antigenic variation

Question 1

differenece between antigenic variation and antigenic diversity
-what does it occur in
-is it reversible or irreversible

Answer 1

variation (viruses, bacteria and eukaryotic pathogens)= reversible, uninduced. one varant at a time expressed by each cell

diversity (viruses especially RNA genomes) = irreversible
mutation and immune selection for survivors that transmit.

Question 2

antigenic variation examples:
1) borrelia burgdoferi (bacteria)
-how is it spread
-how does glycoproteins antigen change
-genome

2) neisseria (bacteria)
-where does bacterium live
-consequeces of neisseria
-how antigen variation occurs

Answer 2

1) spread by ticks
-their glycoporteins antigen change by recombination of silent gene
-has unusual gene

2) lives in nasopharynx
result in Neisseria gonorrhoeae and Neisseria meningitis
-antigenic variation involves pilus by changing number of pilli
-recombination of silent pili gene

Question 3

3) trypanosoma brucei
-what is key to antigenic variation
-one mechanism of VSG switching
-the major route for VSG swithcing

4) malaria
why symptoms occur
-what does antigenic variation in plasmodium only rely on
-what is PfEMpI and what does it do

5) HIV-1
-how does antigen variation occur.
what is gp120
-what happens when this glycoprotein is mutated

Answer 3

3) thousands of silent VSG genes
-only one VSG expressed at a time. VSG can occur due to swtching is based on transcription.
but the major route of VSG switching involves recombination

4) the symptoms occur when plasmodium invades red blood cells
pfEMPI is a family of proteins expressed on red blood cells infected with the malaria parasite plasmodium falciparum. this helps parasite cause malaria.
-antigenic variation relies only on transcription

5) due to a high mutation rate caused by reverse transcriptase and rapid replication
-gp120= a glycoprotein on HIV-1 virus that is essential for entry into host cells.
-mutation in gp120 allows immune envasion

Question 4

antigenic diversity example
1) Influenza A
-how does variation occur in viral surface proteins
-the two viral surface glycoproteins of influenza A and function. HA and NA
-how many genome segments

2) babesia bovis
-what is it related to
-how is the pathogen of cattle transmitted
-can go through antigenic variation and diversity

Answer 4

1) variation casued by antigenic drift and antigenic shift
-HA =attaches the viroin to cells, Na= releases the viron (spread)
-8 genome segments (RNA encoding makes 16 proteins)

2) related to plasmodium
-pathogen of cattle transmitted by ticks

Question 5

difference between antigenic drift and antigenic shift
-changes to HA and NA
-how fast process occurs
-how similar to antigenic variation

Answer 5

drift=
-minor changes to HA and NA
-gradual accumulation of mutations in genes encoding HA and NA
-slow process allows virus to partially evade immune system
-driven by immune selection like antigenic variation

shift= dramatic sudden change in influenza virus that occurs when different strains of influenza A infect the same host cell and exchange genetic material (genetic reassortment of NA and HA)
-not like antigenic variation