DNA Vaccines

One of the greatest achievements in the history of medicine has been the development of vaccination. The use of vaccines has saved more lives than all other medical procedures combined, and represents one of the highest points in civilization's technical accomplishments. Vaccines are used to mobilize the immune system to prevent or combat infectious disease caused by exposure to viruses, bacteria, or parasites.

A vaccine works by mimicking an infectious agent and inducing a protective immune response in the host, without actually causing the disease. Successful vaccination provides protection for individuals by making them immune to the disease, and it protects whole populations by hindering the spread of the infectious agent.

Historically, vaccines have consisted of formulations using live, noninfectious (attenuated) microbes that resemble the original pathogen; whole organisms that have been killed; or purified by-products of the infectious agent. More recently, some vaccines have used recombinant DNA technology to genetically engineer purified proteins from infectious agents.

All of these classic vaccines are based on the principle of using a protein to stimulate the immune system. In other words, the individual is immunized with a protein vaccine consisting of either a modified pathogen or some protein or proteins derived from that pathogen. When the immune system encounters a foreign protein (called an antigen), it mounts a two-pronged defense. It produces proteins called antibodies, which can bind and neutralize the antigen, and it produces specific immune cells, which work to eliminate those host cells that have been infected by the microbe. Thus our immune system is capable of producing two distinct Certain DNA vaccines have been tested on cattle. types of responses to combat infectious microbes: An antibody response and a cell-mediated response. Typically, vaccines activate only the antibody response to an infectious microbe.