Publications

Chronic infections induce a complex immune response that controls pathogen replication, but also causes pathology due to sustained inflammation. Ca2+ influx mediates T cell function and immunity to infection, and patients with inherited mutations in the gene encoding the Ca2+ channel ORAI1 or its activator stromal interaction molecule 1 (STIM1) are immunodeficient and prone to chronic infection by various pathogens, including Mycobacterium tuberculosis (Mtb). Here, we demonstrate that STIM1 is required for T cell-mediated immune regulation during chronic Mtb infection. Compared with WT animals, mice with T cell-specific Stim1 deletion died prematurely during the chronic phase of infection and had increased bacterial burdens and severe pulmonary inflammation, with increased myeloid and lymphoid cell infiltration. Although STIM1-deficient T cells exhibited markedly reduced IFN-γ production during the early phase of Mtb infection, bacterial growth was not immediately exacerbated. During the chronic phase, however, STIM1-deficient T cells displayed enhanced IFN-γ production in response to elevated levels of IL-12 and IL-18. The lack of STIM1 in T cells was associated with impaired activation-induced cell death upon repeated TCR engagement and pulmonary lymphocytosis and hyperinflammation in Mtb-infected mice. Chronically Mtb-infected, STIM1-deficient mice had reduced levels of inducible regulatory T cells (iTregs) due to a T cell-intrinsic requirement for STIM1 in iTreg differentiation and excessive production of IFN-γ and IL-12, which suppress iTreg differentiation and maintenance. Thus, STIM1 controls multiple aspects of T cell-mediated immune regulation to limit injurious inflammation during chronic infection.

Hepatocyte growth factor (HGF) promotes lung epithelial repair after injury. Because prior studies established that human neutrophil proteases inactivate HGF in vitro, we predicted that HGF levels decrease in lungs infiltrated with neutrophils and that injury is less severe in lungs lacking HGF-inactivating proteases. After establishing that mouse neutrophil elastase cleaves mouse HGF in vitro, we tested our predictions in vivo by examining lung pathology and HGF in mice infected with Mycoplasma pulmonis, which causes neutrophilic tracheobronchitis and pneumonia. Unexpectedly, pneumonia severity was similar in wild type and dipeptidylpeptidase I-deficient (Dppi-/-) mice lacking neutrophil serine protease activity. To assess how this finding related to our prediction that Dppi-activated proteases regulate HGF levels, we measured HGF in serum, bronchoalveolar lavage fluid, and lung tissue from Dppi(+/+) and Dppi(-/-) mice. Contrary to prediction, HGF levels were higher in lavage fluid from infected mice. However, serum and tissue concentrations were not different in infected and uninfected mice, and HGF lung transcript levels did not change. Increased HGF correlated with increased albumin in lavage fluid from infected mice, and immunostaining failed to detect increased lung tissue expression of HGF in infected mice. These findings are consistent with trans-alveolar flux rather than local production as the source of increased HGF in lavage fluid. However, levels of intact HGF from infected mice, normalized for albumin concentration, were two-fold higher in Dppi(-/-) versus Dppi(+/+) lavage fluid, suggesting regulation by Dppi-activated proteases. Consistent with the presence of active HGF, increased expression of activated receptor c-Met was observed in infected tissues. These data suggest that HGF entering alveoli from the bloodstream during pneumonia compensates for destruction by Dppi-activated inflammatory proteases to allow HGF to contribute to epithelial repair.

