Chronic THC Did Not Worsen SIV Infection in Monkeys and May Have Reduced Mortality | Research

The takeaway

Long-term daily THC administration in monkeys infected with the primate equivalent of HIV did not enhance viral replication or worsen immune decline, and fewer THC-treated animals died compared to controls.

Read this if you have HIV and use or are considering cannabis, and want to know whether it affects disease progression.

428 days of daily THC did not increase viral loads or worsen immune decline in SIV-infected monkeys.

What the researchers found

Sixteen male Chinese-origin rhesus macaques were divided into four groups and treated with daily THC or placebo for 428 days. After one month of THC/placebo, half of each group was infected with a pathogenic strain of SIV (the primate equivalent of HIV).

Chronic THC did not increase viral loads: peak and steady-state plasma viral levels were comparable between THC-treated and placebo-treated infected animals. All infected macaques showed similar immune decline regardless of THC treatment, including drops in CD4/CD8 ratios and CD4+ T cell counts.

THC treatment significantly reduced the frequency of circulating IgE+ B cells, a finding with potential relevance to allergic and inflammatory conditions.

During the study period, only one THC-treated infected animal died, compared to two deaths in the placebo-infected group. While the numbers are too small for statistical conclusions, the trend aligns with previous studies in Indian macaques showing THC did not worsen and may have reduced SIV-related mortality.

Why it matters

THC (as Marinol) is used as an appetite stimulant for AIDS patients, but whether THC affects HIV progression has been a concern. This study, using a primate model with a brain-tropic SIV strain causing neuroAIDS, provides reassurance that chronic THC does not worsen viral infection and may have modest immunomodulatory benefits.

The numbers in context

16 macaques. 428 days of treatment. THC dose: 0.32 mg/kg IM twice daily. No significant differences in peak or steady-state viral loads. THC significantly reduced IgE+ B cell frequency. Deaths: 1/4 THC+SIV+ vs 2/4 placebo+SIV+.

How the study worked

Controlled primate study. 16 male Chinese-origin rhesus macaques in 4 groups (THC+SIV+, THC+SIV-, placebo+SIV+, placebo-SIV-). THC administered intramuscularly at 0.32 mg/kg twice daily for 428 days. SIV challenge performed one month after starting THC/placebo. Viral loads, immune markers, and IgE+ B cells monitored throughout.

What this study cannot tell us

Very small sample size (4 per group). The SIV strain used was a brain-tropic isolate from Chinese macaques, which may not represent all HIV subtypes. Chinese-origin macaques may respond differently to SIV than Indian-origin macaques used in previous studies. The THC dose and route (intramuscular) may not reflect human cannabis use patterns.

How to read the evidence

Moderate evidence from a controlled primate study with a relevant disease model, though severely limited by the small sample size (4 per group).

When this study was published

Published in 2016. Cannabis use among people living with HIV continues to be studied for both safety and potential therapeutic benefits.

The bigger picture

The safety of cannabis use in people living with HIV has been a longstanding question. This study, along with previous work in Indian macaques, consistently shows THC does not accelerate disease progression and may have protective immunological effects, supporting the safety of cannabinoid use in this population.

Questions still open

What mechanism reduces IgE+ B cells, and is this clinically beneficial? Would higher THC doses or longer exposure change the outcome? Does the trend toward lower mortality in THC-treated animals reflect a real protective effect? Would CBD or other cannabinoids show similar or better results?

Common questions

Does cannabis make HIV worse?

This primate study found that chronic THC administration did not increase viral levels or accelerate immune decline in SIV-infected monkeys. Fewer THC-treated animals died, though the study was too small to draw definitive conclusions.

Is it safe to use cannabis with HIV?

This and similar primate studies have consistently found that THC does not worsen SIV/HIV progression. THC (as Marinol) is already approved for AIDS-related appetite loss. However, individual health decisions should be made with a healthcare provider.

Read the original research

Chronic Δ(9)-Tetrahydrocannabinol Administration Reduces IgE(+)B Cells but Unlikely Enhances Pathogenic SIVmac251 Infection in Male Rhesus Macaques of Chinese Origin.

Journal of neuroimmune pharmacology : the official journal of the Society on NeuroImmune Pharmacology, 11(3), 584-591

View on PubMed ↗Publisher’s paper ↗

Citation

Wei, Qiang; Liu, Li; Cong, Zhe; Wu, Xiaoxian; Wang, Hui; Qin, Chuan; Molina, Patricia; Chen, Zhiwei. (2016). Chronic Δ(9)-Tetrahydrocannabinol Administration Reduces IgE(+)B Cells but Unlikely Enhances Pathogenic SIVmac251 Infection in Male Rhesus Macaques of Chinese Origin.. Journal of neuroimmune pharmacology : the official journal of the Society on NeuroImmune Pharmacology, 11(3), 584-591. https://doi.org/10.1007/s11481-016-9674-9