Virus Classification - DNA, RNA Flashcards
Please do not distribute notes
1
Q
Define obligate intracellular parasite
A
Growth and reproduction of this organism can only occur inside of host cells
2
Q
A virus is an Obligate intracellular parasite (T/F)
A
True
3
Q
What is viral genetic information surrounded by?
A
Protein in the form of protein capsid
4
Q
Range of virus sizes
A
20-300nm
5
Q
Viruses have a receptor - binding protein for attaching to cells (T/F)
A
True
6
Q
Viruses are not host/organ specific (T/F)
A
False; viruses have host and organ specificity i.e. they can target specific organs in a host or specific hosts
7
Q
Viruses cannot pass through filters (T/F)
A
False; viruses are ultramicroscopic unlike bacteria which can be filtered
8
Q
Which microscope is used to observe viruses
A
Electron microscope
9
Q
List 4 main components of a virus structure
A
Nucleic acid genome, protein capsid, lipid envelope, envelope proteins
10
Q
Classifications of viruses based on nucleic acids
A
DNA viruses
RNA viruses
11
Q
Herpes, Pox, Papovavirus, Parvovirus, Adenovirus, Bacteriophage
- These are DNA or RNA viruses?
A
DNA viruses
12
Q
Herpes virus types
A
Human herpes virus 1 - Herpes Simplex Virus 1
“ “ “ 2 - HSV2
“ “ “ 3 - Varicella zoster virus - chicken pox
Human “ “ 4 - Epstein-Barr virus
Human “ “ 5 - Cytomegalovirus
“ “ “ 6
“ “ “ 7
“ “ “ 8 - Kaposi sarcoma associated herpes virus
13
Q
Pox virus
A
Smallpox virus
14
Q
Are antibiotics used when treating patients with viruses?
A
No; only if patient is in ICU and has secondary bacterial infection
15
Q
Icosahedral - define
A
A polyhedron with 20 faces
16
Q
Complex viral structure - define
A
Combination of icosahedral and helical shape and may have a complex outer wall or head-tail morphology e.g. bacteriophage
17
Q
Enveloped viruses are only double stranded (T/F)
A
True
18
Q
Name an icosahedral, ds, enveloped DNA virus
A
Herpes
19
Q
Name a complex, ds, enveloped DNA virus
A
Pox
20
Q
Naked viruses have no lipid envelope (T/F)
A
True
21
Q
The structure of naked viruses consists of both complex and icosahedral (T/F)
A
False; all are icosahedral
22
Q
Naked viruses are only single stranded (T/F)
A
False, both single and double stranded
23
Q
Name an icosahedral, ss, naked DNA virus
A
Parvovirus
24
Q
Name an icosahedral, ds, naked DNA virus
A
Papovavirus, Adenovirus
25
+ssRNA vs -ssRNA
a positive-sense RNA virus doesn't need a polymerase (enzyme) and so the virus is able to make message for the DNA right away without a vital enzyme! It can make viral DNA immediately.
-ssRNA must be converted to +ssRNA before translation to make proteins because -ssRNA is complementary to mRNA.
26
ssRNA is split into +ve stranded and -ve stranded types of viruses (T/F)
True
27
Name a +ve stranded, ss, naked RNA virus
Picornavirus, Calicivirus
28
Name a +ve stranded, ss, enveloped RNA virus
Togavirus, Flavivirus, Coronavirus, Retrovirus
29
Name a virus that can be either +ve or -ve stranded but single stranded
Arenavirus
30
Name a -ve stranded, ss, enveloped RNA virus
Bunyavirus, Orthmyxovirus, Paramyxovirus, Rhabdovirus
31
Name a ds, naked RNA virus
Reovirus
32
Picorna, Calici, Toga, Flavi, Reovirus all are icosahedral and the rest of RNA viruses are helical (T/F)
True
33
Structure of naked capsid virus
DNA/RNA + Structural proteins +/- enzymes and nucleic acid binding proteins = nucleocapsid
34
Structure of enveloped virus
Nucleocapsid + Glycoproteins and membrane
35
Viruses have two protective layers (T/F)
True - protein and lipid layers
36
Function of capsid/ protein coat
-- Protects nucleic acid from inactivation
| – Helps to introduce viral genome into host cell
37
Capsid is composed of
Capsomers
38
Capsomer is composed of
Repeating protein subunits blocks that make up the capsid.
39
Protomers are ?
