Hemagglutinin activity

Hemagglutinin activity. Saline extract of the dried seed, at a concentration of 10%, was active on the human red blood cells L Hypocholestrolemic activity. Fresh root, taken orally by human adults at a dose of 200 g/person, was active. Daily ingestion at breakfast for 3 weeks decreased cholesterol in serum by 11%, increased fecal bile acid and fat excretion by 50%, and increased stool weight by 25%° . 

Pahl, H. and Baeuerle, P. Expression of influenza virus hemagglutinin activates transcription factor NF-kappa B. Journal of Virology 69 1480-1484 1995. 

Tepal et al (1994) extruded jack bean powder to remove several undesirable compounds screw speed had no effect. Extrusion significantly decreased hemagglutinins and urease activity, but not canavanine levels. Since nitrogen solubility was also reduced by extrusion, this index could be used as a marker for protein-based unwanted materials. Other workers have reported that all antinutrients could not be destroyed simultaneously or to the same extent. Gujska and Khan (1991) found that nearly all hemagglutinin activity was eradicated in navy, pinto and garbanzo bean high starch fraction, but trypsin inhibitors were reduced only 70-85% under the extrusion conditions used. 

Laver WG, Colman PM, Webster RG, Hinshaw VS, Air GM (1984) Influenza virus neuraminidase with hemagglutinin activity. Virology 137 314-323... 

Nuss JM, Air CM. (1991) Transfer of the hemagglutinin activity of influenza virus neuraminidase subtype N9 into an N2 background. Virology 183, 496-504. 

Lipkind, M., and Tsvetkova, I. V., 1971, Disappearance of neuraminidase and hemagglutinin activities in NDV-infected chick embryo cell monolayer culture with inhibitors of protein synthesis. Arc/ . Ges. Vimsforch. 35 303-307. 

This fusogenic activity of influenza hemagglutinin is frequently exploited in the laboratory. If, for example, the virus is bound to cells at a temperature too low for endocytosis and then the pH of the external medium is lowered, the hemagglutinin causes direct fusion of the viral envelope with the plasma membrane infection is achieved without endocytosis. Similarly, artificial vesicles with hemagglutinin in their membrane and other molecules in their lumen can be caused to fuse with cells by first allowing the vesicles to bind to the plasma membrane via the hemagglutinin and then lowering the pH of the medium. In this way the contents of the vesicles are delivered to the recipient cell s cytoplasm. 

The influenza virus inhibitors, zanamivir, and oseltamivir, act outside the cell after virus particles have been formed. The dtugs have been designed to fit into the active site of the viral envelope enzyme neuraminidase, which is required to cleave sialic acid off the surface of the producing cells. When its activity is blocked, new virus particles stay attached to the cell surface through binding of the virus protein hemagglutinin to sialic acid and are prevented from spreading to other cells. 

Watowich, S., Morimoto, R.I., Lamb, R.A. (1991). Flux of the paramyxovirus hemagglutinin-neuraminidase glycoprotein through the endoplasmic reticulum activates transcription of the grp78-Bip gene. J. Virol. 65, 3690-3697. 

Figure 8. Antigenic sites in the fusion region of influenza virus hemagglutinin of strains A and B. The sites have been localized and their antigenic activity confirmed by synthesis and reactivity with rabbit, goat, and mouse antivirus and antihemagglutinin antibodies. Also, each of the peptides bound considerable amounts of anti-influenza antibodies from sera of human individuals after influenza attack. Reproduced with permission from Ref. 29.

Influenza virus resistant to oseltamivir has not been found in naturally acquired isolates but has been isolated from influenza patients who have undergone treatment with this drug. These resistant strains contain mutations in the active site of neuraminidase and are generally less virulent and infective than nonresistant virus. In vitro passage of influenza virus in the presence of oseltamivir carboxylate can produce mutations in hemagglutinin that decrease the overall dependence of viral replication on neuraminidase however, the clinical relevance of this resistance mechanism is unknown. 

Zanamivir (Relenza) is a neuraminidase inhibitor with activity against influenza A and B strains. Like oseltamivir, zanamivir is a reversible competitive antagonist of viral neuraminidase. It inhibits the release of progeny virus, causes viral aggregation at the cell surface, and impairs viral movement through respiratory secretions. Resistant variants with hemagglutinin and/or neuraminidase mutations have been produced in vivo however, clinical resistance to zanamivir is quite rare at present. 

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