eScholarship@UMMS

BACKGROUND: We assessed the prevalence of preserved left ventricular ejection fraction in patients with incident heart failure and differences in the demographic and clinical characteristics that may differentiate patients presenting with heart failure with preserved versus reduced left ventricular ejection fraction.

METHODS: We identified all patients with newly diagnosed heart failure between 2005 and 2008 from 4 sites in the Cardiovascular Research Network on the basis of hospital discharge and ambulatory visit diagnoses, and assigned a category of preserved, borderline, or reduced left ventricular ejection fraction using data from electronic databases and chart review.

RESULTS: We identified 11,994 patients with incident heart failure; of these, 6210 (51.8%) had preserved left ventricular ejection fraction, 1870 (15.6%) had borderline systolic dysfunction, and 3914 (32.6%) had reduced left ventricular ejection fraction. For those with heart failure with preserved left ventricular ejection fraction, the mean age was 74.7 years and 57.1% were women; for those with borderline systolic dysfunction, the mean age was 71.6 years and 38.4% were women; and for those with reduced left ventricular ejection fraction, the mean age was 69.1 years and 32.6% were women. Compared with white patients, black patients were less likely to have heart failure with preserved systolic function. Those with a history of coronary artery bypass surgery, mitral or aortic valvular disease, atrial fibrillation or flutter, or a diagnosis of hypertension were more likely to have heart failure with preserved systolic function, as were those with a diverse range of noncardiac comorbid conditions, including chronic lung disease, chronic liver disease, a history of a hospitalized bleed, a history of a mechanical fall, a diagnosis of depression, and a diagnosis of dementia. Patients with a history of acute myocardial infarction and a history of ventricular fibrillation or ventricular tachycardia were less likely to have heart failure with preserved left ventricular ejection fraction. Patients with higher systolic blood pressures at baseline and lower low-density lipoprotein levels were more likely to have heart failure with preserved left ventricular ejection fraction, as were those with lower hemoglobin levels and the lowest glomerular filtration rates.

CONCLUSIONS: Heart failure with preserved left ventricular ejection fraction is the most common form of the heart failure syndrome among patients newly presenting with this condition, and women and older adults are especially affected. Evidence-based treatment strategies apply to less than one third of patients with newly diagnosed heart failure.

Translational researchers conduct research in a highly data-intensive and continuously changing environment and need to use multiple, disparate tools to achieve their goals. These researchers would greatly benefit from meta-composite software development or the ability to continuously compose and recompose tools together in response to their ever-changing needs. However, the available tools are largely disconnected, and current software approaches are inefficient and ineffective in their support for meta-composite software development. Building on the composite services development approach, the de facto standard for developing integrated software systems, we propose a concept-map and agent-based meta-composite software development approach. A crucial step in composite services development is the modeling of users' needs as processes, which can then be specified in an executable format for system composition. We have two key innovations.

First, our approach allows researchers (who understand their needs best) instead of technicians to take a leadership role in the development of process models, reducing inefficiencies and errors. A second innovation is that our approach also allows for modeling of complex user interactions as part of the process, overcoming the technical limitations of current tools. We demonstrate the feasibility of our approach using a real-world translational research use case. We also present results of usability studies evaluating our approach for future refinements.

We present a systematic study of the characterization and thermoelectric properties of nanostructured Na-doped PbSe embedded with 1-4% MSe (M = Ca, Sr, Ba) phases as endotaxial inclusions. The samples were powder-processed by the spark plasma sintering technique, which introduces mesoscale-structured grains. The hierarchical architectures on the atomic scale (Na and M solid solution), nanoscale (MSe nanoprecipitates), and mesoscale (grains) were confirmed by transmission electron microscopy. These structures produce a great reduction in the lattice thermal conductivity relative to pristine PbSe without appreciably affecting the power factor. The lattice thermal conductivity can be reduced by up to approximately 29% when the second phase is added. The highest ZT value achieved was approximately 1.3 at 923 K for both 2% SrSe-and 3% BaSe-containing samples, while the sample containing 4% CaSe showed a ZT value of approximately 1.2 at 923 K. The optimal samples have hole carrier concentration of 1-2 x 1020 cm-3. We attribute the high ZT values to the combination of broad-based phonon scattering on multiple length scales and favorable charge transport through coherent interfaces between the PbSe matrix and MSe.

