Effect of experimental influenza A infection on systemic immune and inflammatory parameters in allergic and nonallergic adult subjects

BACKGROUND

The economic impact and medical complication rate of viral upper respiratory infections are well documented, but many of the physiologic, inflammatory, and immune responses to respiratory viruses have only recently been investigated. A previous study demonstrated differential systemic immune and inflammatory responses in allergic rhinitis (AR) and nonallergic rhinitis (NAR) subjects during experimental infection with rhinovirus-39.

OBJECTIVE

The purpose of this study was to compare selected systemic immune and inflammatory responses to experimental influenza A virus (FLU) challenge in seronegative AR and NAR subjects.

METHODS

Peripheral blood was obtained at baseline (study day 0) and 3, 6, 18, and 31 days after intranasal FLU challenge and assayed for leukocyte histamine release, serum immunoglobulins, and plasma histamine.

RESULTS

All subjects were infected, as manifested by viral shedding in nasal secretions and/or seroconversion. FLU infection induced decreases in spontaneous leukocyte histamine release and increases in anti-immunoglobulin E-induced leukocyte histamine release, which were evident at least 1 month after infection, but caused no significant changes in serum immunoglobulins or plasma histamine. There were no differences between AR and NAR subjects for any of the study parameters.

CONCLUSIONS

The results show that intranasal challenge with FLU induces changes in leukocyte histamine release, but not other systemic immune and inflammatory responses.

Urinary histamine metabolite elevations during experimental influenza infection

BACKGROUND

Although histamine is hypothesized to mediate symptoms induced by viral upper respiratory infections, elevations of this mediator have not been observed in nasal lavage fluids recovered from patients with viral upper respiratory infections.

OBJECTIVE

The purpose of this study was to use a novel method to determine whether histamine is released during experimental influenza A infection.

METHODS

Healthy adults (n = 15) were cloistered and inoculated intranasally with influenza A virus, and monitored for infection and illness. Daily morning void urines were collected and assayed for histamine and its metabolites by gas chromatography-mass spectrometry. Total histamine was calculated for each urine specimen by summing the assayed values of histamine and its metabolites.

RESULTS

All subjects were infected and developed illness. ANOVA documented a significant effect of study day (viral infection) on urinary levels of total histamine (P < 0.02). Pairwise analysis showed a significant elevation 2 days after inoculation.

CONCLUSIONS

These results provide the first direct evidence that histamine is released in vivo during infection with a virus that causes cold/flu symptoms.

Effect of intranasal challenge with interleukin-6 on upper airway symptomatology and physiology in allergic and nonallergic patients

BACKGROUND

Interleukin-6 (IL-6) is a potent regulator of airway inflammation and an important component of biologic homeostasis. Previously, a temporal relationship between the local elaboration of IL-6 and the development of upper airway symptoms and pathophysiologic findings was reported for patients experimentally infected with influenza A virus or rhinovirus.

OBJECTIVE

The objective of this study was to determine the provocative effects of direct, intranasal administration of IL-6 on those symptoms, signs, and pathophysiologic findings that accompany viral upper respiratory infection.

METHODS

In this double-blind, placebo-controlled, crossover trial, 10 symptomatic allergic, 10 asymptomatic allergic, and 10 nonallergic adult patients were pretreated with intranasal histamine and, after 15 minutes, were challenged with repeated doses of placebo (saline) or with increasing doses (0, 0.01, 0.1, and 1 microg/mL) of recombinant IL-6 at 20-minute intervals, during randomized paired sessions. Symptom scores, sneeze and cough counts, nasal secretion weights, nasal conductance (rhinomanometry), middle ear pressure (tympanometry), Eustachian tube function (sonotubometry), and pulmonary function (spirometry) were evaluated before and after the histamine challenge, after each dose of IL-6 or placebo, and then at 90 minutes and 2, 3, 4, 6, and 24 hours.

RESULTS

At the doses used, intranasal challenge with IL-6 was well tolerated. At the 90-minute postchallenge endpoint, a significant effect of challenge substance and group assignment was documented for nasal secretion weight. Paired comparisons showed that the effect was greater for the allergic patients when compared with the nonallergic patients. There were no differences between placebo and IL-6 challenge for any of the other measured parameters.

CONCLUSIONS

These results show that local IL-6 at relatively low doses can provoke increased nasal secretions in patients with allergic rhinitis.

Abnormal middle ear pressures during experimental influenza A virus infection--role of Eustachian tube function

INTRODUCTION

Experimental infection of adults with influenza A virus, rhinovirus or RSV causes abnormal ME pressure in some, but not all subjects. The hypothesis tested in this study is that the response variability is caused by constitutional differences in the functioning of the Eustachian tube.

METHODS

18 adult subjects were experimentally infected with influenza A virus. On five occasions before virus exposure, middle ear pressure (by tympanometry) and Eustachian tube function (by sonotubometry) were recorded bilaterally. Tests were repeated on days 1 through 8 and 10 after infection. Individual ears were classified with respect to the number of pre-exposure, positive sonotubometric testings and the middle ear pressure response to infection was compared between ears with Eustachian tube openings at all pre-infection test sessions (GR-A) and those with at least one negative test (GR-B).

RESULTS

Pre-exposure, 19, six, four, four, one and two ears had tubal openings on five, four, three, two, one and zero sessions, respectively. For that period, GR-A had significantly lesser average intra-ear and intra-group middle ear pressure variances compared to GR-B, but there were no between-group differences in the average middle ear pressure or in the number of observations of abnormal middle ear pressure. After virus exposure, middle ear pressure variances and the number of abnormal observations increased and the average pressure decreased in both groups, but the effects were more pronounced for GR-B ears.

CONCLUSIONS

These results support the hypothesis that pre-existing good Eustachian tube function reduces the otological complications of viral upper respiratory tract infection.

Mathematical model explaining the sources of error in certain estimates of the gas exchange constants for the middle ear

Mover-Lev and colleagues reported a carbon dioxide-oxygen time-constant ratio of 3.9 for transmucosal gas exchange in guinea pigs under conditions of a large positive oxygen pressure gradient and a negative carbon dioxide gradient. That ratio is much less than the value of 19 reported previously for monkeys and used in predictive models of middle ear pressure regulation. In this report, the mathematics that underlie models of transmucosal gas exchange are developed and the conditions that allow accurate estimation of time constants are defined. The results demonstrate that the experimental and analytic methods used by Mover-Lev et al do not control for certain confounding effects or concurrently measure all required system parameters. Under the most realistic conditions, their ratio of 3.9 represents a significant underestimation of a true value on the order of 10. Also, their expectation of nonvarying, transmucosal time constant ratios for pairings that include reactive gases is simplistic and true only for identical experimental contexts.

Experimental results do not support a gas reserve function for the mastoid

The mastoid is an aerated extension of the middle ear gas pocket whose state of development was shown to be an indicator of past and future otitis media experience. While the function(s) of the mastoid is not known, a number of hypotheses has been advanced to explain the reported association between mastoid size and middle ear disease. These include the hypotheses that, with respect to the middle ear, the mastoid functions as a pressure buffer, a gas reserve, and/or a pressure regulator. In this paper, a physical model of the mastoid is presented that makes specific predictions against which the validity of the hypothesized gas reserve function could be tested. Data from three published clinical experiments were evaluated for consistency with the predictions of the model, and the hypothesis was rejected. Also, when reinterpreted within the context of the model, the published data do not support a pressure-regulating function for the mastoid.

