Transcript Viral Disease and Virus-like Particles

Discuss with your group
• What does this mean: “viruses are cell specific”?
• Why are viruses cell specific?
• Get out your virus reading assignment.
Viruses are also species specific
The number of species that a virus can infect is
called its home range.
Broad Home range:
Narrow Home range:
West Nile Virus
Measles
• The species specific characteristic of
viruses is significant for controlling the
spread of viral diseases.
For example, smallpox was easier to eradicate because
it only affects humans
(unlike the bird flu and West Nile that affect several
types of animals.)
Small pox
A viral infection causes symptoms in a number of ways:
1. They damage and kill once-healthy cells.
2. When cells are damaged or killed, they can release hydrolytic enzymes
from lysosomes to surrounding cells/tissues.
3. Some viral DNA or RNA codes for protein toxins. The host cell is forced to
translate these genes, producing these proteins, thus releasing toxins.
(Bad bacteria example)
4. Some symptoms are caused by the body’s immune system in response to
the presence of the virus: fever, aches, inflammation, vomiting.
Viral Prevention
• Most vaccines are an injection of virus
particles so your body can recognize and
kill the real virus when it enters your body:
PREVENTION
How a vaccine works: (example, the polio vaccine)
- The polio virus was made inactive by using chemicals
(namely, formaldehyde)
- This inactive virus is then injected into the patient.
Once inside:
- Your body has special white blood cells (B-cells) that
recognize this virus particle as “not self” and memorizes
what the pathogen looks like.
- Then the WBC marks it with a small protein called an
antibody (get it, anti-body/ “not self”)
These antibodies are markers that attach to the virus particles so that
other white blood cells (T-cells) know what to attack.
If this same viral particle were to enter your body at another time, your
immune system already has the correct antibodies and instantly knows to
destroy them.
Anti-Viral Treatment
Anti-viral medicines
These are taken as treatments once the virus has already entered the body.
There are some viruses to which we have anti-viral medications for that slow
or stop the progression of the virus, but does not cure the person of the virus.
Anti-virals impede viral infections by preventing/blocking replication within
the host cells.
Examples: Tamiflu
ARV (Anti Retro-virals)
Valtrex
Believe it or not, viruses are not the smallest or
most simple particles that can cause disease.
Viroids-
small ‘circular’ RNA molecules
without a protein coat.
they do not code for protein
(similar to introns)
Infect plants (potato famine of Ireland)
Believe it or not, viruses are not the smallest or
most simple particles that can cause disease.
Prions-
disease-causing protein molecules
no genetic material
causes abnormal folding of proteins in
the brain which causes degeneration.