Experimental Zika Vaccine Shows Promising Early Results.
Vaccination consists of stimulating the immune system with an infectious agent, or components of an infectious agent, modified in such a manner that no harm or disease is caused, but ensuring that when the host is confronted with that infectious agent, the immune system can adequately neutralise it before it causes any ill effect. For over a hundred years vaccination has been effected by one of two approaches: either introducing specific antigens against which the immune system reacts directly; or introducing live attenuated infectious agents that replicate within the host without causing disease synthesise the antigens that subsequently prime the immune system. Recently, a radically new approach to vaccination has been developed. It involves the direct introduction into appropriate tissues of a plasmid containing the DNA sequence encoding the antigen(s) against which an immune response is sought, and relies on the in situ production of the target antigen. This approach offers a number of potential advantages over traditional approaches, including the stimulation of both B- and T-cell responses, improved vaccine stability, the absence of any infectious agent and the relative ease of large-scale manufacture. As proof of the principle of DNA vaccination, immune responses in animals have been obtained using genes from a variety of infectious agents, including influenza virus, hepatitis B virus, human immunodeficiency virus, rabies virus, lymphocytic chorio-meningitis virus, malarial parasites and mycoplasmas. The field of DNA vaccination is developing rapidly. Vaccines currently being developed use not only DNA, but also include adjuncts that assist DNA to enter cells, target it towards specific cells, or that may act as adjuvants in stimulating or directing the immune response. Many aspects of the immune response generated by DNA vaccines are not understood. However, this has not impeded significant progress towards the use of this type of vaccine in humans, and clinical trials have begun. It is the introduction of this new DNA vaccine that is being referred to in this article on Zika. Credit: WHO.
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