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18 Cards in this Set
- Front
- Back
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Negative Stranded RNA Viruses:
Geometry Enveloped/Non-Enveloped Enzyme Requirements Site of Replication (Exceptions) |
Negative Strand RNA Virus:
Helical and Enveloped MUST CONTAIN RNA-dependent RNA transcriptase to synthesize viral mRNA (uses negative strand as template) Negative strand is not infectious!! (Genome can be segmented/non-segmented) Replicated in CYTOPLASM EXCEPT: INFLUENZA (replicates in nucleus) |
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Orthomyxoviridae:
Subtypes (differences, relevance to humanity) Genome Stability Method of Transmission |
Orthomyxoviridae = FLU VIRUSES
Influenza A, B, C (in order of virulence), only A and B infect humans A has animal reservoir (H1N1, H2N2, H3N2) Segmented genome facilitates dev't of new strains via mutation/reassortment of gene segments (ANTIGENIC REASSORTMENTS), thus, GENETIC INSTABILITY Spread via aerosols Virus concentration high in nasal/tracheal secretions Infects epithelium of respiratory tract Lytic effect = reduced ciliary clearance Note: immune response contributes to epithelial cell death Most serious in elderly |
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Influenza Virus:
Structure Proteins Determining Virulence Relevance to Naming Requirements for Activation |
Influenza:
Enveloped, segmented (-) strand RNA virus Prots: Hemagglutinin (HA): involved in attachment of virus to neuraminic acid (sialic acid) on cell surface and membrane fusion in endosomes To be infectious, HA GLYCOPROT must be cleaved by host cell serine protease (common only at respiratory tract!). HA2 = cleaved product required for host cell entry Neuraminidase Protein (NA) digests sialic acid and is part of virus receptor; allows progeny virions to diffuse once exit cell; involved in penetration of mucus layer in resp tract NA forms tetramer and SA hydrolysis allows release of virus from host cell All influenza viruses typed according to type of HA and NA prots they have |
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What proteins does each segment of the flu genome contain?
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viral RNA and 4 prots:
NP (nucleocapsid protein) PA, PB1, PB2 (RNA polymerase and synthesis) Matrix (M1): assembly, budding M2: pH gated ion channels for viral uncoating |
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Describe the steps of influenza viral replication beginning with HA binding and ending with "snatching".
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HA binds SA receptor
Enter via RECEPTOR-MEDIATED ENDOCYTOSIS Nucleic acid released in cytoplasm Transported to nucleus REPLICATE IN NUCLEUS!!! (EXCEPTION!!!!) Do this bc lack 5' capping activity, so they must 'snatch' newly synthesized caps from euk mRNA in nucleus |
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Antigenic Drift vs Shift
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Drift: mutations in HA and NA genes (occurs slowly), leading to slight variations in flu virus. Occurs in all types.
Antigenic Shift: occurs when cell is doubly infected with more than one type of flu virus (ex: swine flu and human flu); bc genomes are segmented, can reassort and lead to emergence of virus never before seen. ONLY IN TYPE A (occurs infrequently) |
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A virus changing from H1N1 to H3N2 is an example of antigenic _________
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SHIFT
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Paramyxoviridae:
Genome Type Genetic Stability Site of Replication (Exceptions) Method of Transmission Method of Cell Entry Subtypes and Examples Key Proteins and Requirements |
Paramyxoviridae:
spherical, enveloped, NON-SEGMENTED NEGATIVE STRAND RNA NOT SEGMENTED So genetically STABLE Replication in cytoplasm (no exceptions here) Transmission by respiratory droplets Penetrate cell by FUSION with and exit by budding from cell membrane Subtypes: 1)ParamyxoviriNae: Parainfluenza, Mumps, Measles 2) Pneumovirinae: RSV RSV and PARAINFLUENZA are MOST IMPORTANT AGENTS OF RESP INFECTIONS OF INFANTS AND KIDS Measles and mumps are pretty lame too. GLYCOPROTS: Fusion (fusion of viral and host cell membranes) HN (hemaglglutinin-neuraminidase), Hemagglutinin, or G protein = Viral Attachment |
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Mumps:
Glycoprotein for Entry Symptoms |
H
Syx: B/L parotid and submandibular gland enlargement |
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RSV:
Glycoprotein for Entry |
Respiratory Syncytia Virus
G (lacks H or N activity) |
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Parainfluenza:
Glycoprotein for Entry |
HN
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Rubeola:
Glycoprotein for Entry Method of Transmission Clinical Manifestations (2) Associated Disease |
RUBEOLA = MEASLES
Glycoprotein = H (binds to CD46 receptor), NO NA ACTIVITY Transmission via respiratory secretions, local multiplication in resp tract and regional LNs Primary viremia with spread to reticuloendothelial system Secondary viremia disseminates to mucosa of resp, GI, urinary, skin, CNS Replication in epithelium Syx: maculopapular rash (bc T cells targeting infected endothelial cells lining small blood vessels, recovery usually follows) Lifelong immunity established. KOPLIK'S SPOTS! Red spots with blue-white specks in center appear in oral mucosa Assocd Dz: subacute sclerosins panencephatlitis (occasional!) AKA SSPE |
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Rhabdoviridae:
Main genera Method of transmission |
Lyssavirus (RABIES)
Primarily dz of animals Most human cases due to dog bites on DEVELOPING countries In US, most are due to bats! FOllowing inoculation, replicate locally Enter PNS Travels to CNS causes diffuse encephalitis Can then travel to skin, salivary glands |
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What are Negri bodies?
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Pathologic hallmark of Rabies (ephilic cytoplasmic inclusions) identified in brain
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