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Microbio-virology > Veterinary virology > Flashcards

Veterinary virology Flashcards

1
Q

Foot and mouth disease

A
  • Loeffler and Frosch (1898) reported transmission in cattle of filterable and contagious agent
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2
Q

From 1900-1905 the filterable nature of some virulent infections demonstration with

A
  • African horse sickness
  • fowl plague (HP avian influenza)
  • canine distemper
  • equine infectious anemia
  • rinderpest
  • classical swine fever
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3
Q

Dr. Peyton Rous

A
  • 1911 discovered first virus capable of inducing neoplasia
    • Rous sarcoma virus
    • nobel prize in medicine
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4
Q

embryonated eggs

A
  • used started 1931
  • viruses could now be grown
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5
Q

Dr. Shope 1933

A
  • isolates flu virus H1N1 from swin isolated from humans in 1933
    • first emerging disease in animals that cross species barrier
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6
Q

Chorioallantoic membrane inoculation

A
  • Herpes simplex virus
  • Pox virus
  • Rous sarcoma virus
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7
Q

Amniotic inoculation

A
  • Influenza virus
  • Mumps virus
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8
Q

Yolk sac inoculation

A
  • Herpes simplex virus
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9
Q

Allantoic inoculation

A
  • Influenza virus
  • Mumps virus
  • Newcastle disease virus
  • Avian adenovirus
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10
Q

Price of virus outbreaks in domestic animals

Feline parvovirus

A
  • variant crosses species barrier
  • produced worldwide epizootic in dogs in late 70s
  • vaccine was eventually developed to control dz
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11
Q

Price of virus outbreaks in domestic animals

HPAI virus epornitic

A
  • April-June 2015 in upper Midwest US
  • affected 211 commercial farms
  • causes destruction of 7.5 million turkeys and 38.5 million hens
  • more than US $1.5 billion in industry losses
  • Probably inc in price for consumers > US $2 billion
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12
Q

Molecular era of Virology

A
  • 1981 DNA cloning led to development of infectious viral clones
  • 1983 PCR developed
  • Viruses that we couldn’t culture now characterized molecularly
    • papillomavirus
    • norovirus
    • rotavirus
  • Molecular reconstruction of 1918 flu virus from RNA frags
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13
Q

Head of a dress-makers pin

A
  • Large enough for five hundred million rhinoviruses (common cold)
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14
Q

Virus characteristics

(5 characteristics)

A
  • All are obligate intracellular parasites
  • lack metabolic machinery to reproduce
  • inert particles outside living cells
  • Do not reproduce by binary fission
  • replication like an assembly line with parts from a host cell
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15
Q

Eclipse period

A
  • Time elapsed between virus penetration into host cell and production of new virus
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16
Q

Enveloped virus

A
  • Examples
    • herpes
    • pox
    • retro
    • paramyxo
    • orthomyxoviruses
  • inactivated by organic solvents
17
Q

Naked viruses

A
  • Examples
    • Adeno
    • Pappilloma
    • parvo
    • circo
    • calici
    • picornavirus
  • Resistant to inactivation
18
Q

Genetic info storage

A
  • RNA viruses store genes in RNA
  • DNA viruses store genes in DNA
19
Q

Virus symmetry

Icosahedral

A
  • isometric viruses invariably icosahedrons
  • 12 corners, 30 edges, 20 faces (eachface an equilateral triange)
  • subunit repeats optimizes maximum volume
  • e.g. Herpes virus
20
Q

Virus symmetry

Helical

A
  • Nucleocapsid of some RNA viruses self-assembles into cylindrical structure
    • the helix
  • helical nucleocapsid of RNA viruses wound into coil enclosed in an envelope
  • e.g. Rabies virus
21
Q

Herpes virus immunogenicity

A
  • In the virus membrane
  • many vaccines based on glycoproteins on the virus envelope/membrane
22
Q

Rabies virus immunogenicity

A
  • glycoprotein G
    • one of the most immunogenic proteins
23
Q

Viral proteins (can code from 1-100)

