Hashiguchi, T. | bioRxiv Science

bioRxiv2021

Zoonotic potential of a novel bat morbillivirus

Morbilliviruses are amongst the most contagious viral pathogens that infect mammals. Metagenomic surveys have identified numerous morbillivirus sequences in bats, but no full-length authentic morbillivirus has been isolated or characterized from bats. Here we detail the discovery of full-length Myotis Bat Morbillivirus (MBaMV) from a bat surveillance program in Brazil. After determining that MBaMV utilizes bat CD150 but not human CD150 as an entry receptor, we generated an infectious clone of MBaMV using reverse genetics. MBaMV exhibited features consistent with other morbilliviruses, including pleomorphic virions, P-editing and the rule-of-six. MBaMV replicated well in human epithelial cell lines in a nectin-4 dependent manner. Surprisingly, MBaMV was able to infect human macrophages in a CD150-independent manner. However, MBaMV was restricted by cross-neutralizing human sera and did not evade the human innate immune system, indicating that while zoonotic spillover into humans may be possible, MBaMV replication in humans would likely be restricted.

microbiology↗

bioRxiv2020

Fitness selection of hyperfusogenic measles virus F proteins associated with neuropathogenic phenotypes

Measles virus (MeV) is resurgent and caused >200,000 deaths in 2019. MeV infection can establish a chronic latent infection of the brain that can recrudesce months to years after recovery from the primary infection. Recrudescent MeV leads to fatal subacute sclerosing panencephalitis (SSPE) or measles inclusion body encephalitis (MIBE) as the virus spreads across multiple brain regions. Most clinical isolates of SSPE/MIBE strains show mutations in the fusion (F) gene that result in a hyperfusogenic phenotype in vitro and allow for efficient spread in primary human neurons. Wild-type MeV receptor binding protein (RBP) is indispensable for manifesting these mutant F phenotypes, even though neurons lack canonical MeV receptors (CD150/SLAMF1 or Nectin-4). How such hyperfusogenic F mutants are selected for, and whether they confer a fitness advantage for efficient neuronal spread is unresolved. To better understand the fitness landscape that allows for the selection of such hyperfusogenic F mutants, we conducted a screen of [≥]3.1x105 MeV-F point mutants in their genomic context. We rescued and amplified our genomic MeV-F mutant libraries in BSR-T7 cells under conditions where MeV-F-T461I (a known SSPE mutant), but not wild-type MeV can spread. We recovered known SSPE mutants but also characterized at least 15 novel hyperfusogenic F mutations with a SSPE phenotype. Structural mapping of these mutants onto the pre-fusion MeV-F trimer confirm and extend our understanding of the fusion regulatory domains in MeV-F. Our list of hyperfusogenic F mutants is a valuable resource for future studies into MeV neuropathogenesis and the regulation of paramyxovirus fusion. SignificanceMeasles remains a major cause of infant death globally. On rare occasions, measles virus infection of the central nervous system (CNS) leads to a fatal progressive inflammation of the brain many years after the initial infection. MeV isolates from such CNS infections harbor fusion (F) protein mutations that result in a hyperfusogenic phenotype. The small number of hyperfusogenic MeV-F mutants identified thus far limits our ability to understand how these mutations are selected in the context of CNS infections. We performed a saturating mutagenesis screen of MeV-F to identify a large set of mutants that would mimic the hyperfusogenic phenotype of MeV-F in CNS infection. Characterization of these mutants shed light on other paramyxoviruses known to establish chronic CNS infections.

microbiology↗

bioRxiv2020

Genetically engineered retina for improved retinal reconstruction after transplantation

ES/iPS-retinal sheet transplantation, which supplies photoreceptors as well as other retinal cells, has been shown able to restore visual function in mice with end-stage retinal degeneration. Here, by introducing a novel type of genetically engineered ES/iPS-retinal sheet with reduced numbers of secondary retinal neurons but intact photoreceptor cell layer structure, we reinforced the evidence that ES/iPS-retinal sheet transplantation can establish synaptic connections with the host, restore light responsiveness and reduce aberrant RGC spiking. Furthermore, we show that genetically engineered grafts can substantially improve the outcome of the treatment by improving neural integration. We speculate that this leads to reduced spontaneous activity in the host which in turn contributes to a better visual recovery.

neuroscience↗