Immune System Modulation and Viral Persistence in Bats: Understanding Viral Spillover

Subudhi, Sonu; Rapin, Noreen; Misra, Vikram

While bats are well prepared to control viral infections, they also have mechanisms to avoid over-induction of inflammatory genes. Such excessive inflammation is detrimental in vertebrates of other species, such as humans, and is linked to pathology [28] . So, it is beneficial for the bats to have evolved mechanisms that would allow them to control excessive inflammation. Cell culture experiments have shown that cells of several species of bats have an inhibitor molecule (cRel) binding site in the promoter region of tumor necrosis factor alpha (TNFα), a key inflammatory cytokine. In cells of big brown bats (Eptesicus fuscus), stimulated with poly I:C, a surrogate for double-stranded viral RNA, cRel actively suppresses TNFα expression [29] . Genome analysis of black flying foxes and David's myotis have also demonstrated positive selection pressure on the cRel gene [21] . This suggests that many bats have a mechanism to suppress the expression of TNFα, thereby maintaining a balanced response to viral infection.