Introduction to virology Flashcards
what is the structure of a virus?
nucleic acid genome
protein capsid
sometimes an envelope
what does the nucleic acid genome of a virus determine?
the rate of mutations and the risk they pose
what does the protein capsid of a virus do?
Protects the genome
Determines the cells it infects through controlling shape and surface proteins for adhesion to receptors on host cells
what is an envelope which some viruses have?
Lipid bilayer, derived from the host cell, containing viral proteins
what is the purpose of an envelope on a virus?
Host doesn’t see the virus as foreign
how does a virus replicate?
Uses the host cells machinery to replicate -> can’t replicate independently
give an overview of the replication cycle of a virus
attachment
entry
synthesis
assembly
release
virus replication what happens in attachment?
Attachment to host cell receptors, specificity determined by capsid
virus replication, what happens during synthesis?
Genome replicated
Transcription and translation of viral proteins that will make the capsid
virus replication, what happens during assembly?
genome and viral proteins assemble together
virus replication cycle, between assembly and release what happens?
There is a period of time where it isn’t releasing particles but still multiplying so the immune system cant recognise it till later on once its already multiplied
virus replication cycle, what happens in release?
Lysis: destroys the membrane of the host cell, killing it
Budding: form an envelope from the host cell membrane. Seen in more chronic viruses as it doesn’t kill the host cell
what viral factors cause damage to the host? 4
cell lysis
cell-cell fusion
inhibition of host cell transcription and translation
alteration of host cell cycle
how does cell-cell fusion cause damage to the host?
syncitia formation (multinucleated cells)
compromise barrier function of cells
leads to death of cells
give an example of how alteration of host cell cycle causes damage
cause proliferation -> cancer linked to HPV
name 3 host cell factors that cause damage to the host
Apoptosis
Lysis of infected cells by immune system
Inflammation
what is latency? give an example of a virus
virus replicating but not making surface proteins so goes undetected (herpes)
how do viruses cause chronic/persistant infections? give examples of viruses
virus replicates with the cell (not separate) so goes undetected and can reinfect later in life (chicken pox, HIV,HepC)
give an example of a virus that causes transformation of host cells
HPV -> cancer
how does the immune system respond to viruses?
produce antibodies
cytotoxic T-cells
what do antibodies do?
Target for destruction
Impair ability to cause destruction by blocking target sites so cant infect other cells
what do cytotoxic T-cells do?
Recognise capsid proteins and destroy the cells
how are viruses treated?
anti-viral drugs
vaccines
how do antiviral drugs work?
Target proteins specific to certain viruses
what kind of virus is HIV/AIDs?
blood borne
what is the mechanism of HIV/AIDs?
- Changes DNA to RNA with reverse transcriptase
increases the mutation rate of viruses -> more variation to avoid immune response
what does HIV/AIDs lead to?
immunodeficiency
how is HIV/AIDs treated?
Viral drugs can target reverse transcriptase
why are vaccines almost impossible to find for HIV/AIDs
Through each circle of replication it changes and alters its surface
name 2 AIDs defining illnesses
Esophageal candidiasis
Kaposi’s sarcoma
how is HIV/AIDs prevented?
limit exposure
what type of virus is hepatitis?
blood-borne
what is the main clinical manifestation of hepititis?
liver disease
which type of hepatitis has a risk for chronic hepatitis?
Hep C
what are the symptoms of Hep B?
malaise, jaundice, liver disease (that leads to cancer)
which type of hepatitis has a successful vaccine?
Hep B
herpes HSV1 causes what disease common in preschool children?
primary gingivostomatitis
how does oral herpes present?
vesicles and ulcers on lips, buccal mucosa and hard palate
reactivation of herpes is common. this is due to what?
dormancy
presents as cold sores