BACKGROUND: Atrial fibrillation (AF) and heart failure (HF) are 2 of the most common cardiovascular conditions nationally and AF frequently complicates HF. We examined how AF has impacts on adverse outcomes in HF-PEF versus HF-REF within a large, contemporary cohort.

METHODS AND RESULTS: We identified all adults diagnosed with HF-PEF or HF-REF based on hospital discharge and ambulatory visit diagnoses and relevant imaging results for 2005-2008 from 4 health plans in the Cardiovascular Research Network. Data on demographic features, diagnoses, procedures, outpatient pharmacy use, and laboratory results were ascertained from health plan databases. Hospitalizations for HF, stroke, and any reason were identified from hospital discharge and billing claims databases. Deaths were ascertained from health plan and state death files. Among 23 644 patients with HF, 11 429 (48.3%) had documented AF (9081 preexisting, 2348 incident). Compared with patients who did not have AF, patients with AF had higher adjusted rates of ischemic stroke (hazard ratio [HR] 2.47 for incident AF; HR 1.57 for preexisting AF), hospitalization for HF (HR 2.00 for incident AF; HR 1.22 for preexisting AF), all-cause hospitalization (HR 1.45 for incident AF; HR 1.15 for preexisting AF), and death (incident AF HR 1.67; preexisting AF HR 1.13). The associations of AF with these outcomes were similar for HF-PEF and HF-REF, with the exception of ischemic stroke.

CONCLUSIONS: AF is a potent risk factor for adverse outcomes in patients with HF-PEF or HF-REF. Effective interventions are needed to improve the prognosis of these high-risk patients.

We conducted a cluster randomized trial testing the effectiveness of an intervention to increase the use of osteoporosis medications in high-risk patients receiving home health care. The trial did not find a significant difference in medication use in the intervention arm.

INTRODUCTION: This study aims to test an evidence implementation intervention to improve the quality of care in the home health care setting for patients at high risk for fractures.

METHODS: We conducted a cluster randomized trial of a multimodal intervention targeted at home care for high-risk patients (prior fracture or physician-diagnosed osteoporosis) receiving care in a statewide home health agency in Alabama. Offices throughout the state were randomized to receive the intervention or to usual care. The primary outcome was the proportion of high-risk home health patients treated with osteoporosis medications. A t test of difference in proportions was conducted between intervention and control arms and constituted the primary analysis. Secondary analyses included logistic regression estimating the effect of individual patients being treated in an intervention arm office on the likelihood of a patient receiving osteoporosis medications. A follow-on analysis examined the effect of an automated alert built into the electronic medical record that prompted the home health care nurses to deploy the intervention for high-risk patients using a pre-post design.

RESULTS: There were 11 offices randomized to each of the treatment and control arms; these offices treated 337 and 330 eligible patients, respectively. Among the offices in the intervention arm, the average proportion of eligible patients receiving osteoporosis medications post-intervention was 19.1 %, compared with 15.7 % in the usual care arm (difference in proportions 3.4 %, 95 % CI, -2.6 to 9.5 %). The overall rates of osteoporosis medication use increased from 14.8 % prior to activation of the automated alert to 17.6 % afterward, a nonsignificant difference.

CONCLUSIONS: The home health intervention did not result in a significant improvement in use of osteoporosis medications in high-risk patients.

OBJECTIVE: Personal Health Records (PHRs) tethered to an Electronic Health Record (EHR) offer patients unprecedented access to their personal health information. At the Department of Veteran Affairs (VA), the My HealtheVet Pilot Program was an early PHR prototype enabling patients to import 18 types of information, including clinical notes and laboratory test results, from the VA EHR into a secure PHR portal. The goal of this study was to explore Veteran perceptions about this access to their medical records, including perceived value and effect on satisfaction, self-care, and communication.

