Intro to virology and laboratory diagnosis of viral diseases Flashcards
(66 cards)
1
Q
Written record of a virus infection consists of a hieroglyph from Memphis, ancient Egypt’s depicting Siptah, a temple
priest showing a typical clinical sign of paralytic disease______
A
1400 BC
Poliomyelitis.
2
Q
Pharaoh Ramses V is believed to have died/succumbed to
A
1196 BC
smallpox
3
Q
1000 BC
Smallpox was endemic in China, in response, the practice of
_______ was developed.
A
variolation
4
Q
spread across Asia
* It was also practiced in Africa and the method varies from region to region.
A
VARIOLATION
5
Q
MAY 14, 1976
James Phipps (an 8-year-old) was vaccinated using ______
A
cowpox infected material of Sarah Nemes (milkmaid).
6
Q
- Genetic elements that can replicate only inside a living cell
- Dependent on the host cell for energy, metabolic intermediates, and protein synthesis
- All the functions of the host cell are being reserved for its own energy source, purpose, and energy use.
- Possess their own genomes (RNA and DNA)
- Do not grow in artificial media.
o Grow in cell culture, chick embryo, animals. - Small infectious units (measured in nanometer, about 20-300
nm in diameter)
A
OBLIGATE INTRACELLULAR PARASITES
7
Q
- is required (only
visualized in electron microscopy)
A
Electron microscopy
8
Q
smallest animal virus
A
Parvovirus
9
Q
largest animal virus
A
Poxvirus
10
Q
Virus types are very specific, and each has a limited number of hosts it can infect; this referred to as
A
viral tropism
11
Q
o Capsomeres (made up of protomers;
responsible for the shape of the virus)
o May or may not have an envelope made of lipid
derived from the host cell membrane.
▪ GLYCOPROTEIN SPIKES
o Envelope comes from the host cell
A
Protective Protein Coat
12
Q
made up of protomers;
responsible for the shape of the virus
A
Capsomeres
13
Q
May or may not have an envelope made of lipid derived from the host cell membrane.
A
GLYCOPROTEIN SPIKES
14
Q
are very susceptible to drying and
destruction in the environment, they typically are transmitted by direct contact, such as respiratory, sexual, or parenteral
contact.
- This prevents exposure to the environment and successful propagation of the viral agent to another susceptible host.
A
Enveloped viruses
15
Q
Viruses that do not have an envelope are often referred to as _____
- are very resistant to environmental factors.
o Because of their stability, they typically are transmitted by the fecal-oral route
A
“naked” viruses.
16
Q
- Protects the viral genome.
- Responsible for the tropism to specific cell types in naked
viruses - Composed of repeating structural subunits (capsomeres)
which associate to form a helical or icosahedral structure. - Irregularly shaped capsids have a helical form of icosahedral
structure - Icosahedral capsids, cubical with 20 flat
A
VIRAL CAPSID
17
Q
- Encloses the nucleocapsid
- During the infectious process, enveloped virion bud from the host cells cytoplasmic, nuclear, or endoplasmic reticulum
membrane and a protein of the membrane remains attached to the virion as the viral envelope. - Capsid covers the genome; lipid envelope encloses/covers
nucleocapsid.
