Abstract A large proportion of HIV-coinfected visceral leishmaniasis (VL-HIV) patients exhibit chronic disease with frequent VL recurrence. However, knowledge on immunological determinants underlying the disease course is scarce. We longitudinally profiled the circulatory cellular immunity of an Ethiopian HIV cohort that included VL developers. We show that chronic VL-HIV patients exhibit high and persistent levels of TIGIT and PD-1 on CD8+/CD8- T cells, in addition to a lower frequency of IFN-γ+ TIGIT- CD8+/CD8- T cells, suggestive of impaired T cell functionality. At single T cell transcriptome and clonal resolution, the patients show CD4+ T cell anergy, characterised by a lack of T cell activation and lymphoproliferative response. These findings suggest that PD-1 and TIGIT play a pivotal role in VL-HIV chronicity, and may be further explored for patient risk stratification. Our findings provide a strong rationale for adjunctive immunotherapy for the treatment of chronic VL-HIV patients to break the recurrent disease cycle.

OBJECTIVE:Causes of acute febrile illness (AFI) often remain undetermined in developing countries, due to overlap of symptoms and limited available diagnostics. We aimed to assess the aetiology of AFI in adults in a referral hospital in northwest Ethiopia.METHODS:While all participants were tested for malaria by rapid diagnostic test (RDT), microscopy was only done on physician's request. Dengue virus (DENV) infections were detected using an RDT and ELISAs and dengue, yellow fever and chikungunya cases were identified by PCR. Bacterial aetiologies were investigated using blood culture and PCR.RESULTS:The aetiology of acute infection was identified for 20.5% of 200 patients enrolled. Eleven percent tested positive for Plasmodium, while microscopy was only requested for half of the identified malaria cases. For 4.0% of the Plasmodium-infected patients, an acute or past DENV (co-)infection was detected. We found 7.5% acute and 13.0% past DENV - all serotype 3 - infections. Bacterial infections were observed in 4.5% of the patients.CONCLUSION:Malaria is still a considerable aetiology of AFI and dengue is underrecognised. There are areas where both diseases occur concomitantly, and the DENV-3 serotype presumably spreads from Sudan to northern Ethiopia. As only 20.5% of the aetiologies were identified, a broader testing platform is required.

Contact tracing is one of several strategies employed in many countries to curb the spread of SARS-CoV-2. Digital contact tracing (DCT) uses tools such as cell-phone applications to improve tracing speed and reach. We model the impact of DCT on the spread of the virus for a large epidemiological parameter space consistent with current literature on SARS-CoV-2. We also model DCT in combination with random testing (RT) and social distancing (SD). Modelling is done with two independently developed individual-based (stochastic) models that use the Monte Carlo technique, benchmarked against each other and against two types of deterministic models. For current best estimates of the number of asymptomatic SARS-CoV-2 carriers (approximately 40%), their contagiousness (similar to that of symptomatic carriers), the reproductive number before interventions ( R0 at least 3) we find that DCT must be combined with other interventions such as SD and/or RT to push the reproductive number below one. At least 60% of the population would have to use the DCT system for its effect to become significant. On its own, DCT cannot bring the reproductive number below 1 unless nearly the entire population uses the DCT system and follows quarantining and testing protocols strictly. For lower uptake of the DCT system, DCT still reduces the number of people that become infected. When DCT is deployed in a population with an ongoing outbreak where O (0.1%) of the population have already been infected, the gains of the DCT intervention come at the cost of requiring up to 15% of the population to be quarantined (in response to being traced) on average each day for the duration of the epidemic, even when there is sufficient testing capability to test every traced person.

We propose a decentralized digital contact tracing service that preserves the users' privacy by design while complying to the highest security standards. Our approach is based on Bluetooth and measures actual encounters of people, the contact time period, and estimates the proximity of the contact. We trace the users' contacts and the possible spread of infectious diseases while preventing location tracking of users, protecting their data and identity. We verify and improve the impact of tracking based on epidemiological models. We compare a centralized and decentralized approach on a legal perspective and find a decentralized approach preferable considering proportionality and data minimization.

Current sampling methods to diagnose cutaneous leishmaniasis are invasive and painful. An alternative and minimally invasive microbiopsy device was evaluated in a diverse range of cutaneous leishmaniasis lesions in Ethiopia. Using polymerase chain reaction-based diagnosis, the microbiopsy outperformed the routine skin slit sample by detecting more patients while pain scores were significantly lower.

