Prevention and treatment of viral disease Flashcards
What is prophylaxis?
Preventing disease before the aetiologic agent is acquired, by vaccination or giving drug before infection
What is therapy?
Treating the disease after the host has been infected
TRUE OR FALSE:
Antivral drugs are prophylactic
FALSE
Antiviral drugs = therapeutic
Vaccines = prophylactic
What are the different types of viral vaccines?
- Live attenuated
- Inactivated
- Fractionated (purified subunit)
- Cloned
Why is it difficult to develop drugs which selectively act against viral infections?
Viruses use many of the same pathways as humans for protein production = hard to find something that is selectively toxic
What is a common therapy for viral infections?
Antivral drugs
What is attenuation?
Using an alternative form of the virus that is still alive but with no pathological effects
Describe how a virus is attenuated to make a live virus vaccine
- Pathogenic virus is isolated from a patient and grown in human cultured cells
- The cultured virus is used to infect monkey cells
- The virus acquires many mutations that allow it to grow well in monkey cells
- The virus no longer grows in human cells and may be a candidate for a vaccine
What are the advantages and disadvantages of live vaccine?
ADVANTAGES:
- Rapid broad, long-lived immunity
- Dose sparing
- Cellular immunity
DISADVANTAGES:
- Requires attenuation
- May revert
What are the advantages and disadvantages of inactivated vaccine?
ADVANTAGES:
- Safe
- Can be made from wild type virus
DISADVANTAGES:
- Frequent boosting required
- High doses needed
What types of vaccines are available for influenza?
- Inactivated virus or HA subunit
- Live attenuated vaccine
What types of vaccines are available for poliovirus?
- Salk = inactivated vaccine
- Sabin = live attenuated vaccine
TRUE OR FALSE:
There is a vaccine for rotavirus
TRUE
Rotarix = live attenuated rotavirus vaccine
TRUE OR FALSE:
A vaccine for shingles has not yet been discovered
FALSE
Live attenuated vaccine similar but distinct from the chickenpox vaccine
TRUE OR FALSE:
The HPV vaccine is so far the only anticancer vaccine available in the UK
FALSE
There are vaccines for Hep B and Papillomavirus
How can people with viral infections be treated?
- Interferons - induce the host’s natural antiviral response
- Antiviral drug with specific antivral activity
- Treatment that alleviate symptoms but do not inhibit virus replication
What do most antiviral drugs target?
- Viral enzymes (often act as substrate analogues)
- Nucleoside analogues for cancer-like drugs
What type of antiviral drug is acyclovir?
Nucleoside analogue (inhibits viral replication by chain termination)
Describe how nucleoside analogues (e.g. acyclovir) are used as antiviral drugs
- Modified nucleoside (lacks 3’ -OH) incorporated into DNA
- Prevents phosphodiester bond formation = chain termination
- Highly specific
- Only activated inside virus infected cells
- High affinity for viral DNA polymerase than for host cell polymerase
How do antivirals target influenza virus replication?
- Neuraminidase = enzyme on the outside of influenza virus
- Substrate = sialic acid
- Drugs Relenza and Tamiflu competitively inhibits neuraminidase
Name some stages in the life cycle of viruses which could potentially allow therapeutic intervention
- Virus entry
- Early stages of infection (e.g. transcription with reverse transcriptase)
- Integration of virus DNA into host cell’s DNA
- Processing of protein for virus
