VACCINES AND IMMUNIZATION

Reearch Articles

Individuals who suffer from an infectious disease, caused by a virus or bacterium etc, are usually resistant to the pathogen or evidence milder disease symptoms upon re-exposure to the parasite. This is due to the presence of pathogen-specific memory T-cells and B-cells that developed as a consequence of an immune response to the pathogen upon primary exposure. When exposed secondarily, the immune response is robust and the parasite is quickly eliminiated. Also, in the absense of an active immune response, as might be the case in infants, protection from an infectious agent is achieved via antibodies transferred, in this case, form mother to infant trans-placentally or in milk. Antibobies can be given to an individual as well to inactivate a toxin produced by a pathogen, venom from a insect or snake bite, or for short term protection from an infectious disease.

Thus, the goals of vaccine development and immunization are to find a suitable foreign antigen(s) that will elicit a long term protective immune response or antibodies that will be immunologically protective in the short term. The former is called active immunization; the latter passive immunization.

In addition to the use of live attenuated strains, inactivated/killed strains, and components of the pathogen for use as a vaccine, the techniques of molecular genetics are being used to produce new recombinant vaccines: immunodominant antigens can be cloned, produced in large quantities and purified; antibodies can be "humanized" via fusion proteins containing a V region generated from one species with a C region human isotype; and, vectors such as vaccinia virus, adenovirus, or canarypox virus carrying immunogenic DNA sequences from the pathogen of interest. Also, DNA vaccines are under development.