Tuesday, 15 May 2012

“Blocking HIV’s Attack”

“Blocking HIV’s Attack” (June & Levine, March 2012)

Student Number: 42648729

For decades HIV/ AIDS has been one of the leading causes of death in our world. In 2011, The World Health Organisation classed it as the “3rd largest cause of death in the developing world and 6th largest cause of death worldwide”  (World Health Organisation, 2011)

What Is HIV/AIDS??
HIV stands for Human Immunodeficiency Virus and is the elementary stages of the infectious disease, AIDS (Acquired Immune Deficiency Syndrome). HIV is a retrovirus which is transmitted from an infected individual via blood, semen, vaginal fluid, breast milk and from mother to baby during birth.  It is usually a result of unprotected sex, used needles, blood transfusions, childbirth and poor hygiene in medical practice (AIDS.org, 2012).
How does the HIV attack the body?
                                                             Like all viruses, HIV is unable to replicate and therefore multiply by itself, so it works by attaching to and entering the body’s immune cells which are commonly known as T helper cells or CD4 cells (HIV Replication, 2011).  It uses a certain gene known as CCR5 as a gateway into the cell’s nucleus where the viral RNA undergoes reverse transcription with the cell’s DNA (HIV Replication, 2011).  It modifies the cell’s DNA so that when the body’s defence mechanisms are activated, more of the HIV is discharged. http://www.youtube.com/watch?v=RO8MP3wMvqg
                                             (Kimmel, 2005)

What is the effect of HIV?
The problem with HIV is that when an infected T helper cell is triggered to go out and fight infections, more HIV is released which goes on to attack other healthy T cells. The body’s immune system is further compromised as its coordinating cells are also killed, rendering the body defenceless against other infections (June & Levine, March 2012).

                                                                                                    T cell & HIV      (TheBody.com, 2008)

What are the recent genetic advances in this field and how do they work?
There is no available cure or vaccine for HIV as of yet, however there are antiretroviral drugs which help to inhibit the attachment of the HIV to the T cell or which block the processes necessary for replication within the cell (HIV Replication, 2011) (Nettleman, 2011). The problem with these is that the virus continually mutates and therefore these drugs aren’t a cure (June & Levine, March 2012).  
However in 2009, a Berlin man suffering from Leukaemia was completely cured after undergoing a bone marrow transplant from a person who had genetically inherited from both parents a mutation of the CCR5 gene, known as CCR5-Delta32 (June & Levine, March 2012) (Kimmel, 2005). The theory behind this was that this gene mutation inhibited the HIV from gaining access into the T cell, making the person highly resistant to the virus. The problem with this process however is that firstly a donor with a double CCR5-Delta32 mutation and a compatible HLA is extremely rare and secondly, the process is expensive and wouldn’t be worth it due to the intense chemotherapy and lifelong need for anti-rejection drugs (June & Levine, March 2012) (Kimmel, 2005).
Scientists (Sangamo BioSciences, 2012)have since been developing a way to eliminate the CCR5 gene and thus HIV’s gateway into the T cells. It would use a new gene therapy technique which allows a selected section of the DNA to be eliminated.  The selected section would be determined by 2 proteins; zinc finger proteins which would identify which section to snip and the enzyme nuclease, which would cut the DNA in two.  The cell would then repair the detached DNA free from CCR5 (June & Levine, March 2012) (Coghlan, 2011). Phase 2 testing is underway at Sangamo Laboratorys (Sangamo BioSciences, 2012) . http://www.youtube.com/watch?v=KMnyQirJsgM&feature=related (Sigma Life Science, 2009)
        (June & Levine, March 2012)



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Coghlan, A., 2011. Double whammy gene therapy clears HIV from body. New Scientist, 22 September.
June, C. & Levine, B., March 2012. Blocking HIV's Attack. Scientific American, 306(3), pp. 54-49.
Kimmel, R., 2005. Understanding Genetics. [Online]
Available at: www.thetech.org/genetics/news.php?id=13
[Accessed 14 March 2011].
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[Accessed 14 March 2012].
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Available at: http://www.sangamo.com/pipeline/sb-728.html
[Accessed 14 March 2012].
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Available at: http://www.youtube.com/watch?v=KMnyQirJsgM&feature=related
[Accessed 14 March 2011].
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Available at: http://www.thebody.com/content/art48577.html
[Accessed 14 March 2012].
World Health Organisation, 2011. The Top 10 Causes of Death. [Online]
Available at: http://www.who.int/mediacentre/factsheets/fs310/en/index.html
[Accessed 14 March 2012].

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