Prevention of otitis media with effusion by repeated air inflation in a monkey model

OBJECTIVES

To test the following hypotheses that (1) middle ear (ME) air inflation prevents the development of otitis media with effusion in a monkey model of functional eustachian tube obstruction, and (2) ME inflation treatment of otitis media with effusion can cause artifactual clinical improvements due to fluid displacement from the tympanum to the adjacent airspaces.

DESIGN

Randomized controlled trial.

SUBJECTS

Twelve cynomolgus monkeys.

INTERVENTIONS

Eustachian tube dysfunction was induced by botulinum paralysis of the right tensor veli palatini muscle in all monkeys. Before and on study days 9, 15, and 21 after paralysis, the presence or absence, and distribution of ME effusion were documented using magnetic resonance imaging (MRI). Right and left ears were examined twice daily for 21 days using tympanometry, and right ME air inflation (n = 6 ears) or sham inflation (n = 6 ears) was done immediately after those examinations if the ME pressure was -100 mm H2O or less. On 10 of the scheduled MRI evaluations, the MRI was repeated immediately after an inflation to document the possible redistribution of fluid within the ME caused by the maneuver.

RESULTS

Middle ear pressure remained within normal limits for the follow-up period in 11 of the 12 nonparalyzed left ears, in none of the 6 sham-inflated right ears, and in 3 of the 6 air-inflated right ears. Three air-inflated right ears developed flat tympanograms (ie, days 14 through 16). Magnetic resonance imaging documented inflammation and fluid in 1 of the 11 nonparalyzed left ears and in all sham-inflated right ears. Lesser degrees of inflammation and effusion based on MRI evaluations were noted for the 3 air-inflated right ears that retained near-ambient pressures when compared with the right 3 ears that developed a flat tympanogram. The MRI measure of effusion quantity within the tympanum was decreased acutely after inflation, but was simultaneously increased in the adjacent airspaces of the temporal bone.

CONCLUSIONS

Repeated air inflation prevented the development of otitis media with effusion in 50% of the ears with functional eustachian tube obstruction. Postinflation MRI documented the displacement of fluid by inflation from the tympanum to the mastoid and petrous air cells. Using standard clinical evaluations such as tympanometry and otoscopy, this fluid redistribution can cause a false diagnosis of improvement.

The effects of changing middle ear pressure and gas partial pressure on mucosal blood flow and vascular permeability in the chinchilla

OBJECTIVE

To determine if middle ear (ME) gas composition and/or total pressure regulates local mucosal blood flow (MBF) and vascular permeability. The hypotheses tested are: (1) relatively high local CO2 tensions and/or low O2 tensions increase the ME MBF and vascular permeability; and (2) sub-atmospheric total ME pressure provokes similar effects.

METHODS

The responses of ME MBF and vascular permeability parameters were measured during 60 min exposures of chinchilla MEs to one of two test gas mixtures (16.3% O2, 5.1% CO2, balance N2, or 5.3% O2, 15.6% CO2, balance N2) applied at different levels of underpressure (ref. ambient). In the first set of experiments (n = 19), mucosal perfusion parameters were recorded using a Laser Doppler Flowmeter for 60 min before and 60 min after exposure to the experimental conditions. In the second set of experiments (n = 19 chinchillas, 38 ears), the MEs were exposed to the gas mixtures and then maintained for 60 min at ambient pressure or at negative pressures of -200, -400, -600 mmH2O. Fifty minutes into the experiment, the animals were injected intravenously with 60 mg/kg of horseradish peroxidase (HRP). The animals were killed and existing effusion was aspirated, its volume recorded and then analyzed for total protein. From surface preparations of the ME mucosa, vascular leakage sites were measured as percent total surface area using an image analysis program with the threshold window set to discriminate HRP stain.

RESULTS

Throughout the 120 min in the first set of experiments, the measured MBF parameters decreased in all exposure groups. Comparisons among groups for the absolute magnitude of the change from baseline showed that high local CO2 partial pressures decreased MBF and ME underpressures increased MBF, but the effects did not achieve statistical significance. The results of the second set of experiments demonstrated no effect of gas composition on any of the measured parameters of vascular permeability. All measures of permeability were linearly related to the magnitude of the underpressure.

CONCLUSION

These data support a role for total ME pressure, but not CO2 partial pressure in regulating ME MBF and vascular permeability.

Mucosal surface area determines the middle ear pressure response following establishment of sniff-induced underpressures

INTRODUCTION

Miura and colleagues presented data that they interpreted as evidencing a pressure-regulating function of the mastoid mucosa. Specifically, they reported different responses after sniff-induced middle ear (ME) underpressure for ears with and without a history of otitis media with effusion (OME). To understand the mechanism underlying that effect, a previously developed mathematical model was adapted to their experiment and used to simulate the expected pressure-time functions under different conditions.

METHODS

A simple, two-compartment model of passive, gradient-driven, trans-mucosal gas exchange was used to simulate ME pressure behaviour. Initial conditions for the free parameters of the model were taken from published data for humans and monkeys. Functions relating surface area to volume for geometric representations of the ME were constructed and used as model parameters. The effect of sniffing on ME gas partial pressure was modelled as a fractional reduction proportional to gas representation in the ME.

RESULTS

The model accurately simulated the time course and magnitude of the post-sniffing pressure change reported for both normal and abnormal MEs. The post-sniffing pressure increase is driven by sniff-induced blood-ME partial pressure gradients for CO2, O2, and H2O, which cause passive counter-diffusion of those gases. The effect of disease on the rate of pressure increase is attributable to the reduced surface area for exchange caused by underdevelopment of the mastoid in ears with a history of OME.

CONCLUSIONS

These results do not support a pressure-regulating role for the mastoid mucosa. Contrary to currently held beliefs, the model simulation suggests that small, not large mastoid volumes buffer ME pressure from rapid change due to trans-mucosal gas transfers.

Validation by magnetic resonance imaging of tympanometry for diagnosing middle ear effusion

This study was performed to correlate tympanometric gradient with measurements of effusion quantity by use of MRI during an experimental otitis media with effusion episode in 4 cynomolgus monkeys. Paired results for the intensity values of the T(2)-weighted MRI scans and the tympanometric width measured in the right ear of all animals before and on days 15, 21, 29, and 36 after botulinum paralysis of the tensor veli palatini muscle were analyzed. All right ears showed a progressive increase during the study period in the signal intensity of the MRI. Whereas the average middle ear pressures decreased, the average tympanometric widths demonstrated a progressive increase during the course of the experimental otitis media with effusion. Significant correlations between tympanometric width and MRI measures of effusion were documented, confirming the high predictive value of the tympanometric width for diagnosing the presence and quantity of middle ear effusion.

