Gene therapy for infectious diseases
Two different strategies for the treatment of infectious diseases are being explored. Both strategies involve the use of genetically manipulated cells. (i) The first strategy termed intracellular immunization is designed to render cells resistant to viral replication, thus limiting the spread of virus. (ii) The second strategy termed genetically engineered vaccines or DNA vaccines, makes use of genetically modified cells expressing viral gene products to enhance antiviral cellular immune responses.

Genetically engineered vaccines (also called DNA vaccines).
The approach involving genetically engineered vaccines, can induce production of either the antibodies or the Cytotoxic T cell receptors. Introduction of genes that encode T cell receptors has been considered a better alternative. The above resistance genes or the gene vaccines need to be delivered to hematopoietic target cells of the patient and this may be achieved using either the retrovirus based gene transfer systems or the vectors based on adeno associated virus (AA V). The advantages and disadvantages of using these vectors have been discussed elsewhere.

The efficacy and safety of the use of resistance genes or the genes encoding T cell receptors for gene therapy have been tested in immortal cell lines and in animal models, but both these systems have their limitations that need to be dealt with, before clinical trials on human subjects can be conducted.