18.4 How safe are DNA vaccines

Usually DNA vaccines are granted safe for both patient and environment. So far limited local reactivity at the injection site is the only drawback in the studies done. However due to the use of genetic vaccines there is a potential threat that the genome of the plasmid may get integrated into host genome of somatic cells and may lead to the production of transformed cells or oncogenes. To evaluate the potency of the associated risk, the parameter generally set is to compare the integration rate of pDNA with the spontaneous mutation frequency of autologous genes.This mutation rate may vary from person to person but overall, 2 x10 -6 spontaneous gene-inactivating, mutations per gene is usually approved as the standard value.There has been no evidence of elaborated studies carried out for genomic integration of DNA vaccines in humans which might be partly due to hurdles to obtain a biopsy from the administration site. However such studies have been carried out in many lab animals and all these studies have shown that the integration rates are always several folds less than the spontaneous integration rate.

18.5 Secondary role of DNA vaccines

Although DNA vaccines are still not exposed to human population openly but it has many other roles to carry out. It may be because the plasmid DNA can be used in vitro or in vivo. This property of DNA vaccines enables them to design monoclonal and polyclonal antibodies. Other experiments that require the use of DNA vaccines are the making of Knock-out mice models and also for developing DNA vaccine libraries to use them to know which genes encode protective antigens without any info about its corresponding protein.

18.6 RNA vaccines

RNA vaccines have been known in the field of vaccine development is quite well known. Over the past 25 years, many clinical trials of DNA in the form of plasmid and viral vector based vaccines have showed us a safe and efficacious way to deliver many foreign antigens. Yet, plenty and satisfactory potency for general efficacy in humans has remained elusive for DNA and RNA vaccines and the practicality of repeated use of viral vectors has been compromised by anti-vector immunity. RNA vaccines, including those based on mRNA and self-amplifying RNA replicons, have the tendency to surpass the restrictions of plasmid DNA and viral vectors. Possible difficulties related to the cost and feasibility of synthesizing RNA vaccines are being addressed, increasing the likelihood that RNA-based vaccines will be commercially available. Proof of concept for RNA vaccines has been shown in humans and the prospects for further progress into commercial products are very motivating.

18.7 Conclusion

The brief study done here indicates that the science of DNA vaccines is spreading rapidly with second generation formulations, delivery vehicles and a promising approach towards the development of new vaccines and immunotherapeutics. Their role has witnessed an encouraging participation as research tools and diagnostics. Further it is expected that with the ongoing human trials and biological engineering of genomes many emerging and fatal diseases will disappear totally.

Genetic Adjuvant A genetic adjuvant is a protein with adjuvant properties that is encoded by the pDNA together with the antigen and hence co-expressed with the antigen, enhancing the immune response towards this antigen.