MICROBIOLOGY- How viruses cause disease Flashcards
1
Q
Who was responsible for principles of vaccination, pasteurisation and germ theory?
A
Louis pasteur
2
Q
Who invented the electron microscope?
A
Ruska and knoll in 1931
3
Q
What are viruses?
A
Simple micro organisms that are not cable of independent existence
4
Q
What do viruses need to be able to exist?
A
- Require a host cell to survive
- They enter the host cell and use the host cells energy and mechanism to replicate
- Once they have replicated they leave the host cell progeny
5
Q
Describe the basic viral structure
A
- Dna or RNA
- Capsid protein
- Lipoprotein envelope (only present in some viruses)
- Molecules of protein
6
Q
What is a single virus particle referred as?
A
Virion
7
Q
What are viruses classified by?
A
- The type of nucleic acid they carry (DNA vs RNA)
2. The presence or absence of an envelope
8
Q
Give the 5 steps involved in the viruses life cycle
A
- Attachment
- Entry
- Replication
- Assembly
- Release
9
Q
How can the virus enter the body?
A
Can be inhaled, ingested or injected
10
Q
What determines if a virus can enter the host cell
A
The viral tropism determines if a virus can attach and enter
11
Q
What does viral tropism mean?
A
It describes if the host cell is passive to the virion and allows it to enter and use its equipment
12
Q
Which cells can HIV attach to?
A
HIV can only attach to human cells that have a CD4 receptor
13
Q
Which cells can SARS-CoV-2 attach to?
A
SARS-CoV-2 can only attach to human cells with ACE-2 receptors
14
Q
What do we mean when we describe a host cell as passive?
A
It contains the whole range of components required by the virus for replication to be completed
15
Q
What step happens after attachment?
A
Entry into host cell
16
Q
If the virus attaches does it 100% enter the cell?
A
NO
Efficiency varies from <0.1% to 50%
17
Q
How do enveloped viruses enter a cell?
A
Enter by membrane fusion or endocytosis
18
Q
How do non enveloped viruses enter a cell?
A
Entry by endocytosis or penetration (direct injection)
19
Q
Talk through the basic stages of membrane of fusion
A
- Receptor binding
- Virus with host membrane fusion
- Release of vision content into host cytoplasm
20
Q
Give an example of a virus that enters via membrane fusion?
A
HIV
21
Q
After a virus enters the cell what does it need to do?
A
Replicate
22
Q
How does the virion start the replication process?
A
Once inside the host cell the virus will remove its capsid and exposes its genomes (Nucleic acid)
23
Q
Can the virus cell uncoat its capsid anywhere in the cell?
A
No
Site of uncoating is specific to the virus
May be cytoplasm or nuclear
24
Q
What process in host cells to viruses hijack?
A
The process of DNA replication and protein synthesis
25
Talk through the stages of protein synthesis in humans
1. Transcription of DNA into messenger RNA
2. Translation of mRNA into Amino
3. Translocation
26
What does the replication of viruses depend on?
Process depends on the type if nuclei acid the virus has
27
What is necessary to make viral protein
Viral mRNA
28
What does viral mRNA do?
1. Viral mRNA mimics host mRNA
2. Uses the host cell machinery to make viral proteins instead of host proteins
3. New virions are constructed from viral proteins
29
Which type of viruses can immediately start using host cells processes to translate their protein
Why?
Single stranded positive sense RNA viruses
e.g. hepatitis C
This is because their genome is already mRNA
30
Describe the genome of influenza
Single stranded negative sense RNA viruses
31
What must influenza first make before it can start replicating?
Must create mRNA
32
How does influenza create mRNA?
1. Carries its own enzyme (RNA dependent RNA polymerase)
2. This enzyme is used to create positive sense RNA (mRNA) through complementary base pairing
3. mRNA then used to translate proteins
33
Give examples of proteins needed to create new virions
1. Structural proteins
2. Enzymes (proteases) to chop up structural proteins into smaller building blocks
3. Enzymes needed to replication when they invade new host cells
34
After replicating what does a virus do?
Assemble
35
What happens in the assembly stage of a virus' life
All virus components are transported to a site of assembly and put together
36
Where are influenza virus proteins and new RNA assembled?
Assembles at the cell membrane which then forms a bud
37
After assembling all its proteins what does the virus then need to do?
Release itself from the host cell
38
State the 3 ways viruses can leave the host cell
1. Lysis
2. Exocytosis
3. Budding
39
What is lysis?
Cell splitting apart and dying allowing the virus to be released
40
What is exocytosis
When the host cell's transport system releases virions at surface
41
What is budding?
When the virion encloses themselves into host cell membrane
42
Give examples of different routes of infection a virus can take into the host cell
1. Mucosal contact
2. Parenteral (injection)
3. Respiratort droplet/ aerosol
4. Faecal oral
5. Direct contact (skin)
43
Give examples of viruses that spread through mucosal contact
1. HIV
| 2. Hepatitis B
44
Give examples of viruses that spread through parenteral (injection)
1. HIV
2. Hepatitis B
3. Hepatitis C
45
Give examples of viruses that spread through respiratory droplets / aerosol
1. Influenza
| 2. COVID 19
46
Give examples of viruses that spread through faecal oral
1. Hepatitis A
| 2. Norovirus
47
Give examples of viruses that spread through direct skin to skin contact
1. Human papillomavirus
2. Herpes
3. Simplex virus
48
What must be present from effective enter of a virus to occur?
