Tick saliva may be a secret ingredient to help HIV patients

The blacklegged tick — the one that carries Lyme disease — may have some value: its spit.

The arachnid's saliva — which helps it feed on hosts by blocking blood coagulation — is now part of experiments examining ways to reduce heart disease in people living with HIV. Their risk of heart attack and stroke is nearly double that of the general population, according to a study last year. That risk was found even in people whose virus was undetectable in their blood because of antiretroviral drugs.

Chronic inflammation is suspected as the cause of the cardiovascular disease, and researchers are trying to find out what causes it, according to Ivona Pandrea, a professor of pathology in the Center for Vaccine Research at the University of Pittsburgh.

Even when HIV patients are treated with antiretroviral drugs and the virus is well controlled, Pandrea said, “patients develop other issues, co-morbidities that affect organs and systems that reduce longevity. They develop health problems that old people have. The aging process is accelerated in HIV patients. The main cause is inflammation.”

Pandrea was one of the senior authors of recently published research that says the increased heart disease risk can be linked to an overabundance of a type of immune cell in people with HIV.

Irini Sereti, of the National Institute of Allergy and Infectious Diseases, was another senior author. Her team found that people with HIV share an elevated number of the immune cells that continue to express a protein that triggers blood clotting and inflammation even after the HIV is under control.

Pandrea found the same cells in monkeys that progress to AIDS after infection with SIV, the primate form of HIV. The cells taken from a different species of monkey, which usually doesn’t develop heart disease when infected with SIV, didn’t express the protein involved with clotting and inflammation.

As reported in Science Translational Medicine, human blood samples were exposed to ixolaris, a synthetic version of the small molecule found in the saliva of the Ixodes scapularis tick, and researchers found that the protein activity was blocked. Then a small group of lab monkeys, including the two different species and both with an early infection of SIV, were treated with ixolaris.

“Both models replicated very well the virus,” Pandrea said, “but one did not have hypercoagulation; the other had high coagulation and high cardiovascular disease.” The levels of inflammatory proteins in the high-coagulation species were lowered with the ixolaris treatment.

The study concluded that “targeting the coagulation pathway in HIV-infected patients may be effective in reducing the immune activation and inflammation that are linked to cardiovascular comorbidities in HIV infection.” It may also help as therapy in other inflammatory diseases, the study said.

NIH holds the patent for ixolaris, which in the past was tested to treat blood clots in animals. More work needs to be done to confirm the research findings and to study the effectiveness and safety of treatment with the drug, Pandrea said.

Tick saliva alone isn’t a solution, however. “I wouldn’t recommend people getting bitten by ticks,” Pandrea said. “They’ll still get Lyme disease.”

Correction: Due to an editing error, an earlier version of this article referred to ticks as insects. They are arachnids.

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