Cannabis made vaccinia virus infections worse in mice by suppressing immune function
A single dose of cannabis resin enhanced the severity and duration of vaccinia virus infection in mice, while in vitro experiments showed cannabis compounds inhibited immune cell proliferation.
Quick Facts
What This Study Found
Researchers found that a single dose of cannabis resin was equally effective as pure THC at increasing the severity and duration of vaccinia virus (smallpox vaccine virus) infection in mice.
In vitro, cannabis resin was more potent than THC alone at inhibiting immune cell proliferation, suggesting additional cannabis compounds beyond THC contributed to immunosuppression. Sub-fractions containing cannabidiol and cannabinol (also found in cigarette smoke) were also inhibitory.
The immunosuppressive effects were distinct from direct cell-killing (apoptotic) effects, as drug-treated immune cells retained their ability to produce cytokines when stimulated.
The authors noted a recent case of unusually severe cowpox infection in a young drug user, and concluded that cannabis could increase risk of acquiring poxvirus infections or experiencing worse vaccine side effects.
Key Numbers
Single dose of cannabis resin or THC enhanced vaccinia symptoms. Cannabis resin was superior to THC alone at inhibiting immune cell proliferation in vitro. CBD and CBN fractions also showed inhibitory effects.
How They Did This
Animal study and in vitro experiments. Mice infected with vaccinia virus after cannabis resin or THC administration. In vitro immune cell proliferation assays with human and mouse spleen cells and PBMCs. Sub-fractionation of cannabis resin to identify active components.
Why This Research Matters
The finding that cannabis enhanced viral infection severity had implications for immunocompromised individuals and vaccination programs, suggesting cannabis users might face increased infection risks.
The Bigger Picture
This study added to evidence that cannabis has meaningful immunosuppressive effects that could have real clinical consequences, particularly for susceptibility to viral infections.
What This Study Doesn't Tell Us
Mouse model with vaccinia virus, which has limited relevance to most modern infections. Single-dose exposure protocol. In vitro immune effects may not fully translate to in vivo immune function.
Questions This Raises
- ?Do cannabis users have increased susceptibility to common viral infections?
- ?Should vaccination protocols consider cannabis use status?
Trust & Context
- Key Stat:
- Cannabis compounds beyond THC contributed to immune suppression
- Evidence Grade:
- Animal and in vitro study with mechanistic component identification but limited clinical relevance of the vaccinia model.
- Study Age:
- Published in 2011. Cannabis immunology research has continued with more clinically relevant infection models.
- Original Title:
- Cannabinoids lead to enhanced virulence of the smallpox vaccine (vaccinia) virus.
- Published In:
- Immunobiology, 216(6), 670-7 (2011)
- Authors:
- Huemer, Hartwig P, Lassnig, Caroline, Bernhard, David, Sturm, Sonja, Nowotny, Norbert, Kitchen, Maria, Pavlic, Marion
- Database ID:
- RTHC-00491
Evidence Hierarchy
Tests effects in animals (usually mice or rats), not humans.
What do these levels mean? →Frequently Asked Questions
Does cannabis make you more susceptible to infections?
In this study, cannabis enhanced the severity of a viral infection in mice and suppressed immune cell function in the lab. Whether this translates to increased infection risk in human cannabis users requires further study.
Is it just THC that suppresses the immune system?
No. Cannabis resin was more immunosuppressive than pure THC, and sub-fractions containing CBD and CBN also inhibited immune cells, suggesting multiple cannabis compounds contribute.
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Cite This Study
https://rethinkthc.com/research/RTHC-00491APA
Huemer, Hartwig P; Lassnig, Caroline; Bernhard, David; Sturm, Sonja; Nowotny, Norbert; Kitchen, Maria; Pavlic, Marion. (2011). Cannabinoids lead to enhanced virulence of the smallpox vaccine (vaccinia) virus.. Immunobiology, 216(6), 670-7. https://doi.org/10.1016/j.imbio.2010.11.001
MLA
Huemer, Hartwig P, et al. "Cannabinoids lead to enhanced virulence of the smallpox vaccine (vaccinia) virus.." Immunobiology, 2011. https://doi.org/10.1016/j.imbio.2010.11.001
RethinkTHC
RethinkTHC Research Database. "Cannabinoids lead to enhanced virulence of the smallpox vacc..." RTHC-00491. Retrieved from https://rethinkthc.com/research/huemer-2011-cannabinoids-lead-to-enhanced
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.