Discrepancies in Infectivity of Flavivirus and SARS-CoV-2 Clinical Samples: An Improved Assay for Infectious Virus Shedding and Viremia Assessment

Mizuki Fukuta, Co Thach Nguyen, Thi Thu Thuy Nguyen, Thi Thanh Ngan Nguyen, Thi Bich Hau Vu, Taichiro Takemura, Le Khanh Hang Nguyen, Shingo Inoue, Kouichi Morita, Thi Quynh Mai Le, Futoshi Hasebe and Meng Ling Moi
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Mizuki Fukuta: Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki 852-8523, Japan
Co Thach Nguyen: National Institute of Hygiene and Epidemiology, Hanoi 10000, Vietnam
Thi Thu Thuy Nguyen: National Institute of Hygiene and Epidemiology, Hanoi 10000, Vietnam
Thi Thanh Ngan Nguyen: Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki 852-8523, Japan
Thi Bich Hau Vu: National Institute of Hygiene and Epidemiology, Hanoi 10000, Vietnam
Taichiro Takemura: Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki 852-8523, Japan
Le Khanh Hang Nguyen: National Institute of Hygiene and Epidemiology, Hanoi 10000, Vietnam
Shingo Inoue: Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki 852-8523, Japan
Kouichi Morita: Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki 852-8523, Japan
Thi Quynh Mai Le: National Institute of Hygiene and Epidemiology, Hanoi 10000, Vietnam
Futoshi Hasebe: Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki 852-8523, Japan
Meng Ling Moi: Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki 852-8523, Japan

IJERPH, 2021, vol. 18, issue 18, 1-11

Abstract: Infectivity and neutralizing antibody titers of flavivirus and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are frequently measured using the conventional plaque assay. While the assay is useful in the determination of infectivity, conventional plaque assays generally possess lower sensitivity and are time-consuming compared to nucleic acid amplification tests. In this study, a microcrystalline cellulose (MCC), Avicel, was evaluated as an alternative to the conventional virus overlay medium, methylcellulose, for a plaque assay. The plaque assay was performed using dengue and COVID-19 clinical samples and laboratory-established flavivirus and SARS-CoV-2 strains. In virus titration of clinical samples, the plaques were significantly larger, and the virus titers were higher when Avicel MCC-containing overlay medium was used than with conventional methylcellulose overlay medium. In addition, for some clinical samples and laboratory virus strains, infectious particles were detected as plaques in the Avicel MCC-containing medium, but not in the conventional methylcellulose medium. The results suggest that the viremia titer determined using the new overlay medium containing Avicel MCC may better reflect the innate infectious and plaque-forming capabilities of clinical samples and better reflect virus infectivity.

Keywords: infectivity assessment; infectious particles; dengue; SARS-CoV-2; culture medium (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2021
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