Effect of heat inactivation of serum on Bordetella pertussis antibody determination by enzyme-linked immunosorbent assay.

The effect of heat inactivation on Bordetella pertussis antibodies determined by enzyme-linked immunosorbent assay (ELISA) was studied. Sera were heated at increasing temperatures (from 30 to 50 degrees C at 5 degrees C increments and from 52 to 70 degrees C at 2 degrees C increments). Between 30 and 50 degrees C, no significant differences were observed in immunoglobin G (IgG) antibodies to pertussis toxin (PT). From 50 to 56 degrees C the antibody values were twofold higher than those of uninactivated sera; at 64 degrees C the values were 3.6- to 9.1-fold higher. The increase in PT IgG antibody values was more pronounced in sera with low antibody values. ELISA antibody values of sera from a vaccine trial were determined in unheated and heat inactivated sera. The geometric mean value (GMV) of the heat inactivated samples was 3.2 times the geometric mean value of the uninactivated sera. ELISA IgG antibodies to filamentous hemagglutinin, fimbriae-2, and pertactin were studied, and the values of heat inactivated sera did not differ significantly from the values of the uninactivated sera. Our findings indicate that heat inactivation of sera leads to higher, variable, and false-positive PT and IgG values.