Natwral lethal toxin neutralizing factor (N-LTNF), rmoiecular wcight 63.0 kDa,
7uas isolated from opossum serum. Afer trypsin digation, the active domain
of N-LTNF was isolated and sequenced. A synthetic peptide cor~sisting of 10
amino acids frwm the N-LXVF was designated as LTIO. N-LTNF and LT
10 inhibited the iethality of toxins frwm an%mals, plants, and bacteria when
tested in mice by a non,-kmmunological ~mechanism. Howmer, the antibodies
against N-LTW and LTIO reacted zmmunolog2'cally with toxins only and not
with nontoxic substances. Anti-LTW and anti-LTlO detected toxins in an
ELISA assay that were not detected by a mouse toxicity test, includir~gc holera
toxin and digoxin. EUrthermore, anti-N-LTNF and anti-LTl0 faiied to react
i n ~ ~ ~ u n o l o c awl iltyh no~tox i rs ubstances, nerue growth factor and collagen.
Currently, the mouse bioassay is sta~dard practice for detection and assay of
tox%ns. Binding afJinity of anti-LTlO, measured as the ELISA detection h i t ,
showed a linear relationship ruith the mouse bioassay. In addition, anti-LTlO
detects toxins that are not lethal to rnice. Th,us, anti-LTl O ,muy poue useful in
assaying toxins as an alternative to ,mouse bioassay.