5 - Patterns of Viral Infections Flashcards Preview

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Flashcards in 5 - Patterns of Viral Infections Deck (17):

describe the mechanism by which some people are resistant to HIV

- some have a mutation in CCR5, so don't have a proper CCR5 receptor receptor
- some people produce a large amount of chemokine which blocks the use of the co-receptor


Define pathogenicity

the ability of a virus to cause disease


Define virulence

described the capacity of a virus to cause disease


Pathogenicity vs virulence

Pathogenicity refers to the ability of an organism to cause disease (ie, harm the host). This ability represents a genetic component of the pathogen and the overt damage done to the host is a property of the host-pathogen interactions. Commensals and opportunistic pathogens lack this inherent ability to cause disease. However, disease is not an inevitable outcome of the host-pathogen interaction and, furthermore, pathogens can express a wide range of virulence.
Virulence, a term often used interchangeably with pathogenicity, refers to the degree of pathology caused by the organism. The extent of the virulence is usually correlated with the ability of the pathogen to multiply within the host and may be affected by other factors (ie, conditional). In summary, an organism (species or strain) is defined as being pathogenic (or not), and depending upon conditions, may exhibit different levels of virulence.


Which viruses have tropisms that determined by receptors

HIV and measles


What determines the tropism of influenza?

the cutting of the proteins of the virus into 2
therefore, the fluid that lines the lungs that have the right proteases


What is meant by iatrogenic?

due to medical care (e.g. contaminated needles)


What is meant by nosocomial?

acquired in hospital


What is meant by germ line?

part of the host genome (e.g. integrated retrovirus)


When do viral rashes occur?

when the virus leave the blood and enters the skin


What cells does polio infect?
What can it cause?

motor neurones
can causes paralysis


What does rubella have a strong tropism for?

dividing neuronal tissue


What is a chronic viral infection? Give an example

there is low level of replication inside of tissues which regenerate
e.g. papillomaviruses in warts


What is a latent viral infection? Give an example

viral genomes are maintained but no virus is seen until episodes of reactivation at times when you are immunocompromised
e.g. herpes


How do papilloviruses cause oncogenesis?

encode inhibitors of tumour supressor p53, E6 and E7


How do Hepatitis B and C cause oncogenesis?

cause heptocellular carcinoma
- a hepadnavirus (has a DNA genome)
- uses reverse transcriptase
- transmitted through blood and semen
- a blood borne virus


Epstein-Barr Virus leading to oncogenesis

95% of people are infected with EBV
some people with EBV will go on to develop cancer (combined with other circumstances)
e.g. Burkitt's lymphoma, Hodgkin's lymphoma, Nasopharyngeal carcinoma