1,721,106 research outputs found
Murine cytomegalovirus degrades MHC class II to colonize the salivary glands
No full textCytomegaloviruses (CMVs) persistently and systemically infect the myeloid cells of immunocompetent hosts. Persistence implies immune evasion, and CMVs evade CD8+ T cells by inhibiting MHC class I-restricted antigen presentation. Myeloid cells can also interact with CD4+ T cells via MHC class II (MHC II). Human CMV (HCMV) attacks the MHC II presentation pathway in vitro, but what role this evasion might play in host colonization is unknown. We show that Murine CMV (MCMV) down-regulates MHC II via M78, a multi-membrane spanning viral protein that captured MHC II from the cell surface and was necessary although not sufficient for its degradation in low pH endosomes. M78-deficient MCMV down-regulated MHC I but not MHC II. After intranasal inoculation, it showed a severe defect in salivary gland colonization that was associated with increased MHC II expression on infected cells, and was significantly rescued by CD4+ T cell loss. Therefore MCMV requires CD4+ T cell evasion by M78 to colonize the salivary glands, its main site of long-term shedding.</div
Die diagnostische Testgenauigkeit von RT-qPCR im Hinblick auf die SARS-CoV-2-Infektiosität: ein systematischer Review mit Meta-Analyse
No full textHintergrund: Die empfindlichste Methodik zum Nachweis von SARS-CoV-2 basiert auf der Reverse-Transkriptase-Polymerase-Kettenreaktion (RT-qPCR) der viralen RNA. Der Nachweis von RNA bedeutet jedoch nicht zwangsläufig das Vorhandensein eines infektiösen Virus. Wohingegen die Virusisolierung aus Zellkulturen als das Surrogat der Infektiosität angesehen wird.Forschungsziele: Die Forschungsfrage dieser Arbeit lautet wie folgt: Was ist die diagnostische Testgenauigkeit von RT-qPCR im Hinblick auf den Nachweis von infektiösem SARS-CoV-2 im Atemwegsmaterial? Folgende Ziele wurden hierbei verfolgt: 1. Bestimmung der Testgenauigkeit der RT-qPCR im Vergleich zur Zellkultur, 2. Schätzung des positiv prädiktiven Wertes (PPV) der Virusisolation aus RT-qPCR positiven Proben, 3. Schätzung der Virusanzuchtwahrscheinlichkeiten in Abhängigkeit von Cycle Threshold (Ct)-Werten oder log10-Genomkopien/ml.Registrierung und Funding: Der Review wurde über PROSPERO (CRD42021239149) registriert. Das Funding erfolgte über das Bundesministerium für Bildung und Forschung (FKZ: 01KX2021).Methoden: Es wurden drei elektronische Datenbanken nach Studien durchsucht, in denen Atemwegsproben mit RT-qPCR und Zellkultur untersucht wurden. Die Bewertung der Studienqualität erfolgte mittels des Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) Instruments. Der PPV-Gesamtschätzer wurde durch das Random-Effects Modell berechnet. Virusanzuchtwahrscheinlichkeiten wurden mittels logistischer Regressionen analysiert.Ergebnisse: Durch die Datenbankensuche wurden 8939 Treffer identifiziert und 55 Studien in diese Übersichtsarbeit eingeschlossen. Diese Studien lieferten Informationen zu 10‘423 Atemwegsproben. Beim überwiegenden Anteil der Studien handelte es sich um Beobachtungsstudien (n=31, 56,4%). Das Biasrisiko wurde in den meisten Studien als hoch eingestuft, außer in neun Studien, wo das Risiko unklar war. Sieben Studien wurden für die Testgenauigkeitsschätzung einbezogen. Die Sensitivität lag bei 100% und die Spezifität variierte zwischen 29 % und 92 %. Fünfundfünfzig Studien wurden in die PPV-Meta-Analyse einbezogen. PPV variierte in Abhängigkeit von der Subgruppierung nach Samplingzeiten. Es lag ein PPV von 1% (95 % Konfidenzintervall (CI), 0-7 %) bei Probenahme nach10 Tagen und 27% (CI, 19-36 %) bis 46% (CI, 33-60 %) in Subgruppen mit früheren Probenahmenzeiten. Die Heterogenität war substanziell (Prädiktionsintervall: 5-86 %). Zwölf Studien berichteten Daten, die eine Schätzung der Virusanzuchtwahrscheinlichkeit erlaubten. Die Schätzer der Virusanzuchtwahrscheinlichkeit schwankten zwischen 0 % (CI, 0-22 %) und 63 % (CI, 0-100 %).Schlussfolgerung: In dieser Arbeit wurde ein hohes Maß an Heterogenität und ein Mangel an Standardisierung, insbesondere bei der Zellkulturmethodologie, festgestellt. Darüber hinaus zeigte sich eine Evidenzlücke von gut konzipierten Testgütestudien. Solche Studien könnten wichtige Informationen und eine Einschätzungsgrundlage des Übertragungsrisikos liefern und hierdurch das künftige Management von Pandemien beeinflussen
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The placental transport of HCMV - implications for congenital infection by neonatal Fc receptor
