Human Macrophages Activate Bystander Neutrophils' Metabolism and Effector Functions When Challenged with Mycobacterium tuberculosis

Neutrophils are dynamic cells, playing a critical role in pathogen clearance; however, neutrophil infiltration into the tissue can act as a double-edged sword. They are one of the primary sources of excessive inflammation during infection, which has been observed in many infectious diseases including pneumonia and active tuberculosis (TB). Neutrophil function is influenced by interactions with other immune cells within the inflammatory lung milieu; however, how these interactions affect neutrophil function is unclear. Our study examined the macrophage-neutrophil axis by assessing the effects of conditioned medium (MΦ-CM) from primary human monocyte-derived macrophages (hMDMs) stimulated with LPS or a whole bacterium (Mycobacterium tuberculosis) on neutrophil function. Stimulated hMDM-derived MΦ-CM boosts neutrophil activation, heightening oxidative and glycolytic metabolism, but diminishes migratory potential. These neutrophils exhibit increased ROS production, elevated NET formation, and heightened CXCL8, IL-13, and IL-6 compared to untreated or unstimulated hMDM-treated neutrophils. Collectively, these data show that MΦ-CM from stimulated hMDMs activates neutrophils, bolsters their energetic profile, increase effector and inflammatory functions, and sequester them at sites of infection by decreasing their migratory capacity. These data may aid in the design of novel immunotherapies for severe pneumonia, active tuberculosis and other diseases driven by pathological inflammation mediated by the macrophage-neutrophil axis.

Chronic IFNα treatment induces leukopoiesis, increased plasma succinate and immune cell metabolic rewiring

Although clinically effective, the actions of IFNα, either produced endogenously or by therapeutic delivery, remain poorly understood. Emblematic of this research gap is the disparate array of notable side effects that occur in susceptible individuals, such as neuropsychiatric consequences, autoimmune phenomena, and infectious complications. We hypothesised that these complications are driven at least in part by dysregulated cellular metabolism. Male Wistar rats were treated with either 170,000 IU/kg human recombinant IFNα-2a or BSA/saline (0.9% NaCl) three times per week for three weeks. Bone marrow (BM) immune cells were isolated from the excised femurs for glycolytic rate and mitochondrial function assessment using Agilent Seahorse Technology. Frequencies of immune cell populations were assessed by flow cytometry to determine whether leukopoietic changes had occurred in both blood and BM. Plasma levels of lactate and succinate were also determined. BMDMs were metabolically assessed as above, as well as their metabolic response to an antigenic stimulus (iH37Rv). We observed that BM immune cells from IFN-treated rats exhibit a hypermetabolic state (increased basal OCR/GlycoPER) with decreased mitochondrial metabolic respiration and increased non-mitochondrial OCR. Flow cytometry results indicated an increase in immature granulocytes (RP1- SSChi CD45lo) only in the blood, together with increased succinate levels in the plasma. BMDMs from IFN-treated rats retained the hypermetabolic phenotype after differentiation and failed to induce a step-up in glycolysis and mitochondrial respiration after bacterial stimulation. This work provides the first evidence of the effects of IFNα treatment in inducing hypermetabolic immune features that are associated with markers of inflammation, leukopoiesis, and defective responses to bacterial stimulation.

SARS-CoV-2 spike and nucleocapsid proteins fail to activate human dendritic cells or γδ T cells

γδ T cells are thought to contribute to immunity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), but the mechanisms by which they are activated by the virus are unknown. Using flow cytometry, we investigated if the two most abundant viral structural proteins, spike and nucleocapsid, can activate human γδ T cell subsets, directly or in the presence of dendritic cells (DC). Both proteins failed to induce interferon-γ production by Vδ1 or Vδ2 T cells within fresh mononuclear cells or lines of expanded γδ T cells generated from healthy donors, but the same proteins stimulated CD3⁺ cells from COVID-19 patients. The nucleocapsid protein stimulated interleukin-12 production by DC and downstream interferon-γ production by co-cultured Vδ1 and Vδ2 T cells, but protease digestion and use of an alternative nucleocapsid preparation indicated that this activity was due to contaminating non-protein material. Thus, SARS-CoV-2 spike and nucleocapsid proteins do not have stimulatory activity for DC or γδ T cells. We propose that γδ T cell activation in COVID-19 patients is mediated by immune recognition of viral RNA or other structural proteins by γδ T cells, or by other immune cells, such as DC, that produce γδ T cell-stimulatory ligands or cytokines.

