SARS-CoV-2 strain-specific anti-spike IgG ELISA utilizing spike protein produced by silkworms

Article type: Brief Report

Authors: Goto, Takeyuki^{a; *} | Sasaki, Tomoki^{b; c} | Chong, Yong^a | Taniguchi, Masahiro^b | Lee, Jae Man^d | Masuda, Akitsu^d | Ebihara, Takeru^c | Shiraishi, Kenichiro^a | Tani, Naoki^a | Yonekawa, Akiko^a | Gondo, Kei^e | Kuwano, Hiroyuki^e | Shimono, Nobuyuki^f | Ikematsu, Hideyuki^g | Akashi, Koichi^a | Kusakabe, Takahiro^c

Affiliations: [a] Medicine and Biosystemic Science, Kyushu University Graduate School of Medical Sciences (The First Department of Internal Medicine), Fukuoka, Japan | [b] R&D Department, KAICO Ltd, Fukuoka, Japan | [c] Laboratory of Insect Genome Science, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Fukuoka, Japan | [d] Laboratory of Creative Science for Insect Industries Laboratory of Insect Genome Science, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Fukuoka, Japan | [e] COVID-19 Team, Fukuoka City Hospital, Fukuoka, Japan | [f] Center for the Study of Global Infection, Kyushu University Hospital, Fukuoka, Japan | [g] Ricerca Clinica Co., Fukuoka, Japan

Correspondence: [*] Corresponding author: Takeyuki Goto, Medicine and Biosystemic Science, Kyushu University Graduate School of Medical Sciences, 3-1-1 Maidashi, Higashi-Ku, Fukuoka 812-8582, Japan. Tel.: +81 92 642 5228; Fax: +81 92 642 5247; E-mail: goto.takeyuki.759@s.kyushu-u.ac.jp.

Abstract: BACKGROUND: A cost-effective and eco-friendly method is needed for the assessment of humoral immunity against SARS-CoV-2 in large populations. OBJECTIVE: We investigated the performance of an ELISA that uses silkworm-produced proteins to quantify the strain-specific anti-Spike IgG (anti-S IgG) titer. METHODS: The OD values for the anti-His-tag antibody, a standard material of ELISA quantification, were measured. Correlations between the ELISA for each strain and the Abbott SARS-CoV-2 IgG II Quant assay for the wild type were evaluated with serum samples from nine participants with various infection and vaccination statuses. RESULTS: Linear dose-responses were confirmed by high coefficients of determination: 0.994, 0.994, and 0.996 for the wild-type, Delta, and Omicron (BA.1) strain assays, respectively. The coefficient of determination for the wild-type and Delta strain assays was high at 0.959 and 0.892, respectively, while the Omicron strain assay had a relatively low value of 0.563. Booster vaccinees showed similar or higher titers against all strains compared to infected persons without vaccination. The Omicron-infected persons without vaccination had lower antibody titers against wild type than did the vaccinated persons. CONCLUSIONS: This study provides data indicating that the ELISA with silkworm-produced proteins makes it possible to discriminate and quantify the strain-specific anti-S IgG antibody induced by vaccination or infection.

Keywords: SARS-CoV-2, antibody, ELISA, silkworm, omicron

DOI: 10.3233/HAB-230006

Journal: Human Antibodies, vol. 31, no. 3, pp. 27-33, 2023