A
LIPID ENVELOPE
18
Q
Inserted in the viral envelope are viral proteins such as _____
A
- hemagglutinin (receptor for the host cell; give entry to the host cell) (HA),
- neuramidase (enzyme used to lyse/to
facilitate the exit from the host cell), or glycoprotein spikes
19
Q
assist in the stabilization of attachment
for the lipid envelope and host cell for viral entry
A
Glycoprotein spikes
20
Q
may also be present between the envelope and nucleocapsid which may have enzymatic activities or biological function, e.g., inhibition of host-cell transcription (for the virus to survive inside the host cell)
A
Matrix protein
21
Q
- Component: PROTEIN
A
NAKED CAPSID
22
Q
Naked capsid environmentally stable to the following
A
- temperature
- acid
- proteases
- detergents
- drying
- released from cell by lysis
23
Q
- can dry out and retain infectivity
- can be spread easily (on fomites, from hand to hand, by dust,
by small droplets - can survive the adverse conditions of the gut
- can be resistant to detergents and poor sewage treatment
- antibody may be sufficient for immunoprotection (vaccination
to protect from naked viruses) - ex. Poliovirus (transmitted orally, but can be protected by
polio vax) - only released by cell lysis
A
NAKED CAPSID PROPERTIES
24
Q
ENVELOPE CAPSID COMPONENT
A
- Membrane lipids
- Proteins
- Glycoproteins
25
Envelop capsid Environmentally LIABLE – disrupted by the following:
- Acid
- Detergents
- Drying and heat
26
Mode of entry: blood transfusion – so gastrointestinal is not
affected.
* modifies cell membrane during replication.
* released by budding and cell lysis.
* must stay wet (para di mamatay)
* spreads in large droplets, secretion, organ transplants, and
blood transfusions
* cannot survive the gastrointestinal tract.
* Does not need to kill the cell to spread.
* may need antibody and cell-mediated immune response for
protection and control.
* Elicits hypersensitivity and inflammation to cause immunopathogenesis.
* Viruses can produce neoantigens.
Envelope capsid properties
27
* Icosahedral structure (cubic)
* Helical structure
* Complex structure (Poxviridae)
NUCLEOCAPSID STRUCTURES
28
A subunit of the capsid, and outer covering of the protein that
protects the genetic material of the virus
CAPSOMERES
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icosahedron with 12 vertices
(pentones- always 12) and 20 faces
(hexons/heptons- varies among the virus)
Icosahedral
30
icosahedron with 12 vertices
(pentones- always 12) and 20 faces
(hexons/heptons- varies among the virus)
Icosahedral
31
protomers not grouped in
capsomeres but bound to form a ribbon-like structure.
Helical
32
viruses that do not fit the first two
groups: exhibited by poxvirus and rhabdovirus
Complex
33
protect against physical, chemical, and
enzymatic damage and are multiply redundant, with only a
few protein subunits repeated.
Capsomeres
34
introduce the enclosed viral genome into the host cell by adsorbing tardily to host cell surfaces.
Capsid
35
1. Adsorption (recognition of the host cell and attachment to
the host cell)
2. Penetration (host cell membrane)
3. Uncoating (envelope and capsid)
4. Synthetic phase (enter nucleus of the host cell)
5. Viral assembly (assemble proteins and genomes; undergo
6. Release (budding or cell lysis)
VIRAL MULTIPLICATION CYCLE (INFECTIOUS CYCLE)
36
It involves recognition of a suitable host cell and specific binding between viral capsid proteins (often the glycoprotein
spikes) and the carbohydrate receptor of the host cell.
* Each type of virus specifically recognizes and attaches to a specific type of host cell, allowing infection of some tissues
but not others (viral tropism, as described previously).
ATTACHMENT (ADSORPTION)
37
* The process by which viruses enter the host cell
* One mechanism of penetration involves fusion of the viral envelope with the host cell membrane.
* Detection of syncytia can be used to determine the presence of virus in cell cultures or stained smears of clinical specimens. Other mechanisms of viral penetration include
- phagocytosis by host cells (endocytosis) or injection of viral nucleic acids into the host cell.
PENETRATION (VIRAL ENTRY)
38
* Occurs once the virus has been internalized.
* It is the process by which the capsid is removed; this may be by degradation of viral enzymes or host enzymes or by
simple dissociation.
- necessary to release the viral genome for
delivery of the viral DNA or RNA to its intracellular site of replication in the nucleus or cytoplasm
UNCOATING
39
* Involves the production of nucleic acids and protein polymers.
* Viral transcription leads to the synthesis of messenger RNA (mRNA), which encodes early and late viral proteins.