Human Hepatic CD56bright NK Cells Display a Tissue-Resident Transcriptional Profile and Enhanced Ability to Kill Allogenic CD8+ T Cells

Liver-resident CD56^brightCD16^- natural killer (NK) cells are enriched in the human liver and are phenotypically distinct from their blood counterparts. Although these cells are capable of rapid cytotoxic effector activity, their functional role remains unclear. We hypothesise that they may contribute to immune tolerance in the liver during transplantation. RNA sequencing was carried out on FACS sorted NK cell subpopulations from liver perfusates (n=5) and healthy blood controls (n=5). Liver-resident CD56^brightCD16^+/- NK cells upregulate genes associated with tissue residency. They also upregulate expression of CD160 and LY9, both of which encode immune receptors capable of activating NK cells. Co-expression of CD160 and Ly9 on liver-resident NK cells was validated using flow cytometry. Hepatic NK cell cytotoxicity against allogenic T cells was tested using an in vitro co-culture system of liver perfusate-derived NK cells and blood T cells (n=10-13). In co-culture experiments, hepatic NK cells but not blood NK cells induced significant allogenic T cell death (p=0.0306). Allogenic CD8⁺ T cells were more susceptible to hepatic NK cytotoxicity than CD4⁺ T cells (p<0.0001). Stimulation of hepatic CD56^bright NK cells with an anti-CD160 agonist mAb enhanced this cytotoxic response (p=0.0382). Our results highlight a role for donor liver NK cells in regulating allogenic CD8⁺ T cell activation, which may be important in controlling recipient CD8⁺ T cell-mediated rejection post liver-transplant.

Insights Into Human Intrahepatic NK Cell Function From Single Cell RNA Sequencing Datasets

Diverse populations of natural killer (NK) cells have been identified in circulating peripheral blood and a wide variety of different tissues and organs. These tissue-resident NK cell populations are phenotypically distinct from circulating NK cells, however, functional descriptions of their roles within tissues are lacking. Recent advances in single cell RNA sequencing (scRNA-seq) have enabled detailed transcriptional profiling of tissues at the level of single cells and provide the opportunity to explore NK cell diversity within tissues. This review explores potential novel functions of human liver-resident (lr)NK cells identified in human liver scRNA-seq studies. By comparing these datasets we identified up-regulated and down-regulated genes associated with lrNK cells clusters. These genes encode a number of activating and inhibiting receptors, as well as signal transduction molecules, which highlight potential unique pathways that lrNK cells utilize to respond to stimuli within the human liver. This unique receptor repertoire of lrNK cells may confer the ability to regulate a number of immune cell populations, such as circulating monocytes and T cells, while avoiding activation by liver hepatocytes and Kupffer cells. Validating the expression of these receptors on lrNK cells and the proposed cellular interactions within the human liver will expand our understanding of the liver-specific homeostatic roles of this tissue-resident immune cell population.

Liver-Derived TGF-β Maintains the EomeshiTbetlo Phenotype of Liver Resident Natural Killer Cells

The adult human liver hosts a complex repertoire of liver resident and transient natural killer (NK) cell populations with diverse phenotypes and functions. Liver resident NK cells are CD56^bright NK cells defined by a unique expression profile of transcription factors and cell surface markers (Eomes^hiTbet^loTIGIT⁺CD69⁺CXCR6⁺CD49e⁻). Despite extensive characterization of the phenotype of liver resident NK cells, it remains unclear how factors within the liver microenvironment induce and maintain this unique phenotype. In this study, we have explored the factors regulating the phenotype of liver resident NK cells. Isolation of healthy liver resident NK cells from donor liver perfusate and in vitro culture results in the gradual loss of the characteristic Tbet^lo phenotype, with the cells increasing Tbet expression significantly at day 7. This phenotypic loss could be halted through the dose-dependent addition of liver conditioned media (LCM), generated from the ex vivo culture of liver biopsies from healthy organ donors. TGF-β, but not IL-10, replicated the Tbet suppressive effects of LCM in both liver resident and peripheral blood NK cells. Furthermore, blocking TGF-β receptor signaling using the inhibitor SB431542, reversed the effect of LCM treatment on liver resident NK cells, causing the loss of tissue resident Eomes^hi Tbet^lo phenotype. Our findings identify liver-derived TGF-β as an important component of the liver microenvironment, which acts to regulate and maintain the phenotype of liver resident NK cells.

