Enhanced allergic responsiveness after early childhood infection with respiratory viruses: Are long-lived alternatively activated macrophages the missing link?

Early childhood infection with respiratory viruses, including human rhinovirus, respiratory syncytial virus (RSV) and influenza, is associated with an increased risk of allergic asthma and severe exacerbation of ongoing disease. Despite the long recognition of this relationship, the mechanism linking viral infection and later susceptibility to allergic lung inflammation is still poorly understood. We discuss the literature and provide new evidence demonstrating that these viruses induce the alternative activation of macrophages. Alternatively activated macrophages (AAM) induced by RSV or influenza infection persisted in the lungs of mice up to 90 days after initial viral infection. Several studies suggest that AAM contribute to allergic inflammatory responses, although their mechanism of action is unclear. In this commentary, we propose that virus-induced AAM provide a link between viral infection and enhanced responses to inhaled allergens.

Antenatal factors modulate hearing screen failure risk in preterm infants.

OBJECTIVE: The objective of this study was to characterise the effects of antenatal inflammatory factors and maternal therapies on neonatal hearing screen outcomes in very low birthweight infants. METHODS: We conducted a retrospective study of a cohort of infants <33 weeks' gestational age and <1501 g birth weight prospectively enrolled between 1999 and 2003 for whom placental pathology, cord blood interleukin (IL) 6, IL-1ß, tumour necrosis factor-α and neonatal hearing screen results were available. RESULTS: Of 289 infants with documented hearing screen results, 244 (84%) passed and 45 (16%) failed the hearing screen (unilateral, N=25 (56%); bilateral, N=20 (44%)). In the final logistic model, the fetal inflammatory response syndrome defined as the presence of fetal vasculitis and/or cord serum IL-6>18.2 pg/mL was the factor with greatest risk for hearing screen failure (OR 3.62, 95% CI 1.38 to 9.5). A patent ductus arteriosus treated with indomethacin significantly increased the risk (OR 3.3, 95% CI 1.3 to 8.26), while combined maternal steroid and magnesium sulfate exposure (0.37, 95% CI 0.11 to 0.81) reduced the risk for hearing screen failure. CONCLUSIONS: Intrauterine infection with a fetal inflammatory response is a risk factor for neonatal hearing loss while maternal therapies significantly reduced the risk of neonatal hearing loss in very low birthweight infants.

Pharmacokinetics, microbial response, and pulmonary outcomes of multidose intravenous azithromycin in preterm infants at risk for Ureaplasma respiratory colonization.

The study objectives were to refine the population pharmacokinetics (PK) model, determine microbial clearance, and assess short-term pulmonary outcomes of multiple-dose azithromycin treatment in preterm infants at risk for Ureaplasma respiratory colonization. Fifteen subjects (7 of whom were Ureaplasma positive) received intravenous azithromycin at 20 mg/kg of body weight every 24 h for 3 doses. Azithromycin concentrations were determined in plasma samples obtained up to 168 h post-first dose by using a validated liquid chromatography-tandem mass spectrometry method. Respiratory samples were obtained predose and at three time points post-last dose for Ureaplasma culture, PCR, antibiotic susceptibility testing, and cytokine concentration determinations. Pharmacokinetic data from these 15 subjects as well as 25 additional subjects (who received either a single 10-mg/kg dose [n = 12] or a single 20-mg/kg dose [n = 13]) were analyzed by using a nonlinear mixed-effect population modeling (NONMEM) approach. Pulmonary outcomes were assessed at 36 weeks post-menstrual age and 6 months adjusted age. A 2-compartment model with all PK parameters allometrically scaled on body weight best described the azithromycin pharmacokinetics in preterm neonates. The population pharmacokinetics parameter estimates for clearance, central volume of distribution, intercompartmental clearance, and peripheral volume of distribution were 0.15 liters/h · kg(0.75), 1.88 liters · kg, 1.79 liters/h · kg(0.75), and 13 liters · kg, respectively. The estimated area under the concentration-time curve over 24 h (AUC24)/MIC90 value was ∼ 4 h. All posttreatment cultures were negative, and there were no drug-related adverse events. One Ureaplasma-positive infant died at 4 months of age, but no survivors were hospitalized for respiratory etiologies during the first 6 months (adjusted age). Thus, a 3-day course of 20 mg/kg/day intravenous azithromycin shows preliminary efficacy in eradicating Ureaplasma spp. from the preterm respiratory tract.

