Cryo-EM structure of Influenza A virus NS1 and antiviral protein kinase PKR complex

Influenza A virus is the cause of a widespread human disease with high morbidity and mortality rates. The influenza virus encodes non-structural protein 1 (NS1), an exceedingly multifunctional virulence component. NS1 plays essential roles in viral replication and evasion of the cellular innate immune system. Protein kinase RNA-activated also known as protein kinase R (PKR) phosphorylates translation initiation factor eIF-2α on serine 51 to inhibit protein synthesis in virus-infected mammalian cells. Consequently, PKR activation inhibits mRNA translation, which results in the assert of both viral protein synthesis and cellular and possibly apoptosis in response to virus infection. Host signaling pathways are important in the replication of influenza virus, but the mechanisms involved remain to be characterized. Herein, the structure of NS1 and PKR complex was determined using Cryo-EM. We found the N91, E94, and G95 residues of PKR bind directly with N188, D125, and K126, respectively, of NS1. Furthermore, the study shows that PKR peptide offers a potential treatment for Influenza A virus infections.

Rosmarinic acid interferes with influenza virus A entry and replication by decreasing GSK3β and phosphorylated AKT expression levels

BACKGROUND

The purpose of this study was to examine the in vivo activity of rosmarinic acid (RA) - a phytochemical with antioxidant, anti-inflammatory, and antiviral properties - against influenza virus (IAV). An antibody-based kinase array and different in vitro functional assays were also applied to identify the mechanistic underpinnings by which RA may exert its anti-IAV activity.

METHODS

We initially examined the potential efficacy of RA using an in vivo mouse model. A time-of-addition assay and an antibody-based kinase array were subsequently applied to investigate mechanism-of-action targets for RA. The hemagglutination inhibition assay, neuraminidase inhibition assay, and cellular entry assay were also performed.

RESULTS

RA increased survival and prevented body weight loss in IAV-infected mice. In vitro experiments revealed that RA inhibited different IAV viruses - including oseltamivir-resistant strains. From a mechanistic point of view, RA downregulated the GSK3β and Akt signaling pathways - which are known to facilitate IAV entry and replication into host cells.

CONCLUSIONS

RA has promising preclinical efficacy against IAV, primarily by interfering with the GSK3β and Akt signaling pathways.

In Vitro Inactivation of Respiratory Viruses and Rotavirus by the Oral Probiotic Strain Weissella cibaria CMS1

Weissella cibaria CMS1 (oraCMS1) has been commercially used in Korea as an oral care probiotic for several years. Human respiratory syncytial virus (RSV) and the influenza A virus (H1N1) are representative viruses that cause infantile lower respiratory tract infections. Rotavirus A (RVA) is the most common cause of diarrhea in infants and young children. Here, we aimed to evaluate the efficacy of the cell-free supernatant (CFS) of oraCMS1 in inactivating RSV, H1N1, and RVA in suspension as per ASTM (American Society for Testing and Materials) E1052-20. The mixture of oraCMS1 and these viruses was evaluated at contact times of 1, 2, and 4 h. Virucidal activity was measured using a 50% tissue culture infective dose assay (log₁₀TCID₅₀) after infecting the host cells with the viruses. The CFS of oraCMS1 inactivated RSV by up to 99.0% after 1 h and 99.9% after 2 and 4 h, and H1N1 and RVA were inactivated by up to 99.9% and 99.0% at 2 h, respectively. Although these in vitro results cannot be directly interpreted as implying clinical efficacy, our findings suggest that oraCMS1 provides a protective barrier against RSV, H1N1, and RVA, and therefore, it can help decrease the risk of respiratory tract and intestinal infections.

Carvacrol inhibits the excessive immune response induced by influenza virus A via suppressing viral replication and TLR/RLR pattern recognition

ETHNOPHARMACOLOGICAL RELEVANCE

Carvacrol, a monoterpene phenol from Mosla chinensis Maxim, which is a commonly Chinese herbal medicine. The most important pharmacology of it is dispelling exogenous evils by increasing perspiration. And it is the gentleman medicine in the Chinese herbal compound prescription of Xin-Jia-Xiang-Ru-Yin, mainly for the treatment of summer colds with dampness including influenza virus A infection.

AIM OF THE STUDY

Our preliminary study verified that the Xin-Jia-Xiang-Ru-Yin could inhibit acute lung injury of mice with influenza virus A infection. And there have been some reports implicating the high antimicrobial activity of carvacrol for a wide range of product preservation, but little research including the effects of it on viral infection. The aim of this study was to reveal the antiviral effects of carvacrol, the main constituent in Mosla chinensis Maxim.

MATERIALS AND METHODS

Initially, C57BL/6 mice were grouped and intranasally administered FM1 virus to construct viral infection models. After treatment with ribavirin and carvacrol for 5 days, all mice were euthanized, and specimens were immediately obtained. Histology, flow cytometry and Meso Scale Discovery (MSD) analysis were used to analyze pathological changes in lung tissue, the expression levels of cytokines and the differentiation and proportion of CD4+ T cells subsets, while Western blot and qRT-PCR were used to detect the expression of related proteins and mRNA.