Middle ear inflation for diagnosis and treatment of otitis media with effusion

An adult (18 years), healthy, male subject with persistent bilateral middle ear (ME) underpressure and a history of recurrent otitis media into his teen years was identified. The response of his MEs to air inflation was evaluated and showed an immediate pressure increase after a Valsalva maneuver followed by a rapid pressure drop to approach the pre-inflation levels. That response is consistent with the presence of ME effusion, which was not diagnosed by otoendoscopy or tympanometry, but was visualized bilaterally within the mastoid regions using magnetic resonance imaging (MRI). The patient was treated for 25 days with ME inflation (3/day) and then re-examined. On each treatment day, he recorded his ME pressure using tympanometry before and after one inflation maneuver. The patient's compliance with the treatment protocol was high, and successful gas transfers were documented on most days. Over the course of treatment, pre-inflation ME pressure became more normal bilaterally. When compared to the pre-treatment test, the post-treatment inflation test showed a similar rate of ME pressure decrease, but significantly higher terminal pressures. On follow-up but not during the pre-treatment period, discrete changes in ME pressure attributable to ET openings were noted during test sessions. MRI documented lesser amounts of effusion in the mastoid, but not complete disease resolution. The significance of these observations to the design of a well controlled clinical trail of ME inflation as a treatment for otitis media is discussed.

The impact of personality on the reporting of unfounded symptoms and illness

This study examined the role of personality in the reporting of symptoms and illness not supported by underlying pathology. After assessment of the Big Five personality factors, 276 healthy volunteers were inoculated with a common cold virus. On each of the following 5 days, objective indicators of pathology, self-reported symptoms, and self-reported illness onset were assessed. Neuroticism was directly associated with reports of unfounded (without a physiological basis) symptoms in individuals at baseline and postinoculation in those with and without colds. Neuroticism was also indirectly associated with reports of unfounded illness through reports of more symptoms. Openness to Experience was associated with reporting unfounded symptoms in those with verifiable colds, whereas Conscientiousness was associated with reporting unfounded illness in those who were not ill.

The impact of personality on the reporting of unfounded symptoms and illness

This study examined the role of personality in the reporting of symptoms and illness not supported by underlying pathology. After assessment of the Big Five personality factors, 276 healthy volunteers were inoculated with a common cold virus. On each of the following 5 days, objective indicators of pathology, self-reported symptoms, and self-reported illness onset were assessed. Neuroticism was directly associated with reports of unfounded (without a physiological basis) symptoms in individuals at baseline and postinoculation in those with and without colds. Neuroticism was also indirectly associated with reports of unfounded illness through reports of more symptoms. Openness to Experience was associated with reporting unfounded symptoms in those with verifiable colds, whereas Conscientiousness was associated with reporting unfounded illness in those who were not ill.

MRI validation of the accuracy of tympanometric gradient for the diagnosis of OME

Tympanometry provides a rapid, non-invasive and objective assessment of middle ear (ME) status and is widely used for the clinical diagnosis and follow-up of otitis media with effusion (OME). ME pressure, acoustic admittance and tympanometric gradient are the main test parameters used in making assignments to diagnostic classes (i.e. presence or absence of effusion, effusion quantity). Of these, the tympanometric gradient was suggested to be more sensitive to the presence of effusion, but this has not been demonstrated conclusively and no standard definition of that gradient is accepted. In this study, 10 cynomolgus monkeys with experimental OME were used to compare the diagnosis of OME made using three different methods to estimate tympanometric gradient with that provided by simultaneous magnetic resonance imaging (MRI) of the ME. All three methods of tympanometric gradient measurement were highly correlated with the quantity of ME effusion measured by the MRI. Although not significant, the MRI results were better correlated with those for the 'width' method when compared to either the 'difference' or the 'ratio' method of gradient estimation. This study demonstrates the use of MRI as a gold standard for evaluating the accuracy of other methods to diagnose ME effusion.

Repeated inflation does not prevent otitis media with effusion in a monkey model

OBJECTIVE

Investigate the efficacy of repeated middle ear inflation with an inert gas (argon) for preventing the development of middle ear effusion in monkeys with functional eustachian tube obstruction.

STUDY DESIGN

Prospective controlled trial of daily middle ear inflation with five monkeys assigned to the inflation group and four to the control group.

METHODS

The right tensor veli palatini muscle of nine monkeys was paralyzed with botulinum toxin. Tympanometry was done before the procedure and then daily for 21 days. Presence and distribution of effusion were assessed before paralysis and on day 15 using magnetic resonance imaging (MRI). In five right ears inflation was done beginning at the first observation of negative middle ear pressure of < or =200 mm H2O and repeated on all days with pressures < or =-100 mm H2O. Four right ears served as uninflated controls.

RESULTS

Right middle ear pressure decreased in all animals over the course of the study. Pressure returned to near-ambient levels immediately following the argon inflation but was decreased to control levels at the subsequent observation on the following day. MRI at day 15 documented effusion in all right ears with no quantifiable differences in amount or distribution between ears that were and were not inflated with argon.

CONCLUSIONS

Repeated inflation with an inert gas does not prevent middle ear effusion in monkeys with functional eustachian tube obstruction.

Evidence for cytokine mediation of disease expression in adults experimentally infected with influenza A virus

The roles of interleukin (IL)-6 and IL-8 in mediating the symptoms and signs of influenza A infection were examined. Adults were intranasally inoculated with a rimantadine-sensitive strain of influenza A HlNl virus and treated with rimantadine or placebo. Viral shedding, secretion weights, symptom scores, and concentrations of IL-6 and IL-8 in nasal lavage fluids were compared between treatment groups. Viral shedding was associated with increases in local and systemic symptoms, in expelled secretion weights, and in levels of IL-6 and IL-8. Compared with placebo, rimantadine treatment reduced viral shedding, systemic symptoms, and levels of IL-8. Days of viral shedding and IL-6 but not IL-8 concentrations were significantly correlated with the other measures of symptoms and signs. These data support a causal relationship between viral replication, cytokine production, and symptom expression, and they suggest that IL-6 may have a role in mediating symptom and sign expression during influenza A infection.

Higher rates of pressure decrease in inflamed compared with noninflamed middle ears

Recent clinical trials have renewed interest in middle ear inflation as a treatment for otitis media with effusion. However, air inflation in human beings with significant negative middle ear pressures was shown to be followed by a rapid pressure decrease to approach the preinflation values. In this experiment, the middle ears of anesthetized rhesus monkeys with unilateral inflammation were inflated at different times with air or N2, and pressures were recorded by tympanometry until they had stabilized or the animal had recovered from anesthesia. The results for air inflations reproduced those reported for human beings with negative pressures. Similarly, after N2 inflation a significantly greater rate of pressure decrease and significantly lesser terminal pressures were observed for inflamed ears when compared with the contralateral control ears. However, the rate of pressure decrease and the magnitude of the pressure drop were dampened by sequential N2 inflations. These observations have clinical implications with respect to the efficacy of inflation as a treatment for otitis media with effusion.

