自2019年冠状病毒病(COVID-19)爆发以来,实验室诊断主要采用逆转录聚合酶链反应(RT-PCR).检测收集的样品中是否存在感染性病毒对于分析一个人是否可以传播传染性严重急性呼吸道综合症冠状病毒2(SARS-CoV-2)至关重要。然而,尚未对临床样本中的传染性SARS-CoV-2进行定量研究。因此,在本研究中,使用过氧化物酶-抗过氧化物酶技术开发了一种快速且简单的焦点形成测定法,以量化来自COVID-19患者的119个样本(n=52,鼻咽拭子[NPS];n=67,唾液)中的传染性SARS-CoV-2滴度。此外,将研究结果与实时RT-PCR的循环阈值(Ct)值进行比较。NPS样本中的感染性病毒滴度与Ct值呈负相关,当Ct值超过30时,检测不到感染性病毒。相比之下,唾液中感染性病毒滴度与Ct值之间的相关性较低(r=-0.261,p=0.027).此外,唾液中的感染性病毒滴度明显低于NPS样本。COVID-19症状出现10天后,传染性病毒无法检测到,在NSP和唾液样本中,Ct值大于30。结果表明,发病后10天症状消退的患者,NSP和唾液样本中的Ct值超过30,不太可能感染他人。
Since the coronavirus disease 2019 (COVID-19) outbreak, laboratory diagnosis has mainly been conducted using reverse-transcription polymerase chain reaction (RT-PCR). Detecting the presence of an infectious virus in the collected sample is essential to analyze if a person can transmit infectious severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, there have been no quantitative investigations conducted for infectious SARS-CoV-2 in clinical samples. Therefore, in the present study, a rapid and simple focus-forming assay using the peroxidase-antiperoxidase technique was developed to quantify infectious SARS-CoV-2 titers in 119 samples (n = 52, nasopharyngeal swabs [NPS]; n = 67, saliva) from patients with COVID-19. Furthermore, the study findings were compared with the cycle threshold (Ct) values of real-time RT-PCR. The infectious virus titers in NPS samples and Ct values were inversely correlated, and no infectious virus could be detected when the Ct value exceeded 30. In contrast, a low correlation was observed between the infectious virus titers in saliva and Ct values (r = -0.261, p = 0.027). Furthermore, the infectious virus titers in the saliva were significantly lower than those in the NPS samples. Ten days after the onset of COVID-19 symptoms, the infectious virus was undetectable, and Ct values were more than 30 in NSP and saliva samples. The results indicate that patients whose symptoms subsided 10 days after onset, with Ct values more than 30 in NSP and saliva samples, were less likely to infect others.