Single nucleotide polymorphism in toll-like receptor 6 is associated with a decreased risk for ureaplasma respiratory tract colonization and bronchopulmonary dysplasia in preterm infants.

BACKGROUND: Ureaplasma spp. respiratory tract colonization is a risk factor for bronchopulmonary dysplasia (BPD) in preterm infants, but differences in host susceptibility have not been elucidated. We hypothesized that variants in genes regulating the innate immune response are associated with altered risk for Ureaplasma spp. respiratory colonization and BPD in preterm infants. METHODS: Twenty-four tag single nucleotide polymorphisms (SNPs) from Toll-like receptor (TLR)1, TLR2, TLR4 and TLR6 were assayed in 298 infants <33 weeks gestation who had serial respiratory cultures for Ureaplasma spp. and were evaluated for BPD. RESULTS: The majority of subjects (N = 205 [70%]) were African-American. One hundred ten (37%) were Ureaplasma positive. Four SNPs in TLR2 and TLR6 were significantly associated with Ureaplasma respiratory tract colonization. Single SNPs in TLR2, TLR4 and TLR6 were associated with BPD. TLR6 SNP rs5743827 was associated with both a decreased risk for Ureaplasma respiratory tract colonization and decreased risk for BPD (odds ratio: 0.54 [0.34-0.86] and odds ratio: 0.54 [0.31-0.95], respectively). There was a significant additive interaction between Ureaplasma colonization and genotype at TLR6 SNP rs5743827 (Padditive = 0.023), with an attributable proportion due to interaction of 0.542. CONCLUSIONS: Polymorphisms in host defense genes may alter susceptibility to Ureaplasma infection and severity of the inflammatory response contributing to BPD. These observations implicate host genetic susceptibility as a major factor in BPD pathogenesis in Ureaplasma-infected preterms.

Azithromycin to prevent bronchopulmonary dysplasia in ureaplasma-infected preterm infants: pharmacokinetics, safety, microbial response, and clinical outcomes with a 20-milligram-per-kilogram single intravenous dose.

Ureaplasma respiratory tract colonization is associated with bronchopulmonary dysplasia (BPD) in preterm infants. Previously, we demonstrated that a single intravenous (i.v.) dose of azithromycin (10 mg/kg of body weight) is safe but inadequate to eradicate Ureaplasma spp. in preterm infants. We performed a nonrandomized, single-arm open-label study of the pharmacokinetics (PK) and safety of intravenous 20-mg/kg single-dose azithromycin in 13 mechanically ventilated neonates with a gestational age between 24 weeks 0 days and 28 weeks 6 days. Pharmacokinetic data from 25 neonates (12 dosed with 10 mg/kg i.v. and 13 dosed with 20 mg/kg i.v.) were analyzed using a population modeling approach. Using a two-compartment model with allometric scaling of parameters on body weight (WT), the population PK parameter estimates were as follows: clearance, 0.21 liter/h × WT(kg)(0.75) [WT(kg)(0.75) indicates that clearance was allometrically scaled on body weight (in kilograms) with a fixed exponent of 0.75]; intercompartmental clearance, 2.1 liters/h × WT(kg)(0.75); central volume of distribution (V), 1.97 liters × WT (kg); and peripheral V, 17.9 liters × WT (kg). There was no evidence of departure from dose proportionality in azithromycin exposure over the tested dose range. The calculated area under the concentration-time curve over 24 h in the steady state divided by the MIC90 (AUC24/MIC90) for the single dose of azithromycin (20 mg/kg) was 7.5 h. Simulations suggest that 20 mg/kg for 3 days will maintain azithromycin concentrations of >MIC50 of 1 µg/ml for this group of Ureaplasma isolates for ≥ 96 h after the first dose. Azithromycin was well tolerated with no drug-related adverse events. One of seven (14%) Ureaplasma-positive subjects and three of six (50%) Ureaplasma-negative subjects developed physiologic BPD. Ureaplasma was eradicated in all treated Ureaplasma-positive subjects. Simulations suggest that a multiple-dose regimen may be efficacious for microbial clearance, but the effect on BPD remains to be determined.