Effects of nasal obstruction on Eustachian tube function and middle ear pressure

To evaluate the relationship between nasal obstruction and otitis media, 10 ferrets were studied before and after either unilateral (E = 5) or bilateral (n = 5) nasal obstruction. Observations included otomicroscopic assessments of middle ear status, tympanometric recordings of middle ear pressure and forced-response, inflation-deflation and continuous monitoring tests of Eustachian tube function. During the 6 8 week post-obstruction follow-up period no animal developed evidence of otitis media. Abnormal positive middle ear pressures lasting for the period of follow-up occurred only in the animals with bilateral nasal obstruction. Eustachian tube function test results showed these pressures to be generated during swallowing. No changes in the passive function of the tube were documented in either group, but changes in active function consistent with alterations in the pressure gradient between the middle ear and the nasopharynx were observed in both groups.

Diminished IL-10 production in subjects with allergy after infection with influenza A virus

BACKGROUND

Recent studies have documented a link between respiratory viral infections and the expression of asthma and other allergic disorders. Results from other studies have suggested that diminished production of IL-10, an anti-inflammatory cytokine, may contribute to the pathophysiologic features of these diseases.

OBJECTIVE

The objective of this study was to determine whether diminished IL-10 production and TH2 cytokine skewing occur in allergic, as compared with nonallergic, subjects after experimental infection with the influenza A virus.

METHODS

PBMCs were isolated from 11 subjects with allergy and 14 subjects with no allergy before and after influenza A infection and stimulated with either mitogen (PHA) or antigen (influenza A). Supernatants were assayed for IL-10, IL-4, and IFN-gamma by ELISA.

RESULTS

PBMC IL-10 production was significantly diminished in subjects with allergy, as compared with subjects with no allergy, after experimental infection with influenza A virus. However, significant TH2 skewing and enhanced airway symptoms were not observed in these same subjects.

CONCLUSIONS

These data provide further support that subjects with allergy have an intrinsic inability to upregulate IL-10 production in response to inflammatory stimuli and extend this observation to include respiratory viral infections. Future studies in this area could lead to a better understanding of the pathogenesis of asthma and other allergic disorders

Personality and tonic cardiovascular, neuroendocrine, and immune parameters

Although there is now abundant evidence that certain personality features constitute risk factors for negative health outcomes, personality measures have received little attention to date in the behavioral immunology literature. The present study assessed the relationship between major dimensions of personality and tonic cardiovascular, neuroendocrine, and immunologic parameters in 276 healthy adults. Participants who scored low in agreeableness tended to have higher levels of systolic blood pressure, diastolic blood pressure, and epinephrine. Low levels of extraversion were associated with higher blood pressure, epinephrine, norepinephrine, and natural killer cell cytotoxicity. Neuroticism was generally unrelated to physiologic outcomes. Personality was not associated with leukocyte subset counts. The magnitude of relationships between personality and physiology was modest, with personality measures accounting for 1 to 7% of the variance in selected physiological parameters. Health practices did not mediate associations between personality and physiologic outcomes. However, a substantial proportion of the relationship between extraversion and natural killer cell cytotoxicity was accounted for by their common association with epinephrine and to a lesser extent norepinephrine. These findings are consistent with the notion that personality contributes to basal physiology and provide a foundation for further research on the relationship between personality and natural killer cell cytotoxicity.

Psychological stress, cytokine production, and severity of upper respiratory illness

OBJECTIVE

The purpose of this study is to assess the role of psychological stress in the expression of illness among infected subjects and to test the plausibility of local proinflammatory cytokine production as a pathway linking stress to illness.

METHODS

After completing a measure of psychological stress, 55 subjects were experimentally infected with an influenza A virus. Subjects were monitored in quarantine daily for upper respiratory symptoms, mucus production, and nasal lavage levels of interleukin (IL)-6.

RESULTS

Higher psychological stress assessed before the viral challenge was associated with greater symptom scores, greater mucus weights, and higher IL-6 lavage concentrations in response to infection. The IL-6 response was temporally related to the two markers of illness severity, and mediation analyses indicated that these data were consistent with IL-6 acting as a major pathway through which stress was associated with increased symptoms of illness. However, this pattern of data is also consistent with increases in IL-6 occurring in response to tissue damage associated with illness symptoms.

CONCLUSIONS

Psychological stress predicts a greater expression of illness and an increased production of IL-6 in response to an upper respiratory infection.

Illness and otological changes during upper respiratory virus infection

OBJECTIVES

Upper respiratory virus infection is associated with the expression of symptoms and signs of illness, and with the development of complications in anatomically contiguous structures. In most epidemiological studies, the frequency of the various complications is expressed as a fraction of the total population judged to be ill by report, signs, or symptoms. Because not all infected subjects become ill and because infected non-ill subjects may develop complications, such risk estimates could be inaccurate. The objective of this study was to estimate the magnitude of the presentation bias during controlled, experimental infections.

STUDY DESIGN

This was a prospective, experimental study of the relationship between illness and otological complications during experimental upper respiratory virus infection in 316 adult volunteers.

METHODS

The data for illness and for abnormal middle ear underpressure in adult (18-54 y) volunteers experimentally infected with one of three viruses (rhinovirus type 39, rhinovirus strain hanks, influenza A virus) were analyzed and expressed as the relative frequencies of infected subjects reporting illness, developing abnormal middle ear pressure, and developing abnormal middle ear pressure in the absence of illness.

RESULTS

For all three viruses, illness was documented in approximately 50% of the infected subjects. While the frequency of persons developing abnormal middle ear underpressure was greater in the infected-ill subjects, approximately one third of all infected subjects developing that complication did not report illness.

CONCLUSIONS

These results support a large presentation bias in epidemiological surveys of viral upper respiratory infections, and infer that those surveys underestimate the true frequency of complications resulting from such infections.

Trans-mucosal inert gas exchange constants for the monkey middle ear

OBJECTIVE

The purpose of the study was to estimate the exchange constants for Argon and N2 across the middle ear mucosa of monkeys for use in mathematical models of middle ear pressure regulation.

METHODS

In five anesthetized monkeys, the tympanic membrane was perforated and, with the animal breathing room air, a 13-ml probe attached to an Argon gas source and to a pressure transducer was introduced into the ear canal and sealed. The probe and middle ear volume was washed with Argon and then closed to the gas source. Gas samples were withdrawn from the probe at 15-min intervals for composition analysis using an online mass spectrometer. Probe partial pressures of Argon and N2 were regressed on time and the slopes of those functions were divided by the respective average partial pressure gradient for the interval to estimate the exchange constants.

RESULTS

The average trans-mucosal exchange constants for Argon and N2 were 0.0007 +/- 0.0001 and 0.0003 +/- 0.0001/min, respectively. The average ratio of the two constants was 2.60 +/- 0.36 which is not different from the value of 2.3 predicted for perfusion limited gas exchange.

CONCLUSION

These results confirm a very slow, perfusion limited trans-mucosal exchange of N2 and other inert gases across the middle ear mucosa. They infer that the required frequency of Eustachian tube openings to prevent the development of middle ear effusion is low and on the order of one/day.

A model to explain the rapid pressure decrease after air-inflation of diseased middle ears

OBJECTIVES

Air-inflation in humans and monkeys with significant negative middle ear pressure or with middle ear inflammation was shown to cause greater than ambient middle ear pressure initially, followed by a rapid rate of pressure decrease to approach the preinflation value.

STUDY DESIGN

A mathematical model of middle ear pressure regulation is presented and used to simulate air-inflation of the normal and diseased middle ear.

