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How hemaglutinin work

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  • #61
    Re: How hemaglutinin work

    Coming from a slightly different tack I looked for other viruses that may be behaving in a similar with organ necrosis and sequestered host proteases.

    Expression of factor X and its significance for the determination of paramyxovirus tropism in the chick embryo
    http://www.pubmedcentral.nih.gov/pic...6&blobtype=pdf

    The dancers are different but the dance is the same.

    The virus is Paramyxovirus (Sendi or Newcastle), the protein being cleaved is F Glycoprotien and the protease is factor X (FXa another from the clotting cascade) and they used Russell?s Viper Venom another ?clot buster? to cleave FX into active FXa.

    Viral graphic
    http://www-micro.msb.le.ac.uk/3035/paramyxoviruses.html


    Enveloped animal viruses usually possess a surface glycoprotein which mediates fusion between the viral envelope and host cell membrane, hence enabling the
    initiation of infection, and its biosynthesis often involves post-translational endoproteolytic activation of the inactive precursor by a host cell protease(s). Therefore, the protease distribution in the host must be critical for determining
    the viral tropism. We previously isolated from chick embryo a cogent candidate endoprotease of this kind for paramyxovirus infection, and demonstrated its
    identity with factor X (FX), a vitamin K-dependent serine protease in the prothrombin family which, in general, is synthesized in the liver and circulates as one of the
    plasma proteases essential for blood clotting. Here, we examined FX expression with specific cDNA and antibody probes in a series of embryonic tissues. Many tissues
    other than the liver expressed the specific mRNA but, in most instances, the translation products remained inactive zymogen forms. The enzymatically active FXa was detectable only in the allantoic fluid and amniotic fluid, and virus spreading was strictly confined to the tissues in direct contact with these FXa-containing fluids. Thus, the ectopically expressed FXa is probably the major host determinant of paramyxovirus tropism in ovo.
    and

    Identification of the responsible proteases would be difficult for the natural hosts, such as the mouse lung for Sendai virus and the human upper respiratory tract for
    influenza A viruses. Earlier results suggested the importance of plasminogen activation by physiological and/or bacterial factors (Lazarowitz et al., 1973; Akaike et al., 1989). Furthermore, certain bacterial proteases could directly promote viral activation (Tashiro et al., 1987). FX of plasma origin could also be activated at the sites of tissue damage and inflammation. Moreover, activated macrophages were
    shown to produce FXa (Osterud et al., 1980) or prothrombinase (Schwartz et al., 1982). The tryptase identified in mast cells has a substrate specificity very similar to that of FXa (Kido et al., 1985). Compared with plasmin and bacterial proteases, FXa obviously has a much more stringent substrate specificity and was found to cleave the viral precursors very efficiently (Gotoh et al., 1990). Thus, FXa and FXa-like proteases should also be taken into consideration as potential key enzymes for virus spread in natural hosts.
    Sendi Virus Symptoms (from http://ratguide.com/health/viruses/sendai_virus_sv.php)
    SV is a descending respiratory infection. It begins in the nasal passages, and moves through the trachea into the lungs. Sendai causes necrosis of the respiratory epithelium (thin layer of cells on the surface of the organs). In the first few days of infection epithelium necrosis is mild. As the disease progresses the necrosis becomes severe and usually peaks around day 5. By day 9 the regeneration of respiratory tract surface cells occurs. Focal interstitial pneumonia occurs and inflammation and lesions of varying degrees can develop on the lungs.
    In uncomplicated infection the respiratory system shows evidence of healing within 3 weeks although there may be residual lesions, inflammation, or permanent scarring.




    Originally posted by LMonty
    Thanks for the links, Mingus! that explains how plasminogen works at the cellular level to cleave membrane.

    But what happens to the rest of the body when a sudden process removing significant amounts of plasinogen occurs? What Happens to the activated plasmin, and is there a sudden flush of plasminogen activator?

    Remember the "clot busters" we use in human heartattack and stroke?

    The best known clot buster -after the initial development of streptokinase- is TPa: tissue plasminogen activator! The result is a rapid lysis (breakdown) of all clots present in the stem- and the failure to clot while it is present. The TPa we use to save lives is a mimic of one of the chemicals naturally present in the body.

    Could a plasminogen sequestering virus essentially be activating so much plasmin via a natural version of TPa that the ability to clot at all is temporarily disabled? If so, then it seems to me that once again, viral load is imperitive- the more virus, the more plasminogen sequestered- and the greater production of a natural TPa and thus the "lytic cascade", and the more hemmorhagic activity that is produced.

