Quote (Grippster @ 16 Dec 2010 17:54)
if vaccinations dont allow diseases to take their course, and their toll on our population, then the natural selection u speak of becomes a test of who's body can best withstand chemicals, in this synthetic age, rather than germs lol
so yea i guess your right, natural selection never stops, just changes. i prefer the old kind though.
2. elaborate?
1.
Vaccination allows diseases to take their course to a certain extent.
What vaccination does is prepare your immune system to counter the pathogen once you are infected with it.
For example, a classic vaccine approach is to prepare a less pathogenic version of x virus, inject it into you, your immune system attacks with weak non-specialist immune cells and eventually builds strong specialists against it. A small portion of the specialists (T cells and B cells) become memory cells, and the rest of them die when the infection is cleared. Theses memory cells can be reactivated once it is in contact with the wild-type pathogen.
T cells (CD8 T cells) are those who recognize infected cells and B cells are those who produce antibodies to neutralize viral particles.
The advantage of vaccination is that your body does not need to go through the stage of preparing the "specialists" to clear the virus because theses specialists are already there and can proliferate when in contact with subunits of the pathogen. A few cells get infected, but your immune system overcomes the infection quickly and effectively.
Now say you want to prepare a vaccine against HIV. You can't just build a less virulent strain and inject it in people because it just wont work; the virus attacks immune cells and integrates into the cell, makes reservoirs, etc. So scientists try different approaches and thus need to manipulate synthetic/natural biological material. Note that theses do not harm you. Take for example a viral vector used in vaccination. Adenovirus. They manipulate the virus to put part of HIV genes into it and thus hope that when your immune system sees the adenovirus, it will make cells against the HIV portion and confer protection when you actually get infected with HIV. That adenovirus naturally causes a small cold. But they modify it and make it non-replicative and remove it's gene that helps it counter the immune system. The adenovirus becomes harmless.
2.
HIV and HCV are RNA viruses. RNA viruses, when they replicate, have no repair mechanism, meaning that the sequence of the virus is never the same. When your immune system puts selective pressure on a specific sequence, the virus that has a mutation on that sequence can escape recognition and neutralization by your immune system, if replication is effective. And actually when you observe mutations caused by this selective pressure, that tells you that the immunological branch (either T cell or B cell) can be important in viral control. The virus always seem to be ahead of our immune system partly because of theses mutations. If you look at patients who use antiretroviral drugs in case of HIV, there are well known mutations on the virus that appear because of the use of drugs. Eventually, the patient is filled with viruses with that mutation. Those without it could not replicate because of the drug.
This post was edited by Haitham on Dec 16 2010 05:57pm