092 MEF specimens, 102 were virus-positive, including 43 for respiratory syncytial virus and 29 for influenza virus. In 75 children, respiratory viruses were only detected in MEF. The viral detection rate was higher in children with fever at an early stage of their illness. The tympanic membrane changes associated with viral infection tended to be less severe, while changes were more severe in cases with bacterial infection, especially co-infection with bacteria and viruses.

Tympanometric findings in young children during upper respiratory tract infections with and without acute otitis media

BACKGROUND

Upper respiratory tract infections (URI) likely lead to acute otitis media (AOM) by causing Eustachian tube dysfunction which creates negative middle ear pressure. Children younger than 2 years of age are at highest risk for AOM compared with older children and adults. There has been no published study comparing the middle ear status during URI in infants and young children by age group.

METHODS

We analyzed data from a prospective, longitudinal study of virus-induced AOM. Healthy children 6-35 months of age were enrolled in a study designed to capture all AOM after URI during a 1-year follow-up period. Tympanometry was used to address the middle ear status; tympanometric findings during the first week of URI were compared among different age groups. Tympanograms were classified into type A (normal), type B (middle ear effusion), and type C (negative middle ear pressure).

RESULTS

Children 6-11 months of age with URI experienced abnormal tympanograms more frequently than older children (P < 0.001). The peak day for an abnormal tympanogram was day 2 of the URI. Abnormal tympanogram tended to be type B in children age 6-23 months and type C in children age 24-47 months (P < 0.001). One-third of children older than 24 months of age had type C tympanogram during the first week of URI.

CONCLUSIONS

Eustachian tube dysfunction and middle ear abnormality during URI are more severe in children younger than 2 years of age, compared with older children. These findings could help explain the higher incidence of AOM after URI in younger children.

Acute otitis media associated with cytomegalovirus infection in infants and children

OBJECTIVE

Acute otitis media (AOM) is one of the most common complications of viral respiratory tract infections in children, but the role of each virus is still to be elucidated. We analyzed AOM associated with infection by cytomegalovirus (CMV), which is known as one of the major causes of viral respiratory tract infection.

METHODS

Four hundred and ninety-five children (292 boys and 203 girls) diagnosed as having AOM in 2002 were studied. All of the children were under 6 years old, with the average age being 1.31+/-1.36 years. Bacterial and viral culture of both nasopharyngeal secretions (NPS) and middle ear fluid (MEF) was performed in all 495 children. The levels of glutamyl pyruvic transaminase (GPT) and the serum IgM antibody for CMV were measured. CMV infection was defined on the basis of isolation of this virus by culture and/or positive anti-CMV IgM antibody. NPS and MEF specimens of the subjects diagnosed as having CMV infection were tested for the virus by nested PCR.

RESULTS

Twelve of the 495 children were found to have CMV infection. They included 6 boys and 6 girls aged from 3 to 25 months, with the average age being 11+/-7 months. Among 10 children in whom CMV infection was diagnosed by viral culture, CMV was isolated from NPS alone in nine cases and from both NPS and MEF in one case. Nested PCR was performed in all 12 subjects diagnosed as having CMV infection, and all NPS samples were positive, as were 8 MEF samples. We obtained serum samples from 205 children under 2 years of age, including 9 with CMV infection. The mean serum GPT level of 124 children in whom no viruses were detected was 20.7+/-14.4 IU/L. While, the serum GPT levels of 9 children with CMV infection ranged from 10 to 280 IU/L with the average titer being 78.4+/-81.9 IU/L, and the GPT levels of the children with CMV infection were significantly higher than those of the children in whom no viruses were detected (p<0.05).

CONCLUSION

Our results suggested that CMV is a causative pathogen of AOM, and that CMV infection should be suspected in patients with AOM and liver dysfunction.

Isolation of measles virus from middle ear fluid of infants with acute otitis media

Measles virus was isolated from the middle ear fluid (MEF) of two infant cases of acute otitis media (AOM) associated with measles. This is the first report on the isolation of measles virus from the MEF in patients with AOM, and possibility of the measles virus as a causative agent of AOM was suggested.

The occurrence of Chlamydia pneumoniae, Mycoplasma pneumoniae, and herpesviruses in otitis media with effusion

In a previous report we found Chlamydia (C.) pneumoniae to be present in middle ear fluids (MEE) from older children with otitis media with effusion (OME). However, OME is a disease of younger children the present study was conducted in toddlers. MEEs (n = 150) and nasopharynx samples (n = 83) from children with OME was analyzed by PCR for the presence of C. pneumoniae and Mycoplasma (M.) pneumoniae. C. pneumoniae was not present in any and M. pneumoniae only in one of the MEEs, and these pathogens could be demonstrated in one and two nasopharynx samples, respectively. Further, 133 MEEs were analyzed by PCR for the presence of the 8 human herpesviruses, and all samples were found to be negative. We conclude that neither C. pneumoniae or M. pneumoniae, or any of the 8 human herpesviruses seems to play a major role in the pathogenesis of OME in early childhood OME.

Viral respiratory infections due to rhinoviruses: current knowledge, new developments

Viral respiratory infections (VRIs) are among the most common reasons for which primary care providers are consulted. VRIs due to rhinoviruses-the most commonly implicated etiologic agent-constitute a syndrome characterized by signs and symptoms of a cold. Rhinoviruses have been implicated in respiratory tract illnesses such as sinusitis and otitis media, as well as lower respiratory complications in high-risk populations. Most patients treat VRI with over-the-counter remedies that have been demonstrated to produce marginal clinical benefits. The development of novel antiviral agents has intensified interest in VRIs. Pleconaril, a capsid-function inhibitor currently under FDA review, has been shown in clinical trials to reduce the duration and severity of rhinovirus VRIs. By targeting the cause of illness, antiviral agents represent an opportunity to reduce the substantial clinical burden of VRI. Furthermore, effective therapies can potentially reduce inappropriate antibiotic use for viral infections.

