Development of antiviral medications is one of the most difficult problems in a therapy of infections. It is linked to the fact that DNA and RNA containing viruses are obligate intracellular parasites1. During replication process viruses modify and utilize biosynthesis process of the invaded cells of macroorganism. Therefore, it is hard to find a chemical compound which can selectively affect the virus without harm to the host cell. Some viruses (herpes simplex virus, varicella zoster virus) induce the production enzymes upon entry into the host cell, which are different from enzymes of the host cell. DNA-polymerase is an example. Acycloguanosine (acyclovir) phosphorylated to triphosphate upon entry into the host cell, inhibits herpes simplex virus DNA-polymerase much more than DNA-polymerase of the host cell. It also gets integrated into viral DNA. Ribavirin, converted to 5-triphosphate, specifically inhibits HIV RNA-polymerase. Azidothymidine (zidovudine) inhibits HIV reverse transcriptase. Anti-HIV peptides (saquinavir) selectively inhibits HIV proteases. Antiinfluenza medications, which inhibit viral neuraminidase, were discovered. Achievements listed above are quite promising in the process of development of new selective anti-viral medications.
Mode of action of antiviral agents can target different stages of virus-host cell interactions (Fig. 30.1).
Besides, entry of viruses into the body impels host cells to produce interferons, and stimulate humoral and cellmediated components of immune system. Viral proteins are powerful antigens and cause massive antibodies production, which neutralize viral activity. Thus, the creation of agents stimulating interferon production and antibodies secretion is a very perspective direction in the development of antiviral medications.