The polypeptide chains which make up the capsomers
40
Icosahedral capsid symmetry
12 Corners & 20 Sides
- Two types of Capsomers form the Capsid
- Pentagonal capsomers form the vertices
- Hexagonal capsomers form the sides
41
Capsid symmetry - helical
Capsomers & nucleic acid are wound together to form a helical or spiral tube
42
Complex capsid symmetry
The overall shape of virus is quite variable , but mostly they are spherical
43
Protein subunits seen as projecting spikes on the
| surface of envelope are called
Peplomers
44
A virus may have more than one type of peplomer (T/F)
True
45
Example of virus with more than one type of peplomer
Influenza virus
46
Properties of peplomers
- Confers chemical , antigenic & biological properties.
| - Susceptible to lipid solvents
47
Viral replication steps
```
1) Recognition of host cell
↓
2) Attachment
↓
3) Penetration
↓
4)Uncoating
↓
5) Transcription ( RNA-dependent RNA transcriptase is carried with virus for -sense b/c needs to be converted to +sense mRNA to form proteins in nucleus)
↓
6) Protien synthesis
↓
7) Replication
↓
8) Assembly
↓
9) Lysis & release
```
48
When is the eclipse phase of viral replication?
From the stage of penetration till the appearance of mature daughter virions
The virions cannot be detected inside the host cell
49
Duration of eclipse phase
3-12 hours
50
Viruses can grow on chemically defined media (T/F)
False
51
Types of Arboviruses
Alpha virus
- Chikungunya
Flaviviridae
--> Mosquito transmission
Hemorrhagic group
- Yellow fever, Dengue
Rhabdovirus
- Rabies virus
52
In vivo vs in vitro
In vivo - lab bred animals, embryonic bird tissue
| In vitro - cell/tissue culture
53
Why do we culture viruses?
- Isolate + ID viruses
- Research on viral structure, replication effects on host cell
- Prepare virus for vaccine production
54
How does animal culture work?
Animals are inoculated with the virus and observed for effects which can include death
Virus is isolated and purified from the tissue of these animals.
55
```
Match virus to animal inoculation (rabbit, monkey, white mouse, baby white mouse)
HSV
Rabies virus
Dengue virus
Polio virus
```
HSV - rabbit
Rabies virus - white mouse
Dengue virus - baby white mouse
Polio virus - monkey
Animal inoculation isn't done much anymore - difficulty in choosing animals + care
56
Which viruses is CAM (chorioallantoic membrane) used for?
Herpes simplexx virus, Pox virus
57
Which viruses is Amniotic cavity used for?
Inoculation is mainly done for primary isolation of influenza virus and the mumps virus.
58
What is Amniotic cavity used for?
10 day old embryo
| Inoculation is mainly done for production of vaccine of influenza virus, yellow fever, rabies.
59
Which viruses is the yolk sac used for?
3-8 day old embryo
| e.g.: Chlamydiae & Ricketssia
60
Which viruses is the intraembryonal area used for?
Japanese B encephalitis virus
61
Pros and cons of inoculating embryonated eggs
Pros
They are free from contaminating bacteria and many latent viruses.
Specific and non specific factors of defense are not involved in embryonated eggs
Cost effective and maintenance is much easier.
Cons
Site of inoculation for varies with different virus. That is, each virus have different sites for their growth and replication.
Primary cultures usually have a limited life span. When cells in a primary culture undergo mitosis and a sufficient density of cells is produced, cells come in contact with other cells.
When this cell-to-cell-contact occurs, mitosis is triggered to stop. This is called contact inhibition and it prevents the density of the cells from becoming too high.
To prevent contact inhibition, cells from the primary cell culture must be transferred to another vessel with fresh growth medium (secondary cell culture).
62
Purpose of cell cultures in cultivating viruses
For isolation , Neutralization , Production of Antigen for
| serological assay
63
Types of cell cultures
Primary culture :- Made by dispersing cells from freshly
removed host tissues , unable to grow for more than a few passage/sub cultures.
eg : - Rhesus monkey kidney cell & Human
amnion cell culture .
Secondary / Diploid culture :- Diploid cell lines up to 50
passage/ sub cultures but retain their normal chromosome pattern.
eg Human embryonic lung cell culture.
Continuous cell line / Heteroploid cell culture :- Capable of prolonged , infinite growth , derived from cancerous cells ,
grow faster with haploid chromosomes.
eg HeLa cell from cancer of cervix , Hep-2 ( epithelioma of larynx cell ) .
64
Pros and cons of cell cultures
Pros
Relative ease, broad spectrum, cheaper and sensitivity
Cons
Need trained technicians 24/7
Most hospital labs don't isolate and ID viruses
65
What are Cytopathic effects?
