scholarly journals A Mutant H3N2 Influenza Virus Uses an Alternative Activation Mechanism in TMPRSS2 Knockout Mice by Loss of an Oligosaccharide in the Hemagglutinin Stalk Region

2015 ◽  
Vol 89 (9) ◽  
pp. 5154-5158 ◽  
Author(s):  
Kouji Sakai ◽  
Tsuyoshi Sekizuka ◽  
Yasushi Ami ◽  
Noriko Nakajima ◽  
Minori Kitazawa ◽  
...  

The host protease TMPRSS2 plays an essential role in proteolytic activation of the influenza A virus (IAV) hemagglutinin (HA) protein possessing a monobasic cleavage site. However, after passages in TMPRSS2 knockout mice, an H3N2 subtype IAV began to undergo cleavage activation of HA, showing high virulence in the mice due to the loss of an oligosaccharide at position 8 in the HA stalk region. Thus, the H3N2 IAV acquired cleavability by an alternative HA activation mechanism/protease(s).

2021 ◽  
Vol 10 (36) ◽  
pp. 167-169
Author(s):  
Camila Siqueira ◽  
Diogo Kuczera ◽  
Eneida Da Lozzo ◽  
Dorly Buchi ◽  
José Nelson Couceiro ◽  
...  

Introduction: Strains of macrophages, such as murine J774.G8 macrophages, are susceptible to influenza A infection [1]. One of the responses to viral infection involves the production of various types of immunostimulatory cytokines by infected cells [2]. Methods: In the present study, the macrophage strain J774.G8, maintained in RPMI medium, was submitted to treatment with 10% V/V of two different biotherapics prepared from influenza H3N2, both at 30x. Additionally, two control groups were analyzed: macrophages stimulated with water 30x and macrophages without any treatment. Biotherapics were prepared from intact H3N2 influenza virus and H3N2 inactivated by alcohol 70%. The compounding of both biotherapics followed this procedure: one part of viral particles was diluted in 9 parts of sterile distilled water. The 1:10 sample was submitted to 100 mechanical succussions using Autic® Brazilian machine, originating the first dilution, named decimal (1x). 1 ml of this solution was diluted in 9 ml of solvent and was submitted to 100 succussions, generating biotherapic 2x. This procedure was successively repeated, according to Brazilian Homeopathic Pharmacopoeia, to obtain the biotherapic 30x. By the same technique, water vehicle was prepared in the potency of 30x to be used as control. All samples were prepared under sterile and aseptic conditions, using laminar flow cabinet, class II, and were stored in the refrigerator (8ºC), to avoid microbiological contamination. J774.G8 macrophages were stimulated for 2 days, in a total of six stimuli. Immediately before infection with 25 µl of H3N2 influenza virus, the supernatants were collected and frozen at -20 ºC for later analysis. Next, 24 hours after the virus infection, the supernatants were aliquoted and frozen under the same conditions. Three independent experiments were done in triplicate. Analysis of supernatants was performed by flow cytometry using the Mouse Inflammation Kit. The cytokines detected in this experiment were IL-10, IL 12, TNF-α and MCP1. Results: In all cases, there were no significant differences compared to control groups. However, the production of TNF-α detected in macrophages treated by intact and inactivated biotherapics presented a tendency to increase after infection. In fact, similar results were previously detected in other experiments conducted only with the intact biotherapic [3]. The release of the cytokine MCP1 in all experimental situations presented a tendency to decrease after the viral infection when compared to untreated macrophages. No statistically significant difference was detected in the production of IL 12 and IL 10. These experiments will be repeated to confirm the data obtained.


2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Jumpei Omi ◽  
Miho Watanabe-Takahashi ◽  
Katsura Igai ◽  
Eiko Shimizu ◽  
Ching-Yi Tseng ◽  
...  

AbstractThe emergence of drug-resistant influenza type A viruses (IAVs) necessitates the development of novel anti-IAV agents. Here, we target the IAV hemagglutinin (HA) protein using multivalent peptide library screens and identify PVF-tet, a peptide-based HA inhibitor. PVF-tet inhibits IAV cytopathicity and propagation in cells by binding to newly synthesized HA, rather than to the HA of the parental virus, thus inducing the accumulation of HA within a unique structure, the inducible amphisome, whose production from the autophagosome is accelerated by PVF-tet. The amphisome is also produced in response to IAV infection in the absence of PVF-tet by cells overexpressing ABC transporter subfamily A3, which plays an essential role in the maturation of multivesicular endosomes into the lamellar body, a lipid-sorting organelle. Our results show that the inducible amphisomes can function as a type of organelle-based anti-viral machinery by sequestering HA. PVF-tet efficiently rescues mice from the lethality of IAV infection.


2002 ◽  
Vol 46 (4) ◽  
pp. 1014-1021 ◽  
Author(s):  
Warren M. Kati ◽  
Debra Montgomery ◽  
Robert Carrick ◽  
Larisa Gubareva ◽  
Clarence Maring ◽  
...  

