Transcript Document

Antivirals
Structure of a Virus
• all viruseso have a central core of DNA or RNA
o surrounded by a coat(capsid) of packed protein
units(capsomers)
• UNLIKE bacteria- viruses have no nucleus or cytoplasm
o therefore, they are not cells
o do not feed,
excrete, or grow
o can only reproduce inside
the cells of living
organisms using the host
cell
Multiplication of Viruses
• can survive outside the host cell
• can only replicate by:
o penetrating the living host cell
o then injecting their DNA or RNA into the cell's
cytoplasm(part of the cell enclosed within the cell
membrane).
o the virus then takes over the biochemical machinery
o causes the host cell to become altered or die, leads to
symptoms of a viral infection.
• produces new DNA or RNA and forms large numbers of the
viruses
o then released to infect other healthy cells
Antiviral Drugs
• Viral Infections:
o cold, influenza, mumps, chicken pox
• Body's defense mechanisms are usually strong enough to
fight the infections, drugs are given to remove pain, fight
fever, or stop a second infection.
o Difficulties:
 viruses multiply fast
 by the time the symptoms appear, there are too many
viruses and the antiviral drugs will have little effect
• problem with inventing new antiviral drugs: they are
always mutating themselves
HIV
Antiviral Drugs cont.
• drugs have been developed to fight specific infections
• Alters the cell's genetic material- virus can't use it then to
multiply
o Acyclovir: used to treat cold sores caused by herpes
 structurally similar to deoxyguanosine(a building
block of DNA)
 viral enzymes are tricked into using it as a building
block for the viral DNA and prevents spreading
• Prevent the new viruses formed from leaving the cell
o Amantadine: used against the influenza virus
 enzyme used by influenza virus to stick to the host
cell wall as it leaves is called neuraminidase
 works by inhibiting the active site on this enzyme
AIDS(Acquired Immune Deficiency
Syndrome)
• no cure for AIDS
• drugs that slow dow the HIV virus and damage to your immune
system
• AIDS is the most advance stage of HIV
• HIV is a virus that kills or damages the cells of the body's immune
system
AIDS: What is it?
• Cause by a retroviruso it contains RNA instead of DNA
• virus invades cells, particularly white blood cells(normally
activate other cells in the immune system)
o the body is then left helpless to fight the infection
AIDS: What happens?
• the virus invades a healthy cell
• makes viral DNA from the RNA template using an enzyme
called reverse transcriptase
• this process is OPPOSITE of the process that takes place in
healthy cells
o i.e.: RNA is made from DNA template using the
transcriptase enzyme
Drugs that help fight AIDS
• AZT(zidovudine)
o combines with the enzyme that the HIV virus uses to
build DNA from RNA and clogs it active site
o reverse-transcriptase inhibitor
 instead of changing RNA to DNA it clogs the active site
so that the virus can't create viral DNA
o only retroviruses use the enzyme AZT, does not affect
healthy cells
 an RNA virus that is replicated in a host cell via the enzyme reverse
transcriptase to produce DNA from its RNA genome.
Sources:
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http://www.nlm.nih.gov/medlineplus/aids.html
http://en.wikipedia.org/wiki/Retrovirus
http://www.drugs.com/pro/amantadine.html
http://www.avert.org/aids.htm
http://www.drugs.com/acyclovir.html
http://en.wikipedia.org/wiki/AIDS#Treatment
http://www.aids.gov/
http://www.aids.org/factSheets/101-What-is-AIDS.html
http://en.wikipedia.org/wiki/Cytoplasm