METHODS: Patients enrolled in the pilot program were invited to participate in a web-based survey.

RESULTS: Among 688 Veteran respondents, there was a high degree of satisfaction with the pilot program, with 84% agreeing that the information and services were helpful. The most highly ranked feature was access to personal health information from the VA EHR. The majority of respondents (72%) indicated that the pilot Web site made it easy for them to locate relevant information. Most participants (66%) agreed that the pilot program helped improve their care, with 90% indicating that they would recommend it to another Veteran.

CONCLUSIONS: Veterans' primary motivation for use of the pilot Web site was the ability to access their own personal health information from the EHR. With patients viewing such access as beneficial to their health and care, PHRs with access to EHR data are positioned to improve health care quality. Making additional information accessible to patients is crucial to meet their needs and preferences.

BACKGROUND: Vulnerable populations face difficulties accessing and using the internet and personal health record (PHR) systems for health-related purposes. Populations disconnected from the internet also tend to be disconnected from health care services.

OBJECTIVES: To develop and evaluate an intervention to increase skills in health-related internet and PHR use for vulnerable populations with limited computer and internet experience.

RESEARCH DESIGN: Preevaluation and postevaluation using quantitative surveys, semistructured interviews, focus groups, and ethnographic observation.

SUBJECTS: Fourteen low-income Veterans receiving care at Veterans Affairs medical centers for human immunodeficiency virus or hepatitis C.

MEASURES: Internet and PHR use, self-efficacy, patient activation, disease knowledge, predictors of medication adherence.

RESULTS: At follow-up one (FU1), mean number of internet for health features used increased from 1.57 to 4.07 (P<0.001) as did number of PHR features, from 0.36 to 2.00 (P<0.001). Mean self-efficacy increased at FU1, from 7.12 to 8.60, (P=0.009) and was maintained at follow-up two (FU2). Patient activation increased only at FU2, from 3.42 to 3.61 (P=0.03). Disease specific knowledge showed borderline increase at FU1, from 67.9% to 72.2% (P=0.05), whereas there were no changes in predictors of medication adherence. Qualitative findings underscored the interest in using internet and PHRs and their contribution to increased engagement in care. Training cost per participant was $287.

CONCLUSIONS: Group training of vulnerable patients represents a cost-effective method to increase internet and PHR skills, and improve patient confidence in finding health-related information, making online health-related transactions, and interacting with health care providers.

Background. Acquired immunity to malaria develops with increasing age and repeated infections. Understanding immune correlates of protection from malaria infection would facilitate vaccine development and identification of biomarkers that reflect changes in susceptibility resulting from ongoing malaria control efforts.

Methods. The relationship between IgG antibody and IFN-gamma and IL-10 responses to the 42 kD C-terminal fragment of Plasmodium falciparum Merozoite Surface Protein 1 (MSP142) and risk-of-(re)infection were examined following drug-mediated clearance of parasitemia in 94 adults and 95 children in a holoendemic area of western Kenya.Results. Positive IFN-gamma ELISA and ELISPOT responses to MSP-142 3D7 were associated with delayed time-to-(re)infection whereas high-titer IgG antibodies to MSP-142 3D7 or FVO alleles were not independently predictive of risk-of-(re)infection. When IFN-gamma and IL-10 responses were both present, the protective effect of IFN-gamma was abrogated. A Cox proportional hazard model including IFN-gamma, IL-10, MSP142 3D7 IgG antibody responses, hemoglobin S genotype, age and infection status at baseline, showed time to blood-stage infection correlated positively with IFNgamma+ responses and negatively with IL-10+ responses, younger age, and asymptomatic parasitemia

.Conclusion. Evaluating combined allele-specific cellular and humoral immunity elicited by malaria provides a more informative measure of protection relative to either measure alone.