No full textHuman Cytomegalovirus (HCMV) is a pervasive pathogen with significant implications for neonatal health, particularly due to its potential for mother-to-fetus (mother-to-embryo) transmission during pregnancy. Despite ongoing research efforts, effective pharmaceutical interventions or vaccines to prevent this mode of transmission remain elusive. Congenitally infected infants often suffer varying degrees of disabilities, with deafness being the most common consequence, posing a substantial risk to newborn health. This dissertation explores the mechanisms underlying the placental transport of HCMV, focusing on the implications of neonatal Fc receptor (FcRn) mediated congenital infection. The study aimed to develop a stable in vitro model of the maternal-fetal interface, emphasizing the roles of viral Fcγ receptors (vFcγRs) in mediating HCMV's linkage to FcRn, and to elucidate the active transport processes and mechanisms of HCMV across the fetal syncytiotrophoblast (STB). In pursuit of these objectives, we evaluated various existing maternal-fetal cell-based in vitro models, ultimately establishing a Transwell® (TW) assay that forms a stable single cell layer, mimicking trophoblast cells' unique characteristics. Through lentivirus transduction technology, the monocytic layer was engineered to express the HA-FCGRT gene, enhancing its interaction with IgG. This assay facilitated quantitative analysis of IgG transcytosis across human STB, highlighting FcRn's pivotal role as the primary transcytosis receptor in our experimental setup. We found that BeWo cells, among various cell types transduced with the FCGRT gene, were most suitable for the TW assay. Optimal antibody concentrations were determined through titration, refining the TW assay's applicability to a broader range of cells, viruses, and antibodies, and laying groundwork for subsequent experiments. Our findings revealed that HCMV, aided by IgG, could efficiently traverse the TW assay's single-cell layer, while viruses lacking the two vFcγRs demonstrated significantly hindered passage. Furthermore, in viral infectivity assays, we observed that Cytotect®, an anti-HCMV Hyperimmune Globulin (HIG), could neutralize HCMV's virulence, impeding its ability to reinfect other epidermal cells. Conversely, antagonizing both vFcγRs substantially reduced HCMV's transcytosis capability, underscoring the importance of vFcγRs' interaction with IgG in manipulating FcRn to facilitate viral spread. The study's findings pave the way for future therapeutic strategies targeting HCMV's hijacking mechanism of FcRn, potentially leading to the development of novel, effective pharmaceuticals or vaccines to prevent HCMV's mother-to-fetus transmission. This research not only contributes to a deeper understanding of HCMV's transplacental transport mechanisms but also opens avenues for mitigating the risks associated with congenital HCMV infection
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Struktur-Funktions-Beziehung der HCMV-kodierten Fcgamma-Rezeptoren gp34 und gp68
No full textNeutralisierende Antikörper sind entscheidend in der Eindämmung der Virusinfektion, indem sie den Eintritt in die Wirtszelle hemmen bzw. die Aktivierung der Komplementkaskade initiieren. Distinkte wirtseigene Oberflächenrezeptoren für die Fc-Domäne von IgG (FcyR) sind für die Kommunikation von humoraler und zellulärer Immunantwort verantwortlich. Auch Mitglieder der Herpesviren kodieren für Fc-bindende Proteine, die Kandidaten für immunevasive Funktionen darstellen könnten. Der Nachweis der HCMV-kodierten Fc-bindenden Proteine gp34 und gp68 als Bestandteil der Virushülle lies auf eine immunevasive Funktion hinsichtlich neutralisierendem IgG und Komplement-vermittelter Virolyse schließen, wie für den HSV-1-kodierten FcyR gE beschrieben. Weder für gp34 noch für gp68 konnte in vitro ein hemmender Effekt auf Neutralisation und Virolyse beobachtet werden. In unserem Labor wurde jedoch gezeigt, dass gp34 und gp68 selektiv die IgG-abhängige Aktivierung zellulärer FcyR inhibieren. Die glykosylierungsunabhängige Ligandenbindung von gp34 und gp68 wies auf unterschiedliche Interaktionsmechanismen zwischen den zellulären und den viralen FcyR hin. Mithilfe eines mutierten Fc-Fragments konnte für gp68 eindeutig eine mit HSV-1 gE überlappende Bindestelle an IgG identifiziert werden. Die für die Ligandenbindung erforderlichen Aminosäuren 71-292 von gp68 binden Fc in einer 2:1 Stöchiometrie, wobei die N-, nicht aber die O-Glykosylierung des vFcyRs essentiell sind. Darüber hinaus formt gp34 auf infizierten Zellen und auf der Virushülle kovalente Homooligomere. gp34-Cysteinpunktmutanten auf Basis der für die Bindung notwendigen