Utility of RT-PCR-based Dot-blot Hybridization for Detecting and Genotyping Echoviruses

ABSTRACT

We attempted to detect and identify virus types quickly by improving an RT-PCR-based dot-blot hybridization test for echoviruses, important human pathogens mainly causing aseptic meningitis. This test was applied to reference viruses of seven echovirus serotypes prevalent in Korea (E6, 7, 9, 11, 13, 25, and 30) and seventy isolates of echovirus isolated in Korea between 2002 and 2004. The primers for target DNA and hybridization probes (25mer, 50mer, and 70mer) were designed within the VP1 region of the echovirus. In RT-PCR, a nonradioactive digoxigenin-DNA labeling mix was added instead of dNTP to initiate PCR. The PCR product was then hybridized against 25mer, 50mer, and 70mer probe DNA spotted on nylon membranes and the reaction was observed. To investigate the optimal conditions for hybridization, various concentrations of target DNA (0.1, 1, 10, and 100 ng/micron l), size of probe DNA (25mer, 50mer, and 70mer), concentrations of probe DNA (10~50 pM), and reaction time were included. In the test zone, the optimal condition in terms of time and cost was a reaction time of 1 h with 10 ng/micron l target DNA concentration and 10 pM of a 50mer probe. We found 100% diagnosis of the serotypes for seven reference echoviruses and 90% (63/70) sensitivity for clinical isolates. Also, tests with this probe for reactivity with seven reference echoviruses by using DNA chips showed that diagnostic identification was possible without other serotype cross-reactivity. Therefore, efficiency analysis of probe and target DNA on clinical specimens by using dot-blot analysis indicated that this system can be applied to the prestages of the DNA chip and that the dot blot analysis itself can be used in applications to develop a tool for diagnosing specific viral serotypes.