LESSON 3: ANT-IVIRAL agents Flashcards
in humans and animals are preferably controlled by
immunization.
Viral infections
However, when a vaccine is not available, example for those major
viral diseases or emergence of a new virulent strain of virus,
antiviral chemotherapy
inhibit virus-specific events related to virus replication;
from preventing virus entry into host cells, interfering with uncoating, genome
replication or assembly to release of virus from host cells
Effective antiviral drugs
Classes of antiviral drugs:
- Immunomodulators:
- Ion-channel blocking compounds:
- Neuraminadase inhibitors:
- Antiviral drugs which inhibit viral genome replication
- Non-nucleoside polymerase inhibitors:
- Protease inhibitors:
In addition, the efficacy of antiviral chemotherapy is further complicated
by viral latency (ex:
(ex: herpesviruses)
produced by fibroblasts and other cell
ii. Interferon-β (IFN-β):
Type 1interferon : mediate the early immune responses to viral infections,
major examples
i.Interferon-α (IFN-α)
ii. Interferon-β (IFN-β
2 types of interferons:
a) Type 1interferons
b) Type 2interferon
enhance innate immune responses, indirect antiviral effects
by inducing cytokines prominently interferons
- Immunomodulators:
produced by mononuclear phagocytes
i. Interferon-α (IFN-α)
Neuraminidase
a) Example: (anti-influenza drugs
Oseltamivir and Zanamivir
Briefly, the presence of
amantadine interfere with the ion channel function of the —protein in the
nucleocapsid of the virus thus inhibits acid-mediated dissociation
M2 protein
prevents virus uncoating shortly after
endocytosis of virus by the host cell (
- Ion-channel blocking compounds:
Example of immunostimulating drugs to viral infections:
Imiquimod and
Inosine pranobex
or interferon-Ɣ (IFN-Ɣ) is produced by stimulated T cells
and NK cells.
b) Type 2interferon :
has antiviral activity against influenza A virus by
inhibiting an early step in the replication of the virus.
Amantadine
interfere with release of virus from host cells
Neuraminadase inhibitors:
is required to cleave sialic acid from the cell membrane of the
budding virions.
Neuraminidase
a) Example: Nucleoside analogue drugs such as
i.Acyclovir: used against herpesvirus
ii. Famciclovir: has inhibitory activity against herpesviruses, poxviruses,
papillomaviruses and adenoviruses
iii. Penciclovir:used against herpesvirus
Most of these drugs are
nucleoside analogues which inhibit viral polymerases, especially —-
by competing with natural substrates and incorporate into the growing DNA chain
where they often terminate elongation.
DNA polymerases,
active against cytomegalovirus
Ganciclovir:
anti-influenza drug
Ribavirin:
Example: Thymidine analogue
Ophthalmic solutions containing idoxuridine are used for
treating herpesvirus keratitis in animals
Idoxuridine
inhibit replication of viruses by binding
to the pyrophosphate binding site of the DNA polymerase to block binding of
nucleotides.
Non-nucleoside polymerase inhibitors
