viral evasion of immunity

Question 1

how viruses are dealt with by cellular immunty

Answer 1

they are intracellular, so their proteins are presented by MHC class 1 molecules, which activate CD8 cytotoxic T cells

Question 2

examples of viruses that evade ANTIGEN LOADING

Answer 2

HSV prevents processed peptide going through transporter TAP to be presented onto MHC molecule

Question 3

example of viruses that modulate tapasin

Answer 3

tapasin is a protein that loads antigen onto MHC molecule- CMV prevents this

Question 4

example of virsues that affect MHC

Answer 4

herpes prevents MHC molecule going to surface, thus it’s degraded in cytoplasm

Question 5

virus that counteracts BOTH innate and cellular immune response

Answer 5

human papillomavirus- prevents MHC being expressed on surface

Question 6

how viruses avoid NK cells

Answer 6

normal cells express MHC, otherwise they are killed by NK cells- if viruses didn’t have MHC, they would die, hence they present MHC ANALOGUES (mimics)

Question 7

virus- mediated immunosuppression- include virus

Answer 7

MEASLES infects SLAM cells ie memory cells, thus if person infected, their immunological memory is erased and they’re very vulnerable for the next couple of years

Question 8

how viruses evade ANTIBODY response, and type, with examples

Answer 8

RNA viruses have ERROR PRONE POLYMERASES that causeantigenic variation- either antigenic DRIFT (constant evolution eg influenza), antigenic SHIFT (new antigen from animal eg influenza), or many serotypes (eg poliovirus has 3 types, dengue has 4, rhinovirus has 100)

Question 9

name of influenza viral antigen

Answer 9

haemagglutinin

Question 10

what parts of antigen does antibody target+ name of antibody

Answer 10

the STALK (head) and the STEM- the stalk has SPIKES is very variable, so antibody is specific, whereas stem is not variable, so a single antibdoy can affect multiple types of antigens at the stem- AKA BROADLY NEUTRALISING antibody

Question 11

how to produce an influenza vaccine that causes production of bn (broadly neu) antibodies

Answer 11

a headless haemagluttinin, or a glycosylated head/stalk

Question 12

how HIV evades antibodies- name antigen

Answer 12

its gp120 is very variable, also poorly accessible by anitibodies, and has excessive glycosylation to prevent antibody binding-

Question 13

solution to HIV evasion and problem

Answer 13

again broadly neutralising anitbodies- some mutants may escape however

Question 14

polio vs rhinovirus in terms of vaccines- why vaccine can be made for polio, but not rhinovirus

Answer 14

polio only has 3 serotypes, so vaccine can contain 3 antigens, but rhinovirus has 100, so impossible to make vaccine

Question 15

effect of dengue infection

Answer 15

leads to haemorrhagic fever, where blood leaks from capillaries, leading to severe bleeding

Question 16

cause of haemorrhagic fever in dengue- ANTIBODY DEPENDENT ENHANCEMENT

Answer 16

dengue has 4 serotypes- an antibody can neutralise 1 type, but binds to another and does NOT neutralise it: it thus forms an IMMUNE COMPLEX, causing inflammation ie cytokine storm: thus important that vaccine to dengue doesn’t make things worse