Infectivity assay for detection of SARS‐CoV‐2 in samples from patients with COVID‐19

Abstract

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.

Stability of SARS-CoV-2 and influenza virus varies across different paper types

“…Viral titer in the upper respiratory tract-derived body fluid of patients infected with IAV and SARS-CoV-2 ranged from 1.0 × ×10 2 to 2.0 × ×10 6 FFUs/mL or TCID 50 /mL [ [16] , [17] , [18] , [19] ]. When 10–100 μL of the infectious body fluid is deposited on a paper surface, the maximum absolute viral titer on the paper surface is approximately 2.0 × ×10 5 FFUs or TCID 50 .…”

Clinical Experience with Ropeginterferon Alfa-2b in the Off-Label Use for the Treatment of COVID-19 Patients in Taiwan

“…A negative correlation between age and the antiviral activity of IFN-based therapies was observed in previous studies. Honda et al evaluated the efficacy of combination therapy with peginterferon-alfa-2b and ribavirin in patients with chronic HCV infection [ 23 ]. The study showed that sustained viral response (SVR) rate was lower in elderly patients (≥ 65 years) than in younger patients (< 65 years).…”

“…The primary outcome was to compare the median time from the date of the last SARS-CoV-2 RT-PCR positive examination to the date of the first RT-PCR negative conversion and patient overall RT-PCR negative conversion time between the ropeginterferon alfa-2b and SOC alone groups. SARS-CoV-2 RT-PCR negative conversion was defined as the first detection of C t value ≥ 30 after treatments [ 21 – 23 ]. Safety was evaluated by the occurrences of AEs and SAEs after receiving the single dose of ropeginterferon alfa-2b.…”

Antibody-Dependent Enhancement of IL-6 Production by SARS-CoV-2 Nucleocapsid Protein

“…SARS-CoV-2 (JPN-TY-WK-521) was obtained from the National Institute for Infectious Diseases, Japan. Clinical isolates hCoV-19/Japan/OIPH14/2020 and hCoV-19/Japan/OIPH21/2020 57 were propagated in TMPRSS2/VeroE6 cells 58 that were obtained from the National Institutes of Biomedical Innovation, Health and Nutrition, Japanese Collection of Research Bioresources Cell Bank, Japan. K-ML2 cells were established as described previously 59 and maintained in minimum essential medium supplemented with 10% fetal calf serum.…”