29 research outputs found
Corneal Replication Is an Interferon Response-Independent Bottleneck for Virulence of Herpes Simplex Virus 1 in the Absence of Virion Host Shutoff
Herpes simplex viruses lacking the virion host shutoff function (Îvhs) are avirulent and hypersensitive to type I and type II interferon (IFN). In this study, we demonstrate that even in the absence of IFN responses in AG129 (IFN-αÎČÎłRâ/â) mice, Îvhs remains highly attenuated via corneal infection but is fully virulent via intracranial infection. The data demonstrate that the interferon-independent inherent replication defect of Îvhs has a significant impact upon peripheral replication and neuroinvasion
MERS-CoV 4b protein interferes with the NF-ÎșB-dependent innate immune response during infection
This work is licensed under a Creative Commons Attribution 4.0 International License.Middle East respiratory syndrome coronavirus (MERS-CoV) is a novel human coronavirus that emerged in 2012, causing severe pneumonia and acute respiratory distress syndrome (ARDS), with a case fatality rate of ~36%. When expressed in isolation, CoV accessory proteins have been shown to interfere with innate antiviral signaling pathways. However, there is limited information on the specific contribution of MERS-CoV accessory protein 4b to the repression of the innate antiviral response in the context of infection. We found that MERS-CoV 4b was required to prevent a robust NF-ÎșB dependent response during infection. In wild-type virus infected cells, 4b localized to the nucleus, while NF-ÎșB was retained in the cytoplasm. In contrast, in the absence of 4b or in the presence of cytoplasmic 4b mutants lacking a nuclear localization signal (NLS), NF-ÎșB was translocated to the nucleus leading to the expression of pro-inflammatory cytokines. This indicates that NF-ÎșB repression required the nuclear import of 4b mediated by a specific NLS. Interestingly, we also found that both in isolation and during infection, 4b interacted with α-karyopherin proteins in an NLS-dependent manner. In particular, 4b had a strong preference for binding karyopherin-α4 (KPNA4), which is known to translocate the NF-ÎșB protein complex into the nucleus. Binding of 4b to KPNA4 during infection inhibited its interaction with NF-ÎșB-p65 subunit. Thereby we propose a model where 4b outcompetes NF-ÎșB for KPNA4 binding and translocation into the nucleus as a mechanism of interference with the NF-ÎșB-mediated innate immune response
Corneal Replication Is an Interferon Response-Independent Bottleneck for Virulence of Herpes Simplex Virus 1 in the Absence of Virion Host Shutoff
Evolutionary study of COVIDâ19, severe acute respiratory syndrome coronavirus 2 (SARSâCoVâ2) as an emerging coronavirus: Phylogenetic analysis and literature review
Identification of promising drug candidates against NSP16 of SARS-CoV-2 through computational drug repurposing study
Reverse genetics with a full-length infectious cDNA of the Middle East respiratory syndrome coronavirus
Severe acute respiratory syndrome with high mortality rates (âŒ50%) is associated with a novel group 2c betacoronavirus designated Middle East respiratory syndrome coronavirus (MERS-CoV). We synthesized a panel of contiguous cDNAs that spanned the entire genome. Following contig assembly into genome-length cDNA, transfected full-length transcripts recovered several recombinant viruses (rMERS-CoV) that contained the expected marker mutations inserted into the component clones. Because the wild-type MERS-CoV contains a tissue culture-adapted T1015N mutation in the S glycoprotein, rMERS-CoV replicated âŒ0.5 log less efficiently than wild-type virus. In addition, we ablated expression of the accessory protein ORF5 (rMERSâąORF5) and replaced it with tomato red fluorescent protein (rMERS-RFP) or deleted the entire ORF3, 4, and 5 accessory cluster (rMERS-ÎORF3â5). Recombinant rMERS-CoV, rMERS-CoVâąORF5, and MERS-CoV-RFP replicated to high titers, whereas MERS-ÎORF3â5 showed 1â1.5 logs reduced titer compared with rMERS-CoV. Northern blot analyses confirmed the associated molecular changes in the recombinant viruses, and sequence analysis demonstrated that RFP was expressed from the appropriate consensus sequence AACGAA. We further show dipeptidyl peptidase 4 expression, MERS-CoV replication, and RNA and protein synthesis in human airway epithelial cell cultures, primary lung fibroblasts, primary lung microvascular endothelial cells, and primary alveolar type II pneumocytes, demonstrating a much broader tissue tropism than severe acute respiratory syndrome coronavirus. The availability of a MERS-CoV molecular clone, as well as recombinant viruses expressing indicator proteins, will allow for high-throughput testing of therapeutic compounds and provide a genetic platform for studying gene function and the rational design of live virus vaccines
Further Evidence for Bats as the Evolutionary Source of Middle East Respiratory Syndrome Coronavirus
The evolutionary origins of Middle East respiratory syndrome (MERS) coronavirus (MERS-CoV) are unknown. Current evidence suggests that insectivorous bats are likely to be the original source, as several 2c CoVs have been described from various species in the family Vespertilionidae. Here, we describe a MERS-like CoV identified from a Pipistrellus cf. hesperidus bat sampled in Uganda (strain PREDICT/PDF-2180), further supporting the hypothesis that bats are the evolutionary source of MERS-CoV. Phylogenetic analysis showed that PREDICT/PDF-2180 is closely related to MERS-CoV across much of its genome, consistent with a common ancestry; however, the spike protein was highly divergent (46% amino acid identity), suggesting that the two viruses may have different receptor binding properties. Indeed, several amino acid substitutions were identified in key binding residues that were predicted to block PREDICT/PDF-2180 from attaching to the MERS-CoV DPP4 receptor. To experimentally test this hypothesis, an infectious MERS-CoV clone expressing the PREDICT/PDF-2180 spike protein was generated. Recombinant viruses derived from the clone were replication competent but unable to spread and establish new infections in Vero cells or primary human airway epithelial cells. Our findings suggest that PREDICT/PDF-2180 is unlikely to pose a zoonotic threat. Recombination in the S1 subunit of the spike gene was identified as the primary mechanism driving variation in the spike phenotype and was likely one of the critical steps in the evolution and emergence of MERS-CoV in humans