Dear Diary….. MOAR VIRUSES!
This week we talked about how viruses cause disease, and used a few examples to illustrate that point.
Firstly, was exactly HOW they cause disease: interruptions in cell function/homeostasis/cell death and the immune response. So “flu-like symptoms” should really be called “immune system symptoms”.
Influenza causes symptoms by causing the death of ciliated epithelial cells in the URT, leading to mucus accumulation. The immune system causes inflammation in the URT, leading to more fluid, and producing a systemic immune response resulting in fever, muscle ache, fatigue.
Here’s the video we watched. Please forgive the narrator, he knows not what he speaks about.
And just for sneezes, here’s another video to disgust you….
We talked a LOT in class about antigenic shift and drift. Drift happens all the time to all the things, and while it consists of small changes… the small changes do accumulate across time.
Shift, however, is a pig of a different color. It can only happen in segmented viruses, and only if two similar viruses infect the same cell at the same time. And it can cause some BIG changes.
Which of the two processes is at play in this video?
While there are medications on the market, vaccines are a much better way to protect the population as a whole from influenza infection. The CDC monitors flu activity in real time and produces a lot of reports, which can be found here.
HIV was next on the agenda, and this one is such a sneaky little thing. It hides its genome inside the human’s chromosomes, and slowly destroys the immune system across time. Once the immune system has collapsed, it can re-emerge from hiding and replicate again.
Nasty.
The pathogenesis follows a very typical path…. Acute/primary phase, Clinical latency and AIDS. What are the unique characteristics of each phase?
Finally, Human Papillomavirus. The only cause of warts.
Warts are caused when HPV infects cells of the basal epithelium and induces those cells to replicate faster than the ones around it. These infected cells then rise to the surface of the skin in a column (the wart) where the virus then egresses. Sometimes, the mechanism by which the virus causes the cells to replicate is over-active, and the replicating cells become a tumor. This can lead to cancer, but happens only rarely. It is the most common human sexually transmitted disease, by A LOT.
Finally, we discussed anti-viral drugs and vaccines. Antivirals are great, when you can find them. Unfortunately since viruses use our cellular machinery for dang near everything, its hard to create drugs to stop them. And they quickly become resistant to the drugs, because they evolve so fast (how? why?). With that in mind, vaccines to prevent infection in the first place end up being more powerful.
There are four major types of vaccines available on the market (with some new types in the pipeline). But the idea behind all of them is the same. Trick your body into thinking its sick, and your immune system will produce a MEMORY response…. remembering what that antigen looked like so that it can fight it better the next time around…. Ta Da! Immunity!
Immunity not only protects you, but it also protects the community as a whole…. through herd immunity. The trick is, for herd immunity to work, a certain number of people in the community have to be vaccinated. The fewer vaccinated individuals you have, herd immunity no longer works.
What to focus on this week:
- Describe HOW viruses can make you sick. If I gave you a set of symptoms, would you be able to predict how the virus was causing them?
- Understand the difference between drift and shift. Like seriously.
- Describe the unusual steps of HIV replication and what the consequence is to the virus and to the cell
- Track HIV infection through the three stages of pathogenesis
- Describe how antiviral medications can be used BEFORE you even get infected (PrEP)
- Describe the four different types of vaccines and what are the pros/’cons of each
- Be able to draw and label an antibody and describe is major functions