2. RETROVIRUS
A retrovirus is an RNA virus that replicates in a
host cell through the process of reverse
transcription. First it uses its own reverse
transcriptase enzyme to produce DNA from its
RNA genome, reverse of the usual pattern, thus
retro (backwards). This new DNA is then
incorporated into the host's genome by an integrase
enzyme.
3. The following genera are included here:
Genus Alpharetrovirus; type species: Avian leukosis
virus; others include Rous sarcoma virus
Genus Betaretrovirus; type species: Mouse mammary
tumour virus
Genus Gammaretrovirus; type species: Murine leukemia
virus; others include Feline leukemia virus
Genus Deltaretrovirus; type species: Bovine leukemia
virus; others include the cancer-causing Human T-
lymphotropic virus
Genus Epsilonretrovirus; type species: Walleye dermal
sarcoma virus
Genus Lentivirus; type species: Human
immunodeficiency virus 1; others include Simian, Feline
immunodeficiency viruses
Genus Spumavirus; type species: Simian foamy virus
4. According to Baltimore’s classification they are:
Group VI viruses
All members of Group VI use virally encoded reverse transcriptase, an RNA-
dependent DNA polymerase, to produce DNA from the initial virion RNA
genome. This DNA is often integrated into the host genome, as in the case of
retroviruses and pseudoviruses, where it is replicated and transcribed by the
host.
Group VI includes:
Family Metaviridae
Family Pseudoviridae
Family Retroviridae - Retroviruses, e.g. HIV
Group VII viruses
Both families in Group VII have DNA genomes contained within the invading
virus particles. The DNA genome is transcribed into both mRNA, for use as a
transcript in protein synthesis, and pre-genomic RNA, for use as the template
during genome replication. Virally encoded reverse transcriptase uses the pre-
genomic RNA as a template for the creation of genomic DNA.
Group VII includes:
Family Hepadnaviridae - e.g. Hepatitis B virus
Family Caulimoviridae - e.g. Cauliflower mosaic virus
5. NOW HIV…….
Human immunodeficiency virus (HIV) is a lentivirus (slowly
replicating retrovirus) that causes acquired
immunodeficiency syndrome (AIDS), a condition in humans
in which progressive failure of the immune system allows life-
threatening opportunistic infections and cancers to thrive.
Infection with HIV occurs by the transfer of
blood, semen, vaginal fluid, pre-ejaculate, or breast milk.
Within these bodily fluids, HIV is present as both free virus
particles and virus within infected immune cells.
8. BRIEF HISTORY…..
AIDS was first clinically observed in 1981 in the United
States. The initial cases were a cluster of injection drug users
and gay men with no known cause of impaired immunity who
showed symptoms of Pneumocystis carinii pneumonia
(PCP), a rare opportunistic infection that was known to occur
in people with very compromised immune systems. Soon
thereafter, additional gay men developed a previously rare
skin cancer called Kaposi's sarcoma (KS).
Both HIV-1 and HIV-2 are believed to have originated
in non-human primates in West-central Africa and to have
transferred to humans (a process known as zoonosis) in the
early 20th century. HIV-1 appears to have originated in
southern Cameroon through the evolution of
SIV(cpz), a simian immunodeficiency virus (SIV) that infects
wild chimpanzees (HIV-1 descends from the SIVcpz endemic
in the chimpanzee subspecies Pan troglodytes troglodytes)
9. Left to right: the African green monkey source of SIV, the sooty
mangabey source of HIV-2 and the chimpanzee source of HIV-1
10. ABOUT VACCINE….
Washington -The hunt for an HIV vaccine has
gobbled up $8bn in the past decade, and the
failure of the most recent efficacy trial has
delivered yet another setback to 26 years of
efforts.
With the next attempts expected to be years
away, top researchers now say there is a "void"
or a "gap" in current clinical trial efforts to test
whether a vaccine may be safe and effective in
people.
11. BRIEF FACTS…..
How quickly do people infected with HIV develop
AIDS?
