Final answer:
Genetically engineered vaccines can be created by all listed methods, which include removing virulence genes from a pathogen, adding those genes to a non-virulent organism, and purifying part of the pathogen to use as a vaccine. These methods utilize recombinant DNA technology to produce antigens that stimulate an immune response without an actual infection.
Step-by-step explanation:
Genetically engineered vaccines can be created by all of the listed responses:
- Removing virulence genes from a pathogen
- Adding virulence genes from a pathogen to a non-virulent organism
- Purifying a specific subunit of a pathogen
Recombinant DNA technology allows the creation of subunit vaccines like the one for hepatitis B, produced by inserting a gene for a hepatitis B surface protein into yeast. The hepatitis B antigen is then purified from the yeast cultures and used as a vaccine. Additionally, virulence genes can be excised from pathogens, modified, and introduced into the non-virulent vaccines, which will express surface antigens that block the adherence of virulent bacteria.
Recombinant DNA is also utilized in the formulation of vaccines, which involve introducing these genes into an organism to generate the required antigens. Production of vaccines using such genetic engineering techniques is key in developing immunity against various diseases without the need to use weakened or live pathogenic organisms.