Hey everybody, Dr. O here. This video we’re going to talk about Antigenic Variation and how organisms use it to hide from evade the immune system. So first just a real quick primer on the immune system, so antibodies are a huge part of your immune system. They’re produced by B cells. Um, and they’re looking for antigens, which are cells surfaced markers. So, I always think of the immune system especially the memory portion of your immune system as looking at one imposters, so a one imposters is a here’s the cells surfaced markers, here’s the features we know about this bank robber. Whatever, right from the old cowboy movies. Um, so antigens are cell surfaced markers. Antibodies are looking for those cell-surfaced markers. So, Antigenic Variation is how organisms change their antigens, change their cell surfaced markers, so they’re no longer looking like that right. So, if I’d robbed a bank, I’d shave my go-tee, I’d get rid of my gray hair, I’d change my clothes etc. etc. So, this is antigenic variation. So, we’re primarily going to focus here on how this works with the influenza virus (the flu virus), but as a couple of real quick examples: bacteria can do this as well. Borrelia burgdorferi, which causes the causative agent of lime disease can do this. So, basically every time someone has a uh fever with lime disease, you’re seeing a change in the cell surface markers and that’s why it can become a chronic disease. Uh, you also have Niceria gonorrhea, the causative agent of gonorrhea. It changes what it’s actual its pili on one of the cell-surfaced structures looks like for the same reasons. So, there are bacteria that can do this, but let’s primarily focus on the influenza virus. So, let’s talk about the two examples and then we’ll talk about where flu pandemics come from and then about the vaccine and why it only works so well and has to be taken annually. So, first we have Antigenic Drift. This is just going to be mutations, right. Viruses um mutate uh, more quickly than bacteria. So, viruses mutate quite often which means they’re going to have these point mutations or base substitutions which every once in a while, uh, pieces of genetic material will change and that’s gonna change what the surface looks like. So, you’re seeing here um that these surface um antigens the hemagglutinins and neuraminidases they can actually change over time because of mutation. So, that’s an example of an Antigenic Drift. The slow steady changing of what the outside of the flu virus looks like. Antigenic Shifts are going to occur when one person is infected with two different influenza viruses. So, you receive virus A, virus B, they actually reassort and swap their genes and out spits virus C which looks a lot different. So, Antigenic Shift is where most if not all of the influenza pandemics like the flu pandemic of 1918 that killed thirty to fifty million human beings, six hundred Americans or the other flu pandemics came from. So, Antigenic Shifts are going to be huge changes in what the outside, the surface of the flu virus looks like. So, these slow and steady changes the Antigenic Drift and these rapid changes Antigenic Shift, this is constantly changing what the outside of the flu virus looks like. This is why, uh the flu vaccine has to be taken annually. So, because you have to basically, they have to try and look and one of the biggest problems of the flu vaccine is how long it takes to produce. So, they have to look and try to guess what are the three or four or five strains of the flu that we’re most likely to see next year in the next flu season and they produced vaccines against those, but since it changes every year you don’t have a flu vaccine that can be taken once and forgotten about or you need a booster every ten years, whatever. This is why the flu vaccine is taken annually. This is also why the flu vaccine is not you know super effective. So, I mean it is helpful, but you’ll see numbers like between 30-40 or 70% effective. So, lower than many vaccines because the flu is constantly changing so if a vaccine protects you against uh the flu viruses you see here on the screen, but they slowly change. They change their outfit, they change their disguise, your immune system is not gonna be able to recognize these new strains. So, that is Antigenic Variation or one of the ways that organisms evade your immune system by constantly changing what they look for. Now in the future, could we see a flu vaccine um that you can take once? Um, I guess what you would say you’d have to create a vaccine that was looking for something on the flu virus that never changed. So, no matter what parts of the disguise, the bank robber is changing um there has to be something there that didn’t change and that would be what your immune system is looking for. So, it is possible, but we’re not there yet. Alright, that is Antigenic Variation. I hope this helped. Have a wonderful day, be blessed!