The reverse transcription-polymerase chain reaction (RT-PCR) gene assay, as well as electron microscopic examination, is commonly used to detect Norwalk-like viruses (NLVs). Types and number of primer pairs used are considered to be of critical importance for efficiency of the RT-PCR detection. This study was performed to determine primer pairs useful for the detection of NLVs.
NLVs genes were detected by RT-PCR in 48 cases in Yamanashi Prefecture between December 1997 and March 2000. The probe type of the gene was G2P-C in 21, G2P-B in 10, G2P-A in 6, G1P-A in 3, G1P-B in 2, and a mixture of G2P-A and G2P-B in 6. The NLVs genes of G2P-C and G2P-B were estimated to have undergone mutation in the polymerase region and poorly specific to the primer pair 35/36, a combination that has been used most commonly for the RT-PCR assay in Japan.
The primer pair G2R1/F1 that amplifies the capsid (CAP) region of NLVs genes can detect all NLVs genes of the Genogroup 2. The combination of this primer pair with another primer pair G1R1/Fl, which like G2R1/F1, amplifies the CAP region, makes discrimination between NLVs of different groups possible. Consequently, this combination, may be the most useful for the NLVs detection by RT-PCR.