Entry of human coronaviruses

Speaker: Krzysztof Pyrć, PhD, DSc, JU professor (Laboratory of Virology, Jagiellonian University)
http://virogenetics.info/

Talk: Entry of human coronaviruses

Time: 25th January 2018, 9:00 am

Venue: Intercollegiate Faculty of Biotechnology, Abrahama 58, hall 042

The virus entry is one of the key points of the infection, and cell/tissue susceptibility to a large extent determines the nature and severity of the disease. Using a variety of techniques we have mapped the route of entry for several coronaviruses, including human coronavirus NL63 and human coronavirus OC43. Available data on coronavirus’ entry originate frequently from studies employing immortalized cell lines or undifferentiated cells. Here, using the most advanced 3D tissue culture system mimicking the epithelium of conductive airways, we systematically mapped entry of viruses into susceptible cell. Considering low specificity of chemical inhibitors targeting different endocytic pathways, we decided to track the fate of a single virus particle in the cell with confocal microscopy. Obtained results were validated with developed 3D image analysis algorithms and subsequent statistical assessment.

Our results show that HCoV-NL63 virions require endocytosis for successful entry, and interaction between the virus and the receptor molecule triggers recruitment of clathrin. Subsequent vesicle scission by dynamin results in virus internalization, and the newly formed vesicle passes the actin cortex, what requires cytoskeleton rearrangement. Finally, acidification of the endosomal microenvironment is required for successful fusion and release of viral genome into the cytoplasm. On the other hand, HCoV‑OC43 employed a very different route, using caveolin-1-dependent pathway to enter the cell. Surprisingly, the virus was also internalized by macropinocytosis, but this route of internalization did not allow for virus entry and subsequent replication. HCoV‑OC43 trafficking in the cell seems to be carried out along actin filaments. We believe that usage of 3D tissue culture models and an appropriate methodology allowed us to obtain reliable, relevant biological results.