By Stephanie Baringer
Amidst the chaos surrounding the COVID-19 pandemic, other areas of the virology field have continued to advance. In early March, it was announced that Adam Castillejo, a 40-year old man from London, was cured of human immunodeficiency virus (HIV). HIV is a virus that weakens the immune system by destroying white blood cells that normally fight infection. This places the patient at a greater risk for infections and certain cancers and ultimately leading to AIDS. Globally, 37.9 million people have either HIV or AIDS, and an estimated 770,000 people die from AIDS-related illnesses each year. While there is no universally accepted cure, there is a standard treatment, antiretroviral therapy (ART). ART is a combination of three drugs that must be rigorously taken daily to suppress the virus from replicating and spreading the infection. This treatment of HIV is used to manage symptoms and to slow the progression. However, Castillejo received a stem-cell treatment, and is now the second person to be cured of HIV this way.
Diagnosed in 2012, Castillejo was originally treated for his advanced Hodgkin’s lymphoma, a type of cancer that originates in white blood cells. The first patient to be cured of HIV this way in 2008 was previously diagnosed with acute myeloid leukemia. Both treatments started with chemotherapy and a stem-cell transplant from a donor patient whose white blood cells had an HIV resistance mutation. The mutation was in the CCR5 receptor, the receptor most commonly used by HIV to enter the cell. Without a route into the cell, the virus cannot start the infection process and is eventually phased out. If this sounds familiar, it may be because this is the same gene that Dr. He Jiankui attempted to mutate in his infamous gene-edited twins.
During the stem-cell therapy Castillejo underwent, approximately 99% of Castillejo’s immune cells were replaced. However, some remnants of the virus still remained. A reservoir of cells carrying HIV can stay in the body in a dormant state for many years. Therefore, it is impossible to say if he will ever redevelop the disease. Thirty months after the treatment, the HIV viral load in Castillejo’s blood plasma was undetectable and HIV specific T-cell responses were absent. T-cells help fight foreign invaders by activating other immune cells. A lack of response indicates a lack of the virus. Doctors and researchers found low levels of viral DNA in Castillejo’s peripheral T-cell memory, indicating that the virus was not 100% gone. For the sake of clinical significance, the tests conclude that Castillejo is HIV free.
As promising as stem-cell therapy is for HIV patients, researchers have made it clear the treatment is not viable for everyone. It is an aggressive therapy that has only been deployed to treat a patient’s hematological cancer. Additionally, the current ART treatments are highly effective when taken every day and as a result, patients can live long and healthy lives. Dr. Ravindra Kumar Gupta, the lead researcher from the University of Cambridge, says, “It is important to note that this curative treatment is high-risk and only used as a last resort for patients with HIV who also have life-threatening hematological malignancies. Therefore, this is not a treatment that would be offered widely to patients with HIV who are on successful anti-retroviral treatment.” While we may not be looking at a universal cure, stem-cell therapy provides options for the thousands of patients who suffer from both cancer and HIV.