Control of influenza virus growth by cellular proteins

2006 ◽  
Author(s):  
A. Honda
Keyword(s):  
Influenza Virus ◽  
Cellular Proteins ◽  
Virus Growth

scholarly journals Functional Analysis of PA Binding by Influenza A Virus PB1: Effects on Polymerase Activity and Viral Infectivity

2001 ◽  
Vol 75 (17) ◽  
pp. 8127-8136 ◽  
Author(s):  
Daniel R. Perez ◽  
Ruben O. Donis
Keyword(s):  
Amino Acids ◽  
Influenza Virus ◽  
Amino Acid ◽  
Viral Replication ◽  
Influenza A Virus ◽  
Influenza A ◽  
Amino Acid Sequences ◽  
Influenza Viruses ◽  
Virus Growth ◽  
Transcription And Replication

ABSTRACT Influenza A virus expresses three viral polymerase (P) subunits—PB1, PB2, and PA—all of which are essential for RNA and viral replication. The functions of P proteins in transcription and replication have been partially elucidated, yet some of these functions seem to be dependent on the formation of a heterotrimer for optimal viral RNA transcription and replication. Although it is conceivable that heterotrimer subunit interactions may allow a more efficient catalysis, direct evidence of their essentiality for viral replication is lacking. Biochemical studies addressing the molecular anatomy of the P complexes have revealed direct interactions between PB1 and PB2 as well as between PB1 and PA. Previous studies have shown that the N-terminal 48 amino acids of PB1, termed domain α, contain the residues required for binding PA. We report here the refined mapping of the amino acid sequences within this small region of PB1 that are indispensable for binding PA by deletion mutagenesis of PB1 in a two-hybrid assay. Subsequently, we used site-directed mutagenesis to identify the critical amino acid residues of PB1 for interaction with PA in vivo. The first 12 amino acids of PB1 were found to constitute the core of the interaction interface, thus narrowing the previous boundaries of domain α. The role of the minimal PB1 domain α in influenza virus gene expression and genome replication was subsequently analyzed by evaluating the activity of a set of PB1 mutants in a model reporter minigenome system. A strong correlation was observed between a functional PA binding site on PB1 and P activity. Influenza viruses bearing mutant PB1 genes were recovered using a plasmid-based influenza virus reverse genetics system. Interestingly, mutations that rendered PB1 unable to bind PA were either nonviable or severely growth impaired. These data are consistent with an essential role for the N terminus of PB1 in binding PA, P activity, and virus growth.

scholarly journals ENDOCRINES AND THEIR RELATION TO INFLUENZA VIRUS INFECTION

1951 ◽  
Vol 93 (6) ◽  
pp. 529-538 ◽  
Author(s):  
Seymour S. Kalter ◽  
Harold J. Smolin ◽  
Jane M. McElhaney ◽  
Jay Tepperman
Keyword(s):  
Influenza Virus ◽  
Virus Infection ◽  
Protein Metabolism ◽  
Influenza Virus Infection ◽  
Protein Catabolism ◽  
Virus Growth ◽  
Relative Lack

Treatment with testosterone increases proliferation of influenza virus as well as protein anabolism. A relative lack of testosterone caused by castration is associated with a diminished rate of virus growth. When protein catabolism is increased by ACTH or cortisone, the rate of virus proliferation decreases. These results suggest the existence of a correlation between alterations of protein metabolism and virus proliferation.

scholarly journals Cleavage of Influenza A Virus Hemagglutinin in Human Respiratory Epithelium Is Cell Associated and Sensitive to Exogenous Antiproteases

2002 ◽  
Vol 76 (17) ◽  
pp. 8682-8689 ◽  
Author(s):  
Oleg P. Zhirnov ◽  
Mine R. Ikizler ◽  
Peter F. Wright
Keyword(s):  
Molecular Weight ◽  
Influenza Virus ◽  
Serine Proteases ◽  
Influenza A ◽  
Extracellular Fluid ◽  
Respiratory Epithelium ◽  
Influenza Viruses ◽  
Secretory Cells ◽  
Low Molecular Weight ◽  
Virus Growth

