Herpes Virus Infection May Cause Pediatric Leukemia

It has been previously shown that a majority of childhood acute lymphoblastic leukemia cases originate from prenatal causes. Findings from a recent study suggest that an infection may play a large role in developing the cancer.

Children diagnosed with acute lymphoblastic leukemia were found to be more than 3 times as likely to have had a cytomegalovirus infection at birth compared with children who do not develop the cancer, according to a study published by Blood.

Acute lymphoblastic leukemia is caused by the bone marrow making too many immature white blood cells that become lymphoblasts, B lymphocytes, or T lymphocytes. These surplus cells do not develop normally, and do not function properly against pathogens. Additionally, as the number of these cells increase, there is not enough space for healthy white blood cells, red blood cells, and platelets, which increases the chance of infection and anemia, and presents a bleeding risk.

Certain genetic conditions, as well as previous cancer treatments, are thought to influence the risk of developing acute lymphoblastic leukemia during childhood. The cancer typically develops in patients between 2- and 6-years-old, and is the most common pediatric cancer.

While infection has been a suspected player in this childhood cancer, the researchers in the current study were the first to identify the link to cytomegalovirus, a common herpes virus.

Once the virus infects an individual, it typically remains dormant for the duration of life. A majority of individuals do not experience symptoms, but a flare-up can occur during pregnancy, and the virus can be transmitted to the fetus. Side effects of this infection includes birth defects, and hearing loss in newborns, according to the study.

The researchers compared the infections of 127 children with acute lymphoblastic leukemia, and 38 children with acute myeloid leukemia. Each sample was screened for viruses and bacteria to determine whether there was a link between a certain pathogen and the cancer.

Genetic traces of cytomegalovirus were discovered in abnormal white blood cells, and virus particles in blood samples from patients with acute lymphoblastic leukemia, according to the study. However, these findings were only rarely found in patients with acute myeloid leukemia.

The researchers then tested blood samples from 268 newborns who went on to develop acute lymphoblastic leukemia, and 270 healthy newborns who did not develop cancer.

The investigators discovered that children who developed acute lymphoblastic leukemia were 3.71 times more likely to have a cytomegalovirus infection at birth, according to the study. Interestingly, Hispanic newborns were 5.9 times more likely to be cytomegalovirus-positive at birth, which is a significant finding since Hispanic people have the highest risk of developing this cancer.

If additional studies are conducted, and a link is found between cytomegalovirus (CMV) and acute lymphoblastic leukemia, the results may lead to a vaccine for the virus to prevent transmission, the researchers wrote.

“If it's truly that in-utero CMV is one of the initiating events in the development of childhood leukemia, then control of the virus has the potential to be a prevention target,” concluded lead author Stephen Francis, PhD. “That's the real take-home message.”