A novel reporter gene assay for pyrogen detection

Fever is a systemic inflammatory response of the body to pyrogens. Nuclear factor κB (NF-κB) is a central signalling molecule that causes the excessive secretion of various proinflammatory factors induced by pyrogens. This study explored the feasibility of a novel reporter gene assay (RGA) for pyrogen detection using RAW 264.7 cells stably transfected with the NF-κB reporter gene as a pyrogenic marker. Pyrogen was incubated with the transgenic cells, and the intensity of the fluorescence signal generated by luciferase secreted by the reporter gene was used to reflect the degree of activation of NF-κB, so as to quantitatively detect the pyrogens. The RGA could detect different types of pyrogens, including the lipopolysaccharide (LPS) of gram-negative bacteria, the lipoteichoic acid (LTA) of gram-positive bacteria, and the zymosan of fungi, and a good dose-effect relationship was observed in terms of NF-κB activity. The limits of detection of the RGA to those pyrogens were 0.03 EU/ml, 0.001 μg/ml, and 1 μg/ml, respectively. The method had good precision and accuracy and could be applied to many biological products (e.g., nivolumab, rituximab, bevacizumab, etanercept, basiliximab, haemophilus influenzae type b conjugate vaccine, 23-valent pneumococcal polysaccharide vaccine, and group A and group C meningococcal conjugate vaccine). The results of this study suggest that the novel RGA has a wide pyrogen detection spectrum and is sufficiently sensitive, stable, and accurate for various applications. Importance Pyrogen testing is mandatory and a critical method to ensure the safety of parenteral products including vaccines. Currently, only two pharmacological tests, including the rabbit pyrogen test and the bacterial endotoxins test (BET), are applied to evaluate pyrogenic contamination in parenteral pharmaceuticals by most of state pharmacopoeias. Although generally reliable, both of these assays have shortcomings. The rabbit test is not quantitative but is expensive and involves the use of animals. It can also produce varying responses depending on the strain, age and housing conditions of the rabbits. The BET, however, does not detect pyrogens other than gram-negative bacterial endotoxins and is often problematic when used to test solutions with a high protein content. To overcome these shortcomings and satisfy the growing need for new methods prompted by the constantly increasing production of biological compounds, it is necessary to develop the novel assay for pyrogen detection. Highlights This novel reporter gene assay can detect different types of pyrogens, including the lipopolysaccharide of gram-negative bacteria, the lipoteichoic acid of gram-positive bacteria, and the zymosan of fungi. The novel reporter gene assay is sufficiently sensitive, stable, and accurate for various applications.