23 - Antiviral medicines, interferons, interferon inducers and immune sera in therapy

Question 1

What should be included in the topic

Answer 1

• Defense against viral diseases, types of defense
• Resistance of viruses to environmental conditions
• Disifectants and inactivating agents
  
  • Aim
  • Disinfectants
  • Inactivating agents
• Antiviral medicaments
  
  • Effects
  • Problems
  • Nucleoside analogues
  • Non-nucleoside RT inhibitor
  • Protease inhibitor
  • Favipiravir
  • Other antiviral drugs
    
    • Methisazone
    • Amantadine, Rimantadine
    • Neuraminidase inhibitors
• Interferon inducers
• Immune sera in therapy

Question 2

Give the types of defense against viral diseases

Answer 2

1. General defense
   
   • ​Surveillance and control
     
     • Monitoring of virus activity
     • Morbidity and morality data
     • Quarantines, restrictions, stamping out
   • Animal hygine
     
     • Feeding and keeping conditions
2. Specific defense
   
   • ​In the environment
     
     • Disinfectants
   • In the host organism
     
     • Antiviral drugs
     • Interferons
     • Immune sera
     • Vaccines
   • Eradication

Question 3

Resistance of viruses to the environmental conditions

Answer 3

• Dehydration: Envelopes viruses
• High temperature: Protein denaturation
• Radiation (UV, gamma): Damage of nucleic acids
• Ionic environment:
  
  • Optimal: pH 6.5 - 7.5
  • Limits: pH 2 - 12

Question 4

Disinfectants and inavtivating agents

Aim

Answer 4

• Virus inactivation in the environment
• Vaccine production - preservation of antigenicity

Question 5

Disinfectants and inavtivating agents

Name some disinfectiants

Answer 5

• Acids and bases
• Oxidants
• Halogenids
• Protein dentaturants
• Detergents, lipid solvent
• Aldehydes

Question 6

Disinfectants and inavtivating agents

Give the inactivating angents

Answer 6

• 0.001% formaldehyde
• Nucleic acid denaturants

Question 7

Antiviral medicaments

Effects

Answer 7

• Inhibition of virus replication
• Decreasing the virus shedding
• Localization of the infections

→ But the infection remains

Question 8

Antiviral medicaments

Problems

Answer 8

• Close contact between virus and cell activity
  
  • Effective drugs are often toxic for the cells, so specific antigens are needed
• High viral mutation ratio → resistance
• Rarely used in veterinary practice
  
  • Expensive
  • Narrow spectrum
  • Resistance occurs

Question 9

Antiviral medicaments

List the antiviral medicaments

Answer 9

• Nucleoside analogues
• Non-nucleoside RT inhibitor
• Protease inhibitor
• Favipiravir
• Other antiviral drugs:
  
  • Methisazone
  • Amantadine, Rimantadine
  • Neuraminidase inhibitors

Question 10

Antiviral medicaments

Nucleoside analogues

Answer 10

First generation nucleoside analogues

• ​Incorporates into the nucleic acid
• Toxic - so external use only
• Riboflavin
  
  • ​Guanoside analogue
  • Works against:
    
    • Orthomyxoviruses
    • Bunyaviruses
    • Arenaviruses

Second generation nucleoside analogues:

• Activated by virus specific enzymes
• More selective to viral polymerase than to cellular
• Safer than first generation
• Acyclovir
  
  • ​Guanine derivate
  • Selective to viral polymerase
  • Puts guanidine into DNA → chani termination
  • Works against:
    
    • Herpes simplex virus 1
    • Herpes simplex virus 2
    • Varivella-Zoster virus
• Zidovudine
  
  • ​Reverse transcriptase inhibitor
  • Reverse transcriptase has no repair activity
  • Competitive to dTTP
  • Works against retroviruses (HIV, etc…)

Question 11

Antiviral medicaments

Non-nucleodise RT inhibitors

Answer 11

• Directly inactivates RT
• Active against HIV-1
• Used in combination therapies

Question 12

Antiviral medicaments

Protease inhibitors

Answer 12

• Inhibits retroviral protease
• Fits into the active center of the enzyme
• The cleavage of the precursor polyprotein is inhibited
• Effective against HIV

Question 13

Antiviral medicaments

Favipiravir

Answer 13

• RdRp inhibitor
• Lethal mutations
• Broad spectrum, effective against alot of viruses:
  
  • Othomyxoviruses
  • Flaviviruses
  • Alphaviruses
  • Arenaviruses
  • Bunyaviruses
  • Enteroviruses
  • Filoviruses

Question 14

Antiviral medicaments

Other antiviral drugs

Answer 14

Methisazone:

• Viral polymerase inhibitor
• Works against pox-infections

Amantadine, Rimantadine:

• Ion-channel inhibitor
• Uncoating is defected
• Against influenza

Neuraminidase inhibitors:

• Oseltamivir
• Zanamivir
• Against influenza

Question 15

Interferon inducers

Answer 15

• Advantages:
  
  • High efficacy
  • Not antigen specific
• Disadvantages:
  
  • Expensive (species-specific)
  • Progressive hypo-responsiveness
  • Short-term effect
  • Parenteral administration
  • → Presently rarely used in veterinary practice

Additional information about interferons:

• Interferons show a wide range of applications due to their antiviral, antibacterial, antitumor and inflammaroty activity
• Interferons are proteins made and relased by host cells in response to pathogens such as bacteria, virus, etc.
• Interfernos are named by their ability to inferfere with replication of viral genome
• They activate immune cells by increasing expression of antigens

Question 16

Immune sera in therapy

Answer 16

Immune sera and purified immunoglobulins

• Advantages:
  
  • Passive immunization
• Disadvatages:
  
  • Short term protection
  • Danger of serum-sickness or anaphylaxis
  • Large animals: enormous doses
  • High costs (hyperimmunization)
• Mainly in pet practice
• Used against:
  
  • Canine distemper virus
  • Canine parvovirus
  • Canine adenovirus 1
  • Feline panleukopenia
  • Feline rhinotracheitis
  • Goose parvovirus (Derzsy’s disease) - goslings