The Flu: The Virus, The Vaccine, and Surveillance Joanna Malukiewicz GK12 Program School of Life Sciences Arizona State University
What do we know about the flu? What kind of bug is it? How do you know if you have it? How do you get? What else do we know about it?
Part I: Getting to Know Our Bug
Part I: A Simple Model of our Bug The flu, or influenza, is a virus. What actually is a virus? A typical virus consists has a genetic material core surrounded by a protein coat In addition to these basic features, the flu virus has surface proteins protruding from the protein coat How do viruses reproduce?
Understanding our bug There are three types of influenza (A,B,C) N8 N8 H1 H1 We will be concerned with type A (more on that later...) H1 N8 Surface proteins on A, B, and C viruses are also called surface antigens A viruses have two surface antigen SUBTYPES called H and N H11 N3 H and N surface antigens are even further subdivided into H1-16 and N1-9 N3 N3 H11 H11
What do you think is the purpose of surface antigens? For the virus? For us?
The Double Life of Surface Antigens Surface Antigens are Important for the Virus for Host Cell Entry (think of viruses as parasites) As a means to evade host protective mechanisms What are host protective mechanisms?
The double life of surface antigens For humans, surface antigens help identify and name viruses Influenza A will only have one type of H surface antigen and one type of N surface antigen How do you think that information helps scientists discriminate between differ viral types Influenza A which has H3 antigens and N8 antigens on its surface is simply called H3N8
How many different types of influenza do you think infect humans? (eg. H3N8, H4N1, etc) Currently humans are infected by H1N1, H3N2, and influenza B Are humans the only hosts to be invaded?
What types of cells does influenza invade (prokaryotes, eukaryotes, plant cells, animal cells)? How might influenza use its surface antigens to invade host cells? The virus antigen binds a RECEPTOR on the host cell. Where would we find the host receptor?
Receptors The receptor is located on the cell membrane Binding of the receptor by the virus causes it to be engulfed by the cell. What is the process for a cell swallowing something? Once the virus invades the cell, it uses the cell s machinery to replicate itself many many times
Host Defenses??? But wait... What about the host? How does the host protect itself against influenza invasion?
The immune system is important for host defense against foreign invaders like viruses The immune system recognizes influenza via viral surface antigens (H and N) The host has guard particles constantly on the lookout for invaders When those particles spot viral surface antigens the immune system is sent in to destroy the virus The immune system keeps a permanent record of all invaders. This makes it easier for the host to remember recurring invader and destroy them faster the second time around
Part II: Viral Defenses and Flu Evolution Is there a flu season? How often does it come around? What causes this seasonality? Didn t we say that our immune system remembers what type of flu invaded us? Well why do we keep getting sick flu season after flu season??!!
A Closer Look at Host Defenses The host (like us) takes a search and destroy approach Antibodies are the search, roam ing the host body looking for invaders Antibodies stick all over foreign invaders when found Antibodies alter the rest of the immune system to destroy If antibodies find influenza they stick to the virus s H and N antigens
The Amazing, Changing Antibody Antibodies are encoded in our genetic material The body generates MANY different versions of antibodies In fact, there are so many types of antibodies that the probability that an antibody recognizes a virus just by chance is very high As mentioned before, the body keep permanent copies of antibodies that recognize invaders How may this be advantageous for the host? In case that same virus invades our bodies again later... those same matching antibodies will help destroy the same virus again and again and again. That is called being immune to an invader in our bodies. But we said that people continually keep getting sick from the flu... so what s going on between the flu and our immune systems?
The Influenza V. Antibody Brawl Viruses change extremely fast by mutation That means during replication the genetic material is changed One possible effect of this is a change in the genetic material that encodes surface antigens A mutation can create a new surface antigen for the virus
The Influenza V. Antibody Brawl How can influenza use new surface antigens to protect itself against the host s immune system? Invading influenza that has new H or Ns poking out is not recognized by the immune system Thus the virus gets into our cells and replicates and invades more cells
So when the flu evolves it replaces one of its old Hs or Ns with a new one Can our bodies fend off the viruses with the new surface antigens with red or yellow antibodies?
Remember that our bodies only will have the red and yellow antibodies from a previous influenza invasion The blue, pink, and green surface antigens will become common enough from several rounds of replication that an antibody will match up with them That will help our bodies fight the mutated antigens Can anyone explain the seasonality of the flu based on the surface antigen v. antibody brawl?
Can we do anything to get ahead of the curve before the virus mutates again?
Part III: Vaccines and the National Flu Surveillance Program
Infection and Immunity: The Big Picture Influenza invades host cells Both host and virus have natural mechanisms against each other Virus mechanisms include fast evolution through mutation Host defenses include making a large variety antibodies and storing antibodies against specific invaders Viruses rapidly change themselves by swapping their surface antigens from flu season to flu season This creates a complicated race between virus and host to always out do each other from flu season to flu season
Vaccinations Vaccinations are another layer of protection that complement our natural defenses Any idea on what vaccinations are and how they work?
The Flu Vaccine We get flu vaccinations to outsmart the flu virus The flu vaccine contains parts of deactivated flu in very very minute amounts The amount is enough to get your immune system prepped but not enough to get you sick How does the vaccine work so that when flu season comes around your body is ready against attack?