Treatment, Prevention and Control of Viral Diseases - L15

Question 1

Acyclovir is a pro-drug

True or False ?

Answer 1

True

Note:

Question 2

ZDV-triphosphate competes

True or False ?

Answer 2

False

Note: It is gDTP

Question 3

Vaccines produced by Serial Passage of viruses in heterologous host is a ______ vaccine.

A. Live-attenuated
B. Killed
C. Subunit

Answer 3

A. Live-attenuated

Note: In this case the virus is live (it is not inactivated) but as a result of serial passage in the heterologous host, it lost its virulence but retained its antigenicity and it can be used as a vaccine

– The word “Serial Passage” more applies to cell culture

Question 4

Quarantine and Isolation have the same meaning

True or False ?

Answer 4

False

Question 5

Autoclaving is primarily considered as a method of _______

A. Disinfection
B. Sterilization
C. Antisepsis

Answer 5

B. Sterilization

Note: By autoclaving normally all microbes are killed.

Question 6

b

Answer 6

b

Question 7

b

Answer 7

v

Question 8

Treating a viral disease is very 
difficult. There are three
 approaches
 for treating a viral disease. What are they ?

Answer 8

1. Antiviral Drugs
2. Immune system stimulation
3. Synthesize antibodies or administration of natural antiserum (antibodies)

Question 9

______ _________ Interfere with the ability of a virus to infiltrate a target cell or target different stages of replication/Synthesis of components required for replication of the Virus.

Answer 9

Antiviral Drugs

Question 10

Interferons, class of proteins that has antiviral effects and modulate functions of the immune system. Are considered what type of viral treatment ?

Answer 10

Immune system stimulation

Note: Interferons are glycoproteins

Question 11

________ is defined as the treatment of infectious diseases by drugs (chemical compounds) that are inhibitory or lethal to the pathogenic microbe.

A. Antibiotics
B. Antimycotics
C. Antimicrobial chemotherapy
D. Antifungal

Answer 11

C. Antimicrobial chemotherapy

Question 12

________ are types of medications that destroy or slow down the growth of bacteria.

A. Antibiotics
B. Antimycotics
C. Antifungal
D. Antiparasitics

Answer 12

A. Antibiotics

Note: also known as antibacterials

Question 13

_________ are medications used to treat fungal diseases.

A. Antibiotics
B. Antimycotics
C. Antifungal
D. Antiparasitics

Answer 13

B. Antimycotics

Question 14

_________ are a class of medications which are indicated for the treatment of parasitic diseases.

A. Antibiotics
B. Antimycotics
C. Antifungal
D. Antiparasitics

Answer 14

D. Antiparasitics

Question 15

Antiviral drugs are a class of medication used specifically for treating viral infections.

True or False ?

Answer 15

True

Note: Compared to antibiotics, there are only few effective antivirals available.

Question 16

Most agents that interfere with virus replication are toxic to the cell.

True or False ?

Answer 16

True

Note: Logical approach to devising antivirals that will interfere with virus replication without harming or causing minimal harm to the infected host cell.

Question 17

Antiviral chemotherapeutic agents are commonly used in veterinary practice.

True or False ?

Answer 17

False

Note: 1) High cost; 2) Species specific (virus and animal); 3) Absence of rapid techniques to allow use in acute infections 4) Difficulties encountered when it has low cytotoxicity

Question 18

Name several mechanisms on which Antivirals can act on different stages of the viral replication cycle.

Answer 18

1. Receptor binding
2. Cell entry
3. Uncoating
4. Nucleic acid and protein synthesis
5. Assembly
6. Release

They can also modulate the immune system

(insert pic)

Question 19

Acyclovir

important antiviral

Answer 19

Description:

• Antiviral activity primarily restricted to herpesviruses.
• Administered as a prodrug, inactive form.
• Requires virus enzymes in infected host cell to convert itself into active form, which then interferes with virus replication.

Treatment:

• > Herpesvirus infections in humans
• > Feline herpesvirus 1 induced corneal ulcers
• > Equine herpesvirus-1 induced encephalomyelitis

Mechanism of Antiviral effect:
In the cytoplasm:
1. Acyclovir is converted into Acyclovir monophosphate by Herpes virus Thymidine Kinase [TK] [enzyme synthesized ONLY by herpesviruses]
2. Acyclovir monophosphate is converted into Acyclovir diphosphate by Cellular Kinase [GMPK]
3. Acyclovir diphosphate gets another phosphate group added onto it by Cellular Kinase [NDPK] making it Acyclovir triphosphate
In the nucleus:
4. The two phosphates are cleaved from acyclovir-triphosphate to form acyclovir-monophosphate by herpes virus DNA polymerase
5. The herpes simplex’s DNA polymerase enzyme incorporates the acyclovir monophosphate into the growing DNA strand as if it were 2-deoxyguanosine monophosphate (a “G” base). Further elongation of the chain is now impossible. Viral DNA chain synthesis stops.
6. Also, competitive inhibition of Viral DNA polymerase, as acyclovir-triphosphate compete with dGTP for viral DNA polymerase

Other:
– Acyclovir is a synthetic nucleoside analog of deoxyguanosine. (Acyclovir has a structure which is chemically similar to guanine; but not identical)

– Acyclovir is Non-toxic to the uninfected host cell [cannot be incorporated into the host DNA; ONLY the viral DNA]

Mechanisms for Resistance:

1. Absent production of TK due to viral genome mutations
2. Decrease of TK production
3. Altered TK substrate specificity [TK gets phosphorylated instead of acyclovir]
4. Mutations in viral DNA polymerase - cause decreased binding of acyclovir-triphosphate to viral DNA polymerase

Question 20

What is the correct mechanism of action of Acyclovir ?

A. TK - GMPK - ACV - NDPK
B. ACV - TK - GMPK - NDPK
C. ACV - NDPK - TK - GMPK
D. GMPK - ACV - TK - NDPK

Answer 20

B. ACV - TK - GMPK - NDPK

Note: ACV = Acyclovir

Question 21

Amantadine

antiviral and anti-Parkinson drug

Answer 21

Description:

• Amantadine is a synthetic tricyclic amine of the adamantane family.
• Amantadine acts as both antiviral and anti-Parkinson drug.
• Amantadine inhibits replication of most strains of influenza A viruses by blocking uncoating of the virus.

Treatment:
- Influenza A viruses

Mechanism of Antiviral effect:
Primary Activity:
1. Blocks the M2 ion channel proteins on the influenza virus
2. It does this by clogging the M2 channel and preventing it from pumping protons into the virion.
3. Viral RNAs remain bound to M1 and cannot enter the nucleus. Virus replication is inhibited.
4. NO protons enter into the virus; pH cannot drop; Prevents viral replication
Secondary Activity:
1. In certain strains of influenza A virus, the pH changes that result from M2 inhibition alter the conformation of hemagglutinin during its intracellular transport later in replication and thus block the viral assembly also.

Other:
Has a specific structure [NH2 attached]

Mechanisms for Resistance:

1. Resistance to amantadine occurs by changes in amino acids that line the M2 channel. These changes prevent the drug from plugging the channel.
2. Strains become resistant to amantadine when there is mutations in influenza M2 ion protein

Question 22

The structure of Influenza virus, which is NOT correct ?

A. M1 (matrix protein)
B. M2 (matrix protein)
C. Lipid bilayer
D. HA (hemagglutination)
E. RNA polymerase
F. NA (neuraminidase)

Answer 22

B. M2 (matrix protein)

Note: Influenza viruses have M2 proteins but they are called “Ion Channel Proteins”