A simple and quick method for enhanced detection of specific IgE in serum from lymphatic filariasis patients

A new simple and quick technique, using a suspension of protein A agarose b eads to absorb IgG4 from sera prior to determination of filarial-specific I gE in ELISA, is presented. The optimal ratio between serum and absorbant wa s determined by absorbing fixed volumes of sera from individuals from a Wuc hereria bancrofti endemic area with different volumes of the protein A agar ose bead suspension and testing supernatants for filaria-specific IgG4 and IgE. The effect of absorption on measured IgG4 and IgE intensities in sera from various categories of individuals from the endemic area was thereafter examined. Overall, absorption resulted in a 96.5% decrease in mean ELISA O D values for IgG4 and a 41.6% increase in mean ELISA OD values for IgE. Hig her increases in IgE measurements were seen with sera from circulating fila rial antigen (CFA) negative individuals (64.7%), microfilaria (mf) negative individuals (56.1%) and individuals with chronic filarial disease (62.7%) than with sera from individuals who were CFA positive (23.4%), mf positive (10.0%), or without chronic disease (36.5%). These differences indicate tha t the degree to which IgE detection in unabsorbed serum is blocked by IgG4 varies with infection and disease status. Absorption of IgG4 from serum wit h a protein A agarose bead suspension prior to measurement of specific IgE is a useful alternative to conventional gel column absorption methods, part icularly when processing many samples. (C) 2001 Elsevier Science B.V. All r ights reserved.