Slides in this set
· HIV/AIDS is caused by the human immunodeficiency virus.
· `AIDS' stands for acquired immune deficiency syndrome.
· Every year about 5 million people are newly infected.
· There were approximately 45 million people living with HIV/AIDS
at the end of 2005. Nearly 30 million people had died from
HIV/AIDS related diseases by the end of 2005.
· HIV can be transmitted in the following ways:
· Exchange of body fluids such as blood-to-blood contact
· Unprotected sexual intercourse
· Unscreened blood transfusions
· Use of unsterilized medical equipment
· Sharing hypodermic needles
· Accidents such as `needle-stick'
· Across the placenta or during childbirth
· From mother to baby during breast feeding…read more
Transmission of HIV/AIDS
What sort of pathogen is involved?
· HIV is the virus and therefore the pathogen. HIV is a retrovirus (a virus built of
RNA instead of more typical DNA) which can lead to AIDS.
· The virus enters your body and may remain inactive. This is known as being
HIV-positive. Once the virus becomes active it attacks your immune system,
particularly your T helper cells.
What are T helper cells (T lymphocytes)?
· T helper cells are a sub-group of lymphocytes, a type of white blood cell. These
contain CD4 receptors on their surfaces, which the virus uses to bind with and so
enters the lymphocyte.
· These cells normally help prevent infection and if they are destroyed, you are
more likely to contract a variety of `opportunistic infections'. This is because
you're unable to defend yourself against any pathogen that enters your body.
What are opportunistic infections?
· An opportunistic infection is an infection caused by pathogens, particularly
those that take advantage of certain situations- such as bacterial, viral, fungal
and protozoan that usually do not cause disease in a healthy host.…read more
HIV pathogen life cycle
Entry: HIV can only replicate inside human cells. The process begins when a
virus particle bumps into a cell that carries CD4 receptors on its surface. The
spikes on the surface of the virus particle stick to the CD4 and allow the viral
envelope to fuse with the cell membrane. The contents of the HIV particle are
then released into the cell, leaving the envelope behind.
Reverse Transcription and Integration: Once inside the cell, the HIV
enzyme reverse transcriptase converts the viral RNA to DNA. This DNA is
transported to the cells nucleus, where it is joined to the human DNA by the HIV
enzyme integrase. Once integrated, the HIV DNA is known as provirus.
Transcription and Translation: HIV provirus may stay inactive within a cell
for a long time. But when the cell becomes activated, it treats HIV genes in much
the same way as human genes. First it converts them into mRNA (using human
enzymes). Then the mRNA is transported outside the nucleus, and is used as a
blueprint for producing new HIV proteins and enzymes.
Assembly, Budding and Maturation: Among the strands of mRNA made
by the cell are complete copies of HIV genetic material. These gather together
with newly made HIV proteins and enzymes to form new viral particles. The
HIV particles are then released or 'bud' from the cell. The enzyme protease
chops up long strands of protein into smaller pieces, which are used to
construct mature viral cores.…read more
HIV infected person:
Several weeks after initial infection, flu-like
symptoms are experienced.
The untreated, infected individual usually remains
healthy for about 5-15 years, but the virus continues
to replicate and slowly destroys their immune
Eventually the body is unable to defend itself which
allows opportunistic infections to enter the body.
Acquired Immune Deficiency Syndrome is the name
given to this final stage of HIV infection, and is
characterised by various, life-threatening illnesses
such as weight loss, rare cancers, pneumonia, fungal
conditions and infections of the brain and eye.…read more