Productive infection of cerebellar granule cell neurons by JC virus in an HIV+ individual.

BACKGROUND: In the setting of severe immunosuppression, the polyomavirus JC (JCV) can cause a lytic infection of oligodendrocytes. This demyelinating disease of the CNS white matter (WM) is called progressive multifocal leukoencephalopathy (PML). JCV has a very narrow host-cell range and productive infection of neurons has never been demonstrated. Patient, methods, and results: An HIV-1-infected patient presented with signs of pyramidal tract and cerebellar dysfunction. Brain MRI revealed T2 hyperintensities in the WM of both frontal lobes and cerebellar atrophy. His disease progressed despite therapy and he died 6 months later. In addition to classic PML findings in the frontal lobe WM, autopsy revealed scattered foci of tissue destruction in the internal granule cell layer (IGCL) of the cerebellum. In these foci, enlarged granule cell neurons identified by the neuronal markers MAP-2 and NeuN reacted with antibodies specific for the polyomavirus VP1 capsid protein. Electron microscopy showed 40 nm viral particles, consistent with polyomaviruses, in these granule cell neurons. In addition, JCV DNA was detected by PCR after laser capture microdissection of cells from the areas of focal cell loss. Finally, in situ hybridization studies demonstrated that many granule cell neurons were infected with JCV but did not contain viral proteins. Sequence analysis of the JCV regulatory region from cerebellar virions showed a tandem repeat pattern also found in PML lesions of the frontal lobe WM. CONCLUSION: JCV can productively infect granule cell neurons of the IGCL of the cerebellum. This suggests a role for JCV infection of neurons in cerebellar atrophy occurring in HIV-infected individuals

Search for intermediate-mass black hole binaries in the third observing run of Advanced LIGO and Advanced Virgo

International audienceIntermediate-mass black holes (IMBHs) span the approximate mass range 100−105 M⊙, between black holes (BHs) that formed by stellar collapse and the supermassive BHs at the centers of galaxies. Mergers of IMBH binaries are the most energetic gravitational-wave sources accessible by the terrestrial detector network. Searches of the first two observing runs of Advanced LIGO and Advanced Virgo did not yield any significant IMBH binary signals. In the third observing run (O3), the increased network sensitivity enabled the detection of GW190521, a signal consistent with a binary merger of mass ∼150 M⊙ providing direct evidence of IMBH formation. Here, we report on a dedicated search of O3 data for further IMBH binary mergers, combining both modeled (matched filter) and model-independent search methods. We find some marginal candidates, but none are sufficiently significant to indicate detection of further IMBH mergers. We quantify the sensitivity of the individual search methods and of the combined search using a suite of IMBH binary signals obtained via numerical relativity, including the effects of spins misaligned with the binary orbital axis, and present the resulting upper limits on astrophysical merger rates. Our most stringent limit is for equal mass and aligned spin BH binary of total mass 200 M⊙ and effective aligned spin 0.8 at 0.056 Gpc−3 yr−1 (90% confidence), a factor of 3.5 more constraining than previous LIGO-Virgo limits. We also update the estimated rate of mergers similar to GW190521 to 0.08 Gpc−3 yr−1.Key words: gravitational waves / stars: black holes / black hole physicsCorresponding author: W. Del Pozzo, e-mail: [email protected]† Deceased, August 2020