A novel approach to enterovirus typing.

A novel method was developed for typing enteroviruses producing cytopathic effect. Monolayers of primary or secondary rhesus monkey kidney cells were prepared and covered with an agarose overlay. Wells were formed in the agarose, the well bottom being optimally determined to be 3 mm from the monolayer and homotypic enterovirus antiserum, intersecting antiserum pool or antiserum-diluent as control was added. After 2 h at 37 degrees C, the test virus isolate was added to each well. Cultures were incubated at 37 degrees C and were examined daily until cytopathic effect was readily observed in the control well. Monolayers were fixed and stained for macroscopic reading. Enterovirus identity based on the inhibition of cytopathic effect was confirmed with a conventional micro-neutralization method. In all, 51 enterovirus isolates were typed. Included were 21 polioviruses, 9 coxsackieviruses and 21 echoviruses, all of which were correctly identified. This method takes advantage of the ability of enterovirus and antibody to diffuse through agarose. It is simple to perform. It does not require preliminary titration of the test virus isolate and tolerates 1,000 fold fluctuations in virus concentration, thereby offering laboratories a more rapid and efficient means of typing enteroviruses.