Role of biofilm formation in Ureaplasma antibiotic susceptibility and development of bronchopulmonary dysplasia in preterm neonates.

BACKGROUND: Ureaplasma respiratory tract colonization is a risk factor for bronchopulmonary dysplasia (BPD) in preterm infants, but whether Ureaplasma isolates from colonized infants can form biofilms is unknown. We hypothesized that Ureaplasma isolates vary in capacity to form biofilms that contribute to their antibiotic resistance and ability to evade host immune responses. Study objectives were to (1) determine the ability of Ureaplasma isolates from preterm neonates to form biofilms in vitro; (2) compare the susceptibility of the sessile and planktonic organisms to azithromycin (AZI) and erythromycin; and (3) determine the relationship of biofilm-forming capacity in Ureaplasma isolates and the risk for BPD. METHODS: Forty-three clinical isolates from preterm neonates and 5 American Tissue Culture Collection strains were characterized for their capacity to form biofilms in vitro, and antibiotic susceptibility was performed on each isolate prebiofilm and postbiofilm formation. RESULTS: Forty-one (95%) clinical and 4 of 5 (80%) American Tissue Culture Collection isolates formed biofilms. All isolates were more susceptible to AZI (minimum inhibitory concentration, MIC50 2 µg/mL) than erythromycin (MIC50 4 µg/mL), and biofilm formation did not significantly affect antibiotic susceptibility for the 2 tested antibiotics. The MIC50 and minimum biofilm inhibitory concentrations (MBIC50) for Ureaplasma urealyticum clinical isolates for AZI were higher than for MIC50 and MBIC50 for Ureaplasma parvum isolates. There were no differences in MIC or MBICs among isolates from BPD infants and non-BPD infants. CONCLUSIONS: Capacity to form biofilms is common among Ureaplasma spp. isolates, but biofilm formation did not impact MICs for AZI or erythromycin.

IL-18R1 and IL-18RAP SNPs may be associated with bronchopulmonary dysplasia in African-American infants.

INTRODUCTION: The genetic contribution to the development of bronchopulmonary dysplasia (BPD) in prematurely born infants is substantial, but information related to the specific genes involved is lacking. RESULTS: Genotype analysis revealed, after multiple comparisons correction, two significant single-nucleotide polymorphism (SNPs), rs3771150 (IL-18RAP) and rs3771171 (IL-18R1), in African Americans (AAs) with BPD (vs. AAs without BPD; q < 0.05). No associations with Caucasian (CA) BPD, AA or CA respiratory distress syndrome (RDS), or prematurity in either AAs or CAs were identified with these SNPs. Respective frequencies were 0.098 and 0.093 in infants without BPD and 0.38 for each SNP in infants with BPD. In the replication set (82 cases; 102 controls), the P values were 0.012 for rs3771150 and 0.07 for rs3771171. Combining P values using Fisher's method, overall P values were 8.31 × 10(-7) for rs3771150 and 6.33 × 10(-6) for rs3771171. DISCUSSION: We conclude that IL-18RAP and IL-18R1 SNPs identify AA infants at risk for BPD. These genes may contribute to AA BPD pathogenesis via inflammatory-mediated processes and require further study. METHODS: We conducted a case-control SNP association study of candidate genes (n = 601) or 6,324 SNPs in 1,091 prematurely born infants with gestational age <35 weeks, with or without neonatal lung disease including BPD. BPD was defined as a need for oxygen at 28 days.

NICU admission hypothermia, chorioamnionitis, and cytokines.

