Metabolic Reprogramming Supports IFN-γ Production by CD56bright NK Cells.

Human NK cells can be classified into phenotypically and functionally distinct subsets based on levels of CD56 receptor. CD56(dim) cells are generally considered more cytotoxic, whereas the CD56(bright) cells are potent producers of IFN-γ. In this study, we define the metabolic changes that occur in peripheral blood NK cells in response to cytokine. Metabolic analysis showed that NK cells upregulate glycolysis and oxidative phosphorylation in response to either IL-2 or IL-12/15 cytokine combinations. Despite the fact that both these cytokine combinations robustly upregulated mammalian Target of Rapamycin Complex 1 in human NK cells, only the IL-2-induced metabolic changes were sensitive to mammalian Target of Rapamycin Complex 1 inhibition by rapamycin. Interestingly, we found that CD56(bright) cells were more metabolically active compared with CD56(dim) cells. They preferentially upregulated nutrient receptors and also differed substantially in terms of their glucose metabolism. CD56(bright) cells expressed high levels of the glucose uptake receptor, Glut1 (in the absence of any cytokine), and had higher rates of glucose uptake compared with CD56(dim) cells. Elevated levels of oxidative phosphorylation were required to support both cytotoxicity and IFN-γ production in all NK cells. Finally, although elevated glycolysis was not required directly for NK cell degranulation, limiting the rate of glycolysis significantly impaired IFN-γ production by the CD56(bright) subset of cells. Overall, we have defined CD56(bright) NK cells to be more metabolically active than CD56(dim) cells, which supports their production of large amounts of IFN-γ during an immune response.

Mechanism of outside-in {alpha}IIb{beta}3-mediated activation of human platelets by the colonizing Bacterium, Streptococcus gordonii.

OBJECTIVE: To better understand the mechanism of platelet recruitment and activation by Streptococcus gordonii. The oral bacterium Streptococcus gordonii, is amongst the most common pathogens isolated from infective endocarditis patients, and has the property of being able to activate platelets, leading to thrombotic complications. The mechanism of platelet recruitment and activation by S. gordonii is poorly understood. METHODS AND RESULTS: Infective endocarditis is a bacterial infection of the heart valves that carries a high risk of morbidity and mortality. The oral bacterium, S gordonii, is among the most common pathogens isolated from patients with infective endocarditis and is able to activate platelets, leading to thrombotic complications. Platelets interact with S gordonii via glycoprotein Ibα- and α(IIb)ß(3)-recognizing S gordonii surface proteins haemaglutitin salivary antigen (Hsa) and platelet adherence protein A, respectively. The inhibition of glycoprotein Ibα or α(IIb)ß(3) using blocking antibodies or deletion of S gordonii Hsa or platelet adherence protein A significantly reduces platelet adhesion. Immunoreceptor tyrosine-based activation motif (ITAM)-containing proteins have recently played a role in transmitting activating signals into platelets. Platelet adhesion to immobilized S gordonii resulted in tyrosine phosphorylation of the ITAM-bearing receptor, FcγRIIa, and phosphorylation of downstream effectors (ie, spleen tyrosine kinase [Syk] and phospholipase C [PLC]-γ2). Tyrosine phosphorylation of FcγRIIa resulted in platelet-dense granule secretion, filopodial and lamellipodial extension, and platelet spreading. Inhibition of FcγRIIa ablated both dense granule release and platelet spreading. CONCLUSIONS: Streptococcus gordonii binding to the α(IIb)ß(3)/FcγRIIa integrin/ITAM signaling complex results in platelet activation that likely contributes to the thrombotic complications of infective endocarditis.

The prehospital patient pathway and experience of care with acute heart failure: a comparison of two health care systems.

AIMS: This study aimed to analyse community management of patients during the symptomatic period prior to admission with acute decompensated heart failure (ADHF). METHODS AND RESULTS: We conducted a prospective, two-centre, two-country observational study evaluating care pathways and patient experience in patients admitted to hospital with ADHF. Quantitative and qualitative data were gathered from patients, carers, and general practitioners (GPs). From the Irish centre, 114 patients enrolled, and from the English centre, 50 patients. Symptom duration longer than 72 h prior to hospitalization was noted among 70.4% (76) Irish and 80% (40) English patients, with no significant difference between those with a new diagnosis of HF [de novo HF (dnHF)] and those with known HF [established HF (eHF)] in either cohort. For the majority, dyspnoea was the dominant symptom; however, 63.3% (31) of these Irish patients and 47.2% (17) of these English patients did not recognize this as an HF symptom, with no significant difference between dnHF and eHF patients. Of the 46.5% (53) of Irish and 38% (19) of English patients reviewed exclusively by GPs before hospitalization, numbers prescribed diuretics were low (11.3%, six; and 15.8%, three, respectively); eHF patients were no more likely to receive diuretics than dnHF patients. Barriers to care highlighted by GPs included inadequate access to basic diagnostics, specialist support and up-to-date patient information, and lack of GP comfort in managing HF. CONCLUSION: The aforementioned findings, consistent across both health care jurisdictions, show a clear potential to intervene earlier and more effectively in ADHF or to prevent the need for hospitalization.