The length of time can vary widely between individuals. The
majority of people infected with HIV, if not treated, develop
signs of HIV-related illness within 5-10 years, but the time
between infection with HIV and being diagnosed with AIDS can
be 10–15 years, sometimes longer. Antiretroviral therapy
can slow down disease progression to AIDS by decreasing the
infected person’s viral load.
12. Primary HIV infection - may be asymptomatic or experienced
as Acute retroviral syndrome.
Clinical stage 1 – asymptomatic or generalized swelling of the
lymph nodes
Clinical stage 2 - includes minor weight loss, minor
mucocutaneous manifestations, and recurrent upper respiratory
tract infections
Clinical stage 3 - includes unexplained chronic
diarrhoea, unexplained persistent fever, oral candidiasis or
leukoplakia, severe bacterial infections, pulmonary
tuberculosis, and acute necrotizing inflammation in the mouth.
Some persons with clinical stage 3 have AIDS.
Clinical stage 4 - includes 22 opportunistic infections or cancers
related to HIV.
All persons with clinical stage 4 have AIDS.
Most of these conditions are opportunistic infections that can be
treated easily in healthy people.
17. HIV AS A REMEDY…..
The HIV virus may be about to become a new weapon
in the fight against cancer as initial tests have shown it
can drastically minimize and even help cure the most
common form of leukemia.
A research team, led by Dr. Carl June working out of
the Abramson Cancer Center at the University of
Pennsylvania, has been experimenting with using a
harmless version of the HIV virus combined with
genetically modified white blood cells as a new way to
fight cancer. The cells are taken from patients and
modified with new genes that make them target
cancer cells, but just as importantly, they can also
multiply once injected allowing them to scale up as a
small army inside the body.
18. HOW?
.
1. Doctors run the patient’s blood through a machine that
removes T-cells, but returns the rest of the blood to the
patient. T-cells are virus and cancer fighting white blood
cells.
2. A modified form of the HIV virus is used to infect the T-
cells and insert genes that cause it to recognize and attack a
particular cancer, then multiply and survive in the patients for
months.
N.B :
The modified HIV virus carries what Carl June, one of the
doctors involved, called a "Rube Gol dber g-l i ke
sol ut i on“, in an interview with the New York Times. The
virus carries DNA from humans, mice and cows, a virus that
infects woodchucks, and one that infects cows.
19.
20. The modified T-cells then carry chimeric antigen
receptors, proteins which allow them to recognize and kill
multiple cancer cells.
3. Chemotherapy kills any remaining T-cells in the patient.
The doctors don't want un-modified T-cells impeding the new
ones.
4. The modified T-cells are returned to the patient. Within the
patient the newly re-programmed T-cells proliferate.
5. Over the next few weeks the patient develops a
temperature, chills, shakes, low blood pressure, and other
flu-like symptoms. The symptoms are caused by chemicals
called cytokines produced by the T-cells.
The flu-like symptoms also mean the cancer is on the run.
After the ordeal, doctors estimated that two pounds of
cancer cells had died off in one patient, William Ludwig.
21.
22. The results have surprised everyone. These
modified cells have acted like serial
killers, multiplying and killing all of the cancer
cells in two patients, while reducing them by
70% in a third. The equivalent of five pounds
of cancer cells has disappeared from each
patient. More good news stems from the fact
that the modified cells remain in the body and
have been seen to reactivate and kill new
cancer cells as long as 12 months after they
were first injected.
23. ABOUT A GIRL CURED USING THIS EXPERIMET…..
In April this year, Emily Whitehead's family had almost given
up hope.
The brave six-year-old had been fighting leukaemia for two
years, only to relapse for a second time during intensive
chemotherapy treatment in February.
Doctors had exhausted all the traditional treatments as Emily
could not remain in remission for long enough to attempt a
bone marrow transplant. So her desperate parents, Kari and
Tom, started looking at more radical options.
N.B: Video on you-tube