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vaccine

About microscopic forms of life, including Bacteria, Archea, protozoans, algae and fungi. Topics relating to viruses, viroids and prions also belong here.

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vaccine

Postby kabuto » Sun Apr 02, 2006 7:47 am

how do we make a vaccine?
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Postby Nithin » Sun Apr 02, 2006 12:11 pm

There are different kind of vaccines. The whole organism vaccines I reckon are the most simple ones. The whole organism vaccines fall in two criterias
1)Live Vaccines and 2) Dead Vaccines
Live Vaccines as the name implies are live organisms which are attenuated ( that makes them loose their ability to infect)
And Dead ones are the vaccines where the organism is killed. These vaccines normaly have to do with the protien coats ( I think so)
Louis Pasteur attenuated Rabies virus by allowing it to grow in the brain of the rabbit for a long time. The rabbit brain was then crushed and vaccine was obtained. That was a long time ago. But now Rabies vaccine is produced by tissue culture methods ( doubtless you will fine in the net).

If you want to know about more complex stuff then try searching about DNA vaccines, Multivalent Subunit Vaccines, Recombinant Vaccines and many more....

Do not take it hard, but the answers to your question do not require expertise in answering them and can be found very easily in the net..........
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Unknown is a galaxy!!!

After you have eliminated the impossible, whatever remains however improbable must be the truth
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Postby kiekyon » Mon Apr 03, 2006 3:41 am

1. isolate the virus
2. use reverse genetic technique form 'seed virus'
3. let it replicate
4. get the antigen or weaken it so that it would infect but not sicken u
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Postby kiekyon » Sat Apr 08, 2006 12:17 pm

The objective in making a vaccine is to change the agent so it cannot cause disease but is still able to stimulate immunity. How this is done for Toxins, Bacteria and Viruses will be discussed in the following paragraphs.

For Toxins this usually means the toxin, a protein, is denatured. When you cook meat, the heat "denatures" the protein and you can see that change as the meat changes from translucent red to dull gray or brown. Chemicals like formaldehyde cross-link amino acids in proteins to chemically "cook" them. This often conserves the proteins antigens in a form that is useful for vaccines at the same time as it damages the toxin's ability to cause damage. Sometimes "denaturing" the toxin also changes the ability to use it as an antigen. More recently, scientists are using genetic engineering to change single amino acids in toxins so they no longer are toxic. Then, that toxin can be used naturally as a vaccine antigen.

Bacterial vaccines can be made as "killed" whole cell products by physically or chemicaly killing the organisms. In many cases, important antigens related to disease production are released into the culture fluid as the bacteria grow, so the culture filtrate can be used as the vaccine after it is precipitated on aluminum hydroxide (a particulate material that also serves as an adjuvant). Disease producing bacteria can be modified by growing them in adverse conditions. In time this may result in living bacteria that can no longer cause disease. A living vaccine made this way would be regarded as an "attenuated live vaccine". More recently, bacterial vaccines are made by genetic engineering. The scientist identifies a protein that is important for the bacteria's disease producing activities. This could be something that enables the bacteria to bind or invade epithelial cells, something that the bacteria needs in order to grow rapidly or something the bacteria secretes that gives it an advantage in your body. The bacterial gene for this can be found and "cut out" of the bacterial genome so it can be used in a safe vector organism to produce the protein in large amounts. Or, the genetic engineer can insert an altered gene into the disease producing bacteria's DNA that will result in damage to its ability to make something needed for disease production. This is referred to as "knocking out" a gene. I know that living candidate Vibrio cholera vaccines have been made by knocking out genes that produce toxins that cause diarrhea or intestinal injury.

Viral vaccines like Jonas Salk's Polio vaccines were made by producing large amounts of disease producing virus in embryo cells and then killing the slurry of virus and proteins with formaldehyde (a denaturing agent). For Polio prevention, several inoculations of this kind of polio vaccine resulted in protection from Polio during epidemics. Another kind of Polio vaccine was made by Albert Sabin. He grew polio virus in tissue culture cells at abnormal temperatures and he selected virus colonies that made small "plaques" in the lawn of tissue culture cells. (plaques are "holes" made in continuous sheets of tissue culture cells by virus growing in a cell and spreading to neighboring cells and causing them to disintegrate). Presumably, small plaques represented slower or less spread of virus. Temperature sensitivity changes also made the virus poorly adapted to grow at normal body temperature. Both of these changes were thought to make the virus less able to produce disease. Fortunately, this was true for the Sabin Polio vaccine, a live-attenuated (living but less able to produce disease) vaccine, which was given by mouth as a droplet or dropped onto a sugar cube. The live-attenuated virus grew in the intestines and stimulated immunity. Live attenuated viral vaccines sometimes undergo mutations while they grow and can revert back to disease producing viruses. This would not be a problem for the person who got the vaccine because any mutation that formed would happen after immunity to the virus started to appear. This would prevent disease and it is possible that the mutation came at a time when it could best stimulate the kind of immunity really needed for complete protection. The risk of this attenuated vaccine was to younger children who might encounter the mutated virus shed in stool. There were some "secondary" cases of polio in family members of children getting the oral polio vaccine. Today, when polio is rare in the United States, this minor risk of acquiring polio from a family member who got the vaccine is one of the reasons officials are reconsidering use of the inactivated Salk polio vaccine. There also are candidate viral vaccines prepared by knocking out genes responsible for disease producing behavior or by determining the genes that encode important viral proteins so they can be used in genetic engineering vectors to produce protein vaccines that no longer have the ability to infect.
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Postby scottyiu » Fri Apr 14, 2006 2:39 pm

How do you "weaken" it?
This forum is so cool
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Postby kiekyon » Sat Apr 15, 2006 1:30 pm

vaccines can be produced from either live or dead organisms. "Live" vaccines can be better described as live attenuated vaccines. "Dead" vaccines are better described as inactivated vaccines.

Live attenuated vaccines are prepared by taking the causative agent and
performing a large number of passages in culture or sub-cultures in a
different animal species (example, a human virus might be passed in chick embryos). Passage of the agent, as described, can cause it to lose its ability to produce disease in the host species. Although the disease is
prevented, the agent can still multiply in the host species and this multiplication allows the production of a immune response. This reduction in disease production through passage is called attenuation. Live attenuated vaccines tend to produce longer lasting immunity than inactivated vaccines and the immunity tends to more closely resemble natural immunity.
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