5 - Patterns of Viral Infections

Question 1

describe the mechanism by which some people are resistant to HIV

Answer 1

• 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

Question 2

Define pathogenicity

Answer 2

the ability of a virus to cause disease

Question 3

Define virulence

Answer 3

described the capacity of a virus to cause disease

Question 4

Pathogenicity vs virulence

Answer 4

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.

Question 5

Which viruses have tropisms that determined by receptors

Answer 5

HIV and measles

Question 6

What determines the tropism of influenza?

Answer 6

the cutting of the proteins of the virus into 2

therefore, the fluid that lines the lungs that have the right proteases

Question 7

What is meant by iatrogenic?

Answer 7

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

Question 8

What is meant by nosocomial?

Answer 8

acquired in hospital

Question 9

What is meant by germ line?

Answer 9

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

Question 10

When do viral rashes occur?

Answer 10

when the virus leave the blood and enters the skin

Question 11

What cells does polio infect?

What can it cause?

Answer 11

motor neurones

can causes paralysis

Question 12

What does rubella have a strong tropism for?

Answer 12

dividing neuronal tissue

Question 13

What is a chronic viral infection? Give an example

Answer 13

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

Question 14

What is a latent viral infection? Give an example

Answer 14

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

Question 15

How do papilloviruses cause oncogenesis?

Answer 15

encode inhibitors of tumour supressor p53, E6 and E7

Question 16

How do Hepatitis B and C cause oncogenesis?

Answer 16

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

Question 17

Epstein-Barr Virus leading to oncogenesis

Answer 17

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