LESSON 3: ANT-IVIRAL agents

Question 1

in humans and animals are preferably controlled by
immunization.

Answer 1

Viral infections

Question 2

However, when a vaccine is not available, example for those major
viral diseases or emergence of a new virulent strain of virus,

Answer 2

antiviral chemotherapy

Question 2

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

Answer 2

Effective antiviral drugs

Question 3

Classes of antiviral drugs:

Answer 3

1. Immunomodulators:
2. Ion-channel blocking compounds:
3. Neuraminadase inhibitors:
4. Antiviral drugs which inhibit viral genome replication
5. Non-nucleoside polymerase inhibitors:
6. Protease inhibitors:

Question 3

In addition, the efficacy of antiviral chemotherapy is further complicated
by viral latency (ex:

Answer 3

(ex: herpesviruses)

Question 4

produced by fibroblasts and other cell

Answer 4

ii. Interferon-β (IFN-β):

Question 4

Type 1interferon : mediate the early immune responses to viral infections,
major examples

Answer 4

i.Interferon-α (IFN-α)
ii. Interferon-β (IFN-β

Question 4

2 types of interferons:

Answer 4

a) Type 1interferons
b) Type 2interferon

Question 4

enhance innate immune responses, indirect antiviral effects
by inducing cytokines prominently interferons

Answer 4

1. Immunomodulators:

Question 5

produced by mononuclear phagocytes

Answer 5

i. Interferon-α (IFN-α)

Question 6

Neuraminidase
a) Example: (anti-influenza drugs

Answer 6

Oseltamivir and Zanamivir

Question 6

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

Answer 6

M2 protein

Question 7

prevents virus uncoating shortly after
endocytosis of virus by the host cell (

Answer 7

2. Ion-channel blocking compounds:

Question 7

Example of immunostimulating drugs to viral infections:

Answer 7

Imiquimod and
Inosine pranobex

Question 8

or interferon-Ɣ (IFN-Ɣ) is produced by stimulated T cells
and NK cells.

Answer 8

b) Type 2interferon :

Question 9

has antiviral activity against influenza A virus by
inhibiting an early step in the replication of the virus.

Answer 9

Amantadine

Question 10

interfere with release of virus from host cells

Answer 10

Neuraminadase inhibitors:

Question 11

is required to cleave sialic acid from the cell membrane of the
budding virions.

Answer 11

Neuraminidase

Question 12

a) Example: Nucleoside analogue drugs such as

Answer 12

i.Acyclovir: used against herpesvirus
ii. Famciclovir: has inhibitory activity against herpesviruses, poxviruses,
papillomaviruses and adenoviruses
iii. Penciclovir:used against herpesvirus

Question 12

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.

Answer 12

DNA polymerases,

Question 13

active against cytomegalovirus

Answer 13

Ganciclovir:

Question 13

anti-influenza drug

Answer 13

Ribavirin:

Question 14

Example: Thymidine analogue
Ophthalmic solutions containing idoxuridine are used for
treating herpesvirus keratitis in animals

Answer 14

Idoxuridine

Question 14

inhibit replication of viruses by binding
to the pyrophosphate binding site of the DNA polymerase to block binding of
nucleotides.

Answer 14

Non-nucleoside polymerase inhibitors

Question 15

ex. (against herpesvirus, HIV, hepatitis B virus)

Answer 15

Foscarnet

Question 15

: used against HIV proteases

Answer 15

6. Protease inhibitors

Question 16

6. Protease inhibitors: used against HIV proteases
   a) Examples:

Answer 16

Saquinavir, indinavir, ritonavir, nelfinavir, and amprenavi

Question 17

are highly selective and usually target a
specific viral protein, viruses can readily become resistant through point mutations in
the virus genome which often limits the usefulness of antiviral drugs.

Answer 17

antiviral compounds

Question 18

may involve the selection
and use of the antiviral compounds, drug concentration at the site of infection, initial
virus susceptibility to the treatment, inherent characteristics of the invading virus and
the immune status of the host.

Answer 18

Development of resistance, a “multifactorial process”