    A quick PubMed check found quite a few interesting abstracts. HEres one that indicates that theres a potential mechanism here that may apply, although it seems theres an additional step involved- if you look a the proces going on here, then consider a strain that sequesters plasminigem, have we got the potential that a virus that essentially sequesters so much of the circulating clotting factors that ususally maintain balance that a type of DIC is created?

    Influenza A virus infection and pulmonary microthromboembolism.

    Ohrui T, Takahashi H, Ebihara S, Matsui T, Nakayama K, Sasaki H.

    Department of Geriatric and Respiratory Medicine, Tohoku University School of Medicine, Sendai, Japan.

    This report presents the cases of two patients with rapidly progressive hypoxemia associated with influenza A(H3N2) virus infection, who were diagnosed with influenza related acute pulmonary microthromboembolism by serum D-dimer, lung perfusion and ventilation scans and computed-tomography scan of the chest, and were successfully treated by anti-coagulant therapy. The present cases suggest that acute onset pulmonary microthromboembolism should be considered in some patients with sudden, unexplained dyspnea during an outbreak of influenza infection and prompt diagnosis is essential to save the patient from acute death associated with influenza.


    Mingus, I am way, way over my head here- this is cellular biology (and pathology!) at a level I am not educated to. But something rings really true about it- I think we need to look at it. at least find someone who can help us figure it out! I have a feeling it may indeed be part of both the pathnogenesis of ARDS inherant in some strains, and a part of the ability of some strains to cause hemorrhagic bleeding.

    And if it is key to either or both of thse processes- it gives us something to work on....

    Biological properties of baicalein in cardiovascular system.

    Huang Y, Tsang SY, Yao X, Chen ZY.

    Department of Physiology, Chinese University of Hong Kong, Shatin, NT, Hong Kong, China. yu-huang@cuhk.edu.hk

    The dried roots of Scutellaria baicalensis (S. baicalensis) Georgi (common name: Huangqin in China) have been widely employed for many centuries in traditional Chinese herbal medicine as popular antibacterial and antiviral agents. They are effective against staphylococci, cholera, dysentery, pneumococci and influenza virus. Baicalein, one of the major flavonoids contained in the dried roots, possesses a multitude of pharmacological activities. The glycoside of baicalein, baicalin is a potent anti-inflammatory and anti-tumor agent. This review describes the biological properties of baicalein (Table 1), which are associated with the prevention and treatment of cardiovascular diseases. Baicalein is a potent free radical scavenger and xanthine oxidase inhibitor, thus improving endothelial function and conferring cardiovascular protective actions against oxidative stress-induced cell injury. Baicalein lowers blood pressure in renin-dependent hypertension and the in vivo hypotensive effect may be partly attributed to its inhibition of lipoxygenase, resulting in reduced biosynthesis and release of arachidonic acid-derived vasoconstrictor products. On the other hand, baicalein enhances vasoconstricting sensitivity to receptor-dependent agonists such as noradrenaline, phenylephrine, serotonin, U46619 and vasopressin in isolated rat arteries. The in vitro effect is likely caused by inhibition of an endothelial nitric oxide-dependent mechanism. The anti-thrombotic, anti-proliferative and anti-mitogenic effects of the roots of S. baicalensis and baicalein are also reported. Baicalein inhibits thrombin-induced production of plasminogen activator inhibitor-1, and interleukin-1beta- and tumor necrosis factor-alpha-induced adhesion molecule expression in cultured human umbilical vein endothelial cells. The pharmacological findings have highlighted the therapeutic potentials of using plant-derived baicalein and its analogs for the treatment of arteriosclerosis and hypertension.

    Publication Types:
    Review

    PMID: 15853750 [PubMed - indexed for MEDLINE]
    http://www.ncbi.nlm.nih.gov/entrez/q...=pubmed_docsum
    [ Influenza virus proteins modulate hemostasis in vitro and in vivo ]

    [Article in Russian]

    Zhilinskaia IN, Liapina LA, Kiselev OI, Ashmarina IP.

    Institute of Influenza, Russian Academy of Medical Sciences, ul. prof. Popova 15/17, St. Petersburg, 197376 Russia.

