2/19/2013
History of AIDS
Ryan White
1971-1990
1930: HIV probably transfers to
humans in Africa
1970: HIV enters the U.S.
1981: first cases are identified
1982: AIDS gets its name
1983: first cases among non-drug
using women and children
2005: 40 million people are living
with AIDS
2006: 28% of people in developing
countries who need treatment are
getting it
Human Immunodeficiency Virus
Size:
•100-150 billionths of a
metre
•One twentieth of the
length of an E. Coli cell
•One seventieth of the
diameter of a human
WBC
HIV & WBC
The Structure of Viruses
Bacteriophage
Not made of cells. They do not have a
nucleus, complex inner membranes, or
organelles.
Simpler than bacteria cells.
Core of nucleic acid (DNA or RNA)
Surrounded by a protein coat (capsid).
Some animal viruses are surrounded with
another protective coating (envelope).
Tobacco Mosaic Virus
HIV
1
2/19/2013
Specificity of Viruses
The envelopes of some viruses are covered
with spikes made of carbohydrates &
proteins. The spikes enable viruses to
chemically recognize and attach to the cells
they infect.
Many viruses infect just one host (measles
& polio infect humans), while a few infect
several hosts (rabies)
Viral Replication
(aka: Viral Reproduction)
Purpose of replication is for each virus
particle to make many copies of itself.
This process can either:
rapidly kill a host cell by making the host cell
lyse or burst apart (LYTIC CYCLE)
Stay hidden in the host chromosome and
replicate with normal cell reproduction
(LYSOGENIC CYCLE)
Lytic Cycle
The nucleic acid of the virus takes control
of the activity of the host cell and directs the
host cell to make more copies of the virus.
When the virus is finished making new
copies of itself, it kills the host by releasing
new virus particles to infect more cells.
Draw the Lytic Cycle on p. 478
Lysogenic Cycle
Replication process that doesn’t kill a host
cell.
Nucleic acid attaches to the host cell’s
chromosomes (called a provirus)
Provirus reproduces every time the
chromosome reproduces until a stimulus
causes it to attack the host and go through
the lytic cycle.
Draw the Lysogenic cycle on p. 479
HIV virus buds
off from the host
cell during the
lytic cycle,
enveloping itself
in the host cell’s
membrane.
Herpes Simplex 1 Virus remains in cells as
a provirus, until stress, anxiety, or sunburn
causes it to be activated and enter the lytic
cycle.
2
2/19/2013
The Chicken Pox
Virus can remain as
proviruses in our
bodies’ nerve cells
for many years.
Later in life, these
proviruses may
enter a lytic cycle
and cause the
disease of Shingles
Can Viruses be Stopped?
1.
2.
3.
4.
Prevention.
Vaccination.
Anti-retroviral drugs.
Evolution of the virus.
Virus-like Particles
Viroids: tiny particles of pure RNA that
cause diseases in plants. There is no cure.
Prions: particles of proteins that cause some
diseases in animals (ex: Mad Cow Disease).
Prevention of AIDS
and other STD’s
Do not use drugs, or use new needles
Abstain from sex or delay first sex
Be faithful to one partner, or have fewer
partners
Use male and female condoms
If in doubt, seek professional advice and
testing from your doctor
3