Antivirals Flashcards
What are viruses?
Viruses are non-living particles composed of nucleic acid (RNA or DNA) enclosed in a protein coat called a capsid. They lack organelles, cell membranes, and walls, and depend entirely on a host cell for replication.
What are the types of viral nucleic acids?
Viral nucleic acids can be single-stranded or double-stranded RNA or DNA. RNA viruses are generally more prone to mutation than DNA viruses.
How do viruses infect host cells?
Viruses attach to specific host cell surface receptors, enter the cell via endocytosis or membrane fusion, uncoat to release genetic material, replicate using host machinery, assemble into new virions, and release via lysis or budding to infect other cells.
What are common pathogenic viruses?
Examples include Filoviridae (Ebola), Influenza virus, Hepatitis B and C viruses, HIV, Herpes Simplex Virus (HSV), Varicella Zoster Virus (chickenpox and shingles), and Human Papillomavirus (HPV).
What are the main targets for antiviral drugs?
Antiviral drugs can target attachment to host cells, uncoating, synthesis of viral mRNA, replication of viral RNA or DNA, translation of viral proteins, protein maturation, and release of new virions.
How do amantadine and rimantadine work?
These drugs block the M2 ion channel protein involved in viral uncoating, preventing the disintegration of the influenza A capsid and subsequent replication.
What are synthetic nucleoside analogues?
These are pro-drugs phosphorylated inside cells to their active triphosphate forms, which inhibit viral enzymes like DNA polymerase, reverse transcriptase, or RNA polymerase, or cause chain termination by incorporation into viral DNA or RNA.
How does acyclovir work?
Acyclovir is a nucleoside analogue that inhibits viral DNA polymerase by mimicking deoxyguanosine triphosphate (dGTP). It selectively incorporates into viral DNA, causing chain termination. It has a higher affinity for viral DNA polymerase than cellular DNA polymerase.
What is ganciclovir used for?
Ganciclovir treats cytomegalovirus (CMV) infections. It is phosphorylated by a CMV-specific viral kinase encoded by the UL97 gene, making it highly effective against CMV.
What are interferons and how do they work?
Interferons are host cytokines that inhibit viral penetration, translation, transcription, protein processing, maturation, and release by inducing intracellular antiviral responses. They are used to treat chronic hepatitis B and C, Kaposi’s sarcoma, herpes, and CMV.
What are neuraminidase inhibitors?
These drugs, like oseltamivir (Tamiflu) and zanamivir (Relenza), inhibit neuraminidase, an enzyme required for the release of influenza virions from infected cells, stopping the spread of the virus.
What is the mechanism of action of neuraminidase inhibitors?
They prevent cleavage of sialic acid residues on the host cell surface, trapping influenza virions and preventing their release and spread.
What is SARS-CoV-2 and how does it infect cells?
SARS-CoV-2 is a single-stranded + sense RNA virus that attaches to the angiotensin-converting enzyme 2 (ACE2) receptor on human cells, allowing entry and replication.
What treatments are available for COVID-19?
Treatments include antiviral drugs (e.g., molnupiravir, remdesivir), monoclonal antibodies (e.g., casirivimab/imdevimab), anti-inflammatory drugs (e.g., dexamethasone), and immunomodulators (e.g., baricitinib), authorized under Emergency Use Authorization (EUA).
What is the difference between viruses and bacteria?
Viruses are non-living, require a host to replicate, and lack organelles, cellular machinery, or a cell wall. Bacteria are living cells with the ability to reproduce independently and have cellular structures like ribosomes and cell walls.
Why is targeting viruses challenging?
Viruses rely on host cells for replication, making it difficult to target them without damaging host cells. High mutation rates also contribute to resistance and treatment challenges.