    We studied the effect of influenza virus proteins--hemagglutinin, neuraminidase, nucleoprotein, and membrane protein--on hemostasis in vitro and in vivo. The obtained data demonstrated that the envelope proteins hemagglutinin and neuraminidase increased the plasma fibrinolytic and anticoagulant activities and the activity of human tissue plasminogen activator. Among the core proteins of influenza virus, membrane protein proved to have the highest activity; in contrast to hemagglutinin and neuraminidase, it inhibited fibrinolysis, increased the coagulation activity of the plasma, and decreased the activity of human tissue plasminogen activator. Combined action of hemagglutinin and neuraminidase increased the plasma fibrinolytic and anticoagulant activities exceeding their individual effects. Combined action of an envelope protein hemagglutinin and membrane protein also increased the plasma fibrinolytic and anticoagulant activities although to a lesser extent as compared to hemagglutinin alone. The obtained data indicate that the viral proteins are physiologically active and can induce hemostatic changes specific for influenza.

    PMID: 14994476 [PubMed - indexed for MEDLINE]
    http://www.ncbi.nlm.nih.gov/entrez/q...=pubmed_docsum
    PMID: 11128871 [PubMed - indexed for MEDLINE]
    http://www.ncbi.nlm.nih.gov/entrez/q...=pubmed_docsum

    Interactions between bacteria and influenza A virus in the development of influenza pneumonia.

    Scheiblauer H, Reinacher M, Tashiro M, Rott R.

    Institut fur Virologie Justus-Liebig-Universitat, Giessen, Germany.

    Different proteases from various microorganisms present in the respiratory tract were capable of enhancing influenza virus infectivity and pathogenicity in mice by proteolytic activation of hemagglutinin (HA). Aerococcus viridans, isolated from a patient with pneumonia, secreted a protease that could activate HA directly, similarly to some Staphylococcus aureus strains. The protease of Pseudomonas aeruginosa could not activate HA directly, but combined application of P. aeruginosa protease and virus into mice enhanced virus titers and pathogenicity. Generation of trypsin-like activity in bronchoalveolar lavage fluids resulting from this combination treatment may be responsible for HA activation. A similar indirect effect on HA activation was induced by streptokinase and staphylokinase, which are known to generate plasmin by plasminogen activation. It was concluded that plasminogen-activating streptococci and staphylococci facilitate viral replication and pathogenicity of plasmin-sensitive influenza virus strains by amplification of the plasminogen/plasmin system.

    PMID: 1527412 [PubMed - indexed for MEDLINE]

    http://www.ncbi.nlm.nih.gov/entrez/q...=pubmed_docsum

    Molecular mechanism of complex infection by bacteria and virus analyzed by a model using serratial protease and influenza virus in mice.

    Akaike T, Molla A, Ando M, Araki S, Maeda H.

    Department of Microbiology, Kumamoto University Medical School, Japan.

    We examined the effect of a serratial exoprotease on the pathogenesis of influenza virus infection in mice as a model of complicated respiratory infection by bacteria and virus in humans. The 56-kilodalton (56-kDa) protease from Serratia marcescens was administrated intranasally to mice at a dose of 10, 20, or 40 micrograms from day 0 to day 3 after inoculation of the influenza virus. Administration of the protease resulted in remarkable enhancement of the lethal effect of the virus and enhancement of pathological changes in the lungs. Influenza virus replication, determined by plaque-forming assay, was accelerated by the protease. Namely, we found a 100-fold increase in virus yield by day 2. The 56-kDa protease caused generation of plasmin activity in the lungs. In vitro experiments showed that plasmin greatly enhanced the yield of influenza virus, although the effect of the 56-kDa protease by itself was much lower than that of plasmin. Furthermore, the 56-kDa protease could induce plasmin production indirectly via activation of plasminogen by the Hageman factor-dependent cascade in the in vitro system. We conclude that this major serratial exoprotease has a deleterious effect on mice infected with influenza virus and that this effect seems to result from enhancement of viral growth by indirect acceleration of plasmin generation induced by the protease.

    PMID: 2522998 [PubMed - indexed for MEDLINE]
    http://www.ncbi.nlm.nih.gov/entrez/q...=pubmed_docsum

    Comment


    • #62
      Re: How hemaglutinin work

      nice job!

      I read this yesterday, and have been mulling htis around. I think it's over my head, because I dont understand the cascades enough to comprhend the potential outcomes.

