A cure for HIV?
Milad Jeilani
The Human Immunodeficiency Virus (HIV) has plagued the human race for over three decades, and has risen to become one of the deadliest diseases in human history, claiming a staggering 1.6 to 1.9 million lives each year. 1 For years the Âcure for HIVÊ has been on the lips of the most prominent scientists, yet to this day it manages to elude us. But we havenÊt given up hope yet. After all, it took 105 years after the discovery of the typhoid bacterium to develop a vaccine for typhoid. But the time lag is getting shorter. It only took 16 years from the discovery of the hepatitis B virus to the development of a vaccine. 2 Still, there is renewed hope after recent success concerning the now famous ÂBoston patientsÊ: two HIV-positive patients that received bone-marrow transplants, leaving them apparently cured of HIV. HIV is a lentivirus, and like all viruses of this type, it attacks the immune system. The name ÂlentivirusÊ literally means Âslow virusÊ because they take such a long time to produce any adverse effects in the body: it can take up to 15 years for the first signs of HIV infection to appear. 3 In fact, it is so well hidden that the only thing that gives it away is the presence of antibodies against HIV in the blood. However, this does not mean that all is well in this dormancy. There are two types of cells of the immune system that are infected by HIV: CD4 lymphocytes – the regulatory cells of the immune system, and macrophages – these ingest foreign proteins and flag them for the immune system. During the silent phase, some 100 million virus particles are destroyed daily, while simultaneously about 2 billion CD4 1 [Student BMJ, The worldÊs deadliest virus , 2013] 2 [Aidsmap, Why is it so hard to make a vaccine against HIV? , 2013] 3 [AIDS.gov, Stages of HIV, 2009] The virus
lymphocytes (5% of the total population) are destroyed by the virus each day and need to be replaced. 4 Such is the extent of the viral onslaught that after a number of years the replenishment of the CD4 lymphocytes fails to keep up with the virus, resulting in a profound depression of immune function. Furthermore, once this immune function has been compromised, the individual is left to the mercy of opportunistic infections. These are bacterial, viral, fungal or protozoan infections that usually do not cause disease in a healthy host, but which take advantage of weakened immune systems, and can cause devastating illnesses. 5 The Centres for Disease Control (CDC) have developed a list of more than 20 opportunistic infections that are considered as AIDS-defining infections. These include PCP (a rare form of pneumonia), KaposiÊs sarcoma (a tumour), Tuberculosis and Wasting Syndrome. 6 Without treatment, people who are diagnosed with AIDS typically survive about 3 years. Once someone has a dangerous opportunistic infection, life expectancy falls to about 1 year. 7 Another problem with treating HIV is that itÊs a retrovirus. After infecting a body cell, a retrovirus turns its own RNA genome into DNA and then integrates this DNA into the host cellÊs DNA. 8 The virus then lies dormant within the cell indefinitely – for as long as the cell is alive. In this state, the virus is known as a latent virus. It is invisible to the immune system and anti-retroviral drugs (ARVs), because these only kill viruses that are actively replicating. The latent virus can 4 [Schoub, AIDS and HIV in perspective , 1999] 5 [AIDSMEDS, Opportunistic Infections (OIs) , 2011] 6 [AIDS.gov, Opportunistic Infections , 2009] 7 [AIDS.gov, Stages of HIV , 2009] 8 [Global Health Forum, Why we canÊt (yet) cure HIV , 2009]
2
Made with FlippingBook - Online Brochure Maker