ABSTRACT Proteolytic cleavage of the hemagglutinin (HA) of human influenza viruses A/Aichi/2/68 (H3N2) and A/WSN/34 (H1N1) from HA0 to HA1/HA2 was studied in primary human adenoid epithelial cells (HAEC). HAEC contain a mixture of ciliated and nonciliated secretory cells and mimic the epithelium membrane of the human respiratory tract. Pulse-chase labeling with [35S]methionine and Western blot analysis with anti-HA antibodies of cellular and virion polypeptides showed that HAEC cleaved newly synthesized HA0 to HA1/HA2 (“cleavage from within”) and significant amounts of cleaved HA accumulated within cells. It was also shown that HAEC was able to cleave HA0 of incoming virions (“cleavage from without”), whereas the HA0 of nonabsorbed virions free in extracellular fluid were not cleaved, supporting the conclusion that HA0 cleavage in HAEC is cell associated. Low-molecular-weight inhibitors of serine proteases, aprotinin and leupeptin, when added to influenza virus-infected HAEC suppressed HA0 cleavage and reduced the amount of cleaved HA1/HA2 both in cells and in progeny virions and thus diminished the infectivity of the virus. In contrast, the addition of fetal bovine serum, containing a number of high-molecular-weight antiproteases that compete for proteases in the extracellular environment, did not inhibit influenza virus growth in HAEC. These data suggest that in human respiratory epithelium the cleavage of influenza virus HA containing a single arginine in the proteolytic site (i) is a cell-associated process accomplished by serine-type protease(s) and (ii) is sensitive to low-molecular-weight exogenous inhibitors of serine proteases.

scholarly journals THE EFFECT OF ADRENAL STEROIDS, CORTICOTROPIN, AND GROWTH HORMONE ON RESISTANCE TO EXPERIMENTAL INFECTIONS

1954 ◽  
Vol 99 (1) ◽  
pp. 89-104 ◽  
Author(s):  
Edward H. Kass ◽  
Marguerite M. Lundgren ◽  
Maxwell Finland
Keyword(s):  
Growth Hormone ◽  
Weight Loss ◽  
Influenza Virus ◽  
Survival Time ◽  
Viral Infections ◽  
Adrenal Steroids ◽  
Hydrocortisone Acetate ◽  
Pneumococcal Infections ◽  
Virus Growth ◽  
Experimental Infections

Cortisone acetate, hydrocortisone, and hydrocortisone acetate depress the resistance of mice to pneumococcal and influenza viral infections, although hydrocortisone acetate is somewhat less effective than the free alcohol, when given subcutaneously. Pituitary adrenocorticotropin, even in highly purified form and in oil and beeswax, does not significantly alter the resistance of mice to these experimental infections, even when given in doses which may cause profound eosinopenia, lymphopenia, and weight loss, and which are at the limit of tolerance of the animals. Corticosterone depresses resistance to pneumococcal infections significantly, but fails to alter resistance to influenza viral infections. The findings suggest that murine adrenals may produce one of the known adrenal steroids such as corticosterone along with another steroid, or may produce a steroid other than cortisone, hydrocortisone, or corticosterone. When resistance is decreased by adrenal steroids, survival time is invariably shortened, and the effect of the steroid hormones is frequently demonstrable within the 1st day after infection with pneumococci, making it unlikely that the depression of resistance that is seen is primarily due to depression of antibody formation. A single dose of 5 mg. of cortisone may cause depression of resistance and may decrease the survival time for 3 to 6 days afterward. Growth hormone (somatotropic hormone) in highly purified form, and in the doses used, did not overcome the weight loss induced by cortisone, but the animals treated with growth hormone and cortisone regained their lost weight more rapidly than those receiving cortisone alone. Growth hormone alone caused a slight increase in the rate of gain in weight over controls. Growth hormone alone did not increase resistance to infection, and did not increase the survival time, in mice infected with either pneumococci or influenza virus. Growth hormone in various dosages failed to overcome the effect of cortisone in depressing resistance to these infections. Cortisone, hydrocortisone, corticosterone, and corticotropin did not alter significantly the titers of influenza virus attained in the murine lungs during the first 2 days after infection, but cortisone and hydrocortisone markedly delayed the rate at which virus titers declined during the subsequent 6 days. Corticosterone and corticotropin delayed the rate at which the titers declined but slightly, and growth hormone had no apparent effect, as compared with controls. Growth hormone did not overcome the effect of cortisone and hydrocortisone on viral titers. No detectable antibody was found as late as 6 days after infection, in controls or in hormone-treated animals.

scholarly journals Interleukin-18 improves the early defence system against influenza virus infection by augmenting natural killer cell-mediated cytotoxicity

