ELISA to evaluate plasma anti-asparaginase IgG concentrations in patients with acute lymphoblastic leukemia

The development of antibodies to asparaginase may attenuate the pharmacolog ic effect of asparaginase treatment, may be associated with hypersensitivit y reactions, and may necessitate switching to a different commercial aspara ginase preparation for current or future therapy. Thus, development of an E LISA for measurement of anti-asparaginase antibody levels is important in t he clinical setting. An anti-asparaginase antibody reference was establishe d by screening 65 plasma samples from six patients with acute lymphoblastic leukemia (ALL) who had recently developed a hypersensitivity reaction to E scherichia coli or Erwinia chrysanthemi asparaginase therapy. Twenty-one pl asma samples were selected for the anti-asparaginase antibody reference poo l. Five micrograms per milliliter of commercial E. coli and Erwinia asparag inase and 10 mu g/ml of E. coli asparaginase conjugated with polyethylene g lycol (PEG asparaginase) were found to be optimal as coating antigen concen trations. Anti-asparaginase antibody concentrations were determined using a commercial polyclonal goat anti-human IgG horseradish peroxidase conjugate . The antibody reference curves were linear in a range of absorbance from 0 .1 to 1.5 O.D, units for dilutions from 1:1600 to 1:51,200, Inter-assay coe fficients of variation were 9.04, 14.7 and 13.0%, and intra-assay coefficie nts of variation were 1,44, 4.43 and 3.28% for antibodies against E. coli, Erwinia, and PEG L-asparaginase, respectively. The cut-off for positivity i n plasma was determined as mean+2 S.D. of the optical density values for pl asma from untreated healthy volunteers. Measurement of specific IgG by this ELISA allows for the evaluation of plasma anti-asparaginase antibody conce ntrations in patients receiving one or more of the multiple commercial L-as paraginase preparations. (C) 2000 Elsevier Science B.V, All rights reserved .