As many of you may be aware the news has recently highlighted an infectious blood scandal within the NHS. An inquiry that started earlier this week is looking into how NHS patients were given HIV and hepatitis infected blood products in the 1970s and 80s. So what actually is HIV and hepatitis and how does this affect those that were given blood products during this time?
HIV, human immunodeficiency virus, is a virus that is transmitted through blood products and sexual intercourse. This virus is whats called a retrovirus, which means it holds its genetic information as RNA (as compared to DNA which all human cells hold), the RNA is converted to DNA by the viruses own reverse transcriptase and the DNA is inserted into the genome of an infected cell (host cell) where it is uses the cells own system for converting this into protein and therefore creating more HIV viruses.
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HIV affects the T cells within the immune system. It only affects these cells because of the viral structure. It has an envelope on the outside which is made up of a lipid bilayer, within this is a protein capsid inside of which the RNA genetic material and the enzyme reverse transcriptase is held. On the outer lipid bilayer there are certain proteins which bind to CD4 receptors that are found on T cell membranes. This then results in the fusion of the viral lipid bilayer and the T cell membrane allowing the capsid to enter the T cell and break down releasing the RNA and reverse transcriptase into the cytosol of the cell. From here the RNA is converted to DNA and the HIV DNA integrates itself within the host cell genome, where it is transcribed and translated by the host cells systems. This then produces hundreds of new HIV viruses. The HIV viruses at this point are just capsids with internal RNA, they then go towards the host cell membrane where they bud off by exocytosis, stealing the host cells membrane as their external lipid bilayer. Pyroptosis can occur of these cells, resulting in decreasing numbers of T cells. When this level drops below 200, cell mediated immunity is lost and therefore the body is at much greater risk of infection. This is the level at which AIDS develops, leaving the body at serious risk of opportunistic infections that can be fatal in such patients.
Many patients with HIV do not know that they have the virus. After primary infection the T cell level drops over a period of around 3 weeks. This period gives an acute HIV syndrome, a period in which the individual presents with very vague infective symptoms due to the low T cell count and the increased risk of not being able to fight off infections. However, after this period the T cell count recovers a little before if falls over many years until AIDS develops (without treatment). This makes HIV very difficult to diagnose, therefore there is increasing screening offered to all patients and doctors are being advised to offer this screening to patients presenting with any infected symptoms. Treatment is not curative but medication can be taken regularly to keep the viral load down, decreasing the likelihood of most symptoms and transmission of the virus.
Hepatitis C is another virus that has been in the news with the recent scandal. Hep C is spread through blood to blood contact and sexual transmission as with HIV. Primarily it affects the liver, and can initially present as generic liver problem, jaundice, fever, dark urine and abdominal pain. These initial problems often resolve, but after many years can lead to cirrhosis of the liver. Hep C is a small enveloped, single stranded RNA virus. The virus is thought to enter cells through glycoproteins on the surface of the virus allowing endocytosis of the virus into certain cells, however current understanding of the exact mechanism is not fully understood. As with HIV, hep C is treated with antiviral medication, liver transplant is also a consideration in patients with cirrhosis.