Antigenicity evaluation of lac color and exploratory study for identifying potential biomarkers of anaphylaxis

Lac color, a natural red dye derived from the larvae of laccifer lacca kerr, is one of the most commonly used substances in food. To date, no studies have reported on the antigenicity of lac color and the other biomarkers that can determine anaphylactic reactions. To address this, we evaluated the antigenicity of lac color through active systemic anaphylaxis (ASA) in addition to identifying potential biomarkers performing exploratory studies. For ASA test, Guinea pigs (n = 5) were sensitized with 0(negative control), 4 mg/kg of lac color, 4 mg/kg of lac color + FCA, and 5 mg/kg of ovalbumin + FCA (positive control) 3 times a week for three weeks. Fourteen days after the last sensitization, animals were challenged intravenously weekly for two weeks. Hematological and histopathological analyses were performed and compared to control groups.

In the ASA test, all lac color groups showed mild symptoms such as nose rubbing, urination, and evacuation, which are insufficient indicators of anaphylaxis. Exploratory studies identified several biomarkers: decreased platelet count, and increased basophil count; distention in the lung, and redness on the inner wall of trachea; mononuclear inflammatory cell infiltration (MICI) in the ear, and heart hemorrhage. When these biomarkers were applied to the ASA test of lac color, in comparison to the negative control group, the positive control group (ovalbumin + FCA) showed a significant over 60-fold reduction in platelet count and nearly threefold higher basophil count compared to other groups. Furthermore, only positive control group exhibited full lung distention and severe redness on the inner wall of the trachea. Mononuclear inflammatory cell infiltration (MICI) in the ear was about three times higher, and heart hemorrhage was only present in the positive control group compared to others. None of the lac color groups were different from the negative control group (p > 0.05), whereas the positive control group was significantly different (p < 0.05).

Our study concludes that lac color, at the tested concentrations, does not induce antigenicity in the guinea pig model, providing valuable safety data. Furthermore, the biomarkers identified in this study offer a supportive approach to evaluating the immunogenicity of substances in future research.