Mechanisms Of Viral Infection And Pathogenesis Flashcards
What are the types of viral infection?
Acute
Chronic
What is acute infection normally resolved by?
Immune system
What are the two options for acute infection resolution?
Either kills you or you get better
What are the types of chronic viral infection?
Latent, reactivating infection
Persistent infection
What is a latent, reactivating infection?
Disease resolves itself and then reappears some period of time later
What are the most common chronic latent reactivating viral infection?
Herpes
What are the subtypes of herpesvirus?
Herpes simplex 1 and 2 Varicella zoster Epstein Barr virus Cytomegalovirus Human herpes virus 6-8
What does herpes simplex 2 cause?
Primary gingivostomatitis (rash) in children Cold sore in adults
What does varicella zoster virus cause?
Chicken pox-> shingles later in life
What is shingles?
Virus incubated in the spinal cord
What is persistent infection?
Initial disease followed by years of very low viral load followed by end of life viral disease
What are some examples of persistent infection?
AIDS
HCV
Measles
Why is congenital rubella slightly different to a normal persistent infection?
Persistently high viral load
What causes congenital rubella?
Infected in utero so virus seen as self and the baby is born immuno tolerant
What is another name for asymptomatic disease?
Inapparent infections
To be inapparent, what does a virus need to be?
Non-cytopathic and host adapted
What does viral pathogenesis result from?
Cell and tissue damage caused by viral infection
What does the Ebola virus target?
Vascular endothelial cells
What cells does the influenza A virus target?
Lung epithelia
What does RSV induce?
Syncytial merging in lung epithelia
What is immunopathology?
When the relatively limited damage caused by a virus is made worse or caused by the hosts immune system
What is the normal pathway of hepatitis C?
Acute infection -> chronic inflammation -> fibrosis -> cancer or cirrhosis (or both)
Is HCV cytopathic or non-cytopathic?
Non-cytopathic
What does chronic HCV cause?
Severe liver damage and loss of hepatocytes
What is associated with HCV (cellularly)?
Leukocyte liver infiltration and high pro inflammatory cytokine levels
What is HCV persistence associated with?
The generation of HCV variants that are not recognised by CD8+ cells
How many serotypes of dengue fever are there?
Four (1-4)
What are the symptoms of primary dengue fever?
Mild fever skin rash Headache Bone and muscle pain Nausea Vomiting
What are the symptoms of secondary dengue fever?
Acute fever Severe abdominal pain Headache Plasma leakage Intravascular volume depletion Coagulation dysfunction
What is the greatest risk factor for severe dengue fever?
previous infection with a different serotype
How does severe dengue work?
Non-neutralising antibodies coat the virus and form immune complexes
Get internalised into mononuclear phagocytes through their fc receptors
Products of the complement cascade are released
Sudden increased vascular permeability, shock and death
What is the immunopathology of RSV?
Infection in early life shows an unbalanced Tht/Th2 response
-> depressed inflammatory cytokine production, CD8+ responses and IgG production
Slow clearance and poor memory cell development
-> enhanced IgE production, leading to allergy/asthma on re-exposure
What is the pathology of influenza?
Mild URTI-> severe LRTI LRTI-> damaged lung epithelia and viral pneumonia Fever Neurological (headache, malaise) Myalgia
What is antigen shift?
When a virus suddenly changes its surface proteins
What is antigen drift?
The gradual changing of surface proteins over time