2004 ◽  
Vol 85 (2) ◽  
pp. 423-428 ◽  
Author(s):  
Beixing Liu ◽  
Isamu Mori ◽  
Md Jaber Hossain ◽  
Li Dong ◽  
Kiyoshi Takeda ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Virus Infection ◽  
Natural Killer ◽  
Influenza A ◽  
Nk Cell ◽  
Early Stage ◽  
Killer Cell ◽  
Influenza Virus Infection ◽  
Virus Growth ◽  
Defence System

The role of interleukin (IL)-18 in the development of the host defence system against influenza virus infection was investigated. IL-18-deficient (IL-18−/−) C57BL/6 mice that were inoculated intranasally with the mouse-adapted strain of human influenza A/PR/8/34 (H1N1) virus showed an increased mortality with the occurrence of pathogenic changes in the lung for the first 3 days of infection, which included pronounced virus growth with massive infiltration of inflammatory cells and elevated nitric oxide production. The interferon-gamma (IFN-γ) level induced in the respiratory tract of IL-18−/− mice in the first few days after virus infection was significantly lower but, in contrast, the IL-12 level was slightly higher than the corresponding levels in wild-type C57BL/6 mice. Natural killer (NK) cell-mediated cytotoxicity in the lung of IL-18−/− mice was poorly activated. Local immune responses in the lung such as specific cytotoxic T lymphocyte and antibody production were induced upon influenza virus infection equally well in both strains of mice. These results indicate that IL-18 is involved in controlling influenza virus replication in the lung, especially at an early stage of infection, through activation of the innate immune mechanisms such as IFN and NK cells.

scholarly journals Identification of Influenza A Virus PB2 Residues Involved in Enhanced Polymerase Activity and Virus Growth in Mammalian Cells at Low Temperatures

2015 ◽  
Vol 89 (15) ◽  
pp. 8042-8049 ◽  
Author(s):  
Tsuyoshi Hayashi ◽  
Saintedym Wills ◽  
Kendra A. Bussey ◽  
Toru Takimoto
Keyword(s):  
Influenza Virus ◽  
Low Temperature ◽  
Respiratory Tract ◽  
Mammalian Cells ◽  
Influenza A ◽  
Polymerase Activity ◽  
Upper Respiratory Tract ◽  
Virus Growth ◽  
Avian Origin ◽  
Upper Respiratory

ABSTRACTMutations in the polymerase genes are known to play a major role in avian influenza virus adaptation to mammalian hosts. Despite having avian origin PA and PB2, the 2009 pandemic H1N1 virus (pH1N1) can replicate well in mammalian respiratory tracts, suggesting that these proteins have acquired mutations for efficient growth in humans. We have previously shown that PA from the pH1N1 virus A/California/04/09 (Cal) strongly enhances activity of an otherwise avian polymerase complex derived from A/chicken/Nanchang/3-120/01 (Nan) in mammalian cells. However, this enhancement was observed at 37°C but not at the lower temperature of 34°C. An additional introduction of Cal PB2 enhanced activity at 34°C, suggesting the presence of unidentified residues in Cal PB2 that are required for efficient growth at low temperature. Here, we sought to determine the key PB2 residues which confer enhanced polymerase activity and virus growth in human cells at low temperature. Using a reporter gene assay, we identified novel mutations, PB2 V661A and V683T/A684S, which are involved in enhanced Cal polymerase activity at low temperature. The PB2 T271A mutation, which we previously reported, also contributed to enhanced activity. The growth of recombinant Cal containing PB2 with Nan residues 271T/661V/683V/684A was strongly reduced in human cells compared to wild-type virus at low temperature. Among the four residues, 271A and 684S are conserved in human and pH1N1 viruses but not in avian viruses, suggesting an important role in mammalian adaptation of pH1N1 virus.IMPORTANCEThe PB2 protein plays a key role in the host adaptation, cold sensitivity, and pathogenesis of influenza A virus. Despite containing an avian origin PB2 lacking the mammalian adaptive mutations 627K or 701N, pH1N1 influenza virus strains can replicate efficiently in the low temperature upper respiratory tract of mammals, suggesting the presence of unknown mutations in the pH1N1 PB2 protein responsible for its low temperature adaptation. Here, in addition to PB2 271A, which has been shown to increase polymerase activity, we identified novel PB2 residues 661A and 683T/684S in pH1N1 which confer enhanced polymerase activity and virus growth in mammalian cells especially at low temperature. Our findings suggest that the presence of these PB2 residues contributes to efficient replication of the pH1N1 virus in the upper respiratory tract, which resulted in efficient human-to-human transmission of this virus.

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