Intranasal DNA Vaccine for Protection against Respiratory Infectious Diseases: The Delivery Perspectives

Xu, Yingying; Yuen, Pak-Wai; Lam, Jenny Ka-Wing

Another safety issue of DNA vaccines is related to the development of anti-DNA immune responses. Animal studies showed that there is no increase in anti-nuclear or anti-DNA antibodies after DNA vaccination. In clinical trial studies, signs and symptoms of autoimmunity, and the markers of autoimmunity are sometimes monitored in the human subjects. There has been no evidence that autoimmunity is associated with DNA vaccines [5, [37] [38] [39] . It has been suggested that proper purification of E. coli can effectively prevent pathogenic anti-DNA antibody production [2, 40] . Antibiotic resistance is another issue related to DNA vaccines. Typically, large-scale manufacture of plasmid DNA involves the use of antibiotic-resistant marker. There is a safety concern that resistance to the same antibiotic might be introduced. In response to this issue, antibiotic-resistance genes in DNA vaccine should be restricted to those that are not used to treat human infections. Alternatively, the use of antibiotic-resistance genes should be avoided completely [41] . Another concern of DNA vaccines is the development of tolerance to the encoded antigen, which appears to be age-related. Newborns have immature immune system and are more likely to develop tolerance rather than protection when exposed to foreign antigens. In contrast, immunity instead of tolerance occurred when DNA vaccines are administered to young animals [42] [43] [44] .