Final answer:
A researcher creating a vaccine by removing a virulence gene from a virus using genetic recombination techniques is producing a subunit vaccine. These vaccines use genetic engineering to expose the immune system to the essential antigens of a pathogen, ensuring safety and effectiveness without causing the disease.
Step-by-step explanation:
When a researcher uses genetic recombination techniques to remove a virulence gene from a virus, the resultant product is a type of vaccine known as a subunit vaccine. This is because such a vaccine contains only the essential antigens of a pathogen, which are produced by genetic engineering and do not include whole cells or the complete virus. The genetic engineering of these vaccines ensures that they are safer than other kinds of vaccines, like live or inactivated ones, as they only introduce the immune system to the key antigens without the risk of causing the disease.
Subunit vaccines can be created by inserting genes that code for the target antigens into a plasmid vector, followed by cultivating these in yeast cells or other hosts, to produce large quantities of the antigenic proteins. These proteins are then extracted and administered to patients, stimulating the immune system to produce antibodies. This form of vaccination effectively harnesses the body's immune response against the pathogen without the risk of an actual infection.