Cytomegalovirus infection disrupts the influence of short-chain fatty acid producers on Treg/Th17 balance

BACKGROUND

Both the gut microbiota and chronic viral infections have profound effects on host immunity, but interactions between these influences have been only superficially explored. Cytomegalovirus (CMV), for example, infects approximately 80% of people globally and drives significant changes in immune cells. Similarly, certain gut-resident bacteria affect T-cell development in mice and nonhuman primates. It is unknown if changes imposed by CMV on the intestinal microbiome contribute to immunologic effects of the infection.

RESULTS

We show that rhesus cytomegalovirus (RhCMV) infection is associated with specific differences in gut microbiota composition, including decreased abundance of Firmicutes, and that the extent of microbial change was associated with immunologic changes including the proliferation, differentiation, and cytokine production of CD8+ T cells. Furthermore, RhCMV infection disrupted the relationship between short-chain fatty acid producers and Treg/Th17 balance observed in seronegative animals, showing that some immunologic effects of CMV are due to disruption of previously existing host-microbe relationships.

CONCLUSIONS

Gut microbes have an important influence on health and disease. Diet is known to shape the microbiota, but the influence of concomitant chronic viral infections is unclear. We found that CMV influences gut microbiota composition to an extent that is correlated with immunologic changes in the host. Additionally, pre-existing correlations between immunophenotypes and gut microbes can be subverted by CMV infection. Immunologic effects of CMV infection on the host may therefore be mediated by two different mechanisms involving gut microbiota. Video Abstract.

Early Life Wildfire Smoke Exposure Is Associated with Immune Dysregulation and Lung Function Decrements in Adolescence

The long-term health effects of wildfire smoke exposure in pediatric populations are not known. The objectives of this study were to determine if early life exposure to wildfire smoke can affect parameters of immunity and airway physiology that are detectable with maturity. We studied a mixed-sex cohort of rhesus macaque monkeys that were exposed as infants to ambient wood smoke from a series of Northern California wildfires in the summer of 2008. Peripheral blood mononuclear cells (PBMCs) and pulmonary function measures were obtained when animals were approximately 3 years of age. PBMCs were cultured with either LPS or flagellin, followed by measurement of secreted IL-8 and IL-6 protein. PBMCs from a subset of female animals were also evaluated by Toll-like receptor (TLR) pathway mRNA analysis. Induction of IL-8 protein synthesis with either LPS or flagellin was significantly reduced in PBMC cultures from wildfire smoke-exposed female monkeys. In contrast, LPS- or flagellin-induced IL-6 protein synthesis was significantly reduced in PBMC cultures from wildfire smoke-exposed male monkeys. Baseline and TLR ligand-induced expression of the transcription factor, RelB, was globally modulated in PBMCs from wildfire smoke-exposed monkeys, with additional TLR pathway genes affected in a ligand-dependent manner. Wildfire smoke-exposed monkeys displayed significantly reduced inspiratory capacity, residual volume, vital capacity, functional residual capacity, and total lung capacity per unit of body weight relative to control animals. Our findings suggest that ambient wildfire smoke exposure during infancy results in sex-dependent attenuation of systemic TLR responses and reduced lung volume in adolescence.

Early life allergen and air pollutant exposures alter longitudinal blood immune profiles in infant rhesus monkeys

Early life is a critical period for the progressive establishment of immunity in response to environmental stimuli; the impact of airborne challenges on this process is not well defined. In a longitudinal fashion, we determined the effect of episodic house dust mite (HDM) aerosol and ozone inhalation, both separately and combined, on peripheral blood immune cell phenotypes and cytokine expression from 4 to 25weeks of age in an infant rhesus monkey model of childhood development. Immune profiles in peripheral blood were compared with lung lavage at 25weeks of age. Independent of exposure, peripheral blood cell counts fluctuated with chronologic age of animals, while IFNγ and IL-4 mRNA levels increased over time in a linear fashion. At 12weeks of age, total WBC, lymphocyte numbers, FoxP3 mRNA and IL-12 mRNA were dramatically reduced relative to earlier time points, but increased to a steady state with age. Exposure effects were observed for monocyte numbers, as well as CCR3, FoxP3, and IL-12 mRNA levels in peripheral blood. Significant differences in cell surface marker and cytokine expression were detected following in vitro HDM or PMA/ionomycin stimulation of PBMC isolated from animals exposed to either HDM or ozone. Lavage revealed a mixed immune phenotype of FoxP3, IFNγ and eosinophilia in association with combined HDM plus ozone exposure, which was not observed in blood. Collectively, our findings show that airborne challenges during postnatal development elicit measureable cell and cytokine changes in peripheral blood over time, but exposure-induced immune profiles are not mirrored in the lung.

