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26 Cards in this Set
- Front
- Back
Orthomyxoviruses
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-spherical or ovoid enveloped
-buds -2 major envelope surface glycoproteins: NA and HA -ssRNA (-) all within matrix -helical nucleocapsid made of nucleocapsid protein |
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Neuraminidase
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-major envelope surface glycoprotein
-orthomyxoviruses -used to distinguish subtype of virus within subtype (influenza A H1N1) |
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Hemagglutinin
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-major envelope surface glycoprotein
-orthomyxoviruses -used to distinguish subtype of virus within subtype (influenza A H1N1) |
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Influenza A
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-widespread various animals
-genomes into 8 pieces, each for different protein, allowing to recombine when two subtypes co-infect -13500 nt genome -most clinically important subtype -imported and grows into episodic epidemic (Dec-Mar) -large genetic pool, recombination easier -highly variable antigenic properties for survival |
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Influenza B
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-only humans
-genomes into 8 pieces, each for different protein -not much recombination, smaller genomic pool (only humans) |
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Influenza C
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-only humans
-7 segments genome -not much recombination, smaller genomic pool (only humans) |
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Thogotovirus
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-tick-borne
-not well characterised -6 segments genome |
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Matrix
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-composed of matrix protein M1
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Mouse tracheal cells experiment
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-shows influenza destroys first line of defese against inhaled pathogens (bacteria)
-through desquamation of ciliated epithelium, virus facilitates bacterial entry |
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Desquamation
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-replicating virus in and thus killing round mucous-secreting cells and ciliated upwards beating cells of upper tracheal epithelium
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Hemophilus influenzae
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-gram negative coccobacillus
-cause of 1918 Spanish flu pandemic -human experiments show maximal illness at same time maximal viral sheeding |
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Flu (A) symptoms
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-due to produciton of interferon, cytokines and repsonse factros in response to viral replication
-1-4 days after infection |
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Flu pandemics
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-10-50 years irregularly
-1918 Spanish -1957 Asian -1967 Hong Kong |
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Natural Immunity against flu
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-against NA and HA
-no cross immunity of subtypes -protective immunity that is not lifelong since glycoproteins regularly undergo antigenic drift |
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Antigenic Drift
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-mutational antigenicity
-1% change in AA sequence glycoprotines per year through random point mutations in antigenic domains |
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Antigenic Shift
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-every decade or so happens to one glycoprotein
-through genetic recombination with animal influenza subtypes -potential to be pandemic or epidemic |
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Antigenic diversity
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-increased by virally encoded error-prone RNA dependedent RNA polymerase
-high nucleotide or aa sequence diveristy in WT viral particles |
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Spanish flu
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-1918
-20 million deaths -H1N1 -avian/human recombinant formed in infected swine cell -cyclic shift allowed influneza to remain pathogenic -disappeared in 1956 along with appearance H2N2 |
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1880 Flu
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-H3N2
-cyclic shift to 1968 but most population in flu from 1880 had died |
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Asian flu 1
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-1947
-H1N1 |
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Asian flu 2
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-1957
-H2N2 |
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Hong Kong flu
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-1968
-H3N2 -due to antigenic shift |
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Swine flu scare
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-1976
-H3N2+H1N1 -deadly flu containing Hswine thought to be new recombitnant -actually no recombination -human-human transmission are low |
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Cross-specicies infection
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-by influenza usualyl does not occur unless large inoculate
-due to host specificity therefore does not occur |
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Avian flu
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-resevoirs, not affected
-H5N1 -humans have partial immunity to N1, no immunity to H5 -although all carry H6 and N1, rest genes are bird genes -jumped species barrier due to proximity -66 cases in humans, no human-human transmission -gets into human respiratory tract, fear of it encoutnering human influenza and recombining making easy spread human to human and therefore pandemic |
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Influenza A genome
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-3 largest segments: polymerase proteins
-4th: hemagglutinin -5th: nucleoprotein -6th: neuraminidase -7th: matrix protein (smaller) -8th: major non structural protein NS1 (smaller) -splicing mechanism makes sub genomic mRNA's encoding two small addition proteins |