      I'd like to take the question to where some physiology experts will see it, and hopefully explain it. I need advice-do we take it to Fluwiki, H5N1 Experts, both? Is this OK with other contributers to this thread?
      Upon this gifted age, in its dark hour,
      Rains from the sky a meteoric shower
      Of facts....They lie unquestioned, uncombined.
      Wisdom enough to leech us of our ill
      Is daily spun, but there exists no loom
      To weave it into fabric..
      Edna St. Vincent Millay "Huntsman, What Quarry"
      All my posts to this forum are for fair use and educational purposes only.

      Comment


      • #63
        Re: How hemaglutinin work

        Sorry LMonty I did'nt have the time to read thoses papers but it seem very interesting. I'll try this week-end
        Is this a potential target for a whole new class of anti-virals ?
        It look like there is something to explore there.

        I would suggest you that you post all thoses articles in the Scientific Literrature section of H5N1experts.org with the links.
        There is no one there yet so if you are familiar with Fluwikki, It could be of interest to ask for expertise there.
        I'm not familiar with fluwikki, my computer and connection are way too slow !

        Comment


        • #64
          Re: How hemaglutinin work

          Thinking about NA sequestering proteases to cleave HA I am a bit confused as to how it may work in practice.

          As I understand it the tertiary structure of proteins is important in presenting the functional regions to each other to effect the required biological activity. In our case the right bit of the protease needs to be in contact with the cleavage site on the HA. In my rather woolly visualisation of this I imagined the NA binding one end of the protease at just the right distance from the HA for the cleaving end to do its thing on the HA cleavage site. This seemed logical if the virons external surface was made up of a regular arrangement of HA & NA molecules. Then I remembered reading that during budding the viron incorporates part of the host cell?s membrane which presumably effects the spatial arrangement of the HA & NA proteins and would therefore change their spatial relationship unpredictably and make cleaving unreliable.

          Where did I go wrong? Was I even close?

          LMonty
          Re posting elseshere its Mingus's Lab if he does not mind I certainly do not - anything that helps is fine by me.

          Comment


          • #65
            Re: How hemaglutinin work

            A link to a power point presentation on the clotting cascade.

            http://www.manfred.maitz-online.de/P...ng-Cascade.ppt

            Comment


            • #66
              Re: Principle of the PCR - Polymerase Chain Reaction

              Originally posted by Mingus


              Real-time PCR system of the 2nd generation.

              This time, no need to run agarose( a kind of tick gello) gel in elecrophorese(electricity in a solution) anymore.
              The machine read the reaction directly by a fluorescent probe.

              But we have to design this probe the same way we design reaction primers with a computer analysys work.

              It give us raw reading like that instead of a fluorescent band in a gel.
              This looks like a real luxury!

              Would bird flu samples be done with this?

              Comment


              • #67
                Re: Principle of the PCR - Polymerase Chain Reaction

                thanks for bumping.

                include the statistics of false positives,false negatives here
                privided by Anne ...(searching for a link...)
                I'm interested in expert panflu damage estimates
                my current links: http://bit.ly/hFI7H ILI-charts: http://bit.ly/CcRgT

                Comment


                • #68
                  Re: Principle of the PCR - Polymerase Chain Reaction

                  >>Yes, all the people that are now working on building and improving
                  >> tools for short read sequencing systems may find that these programs
                  >> need to be thrown out or revamped before long.

                  > This is a rather obvious thing to try,
                  > http://www.nature.com/news/2008/0811...2008.1245.html
                  > A much-watched Silicon Valley company has published a proof of concept for its
                  > DNA-sequencing technology, which it hopes will one day be going through entire human
                  > genomes in minutes.
                  > Pacific Biosciences of Menlo Park, California, reports today that it can generate
                  > continuous stretches of DNA sequence up to thousands of base pairs long.
                  I'm interested in expert panflu damage estimates
                  my current links: http://bit.ly/hFI7H ILI-charts: http://bit.ly/CcRgT

                  Comment


                  • #69
                    Re: How hemaglutinin work

                    new Illumina sequencing machine (2010)
                    costs $700000

                    can sequence 2 human genomes for $10000


                    ... looking for a picture of hemagglutinin with amino-acid numbers,
                    I think we had it somewhere...




                    http://www.ebi.ac.uk/thornton-srv/da...l?pdbcode=1ruz

                    (but no amino-acid-numbers)
                    I'm interested in expert panflu damage estimates
                    my current links: http://bit.ly/hFI7H ILI-charts: http://bit.ly/CcRgT

                    Comment

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