Factors influencing mercury exposure in Arctic-breeding shorebirds.

Mercury (Hg) pollution remains a concern to Arctic ecosystems, due to long-range transport from southern industrial regions and melting permafrost and glaciers. The objective of this study was to identify intrinsic, extrinsic, and temporal factors influencing Hg concentrations in Arctic-breeding shorebirds and highlight regions and species at greatest risk of Hg exposure. We analyzed 1094 blood and 1384 feather samples from 12 shorebird species breeding at nine sites across the North American Arctic during 2012 and 2013. Blood Hg concentrations, which reflect Hg exposure in the local area in individual shorebirds: 1) ranged from 0.01-3.52 µg/g ww, with an overall mean of 0.30 ± 0.27 µg/g ww; 2) were influenced by species and study site, but not sampling year, with birds sampled near Utqiagvik, AK, having the highest concentrations; and 3) were influenced by foraging habitat at some sites. Feather Hg concentrations, which reflected Hg exposure from the wintering grounds: 1) ranged from 0.07-12.14 µg/g fw in individuals, with an overall mean of 1.14 ± 1.18 µg/g fw; and 2) were influenced by species and year. Most Arctic-breeding shorebirds had blood and feather Hg concentrations at levels where no adverse effects of exposure were predicted, though some individuals sampled near Utqiagvik had Hg levels that would be considered of concern. Overall, these data increase our understanding of how Hg is distributed in the various shorebird breeding areas of the Arctic, what factors predispose Arctic-breeding shorebirds to Hg exposure, and lay the foundation for future monitoring efforts.

Nontyphoidal Salmonella Osteomyelitis in Immunocompetent Children Without Hemoglobinopathies: A Case Series and Systematic Review of the Literature.

Salmonella osteomyelitis is well-described in children with hemoglobinopathies, particularly infection with Salmonella typhi. To characterize nontyphoidal osteomyelitis in otherwise healthy children without hemoglobinopathies, we performed a retrospective review of children discharged from our institution with this condition, supplemented with a systematic literature review. Among the 46 subjects identified, common risk factors for Salmonella infection were frequently absent and complications were common.

Non-Type b Haemophilus influenzae Septic Arthritis in Children.

Invasive disease caused by non-type b Haemophilus influenzae serotypes has been increasingly reported. Although to date it has been a rarely described cause of septic arthritis, we present 10 cases of non-type b H influenzae septic arthritis in children seen in a tertiary care center that serves a large Native American population.

Pharmacotherapy of sepsis.

Treatment of sepsis involves prompt recognition and treatment to optimize outcome. Several medication considerations are pertinent to patients with sepsis, severe sepsis, and septic shock. Medications play a crucial role in providing resuscitation, hemodynamic support, resolution of infection, and reduction of complications of the disease. Over the past 20 years, significant focus has been devoted to the pharmacologic treatment of septic shock, resulting in significant advances and controversies. Ongoing research will continue to focus on this disease process and will continue to shape treatment in the future. The use of medication therapies directed at treatment of sepsis will be reviewed in this article.

CD4+ CD25+ regulatory T cells impair HIV-1-specific CD4 T cell responses by upregulating interleukin-10 production in monocytes.

T cell dysfunction in the presence of ongoing antigen exposure is a cardinal feature of chronic viral infections with persistent high viremia, including HIV-1. Although interleukin-10 (IL-10) has been implicated as an important mediator of this T cell dysfunction, the regulation of IL-10 production in chronic HIV-1 infection remains poorly understood. We demonstrated that IL-10 is elevated in the plasma of individuals with chronic HIV-1 infection and that blockade of IL-10 signaling results in a restoration of HIV-1-specific CD4 T cell proliferation, gamma interferon (IFN-γ) secretion, and, to a lesser extent, IL-2 production. Whereas IL-10 blockade leads to restoration of IFN-γ secretion by HIV-1-specific CD4 T cells in all categories of subjects investigated, significant enhancement of IL-2 production and improved proliferation of CD4 T helper cells are restricted to viremic individuals. In peripheral blood mononuclear cells (PBMCs), this IL-10 is produced primarily by CD14(+) monocytes, but its production is tightly controlled by regulatory T cells (Tregs), which produce little IL-10 directly. When Tregs are depleted from PBMCs of viremic individuals, the effect of the IL-10 signaling blockade is abolished and IL-10 production by monocytes decreases, while the production of proinflammatory cytokines, such as tumor necrosis factor alpha (TNF-α), increases. The regulation of IL-10 by Tregs appears to be mediated primarily by contact or paracrine-dependent mechanisms which involve IL-27. This work describes a novel mechanism by which regulatory T cells control IL-10 production and contribute to dysfunctional HIV-1-specific CD4 T cell help in chronic HIV-1 infection and provides a unique mechanistic insight into the role of regulatory T cells in immune exhaustion.

Responsiveness of HIV-specific CD4 T cells to PD-1 blockade.

Defining the T helper functions impaired by programmed death-1 (PD-1) is crucial for understanding its role in defective HIV control and determining the therapeutic potential of targeting this inhibitory pathway. We describe here the relationships among disease stage, levels of PD-1 expression, and reversibility of CD4 T-cell impairment. PD-L1 blockade in vitro enhanced HIV-specific production of Th0 (IL-2), Th1 (IFN-γ), Th2 (IL-13), and TFH (IL-21) cytokines by CD4 T cells. PD-L1 blockade caused an early increase in cytokine transcription and translation that preceded cell proliferation. Although the impact of PD-L1 blockade on cytokine expression and, to a lesser extent, cell proliferation was associated with markers of disease progression, restoration of cytokine secretion was also observed in most subjects with undetectable viremia. PD-L1 blockade restored cytokine secretion in both PD-1intermediate and PD-1high sorted CD4 T-cell subsets. Compared with PD-1high HIV-specific CD8 T cells, PD-1high HIV-specific CD4 T cells showed lower expression of the inhibitory molecules CD160 and 2B4, demonstrating marked differences in expression of inhibitory receptors between T-cell subsets. These data show that PD-1 impairs HIV-specific T helper responses both by limiting expansion of these cells and by inhibiting effector functions of multiple differentiated CD4 T-cell subsets.

IL-10 is up-regulated in multiple cell types during viremic HIV infection and reversibly inhibits virus-specific T cells.

Murine models indicate that interleukin-10 (IL-10) can suppress viral clearance, and interventional blockade of IL-10 activity has been proposed to enhance immunity in chronic viral infections. Increased IL-10 levels have been observed during HIV infection and IL-10 blockade has been shown to enhance T-cell function in some HIV-infected subjects. However, the categories of individuals in whom the IL-10 pathway is up-regulated are poorly defined, and the cellular sources of IL-10 in these subjects remain to be determined. Here we report that blockade of the IL-10 pathway augmented in vitro proliferative capacity of HIV-specific CD4 and CD8 T cells in individuals with ongoing viral replication. IL-10 blockade also increased cytokine secretion by HIV-specific CD4 T cells. Spontaneous IL-10 expression, measured as either plasma IL-10 protein or IL-10 mRNA in peripheral blood mononuclear cells (PBMCs), correlated positively with viral load and diminished after successful antiretroviral therapy. IL-10 mRNA levels were up-regulated in multiple PBMC subsets in HIV-infected subjects compared with HIV-negative controls, particularly in T, B, and natural killer (NK) cells, whereas monocytes were a major source of IL-10 mRNA in HIV-infected and -uninfected individuals. These data indicate that multiple cell types contribute to IL-10-mediated immune suppression in the presence of uncontrolled HIV viremia.