Mechanisms Of Viral Infections And Pathogenesis Flashcards
Why do most viruses not infect us?
Adapted to non human hosts
Excluded by surface barriers
Innate immunity prevents them establishing
Our adaptive immune response has seen something similar
Describe the general patterns of infection
Acute infection
Latent reactivating infection
Persistent infection
What are acute infections?
Resolution by immunity
A huge spectrum of disease and range of outcomes
Kills you or you get better
What is latent reactivating infections?
Human herpes viruses
Life long infection controlled by immunity
What are the symptoms of herpes simplex virus?
Children - rash
Adults - cold sore
What are persistent infections?
Virus is kept under control by active host immune system but keeps being persistent
What are some examples of persistent viruses?
HIV
HCV - flavaris
Measles
Continental rubella
What is continental rubella?
If infected in utero, baby is born immunotolerant - Virus continues to replicate in neonatal tissues
Infects the placenta of pregnant women and viral replication can infect foetal organs
What is the hallmark of continental rubella?
Chronic infection that persists throughout foetal life, with shedding of virus up to 2 years after birth
Viral shedding can result in outbreaks
What are inapparent infections?
Are asymptomatic infections in a host without the occurrence of recognisable clinical symptoms
90% of all poliovirus infections
What is cytopathic damage?
Morphological changes in the cells caused by a virus
Describe the immunopathology of Hepatitis C
Disease of servere liver damage and loss of hepatocytes
HCV is non-cytopathic (cells look same)
Persistence is associated with the generation of HCV variants that are not recognised by CD8+ cells
What is dengue fever?
Most common mosquito born infection
4 stereotypes of the virus
What is the immunopathology of dengue virus?
Antibodies formed in response to infection are not cross protective against other subtypes of the virus
May result in more servere disease due to a phenomenon known as antibody dependent enhancement
What is the immunopathology of RSV?
Infections in early life show unbalanced T cell responses
Depresses inflammatory cytokines production
CD8+ response and IgG production
This enhances IgE production, leading to allergy/asthma on re-exposure
