In fact, the monkeys were less likely to die early, experienced small reductions in their viral loads, and had slightly better retention of body mass. However, the study authors stated that the results are too preliminary to suggest marijuana might slow the progression of HIV.
“In terms of viral replication, disease progression, and immunological parameters, chronic use of cannabinoids may not be detrimental to the infection,” said Dr. Patricia Molina, lead author on the study.
However, she added, “It is too premature to claim that this also reflects protection or improvement of disease in HIV-positive [patients], or how this would play out in the presence of antiretroviral therapy.”
Studies have estimated that about a quarter to a third of people with HIV use marijuana to ease symptoms from HIV infection or antiretroviral therapy. Tetrahydrocannabinol (THC), the primary drug in marijuana, is available in two forms: the marijuana plant itself and two different pills, which are available by prescription.
Marijuana, which is usually smoked, is not approved by the United States Food and Drug Administration (FDA) and is illegal according to federal law. However, 15 states and Washington, D.C. have legalized use of marijuana for people with HIV.
In addition, Marinol (dronabinol), which contains THC, and Cesamet (nabilone), which contains a synthetic version of THC, are available by prescription. Marinol is approved by the FDA for the treatment of HIV-associated anorexia, while Cesamet is approved for use in treatment of anorexia and wasting in people with HIV.
Most research has shown that using marijuana or prescription THC can help ease common symptoms and side effects of antiretroviral therapy in people with HIV (see related AIDS Beacon news). However, some research has suggested that marijuana and THC may have harmful effects on the immune system, which could lead to more illnesses and faster HIV disease progression.
In this study, researchers set out to determine whether regular THC use causes faster disease progression in monkeys infected with SIV, the monkey equivalent of HIV.
Four monkeys were injected twice daily with THC starting approximately one month prior to being infected with SIV. Another four monkeys were infected with SIV but did not receive THC.
After infection, the researchers monitored immune system markers, CD4 (white blood cell) counts, and viral loads (amount of virus in the blood) over the course of 6 months. The monkeys receiving THC continued to receive the drug twice daily throughout the study period.
Contrary to the researchers’ expectations, results showed that regular THC administration did not increase viral load or lead to faster disease progression.
In fact, infected monkeys receiving THC had slightly lower viral loads than infected monkeys that did not receive THC, although the difference was too small to be significant. CD4 counts also dropped more slowly in monkeys receiving THC.
In addition, among the infected monkeys receiving THC, the first death did not occur until 11 months after infection. In that time, three of the four infected monkeys not receiving THC died: two about 5 months after infection and a third after 7 months.
Results also showed that monkeys receiving THC lost less weight 3 to 6 months after infection than monkeys not receiving THC, although the difference was too small to be significant.
The authors noted that their study was small, which means individual differences between monkeys could have played a role. Nonetheless, they concluded that THC does not increase disease progression and, in fact, regular administration of THC may actually delay SIV disease progression, possibly by reducing inflammation and weight loss.
Dr. Molina stated that additional follow-up studies on the monkeys are planned. “There are many things we are interested in pursuing, such as what happens with a longer period of exposure to THC prior to infection, can we eliminate the psychoactive effects of THC and still see protection, does THC interfere directly with viral entry into the cell, etc.,” said Dr. Molina.
The authors also plan to study the effects of THC in female monkeys (all the monkeys in this study were male) and what the biological mechanism of THC’s effects on disease progression might be.
Dr. Molina stated that they would like to replicate the results in human studies, but that this presents some challenges.
“These are difficult studies, and finding the right cohort of patients is quite complex,” said Dr. Molina. “Questions arise as to whom do we study? People on antiretroviral therapy plus cannabinoids? Do we add cannabinoids to the therapy? Do we study cannabinoid users?”
“We are interested in pursuing it, just not at that stage yet,” she added.
For more information on the study, please see the article in AIDS Research and Human Retroviruses.
Source: AIDS Beacon
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