A mouse model of heterosubtypic influenza A virus infections was used to determine the role of MyD88 signaling in CD4+ T-cell, CD8+ T-cell, and IgG immune responses. We found that MyD88 signaling played an important role in anti-influenza A virus heterosubtypic lung and spleen CD4+ T-cell, and spleen CD8+ T-cell, immune responses. MyD88 dependent signaling was important for T-helper 1 cytokine production in anti-influenza A virus lung and spleen heterosubtypic CD4+ T-cells, but not for their frequencies. Toll-like receptor 7 dependent signaling played a partial role in anti-influenza A virus lung heterosubtypic CD4+ T-helper 1 responses and anti-influenza A virus heterosubtypic IgG2c antibody levels. Our results have important implications for the generation of effective universal influenza vaccines.

Human Immunodeficiency Virus Type 1 (HIV-1) is the causative agent of Acquired Immunodeficiency Syndrome (AIDS), currently the leading cause of death from infectious diseases. Since HIV-1 co-opts the host cellular machinery, the study of cellular factors involved is a rational approach in discovering novel therapeutic targets for AIDS drug development. In this thesis, we present studies on two such proteins. APOBEC3G is from the family of cytidine deaminases known to keep endogenous retroviruses and retrotransposons at bay to maintain stability of the human genome. APOBEC3G targets Vif-deficient HIV-1 particles and renders them noninfectious, partially through deaminase-dependent hypermutation of the provirus during reverse transcription. APOBEC3G largely localizes in mRNA processing (P) bodies, cytoplasmic structures involved in RNA metabolism. Here we explore the significance of APOBEC3G localization in P bodies. We found that disrupting P bodies does not affect virion incorporation of endogenous APOBEC3G, implying that the APOBEC3G fraction in P bodies is not directly involved in the production of nascent, non-infectious particles.

We also study UPF1, another host protein encapsidated by HIV-1. It is an essential protein mainly studied for its role in nonsense-mediated decay (NMD) pathway and belongs to the same helicase superfamily as MOV10, a recently identified antiviral factor. We found that UPF1 is incorporated in HIV-1 virions in a nucleocapsid-dependent manner and is required for single-cycle infectivity at an early, post-entry step of the viral life cycle. This novel function of UPF1 most likely does not involve NMD since depletion of UPF2 does not affect viral infectivity.

Since the initial characterization of the human glucose transporter GLUT1, it has been observed that the presence of intracellular sugar stimulates the unidirectional rate of sugar uptake by a kinetic phenomenon known as trans-acceleration. Both GLUTs 1 and 3 catalyze transacceleration, while both GLUTs 2 and 4 do not. Although the basis for trans-acceleration is unknown, potential explanations include the requirement of a modulating cofactor, cellular context, or that the behavior is an artifact of imperfect transport measurements. This thesis examines whether trans-acceleration is a sequence-specific property intrinsic to the transporter. A method for detecting trans-acceleration in mammalian cells at physiologic temperature was developed through transport of two different glucose analogs. Homology-scanning mutagenesis was employed to exchange transmembrane domains (TMs) of GLUTs 1 and 4, and thereby test for accelerated-exchange loss- or gain-of-function. This approach was extended to GLUTs 2 and 3. The catalytic rates of these chimeric proteins were determined through transport measurements and expression measured by cell-surface biotinylation. These studies show that the sequence of putative scaffolding domain TM6 is both necessary and sufficient for trans-acceleration in scaffolds of GLUT1, GLUT2, and GLUT4. The substitution of TM6 sequence between these transporters has no effect on the turnover under exchange conditions, yet profoundly modifies turnover in the absence of intracellular sugar. We propose that the sequence-specific interaction of TM6 with other TMs structurally restrains relaxation of the empty carrier in GLUTs which catalyze trans-acceleration, and that binding of intracellular sugar affects these interactions to reduce the overall duration of the transport cycle. In addition, our model suggests that the substrate binding constant and rate of carrier relaxation are inter-dependent. In this model, the dissociation constant determined by substrate binding and dissociation rates at the endofacial sugar binding site must be larger than the equivalent constant at the exofacial site in order for trans-acceleration to occur.

