Bats are a likely zoonotic reservoir for a range of human pathogens including endemic human coronaviruses and SARS-CoV-2. Despite the high burden caused by these viruses, the factors required for the establishment and ongoing transmission in humans are not well understood, hampering efforts for pandemic preparedness. To help understand those adaptations required to cross the species barrier, we serially passaged endemic human coronavirus 229E isolates in a newly established Rhinolophus (horseshoe bat) kidney cell line. Here we report extensive mutations, including deletions, in the virus genome that result in the loss of spike protein expression, while maintaining the capability to infect bat cells. While we observed a loss of infectivity of human cells for all viruses with spike deletions, one isolate (2613) with an insertion that results in an early stop codon, was recovered from human cells. Deep sequencing of isolate 2613 showed that the majority population had acquired additional nucleotide insertions in the spike resulting in an additional codon that restores spike function. Spike-independent replication of coronaviruses provides an alternative route for infection of host species that dont share common cell-entry receptors.
Spike independent replication of human coronavirus in bat cells