Aetiologies of acute undifferentiated febrile illness at the emergency ward of the University of Gondar Hospital, Ethiopia.

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.

Hepatitis C virus-induced natural killer cell proliferation involves monocyte-derived cells and the OX40/OX40L axis.

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 γ 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.

Molar Activity of Ga-68 Labeled PSMA Inhibitor Conjugates Determines PET Imaging Results.

Radiopharmaceuticals targeting the enzyme prostate-specific membrane antigen (PSMA; synonyms: glutamate carboxypeptidase II, NAALADase; EC 3.4.17.21) have recently emerged as powerful agents for diagnosis and therapy (theranostics) of prostate carcinoma (PCa). The radiation doses for therapeutic application of such compounds are limited by substantial uptakes in kidneys and salivary glands, with excess doses reportedly leading to radiotoxicity-related adverse effects, such as kidney insufficiency or xenostomia. On the basis of the triazacyclononane-triphosphinate (TRAP) chelator, monomeric to trimeric conjugates of the PSMA inhibitor motif lysine-urea-glutamic acid (KuE) were synthesized by means of Cu(I)-mediated (CuAAC) or 5-aza-dibenzocyclooctyne (DBCO)-driven, strain-promoted click chemistry (SPAAC), which were labeled with gallium-68 for application in positron emission tomography (PET), and characterized in terms of PSMA affinity (determined in cellular displacement assays against I-125-BA) and lipophilicity (expressed as log D). Using subcutaneous murine LNCaP (PSMA-positive human prostate carcinoma) xenografts, the influence of ligand multiplicity, affinity, polarity, and molar activity (i.e., mass dose) on the uptakes in tumor, kidney, salivary, and background (muscle) was analyzed by means of region-of-interest (ROI) based quantification of small-animal PET imaging data. As expected, trimerization of the KuE motif resulted in high PSMA affinities (IC50 ranging from 6.0-1.5 nM). Of all parameters, molar activity/cold mass had the most pronounced influence on PET uptakes. Because accumulation in nontumor tissues was effected to a larger extent than tumor uptakes, lower molar activities resulted in substantially better tumor-to-organ ratios. For example, for one trimer, 68Ga-AhxKuE3 (IC50 = 1.5 ± 0.3 nM, log D = -3.8 ± 0.1), a higher overall amount of active compound (12 pmol vs 2 nmol, equivalent to molar activities of 1200 and 8 MBq/nmol) resulted in a remarkable reduction of the kidney-to-tumor ratio from 11.4 to 1.4, respectively, at 60 min p.i. Our study suggests that, for PSMA-targeting radiopharmaceuticals, molar activity has a more pronounced influence on small-animal PET imaging results than structural or in vitro parameters.

Persistent T cell unresponsiveness associated with chronic visceral leishmaniasis in HIV-coinfected patients.

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.

The impact of digital contact tracing on the SARS-CoV-2 pandemic-a comprehensive modelling study.

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 ( R 0 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.

Evaluation of C-reactive protein and myxovirus resistance protein A to guide the rational use of antibiotics among acute febrile adult patients in Northwest Ethiopia.

OBJECTIVES: In 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. METHODS: Adults 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. RESULTS: Of 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%. CONCLUSIONS: An 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.

Minimally Invasive Microbiopsies as an Improved Sampling Method for the Diagnosis of Cutaneous Leishmaniasis.

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.

Hepatitis C Virus and Human Cytomegalovirus-Natural Killer Cell Subsets in Persistent Viral Infections.

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.

Dendritic poly-chelator frameworks for multimeric bioconjugation.

Starting from multifunctional triazacyclononane-triphosphinate chelator cores, dendritic molecules with the ability to bind metal ions within their framework were synthesized. A cooperative interaction of the chelator cages resulted in a markedly increased affinity towards 67/68GaIII. A hexameric PSMA inhibitor conjugate with high affinity (IC50 = 1.2 nM) and favorable in vivo PET imaging properties demonstrated practical applicability. The novel scaffolds are useful for synthesis of structurally well-defined multimodal imaging probes or theranostics.

The proto-oncogene Myc drives expression of the NK cell-activating NKp30 ligand B7-H6 in tumor cells.

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.

IL-12-producing monocytes and HLA-E control HCMV-driven NKG2C+ NK cell expansion.

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.