Can s 3
Summary
Despite the widespread use of cannabis, descriptions of genuine IgE-dependent allergic reactions are relatively rare. However, several European surveys have suggested that Can s 3, a nonspecific lipid transfer protein of Cannabis sativa, may be an important cannabis allergen. As such, is the best studied and characterized cannabis protein in the context of allergic reactions. Passive inhalation of smoke from C. sativa without any previous active exposure can lead to sensitization to Can s 3 and other nsLTP allergens. Additionally, both the severe phenotype and the extensive cross-reactivity associated with cannabis allergy can be attributed to the physiochemical properties of Can s 3. Recent studies have suggested clinically-relevant sensitization also occurs in North America and Northern Europe, with broadly similar nsLTP sensitization profiles to those seen in Mediterranean areas.
Epidemiology
Worldwide distribution
Several European surveys have suggested that Can s 3, a nonspecific lipid transfer protein (nsLTP) of Cannabis sativa, may be an important cannabis allergen.
A case-control study in Belgium reported that 11/12 patients with cannabis allergy (median age 29 years, range 5–41; 6 males) were sensitized to nsLTP. In a subsequent study in Belgium, up to 72% of 120 patients with cannabis allergy reporting likely-anaphylaxis were sensitized to Can s 3 (median age 29.2 years; 48% male). In this study, patients were categorized “likely-anaphylactic” if they presented with generalized symptoms to cannabis in two or more organ systems (e.g. respiratory, gastrointestinal, cardiovascular and/or cutaneous).
In Spain, a survey of the sensitization profiles of patients diagnosed with primary cannabis allergy (mean age 26 ± 9 years; 97 men) found that 95.3% (124/130) of sensitized patients showed a response to cannabis LTP. These patients were diagnosed with cannabis allergy following positive skin prick test (SPT), specific IgE and bronchial challenge.
However, cannabis-sensitive individuals may not necessarily be sensitized to Can s 3. A study in the United States reported on the sequencing of allergens from 23 patients with a positive SPT to a crude extract of C. sativa, none of whom were sensitized to Can s 3.
Clinical Relevance
Disease severity
Despite the widespread use of cannabis, descriptions of genuine IgE-dependent allergic reactions are relatively rare, with under-reporting of symptoms likely to be a result of the illegal status of cannabis in most jurisdictions worldwide. However, reports indicate that the prevalence of IgE-mediated cannabis allergy is increasing, and will continue to increase in the future, due to decriminalization and increasing social, medical and occupational exposure to C. sativa.
Cannabis allergy can significantly impact quality of life and manifest severe and generalized symptoms with extensive cross-reactions to other plant-derived foods and substances containing nsLTPs. Allergic diseases associated with C. sativa include allergic rhinitis, asthma, allergic conjunctivitis, eczema, food allergy, drug eruption, contact urticaria and anaphylaxis.
Passive inhalation of smoke from C. sativa without any previous active exposure can lead to sensitization to Can s 3 and other nsLTP allergens. Additionally, both the severe phenotype and the extensive cross-reactivity associated with cannabis allergy can be attributed to the physiochemical properties of Can s 3.
Diagnostics
In vitro diagnosis
Multiple reports have described the use of specific IgE (sIgE) quantifications for cannabis using either crude cannabis/hemp extracts or purified/recombinant components (reviewed in:). Diagnostics based on crude cannabis products or extracts can yield clinically irrelevant results, irrespective of the methodology used, with relatively low specificity and positive test results in a significant number of cannabis tolerant individuals, especially in multi-sensitized individuals. On the other hand, the use of component-based diagnostics entails a risk of false-negative results as it is unlikely that all cannabis allergic individuals are sensitized to a single component of cannabis.
An assessment of the performance of five cannabis diagnostic tests (e.g. sIgE hemp, sIgE and BAT with a recombinant Can s 3 protein from C. sativa (rCan s3), BAT with a crude cannabis extract, and a skin prick test (SPT) with an nCan s 3-rich cannabis extract), concluded that the most effective and practical tests to confirm cannabis allergy are the SPT with an nCan s 3-rich extract and the sIgE rCan s 3. These authors also noted that a negative test result with the sIgE hemp assay could serve as a suitable diagnostic in central Europe to exclude the risk of cannabis allergy (only 18% of individuals with cannabis allergy had negative sIgE hemp results).
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