Development of two multiplex real-time PCR assays for simultaneous detection and differentiation of monkeypox virus IIa, IIb, and I clades and the B.1 lineage

An ongoing multi-country outbreak of monkeypox was reported in May 2022 with several deaths, affecting 107 countries of all six World Health Organization (WHO) regions. The WHO has declared the current monkeypox outbreak to be a Public Health Emergency of International Concern. It is, thus, necessary to rapidly and accurately detect and distinguish different monkeypox virus (MPXV) clades. We designed primers and probes based on the alignment of 138 complete genomes of poxviruses. In Panel 1, we mixed one pair of primers and three probes to detect and differentiate the MPXV Western Africa (IIa, IIb clade) and Congo Basin (I clade) and other orthopoxviruses. In Panel 2, we mixed one pair of primers and two probes to detect the 2022 MPXV (B.1 lineage and its descendant lineages). In addition, we tested the specificity and sensitivity of the assay using real-time PCR. In Panel 1, the assay reproducibly identified various concentrations of two plasmids of the monkeypox virus, whereas other orthopoxviruses did not cross-react. In Panel 2, the probe annealed well to MPXV B.1 and showed the expected linearity. These two multiple real-time assays are inclusive and highly specific for identifying different clades of MPXV.