Early life ozone exposure results in dysregulated innate immune function and altered microRNA expression in airway epithelium

Exposure to ozone has been associated with increased incidence of respiratory morbidity in humans; however the mechanism(s) behind the enhancement of susceptibility are unclear. We have previously reported that exposure to episodic ozone during postnatal development results in an attenuated peripheral blood cytokine response to lipopolysaccharide (LPS) that persists with maturity. As the lung is closely interfaced with the external environment, we hypothesized that the conducting airway epithelium of neonates may also be a target of immunomodulation by ozone. To test this hypothesis, we evaluated primary airway epithelial cell cultures derived from juvenile rhesus macaque monkeys with a prior history of episodic postnatal ozone exposure. Innate immune function was measured by expression of the proinflammatory cytokines IL-6 and IL-8 in primary cultures established following in vivo LPS challenge or, in response to in vitro LPS treatment. Postnatal ozone exposure resulted in significantly attenuated IL-6 mRNA and protein expression in primary cultures from juvenile animals; IL-8 mRNA was also significantly reduced. The effect of antecedent ozone exposure was modulated by in vivo LPS challenge, as primary cultures exhibited enhanced cytokine expression upon secondary in vitro LPS treatment. Assessment of potential IL-6-targeting microRNAs miR-149, miR-202, and miR-410 showed differential expression in primary cultures based upon animal exposure history. Functional assays revealed that miR-149 is capable of binding to the IL-6 3' UTR and decreasing IL-6 protein synthesis in airway epithelial cell lines. Cumulatively, our findings suggest that episodic ozone during early life contributes to the molecular programming of airway epithelium, such that memory from prior exposures is retained in the form of a dysregulated IL-6 and IL-8 response to LPS; differentially expressed microRNAs such as miR-149 may play a role in the persistent modulation of the epithelial innate immune response towards microbes in the mature lung.

Innate immune response to LPS in airway epithelium is dependent on chronological age and antecedent exposures

The immune mechanisms for neonatal susceptibility to respiratory pathogens are poorly understood. Given that mucosal surfaces serve as a first line of host defense, we hypothesized that the innate immune response to infectious agents may be developmentally regulated in airway epithelium. To test this hypothesis, we determined whether the expression of IL-8 and IL-6 in airway epithelium after LPS exposure is dependent on chronological age. Tracheas from infant, juvenile, and adult rhesus monkeys were first exposed to LPS ex vivo, and then processed for air-liquid interface primary airway epithelial cell cultures and secondary LPS treatment in vitro. Compared with adult cultures, infant and juvenile cultures expressed significantly reduced concentrations of IL-8 after LPS treatment. IL-8 protein in cultures increased with animal age, whereas LPS-induced IL-6 protein was predominantly associated with juvenile cultures. Toll-like receptor (TLR) pathway RT-PCR arrays showed differential expressions of multiple mRNAs in infant cultures relative to adult cultures, including IL-1α, TLR10, and the peptidoglycan recognition protein PGLYRP2. To determine whether the age-dependent cytokine response to LPS is reflective of antecedent exposures, we assessed primary airway epithelial cell cultures established from juvenile monkeys housed in filtered air since birth. Filtered air-housed animal cultures exhibited LPS-induced IL-8 and IL-6 expression that was discordant with age-matched ambient air-housed animals. A single LPS aerosol in vivo also affected this cytokine profile. Cumulatively, our findings demonstrate that the innate immune response to LPS in airway epithelium is variable with age, and may be modulated by previous environmental exposures.

Airway epithelial wounds in rhesus monkey generate ionic currents that guide cell migration to promote healing

Damage to the respiratory epithelium is one of the most critical steps to many life-threatening diseases, such as acute respiratory distress syndrome and chronic obstructive pulmonary disease. The mechanisms underlying repair of the damaged epithelium have not yet been fully elucidated. Here we provide experimental evidence suggesting a novel mechanism for wound repair: endogenous electric currents. It is known that the airway epithelium maintains a voltage difference referred to as the transepithelial potential. Using a noninvasive vibrating probe, we demonstrate that wounds in the epithelium of trachea from rhesus monkeys generate significant outward electric currents. A small slit wound produced an outward current (1.59 μA/cm(2)), which could be enhanced (nearly doubled) by the ion transport stimulator aminophylline. In addition, inhibiting cystic fibrosis transmembrane conductance regulator (CFTR) with CFTR(Inh)-172 significantly reduced wound currents (0.17 μA/cm(2)), implicating an important role of ion transporters in wound induced electric potentials. Time-lapse video microscopy showed that applied electric fields (EFs) induced robust directional migration of primary tracheobronchial epithelial cells from rhesus monkeys, towards the cathode, with a threshold of <23 mV/mm. Reversal of the field polarity induced cell migration towards the new cathode. We further demonstrate that application of an EF promoted wound healing in a monolayer wound healing assay. Our results suggest that endogenous electric currents at sites of tracheal epithelial injury may direct cell migration, which could benefit restitution of damaged airway mucosa. Manipulation of ion transport may lead to novel therapeutic approaches to repair damaged respiratory epithelium.