MATERIALS AND METHODS

The model represents the total volume of the middle ear as consisting of three subcompartments representing the airspace, effusion, and mucosa/blood. Gas exchange among those compartments was assumed to be diffusion limited, and the gas exchange between the mucosa/blood compartment and systemic blood was assumed to be perfusion limited. Disease was modeled as an increase in mucosal blood flow or, alternatively, as an increase in the volumes of the effusion and mucosa/blood compartments.

RESULTS

The predictions of the model agree better with the experimental data when the increased rate of pressure change after middle ear inflation in diseased ears is driven by an increased volume of the effusion compartment as opposed to an increased perfusion rate. The responsible mechanism is a rapid redistribution among subcompartments of the gas volume introduced into the air compartment.

CONCLUSIONS

These results suggest that middle ear inflation with inert gas can be used to diagnose the presence and relative amount of middle ear effusion, and that current protocols for treating otitis media with effusion using inflation need to be modified to optimize their intended effect.

Daily tympanometry in children during the cold season: association of otitis media with upper respiratory tract infections

The causal association between otitis media and viral upper respiratory tract infections (URI) suggests that early intervention during the course of a viral URI could prevent many episodes of otitis media. However, the feasibility of this approach can not be assessed at present since many aspects of the epidemiology and natural history of URI-associated otitis media are undefined. To address this deficiency, daily monitoring of middle ear status (tympanometry) and cold symptoms and weekly pneumatic otoscopy were done on a pilot cohort of 20 children. These children, between the ages of 2 and 6, were followed from November 1996 to April 1997. Compliance with symptom diaries was 85%, with tympanograms was 90%, and with weekly physician visits was 70%. During the study period, there were 53 'colds' (average 2.65 per child) and 28 new episodes of middle ear effusion (10 unilateral and 9 bilateral). Overall, 47.3% of the tympanograms were Type A, 17.2% Type C1, 9.4% Type C2, and 21.8% Type B. Children who developed MEE during the study spent more time with abnormal MEP (either MEP < -150 or flat) during both cold and healthy days than children who did not develop MEE. Temporally, during colds, high negative pressures preceded the development of Type B tympanograms in children who developed middle ear effusions. Children who did not develop effusions still had high negative pressures during colds, but recovered to a normal pressure within days. These observations document the feasibility of this investigational format for study of the sequential changes in middle ear status before, during and after a URI.

Treatment of chronic suppurative otitis media with topical ciprofloxacin

To date, only ofloxacin has been approved by the US Food and Drug Administration for treatment of ears with a nonintact tympanic membrane. The purpose of this study was to determine the safety and efficacy of topical ciprofloxacin hydrochloride in the treatment of experimental chronic suppurative otitis media caused by Pseudomonas aeruginosa infection in cynomolgus monkeys. Forty adult cynomolgus monkeys were divided into 4 equal groups, and their ears were challenged with P aeruginosa, drained for 3 weeks, then treated twice daily for 4 weeks with 1 of 4 randomly assigned agents: 1) ciprofloxacin, 2) saline, 3) Cortisporin, or 4) vehicle. The animals were followed up with auditory brain stem response testing, culture, otoscopy, and histopathology. Both ciprofloxacin and Cortisporin treatment resulted in a significantly more rapid rate of clearance of P aeruginosa as compared to treatment with saline (100% versus 20%). Eradication was not associated with resolution of otorrhea after a 4-week period of treatment. There were no significant changes in auditory brain stem response wave latencies for any of the treatment groups. Histopathologic data revealed that there was no statistically significant difference in the amount of outer hair cell loss for the ciprofloxacin group as compared to the control ear and other treatment groups. We conclude, therefore, that topical ciprofloxacin is not ototoxic and is effective in sterilizing the otorrhea, but does not promote resolution of the drainage, in this animal model.

Types of stressors that increase susceptibility to the common cold in healthy adults

Two-hundred seventy-six volunteers completed a life stressor interview and psychological questionnaires and provided blood and urine samples. They were then inoculated with common cold viruses and monitored for the onset of disease. Although severe acute stressful life events (less than 1 month long) were not associated with developing colds, severe chronic stressors (1 month or longer) were associated with a substantial increase in risk of disease. This relation was attributable primarily to under- or unemployment and to enduring interpersonal difficulties with family or friends. The association between chronic stressors and susceptibility to colds could not be fully explained by differences among stressed and nonstressed persons in social network characteristics, personality, health practices, or prechallenge endocrine or immune measures.

Prechallenge antibodies moderate disease expression in adults experimentally exposed to rhinovirus strain hanks

This double-blind study determined the influence of serum neutralizing antibody titers on the rate of infection and magnitude of disease expression after experimental exposure of adult volunteers to rhinovirus strain Hanks (RV-H). A total of 133 healthy volunteers were tested for antibody status, cloistered for a 6-day period, and challenged with RV-H at the end of the first cloister day. On these days, response to viral challenge is assessed with symptom diaries and physical examinations. The low-titer infected group was significantly different from the intermediate-titer infected and the uninfected groups in terms of postchallenge nasal and throat symptoms, expelled secretion weights, nasal mucociliary clearance rates, and frequency of negative middle ear pressures. A similar trend held for the infected high-titer vs. low-titer group comparisons. These data show that high homotypic serum neutralizing antibody titers are associated with protection from infection and lessened signs and symptoms following experimental RV-H exposure.

Exchange rates of gases across the tympanic membrane in rhesus monkeys

The exchange rates of CO2 and He across the tympanic membrane were estimated in 5 monkeys. For these experiments, the monkey was anesthetized and one arm of a polyethylene "T" tube was introduced into the external canal of the test ear and sealed to the ambient environment with wax. One arm of the T tube was attached to a pressure transducer and the other to an argon gas source via a valve. Silica tubing sealed within the probe provided periodic gas samples for composition analysis by an online mass spectrometer. Prior to each experiment, the probe was washed with Argon. In 5 experiments the probe was sealed within the external canal of animals with physiological middle ear gas compositions, and in 5 experiments the probe was sealed within the external canal of animals whose middle ears were partially washed with He. The gas in the probe was sampled and analyzed at 10-min intervals for up to 4 h. The results documented a significant increase in the percentage composition of CO2 but not He in the experiments conducted with physiological middle ear gas compositions, and increases in both He and CO2 in the experiments conducted after the middle ear was washed with He. Estimated, average exchange constants for He and CO2 were 0.0005 microl/min/mmHg and 0.0103 microl/min/mmHg, respectively. Using data from previous experiments, the relative trans-mucosal to trans-tympanic membrane gas exchange rates in monkeys are estimated to be in the order of 10:1 for inert gases and 180:1 for chemically active gases.

