Identification of enteroviruses by indirect immunofluorescence using monoclonal antibodies

Serum neutralization (Nt) is used most often to type enterovirus isolates, but it is labor-intensive, expensive, and supplies of reference antisera for Nt are limited. Alternative methods of enterovirus typing are needed.

To investigate the use of indirect immunofluorescence (IFA) with commercially available monoclonal antibodies (MAbs) as an alternative to Nt for the identification of enteroviruses.

Two MAb blends (one for coxsackie B viruses and one for echoviruses 4, 6, 9, 11, 30, and 34) and a coxsackie A9 MAb were used to screen 465 clinical isolates over a period of two years. Virus isolates which tested positive with one of the blends were typed with the individual MAbs of the respective blend. Individual MAbs for polioviruses 1, 2, and 3 acquired late in the study were used to screen 45 viral isolates.

The antibodies identified 251/465 (54%) of the total number of isolates tested. IFA results for 451 of 465 viral isolates were in agreement with conventional identification methods. The sensitivity of the IFA screen using the MAb blends and coxsackie A9 MAb was 93% and the specificity was 99%. Thirteen discrepant isolates were negative by IFA, with twelve positive by Nt for echovirus 30 and one isolate positive by Nt for coxsackie A9. The remaining discrepant isolate was positive by IFA for both coxsackie A9 and coxsackie B5, but positive by Nt for coxsackie A9 only.

IFA is highly specific for the identification of enteroviruses, but may not be sensitive enough to identify all strains within an enterovirus type. Procedures which utilize an IFA screen and confirm final results by Nt decrease turnaround time and reduce the number of cell culture tubes required for the identification of each enterovirus isolate.