Researchers make strides in fight against bovine leukemia virus

June 20, 2017

Bovine leukemia is a scary topic for beef ranchers and dairy farmers, and for good reason. But now, researchers in northern Japan have made a discovery that might help fight against bovine leukemia virus (BLV) and other infectious cow diseases in the future.

The virus that causes the contagious disease, BLV, is a retrovirus of cattle. It currently has no successful vaccine or treatment program.

Retroviruses, like HIV, are viruses that enter a host cell and transcribe their own RNA into the cell’s DNA. From there, they make copies of themselves in the organisms they infect. It’s hard to attack retroviruses with drugs because the exact sequence of a retrovirus’s RNA changes often. The work of the Japanese team will hopefully make that fight a little easier.

Antibody plan in Japan

Researchers from Hokkaido University, Tohoku University and the Hokkaido Research Organization have developed an antibody that has been found to reduce the virus count in BLV-infected cattle.

“The new antibody could pave the way for developing biomedicines that effectively treat cows infected with BLV,” said Satoru Konnai of Hokkaido University. “Such biomedicines are also expected to reduce the use of antibiotics or steroids in other intractable infectious diseases. We plan to conduct animal experiments this year to verify if our antibodies are effective in treating other diseases.”

In an earlier study, the same team found that T-cell lymphocytes, a type of white blood cell that fights infections, are suppressed by an interaction between the cell surface receptor PD-1 and its ligand, PD-L1, when infected with BLV. The researchers developed an antibody for the ligand to block the receptor/ligand interaction, therefore helping the T-cells continue to fight infections.

In the newest study put out by the team, rats were used to engineer an antibody for the receptor PD-1 instead of the ligand. After that antibody proved to be unstable in the tested cow’s body, the team formed an anti PD-1 “rat-bovine” chimeric antibody. When administered, the new antibody blocked the binding between PD-1 and PD-L1, reinvigorating the immune response and actively decreasing the virus count in the cow.

A worldwide problem

BLV is one of the most common types of bovine cancers in the world, infecting up to 35% of cows in Japan alone, according to Hokkaido University. It causes cattle to develop too many lymphocytes. This condition, called lymphocytosis, affects infected cows for the remainder of their lives, weakening their immune systems.

BLV is associated with a decrease in milk production and an increase in disease which may cause the animal to need to be culled. A portion of cattle with BLV will develop lymphoma if the infected lymphocytes form tumors. Once a cow reaches that point, the disease is ultimately fatal.