Rhinovirus infection induces mucus hypersecretion

Rhinorrhea is a prominent symptom of the common cold. Although increases in vascular permeability and serous cell secretion have been demonstrated in human nasal mucus during active rhinovirus infections, changes in mucin constituents have not been quantified. Nonallergic (n = 48) and asymptomatic allergic rhinitis (n = 32) subjects were inoculated with rhinovirus type hanks before the spring allergy season. Nasal lavages were performed before inoculation (day 0), then daily for 5 days afterward. The subjects were divided into infected and noninfected groups on the basis of evidence of successful rhinovirus infection (nasal shedding of virus or fourfold increases in specific serum antibodies). Concentrations of interleukin (IL)-8, markers of vascular leak (IgG), seromucous cells (lysozyme), and mucoglycoprotein exocytosis [7F10-immunoreactive mucin (7F10-irm) and Alcian blue staining of acidic mucoglycoproteins] were measured in lavage fluids. The infected subgroup had maximal increases in nasal lavage fluid concentrations of IL-8 (sevenfold), IgG (fourfold), total protein (twofold), and gel-phase 7F10-irm (twofold) on day 3. There were no differences between infected allergic and nonallergic subjects. IL-8 and gel-phase 7F10-irm were significantly higher in infected than in noninfected subjects. In addition to promoting plasma exudation, rhinovirus hanks infection increases IL-8 and gel-phase mucin secretion. These processes may contribute to a progression from watery rhinorrhea to mucoid discharge, with mild neutrophilic infiltration during the common cold.

Upregulation of messenger RNA for inflammatory cytokines in middle ear mucosa in a rat model of acute otitis media

A rat model for acute otitis media has been established and was used to delineate the temporal expression of messenger RNA for key inflammatory cytokines. Inoculation with live Streptococcus pneumoniae induced a rapid expression of tumor necrosis factor alpha (within 6 hours) followed by upregulation of message for interleukin (IL)-6 (peak at 12 to 24 hours, remaining elevated through 120 hours) and IL-10 (peak at 24 hours). Inducible nitric oxide synthase message was also selectively increased following live bacterial inoculation (peak at 12 to 24 hours). Although there was a detectable inflammatory response to killed bacteria, it was minimal, was of short duration, and preceded the peak for live bacteria; only expression of IL-6 was significantly increased in this group (peak at 12 hours, remaining elevated through 72 hours). We interpret this to be due to an inflammatory response to bacterial products (such as lipopolysaccharide) in the heat-killed bacterial inoculum. The phosphate-buffered saline (PBS)-inoculated group exhibited a transient increase of IL-6 message, which indicates that this cytokine is a sensitive marker of the acute response to trauma. Otherwise, PBS invoked only a slight reaction in the mucosa with respect to the other inflammatory mediators being measured.

Comparative evaluation of culture and PCR for the detection and determination of persistence of bacterial strains and DNAs in the Chinchilla laniger model of otitis media

This study was designed to determine the persistence of culturable bacteria versus DNA in the presence of a middle ear effusion in a chinchilla model of otitis media. Cohorts of animals were either infected with an ampicillin-resistant Haemophilus influenzae strain or injected with a tripartite inoculum consisting of freeze-thawed Streptococcus pneumoniae; pasteurized Moraxella catarrhalis; and DNA from H influenzae. The H influenzae-infected animals displayed culture positivity and polymerase chain reaction positivity through day 35. In the chinchillas infected with the low-copy number inocula of S pneumoniae, DNA was not detectable after day 1 from the co-inoculated pasteurized M catarrhalis bacteria or the purified H influenzae DNA; however, amplifiable DNA from the live low-copy number bacteria persisted through day 21 even though they were not culture-positive past day 3. These results demonstrate that DNA, and DNA from intact but nonviable bacteria, does not persist in an amplifiable form for more than a day in the presence of an effusion; however, live bacteria, while not culturable, persist in a viable state for weeks.

Effect of rimantadine treatment on clinical manifestations and otologic complications in adults experimentally infected with influenza A (H1N1) virus

Susceptible adults (n = 105) were enrolled into a randomized double-blind study of rimantadine treatment of experimental influenza A infection. Subjects were cloistered for 8 days and challenged with a rimantadine-sensitive strain of influenza A H1N1 virus at the end of the first day. Forty-eight hours after challenge and for 8 days, 54 subjects received placebo and 51 received rimantadine (100 mg orally, twice a day). Symptoms, signs, and pathophysiologies were monitored. Nine subjects were not infected. Seventeen subjects (38%) in the rimantadine and 26 (53%) in the placebo group became ill. A beneficial effect of rimantadine was documented for virus shedding, symptom load, and sinus pain. Rimantadine had no effect on nasal patency, mucociliary clearance, nasal signs, or on symptoms and signs of otologic complications. These results do not support a preventive effect of rimantadine on the development of otologic manifestations of influenza A infection in adults.

Types of stressors that increase susceptibility to the common cold in healthy adults

Two-hundred seventy-six volunteers completed a life stressor interview and psychological questionnaires and provided blood and urine samples. They were then inoculated with common cold viruses and monitored for the onset of disease. Although severe acute stressful life events (less than 1 month long) were not associated with developing colds, severe chronic stressors (1 month or longer) were associated with a substantial increase in risk of disease. This relation was attributable primarily to under- or unemployment and to enduring interpersonal difficulties with family or friends. The association between chronic stressors and susceptibility to colds could not be fully explained by differences among stressed and nonstressed persons in social network characteristics, personality, health practices, or prechallenge endocrine or immune measures.

Expression of acute otitis media after receptor blockade of platelet activating factor, thromboxane, and leukotrienes in the chinchilla

To determine the role of inflammatory products of phospholipid metabolism in acute otitis media (AOM), we infected 128 chinchillas with Streptococcus pneumoniae and randomly assigned them to one of four equal-sized treatment groups receiving intramuscular ampicillin sodium (control) or intramuscular ampicillin plus receptor blockers of platelet activating factor (WEB 2086, 5 mg/d orally), of leukotriene (MK 571, 0.5 mg/d orally), or of thromboxaneA2 (GR 32191B, 5 mg/d orally). All treatments were begun on day 2 postinoculation and continued for 10 days. On days 3, 6, 9, and 12, 8 animals from each group were sacrificed. Effusions were recovered for biochemical assay, and the right middle ears were prepared for histologic study. Differences among groups in the number of ears with effusion or in effusion volume were not statistically significant. In comparison to the control group, mucosal thickness and the number of ears with histopathologic signs of inflammation were significantly less in the GR and WEB treatment groups, but not the MK group. Also, effusion concentrations of free fatty acids, protease, and hydrolytic enzymes were significantly less in those groups. These results show that the addition of a receptor blocker for either platelet activating factor and/or thromboxane to ampicillin in the treatment of AOM reduces mucosal inflammation and decreases the production of other inflammatory chemicals. The failure of a receptor blocker of leukotrienes to moderate disease expression suggests either a less important role for these chemicals in AOM or an insufficient bioavailability of the specific MK 571 inhibitor. These results confirm that platelet activating factor and thromboxane are active mediators of inflammation in AOM.

Maxillary sinus mucosal blood flow during nasal vs tracheal respiration

OBJECTIVE

To determine the effect of changes from nasal to tracheal respiration on maxillary sinus mucosal blood flow in rabbits with unobstructed sinus ostia.

DESIGN

Animals underwent tracheotomy with a T tube and then a small window of intact maxillary sinus mucosa was exposed. Mucosal blood flow was recorded during normal nasal respiration using laser-Doppler velocimetry. At hourly intervals, respiration was changed from the nasal to the tracheal route and then back again.

