Evasion of the Immune System

Question 1

antigenic plasticity

Answer 1

rapid changes in the structure of the viral antigen. result of mutation, reassortment, or recombination

Question 2

antigenic multiplicity

Answer 2

antigenic variants with little or no cross-reactivity

Question 3

virokines

Answer 3

some viruses synthesize proteins which are homologs of cytokines/interferons

Question 4

viroceptors

Answer 4

some viruses encode proteins that are homologous to the receptors for cytokines. serve as competitive antagonists

Question 5

down-regulation of MHC class 1 pathway

Answer 5

interfere with expression of MHC I molecules and inhibit antigen presentation

Question 6

inhibition of complement activation

Answer 6

vaccinia virus codes for a protein called VCP which binds to C4b, inhibiting classical complement pathway
glycoprotein of herpes binds to C3b, inhibiting both classical and alternative pathways

Question 7

evasion of neutralizing antibodies

Answer 7

virus produces large amounts of soluble proteins that “soak up” antibody and prevent action

Question 8

latency

Answer 8

transcription of viral genes that encode for viral antigenic proteins is blocked.

Question 9

cell-to-cell spread of viruses

Answer 9

not exposed to the host immune response, never leave the inside of the cells

Question 10

poxvirus & herpesvirus inhibition of apoptosis

Answer 10

produce caspase inhibitors that protect the infected cells against death and allow virus replication to be completed.