Impact of antibodies against amyloidogenic transthyretin (ATTR) on phenotypes of patients with familial amyloidotic polyneuropathy (FAP) ATTR Valine30Methionine.

BACKGROUND: This study investigated whether a relationship exists between the presence of de novo antibodies and the clinical manifestations of familial amyloidotic polyneuropathy (FAP).

METHODS: Serum samples were collected from 25 Japanese and 6 Swedish FAP amyloidogenic transthyretin (ATTR) Valine30Methionine (V30M) patients, 4 asymptomatic Japanese ATTR V30M gene carriers, and 24 Japanese healthy volunteers. Study methods included enzyme-linked immunosorbent assay (ELISA) and mass spectrometry.

RESULTS: Three Japanese and 5 Swedish patients had significantly higher levels of antibodies against ATTR than did healthy volunteers and asymptomatic gene carriers (P<0.05). All 8 patients with higher antibody levels were late-onset cases. The ratio of wild-type TTR to ATTR V30M in serum from the high-antibody group was higher than that of the low-antibody group. ELISA results revealed two epitopes at positions 24-35 and 105-115 of ATTR V30M. We found a significant positive correlation between levels of the antibody at positions 24-35 and the age at FAP onset (r=0.751, P<0.05). An age-dependent increase in the occurrence of antibodies was observed in these patients with an epitope at positions 24-35.

CONCLUSIONS: These findings may help explain the differences in early- and late-onset FAP and/or the progression of FAP.