Morphology and biology of viruses Flashcards
(25 cards)
1
Q
What are the criteria for virus classification?
A
- Type of genome (DNA/ RNA, ds/ss)
- Replication strategy
- Structure and size of virion - envelope?
- Host rage
- Tissue tropism
- Pathogenicity
- Mode of transmission
- Physiochemical properties
- Antigenic properties
2
Q
What is the structure of herpes?
A
- icosahedral nucleocapsid
- dsDNA linear
- Enveloped
3
Q
What is the structure of HIV?
A
- Enveloped
- Viral gp120 and gp41
- 2 copies of RNA
- Reverse transcriptase
- Integrase
- Protease
4
Q
What is the structure of hep A?
A
- Picornaviridae family
- No envelope
- Icosahedral
- ssRNA
- +ve sense
5
Q
How is hep A transmitted?
A
- Children and young adults
- Mainly foecal-oral
- possible sexual but unlikely
6
Q
What is the structure of hep B?
A
- Hepadnaviridae family
- Enveloped
- 42nm
- Icosahedral
- Circular DNA, partially ds
- Complete virus and incomplete particles
- Tubular filaments and spherical
7
Q
How is hep B transmitted?
A
- Young babies - toddlers
- Percutaneous - needles
- Perinatal
- Sexual
- Found in body fluids
8
Q
What is the structure of hep C?
A
- Flaviviridae family
- Enveloped
- Icosahedral
- ssRNA
- Non-structral protein 1
9
Q
What are some risk factors for hep C?
A
- IV drug abuse
- Body piercings and tattoos
- Needle stick injury
- mother to baby
- sexual transmission
10
Q
How is Hep C transmitted?
A
- Any age
- Percutaneous
- possible for perinatal and sex
11
Q
What is norovirus?
A
- Common cause of infectious gastroenteritis -> diarrhoea
- Caliciviridae
- icosahedral
- non-enveloped
- ssRNA
12
Q
What is rotavirus?
A
- Reoviridae
- dsRNA - 11 segments
- Non-enveloped
- icosahedral
- Causes fever, vomiting, diarrhoea, abdominal pain
- Structural proteins - VP1-7
- non-structural - NSP1-6
13
Q
How does rotavirus replicate?
A
- Binds to cell with VP7 and VP4 - enters by endocytosis
- Uncoats
- Has VP6 channel, allowing dsRNA to move in and out of virus
- VP1-3 allow transcripton in virus, then sends it to ribosomes of cell to be translated - makes single shelled particles
- These double layered then go to the ER, where they acquire outer shell
- Then get released
14
Q
What is measles virus?
A
- Enveloped
- ssRNA
- -ve sense
- Paramyxoviridae
- Pleomorphic
Causes
- fever cough, runny nose, red eyes, sore throat
- White spots in mouth
- Rash on face, spreads downwards
15
Q
How is measles transmitted?
A
- highly contagious
- Transmitted by coughing/ sneezing
16
Q
What is mumps virus?
A
- Paramyxovirus
- Pleomorphic
- Enveloped
- Helical nucleocapsid
- ssRNA linear genome
Causes
- fever, headache, muscle aches, tiredness, loss of appetite, swollen and tender salivary glands on both sides
Transmitted
- Droplets
17
Q
What is rubella virus?
A
- Acute viral disease causing fever and rash
- Spread through coughing and sneezing
- Togavirus family
- enveloped
- ssRNA
- icosahedral
18
Q
What is congenital rubella?
A
- Birth defects if acquired by pregnant woman
- Deafness, cataracts, heart defects, foetal brain damage, liver and spleen damage
19
Q
What is adenovirus?
A
- Adenoviridae
- No envelope
- Icosahedral
- dsDNA, linear
- Respiratory illness, or gastrenteritis, conjunctivitis, cystitis, rash
20
Q
What is papillomavirus?
A
- no envelope
- Icosahedral
- circular dsDNA
- Papovaviridae
- Different serotypes - some cause infections in the genital tract
- Cervical cancer
21
Q
What is parvovirus?
A
non-enveloped
- ssDNA
- Nucleocapsid icosahedral
- Pavovirus B19 can attach to erythrocyte progenitor cells and inhibit erythropoeisis
- shortens life span of RBCs
- mostly in children
- Slapped cheek rash
- may have low-grade fever
22
Q
What is the structure of influenza?
A
- Orthomixoviridae
- Enveloped
- Has HA, NA, and an ion channel (matrix protein 2, M2)
- Also M1 protein associated with ribonucleoprotein in middle, and the envelope
23
Q
What are the influenza subtypes?
A
- A - most serious. Animals and birds. Genetic cross-over leads to pandemic
- B - humans - minor outbreaks but not pandemic
- C - mild, only affects humans. Endemic, symptoms similar to the common cold
24
Q
What is the replication cycle of influenza?
A
- Virus binds to sialic acid via HA - endocytosis
- Virus envelope fuses with the endosome, low pH triggers uncoating
- Viral nucleic acid capsid contains RNA and is released into cytoplasm
- Viral RNA is copied in nucleus - -ve sense so must be transcribed twice
- Once transcribed, mRNA is synthesised and translated in the cytoplasm
- Early viral proteins are transported back into the nucleus as they are needed for transcription and replication (telomerase and ribosomes)
- RNA segments are assembled in the nuclear capsid
- Assembly and budding of new virions out of the plasma membrane
25
What is the current strategy for dealing with influenza?
- Global influenza network (GIN - part of WHO) - estimate the strain of virus before the following season and recommend vaccines
- There are errors in the estimate, time constraints. Third world don’t have resources for this. There can still be antigenic drift, so even if we have the perfect vaccine this can still be inefficient.