1. There must be enough virus present (high infective dose)
2. Host cell must be accessible, susceptible and permissive
3. Host immune system must be inadequate or absent
49
How can viruses disrupt the host cells they infect
1. Disruptive cell fusion
2. Some inhibit host cell protein manufacture
3. Soem form inclusion bodies inside the cell
50
How does the respiratory syncytial virus disrupt the host cell
Produces multinucleate giant cells (called syncytia) which surround host cells and stick together
51
How can inhibition of host cell protein function harm host cells?
Causes reduced cell function and cell death
52
How can the formation of inclusion bodies inside the cell harm host cells?
Leads to the accumulation of protein / metabolites that damage the cell
53
How do we describe the extent of an infection?
1. Localised
| 2. Generalised
54
Describe localised infections
1. Typically shorter incubation period
2. Viruses remain at site of entry
3. May form focal lesions (eg warts)
4. May effect large areas of the same mucous membranes
55
Describe generalised infections
1. Longer incubation period
2. Initial phase of local replication near the site of entry
3. Generalised through the blood to lymph nodes or via nerves
56
How can generalised infections spread through the body?
1. Through blood to lymph nodes
2. Via nerves
This allows the virus to reach distant organs
57
List some target organs viruses can affect
1. Skin- rashes
2. Respiratory tract
3. Liver
4. Central nervous system
58
How can the skin be affected by a viral infection?
Viral replication can occur in the skin causing rashes
59
Which cells do hepatitis viruses affect
Hepatitis viruses have a tropism for hepatocytes (liver cells)
60
How do we describe illness duration
1. Acute
| 2. Chronic
61
Describe acute infections
1. Present quickly
2. Can be either mild with spontaneous recovery OR lead to rapid decline and death
3. Have to be easily transmitted or very infectious
62
What can acute illnesses result in?
1. Mild spontaneous recovery
OR
2. Rapid decline and death
63
Why do acute viruses need to be easily transmitted or very infectious?
As there shedding time is short
64
Describe chronic illness
1. Infection persists for long period time
2. The host immune system is unable to fully control the virus
3. Ongoing viral replication alongside immune response progressively damages host cells over time
65
What is latency
When the virus is existing but has not yet replicated or made progeny
66
How is a virus maintained during its latency period?
Maintained throughout normal host cell devisions and periodically reactivates
67
Give examples of viruses that have a latency period
1. herpes simplex (cold sores)
| 2. varicella zoster (shingles
68
How do latent viruses establish latency
Establish latency in neurones of the Dorsal root ganglia
69
Some viruses have the potential to induce M______ C______
Malignant change
70
How do some viruses induce malignant change
They disrupt the normal expression of host cell genes
71
What is Epstein Barr virus associated with?
Burkitts lymphoma
72
What malignant consequences can HPV have
Oral, cervical and penile cancer
73
What is HHV-8 associated with
Kaposis sarcoma in the immunosuppressed
74
List the 4 clinical stages of a virus infection
1. Incubation period
2. Prodromal period
3. Specific illness period
4. Recovery period
75
Describe the incubation period of a virus
1. Asymptomatic
| 2. Virus attaches and undergoing non production stages of life cycle
76
Describe the Prodromal period of a virus infection
1. Non specific manifestation
2. Non specific illnesss arises due to virus disseminating through the body
3. Leads to easy host immune response
77
Describe the specific illness period
1. Specific effects of the virus on target cells
| 2. Host immune systems immunogenic attack
78
What can we use to treat viruses?
Anti virals
79
How do antivirals work
They work by blocking different stages of a viruses lifestyle eg penetration, attachment , nucleic acid synthesis etc
80
Which antiviral affect viral attachment and entry
Blocked by:
1. Enfuviritide
2. Maraviroc
3. Docosonal
4. Palivizumab
81
Which antiviral affects virus penetration
Interferon alfa
82
Which antiviral affects viral uncoating
Blocked by amantadine
| rimantadine
83
Which antiviral affects nucleic acid synthesis
Blocked by:
1. NRTIs
2. NNRTIs
3. Acyclovir
4. Fosamet
84
Which antiviral affects late protein synths and processing
Protease inhibitors
85
Which antiviral affects viral release
Blocked by neuraminidase inhibitors
86
Why is it important to study viruses in dentistry
1. Transmission from patient to dentist
| 2. Virus may be underlying cause of the pathology toy see in a patient
87
How can viruses transmit from patient to dentist (and vice versa)
1. Respiratory transmission
2. Percutaneous injuries and blood splashes
3. Skin to mouth
4. Aerosal generating producing using high speed devices
88
Give some viruses that may be the underlying cause of the pathology you see in the patient
1. Herpes simplex
2. Measles
3. Oral cancer (HPV)
4. Kaposis sarcoma (HIV)