Like normal cellular nucleosides, the nucleoside reverse transcriptase (RT) inhibitor (NRTI) 4'-ethynyl-2-fluoro-2'-deoxyadenosine (EFdA) has a 3'-hydroxyl moiety, and yet EFdA is a highly potent inhibitor of human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) replication with activity against a broad range of clinically important drug-resistant HIV isolates. We evaluated the anti-HIV activity of EFdA in primary human cells and in HIV-infected humanized mice. EFdA exhibited excellent potency against HIVJR-CSF in phytohemagglutinin-stimulated peripheral blood mononuclear cells (PBMCs), with a 50% inhibitory concentration of 0.25 nM and a selectivity index of 184,000; similar antiviral potency was found against 12 different HIV clinical isolates from multiple clades (A, B, C, D, and CRF01_AE). EFdA was readily absorbed after oral dosing (5 mg/kg of body weight) in both mice and the rhesus macaque, with micromolar levels of the maximum concentration of drug in serum (Cmax) attained at 30 min and 90 min, respectively. Trough levels were at or above 90% inhibitory concentration (IC90) levels in the macaque at 24 h, suggesting once-daily dosing. EFdA showed reasonable penetration of the blood-brain barrier in the rhesus macaque, with cerebrospinal fluid levels at approximately 25% of plasma levels 8 h after single oral dosing. Rhesus PBMCs isolated 24 h following a single oral dose of 5 mg/kg EFdA were refractory to SIV infection due to sufficiently high intracellular EFdA-triphosphate levels. The intracellular half-life of EFdA-triphosphate in PBMCs was determined to be >72 h following a single exposure to EFdA. Daily oral administration of EFdA at low dosage levels (1 to 10 mg/kg/day) was highly effective in protecting humanized mice from HIV infection, and 10 mg/kg/day oral EFdA completely suppressed HIV RNA to undetectable levels within 2 weeks of treatment.

OBJECTIVES

To describe the characteristics of home-based primary care practices: staffing, administrative, population served, care practices, and quality of care challenges.

DESIGN

Survey of home-based primary care practices.

SETTING

Home-based primary care practices in the United States.

PARTICIPANTS

Members of the American Academy of Home Care Medicine and nonmember providers identified by surveyed members.

MEASUREMENTS

A 58-item questionnaire that assessed practice characteristics, care provided by the practice, and how the quality of care that the practice provided was assessed.

RESULTS

Survey response rate was 47.9%, representing 272 medical house calls practices. Mean average daily census was 457 patients (median 100 patients, range 1-30,972 patients). Eighty-eight percent of practices offered around-the-clock coverage for urgent concerns, 60% held regularly scheduled team meetings, 89% used an electronic medical record, and one-third used a defined quality improvement process. The following factors were associated with practices that used a defined quality improvement process: practice holds regularly scheduled team meetings to discuss specific patients (odds ratio (OR)=2.07, 95% confidence interval (CI)=1.02-4.21), practice conducts surveys of patients (OR=8.53, 95% CI=4.07-17.88), and practice is involved in National Committee for Quality Assurance patient-centered medical home (OR=3.27, 95% CI=1.18-9.07). Ninety percent of practices would or might participate in quality improvement activities that would provide them timely feedback on patient and setting-appropriate quality indicators.

CONCLUSIONS

There is a substantial heterogeneity of home-based primary care practice types. Most practices perform activities that lend themselves to robust quality improvement efforts, and nearly all indicated interest in a national registry to inform quality improvement.

BACKGROUND

Palpitations are a common emergency department (ED) complaint, yet relatively little research exists on this topic from an emergency care perspective.

OBJECTIVES

We sought to describe the perceptions and clinical decision-making processes of emergency physicians (EP) surrounding patients with palpitations.

METHODS

We conducted 21 semistructured interviews with a convenience sample of EPs. We recruited participants from academic and community practice settings from four regions of the United States. The transcribed interviews were analyzed using a combination of structural coding and grounded theory approaches with ATLAS.ti, a qualitative data analysis software program (version 7; Atlas.ti Scientific Software Development GmbH, Berlin, Germany).

RESULTS

EPs perceive palpitations to be a common but generally benign chief complaint. EPs' clinical approach to palpitations, with regards to testing, treatment, and ED management, can be classified as relating to one or more of the following themes: (1) risk stratification, (2) diagnostic categorization, (3) algorithmic management, and (4) case-specific gestalt. With regard to disposition decisions, four main themes emerged: (1) presence of a serious diagnosis, (2) perceived need for further cardiac testing/monitoring, (3) presence of key associated symptoms, (4) request of other physician or patient desire. The interrater reliability exercise yielded a Fleiss' kappa measure of 0.69, indicating substantial agreement between coders.

CONCLUSION

EPs perceive palpitations to be a common but generally benign chief complaint. EPs rely on one or more of four main clinical approaches to manage these patients. These findings could help guide future efforts at developing risk-stratification tools and clinical algorithms for patients with palpitations.