Formaldehyde-protein conjugate-specific antibodies in rats exposed to formaldehyde

A large human population is exposed to formaldehyde (FA) environmentally and occupationally, leading to a variety of respiratory and dermatological disturbances. FA covalently binds with proteins to form FA-protein conjugates, which might lead to the formation of FA-specific antibodies. The focus of this investigation was to study the formation of antibodies against FA-protein conjugates in rats for their possible use as biological markers of FA exposure. Male Sprague-Dawley rats were fed FA via drinking water (1.6 mg/ml) for up to 6 mo. Blood was collected at 3 and 6 mo following FA exposure, and formation of anti-FA-albumin adduct (anti-FAA) antibodies measured in the serum samples (1:100 dilution) by an enzyme-linked immunosorbent assay (ELISA) using synthesized rat albumin conjugates of FA as the solid-phase antigen. Sera from FA-treated rats showed induction of antibodies to FAA in 50% of the animals at both 3 and 6 mo, and the antibody titer was higher at 6 mo, suggesting a greater antibody response with exposure period. These antibodies were highly specific for FAA as they did not cross-react with malondialdehyde-, 4-hydroxynonenal-, 4-hydroxyhexenal-, and acrolein-albumin adducts. The specificity of anti-FAA antibodies was further evaluated by inhibition studies that showed a dose-dependent decrease in binding when the serum was preincubated with increasing concentrations of FAA, and by Western blot analysis that showed immunoreactivity of the antibody with FAA but not with rat albumin. Furthermore, the anti-FAA antibodies (rat serum) also recognized FA-human albumin (FAHA) conjugates, but had only approximately one-third of the binding affinity in comparison to FAA. Induction of anti-FA-protein conjugate antibodies could be further evaluated to serve as a biomarker of FA exposure.