Aminosäuren 24-140 lassen vermuten, dass die Oligomerisierung Voraussetzung für die Fc-Bindung ist. Im Gegensatz zu gp68 scheint der Mechanismus der Fc-Bindung von gp34 einzigartig unter den bekannten Fcy-Rezeptoren zu sein. Diese Ergebnisse lassen vermuten, dass trotz redundanter Expression der HCMV-FcyR der Bindungs- und Wirkungsmechanismus selektiv ist.Neutralizing IgGs play a key role in diminishing virus infectivity by inhibiting the entry into host cells. Additionally, IgG-bound particles may be inactivated by virolysis through the activation of complement. Surface receptors specific for the Fc domain of IgG represent host proteins, connecting humoral and cellular immune responses. Also members of the herpes virus family code for proteins with Fc binding properties, implying functions that could intervene with antibody-dependent effector mechanisms. The presence of gp34 and gp68 on the virion membrane raised the question whether they are able to inhibit neutralising IgG and complement-mediated virolysis. The HSV-1-encoded FcyR gE was described to affect neutralisation and virolysis. Despite extensive analysis, there were no implications found that gp34 or gp68 interfere with neutralising IgG or virolysis in vitro. However, our lab could demonstrate that gp34 and gp68 selectively inhibit the IgG-dependent activation of the different host FcyRs. In contrast to the cFcyRs Fc recognition by gp34 and gp68 occurs independently of N-linked glycosylation of IgG, which points to a different binding mechanism among host and viral FcyRs. By taking advantage of a mutated Fc fragment, overlapping binding regions of the HSV-1 gE and gp68 were identified. For gp68 the amino acids 71-292 including the N-glycans are strictly required for Fc binding in a 2:1 stoichiometry. Interestingly, gp34 forms covalently linked homo-oligomers in infected cells and on the virion. Based on the minimal binding domain comprising the amino acids 24-140 of gp34, targeted cysteine exchange mutants revealed that oligomer formation by gp34 is absolutely required for Fc binding. In contrast to gp68, the Fc binding characteristics of gp34 appears to be unique among the known FcyRs. These findings allow us to postulate that even if the HCMV-encoded FcyRs are redundantly expressed the mechanistic details and binding properties are selective
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Human cytomegalovirus restricts adaptive NK cell expansion and function by deploying IgG-Fc binding glycoproteins gp34 and gp68
No full textHuman cytomegalovirus (HCMV) infection is associated with the emergence of a unique subset of highly antiviral natural killer (NK) cells, commonly referred to as adaptive NK cells (aNK), which are characterized by the expression of the activating NKG2C receptor. As part of their adaptive phenotype, aNK are capable of expanding and contracting in response to viral infections. Interestingly, and consistent with their increased potential for antibody-dependent cellular cytolysis (ADCC), IgG antibody-mediated activation of the Fc gamma receptor (FcγR) CD16 is sufficient to promote aNK expansion. Conversely, previous data show that genetic deletion of CD16 in humans precludes the emergence of aNK in HCMV-seropositive individuals. We have previously shown that HCMV expresses viral Fcγ receptors (vFcγRs) that block HCMV-specific IgG to activate host CD16. We therefore hypothesize that HCMV, while inducing the emergence of aNK, deploys vFcγRs to limit the expansion of aNK. In support of this hypothesis, in a cohort analysis we found a correlation between the CD16 activation potential by HCMV-specific IgG and the number of aNK, which we did not find with EBV-specific IgG or CD64 activation by HCMV-specific IgG. In vitro expansion experiments performed by co-culturing PBMCs with opsonized HCMV virions show that HCMV-specific IgG is sufficient to drive aNK expansion and that genetic deletion of vFcγRs further enhances aNK expansion. Conversely, blocking CD16 leads to abrogation of aNK expansion. Finally, we found that IgG-mediated aNK expansion fundamentally alters the composition of the NK cell compartment with respect to receptor expression, specifically leading to a dominant NGK2C+/CD16+ subpopulation. This results in a stronger HCMV-specific ADCC response by aNK expanded in the absence of HCMV vFcγRs. Our data show that HCMV-encoded vFcγRs limit aNK expansion and effector responses through CD16 antagonization. This furthers our understanding of HCMV persistence in the presence of an antiviral humoral response
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