Virus infection is sensed by the innate immune system through germline encoded pattern recognition receptors (PRRs). Toll-like receptors (TLRs), retinoic acid-inducible gene-I-like receptors (RLRs) and nucleotide-binding oligomerization domain-like receptors (NLRs) serve as PRRs that recognize different viral components. Microbial nucleic acids such as Ribonucleic acid (RNA) are important virus-derived pathogen-associated molecular patterns (PAMPs) to be recognized by PRRs. Virus recognition may occur at multiple stages of the viral life cycle. Replication intermediates such as single-stranded RNA (ssRNA) and double-stranded RNA (dsRNA) are detected by the RNA-sensing PRRs that initiate innate and adaptive immune responses. Triggering of the innate immune system is a critical event that can shape the adaptive immune response to virus infection. Better vaccination strategies that lead to improved T-cell and antibody responses are needed for protection against pathogens. We sought to delineate the RNA-sensing PRR pathways that are activated during infection with an RNA virus, the signaling mediators involved and the influence on subsequent virus-specific adaptive immune responses.

To analyze the role of RNA-sensing PRRs in T-cell immune responses in vitro, we performed direct co-stimulation experiments on CD4+ T-cells of high purity. We utilized synthetic RNA-like immune response modifiers (IRMs) R-848 (MyD88-dependent) and poly I:C (MyD88-independent) as RNA PAMPs to determine the direct effects of RNA-sensing PRR activation on CD4+ T-cells. RNA PAMPs can act directly on CD4+ T-cells and modulate their function and phenotype. Maximal direct co-stimulatory effects were observed in CD4+ T-cells cultured with poly I:C compared to R-848. The cytoplasmic dsRNA-dependent protein kinase R (PKR) was also involved in poly I:C-mediated signaling in CD4+ T-cells.

We found differences in the RNA-sensing PRRs activated by R-848 between mouse and human CD4+ T-cells. We observed minimal direct co-stimulatory effects by R-848 in mouse CD4+ T-cells. In contrast, augmentation of Th1 responses by R-848 was observed in human CD4+ T-cells. TLR8 activation in human CD4+ T-cells may explain the observed differences.

We next explored the signaling pathways activated by RNA PAMPs in conventional dendritic cells (cDCs) and CD4+ T-cells that drive Th1 CD4 T-cell responses in isolated cDC/CD4 T-cell interactions. Allogeneic cDCs and CD4+ T-cells of high purity were cultured together with R-848 and poly I:C in MHC congenic mixed leukocyte reactions (MLRs). R-848 and poly I:C stimulation of type I IFN production and signaling was essential but not sufficient for driving CD4+ Th1 responses. The early production of IL-1α and IL-1β was equally critical.

To analyze the role of RNA-sensing PRRs in T-cell immune responses in vivo, we utilized a mouse model of heterosubtypic influenza A virus (IAV) infections. Using MyD88-/-, TLR7-/- and IL-1-deficient mice, we explored the role of MyD88-signaling in the generation of heterosubtypic memory CD4+ T-cell, CD8+ T-cell and antibody responses. We found that MyD88 signaling played an important role in anti-IAV spleen and lung CD4+ T-cell, spleen CD8+ T-cell and Th1 antibody immune responses. Anti-IAV lung heterosubtypic CD8+ T-cell responses were not dependent on MyD88 signaling.

Our in vitro and in vivo results show the pivotal role of RNA-sensing PRR pathway activation in T-cell immune responses. Understanding the complexity of the PRR pathways involved during viral infections and defining the subsequent immune response would have important implications for the generation of more effective vaccine strategies.

