Antivirals Flashcards
What is the structure of a virus ?
It has a nucleic acid core surrounded by capsid ring consist of capsomere which are together known as nucelocapsid and they have a lipoprotein envelope.
What are enveloped viruses ?
These are viruses with a host cell derived lipid bilayer. examples are SARS Covid 1 and 2, MERS-coV, Alpha virus, Hep C and Zika virus.
What are non-enveloped viruses ?
They do not have spike proteins and host cell derived lipid bilayer examples are Hep A and E, Norovirus, adenovirus and astrovirus.
What are the stages of viral infection?
A) binding stage in which virus attaches to the cell surface.
B) Penetration- Viral DNA is injected into the cell and the viral coat remains outside.
C) Replication- Nucleic acid is replicated in host cell.
D) Synthesis- new protein coats are synthesised within the cell.
E) Assembly- Matured virons are assembled within the cell.
F) Release- The cell ruptures and releases matured viral particles.
Why is viral infections are only treated when the patient is symptomatic ?
The currently available anti-virals are virostatic drugs that are only effective while the viruses are replicating during symptomatic infection.
What are the different classes of anti virals ?
- Reverse Transcriptase Inhibitors
- Protease Inhibitors
- DNA Polymerase Inhibitors
- Inhibitors of Viral Coat Disassembly and
Neuraminidase Inhibitors - Biopharmaceutical Antiviral Drugs
How does HIV replicate ?
HIV replicates by converting its single-stranded
RNA into double stranded DNA which is achieved
by enzyme reverse transcriptase. The DNA is then
incorporated into host DNA of the cell.
What are the two types of reverse transcriptase inhibitors ?
(1)Nucleoside Reverse Transcriptase Inhibitor
(NRTI)
(2) Non-nucleoside Reverse Transcriptase
Inhibitor( NNRTI)
What is the action of NRTIs ?
The nucleoside binds to the DNA chain (of the host) and blocks the reverse transcriptase enzyme from adding another nucleotide. This terminates the viral DNA chain, preventing the viral
DNA from being incorporated into host cells DNA.
How are NRTIs administered and what are the examples ?
They are administered in combination. The commonly available combinations are
1) Tenofovir disoproxil fumarate-emtricitabine.
2) Abacavir-lamivudine
3) Tenofovir alafenamide-emtricitabine.
What are the side effects of NRTIs ?
- Early in treatment adverse effects may include anorexia, nausea, vomiting, headache, dizziness, malaise and myalgia.
- More serious side effects are anaemia and neutropenia, more common with high doses and advanced disease.
What is the action of Non-nucleoside Reverse Transcriptase Inhibitors (NNRTI’s)?
They act by inhibiting the enzyme reverse transcriptase. Examples are Efavirenz and Nevirapine.
What are the side effects of NNRTis ?
*Rash is common in first two weeks gastrointestinal side effects, hepatitis and pancreatitis reported.
*
What is the NNRTI with teratogenicity ?
Efavirenz
how does protease inhibitors work in HIV ?
They act by inhibiting the HIV viral proteases which are necessary for splitting the long polyproteines into short functional proteins. They are used in combination with reverse transcription inhibitors.