Structureal proteins

A
  • Present in mature virions
  • Protect genomic nucleic acid enzymes
  • Provide receptor-binding sites to initiate infection
  • Facilitate penetration of genome into correct cell location
24
Q

Viral proteins

Non-structural proteins

A
  • Involved in
    • assembly
    • genome replication
    • modifying host innate immune response
    • polymerases must be part of mature virion
25
Q

International Committee on taxonomy of Viruses (ICTV)

A
  • established in 1966
  • in 2011
    • 94 families
    • 394 genera
    • 2480 virus species
26
Q

Hieracrchy of recognized viral taxa

A
  • Order
    • Mononegavirales
  • Family
    • Paramyxoviridae
  • Subfamily
    • Pneumovirinae
  • Genus
    • Pneumovirus
  • Species
    • Bovine respiratory syncytial virus (BRSV)
27
Q

Quantitative assays in clinical samples:

Physical assays

A
  • EM viral particles count
  • Hemagglutination
  • Antigen-capture ELISAs
  • Quantitative PCRs
28
Q

Quantitative assays in clinical samples:

Biological assays

A
  • Based on replicating virus particles that successfully initiate infection
    • viral plaque assays
    • end-point titration of infectivity
29
Q

Physical virus particles

vs

Infectious virus particles

(5 reasons)

A
  • Ratio varies between 100:1 and 10,000:1
    • assembly process inefficient
    • replication of RNA is error prone
    • poor stocking of virusis leading to inactivation
    • Inefectivity assays done in suboptimal in vivo systems
    • Host-cell defenses prevent infectious virus particles from completing replication process

*DNA viruses more effective, lower ratio of noninfectious to infectious

30
Q

Direct particle counts by electron microscopy

A
  • Counting of virus particles using electron microscope
  • Expensive, not routinely used
  • numbers must be compared to known conc latex beads for accuracy
    • dilution and volume are keys to calculate conc
  • mainly for firuses with unique geometic shape
    • adenoviruses
    • herpesviruses
    • picornaviruses
31
Q

Hemagglutination assays

A
  • Binding of some viruses to erythrocytes
    • produces lattice of cross-linked erythrocytes
  • Visually detected with Flu virus particles at and above 106/ml for 0.5% turkey or chicken RBCs
  • Sample diluted serially and RBCs are added
  • Hemagglutination (HA) titer
    • highest dilution inducing complete agglutination of RBCs
  • HA does not require intact/infectious virus
32
Q

Antigen-capture assay for Rotaviruses

A
  • 1) well coated with anti-rotavirus antibody
  • 2) rotavirus antigens captured by antibody
  • 3) specific anti-rotavirus enzyme conjugate binds to captured rotavirus antigens
  • 4) color develops

*not all viruses hemagglutinate: most pox viruses

*Physical technique

  • won’t tell us if infectious
33
Q

Quantitative PCR assays

A
  • Detect conc of target nucleic acid in viral sample
    • must previously treat sample with nucleases to degrade non-viral nucleic acids
    • Virus nucleic acid protected by capsid
  • Doesn’t detect empty capsids
  • Titers don’t strictly related to infectivity of virus sample
  • Real-time PCR
    • results observed in minutes
34
Q

Biological assay: Plaque assay

A
  • For viruses that produce discrete holes in cell monolayers
    • visually observed after staining with vital dyes
  • Immunohistochemical techniques used for non-cytopathic viruses
    • immunoperoxidase
  • Based on the fact that a single infectious virus particle is enough to establish and infection
    • plaque numbers follow one-hit kinetic curve
35
Q

Biological assay: Endpoint titration of virus stocks

A
  • Virus dilution that infects 50% of infected
    • embryonated eggs
    • tissue culture cells (inc tracheal rings)
    • experimental animals
  • Two methods
    • Reed-Muench
    • Spearman-Karber
    • LD50, EID50, TCID50, TRLD50
  • Not as accurate as plaque assay but easier to implement and automate

Microbio-virology (8 decks)

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