Nucleic Acid-Based Vaccines

The principles for both DNA and RNA approaches are similar in nature. The in vitro model for this technology lies in the transformation of cells in culture with a plasmid that directs the synthesis of a vaccine antigen. After cells in vivo take up nucleic acid encoding vaccine antigens, the antigens can be secreted or associated with the cell surface in a way that triggers both humoral or cellular immune responses.

A comparison of the three types of vaccines is given in Table 1.

Property	Live Attenuated Virus Vaccine	Inactivated Virus Vaccine	DNA Vaccine
Route of administration	Injection, inhalation, or oral	Injection	Injection, gene gun
Amount of virus in vaccine dose	Low	High	Nil
Number of doses	Usually Single	Multiple	Single, or in prime-boost regimen
Need for adjuvant	No	Yes	No
Duration of immunity	Many years	More limited, several years	Not known
Antibody response	IgG, IgA (if mucosal route)	IgG	IgG
Cell-mediated response	Good	Generally modest	Good
Heat lability	Yes, for most viruses	No	No
Interference by prior antibody	Yes	Usually no	No
Side-effects	Occasional, local, or systemic	Occasional, local	Uncertain
Reversion to virulence	Rare	No	No
Use in pregnant women	Usually not advised	Yes	Yes
Cost	Low	High	Low
Potential hazards	Contaminating viruses	Vaccine-enhanced disease	Not known yet

References:

Plotkin’s Vaccines, 7^th Edition

Fenner and White’s Medical Virology, 5^th Edition