Week 4 Flashcards
Can viruses have both DNA and RNA
No
What is a viruses genome surrounded by
A protein capsid with or without a phospholipid membrane studded with viral glycoproteins
What are the 4 virus shapes
Helical RNA
Polyhedral(icosahedral) DNA
Enveloped RNA
Complex DNA
A viral structure consists of
Nucleic acid + capsid(protein coat) +/- envelope +/- spikes
4 examples of viruses with envelopes
HIV
Influenza
Herpesvirus
SARS-CoV2
What are the advantages of a viral envelope
Glycoproteins help to bind to receptors on host cell
Host derived lipid bilayer help evade immune system
Disadvantages of viral envelope
Lipid bilayer makes enveloped virus more susceptible to detergents, alcohol, and dessication
How to viruses attach to cells
Viral proteins bind to receptors on host cell
Five steps of viral lifecycle
Attachment
Entry
Genome replication and gene expression
Assembly
Release
What is tissue tropism
Receptor is tissue specific
What are the two RNA strand types
Positive strand and negative strand
Can a positive strand RNA be immediately translated by the host cell
Yes
Can a negative strand RNA be immediately translated by the host cell
No it needs to be transcribed into a positive strand by RNA dependent RNA polymerase
What is special about what a retrovirus does with its genetic material
Turns its +ssRNA into +ssDNA using reverse transcriptase. The DNA is then integrated into the hosts DNA
What is an integrated viral genome called
Provirus
What is a persistent viral infection
When a virus is not cleared by the immune system
What are the two types of persistent viruses
Latent and chronic
What is a latent virus
A virus that lies dormant in a cell in a process called latency. Undetectable by immune system.
What is an example of a latent virus
HIV.
Small pox lying latently before reactivating later in life as shingles
What is a chronic viral infection
Virus which the body cannot eliminate. Evades immune system
How are viruses diagnosed
Electron microscopy
Identify cell abnormalities with light microscope
Enzyme immunoassay
Nucleic acid amplification tests
What is a cytopathic effect
Cell abnormality due to viral infection
What is enzyme immunoassay
Antibodies are used to detect virus by attaching to specific biomollecules called antigens.
Wash is applied to clear unattached antibodies.
Substrate is added to change colour of remaining antigens which indicates the virus.
What is host range
Type of cells a virus can infect
What is antigenic drift
Point mutations causing slight changes in spike proteins
Antigenic shift
Major changes in spik proteins due to reassortment
How many people were living with HIV in 2023
39.9 million
HIV incidence 2023
1.3 million
HIV death 2023
630000
Is HIV and AIDS the same
No AIDs is a medical condition induced by HIV
What is AIDS
Acquired Immunodeficiency syndrome,
Immune system too weak to fight infection
What are the features of HIV
Enveloped
Bullet shaped capsid
Contains reverse transcriptase, integrase, and protease
Has two copies of RNA
What type of cells does HIV target
CD4+
What are the steps in the HIV lifecycle
1) binding: attach to host cell surface
2) fusion: fuse with membrane RNA, reverse transcriptase, integrase and other proteins enter cell
3) reverse transcription: RNA->DNA from reverse transcription
4) integration: viral DNA integrated into host DNA
5) replication: viral DNA copied into more viral RNA which makes viral proteins
6) assembly: the RNA and proteins move to cell surface and form immature HIV
7) budding: virus released thanks to protease and matures
What is the role of reverse transcriptase
Convert RNA to DNA
What is the role of integrase
Integrate viral DNA into host DNA
Why is HIV hard to treat
High mutation
Latency
Integrate DNA into host genome
At what parts of HIV lifecycle do ARTs affect
Fusion
Reverse transcription
Integration
Budding
What type of ARTs affect reverse transcription
Nucleoside and non nucleoside reverse transcriptase inhibitors (NRTI and NNRTI)
What is the UNAIDS 90-90-90
90% diagnosed 90% of that on treatment 90% of that suppressed
What is Treatment as prevention
Getting early testing and treatment of HIV to become undetectable in viral load and not transmit HIV
What is PrEP
Using cART without HIV to prevent contracting the virus
What is PEP
Emergency cART for after exposure
