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

BACKGROUND

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 representatives of each poliovirus serotype (Roivainen M, Agboatwalla M, Stenvik 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 retaining the number of steps and reagents to a minimum.

STUDY

DESIGN

Replacement of radioactive labelling by in vitro biotinylation of purified virions, and detection of bound virions with horseradish peroxidase-conjugated streptavidin. To study sensitivity and poliovirus serotype-specificity, 129 sera and 115 CSF specimens from children with acute poliomyelitis 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-polio enterovirus infection were used to assess specificity.

RESULTS

While results with the new test on specimens from clinically confirmed polio patients revealed some correlation with those obtained in the in-house RIA, studies on sera from healthy adults indicated, that non-specific binding of biotinylated virions is difficult to control. Moreover, examination 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 RIA.

CONCLUSION

Cross-reactive epitopes between poliovirus serotypes and between polioviruses and other enteroviruses may compromise the use of an assay for virus-specific IgM for poliovirus diagnosis. Biotinylation of the virions seemed to aggravate these problems.