Causes for massive bacterial colonization on mucosal membranes during infectious mononucleosis: implications for acute otitis media

OBJECTIVE

A common complication of virus-induced upper respiratory tract infections is acute otitis media caused by bacterial pathogens. Simultaneously, increased bacterial colonization in the nasopharynx occurs. Our intention in this study was to identify the causes of this increased colonization of bacteria by evaluating their coating with the antibacterial substances lysozyme, lactoferrin and immunoglobulins IgG, S-IgA and IgM and their ability to penetrate epithelial cells during infectious mononucleosis (IM) caused by Epstein-Barr virus.

METHODS

Cellular samples were collected from the oropharynx of 21 patients (16 males, five females; age range 10-21 years) with current IM. An immunocytochemical assay using gold-labelled antiserum to human lysozyme, lactoferrin, IgG, S-IgA and IgM followed by gold particle and epithelial cell tracing in the transmission electron microscope.

RESULTS

A significant reduction in bacterial coating with IgG (P<0.05) and S-IgA (P<0.01) was noted, whereas there was a significant increase in coating with lactoferrin (P<0.01) and IgM (P<0.01). No significant change in lysozyme coating of the bacteria was noted, compared with healthy controls. Bacterial penetration into epithelial cells was seen particularly in patients culture-positive for beta-haemolytic streptococci.

CONCLUSIONS

Reduced bacterial coating with IgG and S-IgA immunoglobulins, combined with bacterial penetration into epithelial cells, may exacerbate the bacterial colonization on oropharyngeal mucosal membranes observed during IM.

Suppression of epithelial ion transport transcripts during pneumococcal acute otitis media in the rat

Until recently, it was not feasible to conduct genome-wide screening for gene transcript variations that play key roles in the pathogenesis of otitis media. In this study microarray technology was used to profile differential gene expression patterns from rat middle ear mucosa at 12 and 48 h after Streptococcus pneumoniae challenge. Real-time polymerase chain reaction was performed for independent verification of the microarray results. Three ion transport mRNAs were simultaneously suppressed more than 4-fold at 12 h in bacteria-challenged ears, including Na,K-ATPase alpha I subunit (SPATPa1), sodium channel beta 2 subunit (SCNB2) and sodium-hydrogen exchange protein isoform 2 subunit (NHE2). At 48 h after infection, the mRNA levels of SCNB2 and NHE2 had decreased 7- and 10-fold, respectively, whereas the relatively abundant SPATPa1 transcript showed recovery. The downregulation of Na(+)-transporting transcripts suggests a reduced number of epithelial cells and transporting proteins and/or the dysfunction of sodium transporters secondary to the bacterial infection. These changes can disrupt the coupling of the apical Na + entry and basolateral Na + extrusion, deplete the electrochemical Na+ transmembrane gradient, disrupt the intracellular osmotic equilibrium and lead to intracellular acidification and the accumulation of excess sodium, water and other organic and inorganic molecules in the middle ear cavity. Any or all of these changes may contribute to the initiation and persistence of middle ear mucosa inflammation and effusion during an episode of bacterial acute otitis media.

Acute upper airway infections

Upper respiratory tract infections are common and important. Although rarely fatal, they are a source of significant morbidity and carry a considerable economic burden. Numerous therapies for the common cold have no effect on symptoms or outcome. Complications such as cough are not improved by over-the-counter preparations, while labelling cough alone as a symptom of asthma may result in unnecessary use of inhaled steroid treatment. Clinical presentation of sore throat does not accurately predict whether the infection is viral or bacterial, while throat culture and rapid antigen tests do not significantly change prescribing practice. Antibiotics have only a limited place in the management of recurrent sore throat due to group A beta-haemolytic streptococcal infection. Routine use of antibiotics in upper respiratory infection enhances parent belief in their effectiveness and increases the likelihood of future consultation in primary care for minor self-limiting illness. Respiratory viruses play a major role in the aetiology of acute otitis media (AOM); prevention includes the use of influenza or RSV vaccination, in addition to reducing other risk factors such as early exposure to respiratory viruses in day-care settings and to environmental tobacco smoke. The use of ventilation tubes (grommets) in secretory otitis media (SOM) remains controversial with conflicting data on developmental outcome and quality of life in young children. New conjugate pneumococcal vaccines appear safe in young children and prevent 6-7% of clinically diagnosed AOM.

Immunotherapy through TCR gene transfer

The antigen specificity of T lymphocytes is dictated solely by the T cell receptor (TCR) alpha and beta chains. Consequently, genetic transfer of TCR chains may be an appealing strategy with which to impose a desirable virus- or tumor-antigen specificity onto cytotoxic or helper T cell populations. We describe here the genetic introduction of a virus-specific TCR into peripheral T cells in a mouse model system. These experiments showed that T cells redirected by TCR gene transfer expanded upon viral infection of mice and efficiently homed to effector sites. In this setting, TCR gene transfer was not associated with any significant autoimmune pathology. In addition, small numbers of TCR-transduced T cells promoted the rejection of antigen-expressing tumors in vivo. These data suggest that the redirection of T cells by TCR gene transfer is a viable strategy for the rapid induction of virus- or tumor-specific immunity.