@VirusesImmunity latest neuro story is up on biorxiv! biorxiv.org/content/10.110…
We used brain organoids, K18-hACE2 mice and our recently described AAV-hACE2 mice to show the neuroinvasive potential of SARS-CoV-2. A huge collaborative effort, so we have a lot to share. Here we go...
We used brain organoids, K18-hACE2 mice and our recently described AAV-hACE2 mice to show the neuroinvasive potential of SARS-CoV-2. A huge collaborative effort, so we have a lot to share. Here we go...
We started off by infecting some human brain organoids that my classmate Ce Zhang has been growing for the past few years. Check out these beautiful images that he took (more to come). We saw increasing amounts of cells infected over time. 
Our collaborator Tamas, Yuki and Klara took some beautiful EM images for us to confirm the infection, along with viral particles budding off of the ER structures.
There are two biorxiv papers already describing human brain organoid infections, and they described cells dying so we decided to also check. We saw a similar phenomenon, a lot of cell death! But to our surprise, the cells that were infected were not the ones that were dying
To figure out what the heck was going on, we used single cell sequencing to start parsing out different transcriptional profiles of the infected organoids. Unlike Zika virus, which is known to cause significant interferon responses, we saw a completely unique programming.
When we took a closer look at infected (red) versus neighboring cells (blue) we saw transcriptional profiles related to hyperoxia and increased metabolic activities and hypoxic and alternative metabolic pathways enriched respectively.
It seemed that the SARS-CoV-2 infected neurons didn't go through death pathways, but rather was using up more resources to produce high amounts of virus, creating a hypoxic environment for its neighboring cells. We confirmed this with some HIF1a staining
We were wondering how these cells were getting infected, since ACE2 expression in neuronal cells are still up for debate. We show that RNA levels of ACE2 are not the best predictor of infection, and on a protein level, ACE2 was almost expressed everywhere in the neurons!
Blocking ACE2 with an antibody, we saw that SARS-CoV-2 could no longer infect the organoids!
We were lucky enough to obtain CSF from a patient with COVID-19 and also had neurologic symptoms. We detected high levels of SARS-CoV-2 spike antibodies in this CSF, and saw that it could block infection also! (This is my favorite experiment in the paper, check out figure 3C)
We finally examined the neuroinvasiveness of SARS-CoV-2 in two mice models. The K18-hACE2 mice which showed huge neurotropic SARS-CoV-2 infection. And an adaptation of our AAV-hACE2 paper, introducing hACE2 to different compartments, highlighting its lethality in the brain.
Our paper really highlighted the neuroinvasive potential of SARS-CoV-2 in the CNS, and brings up interesting biology behind what might happen if SARS-CoV-2 were to infect neurons. It goes well with a lot of pathology that autopsy studies of patients dying have been showing.
This is just part one of many interesting SARS-CoV-2 neuroimmunology we have for you. Thanks to all the collaborators (you can tell by all the departments that were involved) and of course all the funders and people who allowed this to happen. Happy to hear everyone's thoughts!
Thank you to @ShelFarFar for making this part happen!
And thank you to @aaronmring @FeimeiL and Yile for helping us with the ELISA so urgently.
All the beautiful images were taken by my classmate and co-first author Ce Zhang!
Thank you to @WilenLab for sharing the K18 mice with us for some interesting findings!
