Non-lethal Cell Culture in the Order Chiroptera: Implications for Viral Studies

The recent outbreak and subsequent rapid spread of the deadly severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is currently an urgent global public health issue. Bioinformatic analysis to date has heavily implicated bats as the natural reservoir of the SARS-CoV-2 lineage. However, there exists much evidence to suggest that the novel virus is not transmissible to many bat species via the angiotensin-converting enzyme 2 (ACE2), which is the confirmed functional receptor. Currently, the best way to validate genome predictions such as this is through cellular-based assays. However, this can be difficult if not impossible for many for non-model, wild, and protected species – such is the case with many species of bat. These challenges have resulted in a lack of tools for investigation into cellular function among the bats. This study employed a phylogenomic approach to search for evidence of positive selection on candidate SARS-CoV-2 receptor genes in bats to ascertain if they may play a role in virus binding and cellular entry. Known binding residues of the genes in question were also inspected for substitutions that may confer a conformational change that may affect viral interactions. While in-silico analysis is an essential step in formulating genomic predictions, it is vital to functionally confirm these predictions as closely to their in-vivo state as possible. To address this, this study aimed to optimise the protocol for the establishment of bat primary cell cultures obtained through minimally invasive methods from bat species. Phylogenomic analysis of potential SARS-CoV-2 receptors did not show any significant signals of selection in the ancestral bat lineage, and while inspection of key active residues did show interesting results, functional validation of virus-receptor activity would be required to confirm them. Primary cultures from bat wing biopsies were successfully cultured under optimised novel conditions. The methods developed through this study will serve as powerful tools to bring the wild into the lab, and will allow in-silico predictions regarding the molecular basis of bats’ unique adaptations to be evaluated.