The assessment on cross immunity with smallpox virus and antiviral drug sensitivity of the isolated mpox virus strain WIBP-MPXV-001 in China

ABSTRACT

Since May 2022, human mpox cases have increased unexpectedly in non-endemic countries. The first imported case of human mpox in Hong Kong was reported in September 2022. Here we report the isolation and identification of MPXV from the vesicle swabs of this patient. In this research, the vesicle swabs were inoculated in Vero and Vero E6 cells. In addition to observing cytopathic effects (CPEs) in Vero or Vero E6 cells, the isolated virus was identified as mpox virus (MPXV) using quantitative Real-Time PCR (RT–PCR), transmission electron microscopy, and high-throughput sequencing. The experiment also assessed the cross-protective efficacy of sera from the smallpox vaccinated population and preliminarily assessed the inhibitory effect of anti-smallpox virus drugs against MPXV. CPEs can be observed on Vero E6 cells at 24 h and Vero cells at 48 h. The virus particles could be observed by transmission electron microscope, showing typical orthopoxvirus morphology. In addition, F3L and ATI genes which from MPXV A39R, B2R, HA genes which from orthopoxvirus were confirmed by conventional PCR and Sanger sequencing. The next generation sequencing (NGS) suggests that the MPXV strain belongs to B.1 branch of the West African linage, and has a high identity with the sequence of the 2022 ongoing outbreak. PRNT₅₀ results showed that 26.7% of sera from individuals born before 1981 who had been immunized with smallpox were positive, but no MPXV-neutralizing antibodies were found in sera from individuals born later. All four anti-smallpox virus drugs evaluated demonstrated inhibition of mpox virus.

GRAPHICAL ABSTRACT

KEYWORDS:

• Isolation
• identification
• Mpox virus
• phylogenetic
• neutralizing antibodies

Acknowledgements

The authors thank Public Health Laboratory Services Branch, in Hong Kong, China for providing the vesicle swabs of a mpox-infectious case and P. Zhang from the WIV core facility centre for their help with producing transmission electron microscopy micrographs.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Ethics declarations

All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2008. Informed consent was obtained from all patients for being included in the study.

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

This work was supported by the National Key Research and Development Program of China [2021YFC2600200].