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Biol 460 Test _ 4 Part 1

Biol 460 Test _ 4 Part 1 - F Orthomyxoviridae influenza...

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F. Orthomyxoviridae - influenza - Chapter 31 Influenza is ongoing great plague of mankind and also some animals. Mortalities are common in the elderly (>65yrs) and the high-risk groups. It is generally considered a mild respiratory disease, but it kills thousands of people and is in top 10 causes of death in U.S. a. General properties - Table 31-1, p.491 and Fig. 31-1 p. 490 (1) morphology and replication -ssRNA - pleomorphic - helical symmetry - fragmented genome - 8 fragments (reassortment) - envelope -Antigens: Fig. 1-2 p. 6 External: - H antigen (HA) -hemagglutinin - (14 antigenic subtypes) - trimeric rod-shaped peplomer - receptor for virus to attach to host cells at terminal n-acetyl neuraminic acid (NANA) residues on host cell membrane glycoproteins. Only H1, H2 and H3 subtypes in humans (H1-H14 in birds) - N-neuraminidase Antigen (NA) - (9 antigenic subtypes) - tetrameric mushroom-shaped peplomer -releases virus from cell membrane after budding and prevents viruses from attaching to each other (the membrane receptor NANA is in the viral membrane also.) Ratio of HA to NA about 4-5:1. -Only N1 and N2 in humans; N1-N9 in birds. Internal: - M Ag-membrane protein (matrix protein) - lines inside of envelope - NP Ag-nucleoprotein (capsid Ag associated with genome) From All Virology on WWW: “Influenza virus particles are highly pleiomorphic (variable), mostly spherical/ovoid, 80-120nm diameter, but many forms occur, including long filamentous particles (up to 2000nm long x 80-120nm diameter). Different strains of virus vary in their tendency to form filaments - this property maps to the matrix protein.” The outer surface of the particle consists of a lipid envelope from which project prominent glycoprotein spikes of two types: haemagglutinin (HA), a 135Å trimer neuraminidase (NA), a 60Å tetramer The inner side of the
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