ObjectivesIn low-resource settings, treatment is often given empirically without knowledge of the aetiology due to a lack of diagnostics. In the search for reliable rapid tests to guide treatment work-up, this study was performed to determine whether two biomarkers could differentiate bacterial from non-bacterial infections in acute febrile patients.MethodsAdults with acute fever were recruited at a referral hospital in Ethiopia. The QuikRead Go test was used to quantify C-reactive protein (qCRP) and the FebriDx test was used for combined qualitative detection of the bacterial CRP marker with myxovirus resistance protein A (MxA), a viral biomarker.ResultsOf the 200 patients included in this study, most presented with 2–3 days of fever, headache, and joint pain. Antibiotics were prescribed for 83.5% and antimalarials for 36.5%, while a bacterial infection was only confirmed in 5% and malaria in 11%. The median qCRP level for confirmed bacterial infections was 128 mg/l. The FebriDx and QuikRead Go test had an overall agreement of 72.0%.ConclusionsAn over-prescription of antibiotics for febrile patients was observed, even for those with low CRP levels and without a confirmed bacterial infection. The added value of the FebriDx was limited, while the combined use of rapid tests for qCRP and malaria should be considered for the management of acute febrile illness and antibiotic stewardship.

Background & Aims: Natural killer (NK) cells are found at increased frequencies in patients with hepatitis C virus (HCV). NK cell activation has been shown to correlate with HCV clearance and to predict a favourable treatment response. The aim of our study was to dissect mechanisms leading to NK cell activation and proliferation in response to HCV. Methods: NK cell phenotype, proliferation, and function were assessed after the 6-day co-culture of human peripheral blood mononuclear cells with either HCV replicon-containing HuH6 hepatoblastoma cells or HCV-infected HuH7.5 cells. The results obtained were confirmed by immunohistochemistry of liver biopsies from patients with HCV and from HCV-negative controls. Results: In HCV-containing co-cultures, a higher frequency of NK cells upregulated the expression of the high-affinity IL-2 receptor chain CD25, proliferated more rapidly, and produced higher amounts of interferon gamma compared with NK cells from control co-cultures. This NK cell activation was dependent on IL-2, cell-cell contact-mediated signals, and HCV replicon-exposed monocytes. The tumour necrosis factor-receptor superfamily member OX40 was induced on the activated CD25(+/-) NK cell subset and this induction was abrogated by the depletion of CD14(+) monocytes. Moreover, OX40L was upregulated on CD14(+/-) monocyte-derived cells co-cultured with HCV-containing cells and also observed in liver biopsies from patients with HCV. Importantly, blocking of the OX40/OX40L interaction abolished both NK cell activation and proliferation. Conclusions: Our results uncover a previously unappreciated cell-cell contact-mediated mechanism of NK cell activation and proliferation in response to HCV, mediated by monocyte-derived cells and the OX40/OX40L axis. These results reveal a novel mode of crosstalk between innate immune cells during viral infection. Lay summary: Using a cell-culture model of hepatitis C virus (HCV) infection, our study revealed that natural killer (NK) cells become activated and proliferate when they are co-cultured with HCV-containing liver cells. The mechanism of this activation involves crosstalk with other innate immune cells and a cell-cell contact interaction mediated by the cell surface molecules OX40 and OX40L. Our study reveals a novel pathway leading to NK cell proliferation and activation against virus-infected cells that might be of relevance in antiviral immunity. (C) 2017 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.

Hepatitis C virus (HCV) and human cytomegalovirus (HCMV) are prominent examples of RNA and DNA viruses, respectively, that establish a persistent infection in their host. HCV affects over 185 million patients worldwide, who are at high risk for developing liver fibrosis, liver cirrhosis, and ultimately hepatocellular carcinoma. Recent breakthroughs in HCV therapy, using direct-acting antivirals have provided the opportunity to monitor natural killer (NK) cells after clearance of a chronic infection. There is now increasing evidence that the individual NK cell repertoire before infection is predictive for the course of disease. HCMV affects the majority of the global population. While being asymptomatic in healthy individuals, HCMV represents a severe clinical challenge in immunocompromised patients. Both viral infections, HCV and HCMV, lead to long-lasting and profound alterations within the entire NK cell compartment. This review article, will discuss the diverse range of changes in the NK cell compartment as well as potential consequences for the course of disease.

Natural Killer (NK) cells are innate effector cells that are able to recognize and eliminate tumor cells through engagement of their surface receptors. NKp30 is a potent activating NK cell receptor that elicits efficient NK cell-mediated target cell killing. Recently, B7-H6 was identified as tumor cell surface expressed ligand for NKp30. Enhanced B7-H6 mRNA levels are frequently detected in tumor compared to healthy tissues. To gain insight in the regulation of expression of B7-H6 in tumors, we investigated transcriptional mechanisms driving B7-H6 expression by promoter analyses. Using luciferase reporter assays and chromatin immunoprecipitation we mapped a functional binding site for Myc, a proto-oncogene overexpressed in certain tumors, in the B7-H6 promoter. Pharmacological inhibition or siRNA/shRNA-mediated knock-down of c-Myc or N-Myc significantly decreased B7-H6 expression on a variety of tumor cells including melanoma, pancreatic carcinoma and neuroblastoma cell lines. In tumor cell lines from different origin and primary tumor tissues of hepatocellular carcinoma (HCC), lymphoma and neuroblastoma, mRNA levels of c-Myc positively correlated with B7-H6 expression. Most importantly, upon inhibition or knock-down of c-Myc in tumor cells impaired NKp30-mediated degranulation of NK cells was observed. Thus, our data imply that Myc driven tumors could be targets for cancer immunotherapy exploiting the NKp30/B7-H6 axis.

