Antivirals

Structure of a Virus

• all viruses-o have a central core of DNA or RNAo surrounded by a coat(capsid) of packed protein

units(capsomers)• UNLIKE bacteria- viruses have no nucleus or

cytoplasmo therefore, they are not cellso do not feed, 

          excrete, or growo 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 cello 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 viruseso 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 multiplyo 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 cello 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 retrovirus-o 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 cellso 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 siteo 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:

• 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