Lethal Toxin Neutralizing Factor (N-LTNF), MW 63.0 kDa, was isolated from opossum serum. After trypsin digestion, the active domain of N-LTNF was isolated and sequenced. The synthetic peptide consisting of ten amino acids was designated as LT-10. N-LTNF and LT-10 inhibited the lethality of animal, plant and bacteria toxins when tested on mice non-immunologically. The antibodies against N-LTNF and LT-10 only reacted immunologically with toxins and not with non-toxic substances. Anti-LTNF and anti-LT-10 reacted immunologically by ELISA test with toxins that were not detected by mouse test, such as cholera toxin and digoxin. Anti-LTNF and anti-LT-10 failed to react immunologically with non-toxic substances, such as nerve growth factor and collagen. Currently, mouse bioassay is in use for toxin detection and assay. Binding affinity of IgG from anti-LT-10 showed a linear relationship with mouse bioassay by ELISA detection limit to some toxins only. This may be due to the fact that anti-LTNF and anti-LT-10 detected the toxins that were not lethal to mouse. Thus, anti-LTNF and anti-LT-10 can be useful in assaying toxins as an alternative to mouse bioassay.
antibodies; in vitro assay; lethal toxin neutralizing factor; toxins; venoms