A Primer on Antiviral Agents
The world of antiviral drugs is rapidly changing with over 20 antiviral agents and 25 antiretroviral agents currently approved by the US Food and Drug Administration. Key to appropriately utilizing these agents is an understanding of the generic viral life cycle and the places points in that cycle where antivirals can act.
To simplify this, there are 2 major factors that distinguish viruses:
DNA vs RNA viruses; and
Envelope vs nonenvelope viruses.
Viruses work by hijacking the host cell machinery to manipulate cellular proteins in order to replicate. Viruses bring with them their own replication and packaging, but everything else they borrow from host cells. While not an absolute distinction, most DNA viruses enter the host cell nucleus, whereas RNA viruses stay in cytoplasm.
Figure 1. Viral life cycle.
Figure courtesy of Paul Krogstad, University of California, Los Angeles.
During the viral life cycle, a virus traffics in, binds to its receptor, enters, uncoats, makes its own nucleic acids and proteins, and then reassembles before releasing into the host system. That pretty much applies to all viruses.
Antiviral agents target several places within this process.
Figure 2. Sites of antiviral drug action.
Figure courtesy of Paul Krogstad, University of California, Los Angeles
It is important to emphasize that the viral life cycle results in the ultimate release of new virus. Therefore, a cell that is infected is generating a lot of virions. Virology should be thought of in terms of total numbers of virus. An antiviral agent that is 99.9% effective at reducing virus will leave 0.01% of the infected cells, and these infected cells continue to make new virions. If the original infection caused 1 billion new virions to be produced, 0.01% will continue to produce 1 million new virions, which is enough to generate symptoms in a patient. The best treatment for a viral infection, therefore, is to prevent a cell from being infected. Once a cell is infected and generating new virions, an antiviral must be extremely potent in order to arrest the infection.
Medscape Infectious Diseases © 2011 WebMD, LLC
Cite this: Ravi Jhaveri. A Brief Primer on Antivirals in Children - Medscape - Jul 18, 2011.