Elephants rarely get cancer: less than 5% of captive elephants die of cancer, compared to 20% of humans. Elephant genomes have at least 20 copies of the tumour suppressor, p53, which may explain their low cancer rates relative to humans, who have only one copy.
In 1983, when I was a Cambridge undergraduate studying Part II Pathology, the virus HIV was identified in patients suffering from a newly observed fatal disease called AIDS (acquired immune deficiency syndrome)1. The virus and the disease quickly became one of the greatest medical challenges facing my generation. The response to this crisis exemplifies the power of applied scientific research that I find hugely inspiring.
The HIV pandemic is now in its fourth decade and its statistics are staggering. 75 million people have become infected with HIV and 40 million people have died from AIDS-related illnesses.
But the unprecedented collaboration between clinicians, research scientists, politicians, investors, activists and patients has shown that we can treat and prevent a highly complex infectious disease even on this scale. There has been enormous progress: 1 million people died from AIDS-related illnesses in 2016, compared with 1.9 million in 2005; and 2 million people became newly infected with HIV in 2016, compared with 3 million in 2000.
Yet in 2017 there are still around 38 million people living with HIV and requiring daily, lifelong, treatment to stay well. HIV infects CD4+ cells of the immune system and results in their death, effectively disabling the host’s immune response and allowing other infections which are ultimately fatal. Treatment of HIV infection is extraordinarily difficult. Firstly, there is the genetic diversity and rapid evolution of the virus that is related to the way it replicates in cells. The sheer number of genetically distinct subtypes make drug design exceptionally challenging. Anti-retroviral drugs (ARVs) target processes unique to the virus. Using a combination of three drugs decreases the patient’s viral load, which reverses AIDS-related infections and illness but also prevents onward transmission.
However, virus mutations allow drug resistance to develop: to counter this, we need more user-friendly drug regimens, at a cost that providers can meet, plus a greater breadth of treatment. New drugs include ‘biologics’: sugars, proteins and/or genes that differ from conventional ARVs.
Another difficulty with HIV infection are host cells carrying ‘silent’ virus that is not susceptible to drugs or immune defences. Early diagnosis and immediate onset of continuous treatment is essential to prevent this, demanding novel routes of healthcare provision – such as self-testing and pop-up clinics.
Prevention of infection is critical in tacking infectious disease.
PrEP (pre-exposure chemoprophylaxis) is a combination of drugs, used before and after sex to prevent HIV replication, and is already reducing new infections. But the quest for an effective vaccine is a formidable task, due to the genetic variation of HIV but also the resistance of the virus to antibody binding and clearance. Researchers are designing and testing vaccines with modified forms of HIV antigens to improve generation of effective antibody responses.
The amazing distance covered so far on the road to beating HIV/AIDS is a testament to our passion and ingenuity as scientists and human beings. We aren’t there yet, but with continued collaboration, enthusiasm and inspiration we have the potential to go much further.
Dr Julia Turner
Fellow and Alumna
1. Barré-Sinoussi F, Chermann JC, Rey F, Nugeyre MT, Chamaret S, Gruest J, Dauguet C, Axler-Blin C, Vézinet-Brun F, Rouzioux C, Rozenbaum W, Montagnier L (1983). “Isolation of a T-lymphotropic retrovirus from a patient at risk for acquired immune deficiency syndrome (AIDS)”. Science. 220 (4599): 868–871.
2. WHO. Latest WHO HIV data: http://www.who.int/hiv/data/en/