Cytopathic effects (CPEs) are distinct observable cell abnormalities due to viral infection.
66
```
Which of the following is NOT a cytopathic effect?
transformation
cell fusion
mononucleated cell
inclusion bodies
```
Mononucleated cell
67
Cell abnormalities resulting from a viral infection are called _____________.
Cytopathic effects
68
CPEs can include what events in a viral cell?
CPEs can include:
- adherence of red blood cells to the surface of a virus (hemadsorption)
- inhibition of viral reproduction (interference)
- changes in cell shape from flat to round, shrinkage of the nucleus (transformation)
- vacuoles in the cytoplasm, fusion of cytoplasmic membranes and the formation of multinucleated syncytia,
- inclusion bodies in the nucleus or cytoplasm, and
- complete cell lysis
69
During viral replication, what can be produced?
Inclusion bodies
70
Inclusion bodies become larger tan viruses and have an affinity for dyes (T/F)
True
71
Intra vs inter
Intra - inside
| Inter - between
72
Herpes virus , Poliovirus , Echovirus , Coxsackie virus , Influenza virus , Rubella virus , CMV all have inclusion bodies present where in a viral cell?
Nucleus
73
Herpes virus , Poliovirus , Echovirus , Coxsackie virus , Influenza virus , Rubella virus , CMV all have inclusion bodies present where in a viral cell?
Nucleus; if the virus is made of RNA then it affects cyotplasm and if DNA then nucleus, this is because inclusion bodies form during viral replication
74
Herpes virus has inclusion bodies where in a viral cell?
Nucleus
75
Influenza virus has inclusion bodies where in a viral cell?
Nucleus
76
Poxvirus , Rabies virus has inclusion bodies where in a viral cell?
Cytoplasm
77
Adeno virus & Measles virus has inclusion bodies where in a viral cell?
Both ( nucleus&cytoplasm)
78
Cowdry bodies - define
Eosinophilic nuclear inclusions made up of nucleic acid and proteins
79
Cowdry bodies - define
Eosinophilic nuclear inclusions in viruses, composed of nucleic acid and protein seen in cells infected with Herpes simplex virus
Nuclear inclusions - Abnormal substances in the nuclei
80
Most viruses are acidophilic, few basophilic e.g. ______.
Adenovirus
81
Intra nuclear inclusions consist of what types of inclusions?
Cowdry type A and cowdry type B
82
Cowdry type A is found in?
Yellow fever - Variable size, granular appearance
83
Cowdry type B is found in?
Polio) - Circumscribed (confined to one area) , multiple
84
Match the Intra cytoplasmic inclusions to the viruses (Small pox, adenovirus, rabies, measles)
Guarnieri bodies
Negri bodies
Both
```
Guarnieri bodies ( Small pox )
Negri bodies ( Rabies )
Both ( Measles , Adenovirus )
```
85
Bacteriophage - define
Viruses that infect bacteria
86
Shape of head and sheath of bacteriophage
Capsid ( head ) is polyhedral ,
| Sheath is helical
87
Bacteriophages can pass through bacterial filters (T/F)
True
88
Bacteriophages have low host specificity
False; high host specificity
89
Common habitat of bacteriophages
Intestinal tract of animals
90
Bacteriophage purpose
Bacterial identification; not viral ID
91
Phage typing - explain
- Classify strains within species of bacteria, each strain is sensitive to a small number of different phages
- Leaves patterns of growth and lysis that can determine the strain.
92
Phage typing - purpose
Trace the source of outbreaks of infections.
---The viruses that infect bacteria are called bacteriophages and some of these can only infect a single strain of bacteria.
Act as carrier of genes from one bacterium to another
Utilized to study Host - Parasite Relationships
93
Hemadsorption is used for?
| Hemadsorption process
hemadsorption : adherence of red blood cells to the surface of something (as a virus or cell)
Testing presence of Influenza
Influenza virus - Orthomyxoviridae
- Has diff antigens on surface, one of which is HA (Hemagglutinin). Drop erythrocytes of guinea pig onto viral cell culture of Influenza to see if it will be absorbed by the cell surface antigens.
94
Direct Immunofluorescence Assay (DIA)
- Antibody tagged fluorescent dye on infected cells and view on fluorescent microscope
95
ImmunoPeroxidase Staining
- Immunoperoxidase staining the cells coated for viral antigens
immune protein called an antibody will attach itself to certain substances, called antigens, that are on or in the cell.
an antibody is joined to an enzyme, peroxidase, that catalyses a reaction in which the protein is specifically stained brown.
