INFLUENZA VIRUS INTRODUCTION Family orthomyxoviridea Genus influenza virus Genome RNA Types A,...
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INFLUENZA VIRUS
INTRODUCTION
Family orthomyxoviridea Genus influenza virus
Genome RNA
Types A, B, C
HISTORYIn 1918, J.S. Koen, a veterinarian, observed
a disease in pigsIn 1928, N. McBryde attempted to transmit
influenza from pig to pigRobert Shope inoculated unfiltered material The term “influenza” was coined by an
Italian in the mid-1700’s to connote a disease resulting from miasma (bad air).
Wilson Smith, Christopher Andrews, and Patrick Laidrow first identified the virus that causes human influenza
STRUCTURE OF INFLUENZA Roughly Spherical
Virion diameter ranges from 80-120 nanometers
Enveloped virus,the outer layer is lipid membrane taken from host in which virus multiplies
Inserted on membrane are SPIKES
These spikes are the glycoproteins known as Hemagglutinin (HA)
Neuraminidase (NA)
These are the proteins that determine the type of the influenza virus(A,B, and C) and the subtypes(e.g. A/H1N1)
Embedded on the lipid membrane is the M2(ion channel),which is the target of the antiviral adamantanes
Beneath the lipid membrane is a viral protein called M1(matrix protein).This protein which form a shell gives strength and rigidity to the lipid envelope
Interior of the virion are the viral RNAs ,genetic material which code for proteins
NEP,another protein is also present
Its genome is not single piece of nucleic acid but consists of pieces of segmented negative sense RNAs
Influenza A and B 8 segments of ssRNA Influenza C
7 segments of ssRNA with negative polarity
HEMAGGLUTININ Named because of its ability to
agglutinate or clump the host’s RBCs16 HA antigenic subtypes from H1 –H1680% spikes are hemagglutinin It is a trimeric,combination of three
identical proteins,bound together to form a cylindrical shape
It binds virus to target cell and enter viral genome in the target cell
Hemaggulutinin
VIRUS HOST INTERACTION
NEURAMINIDASEIt is shaped like a squareThere are 9 subtypes of NA:N1 through
N9The top consists of 4 identical proteins
forming a roughly spherical shapeIts is involved in the release of progeny
virus from infected cells by cleaving sugars that bind the mature viral particles
It cleaves terminal sialic acid residues from host membrane bound glycoprotein and glycolipids
NEURAMINIDASE
oThese proteins are the antigen to which antibodies can be raised These proteins are the targets of antiviral drugs
The virus is constantly changing its structure