Influenza A virus transcribes viral mRNAs from the eight segmented viral genome when it infects. The kinetics of viral transcription, nuclear export of viral transcripts, and their potential variation between the eight segments are poorly characterised. Here, we introduce a statistical framework for estimating the nuclear export rate of each segment from a snapshot of mRNA localisation.
View Article and Find Full Text PDFBackground: Vaccines in emergency use are efficacious against COVID-19, yet vaccine-induced prevention against nasal SARS-CoV-2 infection remains suboptimal.
Methods: Since mucosal immunity is critical for nasal prevention, we investigated the efficacy of an intramuscular PD1-based receptor-binding domain (RBD) DNA vaccine (PD1-RBD-DNA) and intranasal live attenuated influenza-based vaccines (LAIV-CA4-RBD and LAIV-HK68-RBD) against SARS-CoV-2.
Findings: Substantially higher systemic and mucosal immune responses, including bronchoalveolar lavage IgA/IgG and lung polyfunctional memory CD8 T cells, were induced by the heterologous PD1-RBD-DNA/LAIV-HK68-RBD as compared with other regimens.
We previously developed a temperature-sensitive, and NS1 gene deleted live attenuated influenza vaccine (DelNS1-LAIV) and demonstrated its potent protective efficacy in intranasally vaccinated mice. Here we investigated whether intradermal (i.d.
View Article and Find Full Text PDFThe development of a safe and effective vaccine against SARS-CoV-2, the causative agent of pandemic coronavirus disease-2019 (COVID-19), is a global priority. Here, we aim to develop novel SARS-CoV-2 vaccines based on a derivative of less commonly used rare adenovirus serotype AdC68 vector. Three vaccine candidates were constructed expressing either the full-length spike (AdC68-19S) or receptor-binding domain (RBD) with two different signal sequences (AdC68-19RBD and AdC68-19RBDs).
View Article and Find Full Text PDFHost adaptive mutations in the influenza A virus (IAV) PB2 protein are critical for human infection, but their molecular action is not well understood. We observe that when IAV containing avian PB2 infects mammalian cells, viral ribonucleoprotein (vRNP) aggregates that localize to the microtubule-organizing center (MTOC) are formed. These vRNP aggregates resemble LC3B-associated autophagosome structures, with aggresome-like properties, in that they cause the re-distribution of vimentin.
View Article and Find Full Text PDFThe ongoing pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is currently affecting millions of lives worldwide. Large retrospective studies indicate that an elevated level of inflammatory cytokines and pro-inflammatory factors are associated with both increased disease severity and mortality. Here, using multidimensional epigenetic, transcriptional, in vitro, and in vivo analyses, we report that topoisomerase 1 (TOP1) inhibition suppresses lethal inflammation induced by SARS-CoV-2.
View Article and Find Full Text PDFThe ongoing pandemic caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is currently affecting millions of lives worldwide. Large retrospective studies indicate that an elevated level of inflammatory cytokines and pro-inflammatory factors are associated with both increased disease severity and mortality. Here, using multidimensional epigenetic, transcriptional, and analyses, we report that Topoisomerase 1 (Top1) inhibition suppresses lethal inflammation induced by SARS-CoV-2.
View Article and Find Full Text PDFBackground: Clinical outcomes of the interaction between the co-circulating pandemic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and seasonal influenza viruses are unknown.
Methods: We established a golden Syrian hamster model coinfected by SARS-CoV-2 and mouse-adapted A(H1N1)pdm09 simultaneously or sequentially. The weight loss, clinical scores, histopathological changes, viral load and titer, and serum neutralizing antibody titer were compared with hamsters challenged by either virus.
Emerg Microbes Infect
December 2020
The emergence of SARS-CoV-2 has led to the current global coronavirus pandemic and more than one million infections since December 2019. The exact origin of SARS-CoV-2 remains elusive, but the presence of a distinct motif in the S1/S2 junction region suggests the possible acquisition of cleavage site(s) in the spike protein that promoted cross-species transmission. Through plaque purification of Vero-E6 cultured SARS-CoV-2, we found a series of variants which contain 15-30-bp deletions (Del-mut) or point mutations respectively at the S1/S2 junction.
View Article and Find Full Text PDFNonstructural protein 1 (NS1) of influenza virus is a key virulence element with multifunctional roles in virus replication and a potent antagonist of host immune response. Deletion of NS1 (DelNS1) would create a safer and more extensively immunogenic live attenuated influenza virus (LAIV) vaccine. However, DelNS1 viruses are very difficult to grow in regular vaccine-producing systems, which has hampered the application of DelNS1 LAIV vaccines in humans.