Human platelets recognize a novel surface protein, PadA, on Streptococcus gordonii through a unique interaction involving fibrinogen receptor GPIIbIIIa.

The concept of an infectious agent playing a role in cardiovascular disease is slowly gaining attention. Among several pathogens identified, the oral bacterium Streptococcus gordonii has been implicated as a plausible agent. Platelet adhesion and subsequent aggregation are critical events in the pathogenesis and dissemination of the infective process. Here we describe the identification and characterization of a novel cell wall-anchored surface protein, PadA (397 kDa), of S. gordonii DL1 that binds to the platelet fibrinogen receptor GPIIbIIIa. Wild-type S. gordonii cells induced platelet aggregation and supported platelet adhesion in a GPIIbIIIa-dependent manner. Deletion of the padA gene had no effect on platelet aggregation by S. gordonii but significantly reduced (>75%) platelet adhesion to S. gordonii. Purified N-terminal PadA recombinant polypeptide adhered to platelets. The padA mutant was unaffected in production of other platelet-interactive surface proteins (Hsa, SspA, and SspB), and levels of adherence of the mutant to fetuin or platelet receptor GPIb were unaffected. Wild-type S. gordonii, but not the padA mutant, bound to Chinese hamster ovary cells stably transfected with GPIIbIIIa, and this interaction was ablated by addition of GPIIbIIIa inhibitor Abciximab. These results highlight the growing complexity of interactions between S. gordonii and platelets and demonstrate a new mechanism by which the bacterium could contribute to unwanted thrombosis.

Role of Streptococcus gordonii surface proteins SspA/SspB and Hsa in platelet function.

Streptococcus gordonii colonization of damaged heart surfaces in infective endocarditis is dependent upon the recognition of host receptors by specific bacterial surface proteins. However, despite several attempts to identify the mechanisms involved in this interaction, the nature of the bacterial proteins required remains poorly understood. This study provides clear evidence that several S. gordonii surface proteins participate in the interaction with platelets to support platelet adhesion and induce platelet aggregation. S. gordonii strains were found to support strong (DL1-Challis, SK12, SK184, and Blackburn) or moderate (UB1545 delta hsa and CH1-Challis) adhesion or failed to support platelet adhesion (M5, M99, and Channon). In addition, under flow conditions, platelets rolled and subsequently adhered to immobilized S. gordonii at low shear (50 s(-1)) in an Hsa-dependent manner but did not interact with S. gordonii DL1 at any shear rate of >50 s(-1). S. gordonii strains either induced (DL1-Challis, SK12, SK184, UB1545 delta hsa, and M99) or failed to induce (M5, CH1-Challis, Channon, and Blackburn) platelet aggregation. Using a proteomic approach to identify differential cell wall protein expression between aggregating (DL1) and nonaggregating (Blackburn) strains, we identified antigen I/antigen II family proteins SspA and SspB. The overexpression of SspA or SspB in platelet-nonreactive Lactococcus lactis induced GPIIb/GPIIIa-dependent platelet aggregation similar to that seen with S. gordonii DL1. However, they failed to support platelet adhesion. Thus, S. gordonii has distinct mechanisms for supporting platelet adhesion and inducing platelet aggregation. Differential protein expression between strains may be important for the pathogenesis of invasive diseases such as infective endocarditis.

Heart Failure Virtual Consultation: bridging the gap of heart failure care in the community - A mixed-methods evaluation.

