About this Research Topic
Vaccines are one of the greatest advances in medicine, with drastic reduction of mortality worldwide. DNA vaccines are based on plasmid DNA encoding specific antigens, and were once considered third-generation vaccines. Over the last three decades, this technology has been applied for investigation of prevention or treatment of infections caused by different pathogens, as well as for the treatment of cancer, allergies and autoimmune diseases.
One of the advantages of DNA vaccines is the in vivo expression of the antigen, which avoids incorrect folding of the recombinant protein and allows post-translational modifications that may influence the immune response it elicits. Studies with different animal models indicate that DNA vaccines are able to induce broad humoral and cellular immune responses, with activation of both TC4+ and TC8+ cells. Additionally, plasmid DNA can be easily constructed and manipulated by genetic engineering, are stable at room temperature, and hence, large-scale production is available at lower cost comparing to traditional vaccines. This approach is also a robust technology for screening of protective antigens and expression of several proteins simultaneously, mediated by the same vector or in a mixture with different plasmids.
Due to the initial promising reports of DNA vaccines in small animal studies, clinical trials were conducted with human volunteers. Unfortunately, results of these trials were disappointing. It revealed that, although safe, the DNA vaccines were poorly immunogenic in humans.
One of the main reasons for this lack of immunogenicity is the low efficiency of transfection in humans and non-human primates. Researches have then focused on developing new strategies to overcome this obstacle, through for example, immunization by electroporation. Other efforts to increase the efficacy of DNA vaccines also include codon optimization to enhance antigen expression, the use of adjuvant as CpG oligonucleotides, co-administration of plasmids encoding cytokines, co-stimulatory receptors, etc. In addition, DNA vaccines were tested in combination with several other strategies, such as inactivated or live-attenuated virus and recombinant subunit vaccines, in prime-boost regimen or with simultaneous immunization. These studies revealed successful results by improving the elicited immune response and activating different branches of the immune system.
Yet, there are currently no approved DNA-based vaccines for human use. However, some DNA vaccines have been approved for veterinary use, such as: West Nile Virus in horses, Infectious Hematopoietic Necrosis Virus in salmon, growth hormone in swine, and canine melanoma. Thus, DNA vaccines is still an important issue in the field of vaccinology and requires further studies.
Please note that, as a response to the current global pandemic, this Research Topic will now welcome submissions reporting original data relating to the development of DNA vaccines for the prevention or treatment of COVID-19.
This Research Topic welcomes the submission of Original Research Articles, Reviews, Opinion and Perspective articles towards DNA vaccines for prevention against pathogens, treatment of different diseases, understanding the mechanisms involved in activation of the immune responses elicited by these vaccines, improvement of the in vivo transfection and antigen expression.
Keywords: dna vaccines, in vivo expression, plasmid dna, immunogenicity, transfection, COVID-19
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