Occurrence and correlations between coliphages and anthropogenic viruses in the Massachusetts Bay using enrichment and ICC-nPCR

We evaluated a two-step enrichment procedure to detect coliphages and an integrated cell culture-nested polymerase chain reaction (ICC-nPCR) to detect human astrovirus, enteroviruses, rotavirus and adenovirus type 40 and 41 in marine water samples collected by the Massachusetts Water Resource Authority (MWRA). MWRA has been monitoring its receiving waters for coliphages, anthropogenic viruses and indicator bacteria in order to evaluate the impact of Boston's Deer Island Sewage Treatment Plant discharge. Coliphages and enteric viruses were originally assayed using single agar overlay and most probable number cell culture (MPN) methods, respectively. Reanalysis of these samples for enteric viruses by ICC-nPCR demonstrated that 46% were positive for at least one virus compared with 23% with the MPN method. Use of the enrichment method showed a 47% increase in the detection of male specific and somatic coliphages compared with the single agar overlay method. Correlations between the presence of coliphages, enteric viruses and indicator bacteria were based on proximity to the treatment plant discharge, seasonal variations and site levels. The presence of enteric viruses was significantly correlated to coliphages but not to indicator bacteria. Preliminary comparative results demonstrate that effective and efficient monitoring of anthropogenic contamination can be achieved using these more sensitive and specific techniques.

Detection of astroviruses, enteroviruses, and adenovirus types 40 and 41 in surface waters collected and evaluated by the information collection rule and an integrated cell culture-nested PCR procedure

We evaluated the use of an integrated cell culture-reverse transcription-PCR (ICC-RT-PCR) procedure coupled with nested PCR to detect human astroviruses, enteroviruses, and adenovirus types 40 and 41 in surface water samples that were collected and evaluated by using the Information Collection Rule (ICR) method. The results obtained with the ICC-RT-PCR-nested PCR method were compared to the results obtained with the total culturable virus assay-most-probable-number (TCVA-MPN) method, the method recommended by the U.S. Environmental Protection Agency for monitoring viruses in surface and finished waters. Twenty-nine ICR surface water samples were analyzed. Viruses were concentrated by using filter adsorption-beef extract elution and organic flocculation techniques, and then the preparations were evaluated for viruses by visualizing cytopathic effects in the Buffalo green monkey kidney (BGMK) cell line. In the ICC-RT-PCR-nested PCR technique we used Caco-2 cells to propagate astroviruses and enteroviruses (ICC step), and we used BGMK cells to propagate adenovirus types 40 and 41, as well as enteroviruses. Fifteen of the 29 samples (51.7%) were positive for astrovirus as determined by the ICC-RT-PCR-nested PCR method, and eight of these samples (27.5%) contained infectious astrovirus. Seventeen of the 29 samples (58.6%) were positive for enteroviruses when the BGMK cell line was used, and six (27.6%) of these samples were determined to be infectious. Fourteen of the 29 samples (48.3%) were positive for adenovirus types 40 and 41, and 11 (37.9%) of these samples were determined to be infectious. Twenty-seven of the 29 samples (93.1%) were positive for a virus, and 19 (68.9%) of the samples were positive for an infectious virus. Only 5 of the 29 samples (17.2%) were positive as determined by the TCVA-MPN method. The ICC-RT-PCR-nested PCR method provided increased sensitivity compared to the TCVA-MPN method.