ABSTRACT A-315675 is a novel, pyrrolidine-based compound that was evaluated in this study for its ability to inhibit A and B strain influenza virus neuraminidases in enzyme assays and influenza virus replication in cell culture. A-315675 effectively inhibited influenza A N1, N2, and N9 and B strain neuraminidases with inhibitor constant (Ki ) values between 0.024 and 0.31 nM. These values were comparable to or lower than the Ki values measured for oseltamivir carboxylate (GS4071), zanamivir, and BCX-1812, except for the N1 enzymes that were found to be the most sensitive to BCX-1812. The time-dependent inhibition of neuraminidase catalytic activity observed with A-315675 is likely due to its very low rate of dissociation from the active site of neuraminidase. The half times for dissociation of A-315675 from B/Memphis/3/89 and A/Tokyo/3/67 (H3N2) influenza virus neuraminidases of 10 to 12 h are significantly slower than the half times measured for oseltamivir carboxylate (33 to 60 min). A-315675 inhibited the replication of several laboratory strains of influenza virus in cell culture with potencies that were comparable or superior to those for oseltamivir carboxylate and BCX-1812, except for the A/H1N1 viruses that were found to be two- to fourfold more susceptible to BCX-1812. A-315675 and oseltamivir carboxylate exhibited comparable potencies against a panel of A/H1N1 and A/H3N2 influenza virus clinical isolates, but A-315675 was found to be significantly more potent than oseltamivir carboxylate against the B strain isolates. The favorable in vitro results relative to other clinically effective agents provide strong support for the further investigation of A-315675 as a potential therapy for influenza virus infections.


Author(s):  
Michael L. Knight ◽  
Haitian Fan ◽  
David L. V. Bauer ◽  
Jonathan M. Grimes ◽  
Ervin Fodor ◽  
...  

Influenza A viruses of the H1N1 and H3N2 subtypes are responsible for seasonal epidemic events. The influenza nucleoprotein (NP) binds to the viral genomic RNA and is essential for its replication. Efforts are under way to produce therapeutics and vaccines targeting the NP. Despite this, no structure of an NP from an H3N2 virus has previously been determined. Here, the structure of the A/Northern Territory/60/1968 (H3N2) influenza virus NP is presented at 2.2 Å resolution. The structure is highly similar to those of the A/WSN/1933 (H1N1) and A/Hong Kong/483/97 (H5N1) NPs. Nonconserved amino acids are widely dispersed both at the sequence and structural levels. A movement of the 73–90 RNA-binding loop is observed to be the key difference between the structure determined here and previous structures. The data presented here increase the understanding of structural conservation amongst influenza NPs and may aid in the design of universal interventions against influenza.


2019 ◽  
Vol 93 (22) ◽  
Author(s):  
Lauren Byrd-Leotis ◽  
Chao Gao ◽  
Nan Jia ◽  
Akul Y. Mehta ◽  
Jessica Trost ◽  
...  

ABSTRACT H3N2 strains of influenza A virus emerged in humans in 1968 and have continued to circulate, evolving in response to human immune pressure. During this process of “antigenic drift,” viruses have progressively lost the ability to agglutinate erythrocytes of various species and to replicate efficiently under the established conditions for amplifying clinical isolates and generating vaccine candidates. We have determined the glycome profiles of chicken and guinea pig erythrocytes to gain insights into reduced agglutination properties displayed by drifted strains and show that both chicken and guinea pig erythrocytes contain complex sialylated N-glycans but that they differ with respect to the extent of branching, core fucosylation, and the abundance of poly-N-acetyllactosamine (PL) [-3Galβ1-4GlcNAcβ1-]n structures. We also examined binding of the H3N2 viruses using three different glycan microarrays: the synthetic Consortium for Functional Glycomics array; the defined N-glycan array designed to reveal contributions to binding based on sialic acid linkage type, branched structures, and core modifications; and the human lung shotgun glycan microarray. The results demonstrate that H3N2 viruses have progressively lost their capacity to bind nearly all canonical sialylated receptors other than a selection of biantennary structures and PL structures with or without sialic acid. Significantly, all viruses displayed robust binding to nonsialylated high-mannose phosphorylated glycans, even as the recognition of sialylated structures is decreased through antigenic drift. IMPORTANCE Influenza subtype H3N2 viruses have circulated in humans for over 50 years, continuing to cause annual epidemics. Such viruses have undergone antigenic drift in response to immune pressure, reducing the protective effects of preexisting immunity to previously circulating H3N2 strains. The changes in hemagglutinin (HA) affiliated with drift have implications for the receptor binding properties of these viruses, affecting virus replication in the culture systems commonly used to generate and amplify vaccine strains. Therefore, the antigenic properties of the vaccines may not directly reflect those of the circulating strains from which they were derived, compromising vaccine efficacy. In order to reproducibly provide effective vaccines, it will be critical to understand the interrelationships between binding, antigenicity, and replication properties in different growth substrates.