* Early proteins are nonstructural elements, such as enzymes, and late proteins are structural components.
* Rapid identification of virus in a cell culture can be accomplished by detecting early viral proteins in infected cells using immunofluorescent staining techniques.
MACROMOLECULES SYNTHESIS
40
* Structural proteins, genomes and in some cases, viral enzymes are assembled into virus particles
* Envelopes are acquired during viral budding from the host cell membrane
* Nuclear endoplasmic reticulum and cytoplasmic membranes are common areas for budding
* Acquisition of envelope is the final step in viral assembly
VIRAL ASSEMBLY
41
* Occurs after cell lysis or by virus particle budding from cytoplasmic membranes
* Release by budding may not result in rapid host cell death unlike cell lysis
* Detection of cell lysis in cell culture – detection of virus
RELEASE OF INTACT VIRUS PARTICLES
42
Influenza virus which are released by budding can be detected by
hemadsorption
43
RBCs added to the culture
medium but not to_____
Uninfected cells
44
1 host cell
1000 particles
45
may be due to errors of mutations or
virus assembly/packaging of components that occur during the infectious cycle
Non-infectious particles
46
6 orders
name ending in -virales
47
87 families
viridae
48
19 subfamilies
virinae
49
348 genera
-virus
50
o Type of nucleic acid
o Symmetry and shape of the capsid
o Presence or absence of envelope (naked or envelope)
o Size of the virus particle
Based on 4 major properties of viruses
51
- With advances in molecular techniques, sequencing of viral nucleic acids, including DNA or RNA genomes, has become
a routine procedure in clinical research setting and clinical diagnostic laboratory.
- But due to genetic instability of viral genomes, DNA/RNA sequencing is limited to provide evidence for species
relationship, epidemiologic comparison of isolates and genotype information which may direct antiviral therapies.
- Clinical virologists currently categorize viruses first as DNA or RNA, then by family and common names based on nucleic
acid sequence and phylogenic relatedness.
VIRAL TAXONOMY
52
o All are DS DNA except
PARVOVIRUS
53
All are icosahedral except
POXVIRUS
54
All are enveloped except
- PAPOVAVIRUS
- ADENOVIRUS
- PARVOVIRUS
55
All multiply in nucleus except
POXVIRUS
56
All are SS RNA except
REOVIRUS
57
All are enveloped except PCR
- PICORNAVIRUS
- CALCIVIRUS
- REOVIRUS
58
All are non-segmented except ROBA
- REOVIRUS
- ORTHOMYXOVIRUS
- BUNYAVIRUS
- ARENAVIRUS
59
Generally helical except the
POSITIVE SENSE RNA VIRUSES
60
- Calcivirus
- Picornavirus
- Flavivirus
- Togavirus
- Coronavirus
- Retrovirus
- icosahedral
POSITIVE SENSE
61
- Paramyxovirus
- Orthomyxovirus
- Filovirus
- Rhabdovirus
- Bunyavirus
- Arenavirus
– helical
NEGATIVE SENSE
62
What was the first virus to be discovered?
a. Smallpox
b. Poliovirus
c. Both the given options
d. Neither
b. Poliovirus
63
The following are general characteristics of virus, EXCEPT:
a. Obligate intracellular organism
b. Measures 20-300 nm
c. Grow in artificial culture media
d. Possess their own genomes
c. Grow in artificial culture media
64
Which of the following viral components assist in the stabilization of attachment for the lipid envelope and host cell for viral entry?
a. Nucleocapsid
b. Matrix protein
c. Viral genomes
d. Glycoprotein spikes
d. Glycoprotein spikes
65
Fusion of the viral envelope with the host cell membrane occurs during which phase of viral
replication?
a. Attachment
b. Penetration
c. Uncoating
d. Assembly
b. Penetration
66
The viral classification is based on which of the following viral options?
a. Type of nucleic acid
b. Size of the virus
c. Symmetry and shape of the capsid
d. All of the given options
d. All of the given options
