Researchers in Germany have hidden vaccine-grade measles virus inside artificially generated blood cells in order to devise a search-and-destroy therapy for human brain cancer that can?t be “seen” by the immune system.
They say their mouse experiments show a proof of principle that this non-pathogenic virus can attack glioma by getting inside tumor cells and replicating, destroying the common brain tumors from the inside out. This and other so-called “oncolytic” viruses are already being tested in clinical trials, but their effectiveness has been limited by an immediate human immune response, the researchers say.
“In an immune-competent patient, the immune system will fight the virus, and most adults are immune against measles since they have been vaccinated against the disease in childhood or have had measles,” said Christian Beltinger, M.D., an associate professor at the University Children?s Hospital in Ulm. “Although cancer patients are immune-compromised by their disease or because of therapy, they still may mount a sufficient attack against vaccine measles virus.”
To trick this immune surveillance, the researchers generated blood outgrowth endothelial cells (BOECs), which are produced outside of the body using human blood bathed in a cocktail of growth factors. “They do not naturally occur in the blood, but they are derived from endothelial progenitor cells, rare cells that are produced in the bone marrow and shed into the blood,” Dr. Beltinger said.
These cells are well suited for cancer therapy for two reasons, he said. If a vaccine measles virus is tucked within them, it can?t be reached by the immune system?s neutralizing antibodies. Also, they are endothelial progenitor cells, which are recruited in the body wherever new blood vessels are formed.
“Tumors need vessels to grow, hence they recruit these blood progenitor cells,” Dr. Beltinger said. “That makes them home to the tumors.”
BOECs have been used for other gene therapeutic approaches, such as for hemophilia, but this is the first time they have been adapted to carry vaccine measles virus, he said.