Experimental Infection of Brazilian Free-Tailed Bats (Tadarida brasiliensis) with Two Strains of SARS-CoV-2.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is presumed to have originated from wildlife and shares homology with other bat coronaviruses. Determining the susceptibility of North American bat species to SARS-CoV-2 is of utmost importance for making decisions regarding wildlife management, public health, and conservation. In this study, Brazilian free-tailed bats (Tadarida brasiliensis) were experimentally infected with two strains of SARS-CoV-2 (parental WA01 and Delta variant), evaluated for clinical disease, sampled for viral shedding and antibody production, and analyzed for pathology. None of the bats (n = 18) developed clinical disease associated with infection, shed infectious virus, or developed histopathological lesions associated with SARS-CoV-2 infection. All bats had low levels of viral RNA in oral swabs, six bats had low levels of viral RNA present in the lungs during acute infection, and one of the four bats that were maintained until 28 days post-infection developed a neutralizing antibody response. These findings suggest that Brazilian free-tailed bats are permissive to infection by SARS-CoV-2, but they are unlikely to contribute to environmental maintenance or transmission.

Species-specific molecular barriers to SARS-CoV-2 replication in bat cells

Bats are natural reservoirs for numerous coronaviruses, including the potential ancestor of SARS-CoV-2. Knowledge concerning the interaction of coronaviruses and bat cells is, however, sparse. There is thus a need to develop bat cellular models to understand cell tropism, viral replication and virus-induced cell responses. Here, we report the first molecular study of SARS-CoV-2 infection in chiropteran cells. We investigated the ability of primary cells from Rhinolophus and Myotis species, as well as of established and novel cell lines from Myotis myotis, Eptesicus serotinus, Tadarida brasiliensis and Nyctalus noctula, to support SARS-CoV-2 replication. None of these cells were permissive to infection, not even the ones expressing detectable levels of angiotensin-converting enzyme 2 (ACE2), which serves as the viral receptor in many mammalian species including humans. The resistance to infection was overcome by expression of human ACE2 (hACE2) in three cell lines, suggesting that the restriction to viral replication was due to a low expression of bat ACE2 (bACE2) or absence of bACE2 binding in these cells. By contrast, multiple restriction factors to viral replication exist in the three N. noctula cells since hACE2 expression was not sufficient to permit infection. Infectious virions were produced but not released from hACE2-transduced M. myotis brain cells. E. serotinus brain cells and M. myotis nasal epithelial cells expressing hACE2 efficiently controlled viral replication, which correlated with a potent interferon response. Together, our data highlight the existence of species-specific molecular barriers to viral replication in bat cells. Our newly developed chiropteran cellular models are useful tools to investigate the interplay between viruses belonging to the SARS-CoV- 2 lineage and their natural reservoir, including the identification of factors responsible for viral restriction.