Development of a multiplex droplet digital PCR assay for detection of enterovirus, parechovirus, herpes simplex virus 1 and 2 simultaneously for diagnosis of viral CNS infections

BACKGROUND: Enterovirus (EV), parechovirus (HPeV), herpes simplex virus 1 and 2 (HSV1/2) are common viruses leading to viral central nervous system (CNS) infections which are increasingly predominant but exhibit deficiency in definite pathogen diagnosis with gold-standard quantitative PCR method. Previous studies have shown that droplet digital PCR (ddPCR) has great potential in pathogen detection and quantification, especially in low concentration samples. METHODS: Targeting four common viruses of EV, HPeV, HSV1, and HSV2 in cerebrospinal fluid (CSF), we developed a multiplex ddPCR assay using probe ratio-based multiplexing strategy, analyzed the performance, and evaluated it in 97 CSF samples collected from patients with suspected viral CNS infections on a two-channel ddPCR detection system. RESULTS: The four viruses were clearly distinguished by their corresponding fluorescence amplitude. The limits of detection for EV, HPeV, HSV1, and HSV2 were 5, 10, 5, and 10 copies per reaction, respectively. The dynamic range was at least four orders of magnitude spanning from 2000 to 2 copies per reaction. The results of 97 tested clinical CSF specimens were identical to those deduced from qPCR/qRT-PCR assays using commercial kits. CONCLUSION: The multiplex ddPCR assay was demonstrated to be an accurate and robust method which could detect EV, HPeV, HSV1, and HSV2 simultaneously. It provides a useful tool for clinical diagnosis and disease monitoring of viral CNS infections.