MFD2

Question 1

Prions diseases are caused by proteins whose misfolding is infectious. Through the following process:

Answer 1

(A) The protein undergoes a rare conformational change to give an abnormally folded prion form.
(B) The abnormal form causes the conversion of normal proteins in the hostʹs brain into a misfolded prion form (‘evangelistic’ behaviour)
(C) The prions aggregate into amyloid Fibrils by stacking beta sheets, which disrupt brain cell function, causing neurodegenerative disorder.
The fibres are protease resistant and resistant to autoclaving for long periods

Question 2

1) What is a prion?
2) What does it form?
3) How does it spread?
4) What does it cause?

Answer 2

1) Misfolded proteins which form aggregates: proteinaceous infectious particles
2) Spread from cell to cell and in between individuals via contaminated food, blood and surgical instruments (and are therefore ‘infectious’)
3) Cause neurodegenerative diseases e.g. Creutzfeldt-Jakob Disease (CJD)-transmissible spongiform encephalopathies (TSEs)

Question 3

Prion disease in man

1) How can you get it? (3)
2) What does it do to tissue? What happens to neuronal function?
3) Does it induce an inflammatory response?
4) Describe onset of symptoms and is it fatal?

Answer 3

1) Spontaneous (sporadic CJD), inherited (familial CJD), acquired (vCJD, Kuru- cannabilism)
2) forms insoluble aggregates = plaques,
, neuronal dusyfunction and tissu death= holes , hence name spongiform
3) no
4) fast, yes

Question 4

1) How common is sporadic CJD?
2) What type of disease is it?
3) What else can other misfolded proteins (e.g.amyloid proteins) cause?

Answer 4

1) 1-2 percent
2) prion disease
3) contribute to non-infective tissue degenerative disorders e.g. Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, atherosclerosis, type 2 diabetes.

Question 5

Are all misfolded proteins prions?

Answer 5

no only the ones that go undetected

Question 6

How are viruses classifed?

Answer 6

into those that do and don’t have an envelope

Question 7

What do non-enveloped viruses consist of?

Answer 7

a nucleocapsid containing the viral genome.

Question 8

What do enveloped viruses consist of?

Answer 8

1) nucleocapsid containing the viral genome.
2) lipid bilayer
3) envelope proteins
(in order where 1 is most inner layer)

Question 9

What do viral genomes encode for?

Answer 9

1) viral structural proteins
2) proteins that interact with the host ( proteases, DNA/RNA polymerase, reverse transcriptase, immune system inhibitors)

Question 10

What structures can viral genomes have?

Answer 10

1. RNA single stranded
2. RNA double stranded
3. DNA single stranded
4. DNA double stranded

Question 11

What 3 forms can viral genomes have?

Answer 11

linear, circular or segmented

Question 12

What is only present in viruses and used to identify them?

Answer 12

Reverse transcriptase is only present in viruses and used to identify them.

Question 13

Viruses have many different nucleic acid structures and hence a variety of _____1____.
Most viruses that cause human disease are either ______2___ (e.g. herpes viruses) or _____3_____ (e.g. retroviruses such as HIV). They have different ____4____.

Answer 13

1) replication mechanisms
2) double stranded DNA
3) single stranded RNA
4) life cycles.

Question 14

Describe the life cycle of a double stranded DNA genome virus:

Answer 14

1. DNA enters cell
2. DNAreplicated
3. transciption into RNA occurs
4. RNA is translated into coat proteins
5. Assembly of progeny virus particles ( the coat protein + its DNA) and cell lysis

Question 15

Describe the life cycle of a single stranded RNA genome retrovirus:

Answer 15

1. Enters into host cell and loss of envelope
2. Reverse transcriptase makes DNA/RNA hybrid then DNA/DNA double helix
3. Integretion of DNA copy into host chromosome
4. Host cell chromosome now with integrated viral DNA is transcribed= many RNA copies
5. RNA is translated = coat proteins, envelope proteins and reverse transciptase
6. Assembled into many , infectious virus particles

Question 16

Why is it important to understand viral genome?

Answer 16

classifies them and indicates their properties

Question 17

Some viruses directly affect oral health after infection the mouth and others ….
2) Why is this important to dentists?