The formation of the anterior-posterior axis requires a symmetry-breaking event that starts gastrulation. Ultimately, the morphogenetic movements of gastrulation reshape the embryo to its final tri-dimensional form. In mouse embryos, the identity of the molecule that breaks the bilateral symmetry and sets in motion gastrulation remains elusive. The Wnt signaling pathway plays a pivotal role during axial specification and gastrulation in metazoans. Loss-of-function experiments have demonstrated a requirement of Wnt3 for gastrulation in mice. But because Wnt3 is expressed sequentially in two tissues, the visceral endoderm and the epiblast, its tissue specific requirements remain uncertain. Here, we report that embryos lacking Wnt3 specifically in the visceral endoderm do not form a primitive streak, mesoderm, endoderm or any derivatives. Visceral endoderm-specific Wnt3 mutants also lack primordial germ cells. Moreover, we provide data demonstrating that Wnt3 carries out its actions in the epiblast via the canonical Wnt pathway. Together, these data suggest that the posterior visceral endoderm via Wnt3, regulates the development of mouse embryos in a similar fashion to the amphibian Nieuwkoop center. Next, we conditionally ablated Wnt3 locus in the epiblast to investigate whether Wnt3 expression is also required in that tissue. Embryos lacking Wnt3 expression in the epiblast, but retaining its expression in the visceral endoderm, show delayed but not absent gastrulation. We conclude that the expression of Wnt3 in the epiblast is required for maintenance but not initiation of gastrulation in mouse embryos. Furthermore, we used in vitro and in vivo approaches to demonstrate that the Wnt3-mediated activation of the canonical Wnt pathway leads to β-catenin occupancy followed by transcription of key loci, including the Wnt3 locus itself, during gastrulation in mice. Our data indicate the presence of an autoregulatory loop in which Wnt3 controls its own expression and orchestrates the process of gastrulation in the mouse embryo.

Over 260,000 Americans are living with a traumatic spinal cord injury (SCI). Medical advances have increased the longevity of individuals living with SCI into middle age and beyond. The majority of these individuals are living with an incomplete SCI (NSCISC, 2012), and the proportion of incomplete injuries is rising (DeVivo, 2012). There is little research that specifically examines the changes in physical function experienced by individuals aging with a traumatic incomplete SCI. The purpose of this qualitative descriptive study was to describe the changes in physical function experienced by participants with a traumatic incomplete SCI aging through middle age. Data were collected through moderately structured individual interviews (N=17), in either a face-to-face (n=6) or an email (n=11) format. The seventeen participants ranged in age from 35 to 65 years, with a 16 to 36 year duration of injury. Participants described changes in various body systems and recalled the timing of those changes as they transitioned through their middle years. Qualitative content analysis revealed that participants described primarily gradual changes including decreased muscle strength, decreased endurance, weight gain, and wear and tear changes. When asked to identify sources of information about physical changes, participants predominantly emphasized their lack of knowledge about anticipated changes. Further content analysis revealed three themes related to this transition. Participants likened their experience to travelling through uncharted territory. They described strategies for living in uncharted territory that help them to prevent or manage changes in physical function, with sub-themes of being vigilant in their self-assessment and self-management practices, investing time in figuring out what changes they experienced and why those changes happened, and staying positive. They also described the importance of recognizing the impact of changes. These findings provide a foundation for understanding this age-related transition, and identify the need for further research to support effective self-management strategies and efficient mechanisms for disseminating this knowledge to people with SCI, their caregivers and families. In acute and chronic patient care settings, nurses are well-positioned to be a valuable support and information source for individuals living with an incomplete SCI.

