L10-Hiv and other viruses

Question 1

What kind of virus is influenza and what are the three main species?

Answer 1

Influenza is a segmented RNA virus. The three main species are A,B and C of which influenza A is the most severe.

Question 2

What influenzas infection strategy?

Answer 2

To infect the upper and lower respiratory epithelium

Question 3

What are the two main immune responses to influenza?

Answer 3

CD8 T cells protect respiratory mucosa and contribute to establishing inflammation of the lungs.
Antibodies limit the spread of infection within the lungs and are essential for protecting against reinfection

Question 4

What is antigenic drift and how does it happen?

Answer 4

Antigenic drift is over a few seasons the influenza virus can mutate to the point where its antigens can no longer be recognised by the antibodies originally made to fight them.

Question 5

What is antigenic shift and how does it happen?

Answer 5

When the segmented genome of influenza rearranges itself to produce a completely new strain. This typically happens every 10-30 years. The strains that infect the lower airways have much higher mortality than those infecting the upper airways.

Question 6

What is the treatment for influenza?

Answer 6

It can be treated with anti-influenza agents however these are fairly poor. The best treatment is prevention through vaccination.

Question 7

What are the two distinct species of HIV?

Answer 7

HIV 1 - more common in western world

HIV 2 - slower developing and sometimes requires no treatment

Question 8

What family are HIV a member of?

Answer 8

The retroviridae family

Question 9

What makes HIV so hard to eradicate?

Answer 9

It integrates its DNA with the host cells DNA becoming permanently incorperated

Question 10

Which cells does HIV principally infect?

Answer 10

CD4 T cells

Question 11

What is the lifecycle of retroviruses like HIV?

Answer 11

Infection
Integration of genome (nucleus)
Transcription of genome (nucleus)
Release of mature virions from infected cells

Question 12

What are the three major genes in HIV?

Answer 12

Gag (capsid proteins, core particle)
Pol (polymerase ; also encodes integrase and protease)
Env(envelope ; outer structural proteins responsible for cell-type specificity)

Question 13

Which enzyme cuts the host DNA to integrate HIV?

Answer 13

Integrase

Question 14

What are the three distinct clinical phases of HIV?

Answer 14

Acute serconversion - flu like symptoms which the pro-viral reservoir is created.
Asymptomatic infection - 7-15 years during which CD4+ T cell count progressively falls
AIDS- eventually falls below a critical level at which point they will die without treatment

Question 15

Why do herpes viruses cause lifelong infection?

Answer 15

They exhibit a latent phase where the genome does not replicate and then replication is resumed at a later stage.

Question 16

What kind of patients are most susceptible to the herpes virus?

Answer 16

Those that are immunosuppressed as they will have low T cell numbers.

Question 17

What are the symptoms of herpes simplex virus 1,2 and 3?

Answer 17

1 and 2 produce cold sores or genital sores whereas 3 produces an ichy spotty rash that turns into blisters

Question 18

What is Epstein Barr Virus?

Answer 18

It is a type of herpes virus that infects B cells and transforms them to give a mild form of lymphoma. This is a good example of a cancer causing viral infection.

Question 19

What is cytomegalovirus?

Answer 19

It is a type of herpes virus that leads to an asymptomatic infection. It occupies lots of the immune system especially the T cells. When T cell responces fail due to age for example then the virus can infect other cells and cause death.