Problems with biotin-labelled virions as probes in poliovirus-specific mu-capture-IgM assays

Backround: we have previously developed a mu-capture-based radioimmunoassay (RIA) for detecting virus-specific IgM for the diagnosis of poliomyelitis. To probe captured IgM we used radiolabelled, purified preparations of repr esentatives of each poliovirus serotype (Roivainen M, Agboatwalla M, Stenvi k M, Rysa T, Akram DS, Hovi T. J Clin Microbiol 1993;31:2427-32). However, this assay is not directly applicable for wider use because preparation and handling of radioactive reagents is cumbersome and potentially hazardous. Objectives: to develop a non-radioactive modification of the assay retainin g the number of steps and reagents to a minimum. Study design: replacement of radioactive labelling by in vitro biotinylatio n of purified virions, and detection of bound virions with horseradish pero xidase-conjugated streptavidin. To study sensitivity and poliovirus serotyp e-specificity, 129 sera and 115 CSF specimens from children with acute poli omyelitis were used in comparative tests with the in-house RIA. In addition , sera from 40 healthy adults and 11 paired sera from patients with non-pol io enterovirus infection were used to assess specificity. Results: while results with the new test on specimens from clinically confi rmed polio patients revealed some correlation with those obtained in the in -house RIA, studies on sera fi-om healthy adults indicated, that non-specif ic binding of biotinylated virions is difficult to control. Moreover, exami nation of sera from patients with non-polio enterovirus infection suggested frequently occurring cross-reactivity between immune responses induced by polio- and other enterovirus infections. The latter were also seen in the R IA. Conclusion: cross-reactive epitopes between poliovirus serotypes and betwee n polioviruses and other enteroviruses may compromise the use of an assay f or virus-specific IgM for poliovirus diagnosis. Biotinylation of the virion s seemed to aggravate these problems. (C) 1999 Elsevier Science B.V. All ri ghts reserved.