Enhanced phosphorylation of many endogenous protein substrates in human fibroblasts transformed by simian virus 40

Protein phosphorylation in normal and in simian virus 40-transformed human skin fibroblasts was assessed by two different methods: incubation of whole-cell homogenates with [gamma-(32)P]ATP or labeling of intact cells with Na(2)H(32)PO(4). Phosphorylated proteins were detected by sodium dodecyl sulfate/polyacrylamide gel electrophoresis and autoradiography. With both methods, the Coomassie-blue-stained protein patterns of the three transformed cell lines studied were similar to the patterns of the nontransformed normal human cells. However, although the phosphoprotein autoradiograms of the three transformed cell lines were nearly identical, their patterns were strikingly different from those of the nontransformed cells. Each of the three transformed lines tested showed approximately 25-30 phosphoprotein bands that were significantly enhanced when compared to the patterns of the nontransformed cells. Quantitation of 12 of the enhanced phosphoprotein bands in one of the transformed cell lines showed an average of 4.4 times as much phosphorylation as in the normal cells. The enhanced phosphorylation observed in the transformed cell lines was not dependent on the growth rate of the cells or on cyclic AMP. Furthermore, when homogenates of transformed and nontransformed cells were mixed prior to incubation with [gamma-(32)P]ATP, the resultant phosphoprotein patterns resembed those obtained with transformed cells alone. In addition, an evaluation of the time course of protein phosphorylation revealed that the initial reaction rate was greater in the transformed than in the normal cells, although in both cell types the reaction was complete after 1 min. The results suggest that the simian virus 40-transformed human fibroblasts possess an increased ability to phosphorylate proteins rather than that the normal cells possess a diffusible inhibitor. There appear to be many endogenous cellular substrates for this increased activity.

Steroid hormone toxicity in human fibroblasts does not correlate with high affinity receptor content

Human diploid skin fibroblasts derived from normal individuals and those with the testicular feminization syndrome (TFM) have been shown to be killed to the same degree by dihydrotestosterone in spite of the absence of high affinity cellular androgen receptors in the TFM fibroblasts. Furthermore, several different normal fibroblast strains from various anatomical sites all showed similar amounts of androgen-induced cytotoxicity even though their respective receptor contents differed by as much as ten-fold. These results suggest that steroid-induced cytotoxicity in human fibroblasts is not correlated with receptor content, unlike murine lymphoid cells in which the receptor content has been shown to be closely related to their ability to survive hormone exposure.

Enhanced dexamethasone resistance in cystic fibrosis cells: potential use for heterozygote detection and prenatal diagnosis

Cultured skin fibroblasts from patients with cystic fibrosis (CF) are more resistant to dexamethasone toxicity than are normal cells. We now report that, when fibroblasts cultured from obligate CF heterozygotes are exposed to dexamethasone, they have an intermediate survival compared to normal and homozygous CF cells. When dexamethasone survival was tested on cells from four patients undergoing amniocentesis, cells from a woman at risk of producing a child with CF showed significant dexamethasone resistance, similar to that of fibroblasts derived from lnown CF homozygotes; the other amniotic cell specimens showed dexamethasone sensitivity similar to that of normal skin fibroblasts. These data suggest that the dexamethasone resistance previously observed in skin fibroblasts may also be useful in the prenatal diagnosis of CF.

Dexamethasone-resistant cystic fibrosis fibroblasts show cross-resistance to sex steroids

Diploid skin fibroblasts derived from individuals with the autosomal recessive disease, cystic fibrosis (CF), were shown previously to be significantly more resistant to the cytotoxicity of dexamethasone, a glucocorticoid hormone, than were normal human fibroblasts. Here cystic fibrosis fibroblasts are also shown to be more resistant than normal human fibroblasts to the cytotoxic effects of the sex hormones, 17 beta-estradiol, dihydrotestosterone and progesterone. Since cells are believed to contain different receptors for each of the steroid hormones, it is not probable than the resistance of CF cells to these hormones results from a receptor deficiency. This was shown by the fact that CF cells were found to exhibit the same receptor activity as normal cells for 3-H-dexamethasone. Furthermore, neither normal human nor CF fibroblasts could be demonstrated to contain detectable receptor activity for 3H-17 beta-estradiol. In addition, the studies of fibroblast killing by hormones led to the further interesting observation that normal human diploid fibroblasts, regardless of the sex of the tissue donor, are sensitive to killing by each of the sex hormones. These findings suggest that the cytotoxic effects of the steroid hormones may be observed independently of the specific hormone receptors. The studies reported here thus suggest that the resistance of CF cells to the different steroid hormones is probably the result of a defect in a pathway in cellular steroid hormone metabolism other than that involving receptors.

Asbestos control in steam-electric generating plants

A program to control industrial work exposures to airborne asbestos fibers is presented. The program is consistent with OSHA standards, and with current good industrial hygiene practice. The program includes methods of problem evaluation, the establishment of effective corporate standards, and provisions for environmental and medical surveillance. Hazard control measures and techniques are discussed and their merits related.