D5 Flashcards
Viruses
All viruses have a central core of genetic material, surrounded by protein coat, non-cellular with no nucleus or cytoplasm, requires host for reproduction, non-living
Responsible for causing many diseases: AIDS, influenza, rabies, common cold, small pox, measles
How viruses work
- virus attaches to host cell surface
- viral DNA injected into cell:? coat of virus remains outside
- viral DNA is replicated in host cell
- New protein coats synthesised within the host cell
- mature virions are assembled within the cell
- cell ruptures, releasing mature virus particles
Bacteria
self-reproducing, able to grow, feed, and excrete, contain organelles which all perform specific functions, many times larger than viruses, have more complex DNA, mutate slower than viruses
Difficulties in targeting viruses
Viruses mutate quickly so they can adapt to drugs and can evade human immune system
Bacteria can be killed or their actions reduced by simple chemical agents, but viruses cannot be killed and must be targeted on a genetic level
Each kind of virus requires special drugs whereas different types of bacteria employ similar metabolic processes so can be targeted by common antibacterials
Antiviral drugs
Many antivirals developed to interfere with the viral life cycle
Can be achieved by: prevention of viral particle release from host cell, alteration of cell’s DNA so virus cannot multiply, blocking of host cell’s enzyme activity preventing virus from reproducing
Antiviral case study: Influenza
influenza particularly serious for elderly and those with compromised immune systems
One of most serious pandemics in world was the Spanish flu - influenza
Influenza viruses have specific key proteins on their surface that play a key role in their life cycle: Hemaglutinin - responsible for docking virus to host, Neuramidase - critical in releasing new viral particles from host cells
Neuraminidase inhibition
Inhibiting the neuraminidase pathway has been proven to be most effective treatment of influenza
First inhibitors (Relenza) developed in Australia by Mark Von Itzstein - early example of drug designed completely by computer and was released for use in humans in 2000
Success due to similar structure to natural substrate of neuraminidase enzyme sialic acid
Antiviral drugs: mode of action
HIV and AIDS
Infection with HIV results in eventual diagnosis of AIDs
Lots of infection in 1980s-90s but increased education and good health care has seen it reduced in western countries - still critical health issue in Africa
How HIV affects cells
RNA retrovirus
Inside virus capsule is viral RNA which is transcribed into DNA via enzyme reverse transcriptase and new DNA is then integrated into the host cells genome
This allows for reproduction of virus - the virus hijacks the immune system’s T cells and also stops immune response from signalling to rest of immune system
Treatment of HIV
Reverse transcriptase inhibitors and protease inhibitors - most treatments use a combo of the 2
This combination therapy aims to reduce HIV viral particles in blood to undetected levels - not a cure as they don’t remove virus completely
HIV treatment challenges
Socioeconomic factors: high price of antiretroviral drugs, cost to state, access to drugs
Cultural issues: discrimination, stigma
Vaccines
Weakened form of a disease antigen - may be dead or living - injected into body
Bosy reacts to antigen by creating antibodies to attack it
If the certain antigen is detected in body again, body’s immune system antibodies will be able to fight against it