1981 ◽  
Vol 86 (3) ◽  
pp. 303-313 ◽  
Author(s):  
L. H. Taber ◽  
A. Paredes ◽  
W. P. Glezen ◽  
R. B. Couch

SUMMARYIn 1976, an epidemic caused by infections with an influenza virus antigenically similar to A/Victoria/75 (H3N2) occurred in Houston, Texas. During this outbreak, 37 families (155 members) enrolled in the Houston Family Study were under observation. The families lived throughout the metropolitan area (Houston, Texas), and were representative of low income groups. The overall frequency of infection in family members was 27·7%. The frequency of infection was the highest for infants under one year of age and for their older siblings, 14 (37·8%) of 37 and 17 (33·3%) of 51, respectively. Eighteen (48·6%) of the 37 families had at least one infected member. Twelve of the 18 ‘infected’ families had school aged children, whereas only three of the 19 ‘non-infected’ families had school aged children (P < 0·01). These infected families were also larger and had increased household density (persons/rooms). The levels of pre-existing HI antibodies to A/Victoria/75 and A/Port Chalmers/73 were inversely related to frequencies of infection and illness associated with A/Victoria/75 virus. Three children required hospitalization as direct consequence of their infection with this H3N2 influenza virus. Antibody response to infection was related to previous experience with antigenically-related influenza A (H3N2) viruses according to Francis', ‘doctrine of original antigenic sin.’


2016 ◽  
Vol 90 (9) ◽  
pp. 4298-4307 ◽  
Author(s):  
Nora Kühn ◽  
Silke Bergmann ◽  
Nadine Kösterke ◽  
Ruth L. O. Lambertz ◽  
Anna Keppner ◽  
...  

ABSTRACTCleavage of influenza virus hemagglutinin (HA) by host cell proteases is necessary for viral activation and infectivity. In humans and mice, members of the type II transmembrane protease family (TTSP), e.g., TMPRSS2, TMPRSS4, and TMPRSS11d (HAT), have been shown to cleave influenza virus HA for viral activation and infectivityin vitro. Recently, we reported that inactivation of a single HA-activating protease gene,Tmprss2, in knockout mice inhibits the spread of H1N1 influenza viruses. However, after infection ofTmprss2knockout mice with an H3N2 influenza virus, only a slight increase in survival was observed, and mice still lost body weight. In this study, we investigated an additional trypsin-like protease, TMPRSS4. Both TMPRSS2 and TMPRSS4 are expressed in the same cell types of the mouse lung. Deletion ofTmprss4alone in knockout mice does not protect them from body weight loss and death upon infection with H3N2 influenza virus. In contrast,Tmprss2−/−Tmprss4−/−double-knockout mice showed a remarkably reduced virus spread and lung pathology, in addition to reduced body weight loss and mortality. Thus, our results identified TMPRSS4 as a second host cell protease that, in addition to TMPRSS2, is able to activate the HA of H3N2 influenza virusin vivo.IMPORTANCEInfluenza epidemics and recurring pandemics are responsible for significant global morbidity and mortality. Due to high variability of the virus genome, resistance to available antiviral drugs is frequently observed, and new targets for treatment of influenza are needed. Host cell factors essential for processing of the virus hemagglutinin represent very suitable drug targets because the virus is dependent on these host factors for replication. We reported previously thatTmprss2-deficient mice are protected against H1N1 virus infections, but only marginal protection against H3N2 virus infections was observed. Here we show that deletion of two host protease genes,Tmprss2andTmprss4, strongly reduced viral spread as well as lung pathology and resulted in increased survival after H3N2 virus infection. Thus, TMPRSS4 represents another host cell factor that is involved in cleavage activation of H3N2 influenza virusesin vivo.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
James D. Allen ◽  
Ted M. Ross

AbstractWhile vaccines remain the best tool for preventing influenza virus infections, they have demonstrated low to moderate effectiveness in recent years. Seasonal influenza vaccines typically consist of wild-type influenza A and B viruses that are limited in their ability to elicit protective immune responses against co-circulating influenza virus variant strains. Improved influenza virus vaccines need to elicit protective immune responses against multiple influenza virus drift variants within each season. Broadly reactive vaccine candidates potentially provide a solution to this problem, but their efficacy may begin to wane as influenza viruses naturally mutate through processes that mediates drift. Thus, it is necessary to develop a method that commercial vaccine manufacturers can use to update broadly reactive vaccine antigens to better protect against future and currently circulating viral variants. Building upon the COBRA technology, nine next-generation H3N2 influenza hemagglutinin (HA) vaccines were designed using a next generation algorithm and design methodology. These next-generation broadly reactive COBRA H3 HA vaccines were superior to wild-type HA vaccines at eliciting antibodies with high HAI activity against a panel of historical and co-circulating H3N2 influenza viruses isolated over the last 15 years, as well as the ability to neutralize future emerging H3N2 isolates.


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