OBJECTIVE: To determine whether neonatal intensive care unit (NICU) admission hypothermia is associated with an intrauterine inflammatory response. METHODS: We analyzed a cohort of 309 very low birthweight infants to determine relationships between admission hypothermia, chorioamnionitis, and serum and cerebrospinal fluid (CSF) interleukin (IL)-1ß, IL-6, and tumor necrosis factor-α. RESULTS: Admission hypothermia <36°C occurred in 72% of patients <26 weeks and 44% of patients ≥26 weeks gestational age. NICU admission hypothermia was not associated with histologic chorioamnionitis or with elevated serum cytokine concentrations. CSF IL-6 concentrations ≥6.3 pg/mL were associated with admission hypothermia in infants <26 weeks' gestation. Clinical chorioamnionitis was associated with a lower risk of admission hypothermia, while cesarean section delivery was associated with increased risk. CONCLUSIONS: NICU admission hypothermia is common among preterm infants and is not associated with the fetal inflammatory response syndrome. Hypothermia is less common in the setting of clinical chorioamnionitis and more common in cesarean section deliveries, identifying two groups in whom extra attention to appropriate thermoregulation is warranted.

Surfactant protein-A enhances ureaplasmacidal activity in vitro.

BACKGROUND: Persistent respiratory tract colonization with Ureaplasma spp. in preterm infants is a significant risk factor for the development of the chronic lung disorder, bronchopulmonary dysplasia (BPD). Surfactant protein-A (SP-A), a lung collectin critical for bacterial clearance and regulating inflammation, is deficient in the preterm lung. In an experimental Ureaplasma-pneumonia model, infected SP-A deficient mice exhibited delayed bacterial clearance and an exaggerated inflammatory response compared to infected wild-type mice. The objective was to analyze the role of SP-A in Ureaplasma clearance in vitro. SUBJECTS AND METHODS: We analyzed SP-A binding to Ureaplasma isolates and SP-A-mediated ureaplasmal phagocytosis and killing by cultured RAW 264.7 macrophages. RESULTS: Calcium-dependent SP-A binding was similar among Ureaplasma isolates tested. Pre-incubation of RAW 264.7 cells with SP-A (10-50 µg/ml) enhanced phagocytosis of fluorescein-isothiocyanate (FITC)-labeled Ureaplasma. Surfactant protein-A also increased ureaplasmacidal activity of RAW 264.7 cells by 2.1-fold over 4 h. Pre-incubation of RAW 264.7 cells with 10 µg/ml SP-A reduced lipopolysaccharide (LPS) (100 ng/ml) and Ureaplasma (10(6) color changing units/ml)-stimulated release of tumor necrosis factor-α (TNF-α) by 46% and 43%, respectively, but did not affect transforming growth factor ß(1) (TGFß(1)) release. CONCLUSIONS: These in vitro data confirm that SP-A is important in host defense to perinatally-acquired Ureaplasma infection.

Pharmacokinetics, safety, and biologic effects of azithromycin in extremely preterm infants at risk for ureaplasma colonization and bronchopulmonary dysplasia.

Ureaplasma spp. respiratory tract colonization is a significant risk factor for bronchopulmonary dysplasia (BPD), a chronic lung disorder in preterm infants. As an initial step preparatory to future clinical trials to evaluate the clinical efficacy of azithromycin to prevent BPD, the authors characterized the pharmacokinetics, safety, and biological effects of a single intravenous dose of azithromycin (10 mg/kg) in preterm neonates (n = 12) 24 to 28 weeks gestation at risk for Ureaplasma infection and BPD. A 2-compartment structural model with the clearance and volume of peripheral compartment (V2) allometrically scaled on body weight (WT) best described the pharmacokinetics of azithromycin in preterm neonates. The estimated parameters were clearance [0.18 L/h × WT(kg)(0.75)], intercompartmental clearance [1.0 L/h], volume of distribution of central compartment [0.93 L], and V2 [14.2 L × WT(kg)]. There were no serious adverse events attributed to azithromycin. A single dose of azithromycin did not suppress inflammatory cytokines or myeloperoxidase activity in tracheal aspirates. These results demonstrated the safety of azithromycin and developed a pharmacokinetic model that is useful for future simulation-based clinical trials for eradicating Ureaplasma and preventing BPD in preterm neonates.

Frequency of ureaplasma serovars in respiratory secretions of preterm infants at risk for bronchopulmonary dysplasia.

