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HIV (Human Immunodeficiency Virus) is a virus that infects particular cells of the immune system, called CD4 T-cells.

If left untreated, HIV gradually weakens the immune system of an infected person making them more susceptible to other infections which may put their life at risk.

HIV can be transmitted through unprotected sexual intercourse (anal or vaginal), sharing of contaminated needles, transfusion of contaminated blood, and between a mother and baby during pregnancy, childbirth, and breastfeeding.

AIDS (acquired immune deficiency syndrome) is a term that describes the point at which an infected person’s immune system can no longer function properly because of the damage caused by HIV, and they get one or more specific, often severe, illnesses.

It can take up to 10-15 years for an untreated person to advance to AIDS. Although there is currently no cure for HIV, antiretroviral drugs target HIV and stop it from multiplying. Antiretroviral therapy usually consists of a combination of at least 2 or more drugs; these medications are usually taken every day and treatment is life-long. Combination antiretroviral therapy significantly slows down the progression of HIV infection and greatly lessen the chance of developing AIDS-defining illnesses. The result is that HIV-infected people can now expect to live much longer. In addition, antiretroviral therapy can reduce the risk of transmitting HIV to partners. However, many HIV-infected people (approximately one third in the UK) are not aware of their infection. People who are not aware of their HIV infection are unable to fully benefit from antiretroviral therapy either for their own health or to prevent transmission of HIV to their partners.

In many parts of the world, especially sub-Saharan Africa, antiretroviral drugs are not affordable but have started to be made freely available since 2004 by donors such as the Global Fund, for all those who are eligible to start treatment. The wider availability of antiretroviral therapy in low income countries has already made a significant impact on health and life expectancy in HIV-infected individuals in those countries. At the end of 2013, approximately 35 million people were living with HIV worldwide, 1.5 million had died from HIV/AIDS and 2.1 million were newly infected with HIV. In low and middle income countries 11.7 million people are on antiretroviral therapy, but according to the World Health Organisation treatment targets, a further 28 million people are eligible for treatment. The situation is a little worse in children, in 2013 fewer than 1 in 4 children living with HIV had access to antiretroviral therapy, compared to 1 in 3 adults.

The MRC Clinical Trials Unit is involved in co-ordinating and running a number of major international clinical trials of antiretroviral therapy and HIV prevention, and different treatment strategies. We also co-ordinate a number of national and international observational studies that help us to understand the progression of HIV and the longer-term effects of treatment.

Our main objectives are to:

  • Identify and recommend optimum strategies for treating and monitoring adults, adolescents and children with HIV
  • Investigate effective ways of preventing HIV transmission
  • Monitor clinical outcome and HIV drug resistance
  • Explore ways to improve long-term adherence to treatment
  • Explore ways to allow people to stay off or stop HIV treatment and sustain a functional cure (so they no longer need antiretroviral therapy to stay healthy)
Finger prick HIV test


18 September 2018

The team behind the CHAPAS paediatric HIV trials has been awarded the prestigious European and Developing Countries Clinical Trials Partnership (EDCTP) prize for Outstanding Research Team.

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SELPHI: An HIV Self-testing Public Health Intervention

SELPHI: An HIV Self-testing Public Health Intervention

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IeDea and Cohere Cohort Collaboration.

Global trends in CD4 cell count at the start of antiretroviral therapy: Collaborative study of treatment programs. Clinical Infectious Diseases. 2018; 66:893-903

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