“Our study shows that the immune system can be as powerful as the most
potent combination drug cocktails,” explains study co-author Dr Ravi Gupta (UCL
Infection & Immunity). “. We’re still a long way from being able to cure
HIV patients, as we still need to develop and test effective vaccines, but this
study takes us one step closer by showing us what type of immune responses an
effective vaccine should induce.”
The study looked at a single 59 year old man in London who was an ‘elite
controller’, meaning that his immune system could control HIV for a long time
without needing treatment. Elite controllers, who make up 0.3% of HIV patients,
eventually require treatment to prevent progression to AIDS but they can go a
lot longer without treatment because their immune systems are more active
against HIV.
The patient in the study had both HIV and myeloma, a cancer of the bone
marrow. The bone marrow produces white blood cells, including those that help
to control HIV. To treat the patient’s myeloma, his bone marrow was completely
removed and replaced using his own stem cells. When the bone marrow was
removed, the immune system was severely impaired, allowing the HIV to re-activate
and replicate. This caused the level of virus in his bloodstream to rise from
fewer than 50 copies per millilitre to approximately 28,000 copies per ml
before immune function returned.
When the patient’s immune function returned about two weeks after the
transplant, the levels of HIV in his bloodstream rapidly fell. His immune
system reduced HIV levels at a similar rate to the most powerful treatments
available, bringing them back down to 50 copies per ml within six weeks.
“By measuring the strength of the immune system required to keep this
virus under control in this rare individual, we have a better idea of the
requirements for successful future treatment,” says co-author Professor Deenan
Pillay (UCL Infection & Immunity, and now also Director of the Africa
Centre for Health and Population Studies, in South Africa). “We also managed to
identify the specific immune cells that fought the infection. This is a single
patient study, but nevertheless it is often the unusual patients who help us to
understand the HIV disease process.”
The patient was not given anti-HIV medication in this study due to
concerns about side-effects affecting the myeloma treatment and low initial
levels of HIV in his bloodstream. It is possible that an equally strong immune
response in combination with powerful drugs could have cured the HIV
completely, however this is far from certain.
“We need to be cautious in interpreting observations from a single
subject,” says Dr Nilu Goonetilleke, who began working on the study at the
University of Oxford and is now at the University of North Carolina at Chapel
Hill. “However, demonstration even from a single subject, that our immune
system can rapidly control HIV-1 tells us a lot about the types of immune
responses we should target and augment through vaccination.”
Dr Gupta adds: “Drugs to stimulate reactivation of dormant HIV are still
imperfect, and we do not know if they would be able to flush out all of the HIV
from the body. Likewise, it remains to be seen whether a vaccine could enable a
normal HIV patient’s immune system to kill HIV with the full strength of an
elite controller. Our study is a proof of principle and the results are
promising, but it is unlikely to lead to a cure for at least a decade.
- See more at: http://www.ucl.ac.uk/news/news-articles/0415/130415-human-immune-system-control-HIV#sthash.sWfZfpHb.dpuf