OBJECTIVE: Ureaplasma respiratory tract colonization is associated with bronchopulmonary dysplasia (BPD) in preterm infants. Whether the 4 Ureaplasma parvum and 10 Ureaplasma urealyticum serovars differ in virulence is unknown. This study was conducted to determine the distribution of Ureaplasma serovars in respiratory secretions of a prospective cohort of preterm infants and to assess whether any of the serovars are associated with BPD. METHODS: Serial endotracheal and/or nasopharyngeal aspirates were obtained for Ureaplasma culture and PCR from 136 infants of gestational age <33 weeks. All positive samples were speciated and serovars were determined by real-time PCR. RESULTS: A total of 51 (37.5%) infants were Ureaplasma-positive one or more times during the first month of life. Respiratory colonization was inversely related to gestational age. Sixty-five percent of infants <26 weeks compared with 31% infants ≥ 26 weeks were culture or PCR positive. U. parvum was more common (N = 32, 63%) than U. urealyticum (N = 17, 33%); both species were present in 2 samples. Serovars 3 and 6 alone and in combination accounted for 96% U. parvum isolates. U. urealyticum isolates were commonly a mixture of multiple serovars, with serovar 11 alone or combined with other serovars (10/17, 59%) being the most common serovar. No individual species or serovars or serovar mixtures were associated with moderate-to-severe BPD. CONCLUSIONS: U. parvum serovars 3 and 6 and U. urealyticum serovar 11 were the most common serovars detected in respiratory samples from a prospective cohort of preterm infants.

Ureaplasma species: role in diseases of prematurity.

There is accumulating epidemiologic and experimental evidence that intrauterine or postnatal infection with Ureaplasma species is a significant risk factor for adverse pregnancy outcomes and complications of extreme preterm birth such as bronchopulmonary dysplasia and intraventricular hemorrhage. In a cohort of very low birth weight infants, Ureaplasma spp were detected by culture or polymerase chain reaction in respiratory secretions, blood, or cerebrospinal fluid of almost half of the subjects, suggesting that this organism is the most common pathogen affecting this population. This review summarizes the evidence supporting the hypothesis that Ureaplasma-mediated inflammation in different compartments (intrauterine, lung, blood, or brain) during a common developmental window of vulnerability contributes to preterm labor and lung and brain injury. Appropriate methods for detecting these fastidious organisms and potential strategies to prevent or ameliorate the effects of Ureaplasma infection are discussed.

Surfactant protein-A limits Ureaplasma-mediated lung inflammation in a murine pneumonia model.

Ureaplasma respiratory tract colonization stimulates prolonged, dysregulated inflammation in the lungs of preterm infants, contributing to bronchopulmonary dysplasia (BPD) pathogenesis. Surfactant protein-A (SP-A), a lung collectin critical for bacterial clearance and regulating inflammation, is deficient in the preterm lung. To analyze the role of SP-A in modulating Ureaplasma-mediated lung inflammation, SP-A deficient (SP-A-/-) and WT mice were inoculated intratracheally with a mouse-adapted U. parvum isolate and indices of inflammation were sequentially assessed up to 28 d postinoculation. Compared with infected WT and noninfected controls, Ureaplasma-infected SP-A-/- mice exhibited an exaggerated inflammatory response evidenced by rapid influx of neutrophils and macrophages into the lung, and higher bronchoalveolar lavage TNF-alpha, mouse analogue of human growth-related protein alpha (KC), and monocyte chemotactic factor (MCP-1) concentrations. However, nitrite generation in response to Ureaplasma infection was blunted at 24 h and Ureaplasma clearance was delayed in SP-A-/- mice compared with WT mice. Coadministration of human SP-A with the Ureaplasma inoculum to SP-A-/- mice reduced the inflammatory response, but did not improve the bacterial clearance rate. SP-A deficiency may contribute to the prolonged inflammatory response in the Ureaplasma-infected preterm lung, but other factors may contribute to the impaired Ureaplasma clearance.

Antenatal Ureaplasma urealyticum respiratory tract infection stimulates proinflammatory, profibrotic responses in the preterm baboon lung.

