The Human Cytomegalovirus Fc Receptor gp68 Binds the Fc CH2-CH3 Interface of Immunoglobulin G

Recognition of immunoglobulin G (IgG) by surface receptors for the Fc domain of immunoglobulin G (Fc{gamma}), Fc{gamma}Rs, can trigger both humoral and cellular immune responses. Two human cytomegalovirus (HCMV)-encoded type I transmembrane receptors with Fc{gamma}-binding properties (vFc{gamma}Rs), gp34 and gp68, have been identified on the surface of HCMV-infected cells and are assumed to confer protection against IgG-mediated immunity. Here we show that Fc{gamma} recognition by both vFc{gamma}Rs occurs independently of N-linked glycosylation of Fc{gamma}, in contrast with the properties of host Fc{gamma}Rs. To gain further insight into the interaction with Fc{gamma}, truncation mutants of the vFc{gamma}R gp68 ectodomain were probed for Fc{gamma} binding, resulting in localization of the Fc{gamma} binding site on gp68 to residues 71 to 289, a region including an immunoglobulin-like domain. Gel filtration and biosensor binding experiments revealed that, unlike host Fc{gamma}Rs but similar to the herpes simplex virus type 1 (HSV-1) Fc receptor gE-gI, gp68 binds to the CH2-CH3 interdomain interface of the Fc{gamma} dimer with a nanomolar affinity and a 2:1 stoichiometry. Unlike gE-gI, which binds Fc{gamma} at the slightly basic pH of the extracellular milieu but not at the acidic pH of endosomes, the gp68/Fc{gamma} complex is stable at pH values from 5.6 to pH 8.1. These data indicate that the mechanistic details of Fc binding by HCMV gp68 differ from those of host Fc{gamma}Rs and from that of HSV-1 gE-gI, suggesting distinct functional and recognition properties

Einsatz geeigneter Desinfektionsmitteln bei gentechnisch veränderten Viren und viralen Vektoren – Stellungnahme der Kommission für Virusdesinfektion der Deutschen Vereinigung zur Bekämpfung der Viruskrankheiten (DVV) e. V. und der Gesellschaft für Virologie (GfV) e. V.

Im Epidemiologischen Bulletin 36/2020 haben Mitglieder der Kommission für Virusdesinfektion der DVV/GfV eine Übersicht häufig verwendeter gentechnisch veränderter Organismen zusammengestellt, davon ausgehend werden Aspekte der Auswahl und Anwendung von Desinfektionsmitteln näher erörtert. Dabei wurden neben Vertretern von Bundesoberbehörden, wie des FLI, des PEI und des RKI, auch Vertreter des ÖGD und virologischer Institute aus Universitäten einbezogen.Peer Reviewe

Human Cytomegalovirus Disrupts the Major Histocompatibility Complex Class I Peptide-Loading Complex and Inhibits Tapasin Gene Transcription ▿

Major histocompatibility complex class I (MHC I) molecules present antigenic peptides for CD8+ T-cell recognition. Prior to cell surface expression, proper MHC I loading is conducted by the peptide-loading complex (PLC), composed of the MHC I heavy chain (HC) and β2-microglobulin (β2m), the peptide transporter TAP, and several chaperones, including tapasin. Tapasin connects peptide-receptive MHC I molecules to the PLC, thereby facilitating loading of high-affinity peptides onto MHC I. To cope with CD8+ T-cell responses, human cytomegalovirus (HCMV) encodes several posttranslational strategies inhibiting peptide transport and MHC I biogenesis which have been studied extensively in transfected cells. Here we analyzed assembly of the PLC in naturally HCMV-infected fibroblasts throughout the protracted replication cycle. MHC I incorporation into the PLC was absent early in HCMV infection. Subsequently, tapasin neosynthesis became strongly reduced, while tapasin steady-state levels diminished only slowly in infected cells, revealing a blocked synthesis rather than degradation. Tapasin mRNA levels were continuously downregulated during infection, while tapasin transcripts remained stable and long-lived. Taking advantage of a novel method by which de novo transcribed RNA is selectively labeled and analyzed, an immediate decline of tapasin transcription was seen, followed by downregulation of TAP2 and TAP1 gene expression. However, upon forced expression of tapasin in HCMV-infected cells, repair of MHC I incorporation into the PLC was relatively inefficient, suggesting an additional level of HCMV interference. The data presented here document a two-pronged coordinated attack on tapasin function by HCMV