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, 7th Edition
Fenner and White’s Medical Virology, 5th Edition
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