Dose-finding study of NKTR-102 in combination with cetuximab

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Background: NKTR-102 is an advanced polymer conjugate of irinotecan with broad single agent activity and a unique pharmacokinetic (pk) profile. The apparent half-life of the active metabolite SN-38 in patients (pts) administered NKTR-102 is approximately 50 days. NKTR-102 in combination with cetuximab was evaluated in pts with refractory solid tumors to define the maximum tolerated dose (MTD). Methods: NKTR-102 was infused over 90 minutes every 3 weeks per cycle. Cetuximab was infused over 2 hours at 400mg/m2 on day 1 followed by a weekly 1 hour infusion at 250mg/m2. Cohorts of 3 -12 pts were treated with escalating doses of NKTR- 102. MTD was established based on the dose limiting toxicities observed in cycle 1 and safety data from subsequent cycles. Serial plasma samples were collected throughout the study for PK analysis. Results: Eighteen pts were enrolled: main tumor types include colon (5), pancreas (4), rectal (2), breast (2), gastric (1), other (4). Pts received 100 mg/m2 (12) or 125 mg/m2 (6) of NKTR-102 for a median of 2.5 cycles (range 1 to 11+). At 125 mg/m2, 3 pts had G3 diarrhea, 1 in cycle 1; 2 in cycle 2. At 100mg/m2, 1 pt had G3 diarrhea in cycle 1 and a further pt had G4 fatigue in cycle 2. Other G3 toxicities for all patients in both dose groups include nausea (3), vomiting (3) and neutropenia (2). No G3 rash was reported. Partial responses (PR) were observed in 3 pts at 100 mg/m2: confirmed (rectal, colorectal) and unconfirmed (gastric). Another pt with pancreatic cancer had a decrease in CA19–9 from 2000 at baseline to 157 U/ml with associated symptomatic benefit. NKTR-102 resulted in sustained exposure to SN-38 with no evidence of PK drug interactions between NKTR-102 and cetuximab. Conclusions: NKTR-102 shows evidence of clinical antitumor activity in combination with cetuximab. Toxicity is manageable; diarrhea and neutropenia are dose limiting. The recommended dose of NKTR-102 with cetuximab is 100mg/m2 every three weeks. Data support further evaluation of this combination in appropriate tumor types.

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A mesoscale phytoplankton bloom in the polar Southern Ocean stimulated by iron fertilization

Changes in iron supply to oceanic plankton are thought to have a significant effect on concentrations of atmospheric carbon dioxide by altering rates of carbon sequestration, a theory known as the 'iron hypothesis'. For this reason, it is important to understand the response of pelagic biota to increased iron supply. Here we report the results of a mesoscale iron fertilization experiment in the polar Southern Ocean, where the potential to sequester iron-elevated algal carbon is probably greatest. Increased iron supply led to elevated phytoplankton biomass and rates of photosynthesis in surface waters, causing a large drawdown of carbon dioxide and macronutrients, and elevated dimethyl sulphide levels after 13 days. This drawdown was mostly due to the proliferation of diatom stocks. But downward export of biogenic carbon was not increased. Moreover, satellite observations of this massive bloom 30 days later, suggest that a sufficient proportion of the added iron was retained in surface waters. Our findings demonstrate that iron supply controls phytoplankton growth and community composition during summer in these polar Southern Ocean waters, but the fate of algal carbon remains unknown and depends on the interplay between the processes controlling export, remineralisation and timescales of water mass subduction.

The novel lipid delivery system of amphotericin B: drug profile and relevance to clinical practice

PURPOSE/OBJECTIVES

To review the drug profile and nursing implications associated with the new lipid amphotericin preparations.

DATA SOURCES

Published articles, abstracts, professional communications, drug manufacturer prescribing information, and personal experience.

DATA SYNTHESIS

Three lipid amphotericin B (AmB) preparations have been approved by the U.S. Food and Drug Administration (FDA). The first agent, amphotericin B lipid complex (Abelcet, Liposome Co., Princeton, NJ), a ribbon-like structure, was approved in November 1995 for the treatment of aspergillosis in patients who are refractory to or intolerant of conventional amphotericin B therapy and for invasive fungal infections. In November 1996, amphotericin B cholesteryl sulfate complex for injection (Amphotec, Sequus Pharmaceuticals, Menlo Park, CA), a second preparation composed of a disc-like structure, received FDA approval for the treatment of invasive aspergillosis in patients in whom renal impairment or unacceptable toxicity precludes the use of conventional AmB therapy and in patients in whom prior AmB therapy has failed. Amphotec frequently is referred to as amphotericin B colloidal dispersion (ABCD). The third formulation, a liposomal preparation composed of vesicles, liposomal amphotericin B or L-AmB (AmBisome, Fujisawa USA, Inc., Deerfield, IL, and Nexstar Co., Boulder, CO) recently received FDA approval for three indications. All of these preparations accumulate in organs of the reticuloendothelial system as opposed to the kidneys. Further studies of lipid AmB are needed to help clarify the usefulness of each AmB preparation. The most common side effects of lipid AmB preparations are chills and fever.

CONCLUSIONS

Lipid-based AmB preparations are well-tolerated treatments with mild to moderate side effects. These preparations have some advantages over conventional AmB.

IMPLICATIONS FOR NURSING PRACTICE

Nurses in clinical settings can focus on staff and patient education, including identification and management of side effects associated with the lipid-based AmB preparations. Patient-care concerns include appropriate patient selection, dosing and administration issues, and the prevention, early identification, and management of toxicities.