Development of a TaqMan real-time RT-PCR assay for the detection of rabies virus.

Diagnosis of rabies relies on the fluorescent antibody test (FAT) from brain impression smears. The mouse brain inoculation test is used to confirm FAT but requires weeks until the result is known. TaqMan real-time PCR has been described for rabies viral RNA detection; however, this is burdened by primer and probe binding site mismatches. The purpose of this study was to develop a TaqMan real-time RT-PCR assay as an adjunct to FAT, based on national data of 239 rabies nucleoprotein sequences from rabies-infected brain specimens collected between 1998 and 2003. Two showed as many as 3 mismatches. However, mismatches on primer and/or probe binding sites did not affect amplification or detection. One hundred and forty-three brain samples submitted for rabies diagnosis from all over the country between 2005 and 2007 were also tested. Results were concordant with FAT. Thirteen rabies proven samples from Myanmar, Cambodia, Indonesia and India; 3 of which had up to 7 mismatches at primer/probe binding sites, could be detectable. Challenge Virus Standard, a fixed virus strain with 4 mismatches at probe binding site, could not be detected but remained amplified. This assay could be used as an adjunct to FAT and may serve as a rabies surveillance tool.