Vaccines and Immunotherapy

I'm a bit hesitant to write about this topic because it's one that some people have very strong opinions about, and I really don't want to start a flame war on this blog. At least this lecture was short, so I guess I'll just say my piece quickly and get the hell out.

Immunisation

Most of the time, when we talk about immunisation, we are referring to active immunisation. The goal of active immunisation is to ultimately form a memory response so that the person can easily fight off the pathogen again. There is also passive immunisation, in which preformed products are given to patients to prevent illness following exposure (to tetanus, rabies etc.). These may also block toxins, as in the case of diphtheria antitoxin and snake antivenoms. Passive immunisation, however, is not long lasting and produces no memory response.

A vaccine, as I'm sure you know, basically contains a modified component of the pathogen that can elicit an immune response without actually making you catch the disease. The end result is that you can build up immunity to said diseases without experiencing some of the risks of the disease itself, like deafness (measles), infertility (mumps), paralysis (polio), and so on. Vaccination basically works on the principles of the primary and secondary response, which I've outlined here: when you are vaccinated you produce IgM, and during subsequent booster shots, or exposures to the antigen, you produce more antigen-specific IgG which can clear the infection much more rapidly.

One of the nice things about vaccination is that it doesn't just protect the individual. If an individual is immune to the disease, then they generally won't be able to pass it on. The more people that are immunised, the less potential "disease vectors" there are to spread the disease to people who can't be immunised (due to being immunocompromised, too young etc.) or people who, for whatever reason, didn't generate a memory response following vaccination.

Vaccination was also responsible for the eradication of smallpox. You've probably heard the story: Edward Jenner found that milkmaids who had experienced cowpox (a disease related to smallpox but much less severe) never caught smallpox. He then immunised many people with the cowpox virus so that they would not catch smallpox. This worked because cowpox and smallpox, being related viruses, share many surface antigens. Therefore, antibodies generated against cowpox could help to clear smallpox as well.

There are several different types of vaccines. Some vaccines, known as live attenuated vaccines, contain a weakened version of the virus or organism. If these mutate to become active again they can cause issues, but this is very rare. Live attenuated vaccines include the Sabin polio vaccine, the MMR vaccine and the BCG vaccine against tuberculosis (BCG is related to tuberculosis). Some vaccines, such as the Salk polio vaccine and the flu vaccine, contain an inactivated or killed organism. Other vaccines only contain subunits of the organism- for example, the tetanus and diptheria vaccines contain toxoids (toxins that have been made harmless), and the Hepatitis B and HPV vaccines contain recombinant proteins (immunogenic proteins which have been created artificially). Inactivated/killed vaccines and subunit vaccines cannot give you the diseases that they protect against; however, they may be slightly less effective, and may require an adjuvant (usually aluminium) to produce an immune response.

Immunotherapy

One type of immunotherapy is cytokine therapy, in which certain cytokines are given to treat a disease. An example of this is IFN-α, which can be given to treat certain types of cancers.

Another type of immunotherapy, anti-cytokine therapy, has the opposite effect: it blocks the actions of cytokines. For example, anti-TNF-α can be given to patients with rheumatoid arthritis to reduce inflammation.

Only one more lecture to go for this unit!!