Degenerate splice site sequences mark the intron boundaries of pre-mRNA transcripts in multicellular eukaryotes. The essential pre-mRNA splicing factor U2AF(65) is faced with the paradoxical tasks of accurately targeting polypyrimidine (Py) tracts preceding 3' splice sites while adapting to both cytidine and uridine nucleotides with nearly equivalent frequencies. To understand how U2AF(65) recognizes degenerate Py tracts, we determined six crystal structures of human U2AF(65) bound to cytidine-containing Py tracts. As deoxy-ribose backbones were required for co-crystallization with these Py tracts, we also determined two baseline structures of U2AF(65) bound to the deoxy-uridine counterparts and compared the original, RNA-bound structure. Local structural changes suggest that the N-terminal RNA recognition motif 1 (RRM1) is more promiscuous for cytosine-containing Py tracts than the C-terminal RRM2. These structural differences between the RRMs were reinforced by the specificities of wild-type and site-directed mutant U2AF(65) for region-dependent cytosine- and uracil-containing RNA sites. Small-angle X-ray scattering analyses further demonstrated that Py tract variations select distinct inter-RRM spacings from a pre-existing ensemble of U2AF(65) conformations. Our results highlight both local and global conformational selection as a means for universal 3' splice site recognition by U2AF(65).

OBJECTIVES: Identification of HIV infection in exposed infants facilitates early therapy, which may limit viral reservoirs that maintain HIV infection under HAART.

METHODS: The dynamics of the resting CD4 T-cell latent HIV reservoir was determined over the first 2 years of life in 17 HIV-infected infants initiating lopinavir/ritonavir-based HAART at a median age of 8.1 weeks and achieving adequate suppression of plasma viral load by 24 weeks.

RESULTS: The resting CD4 T-cell latent HIV reservoir was detected in 12 of 14 (86%) infants tested at 24 weeks of HAART [median frequency 1.88 infectious units per million (IUPM); range <0.22 to 3.25) in six of 10 (60%) children retested at 96 weeks. The reservoir declined, from 24 to 96 weeks of HAART, at an estimated mean rate of 0.028 log10 IUPM/month, corresponding to a half-life of 11 months (95% confidence interval 6-30 months]. A strong relationship was found between the frequency of latently infected CD4 T cells at 96 weeks of HAART and time to first undetectable plasma viral load (Spearman r = 0.91, P < 0.001).

CONCLUSION: Although the resting CD4 T-cell latent reservoir remains detectable over the first 2 years of HAART in a substantial proportion of infants, its size is associated with time to first undetectable viral load. To minimize HIV reservoirs in infants, rapid curtailment of viremia may limit HIV reservoirs and should be a therapeutic goal of early HAART in infants.

BACKGROUND: Programmed Death-1 (PD-1) is an inhibitory member of the CD28 family of molecules expressed on CD8+ T cells in response to antigenic stimulation. To better understand the role of PD-1 in antiviral immunity we examined the expression of PD-1 on Epstein-Barr virus (EBV) epitope-specific CD8+ T cells during acute infectious mononucleosis (AIM) and convalescence.

METHODOLOGY/PRINCIPAL FINDINGS: Using flow cytometry, we observed higher frequencies of EBV-specific CD8+ T cells and higher intensity of PD-1 expression on EBV-specific CD8+ T cells during AIM than during convalescence. PD-1 expression during AIM directly correlated with viral load and with the subsequent degree of CD8+ T cell contraction in convalescence. Consistent differences in PD-1 expression were observed between CD8+ T cells with specificity for two different EBV lytic antigen epitopes. Similar differences were observed in the degree to which PD-1 was upregulated on these epitope-specific CD8+ T cells following peptide stimulation in vitro. EBV epitope-specific CD8+ T cell proliferative responses to peptide stimulation were diminished during AIM regardless of PD-1 expression and were unaffected by blocking PD-1 interactions with PD-L1. Significant variability in PD-1 expression was observed on EBV epitope-specific CD8+ T cell subsets defined by V-beta usage.

CONCLUSIONS/SIGNIFICANCE: These observations suggest that PD-1 expression is not only dependent on the degree of antigen presentation, but also on undefined characteristics of the responding cell that segregate with epitope specificity and V-beta usage.