RESULTS

Carvacrol attenuated lung tissue damage, the proportions of Th1, Th2, Th17 and Treg in CD4+ T cells and the relative proportions of Th1/Th2 and Th17/Treg cells. Carvacrol inhibited the expression of inflammation-associated cytokines including IFN-γ, IL-2, IL-4, IL-5, IL-12 and TNF-ɑ, IL-1, IL-10, IL-6. Decreased levels of TLR7, MyD88, IRAK4, TRAK6, NF-κB, RIG-I, IPS-I and IRF mRNA in carvacrol-treated mice were observed comparing to the mice in VC group. Further, the total expression of RIG-I, MyD88 and NF-κB proteins had increased significantly in the VC group but reduced obviously in the group treated with ribavirin or carvacrol.

CONCLUSIONS

These results indicate that carvacrol is a potential alternative treatment for the excessive immune response induced by influenza virus A infection, the cold-fighting effect of Mosla chinensis Maxim may depend on the anti-virus of carvacrol.

Electrostatic wipes as simple and reliable methods for influenza virus airborne detection

The performance of an in-house protocol for virus detection on commercialized electrostatic wipes (EWs) was assessed experimentally by impregnating them with suspensions of cytomegalovirus, adenovirus, and influenza virus, and by determining the recovery efficiency, repeatability, and detection limit of the protocol. The protocol was sensitive enough to detect 4 log₁₀ gene copies of virus. At room temperature, influenza RNA was stable on EWs for at least four days. When EWs were placed high in 32 influenza-infected patients' rooms, influenza RNA was detectable in 75% (N = 24) of EWs, suggesting that EWs are simple and reliable methods for influenza virus airborne detection.

A retrospective observational study of the treatment of a nosocomial infection caused by oseltamivir-resistant influenza virus A with baloxavir marboxil

BACKGROUND

Nosocomial (hospital-acquired) influenza A virus infection is a very important clinical issue. The objective of this study is to describe the effect of baloxavir marboxil in controlling an outbreak of this infection.

METHODS

A retrospective observational study was performed to assess the effectiveness of baloxavir marboxil in the treatment of nosocomial infections caused by oseltamivir-resistant influenza virus A.

RESULTS

In September 2019, there was an outbreak of nosocomial influenza A(H1N1)pdm09 viral infection in one out of three facility wards for inpatients at the Okinawa Nanbu Regional Center for Children with Special Needs. Symptomatic staff members were kept off duty until they remained afebrile for 2 days. Prophylactic oseltamivir was administered to inpatients (n = 37) and to staff members (n = 16) who voluntarily requested the drug. However, both inpatients and staff members showed influenza A infection during prophylactic use of oseltamivir. The A(H1N1)pdm09 virus sample obtained from one patient was shown to be oseltamivir-resistant. After administration of baloxavir marboxil, the nosocomial outbreak gradually ceased. Moreover, the time (hours) to alleviation of fever in the oseltamivir group (n = 11) and baloxavir marboxil group (n = 13) was significantly different (p = 0.0034).

CONCLUSION

Our report provides evidence for the usefulness of baloxavir marboxil in treating influenza A patients who have received prophylactic doses of oseltamivir. This is the first report describing the successful use of baloxavir marboxil for of a nosocomial outbreak caused by oseltamivir-resistant influenza A virus.

Implementation of the cobas Liat influenza point-of-care test into an emergency department during a high-incidence season: a retrospective evaluation following real-world implementation

The cobas Liat influenza A/B and respiratory syncytial virus (RSV) assay (Liat) was used in the adult emergency department of a large London hospital from 21^st January 2018 to 14^th April 2018. Influenza was detected in 308 of 1027 (30%) samples tested; influenza A in 157 (15.3%), influenza B in 149 (14.5%) and RSV in 28 (2.7%). When compared against Fast Track Diagnostics Respiratory Pathogens 21 multiplex polymerase chain reaction and Cepheid Xpert Xpress Flu/RSV assay, Liat performance for the detection of influenza A or B was: sensitivity 85% [95% confidence interval (CI) 76–92)], specificity 98% (95% CI 97–99), negative predictive value 94% (95% CI 92–96) and positive predictive value 95% (95% CI 91–97).

Implementation of influenza point-of-care testing and patient cohorting during a high-incidence season: a retrospective analysis of impact on infection prevention and control and clinical outcomes

BACKGROUND

During high-incidence influenza seasons, a robust infection prevention and control policy is imperative to reduce nosocomial transmission of influenza.

AIM

To assess the impact of influenza point-of-care testing (POCT) in an emergency department (ED) and patient cohorting on an influenza ward on infection prevention and control and clinical outcomes.

