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Acyclovir looks similar to guanosine except that the sugar is replaced with a short carbon chain. Step 1: Viral enzyme adds a phosphate group to acyclovir. Step 2: Human enzymes add two more phosphate groups, producing acyclovir triphosphate. Step 3: During viral DNA replication, acyclovir is added to the growing strand rather than GTP. This halts further elongation of the DNA molecule and stops viral replication.
Acyclovir is a structural analog of guanosine. It is specifically activated by the viral enzyme thymidine kinase and then preferentially binds to viral DNA polymerase, leading to chain termination during DNA replication.
Diagram showing HIV infection and locations where drugs can stop the infection. GP120 and G(42 are proteins that are on the surface of the virus and bind to CD4 receptor and CCR5. Enfuvirtide is a fusion inhibitor that blocks this process. When the virus enters, it produces DNA from RNA, this  can be blocked by AZT and etravirine which are reverse-transcriptase inhibitors. Next, the viral DNA integrates into the host DNA. Raltegravir is an integrase inhibitor and blocks this step. Finally the virus is rebuild. Ritonavir is a protease inhibitor and blocks this step.
Antiretroviral therapy (ART) is typically used for the treatment of HIV. The targets of drug classes currently in use are shown here. (credit: modification of work by Thomas Splettstoesser)
Common Antiviral Drugs
Mechanism of Action Drug Clinical Uses
Nucleoside analog inhibition of nucleic acid synthesis Acyclovir Herpes virus infections
Azidothymidine/zidovudine (AZT) HIV infections
Ribavirin Hepatitis C virus and respiratory syncytial virus infections
Vidarabine Herpes virus infections
Sofosbuvir Hepatitis C virus infections
Non-nucleoside noncompetitive inhibition Etravirine HIV infections
Inhibit escape of virus from endosomes Amantadine, rimantadine Infections with influenza virus
Inhibit neuraminadase Olsetamivir, zanamivir, peramivir Infections with influenza virus
Inhibit viral uncoating Pleconaril Serious enterovirus infections
Inhibition of protease Ritonavir HIV infections
Simeprevir Hepatitis C virus infections
Inhibition of integrase Raltegravir HIV infections
Inhibition of membrane fusion Enfuviritide HIV infections
  • Why is HIV difficult to treat with antivirals?

Key concepts and summary

  • Because fungi, protozoans, and helminths are eukaryotic organisms like human cells, it is more challenging to develop antimicrobial drugs that specifically target them. Similarly, it is hard to target viruses because human viruses replicate inside of human cells.
  • Antifungal drugs interfere with ergosterol synthesis, bind to ergosterol to disrupt fungal cell membrane integrity, or target cell wall-specific components or other cellular proteins.
  • Antiprotozoan drugs increase cellular levels of reactive oxygen species, interfere with protozoal DNA replication (nuclear versus kDNA, respectively), and disrupt heme detoxification.
  • Antihelminthic drugs disrupt helminthic and protozoan microtubule formation; block neuronal transmissions; inhibit anaerobic ATP formation and/or oxidative phosphorylation; induce a calcium influx in tapeworms, leading to spasms and paralysis; and interfere with RNA synthesis in schistosomes.
  • Antiviral drugs inhibit viral entry, inhibit viral uncoating, inhibit nucleic acid biosynthesis, prevent viral escape from endosomes in host cells, and prevent viral release from infected cells.
  • Because it can easily mutate to become drug resistant, HIV is typically treated with a combination of several antiretroviral drugs , which may include reverse transcriptase inhibitors, protease inhibitors, integrase inhibitors , and drugs that interfere with viral binding and fusion to initiate infection.

Fill in the blank

Antiviral drugs, like Tamiflu and Relenza, that are effective against the influenza virus by preventing viral escape from host cells are called ________.

neuraminidase inhibitors

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True/false

Echinocandins, known as “penicillin for fungi,” target β(1→3) glucan in fungal cell walls.

true

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Short answer

How does the biology of HIV necessitate the need to treat HIV infections with multiple drugs?

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Niclosamide is insoluble and thus is not readily absorbed from the stomach into the bloodstream. How does the insolubility of niclosamide aid its effectiveness as a treatment for tapeworm infection?

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Questions & Answers

Ayele, K., 2003. Introductory Economics, 3rd ed., Addis Ababa.
Widad Reply
can you send the book attached ?
Ariel
?
Ariel
What is economics
Widad Reply
the study of how humans make choices under conditions of scarcity
AI-Robot
U(x,y) = (x×y)1/2 find mu of x for y
Desalegn Reply
U(x,y) = (x×y)1/2 find mu of x for y
Desalegn
what is ecnomics
Jan Reply
this is the study of how the society manages it's scarce resources
Belonwu
what is macroeconomic
John Reply
macroeconomic is the branch of economics which studies actions, scale, activities and behaviour of the aggregate economy as a whole.
husaini
etc
husaini
difference between firm and industry
husaini Reply
what's the difference between a firm and an industry
Abdul
firm is the unit which transform inputs to output where as industry contain combination of firms with similar production 😅😅
Abdulraufu
Suppose the demand function that a firm faces shifted from Qd  120 3P to Qd  90  3P and the supply function has shifted from QS  20  2P to QS 10  2P . a) Find the effect of this change on price and quantity. b) Which of the changes in demand and supply is higher?
Toofiq Reply
explain standard reason why economic is a science
innocent Reply
factors influencing supply
Petrus Reply
what is economic.
Milan Reply
scares means__________________ends resources. unlimited
Jan
economics is a science that studies human behaviour as a relationship b/w ends and scares means which have alternative uses
Jan
calculate the profit maximizing for demand and supply
Zarshad Reply
Why qualify 28 supplies
Milan
what are explicit costs
Nomsa Reply
out-of-pocket costs for a firm, for example, payments for wages and salaries, rent, or materials
AI-Robot
concepts of supply in microeconomics
David Reply
economic overview notes
Amahle Reply
identify a demand and a supply curve
Salome Reply
i don't know
Parul
there's a difference
Aryan
Demand curve shows that how supply and others conditions affect on demand of a particular thing and what percent demand increase whith increase of supply of goods
Israr
Hi Sir please how do u calculate Cross elastic demand and income elastic demand?
Abari
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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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