Natural Killer (NK) cells are important effector cells in Hepatitis C Virus (HCV) infection, a virus that chronically infects around 2.5% of the world population and is a major cause of liver disease and hepatocellular carcinoma. The exact mechanisms, however, through which NK cells are activated in response to HCV remain elusive. Using the well-established HCV replicon cell-culture model we show that after co- culture of HCV replicon-carrying hepatocytes with peripheral blood mononuclear cells (PBMCs), NK cells increase expression of the high-affinity IL-2 receptor chain CD25, proliferate rapidly and produce IFN-gamma. Activation of NK cells was dependent on IL-2, most likely produced by T cells and on cell-cell contact mediated signals from monocytes. Monocytes from replicon-carrying co-cultures showed increased expression of OX40L, a member of the tumor necrosis factor family and concurrently its receptor OX40 was increased on NK cells. Blocking of OX40L in those co-cultures, as well as depletion of CD14+ monocytes abrogated the virus-induced activation and effector functions of NK cells. Together, our data reveals a novel mechanism of monocyte mediated NK cell activation against virus-infected cells involving the OX40/OX40L axis with potential relevance for therapeutic intervention by e.g. agonistic antibodies against OX40, which are already tested in cancer therapy.

Human cytomegalovirus (HCMV) infection is the most common cause of congenital viral infections and a major source of morbidity and mortality after organ transplantation. NK cells are pivotal effector cells in the innate defense against CMV. Recently, hallmarks of adaptive responses, such as memory-like features, have been recognized in NK cells. HCMV infection elicits the expansion of an NK cell subset carrying an activating receptor heterodimer, comprising CD94 and NKG2C (CD94/NKG2C), a response that resembles the clonal expansion of adaptive immune cells. Here, we determined that expansion of this NKG2C(+) subset and general NK cell recovery rely on signals derived from CD14(+) monocytes. In a coculture system, a subset of CD14(+) cells with inflammatory monocyte features produced IL-12 in response to HCMV-infected fibroblasts, and neutralization of IL-12 in this model substantially reduced CD25 upregulation and NKG2C(+) subset expansion. Finally, blockade of CD94/NKG2C on NK cells or silencing of the cognate ligand HLA-E in infected fibroblasts greatly impaired expansion of NKG2C(+) NK cells. Together, our results reveal that IL-12, CD14(+) cells, and the CD94/NKG2C/HLA-E axis are critical for the expansion of NKG2C(+) NK cells in response to HCMV infection. Moreover, strategies targeting the NKG2C(+) NK cell subset have the potential to be exploited in NK cell-based intervention strategies against viral infections and cancer.

Many previous reports on Natural Killer (NK) cells highlighted their ability to form the proverbial first line of defense against a variety of viral infections and malignancies. NK cells have been considered a part of innate immunity, characterized by invariant, germ-line encoded receptors for the recognition of pathogens and infected cells. In contrast, somatic rearrangement of receptor genes, the clonal expansion of antigen-specific cells, and the ability to mount a more potent memory response upon secondary challenge are traditionally considered hallmarks of T and B cells belonging to the adaptive immune system. More recently, exciting new data are challenging this conventional view [1]. A growing body of evidence indicates that under certain experimental conditions, NK cells share some of the features of adaptive immune cells. For instance, in mice infected with murine cytomegalovirus (MCMV), an NK cell subset expands in an antigen-dependent manner reminiscent of the clonal expansion of adaptive immune cells [2]. This NK cell expansion is associated with long-lasting functional changes similar to features of memory T cell populations. Resemblances between NK and T cells are not only limited to their response kinetics and certain functions, but also comprise characteristics of homeostatic proliferation, development, and differentiation [3]. Currently, a clear consensus on how the term “memory” is defined in NK cell biology is lacking. Throughout this article we will refer to memory NK cells, if these NK cells respond more potently to a second challenge with the same antigen they had initially encountered (Figure 1). The term “memory-like” NK cells will be used when long-lasting functional alterations are induced, e.g. by cytokines without clear evidence of antigen involvement (Figure 1). Figure 1 Memory and memory-like NK cells in mice and humans.