In vitro assay of biological and chemical toxins using antibodies against lethal toxin neutralizing factor

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.