A cell-based alternative to the mouse potency assay for pharmaceutical type E botulinum antitoxins

Area of Science:

• Biotechnology
• Toxicology
• Immunology

Background:

• The standard pharmacopeia mouse neutralization assay (PMNA) for botulinum antitoxin potency requires numerous mice.
• There is a critical need for an alternative in vitro method to reduce animal usage.

Purpose of the Study:

• To develop and validate an in vitro SiMa cell line-based neutralization assay (SBNA) as a replacement for the PMNA.
• To assess the SBNA's ability to determine the potency of therapeutic antitoxins against type E botulinum neurotoxin (BoNT/E).

Main Methods:

• Developed an in vitro SBNA using SiMa cells and measuring residual BoNT/E activity via ELISA for SNAP-25 cleavage.
• Quantified antitoxin potencies using both a cutoff value and nonlinear regression of a standard curve.
• Validated SBNA results against the established PMNA.

Main Results:

• The SBNA accurately determined antitoxin potencies, comparable to the PMNA (average %RE ~16%).
• Achieved high correlation between SBNA and PMNA results (r = 0.99 for standard curve, r = 0.97 for cutoff).
• Successfully determined the neutralizing activity of next-generation equine and rabbit antitoxins in vitro.

Conclusions:

• The SBNA is a viable in vitro alternative to the PMNA for botulinum antitoxin potency determination.
• The SBNA significantly reduces the reliance on animal testing for pharmaceutical antitoxin approval.
• This assay offers a more ethical and potentially cost-effective method for antitoxin characterization.