Antiviral Drugs Mechanisms of Action, Animation

(USMLE topics) Viral life cycle and antiviral drug targets. Attachment and entry inhibitors, uncoating inhibitors, nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs), integrase inhibitors, DNA polymerase inhibitors, protease inhibitors, neuraminidase inhibitors and antisense therapy.
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Antiviral drugs are medications used to treat viral infections. Because viruses replicate entirely inside host cells using the host’s machinery, it is difficult to develop drugs that affect viruses without also harming the host. Antiviral drugs do not inactivate or kill viruses, they merely inhibit viral reproduction by interfering with a certain stage of the virus life cycle.
A virus is composed of a genome, DNA or RNA, wrapped inside a protective protein coat, called a capsid. Most animal viruses also have an additional lipid membrane, called an envelope, with protein spikes that serve to attach to host cells.
A viral life cycle typically consists of the following steps:
- attachment to host cell receptor, followed by viral entry: via endocytosis, membrane fusion, or both.
- release of viral genome, also known as uncoating,
- replication of viral genome,
- synthesis and processing of viral proteins, assembly of viral components into new viruses,
- and release of new viruses from host cell.
Antiviral strategies aim to block viral reproduction at any of these stages.
To prevent viral attachment, a drug can either bind to host cell receptor/coreceptor, or to the viral spike protein. Examples are HIV drugs - CCR5-antagonists. They bind to CCR5 coreceptor, masking its binding site for HIV.
For enveloped viruses, one strategy is to prevent fusion of viral and host cell membrane. An agent can bind directly to the viral protein that is responsible for fusion, or disrupt the condition that is required for fusion.
Several drugs have been developed to inhibit the uncoating of influenza A virus - they impair the function of the protein responsible for viral genome release from endosomes.
Viruses that use reverse transcriptase for replication are usually targeted for this enzyme. Because the process of reverse transcription, converting RNA to DNA, occurs only in these viruses and not human cells, drugs targeting reverse transcriptase are generally safe for humans. Most of these agents are nucleoside or nucleotide analogs. They compete with regular nucleotides, insert themselves into the growing chain of DNA, and stop the process prematurely. There are also non-nucleoside reverse transcriptase inhibitors, which bind non-competitively to the reverse transcriptase, impairing its function. The 2 classes of inhibitors are usually combined for maximum effects.
Retroviruses, such as HIV, use viral enzyme integrase to insert their genome into host cell DNA, a critical step for viral reproduction. Drugs that inhibit integrase have been developed to treat HIV and other retroviruses.
Viruses with large DNA genomes usually encode their own DNA polymerase for DNA replication. Viral DNA polymerases are the target of many currently available antiviral drugs. Most of these drugs are nucleoside analogs, they incorporate into the growing DNA and cause premature termination of viral DNA synthesis.
Another approach is to inhibit viral protein synthesis by antisense mechanism. Antisense antiviral drugs are short synthetic nucleic acid strands that are complementary to part of an essential viral mRNA. They bind specifically to the viral mRNA, effectively preventing it from being translated into protein.
Some viruses require activity of a specific protease to cleave precursor viral proteins into functional components for viral assembly. Several drugs have been developed to target this protease in HIV.
Influenza virus requires action of viral enzyme neuraminidase to release new viruses from host cell. Blocking neuraminidase is an effective way to treat influenza.

[@Alilamedicalmedia]

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[@jellebakker8193]

This was extremely useful for my research on virusses. I'm so glad people are taking their time to produce these kind of videos with clear explanation.

[@josephchambers68]

Great video that is easy to understand whilst giving a concise and informative overview

[@zainhamid5545]

This video making my concepts more clear big respect and thanks for creator

[@SaravananS-gc4kt]

Thanks mam Clear explanation

[@RUYINAETENGsMEDICDIARY]

Thank you so much

[@pharmaboy1510]

Excellent

[@crystalsareallisee]

This was very easy to understand. Thank you so much.

[@jihyun2434]

so much help

[@Misaka-gt5yj]

I think the most ludicrous thing is that people still confuse molnupiravir MOA with ribavirin. For ribavirin, there is multiple antiviral mechanisms including polymerase inhibition, and error catastrophe doesn't happen. Not for molnupiravir, which introduces mutations but does NOT inhibit viral replication.

[@sajedahaisam9135]

Amazing video

[@niazwali8169]

Nice very helpful

[@xxnajdxxful]

Brilliant

[@benitoramirezbarrera781]

great video!

[@nicholasbrandt4464]

What is a polymerase inhibitor

[@omaralkhatib3646]

Antivirals require a lot of research, and are hard to develop because of the simplicity of viruses, especially the fact that some, such as rhinoviruses can mutate in a few days!

[@RKGHARSE]

I'm also on TH-cam

[@oussamafr6123]

If you use this drugs the immune system still works against the virus or no?

[@jatinshahu9054]

Can we give artificial interferons ?? 🤔🤔

[@Alilamedicalmedia]

Yes, but because interferons act to modulate the body's immune response (rather than targeting a particular virus) and the immune system is complex, the antiviral effect, and side effect, may be very different for different people.

[@jatinshahu9054]

Okay got it !! 😃

[@jatinshahu9054]

Thank you

[@Alex-jb8wr]

Alila Medical Media On the topic of Interferons, I read they create antiviral proteins that target dsRNA. Do these proteins only attack dsRNA or all virus proteins?

[@jatinshahu9054]

@@Alex-jb8wr hey Alex .. according to what I have studied, when viruse infect any cell in the body it inject it's viral gene in cell and then this infected cell releases type-I IFN ( IFN-a and IFN-b) and "these IFNs are part of innate immunity" and now these released IFNs do their work on Non-infected(Uninfected) cells by producing anti-viral proteins. When virus encounters this Non-infected(Uninfected) cell, these anti-viral proteins inhibits DNA/RNA synthesis.

[@ornith4213]

Vivid

[@amosnyirenda5712]

Next time try not be very fast

[@leilaknight2644]

Go to settings on the video, and adjust playback speed to slow it down.