What is HIV?
HIV is a retrovirus, which is transmitted through blood or sexual contact. Initial symptoms vary, and can include flu-like symptoms and fever, although most infected people will not have any symptoms at all.
During the later stages of infection, the immune system will become significantly weakened. This is because the virus gradually destroys a section of the immune system called T-cells, which are crucial for the body to fight infection. At the later stages, HIV can develop into Acquired Immunodeficiency Syndrome (AIDS) and other infections, such as severe pneumonia, can occur.
Eventually, without the proper treatment, the loss of the immune cells will pass beyond a critical level and can be fatal.
Why do we need research into early detection systems for HIV?
The 1980s saw the emergence of HIV and the AIDS pandemic. The following years since then have seen an incredible output of research into the virus, and its subsequent characterisation and treatment. However, with an estimated 35 million HIV-infected people worldwide and 1.6 million deaths from AIDS-related infections every year1 there is still a long way to go towards eradication of HIV.
In the UK alone, there are an estimated 100,000 infected individuals. Yet one in four people with HIV in the UK are unaware that they are infected and almost half of the patients that are newly diagnosed with HIV are at a late stage of the infection2. This stage has a high risk of death as well as posing a risk to others through onwards transmission. The health economic benefits of widening access to testing was shown in the Health Protection Agency Report (now Public Health England) in 2011. This has led to new legislation to widen access to testing outside hospital settings, in both developed and developing countries. Self-testing became legal in the UK in 2014.
Finding out early that people have HIV is crucial for starting treatment before their immune system is irreversibly damaged and suffer from life threatening infections as their immune system is weak. Today, diagnosis is made by sophisticated laboratory tests and patients have to visit a clinic to have a test done.
However early detection in non-hospital settings is problematic for rapid-tests, since they typically rely on antibody detection; these antibodies cannot be detected until 3 weeks to 6 months after the exposure. Moreover, antibody detection is sometimes inaccurate, for example it cannot be used to diagnose infants under 18 months of age as their mothers’ antibodies may cause false, positive results.
Biomarkers for early detection are of interest to try and close this window period- the time between onset of infection and detection. Directly detecting parts of the virus, such as a protein called “p24 antigen”, is one way to do this, as this would strongly suggest that the virus is actually present, potentially at a very early stage. This does present challenges due to the very low concentration of these proteins in the blood.
As testing becomes necessary in non-clinical settings, data-linkage becomes increasingly important too; both to keep people linked into follow-up care and for public health efforts. The low-cost and widespread availability of mobile phones in developing countries offers tremendous opportunities for testing in remote settings. Geographically linked information could help support better access to follow-up care and public health interventions, to prevent the spread of HIV.
1. UNAIDS report on the global AIDS epidemic 2013 (figures from 2012).