An experimental drug made from tick saliva may hold promise as a potential treatment for reducing HIV-linked heart disease risk, a study has found. Scientists at the University of Pittsburgh and National Institutes of Health (NIH) in the US have found a clue to why people living with HIV have double the likelihood of developing heart disease.
The increased heart disease risk is driven by a subset of immune cells in people with HIV which continue to express a protein that triggers blood clotting and inflammation even after the HIV virus is under control by medication, they said. The researchers found that Ixolaris, an experimental drug isolated from tick saliva and previously tested to treat blood clots in animals, successfully reduced the inflammation in monkeys infected with SIV, the primate form of HIV.
"This treatment has the potential to improve the clinical management of HIV-infected patients and help them to live longer, healthier lives with HIV," said Ivona Pandrea, professor at Pitt's Center for Vaccine Research. "By uncovering one of the cellular mechanisms driving the heart disease, we can look for medications - such as Ixolaris - that specifically target and disrupt that mechanism," said Pandrea, senior author of the study published in the journal Science Translational Medicine.
Irini Sereti, of the NIH's National Institute of Allergy and Infectious Diseases (NIAID), tested blood samples from people without HIV, people with HIV whose infections were well-controlled by antiretroviral therapy and people with HIV who were not on the medications. The researchers found an elevated number of immune cells called monocytes that expressed high levels of the 'tissue factor' protein, which is associated with blood clotting and other inflammatory proteins, in the blood from people with HIV, regardless of how well their infection was controlled.
These findings were confirmed by Pandrea and her team in monkeys that progress to AIDS after infection with SIV. The same cells isolated from a different species of monkey that usually does not develop heart disease when infected with SIV do not produce tissue factor, thus reinforcing the role of this damaging protein in triggering cardiovascular disease in the HIV/SIV settings.
The scientists then exposed the human blood samples to Ixolaris and observed that the drug blocked the activity of tissue factor. When tested in a small group of monkeys during early SIV infection, the treatment significantly lowered the levels of inflammatory proteins linked to cardiovascular diseases.