AIMS: We undertook a mixed-methods evaluation of a Web-based conferencing service (virtual consult) between general practitioners (GPs) and cardiologists in managing patients with heart failure in the community to determine its effect on use of specialist heart failure services and acceptability to GPs. METHODS AND RESULTS: All cases from June 2015 to October 2016 were recorded using a standardized recording template, which recorded patient demographics, medical history, medications, and outcome of the virtual consult for each case. Quantitative surveys and qualitative interviewing of 17 participating GPs were also undertaken. During this time, 142 cases were discussed-68 relating to a new diagnosis of heart failure, 53 relating to emerging deterioration in a known heart failure patient, and 21 relating to therapeutic issues. Only 17% required review in outpatient department following the virtual consultation. GPs reported increased confidence in heart failure management, a broadening of their knowledge base, and a perception of overall better patient outcomes. CONCLUSIONS: These data from an initial experience with Heart Failure Virtual Consultation present a very positive impact of this strategy on the provision of heart failure care in the community and acceptability to users. Further research on the implementation and expansion of this strategy is warranted.

IFNL cytokines do not modulate human or murine NK cell functions.

The interferon-lambda (IFNL) cytokines have been shown to be important in HCV infection with SNPs in the IFNL3 gene associated with both natural and treatment induced viral clearance. We have recently shown that rs1299860 (an IFNL3 associated SNP) and an NK cell gene, KIR2DS3, synergised to increase the odds of chronic infection in a homogenous cohort of Irish women infected with HCV. To characterise a biological basis for the genetic synergy, we investigated for any evidence that IFNL cytokines regulate NK cell functions. Using a range of functional responses, we did not find any evidence of NK cell activation by IFNL3, IFNL1 or IFNL2 cytokines. Similar results were found using human and murine NK cells. In addition, and in contrast to our preliminary study, we did not find any evidence that IFNL cytokines inhibited NK cell cytokine production; thus, the biological basis for the genetic synergy remains to be discovered.

Variation in both IL28B and KIR2DS3 genes influence pegylated interferon and ribavirin hepatitis C treatment outcome in HIV-1 co-infection.

Pegylated-IFN and ribavirin remains the current treatment for chronic HCV infection in patients co-infected with HIV-1, but this regimen has low efficacy rates, particularly for HCV genotype 1/4 infection, has severe side effects and is extremely costly. Therefore, accurate prediction of treatment response is urgently required. We have recently shown that the NK cell gene, KIR2DS3 and a SNP associated with the IL28B gene synergise to increase the risk of chronic infection in primary HCV mono-infected patients. Identification of SNPs associated with the IL28B gene has also proven very powerful for predicting patient response to treatment. Patients co-infected with HIV-1 are of particular concern given they respond less well to HCV treatment, have more side effects and suffer a more rapid liver disease progression. In this study, we examined both IL28B and KIR2DS3 for their ability to predict treatment response in a cohort of HIV-1/HCV co-infected patients attending two treatment centres in Europe. We found that variation in both host genetic risk factors, IL28B and KIR2DS3, was strongly associated with sustained virological response (SVR) to treatment in our co-infected cohort (n = 149). The majority of patients who achieved a rapid virological response (RVR) achieved a SVR. However, it is currently impossible to predict treatment outcome in patients who fail to achieve an RVR. In our cohort, the presence of host genetic risk factors, IL28B-T and KIR2DS3 alleles, resulted in increased odds of treatment failure in these RVR negative patients (n = 88). Our data suggests that testing for host genetic factors will improve predicting treatment responsiveness in the clinical management of co-infected patients, and provides further evidence of the importance of the innate immune system in the immune response to HCV.

Multiple sites on Streptococcus gordonii surface protein PadA bind to platelet GPIIbIIIa.

Infective endocarditis is a life threatening disease caused by a bacterial infection of the endocardial surfaces of the heart. The oral pathogen, Streptococcus gordonii is amongst the most common pathogens isolated from infective endocarditis patients. Previously we identified a novel cell wall protein expressed on S. gordonii called platelet adherence protein A (PadA) that specifically interacts with platelet GPIIb/IIIa. The interaction between PadA and GPIIb/IIIa resulted in firm platelet adhesion, dense granule secretion and platelet spreading on immobilised S. gordonii. This study set out to identify specific motifs on the PadA protein that interacts with platelet GPIIb/IIIa. Proteomic analysis of the PadA protein identified two short amino acid motifs which have been previously shown to be important for fibrinogen binding to GPIIb/IIIa and contributing to the generation of outside-in signalling. Site directed mutagenesis on the PadA protein in which 454AGD was substituted to AAA, and the 383RGT was substituted to AAA suggests the RGT motif has no role in supporting platelet adhesion however plays a role in dense granule secretion and platelet spreading. In contrast to this the AGD motif has no role to play in supporting firm platelet adhesion or dense granule secretion however plays a role in platelet spreading. These results suggest that multiple sites on S. gordonii PadA interact with GPIIb/IIIa to mediate a number of platelet responses that likely contribute to the thrombotic complications of infective endocarditis.