SUBJECTS

Ten anesthetized rabbits were used: 5 underwent single and 4 underwent multiple shifts in the respiratory route, while 1 was monitored continuously during long-term nasal breathing only.

RESULTS

A significant decrease in maxillary sinus blood flow occurred on switching from nasal to tracheal respiration and a significant increase in blood flow occurred on return to nasal respiration. Where multiple switches were made, blood flow changes diminished in magnitude, but significant decreases (nasal to tracheal) or increases (tracheal to nasal) were evident in all cases.

CONCLUSIONS

It is proposed that the maxillary sinus may act in an accessory capacity to the nose for humidification of inspired air via secretions liberated from the sinus ostium. Furthermore, we suggest that nasal airflow is involved with the reflex regulation of sinus blood flow, probably via stimulation of sensory receptors in the nasal cavity. Reduced maxillary sinus mucosal blood flow may thus contribute to supra-systemic levels of antral carbon dioxide. Since elevated carbon dioxide levels have been shown to reduce maxillary sinus mucociliary activity in vitro, nasal airflow compromise may contribute to the initiation of a cascade of pathophysiological events leading to acute sinusitis.

Effects of systemic hyperoxia on eustachian tube ventilatory function

Middle ear negative pressure and effusions, decreased middle ear compliance, and abnormal tympanometry results have been described after diving on oxygen. Middle ear gas hyperoxia has been shown to down-regulate the eustachian tube ventilatory function (ETVF). The purpose of the present study was to investigate to what extent systemic hyperoxia in the face of air-equivalent middle ear gas composition might interfere with the ETVF. ETVF was investigated in four young adult female cynomolgus monkeys by the forced-response and inflation-deflation tests using air while the animals breathed either room air or 100% normobaric oxygen. Higher opening, closing, and steady-state pressures were observed under systemic hyperoxia. The percentage of the applied pressure equalized, and the maximal pressure change on a single swallow in the deflation test were both lower under hyperoxic conditions. The results show that systemic hyperoxia might impair ETVF. This observation adds to our understanding of the pathophysiology of middle ear dysfunction observed after diving on oxygen.

Increases in middle ear pressure resulting from counter-diffusion of oxygen and carbon dioxide into the middle ear of monkeys

The mechanism of middle ear (ME) pressure regulation is incompletely understood. Previously, Hergels and Magnuson reported an unexpected increase in ME pressure for human subjects who partially evacuated their relative positive ME pressures by swallowing. They suggested that a novel, but unknown mechanism for the generation of gas was responsible for the pressure increase. In this experiment, the MEs of rhesus monkeys were inflated with N2 via the eustachian tube and post inflation ME pressures were recorded for up to three hours. Eleven of 20 experiments showed an initial increase in ME pressure caused by the inflation followed by stable pressures for the remainder of the followup period. In 9 of the experiments, a rapid and temporally discrete decrease in ME pressure was observed during the course of followup. Following the observed pressure decrease which was interpreted as a transient eustachian tube opening, ME pressures showed a progressive increase characterized by a kinetic pattern similar to that of the human experiment. To understand the mechanism responsible for this effect, the monkey experiment was simulated using a mathematical model of ME pressure regulation. Free parameters of the model were taken from experimental data for monkeys. The model accurately predicted the time course of pressure change documented in the monkey experiments. The effect is driven by a decrease in the preexisting ME partial pressures of CO2, O2 and H2O consequent to tubal openings at relative positive pressures, with the subsequent counter diffusion of those gases from blood to ME causing the observed increase in total ME pressure. The results reported by Hergels and Magnuson can also be explained by this mechanism.

Magnetic resonance imaging of the development of otitis media with effusion caused by functional obstruction of the eustachian tube

In this study, magnetic resonance imaging (MRI) was used to define in vivo the effect of experimental functional obstruction of the eustachian tube (ET) on vascular permeability and the development of middle ear (ME) effusion. After collection of baseline data for ME pressure and MRI, the right tensor veli palatini muscle of 10 cynomolgus monkeys was injected with botulinum toxin A to induce ET obstruction. The left tensor veli palatini muscle was injected with saline in 4 monkeys. Right and left ME pressures and compliances were measured twice daily over a follow-up period of 36 days, and MRI scanning sessions including administration of a contrast agent, gadopentetate dimeglumine, were repeated on days 3, 6, 11, 15, 21, 29, and 36 in 6 animals and on days 15, 21, 29, and 36 in 4 animals. Two right ears did not develop underpressures, 5 developed persistent underpressures, and 3 developed underpressures that resolved. No changes in MRI parameters were noted for the ears that did not develop underpressures, but a progressive brightening of the ME on T2-weighted images, indicative of the development of inflammation and effusion, was noted for the others. Also, an increasing rate of transfer of the contrast agent between the vascular and ME compartments, indicative of increasing vascular permeability, was observed to track the temporal changes in ME pressure. These results support a causal relationship between ET dysfunction, ME underpressures, increased vascular permeability, and otitis media with effusion

Suppression of in vivo cell-mediated immunity during experimental influenza A virus infection of adults

A variety of recent evidence documents that otitis media is a frequent complication of upper respiratory tract viral infections. This relationship has been attributed to the interaction of a number of virus-provoked host responses, including eustachian tube dysfunction, changes in nasopharyngeal bacterial flora and suppressed immune function. The present study examined the effect of experimental influenza A virus infection on immune function as assessed by delayed skin test reactivity to candida, tetanus, and diphtheria/tetanus antigens in healthy adults with (n = 12) and without (n = 15) allergic rhinitis. All subjects became infected with the challenge virus as evidenced by viral shedding into nasal secretions and/or a four-fold rise in convalescent serum antibody titers compared to baseline. Intradermal skin tests were placed at baseline and 2, 4, 17, and 24 days after intranasal influenza A inoculation, the reactions were imaged and recorded 48 h after placement, and response areas were calculated by computerized digitization. The average combined areas for the three antigens (+/- S.T.D.) on each of the 5 study days were 1.4 +/- 1.4, 0.7 +/- 0.7, 0.6 +/- 0.6, 1.4 +/- 1.4, and 1.2 +/- 1.2 cm2, respectively. The responses to candida, but not tetanus and diphtheria/tetanus, returned to baseline levels by day 17. Repeated measures ANOVA documented significant effects of study day and antigen, but not allergy status. These results show that experimental influenza A infection suppressed delayed hypersensitivity skin tests in both allergic and non-allergic subjects, and suggest that alterations in immune function may contribute to otitis media.

Prechallenge antibodies: moderators of infection rate, signs, and symptoms in adults experimentally challenged with rhinovirus type 39

This study determined the influence of serum neutralizing antibody titers on infection rate, symptom manifestations, and provoked signs and pathophysiologies in adults experimentally exposed to rhinovirus type 39 (RV-39). Antibody status was determined for 151 healthy volunteers who were then cloistered in a hotel for 6 days. At the end of the first cloister day, the volunteers were challenged with RV-39 in a median tissue culture infective dose of 100. On each of the 6 days, a nasal examination was performed, symptoms were scored, and objective tests of nasal mucociliary function, nasal airway patency, secretion production, and middle ear pressures were completed. Both subjects and investigators were blinded to the prechallenge serum homotypic antibody titers of the subjects. Four subjects presented with a wild virus and were excluded from the analysis. Of the 147 included subjects, prechallenge serum antibody titers to RV-39 were low (under 2) in 56 subjects, intermediate (2 to 8) in 51 subjects, and high (above 16) in 40 subjects. The high-titer group was significantly different from the low-titer group with respect to viral shedding, symptom load, subjective extent of illness, and secretion production, as well as in the frequency of subjects with abnormal nasal mucociliary clearance and positive middle ear pressures. The study results document that for experimental RV-39 exposure, high levels of homotypic serum neutralizing antibody titers are associated with protection from infection and a lessened degree of disease expression, but not with a reduction of otologic complications.

