Rapid Generation of In-House Serological Assays Is Comparable to Commercial Kits Critical for Early Response to Pandemics: A Case With SARS-CoV-2

Heidi Auerswald; Chanreaksmey Eng; Sokchea Lay; Saraden In; Sokchea Eng; Hoa Thi My Vo; Charya Sith; Sokleaph Cheng; Gauthier Delvallez; Vann Mich; Ngy Meng; Ly Sovann; Kraing Sidonn; Jessica Vanhomwegen; Tineke Cantaert; Philippe Dussart; Veasna Duong; Erik A Karlsson

doi:10.3389/fmed.2022.864972

Rapid Generation of In-House Serological Assays Is Comparable to Commercial Kits Critical for Early Response to Pandemics: A Case With SARS-CoV-2

Front Med (Lausanne). 2022 May 6:9:864972. doi: 10.3389/fmed.2022.864972. eCollection 2022.

Authors

Heidi Auerswald¹, Chanreaksmey Eng¹, Sokchea Lay², Saraden In¹, Sokchea Eng³, Hoa Thi My Vo², Charya Sith³, Sokleaph Cheng³, Gauthier Delvallez³, Vann Mich⁴, Ngy Meng⁴, Ly Sovann⁵, Kraing Sidonn⁵, Jessica Vanhomwegen⁶, Tineke Cantaert², Philippe Dussart⁷, Veasna Duong¹, Erik A Karlsson¹

Affiliations

¹ Virology Unit, Institut Pasteur du Cambodge, Pasteur Network, Phnom Penh, Cambodia.
² Immunology Unit, Institut Pasteur du Cambodge, Pasteur Network, Phnom Penh, Cambodia.
³ Medical Biology Laboratory, Institut Pasteur du Cambodge, Pasteur Network, Phnom Penh, Cambodia.
⁴ Khmer-Soviet Friendship Hospital, Ministry of Health, Phnom Penh, Cambodia.
⁵ Communicable Disease Control Department, Ministry of Health, Phnom Penh, Cambodia.
⁶ Environment and Infectious Risks Unit, Institut Pasteur, Paris, France.
⁷ Institut Pasteur de Madagascar, Pasteur Network, Antananarivo, Madagascar.

Abstract

Introduction: Accurate and sensitive measurement of antibodies is critical to assess the prevalence of infection, especially asymptomatic infection, and to analyze the immune response to vaccination during outbreaks and pandemics. A broad variety of commercial and in-house serological assays are available to cater to different laboratory requirements; however direct comparison is necessary to understand utility.

Materials and methods: We investigate the performance of six serological methods against SARS-CoV-2 to determine the antibody profile of 250 serum samples, including 234 RT-PCR-confirmed SARS-CoV-2 cases, the majority with asymptomatic presentation (87.2%) at 1-51 days post laboratory diagnosis. First, we compare to the performance of two in-house antibody assays: (i) an in-house IgG ELISA, utilizing UV-inactivated virus, and (ii) a live-virus neutralization assay (PRNT) using the same Cambodian isolate as the ELISA. In-house assays are then compared to standardized commercial anti-SARS-CoV-2 electrochemiluminescence immunoassays (Elecsys ECLIAs, Roche Diagnostics; targeting anti-N and anti-S antibodies) along with a flow cytometry based assay (FACS) that measures IgM and IgG against spike (S) protein and a multiplex microsphere-based immunoassay (MIA) determining the antibodies against various spike and nucleoprotein (N) antigens of SARS-CoV-2 and other coronaviruses (SARS-CoV-1, MERS-CoV, hCoVs 229E, NL63, HKU1).

Results: Overall, specificity of assays was 100%, except for the anti-S IgM flow cytometry based assay (96.2%), and the in-house IgG ELISA (94.2%). Sensitivity ranged from 97.3% for the anti-S ECLIA down to 76.3% for the anti-S IgG flow cytometry based assay. PRNT and in-house IgG ELISA performed similarly well when compared to the commercial ECLIA: sensitivity of ELISA and PRNT was 94.7 and 91.1%, respectively, compared to S- and N-targeting ECLIA with 97.3 and 96.8%, respectively. The MIA revealed cross-reactivity of antibodies from SARS-CoV-2-infected patients to the nucleocapsid of SARS-CoV-1, and the spike S1 domain of HKU1.

Conclusion: In-house serological assays, especially ELISA and PRNT, perform similarly to commercial assays, a critical factor in pandemic response. Selection of suitable immunoassays should be made based on available resources and diagnostic needs.

Keywords: ELISA; PRNT; SARS-CoV-2; immunoassay; serology.