<< Chapter < Page Chapter >> Page >
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

Got questions? Get instant answers now!

True/false

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

true

Got questions? Get instant answers now!

Short answer

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

Got questions? Get instant answers now!

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?

Got questions? Get instant answers now!

Questions & Answers

how does Neisseria cause meningitis
Nyibol Reply
what is microbiologist
Muhammad Reply
what is errata
Muhammad
is the branch of biology that deals with the study of microorganisms.
Ntefuni Reply
What is microbiology
Mercy Reply
studies of microbes
Louisiaste
when we takee the specimen which lumbar,spin,
Ziyad Reply
How bacteria create energy to survive?
Muhamad Reply
Bacteria doesn't produce energy they are dependent upon their substrate in case of lack of nutrients they are able to make spores which helps them to sustain in harsh environments
_Adnan
But not all bacteria make spores, l mean Eukaryotic cells have Mitochondria which acts as powerhouse for them, since bacteria don't have it, what is the substitution for it?
Muhamad
they make spores
Louisiaste
what is sporadic nd endemic, epidemic
Aminu Reply
the significance of food webs for disease transmission
Abreham
food webs brings about an infection as an individual depends on number of diseased foods or carriers dully.
Mark
explain assimilatory nitrate reduction
Esinniobiwa Reply
Assimilatory nitrate reduction is a process that occurs in some microorganisms, such as bacteria and archaea, in which nitrate (NO3-) is reduced to nitrite (NO2-), and then further reduced to ammonia (NH3).
Elkana
This process is called assimilatory nitrate reduction because the nitrogen that is produced is incorporated in the cells of microorganisms where it can be used in the synthesis of amino acids and other nitrogen products
Elkana
Examples of thermophilic organisms
Shu Reply
Give Examples of thermophilic organisms
Shu
advantages of normal Flora to the host
Micheal Reply
Prevent foreign microbes to the host
Abubakar
they provide healthier benefits to their hosts
ayesha
They are friends to host only when Host immune system is strong and become enemies when the host immune system is weakened . very bad relationship!
Mark
what is cell
faisal Reply
cell is the smallest unit of life
Fauziya
cell is the smallest unit of life
Akanni
ok
Innocent
cell is the structural and functional unit of life
Hasan
is the fundamental units of Life
Musa
what are emergency diseases
Micheal Reply
There are nothing like emergency disease but there are some common medical emergency which can occur simultaneously like Bleeding,heart attack,Breathing difficulties,severe pain heart stock.Hope you will get my point .Have a nice day ❣️
_Adnan
define infection ,prevention and control
Innocent
I think infection prevention and control is the avoidance of all things we do that gives out break of infections and promotion of health practices that promote life
Lubega
Heyy Lubega hussein where are u from?
_Adnan
en français
Adama
which site have a normal flora
ESTHER Reply
Many sites of the body have it Skin Nasal cavity Oral cavity Gastro intestinal tract
Safaa
skin
Asiina
skin,Oral,Nasal,GIt
Sadik
How can Commensal can Bacteria change into pathogen?
Sadik
How can Commensal Bacteria change into pathogen?
Sadik
all
Tesfaye
by fussion
Asiina
what are the advantages of normal Flora to the host
Micheal
what are the ways of control and prevention of nosocomial infection in the hospital
Micheal
what is inflammation
Shelly Reply
part of a tissue or an organ being wounded or bruised.
Wilfred
what term is used to name and classify microorganisms?
Micheal Reply
Binomial nomenclature
adeolu

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Microbiology' conversation and receive update notifications?

Ask