Veterinary virology Flashcards
(35 cards)
1
Q
Foot and mouth disease
A
- Loeffler and Frosch (1898) reported transmission in cattle of filterable and contagious agent
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
3
Q
Dr. Peyton Rous
A
- 1911 discovered first virus capable of inducing neoplasia
- Rous sarcoma virus
- nobel prize in medicine
4
Q
embryonated eggs
A
- used started 1931
- viruses could now be grown
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
6
Q
Chorioallantoic membrane inoculation
A
- Herpes simplex virus
- Pox virus
- Rous sarcoma virus
7
Q
Amniotic inoculation
A
- Influenza virus
- Mumps virus
8
Q
Yolk sac inoculation
A
- Herpes simplex virus
9
Q
Allantoic inoculation
A
- Influenza virus
- Mumps virus
- Newcastle disease virus
- Avian adenovirus
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
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
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
13
Q
Head of a dress-makers pin
A
- Large enough for five hundred million rhinoviruses (common cold)
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
15
Q
Eclipse period
A
- Time elapsed between virus penetration into host cell and production of new virus
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
International Committee on taxonomy of Viruses (ICTV)
* established in 1966
* in 2011
* 94 families
* 394 genera
* 2480 virus species
26
Hieracrchy of recognized viral taxa
* Order
* Mononegavirales
* Family
* Paramyxo**viridae**
* Subfamily
* Pneumovirinae
* Genus
* Pneumovirus
* Species
* Bovine respiratory syncytial virus (BRSV)
27
**Quantitative assays in clinical samples:**
**Physical assays**
* **EM viral particles count**
* **Hemagglutination**
* **Antigen-capture ELISAs**
* **Quantitative PCRs**
28
**Quantitative assays in clinical samples:**
**Biological assays**
* **Based on replicating virus particles that successfully initiate infection**
* **viral plaque assays**
* **end-point titration of infectivity**
29
Physical virus particles
vs
Infectious virus particles
(5 reasons)
* 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
Direct particle counts by electron microscopy
* 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
Hemagglutination assays
* 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
Antigen-capture assay for Rotaviruses
* 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
Quantitative PCR assays
* 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
Biological assay: Plaque assay
* 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
Biological assay: Endpoint titration of virus stocks
* 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**
