Development of an automated plaque-counting program for the quantification of the Chikungunya virus

Abstract Chikungunya virus (CHIKV) induces a massive cytopathic effect (CPE) on various cell types. Therefore, the plaque assay, a CPE-based virus titration method, remains the gold standard for quantifying the infectious units of CHIKV. However, manual plaque counting is often a labor-intensive tas...

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Main Authors: Akino Emi, Youichi Suzuki, Chinami Odake, Shoichi Sakaguchi, Hong Wu, Takashi Nakano
Format: Article
Language:English
Published: Nature Portfolio 2025-04-01
Series:Scientific Reports
Online Access:https://doi.org/10.1038/s41598-025-97590-3
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author Akino Emi
Youichi Suzuki
Chinami Odake
Shoichi Sakaguchi
Hong Wu
Takashi Nakano
author_facet Akino Emi
Youichi Suzuki
Chinami Odake
Shoichi Sakaguchi
Hong Wu
Takashi Nakano
author_sort Akino Emi
collection DOAJ
description Abstract Chikungunya virus (CHIKV) induces a massive cytopathic effect (CPE) on various cell types. Therefore, the plaque assay, a CPE-based virus titration method, remains the gold standard for quantifying the infectious units of CHIKV. However, manual plaque counting is often a labor-intensive task, especially in experiments involving multiple samples. In this study, we developed plaQuest, a stand-alone plaque-counting software running on a Windows operating system, for rapid and reliable quantification of CHIKV plaques in a 24-well plate. Our evaluation experiments using the conventional CPE-based plaque assay showed that the CHIKV plaque counts provided by plaQuest strongly correlated with the plaque counts manually determined by four analysts. In addition, the CHIKV inhibition curve of mycophenolic acid (MPA) determined by plaQuest was identical to that determined by manual counting, resulting in a similar 50% inhibitory concentration of MPA. Furthermore, the automated plaque counting by plaQuest was applicable to the evaluation of inhibitors against other RNA viruses using the CPE-based and immunostain-based plaque assay, which is an alternative titration assay for non- (or less) cytopathic viruses. Thus, our study demonstrates that plaQuest is an effective option for quantifying infectious virus titers, reducing the workload of the plaque assay.
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spelling doaj-art-93b3de464e644fc88c9d5e391dddab632025-08-20T02:17:01ZengNature PortfolioScientific Reports2045-23222025-04-0115111210.1038/s41598-025-97590-3Development of an automated plaque-counting program for the quantification of the Chikungunya virusAkino Emi0Youichi Suzuki1Chinami Odake2Shoichi Sakaguchi3Hong Wu4Takashi Nakano5Department of Microbiology and Infection Control, Faculty of Medicine, Osaka Medical and Pharmaceutical UniversityDepartment of Microbiology and Infection Control, Faculty of Medicine, Osaka Medical and Pharmaceutical UniversityDepartment of Microbiology and Infection Control, Faculty of Medicine, Osaka Medical and Pharmaceutical UniversityDepartment of Microbiology and Infection Control, Faculty of Medicine, Osaka Medical and Pharmaceutical UniversityDepartment of Microbiology and Infection Control, Faculty of Medicine, Osaka Medical and Pharmaceutical UniversityDepartment of Microbiology and Infection Control, Faculty of Medicine, Osaka Medical and Pharmaceutical UniversityAbstract Chikungunya virus (CHIKV) induces a massive cytopathic effect (CPE) on various cell types. Therefore, the plaque assay, a CPE-based virus titration method, remains the gold standard for quantifying the infectious units of CHIKV. However, manual plaque counting is often a labor-intensive task, especially in experiments involving multiple samples. In this study, we developed plaQuest, a stand-alone plaque-counting software running on a Windows operating system, for rapid and reliable quantification of CHIKV plaques in a 24-well plate. Our evaluation experiments using the conventional CPE-based plaque assay showed that the CHIKV plaque counts provided by plaQuest strongly correlated with the plaque counts manually determined by four analysts. In addition, the CHIKV inhibition curve of mycophenolic acid (MPA) determined by plaQuest was identical to that determined by manual counting, resulting in a similar 50% inhibitory concentration of MPA. Furthermore, the automated plaque counting by plaQuest was applicable to the evaluation of inhibitors against other RNA viruses using the CPE-based and immunostain-based plaque assay, which is an alternative titration assay for non- (or less) cytopathic viruses. Thus, our study demonstrates that plaQuest is an effective option for quantifying infectious virus titers, reducing the workload of the plaque assay.https://doi.org/10.1038/s41598-025-97590-3
spellingShingle Akino Emi
Youichi Suzuki
Chinami Odake
Shoichi Sakaguchi
Hong Wu
Takashi Nakano
Development of an automated plaque-counting program for the quantification of the Chikungunya virus
Scientific Reports
title Development of an automated plaque-counting program for the quantification of the Chikungunya virus
title_full Development of an automated plaque-counting program for the quantification of the Chikungunya virus
title_fullStr Development of an automated plaque-counting program for the quantification of the Chikungunya virus
title_full_unstemmed Development of an automated plaque-counting program for the quantification of the Chikungunya virus
title_short Development of an automated plaque-counting program for the quantification of the Chikungunya virus
title_sort development of an automated plaque counting program for the quantification of the chikungunya virus
url https://doi.org/10.1038/s41598-025-97590-3
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