Lower airway responses to influenza A virus in healthy allergic and nonallergic subjects

Acute asthma is considered a complication of respiratory viral infections. This investigation assessed the effects of influenza A virus infection on both the patency and responsiveness of the lower airways. Subjects with allergic rhinitis (AR; n = 21) and without AR (non-AR; n = 25) were intranasally inoculated with influenza A virus and monitored for 8 d in a cloistered environment for changes in symptoms, signs, and airway physiology (pulmonary function, bronchial methacholine provocation). All subjects were infected after inoculation. Significant increases in nasal symptoms and secretion weights were observed, with peak effects on Days 3 and 4. Cough was a relatively minor symptom, and none of the subjects developed wheezing. Likewise, there were no significant changes in the measured functions of the lower airways. No effects on allergy status were observed. Under these experimental conditions, influenza A virus infection did not produce detectable alterations in lower airway function in health AR and non-AR subjects.

Efficacy of clarithromycin treatment of acute otitis media caused by infection with penicillin-susceptible, -intermediate, and -resistant Streptococcus pneumoniae in the chinchilla

Because of the increasing frequencies of recovery of penicillin-resistant Streptococcus pneumoniae from the middle ears of children with acute otitis media, non-beta-lactam antibiotics are being explored as treatment alternatives to amoxicillin. In this study, the efficacy of a 10-day course of clarithromycin was evaluated with chinchillas. After the pharmacokinetic profiles for clarithromycin were established, 180 animals were assigned to one of three susceptibility groups (n = 60/group; penicillin-susceptible, -intermediate, and -resistant S. pneumoniae), and the right middle ear was infected with the appropriate strain of S. pneumoniae. Equal numbers of animals in each group were treated orally beginning on day 2 with a 10-day course of clarithromycin (15 mg/kg of body weight; given twice a day) or amoxicillin as a control (20 mg/kg twice a day). On days 4, 9, and 13, otomicroscopy and tympanometry were performed, and on day 13, the middle ears were cultured for bacteria. The results showed 100% eradication of the challenge organism in both treatment groups for the susceptible strains of S. pneumoniae. Cultures were negative in 87 and 74% (P > 0.05) of the animals challenged with the intermediate resistant strains and in 100 and 56% (P < 0.05) of the animals challenged with the resistant strains and treated with clarithromycin and amoxicillin, respectively. There were no differences between treatments in the diagnosis of effusion for any group. These results support the use of the chinchilla to evaluate drug efficacy in the treatment of acute otitis media and show clarithromycin to be effective in sterilizing the middle ears of animals challenged with penicillin-susceptible, -intermediate, and -resistant strains of S. pneumoniae.

Lower airway responses to rhinovirus 39 in healthy allergic and nonallergic subjects

Acute asthma is considered to be a complication of respiratory viral infections. This investigation assessed the effects of rhinovirus 39 (RV-39) infection both on the patency and responsiveness of the lower airways. Subjects with allergic rhinitis (AR; n = 50) and without AR (non-AR; n = 46) were intranasally inoculated with RV-39, and monitored for 8 days in an enclosed environment for changes in symptoms, signs, and airway physiology (pulmonary function, bronchial methacholine provocation). All subjects were infected postinoculation. Significant increases in nasal symptoms and secretion weights were observed, with peak effects on days 2-3. Cough was a relatively minor symptom and none of the subjects developed wheezing. Likewise, there were no significant changes in the measured functions of the lower airways. No allergy status effects were observed. Under these experimental conditions, rhinovirus 39 infection did not produce detectable alterations in lower airway function in healthy subjects with and without allergic rhinitis.

Effect of influenza A virus infection on natural and adaptive cellular immunity

Influenza A virus (FLU) is an important pathogen in humans. Although many features of the antiviral immune response have been elucidated in murine and human models of disease, little is known about the role of NK cells, which provide natural, innate immunity. The effects of experimental intranasal FLU (H1N1) inoculation on NK cells and other immune parameters were studied in 18 healthy, adult volunteers during the acute and convalescent phases of infection. Peripheral blood mononuclear cells (PBMNC) were assayed at baseline and on Postinoculation Days 1, 3, 4, 6, 7, 23, and 44. FLU infection and pathophysiologic upper airway responses were documented in all subjects, and there was no mortality. During both the acute (Days 1-3) and the convalescent (Days 23 and 44) stages of the FLU infection, significant increases in NK activity and decreases in the number of activated NK cells were observed. Reductions in the absolute number of T lymphocytes and in PBMNC proliferation to FLU virus antigen and mitogen were also observed. The current investigation extended those findings to include reductions in the number of CD4+ and CD8+ T lymphocytes and increases in the number of activated T lymphocytes. These results document that FLU infection was accompanied by enhancement of natural immunity and, as expected, suppression of most of the other measured parameters of cellular immunity. The normal response to FLU infection in humans may involve sequential modulation of the different components of the cellular immune system.

PCR-based detection of bacterial DNA after antimicrobial treatment is indicative of persistent, viable bacteria in the chinchilla model of otitis media

PURPOSE

Bacterial deoxyribonucleic acid (DNA) has been previously detected by polymerase chain reactions (PCR) in a significant percentage of culturally-sterile pediatric middle-ear effusions. The current study was designed to determine whether this represents the existence of viable bacteria or the persistence of residual DNA in the middle-ear cleft.

MATERIALS AND METHODS

The middle-ear cavities of two sets of chinchillas were inoculated with either: 1) 100 colony-forming units (CFU) of live Haemophilus influenzae, 2.2 x 10(6) CFU of pasteurized Moraxella catarrhalis, and 1000 ng of DNA (>10(8) genomic equivalents) from Streptococcus pneumoniae; or 2) 100 CFU of live S pneumoniae, 2.2 x 10(6) CFU of pasteurized M catarrhalis and 1000 ng of purified DNA from H influenzae. Animals were treated with ampicillin for 5 days beginning on day 3. A single-point longitudinal study design was used for sampling to eliminate the possibility of contamination.

RESULTS

No DNA was detectable from the heat-killed bacteria or the purified DNA after day 3. However, DNA from the live bacteria persisted through day 21, even though all specimens were culture-negative following the initiation of antimicrobial therapy.

CONCLUSION

These findings indicate that purified DNA and DNA from intact but nonviable bacteria do not persist in the middle-ear cleft in the presence of an effusion, even following high copy inoculation. In contrast, antibiotic-treated bacteria persist in some viable state for weeks as evidenced by the differential ability of the PCR-based assay systems to detect the live bacteria, but not detect the heat-killed organisms.