Answer 17

the mouth without directly causing oral disease (following release from other tissues)
2) cross-infection control

Question 18

Give oral symptoms of measles, mumps and rubella

Answer 18

• Measles (rash-Koplik’s spots- red spors on oral mucosa, fever, cough, conjunctivitis, coryza (stuffy nose))
• Mumps (salivary gland inflammation/ swelling of the jaws and neck- somes causes ear ache and trismus (spasm of mm of mastication)
• Rubella (rash)

Question 19

Viral infections of the mouth 
- give oral symptoms:
• Hand, foot and mouth disease
• Human herpes viruses (HHV)
• Human papilloma viruses (HPV)]

Answer 19

• Hand, foot and mouth disease –enterovirus (coxsackie A virus) which causes oral blisters (yellow ulcers with red halos-labial and buccal mucosas) (not the same as foot and mouth disease in cattle)
• Human herpes viruses (HHV)-(lesions (small, painful, fluid-filled blisters ooze and ulcerate) in gums, palate, tongue , lip and facial area) large class of structurally related viruses
• Human papilloma viruses (HPV)- oral lesionscan cause Oral cancer in men,

Question 20

Give other name of each member of the human herpes virus family:

1) HHV1
2) HHV3
3) HHV4
4) HHV5
5) HHV8

Answer 20

1) Herpes simplex virus 1
2) Varicella-zoster virus
3) Epstein-Barr virus
4) Cytomegalovirus
5) N/A

Question 21

Give diseases caused by each member of the human herpes virus family:

1) HHV1
2) HHV3
3) HHV4
4) HHV5
5) HHV8

Answer 21

1) Fever blisters (cold sores)
2) Chicken pox/ shingles
3) Glandular fever, hairy leukoplakia, B-cell lymphoma
4) Congenital defects/ pneumonia in AIDS
5) Kaposi’s sarcoma

Question 22

HHV1 (HSV-1)
• Infects ____1____l cells (in the ______2____) and ____3____ cells
• Exhibits ___4___
• Causes ____5___ on initial infection, then ___6__ and ____7___ on reactivation
• Transmission during childhood contact via _____8_____

Answer 22

HHV1 (HSV-1)
• Infects (1)epithelial cells ((2)oral mucosa) and (3)neuronal cells
• Exhibits (4) latency
• Causes (5) stomatitis on initial infection, then (6) fever and (7) blisters on reactivation
• Transmission during childhood contact via (8) saliva

Question 23

HHV3 (varicella zoster virus, VZV)
• Very contagious-transmitted via ___1–___ and ___2___-
• Can cause___3___in the __4___mucosa
• Primary disease is chicken pox-can be reactivated as shingles
• Shingles appears in skin along ____5___ usual on trunk but can be facial (30% of shingles cases)

Answer 23

Very contagious-transmitted via (1) aerosols and (2)direct contact  
Can cause (3) blisters in the oral (4)mucosa • Primary disease is chicken pox-can be reactivated as shingles 
• Shingles appears in skin along (5)track of nerve usual on trunk but can be facial (30% of shingles cases)

Question 24

Human papilloma virus
Over 150 types on HPV-some cause pathology, others are part of the virome of the skin
• Some cause ___1___ (papillomas) of the genital or oral mucosa
• Some types of HPV associated with papillomas (e.g. HPV-16 and HPV-18) are also associated with cancers e.g. cervical cancer/oral cancer
• HPV-13 and HPV-32 cause focal epithelial hyperplasia and are restricted to the oral cavity

Answer 24

Human papilloma virus
Over 150 types on HPV-some cause pathology, others are part of the virome of the skin • Some cause (1) warts (papillomas) of the genital or oral mucosa
• Some types of HPV associated with papillomas (e.g. HPV-16 and HPV-18) are also associated with cancers e.g. cervical cancer/oral cancer
• HPV-13 and HPV-32 cause focal epithelial hyperplasia and are restricted to the oral cavity

Question 25

What are papillomas?

Answer 25

warts

Question 26

1) Why don’t we vaccinate against chicken pox?
2) what healthcare measures are in place to reduce the incidence of HPV infection and how might these be made even more effective?

Answer 26

1) It provides immunity to other viruses

2) 12-13 year old girls receive vaccinations against HPV and cervical screen when middle aged.

Question 27

Necrotising ulcerative gingivitis has these possible causes:

2) it is very …
3) Treatment:

Answer 27

1) Associated with stress, mixed bacterial infection, smoking and HPV
2) Very painful
3) Plaque control (chlorhexidine, ultrasonics, oral hygiene instruction) – Metronidazole

Question 28

What are the different ways of diagnosis of viral infections:

Answer 28

1. Clinical appearance
2. Laboratory tests: immunoassay (ELISA) & sero-conversion (detect antibodies)
3. Microbiology: viral culture
4. Histology of tissues: biopsy (cellular morphology and immunohistochemistry)

Question 29

1) How do antiviral drugs work?

2) e.g.sss

Answer 29

1) antiviral drugs do not destroy their target pathogen; instead they inhibit their development.
2) e.g. nucleoside analogues: acyclovir and azidothymidine (AZT)