Researchers in Japan are developing a vaccine that may someday replace the daily pill people take for hypertension.

Scientists in Japan are developing a vaccine that someday may be able to lower blood pressure for up to six months, according to new research published today in Hypertension, the journal of the American Heart Association.

The researchers have concluded a long-term study with rats that they say may lead to a breakthrough treatment for people with high blood pressure, one that would be a lower cost alternative to taking a daily pill.

Dr. Hironori Nakagami, Ph.D., a professor at Japan’s Osaka University and co-author of the study, said, “The potential of a vaccine for hypertension offers an innovative treatment that could be very effective for the control of non-compliance, which is one of the major problems in the management of hypertensive patients.”

The DNA vaccine created by Nakagami and his colleagues works similarly to common angiotensin-converting enzyme (ACE) inhibitor medications. It targets angiotensin II, a hormone that constricts blood vessels and consequently raises blood pressure. Higher blood pressure forces the heart to work harder.

In the Osaka study, researchers used needleless injections to inoculate hypertensive rats three times at two-week intervals. The vaccine lowered the rats’ blood pressure for up to six months and it reduced tissue damage to the heart and blood vessels, which is associated with hypertension.

The scientists found no other signs of organ damage, such as in the kidney or liver. Other studies have tested vaccines for hypertension, but none had lasting results and some had adverse side effects.

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Medical science has been searching for a vaccine alternative to treating hypertension since the mid-1980s, according to Dr. Ernesto L. Schiffrin, C.M., Ph.D., an associate editor of Hypertension.

He is a clinician-scientist who does research in vascular disease and hypertension at the Jewish General Hospital and the Lady Davis Institute at McGill University in Montreal, Canada.

He noted that vaccine tests on humans still need to be done.

“Though no side effects have been noted in the rats,” he said, “the vaccine’s use in humans could result in side effects.”

In addition, while the vaccine controlled blood pressure in rats for up to six months, “we do not know how long the effect would last in humans.”

Schiffrin said non-compliance — the failure of patients to take medications or follow a course of treatment — is also a concern.

“[It’s] a very complex issue,” he said. “The relationship between healthcare professional and patient, cultural and economic factors, and side effects all conspire to reduce compliance.”

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Other factors, Schiffrin said, also make it difficult for physicians to control hypertension in their patients: “Diet, excess salt in food, lack of exercise, overweight and obesity, and excessive alcohol consumption.”

The goal for an anti-hypertensive vaccine is to improve a patient’s medication compliance and to achieve ideal blood pressure. In Africa, South Asia, and other developing regions, current hypertension medications such as angiotensin receptor blockade (ARB) are costly. The prospect of a future DNA vaccine, with a potentially lower cost, is highly desirable.

“Further research on this DNA-vaccine platform, including increasing the longevity of blood-pressure reduction, may eventually provide a new therapeutic option to treat hypertensive patients,” Nakagami said.

In addition, the technology could be used to create other vaccines.

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