Posted by jayaram in Introduction
Traditional procedures of vaccination have used purified components of an infectious organism, dead or attenuated intact cells or viruses, to provide individuals with active immunity by eliciting production of specific antibodies. Many have been successful in providing protection against diseases such as polio, smallpox, whooping cough, typhoid fever, and diphtheria.
Recently, a new approach to immunization has been explored that uses transparent DNA. The source of this DNA is typically a bacterial plasmid that is free of bacterial proteins. This DNA can enter a number of cell types and can be expressed by host cells. Sequences encoding antigenic portions of a pathogen are encoded in this DNA, and protein products are synthesized using cellular transcription and translation machinery. In this respect, DNA vaccines act much like viruses. However, these DNAs contain only a very limited set of genetic information and cannot become infectious. The mechanisms of uptake and induction of the immune response are not yet clear. However, promising results have been obserbved against a nuimber of pathogens including viruses, bacteria and parasitic microorganisms. This approach holds great promise for development of effective vaccines against a number of intractable diseases including HIV/AIDS, tuberculosis, and malaria.