View Article and Find Full Text PDFSignificantly higher numbers of human infections with H5N1 virus have occurred in Indonesia and Egypt, compared with other affected areas, and it is speculated that there are specific viral factors for human infection with avian H5N1 viruses in these locations. We previously showed PB2-K526R is present in 80% of Indonesian H5N1 human isolates, which lack the more common PB2-E627K substitution. Testing the hypothesis that this mutation may prime avian H5N1 virus for human infection, we showed that: (1) K526R is rarely found in avian influenza viruses but was identified in H5N1 viruses 2⁻3 years after the virus emerged in Indonesia, coincident with the emergence of H5N1 human infections in Indonesia; (2) K526R is required for efficient replication of Indonesia H5N1 virus in mammalian cells in vitro and in vivo and reverse substitution to 526K in human isolates abolishes this ability; (3) Indonesian H5N1 virus, which contains K526R-PB2, is stable and does not further acquire E627K following replication in infected mice; and (4) virus containing K526R-PB2 shows no fitness deficit in avian species.
View Article and Find Full Text PDFHuman infection with highly pathogenic avian influenza A viruses causes severe disease and fatalities. We previously identified a potent and broadly neutralizing antibody (bnAb), 13D4, against the H5N1 virus. Here, we report the co-crystal structure of 13D4 in complex with the hemagglutinin (HA) of A/Vietnam/1194/2004 (H5N1).
View Article and Find Full Text PDFMicrobes Infect
December 2017
The non-structural protein (NS1) of influenza A viruses (IAV) performs multiple functions during viral infection. NS1 contains two nuclear localization signals (NLS): NLS1 and NLS2. The NS1 protein is located predominantly in the nucleus during the early stages of infection and subsequently exported to the cytoplasm.
View Article and Find Full Text PDFInfluenza virus utilizes host splicing machinery to process viral mRNAs expressed from both M and NS segments. Through genetic analysis and functional characterization, we here show that the NS segment of H7N9 virus contains a unique G540A substitution, located within a previously undefined exonic splicing enhancer (ESE) motif present in the NEP mRNA of influenza A viruses. G540A supports virus replication in mammalian cells while retaining replication ability in avian cells.
View Article and Find Full Text PDFWe report the complete genome sequence of influenza virus H9N2 associated with a fatal outbreak among chickens in Dubai. All segments are clustered with avian H9N2 viruses circulating in the Middle East but distinct from those in southeast Asia. It is not a reassortant virus or transmitted from other regions.
View Article and Find Full Text PDFThe continuous and sporadic human transmission of highly pathogenic avian H5N1 and H7N9 influenza viruses illustrates the urgent need for efficacious vaccines. However, all tested vaccines for the H5N1 and H7N9 viruses appear to be poorly immunogenic in mammals. In this study, a series of vaccines was produced using reverse genetic techniques that possess HA and NA genes from the H5N1 virus in the genetic background of the high-yield strain A/PR/8/34 (H1N1).
View Article and Find Full Text PDFA novel avian influenza virus H7N9 infection occurred among human populations since 2013. Although the lack of sustained human-to-human transmission limited the epidemics caused by H7N9, the late presentation of most patients and the emergence of neuraminidase-resistant strains made the development of novel antiviral strategy against H7N9 in urgent demands. In this study, we evaluated the potential of pamidronate, a pharmacological phosphoantigen that can specifically boost human Vδ2-T-cell, on treating H7N9 virus-infected humanized mice.
View Article and Find Full Text PDFUnlabelled: The NS1 protein of influenza virus has multiple functions and is a determinant of virulence. Influenza viruses with NS1 deletions (DelNS1 influenza viruses) are a useful tool for studying virus replication and can serve as effective live attenuated vaccines, but deletion of NS1 severely diminishes virus replication, hampering functional studies and vaccine production. We found that WSN-DelNS1 viruses passaged in cells consistently adapted to gain an A14U substitution in the 3' noncoding region of the M segment of viral RNA (vRNA) which restored replicative ability.
View Article and Find Full Text PDFHost-adaptive strategies, such as the E627K substitution in the PB2 protein, are critical for replication of avian influenza A viruses in mammalian hosts. Here we show that mutation PB2-K526R is present in some human H7N9 influenza isolates, in nearly 80% of H5N1 human isolates from Indonesia and, in conjunction with E627K, in almost all seasonal H3N2 viruses since 1970. Polymerase complexes containing PB2-526R derived from H7N9, H5N1 or H3N2 viruses exhibit increased polymerase activity.
View Article and Find Full Text PDFNF90 was shown to exhibit broad antiviral activity against several viruses, but detailed mechanisms remain unclear. In this study, we examined the molecular basis for the inhibitory effect of NF90 on virus replication mediated through protein kinase (PKR)-associated translational regulation. We first verified the interaction between NF90 and PKR in mammalian cells and showed that NF90 interacts with PKR through its C-terminal and that the interaction is independent of NF90 RNA-binding properties.
View Article and Find Full Text PDFObjective: Human infections caused by avian influenza virus A(H7N9) re-emerged in late 2013. We reported the first Hong Kong patient without risk factors for severe A(H7N9) disease.
Methods: Direct sequencing was performed on the endotracheal aspirate collected from a 36-year-old female with history of poultry contact.