Ultrastructural analysis of monkeypox virus replication in Vero cells

Abstract

In early May 2022, the first worldwide monkeypox virus (MPXV) outbreak was reported, with different clinical aspects from previously studied human monkeypox infections. Despite monkeypox medical importance, much of its biological aspects remain to be further investigated. In the present work, we evaluated ultrastructural aspects of MPXV asynchronous infections in Vero cells by transmission electron microscopy (TEM). The viral strain was isolated from a male patient infected during the 2022 outbreak. TEM analysis showed: (i) adhered intracellular mature virus particles before entry of the host cell; (ii) a reorganization of the rough endoplasmic reticulum cisternae into the so-called "mini-nuclei" structure associated with genome replication; and (iii) noticeably different sites within the viral factory presenting granular or fibrillar aspects. We also observed viral crescents, different MPXV particle morphotypes, and cellular alterations induced by infection, such as changes in the cytoskeleton structure and multimembrane vesicles abundance. Taken together, to the best of our knowledge, these results revealed for the first-time ultrastructural aspects of different steps of the MPXV cycle.

Genomic and ultrastructural analysis of monkeypox virus in skin lesions and in human/animal infected cells reveals further morphofunctional insights into viral pathogenicity

“…EM of skin biopsies showed irregularly arranged, pleomorphic intracellular MV particles (Figure 2C–D). Classically, MPXV morphology consists of four components: the core, lateral bodies, outer viral membrane, and lipoprotein membrane 19,20,23 . The dumbbell‐shaped core is made up of tightly packed rod‐shaped structures with dimensions of 10 nm in length and 5 nm in diameter, and an inner smooth layer 5 nm thick.…”

“…Regarding to the ultrastructural changes due to MPXV replication cycle, Witt et al performed a comprehensive study detailing a structural landscape in Vero-infected cells. 23 Our aim was to validate their results at the tissue level for human clinical infections by comparing findings for paraffin-embedded cutaneous tissue biopsies from actual patients infected with MPXV to those from MPVXinfected cell cultures. Overall, there were similar findings in the clinical samples examined as were described during in vitro MPVX infection.…”

“…Ultrastructural studies have revealed important insights into the morphology and replication cycle of MPXV in both humans and a variety of animal hosts 19–22 . More recently, an elegant study by Witt et al has broadened our understanding of the ultrastructural aspects of MPXV by examining, for the first time, the diverse aspects of its replication cycle in Vero cells infected with a current circulating strain from the 2022–2023 MPOX outbreak 23 …”

Sequencing of monkeypox virus from infected patients reveals viral genomes with APOBEC3‐like editing, gene inactivation, and bacterial agents of skin superinfection

“…AY603355) 31 . It is worthy to note that unlike many other DNA viruses, poxviruses replicate in the host cell cytoplasm within viral factories 55,56 …”

“…31 It is worthy to note that unlike many other DNA viruses, poxviruses replicate in the host cell cytoplasm within viral factories. 55,56 Anyway, gene loss is a known trait of poxvirus evolution, and it was notably suspected to be associated with a restricted host range but also with an efficient human-to-human spread in orthopoxviruses. 1,33,[57][58][59] For instance, it was observed in MPXV genomes recovered from 10 of 60 specimens collected from humans between 2005 and 2007 in the Democratic Republic of the Congo.…”