METHODS

Influenza POCT was operational in the study ED from 21^st January 2018 and patient cohorting was operational on an influenza ward from 25^th January 2018. A retrospective 'before-after' analysis was performed with pre-intervention defined as 1^st November 2017 to 20^th January 2018 and post-intervention defined as 21^st January 2018 to 30^th April 2018. The primary outcome was the rate of hospital-acquired influenza. Secondary outcomes included antiviral prescription and length of stay. The length of time that inpatients remained influenza-positive was estimated by polymerase chain reaction (PCR).

FINDINGS

There were 654 inpatients with confirmed influenza during the 2017/18 influenza season: 223 pre- and 431 post-intervention. Post-intervention, there were fewer cases of hospital-acquired influenza per day (0.66 vs 0.95, P < 0.0001), median length of stay was shorter (5.5 vs 7.5 days, P = 0.005) and antiviral prescription was more frequent (80% vs 64.1%, P < 0.0001). Cohorting released 779 single rooms for use elsewhere in the trust. The fixed probability of being PCR-negative by the next day (P) was 0.14 [95% confidence interval (CI) 0.12-0.16] for immunocompetent patients. This implies that half of immunocompetent patients are PCR-negative by five days post-diagnosis (95% CI 5-6).

CONCLUSION

Influenza POCT in an ED and patient cohorting on an influenza ward were associated with reduced nosocomial transmission of influenza and improved patient flow. A policy of retesting immunocompetent patients five days post-diagnosis could allow half of these patients to come out of respiratory isolation earlier.

Identification of Etiologic Agents of the Pertussis-like Syndrome in Children by Real-time PCR Method

The aim of this study was to recognize the identity and frequency of etiologic agents of the pertussis-like syndrome in children &lt; 2 years of age. A cross-sectional hospital-based study conducted from August 2014 to August 2015. All children &lt; 2 years of age (n=100) who were suspected as pertussis infected were enrolled in this study and tested for Bordetella pertussis, adenovirus (Adv), respiratory syncytial virus (RSV), human metapneumovirus (hMPV), and influenza virus A (INF-A) by real-time PCR technique. RSV was the most detected pathogen (20%), followed by B. pertussis (18%), Adv (16%), INF-A (11%), and hMPV (10%). Co-infection was observed in 8 patients (11%) and the combinations of RSV/INF-A (n=3, 4%), and AdV/B. pertussis (n=3, 4%) were more frequent. RSV, B. pertussis, and hMPV were more frequent pathogens among infants &lt; 4 months of age. However, Adv and INF-A were more frequent pathogens among children &gt; 6 months of age. In this study, RSV was the most frequent identified pathogen (n=20, 20%), followed by B. pertussis (n=18, 18%) and AdV (n=16, 16%). Pertussis was more frequent in spring (8%) and summer (6%). In addition, clinical symptoms of pertussis were the same as some viral pathogens, which can lead to misdiagnosis of infection. Therefore, diagnosis of pertussis should be established on the bases of both the clinical symptoms and the laboratory methods.

Impact of a multiplex PCR point-of-care test for influenza A/B and respiratory syncytial virus on an acute pediatric hospital ward

Patients with respiratory infections are often managed presumptively until confirmation of infection status. We assessed the impact of introducing the Enigma® MiniLab™ FluAB-RSV point-of-care test (POCT) on patients admitted with a suspected respiratory virus driven illness in an acute pediatric ward. This utilized a before and after design (respiratory viral seasons 2013/14 versus 2014/15). Following POCT implementation, oseltamivir prescribing increased in patients with influenza (OR = 12.7, P = 0.05, 95% CI [1.0, 153.8]). A reduction in the average reimbursement charges without a change in the length of stay was observed. Modeling suggested that laboratory test cost savings could be achieved if the POCT cost £30 and was used for screening, followed by the respiratory viral panel for RSV and influenza negative patients. A rapid POCT for influenza A/B and RSV infections in pediatric inpatients may improve oseltamivir prescribing, strengthen antimicrobial stewardship, reduce reimbursement charges and decrease laboratory costs.

Selection of predicted siRNA as potential antiviral therapeutic agent against influenza virus

Influenza virus A (IVA) infection is responsible for recent death worldwide. Hence, there is a need to develop therapeutic agents against the virus. We describe the prediction of short interfering RNA (siRNA) as potential therapeutic molecules for the HA (Haemagglutinin) and NA (Neuraminidase) genes. We screened 90,522 siRNA candidates for HA and 13,576 for NA and selected 1006 and 1307 candidates for HA and NA, respectively based on the proportion of viral sequences that are targeted by the corresponding siRNA, with complete matches. Further short listing to select siRNA with no off-target hits, fulfilling all the guidelines mentioned in approach, provided us 13 siRNAs for haemagglutinin and 13 siRNAs for neuraminidase. The approach of finding siRNA using multiple sequence alignments of amino acid sequences has led to the identification of five conserved amino acid sequences, three in hemagglutinin i.e. RGLFGAIAGFIE, YNAELLV and AIAGFIE and two in neuraminidase i.e. RTQSEC and EECSYP which on reveres translation provided siRNA sequences as potential therapeutic candidates. The approaches used during this study have enabled us to identify potentially therapeutic siRNAs against divergent IVA strains.