Determination of seroprevalence and kinetics of humoral response using mpox virus A29 protein

Jian-Piao Cai; Wing-Ming Chu; Anthony Raymond Tam; Kun Wang; Yuting Han; Lin-Lei Chen; Xiaojuan Zhang; Charlotte Yee-Ki Choi; Vincent Chi-Chung Cheng; Kwok-Hung Chan; Zhiwei Chen; Ivan Fan-Ngai Hung; Carol Ho-Yan Fong; Kelvin Kai-Wang To

doi:10.1038/s43856-023-00403-9

Determination of seroprevalence and kinetics of humoral response using mpox virus A29 protein

Commun Med (Lond). 2023 Nov 22;3(1):168. doi: 10.1038/s43856-023-00403-9.

Authors

Jian-Piao Cai¹, Wing-Ming Chu², Anthony Raymond Tam², Kun Wang¹, Yuting Han¹, Lin-Lei Chen¹, Xiaojuan Zhang¹, Charlotte Yee-Ki Choi¹, Vincent Chi-Chung Cheng^{1

3}, Kwok-Hung Chan^{1

4}, Zhiwei Chen^{1

4

5}, Ivan Fan-Ngai Hung^{2

6

7}, Carol Ho-Yan Fong^{8

9}, Kelvin Kai-Wang To^{10

11

12

13}

Affiliations

¹ State Key Laboratory for Emerging Infectious Diseases, Carol Yu Centre for Infection, Department of Microbiology, School of Clinical Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China.
² Infectious Diseases Division, Department of Medicine, Queen Mary Hospital, Pokfulam, Hong Kong Special Administrative Region, China.
³ Department of Microbiology, Queen Mary Hospital, Pokfulam, Hong Kong Special Administrative Region, China.
⁴ Centre for Virology, Vaccinology and Therapeutics, Hong Kong Science and Technology Park, Hong Kong Special Administrative Region, China.
⁵ AIDS Institute, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China.
⁶ Department of Medicine, School of Clinical Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China.
⁷ Department of Infectious Disease and Microbiology, The University of Hong Kong-Shenzhen Hospital, Shenzhen, Guangdong, China.
⁸ State Key Laboratory for Emerging Infectious Diseases, Carol Yu Centre for Infection, Department of Microbiology, School of Clinical Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China. chyfong@hku.hk.
⁹ Centre for Virology, Vaccinology and Therapeutics, Hong Kong Science and Technology Park, Hong Kong Special Administrative Region, China. chyfong@hku.hk.
¹⁰ State Key Laboratory for Emerging Infectious Diseases, Carol Yu Centre for Infection, Department of Microbiology, School of Clinical Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China. kelvinto@hku.hk.
¹¹ Department of Microbiology, Queen Mary Hospital, Pokfulam, Hong Kong Special Administrative Region, China. kelvinto@hku.hk.
¹² Centre for Virology, Vaccinology and Therapeutics, Hong Kong Science and Technology Park, Hong Kong Special Administrative Region, China. kelvinto@hku.hk.
¹³ Department of Infectious Disease and Microbiology, The University of Hong Kong-Shenzhen Hospital, Shenzhen, Guangdong, China. kelvinto@hku.hk.

Abstract

Background: Mpox virus (MPXV), previously known as monkeypox virus, has spread globally in 2022. An accurate and convenient antibody test is essential for the determination of seroprevalence and for studying immune response after natural infection or vaccination. Most seroprevalence or vaccine studies used either live MPXV (or vaccinia virus [VACV]) or inactivated MPXV (or VACV) culture lysate for serological assays, but MPXV culture can only be performed in biosafety level 3 (BSL-3) facilities. Here, we developed and evaluated an enzyme immunoassay (EIA) based on the MPXV A29 surface envelope protein.

Methods: We compared the specificity of the MPXV A29, VACV A27, and VACV lysate EIA using serum specimens collected prior to the global spread of MPXV. Next, we performed these EIAs for serum specimens collected from two mpox patients and an MVA-BN vaccine recipient. We also assessed the kinetics of plasmblast and MPXV A29-specific B-cell response.

Results: Using sera collected from different age groups in Hong Kong, we found that most individuals, including those born before 1981 who have received the smallpox vaccine, tested negative using the MPXV A29 protein. MPXV A29-specific antibody could be detected in the serum of mpox patients and an MVA-BN recipient. In a mpox patient, the frequency of plasmablast and MPXV A29-specific B cell peaked on day 8 post-symptom onset and gradually decreased. Finally, we demonstrated that antibodies against the A29 protein can be used for immunofluorescence staining of MPXV-infected cells.

Conclusions: MPXV A29 protein is suitable for studying the immune response against MPXV infection.

Plain language summary

Since early 2022, mpox (monkeypox) has been reported in many countries where the disease is not regularly found to occur. The aim of the study was to develop and evaluate the performance of laboratory assays based on the mpox virus surface protein, named A29. We found our assays could accurately distinguish naturally infected cases from smallpox vaccine recipients as well as those who were neither infected nor vaccinated. Our assays provide a useful tool for studying the host immune response to mpox virus.