In 2022-23 the world experienced the largest recorded mpox virus (MPXV) outbreak outside of endemic regions. Remarkably, cases of neurological manifestations were reported, some of which fatal. MPXV DNA and MPXV-specific IgM antibodies were detected in the cerebrospinal fluid of encephalitis-affected patients, suggesting neuroinvasive potential of MPXV. We explored the susceptibility of neural tissue to MPXV infection using human cerebral organoids (hCOs) exposed to a primary isolate belonging to clade IIb lineage. The virus efficiently replicates in hCOs as indicated by the exponential increase of infectious viral loads and the elevated frequency of MPXV-positive cells over time. Also, electron microscopy imaging revealed the presence of viral particles as well as perinuclear viral factories. We observed susceptibility of several cell lineages to the virus, including neural progenitor cells, neurons, and astrocytes. Furthermore, we detected the presence of viral antigens in neurites and in foci of grouped cells distributed throughout the tissue. In line with this, examining released and cell-associated MPXV titers, we observed significantly more cell-associated infectious virus, suggesting viral spread by cell-to-cell contact. While hCOs displayed no evident outer morphological changes upon infection, we detected the formation of varicosities in neurites, pointing to viral manipulation of axonal transport and neuronal injury. In accordance, the apoptosis marker cleaved caspase-3 was detected within neurite swellings. Our findings identify a mechanism potentially contributing to MPXV-mediated neuropathology that may have therapeutic implications.

Mpox virus spreads from cell-to-cell and leads to neuronal injury in human cerebral organoids