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Infectious Diseases
Unit 4 Lesson 4 plan
Do now
• What are the two ways a pathogen causes
damage?
Do now
• What are the two ways a pathogen causes
damage?
– Direct
– Indirect
Do now
• What are the two ways a pathogen causes
damage?
– Direct
– Indirect
• What feature do both types of damage have in
common?
Do now
• What are the two ways a pathogen causes
damage?
– Direct
– Indirect
• What feature do both types of damage have in
common?
• They cause host cell lysis
Do now
• Can you remember how bacterial pathogens make
you sick? Today, we’ll consider how a virus damages a
host (i.e. how it makes us sick!).
• Let’s pretend a virus in our body is a lone soldier in
enemy territory and one of our cells is a factory the
soldier encounters.
• How could the soldier use the factory if he was
carrying building information?
How do viruses make us sick?
Do you remember the two ways bacteria cause damage?
Viruses damage
through their main goal:
Making more viruses!
But viruses need our cells to
reproduce.
The viral lifecycle has three stages:
1. Enter the cell
2. Replicate
3. Exit the cell
Remember a virus needs to use a cell
and evolution has molded this ability:
1. First the virus attaches to the cell it is going to infect.
2. Then the virus enters the cell.
Surface receptors of HINI
Replication strategies depend on the
genetic code the virus has.
• RNA viruses
• DNA viruses
Before we can learn how viruses
replicate we need to remember
molecular dogma!
DNA
RNA
Protein
Before we can learn how viruses
replicate we need to remember
molecular dogma!
DNA
Replication
RNA
Transcription
Protein
Translation
Where in the cell do these processes take place?
Before we can learn how viruses
replicate we need to remember
molecular dogma!
DNA  RNA  PROTEIN
DNA viruses follow molecular dogma
They need to get their DNA into the nucleus
Herpesvirus is a DNA virus
DNA  RNA  PROTEIN
DNA Viruses need host proteins to replicate
Herpesvirus is a DNA virus
RNA  RNA  PROTEIN
1. RNA viruses defy molecular dogma by making RNA from RNA
2. To do this they bring specialized enzymes with them
H1N1
RNA viruses bring this enzyme with them
RNA  DNA  RNA  PROTEIN
1. Retroviruses like HIV are RNA viruses
2. They defy molecular dogma!
3. They make DNA from RNA
RNA  DNA  RNA  PROTEIN
1. Retroviruses defy molecular dogma by making DNA from RNA
2. To do this they bring specialized enzymes with them
Retroviruses bring the reverse transcriptase enzyme with them.
They use an integrase, to insert the DNA into the host genome.
RNA viruses cannot correct errors
Random uncorrected mutations in RNA viruses cause Antigenic Drift
Exit strategies
Can you remember the exit strategies for:
•
Naked viruses?
•
Enveloped viruses?
Wrap up
• How do virus make you sick?
• Which strategy for survival is best for
viruses? What is the most convincing
evidence for your answer?