Chronic inflammation and fibrosis are hallmarks of lung pathology of newborn Ureaplasma infection. We hypothesized that antenatally acquired Ureaplasma stimulates a chronic inflammatory, profibrotic immune response that contributes to lung injury, altered developmental signaling, and fibrosis. Lung specimens from 125-d gestation baboon newborns ventilated for 14 d that were either infected antenatally with Ureaplasma serovar 1 or noninfected, and 125-d and 140-d gestational controls were obtained from the Baboon BPD Resource Center (San Antonio, TX). Trichrome stain to assess fibrosis and immunohistochemistry for alpha-smooth muscle actin (alpha-SMA) and transforming growth factor beta1 (TGFbeta1) were performed. Lung homogenates were analyzed by enzyme-linked immunosorbent assay (ELISA) for cytokines [tumor necrosis factor alpha (TNFalpha), interleukin (IL)-1beta, TGFbeta1, oncostatin M (OSM), IL-10, and interferon gamma (IFNgamma)] and the chemokine MCP-1 and by Western blot for Smad2, Smad3, and Smad7. Compared with noninfected ventilated and gestational controls, Ureaplasma-infected lungs demonstrated more extensive fibrosis, increased alpha-SMA and TGFbeta1 immunostaining, and higher concentrations of active TGFbeta1, IL-1beta, and OSM, but no difference in IL-10 levels. There was a trend toward higher Smad2/Smad7 and Smad3/Smad7 ratios in Ureaplasma lung homogenates, consistent with up-regulation of TGFbeta1 signaling. Collectively, these data suggest that a prolonged proinflammatory response initiated by intrauterine Ureaplasma infection contributes to early fibrosis and altered developmental signaling in the immature lung.

Inflammatory markers in intrauterine and fetal blood and cerebrospinal fluid compartments are associated with adverse pulmonary and neurologic outcomes in preterm infants.

Recent evidence strongly implicates the inflammatory response to intrauterine infection in the pathogenesis of neonatal brain and lung injury. We hypothesized that lung and brain injury in preterm infants occurs during a common developmental window of vulnerability as the result of an inflammatory response in different compartments. To determine whether inflammatory markers in these compartments are associated with bronchopulmonary dysplasia (BPD) or cranial ultrasound (CUS) abnormalities in infants <33 wk gestation age (GA) and <1501 g birth weight, we analyzed placental pathology and serum and cerebrospinal fluid (CSF) IL-6, IL-1beta, and tumor necrosis factor-alpha (TNF-alpha) concentrations in 276 infants. Logistic regressions were performed stratified by GA. Histologic chorioamnionitis was significantly associated with BPD in infants /=17 pg/mL was associated with an abnormal CUS in infants >28 wk GA (OR 3.36, p = 0.023) but not /=6.5 pg/mL and TNF-alpha >/=3 pg/mL were associated with abnormal CUS in infants /=28 wk GA. These data suggest that in infants

Hypothermia prolongs activation of NF-kappaB and augments generation of inflammatory cytokines.

While moderate hypothermia is protective against ischemic cardiac and brain injury, it is associated with much higher mortality in patients with sepsis. We previously showed that in vitro exposure to moderate hypothermia (32 degrees C) delays the induction and prolongs the duration of TNF-alpha and IL-1beta secretion by lipopolysaccharide (LPS)-stimulated human mononuclear phagocytes. In the present study, we extended these observations by showing that moderate hypothermia exerts effects on TNF-alpha and IL-1beta generation in the human THP-1 monocyte cell line that are similar to those that we previously found in primary cultured monocytes; that hypothermia causes comparable changes in cytokine generation stimulated by zymosan, toxic shock syndrome toxin-1, and LPS; and that hypothermia causes similar changes in TNF-alpha and IL-1beta mRNA accumulation. TNF-alpha mRNA half-life, determined after transcriptional arrest with actinomycin D, was not significantly prolonged by lowering incubation temperature from 37 to 32 degrees C, suggesting that hypothermia modifies TNF-alpha gene transcription. This finding was further supported by reporter gene studies showing a threefold increase in activity of the human TNF-alpha promoter at 32 vs. 37 degrees C. Electrophoretic mobility shift assay revealed that hypothermia prolonged NF-kappaBeta activation, identifying a potential role for this transcription factor in mediating the effects of hypothermia on TNF-alpha and IL-1beta production. Delayed reexpression of the inhibitor IkappaBalpha, shown by Northern blotting and immunoblotting, may account in part for the prolonged NF-kappaBeta activation at 32 degrees C. Augmentation of NF-kappaBeta-dependent gene expression during prolonged exposure to hypothermia may be a common mechanism leading to increased lethality in sepsis, late-onset systemic inflammatory response syndrome after accidental hypothermia, and neuroprotection after ischemia.

