A cancer treatment could force HIV into hiding. 

Researchers found the cancer immunotherapy treatment, pembrolizumab, can reverse HIV latency, the ability for the virus to ‘hide’ inside cells of people living with HIV on antiretroviral therapy, the major barrier to a cure for HIV.  

Pembrolizumab is a monoclonal antibody that reverses the ‘exhaustion’ of the immune system. 

Specifically, when killer T cells get worn out they express proteins on their surface, one of which is called PD1. The monoclonal antibodies, also referred to as anti-PD-1, work by blocking these exhaustion markers, allowing the killer T cells to regain function and kill the cancer. The drug has revolutionised the treatments of several cancers, including melanoma. 

In the new study, researchers found the PD1 exhaustion markers allow HIV to go into hiding.

The findings come from the largest, multicentre prospective clinical trial of pembrolizumab in people with cancer who are also living with HIV.

The study was overseen by Professor Sharon Lewin - Director of the Peter Doherty Institute for Infection and Immunity (Doherty Institute) - a world leader in HIV cure research and co-lead of this latest clinical trial. 

“It’s not straightforward to bring this approach to the clinic in people living with HIV without cancer,” Professor Lewin explains. 

“The side effects of immunotherapy currently are significant, for example, five to 10 per cent of people will get an adverse event. 

“In a cancer setting this isn’t a major concern as you have a life-threatening illness, but in HIV, the situation is very different. 

“People can now live normal and healthy lives with HIV, so any intervention for a cure must have very low toxicity. 

“In this study, we were able to show that in a cohort of 32 people who have cancer who are also living with HIV, pembrolizumab was able to perturb the HIV reservoir, which is a very exciting result and involved many groups around the world.” 

Professor Lewin says the next step will be to see how pembrolizumab modifies the immune response to HIV. 

“It’s an incredible opportunity because we know exactly what the T cells are responding to. We’re endeavouring to ascertain the effect anti-PD-1has on the HIV-specific killer T cells in the hope that as well as reversing HIV latency, it will also rev up the immune system to kill the HIV infected cells in the way it does with cancer,” she said. 

The latest study is accessible here.