HIV : Human Immunodeficiency Virus. How it infects the body.

1. Retrovirus
HIV Structure
Helper T Cells
Mechanism of infection
HIV

2. Retrovirus:
Any group of RNA viruses which insert a
copy of their genome into the DNA of the
host cell in order to replicate.

3.  BECAUSE they contain only
RNA but they don’t contain
DNA.
Retroviruses are unable to replicate outside
of living host cells !!

4. HIV Structure:
# HIV is an enveloped RNA virus. It acquires an outer
envelope consisting of a lipid bilayer with spikes of
glycoproteins gp41 and gp120.
# Inside this envelope is a nucleocapsid, which
surrounds a central core of protein.
# Within this core, are two copies of single-stranded
RNA (the virus genome).
# Proteins and multiple molecules of the enzyme
(Reverse transcriptase, Integrase, Ribonuclease H
and Protease) also found in the core.

7. They strengthen the immune system response to
infection by:
① Releasing chemicals that attract other white
blood cells to the site of infection to attack invading
bacteria or virus.
② Releasing chemicals that cause other white blood
cells to multiply. These new white blood cells create
markers called Antibodies which can identify the
foreign invaders throughout the body.
Helper T Cells :

8. The mechanism of HIV infection:
1- The virus enters the body then its surface proteins
GP120 attach to CD4 and Co-receptors found on helperT
Lymphocytes.
GP 120

9. 2- The lipid membrane of the virus combines with
the host cell’s membrane , while the viral core enters
the host cell.
Viral core
Viral core
GP 120

10. 3- The core uncoats allowing the viral genetic material
which is RNA + Enzymes to enter the cytoplasm of the
host cell.

11. 4- The viral enzyme Reverse transcriptase copies the
RNA into complementary DNA ( cDNA ).
RNA

12. 5- The viral RNA is destroyed by another viral Enzyme
called Ribonuclease H.

13. 6- Reverse transcriptase then synthesizes a second DNA
strand using the first as a template.

14. 7- The double-stranded viral DNA enters the nucleus
with several types of viral proteins including an Enzyme
called Integrase.
The Viral DNA

15. 8- Integrase Enzymes splice the viral DNA into the host
cell’s chromosomal DNA.
*The integrated viral DNA is known as Provirus*

16. 9- The proviral DNA is transcripted into RNA which
contains the code to produce the capsid proteins and
other proteins needed for the viral assembly.
Transcripted
viral RNA

17. 10- In the spliced form RNA also codes for the envelope
proteins ( GP 120 ) and other proteins.
The
spliced
RNA

18. *Envelope proteins are produced in the rough endoplasmic reticulum
(rER) and then move through The Golgi body before arriving at the
cell surface*

20. 11- Finally, viral RNA and associated proteins are packaged and bud
off from the host cell surface. These proteins will then bind to the
receptors on other immune cells facilitating the spread of infection
through the body by destroying more Helper T Cells.
New HIV Cell
*Budding viruses are often exactly like the original particle that initially
infected the host. In the case of HIV, however, the resulting viruses display
a range of variations which makes treatment difficult*

23. So , HIV Sequence of Infection is:
1. ATTACHMENT
Getting in
2. REVERSE TRANSCRIPTION
From viral RNA to DNA
3. INTEGRATION, TRANSCRIPTION
a. Viral DNA joins host DNA
b. Making multiple viral RNAs
4. TRANSLATION
Producing viral proteins
5. VIRAL PROTEASE
Cleaving viral proteins
6. ASSEMBLY & BUDDING
Getting out