The CD4 binding site (CD4bs) on the HIV-1 envelope plays a major role in determining the capacity of R5 viruses to infect primary macrophages. Thus, envelope determinants within or proximal to the CD4bs have been shown to control the use of low CD4 levels on macrophages for infection. These residues affect the affinity for CD4 either directly or indirectly by altering the exposure of CD4 contact residues. Here, we describe a single amino acid determinant in the V1 loop that also modulates macrophage tropism. Thus, we identified an E153G substitution that conferred high levels of macrophage infectivity for several heterologous R5 envelopes, while the reciprocal G153E substitution abrogated infection. Shifts in macrophage tropism were associated with dramatic shifts in sensitivity to the V3 loop monoclonal antibody (MAb), 447-52D and soluble CD4, as well as more modest changes in sensitivity to the CD4bs MAb, b12. These observations are consistent with an altered conformation or exposure of the V3 loop that enables the envelope to use low CD4 levels for infection. The modest shifts in b12 sensitivity suggest that residue 153 impacts on the exposure of the CD4bs. However, the more intense shifts in sCD4 sensitivity suggest additional mechanisms that likely include an increased ability of the envelope to undergo conformational changes following binding to suboptimal levels of cell surface CD4. In summary, we show that a conserved determinant in the V1 loop modulates the V3 loop to prime low CD4 use and macrophage infection.

BACKGROUND: Children with severe bronchospasm requiring mechanical ventilation may become refractory to conventional therapy. In these critically ill patients, isoflurane is an inhaled anesthetic agent available in some centers to treat bronchospasm. We hypothesized that isoflurane is safe and would lead to improved gas exchange in children with life-threatening bronchospasm refractory to conventional therapy.

METHODS: A retrospective review was conducted and included mechanically ventilated children treated with isoflurane in a quaternary pediatric ICU for life-threatening bronchospasm, from 1993 to 2007. Demographic, blood gas, ventilator, and outcome data were collected.

RESULTS: Thirty-one patients, with a mean age of 9.5 years (range 0.4-23 years) were treated with isoflurane, from 1993 to 2007. Mean time to initiation of isoflurane after intubation was 13 hours (0-120 h), and the mean maximum isoflurane dose was 1.1% (0.3-2.5%). Mean duration of isoflurane administration was 54.5 hours (range 1-181 h), with a total mean duration of mechanical ventilation of 252 hours (range 16-1,444 h). Isoflurane led to significant improvement in pH and P(CO(2)) within 4 hours of initiation (P ≤ .001). Complications during isoflurane administration included hypotension requiring vasoactive infusions in 24 (77%), arrhythmia in 3 (10%), neurologic side effects in 3 (10%), and pneumothorax in 1 (3%) patient.

CONCLUSIONS: Isoflurane led to improvement in pH and P(CO(2)) within 4 hours in this series of mechanically ventilated patients with life-threatening bronchospasm. The majority of patients in this series developed hypotension, but there was a low incidence of other side effects related to isoflurane administration. Isoflurane appears to be an effective therapy in patients with life-threatening bronchospasm refractory to conventional therapy. However, further investigation is warranted, given the uncertain overall impact of isoflurane in this context.

OBJECTIVES: The objective of this study was to determine whether the use of heated, humidified, high-flow nasal cannula (HFNC) therapy is associated with a decreased need for intubation in patients presenting to a pediatric emergency department (PED) and admitted to a pediatric intensive care unit (PICU) with acute respiratory insufficiency (ARI).

METHODS: A retrospective study of all patients admitted from the PED to the PICU with ARI from January 2006 through December 2009. Patients admitted before the availability of HFNC (cohort 1) were compared with those admitted after the availability of HFNC but before implementation of an institution-wide guideline on pediatric HFNC usage (cohort 2) and those admitted after the implementation of a pediatric HFNC usage guideline (cohort 3).

RESULTS: After controlling for age, month of admission, type of respiratory illness, and severity of illness, there was an 83% reduction in the odds of intubation in the PED in cohort 3 compared with cohort 1 (odds ratio, 0.17; 95% confidence interval, 0.06-0.50; P = 0.001). There was no significant change in mortality or median PICU length of stay after the introduction of HFNC.

CONCLUSIONS: High-flow nasal cannula used early in the development of pediatric ARI is associated with a decreased the need for intubation and mechanical ventilation.