Immortalized sheep microglial cells are permissive to a diverse range of ruminant viruses

Ruminants, including sheep and goats (small ruminants), are key agricultural animals in many parts of the world. Infectious diseases, including many viral diseases, are significant problems to efficient production of ruminants. Unfortunately, reagents tailored to viruses of ruminants, and especially small ruminants, are lacking compared to other animals more typically used for biomedical research.

The purpose of this study was to determine the permissibility of a stably immortalized, sheep microglial cell line to viruses that are reported to infect ruminants: bovine viral diarrhea virus (BVDV), bovine herpesvirus 1 (BoHV-1), small ruminant lentiviruses (SRLV), and bovine respiratory syncytial virus (BRSV).

Sublines A and H of previously isolated, immortalized, and characterized (CD14-positive) ovine microglial cells were used. Bovine turbinate cells and goat synovial membrane cells were used for comparison. Cytopathic changes were used to confirm infection of individual wells, which were then counted and used to calculate the 50% tissue culture infectious dose. Uninoculated cells served as negative controls and confirmed that the cells were not previously infected with these viruses using polymerase chain reaction (PCR).

Inoculation of the two microglial cell sublines with laboratory and field isolates of BVDV, BoHV-1, and BRSV resulted in viral infection in a manner similar to bovine turbinate cells. Immortalized microglia cells are also permissive to SRLV, similar to goat synovial membrane cells.

These immortalized sheep microglial cells provide a new tool for the study of ruminant viruses in ruminant microglial cell line.