OBJECTIVERespiratory syncytial virus (RSV) is the most common cause of lower respiratory infection in infants. It is very important to quantitative assay of RSV titer in the study on RSV pathogenesis, candidate vaccine and antiviral treatment. Therefore, we develop Real-time Quantitative PCR (Q-PCR) assay and enzyme immunospots (EIS) for titrating RSV and compare them with traditional 50% tissue culture infectious doses (TCID50).

METHODSQ-PCR, based upon the RSV-L genes, and EIS were utilized to titrate samples from RSV culture supernatants and RSV infected mouse lungs. Then, the results were compared with TCID50.

RESULTSFor the samples from RSV culture supernatants, the ratio of Q-PCR and EIS (plaque forming unit, pfu) was 10:1 and the ratio of EIS and TCID50 was 10:1 when TCID50 was converted as pfu. For the samples from RSV infected mouse lungs, the ratio of Q-PCR and EIS was 1000:1 and the ratio of EIS and TCID50 was 5:1.

CONCLUSIONWe have successfully established Q-PCR and EIS to titrate RSV and compared them with TCID50. We concluded EIS is a cost-effective method to titrate RSV.