Characterization of a murine model of Ureaplasma urealyticum pneumonia.

Ureaplasma urealyticum respiratory tract colonization in preterm infants has been associated with a high incidence of pneumonia and the development of bronchopulmonary dysplasia. However, study of this human pathogen has been hampered by the absence of animal models. We have developed the first juvenile mouse model of Ureaplasma pneumonia and characterized the histopathology during the month following inoculation. C3H/HeN mice were inoculated intratracheally with a mouse-adapted clinical Ureaplasma isolate (biovar 2) or sham inoculated with 10B broth. Culture of lung homogenates and PCR of DNA from bronchoalveolar lavage fluid (BAL) confirmed the presence of Ureaplasma in 100% of inoculated animals at 1 day, 60% at 2 days, 50% at 3 days, and 25% at 7 and 14 days. Ureaplasma was undetectable 28 days postinoculation. There were marked changes in BAL and interstitial-cell composition with increased number of polymorphonuclear leukocytes 1 to 2 days and 14 days postinoculation and macrophages at 2 and 14 days postinoculation. The Ureaplasma infection caused a persistent focal loss of airway ciliated epithelium and a mild increase in interstitial cellularity. There were no differences in BAL protein concentration during the first 28 days, suggesting that pulmonary vascular endothelial barrier integrity remained intact. Comparison of BAL cytokine and chemokine concentrations revealed low levels of tumor necrosis factor alpha (TNF-alpha) at 3 days and monocyte chemoattractant protein 1 at 7 days in Ureaplasma-infected mice but a trend toward increased TNF-alpha at 14 days and increased granulocyte-macrophage colony-stimulating factor and interleukin-10 at 28 days. These data suggest that Ureaplasma alone may cause limited inflammation and minimal tissue injury in the early phase of infection but may promote a mild chronic inflammatory response in the later phase of infection (days 14 to 28), similar to the process that occurs in human newborns.

Lung pathology in premature infants with Ureaplasma urealyticum infection.

Respiratory tract colonization with Ureaplasma urealyticum in preterm infants has been associated with a higher incidence of pneumonia, severe respiratory failure, bronchopulmonary dysplasia (BPD), and death. In this report, we characterize the lung pathology and expression of tumor necrosis factor-alpha (TNF-alpha) associated with U. urealyticum pneumonia in very low-birth weight infants (VLBW; < or =1500 g). Lung pathology of archived autopsy specimens was retrospectively reviewed in three groups of VLBW infants: 5 gestational controls who died from nonpulmonary causes, 13 infants with pneumonia who were culture and/or PCR negative for U. urealyticum, and 5 infants with pulmonary disease and positive for U. urealyticum by tracheal aspirate and/or lung tissue culture or polymerase chain reaction (PCR). Presence and extent of alveolar macrophages and neutrophils, as well as interstitial lymphocytic infiltration and fibrosis were evaluated. PCR was performed on formalin-fixed, paraffin-embedded lung sections. Additional sections were immunostained for TNF-alpha. The peripheral total white blood cell counts and absolute neutrophil counts were three-fold higher in infants with U. urealyticum pneumonia than cell counts in infants infected with other organisms. There was a trend toward a predominance of neutrophils in alveoli of non- Ureaplasma pneumonia infants, but a trend toward a predominance of alveolar macrophages in U. urealyticum-infected infants. The most striking finding was the presence of increased interstitial fibrosis in all Ureaplasma-infected infants. TNF-alpha immunoreactive cell density was very low in the gestational controls, but increased in both pneumonia groups. We conclude that persistent lung U. urealyticum infection may contribute to chronic inflammation and early fibrosis in the preterm lung.