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

Subudhi, Sonu; Rapin, Noreen; Misra, Vikram

The immune response has two primary components, innate and adaptive. The host initially responds to infection by activating innate mechanisms. Genes such as those for sensing and repairing DNA damage and the inflammatory process are under positive selection in black flying foxes and David's myotis (Myotis davidii) [21] . For instance, there are mutations in the coding sequence of p53 functional domains that are unique to these bats. Interferons are the primary innate effector molecules that control viral replication. Several types of interferon have been identified in bats, especially Type I and Type III. Type I interferon is induced after virus infection in Egyptian fruit bats whereas Type III interferon is induced similarly in pteropid bats [22, 23] . It is interesting to note that interferon genes in black flying foxes have contracted in terms of diversity. The number of variants of interferon present in these bats is lower compared to those in the gene loci of ten other vertebrate species. Despite this decrease in interferon gene diversity, black flying foxes express these variants at higher basal levels than other mammalian species. This suggests that the interferon and interferon stimulated genes are constitutively expressed in these bats [18] . In contrast, a recent study of the genome of Egyptian fruit bats shows expanded diversity of Type I interferon genes. This, as well as expansion of various other immune genes, suggests novel modes of antiviral defense in bats of various species [24] . Novel modes of antiviral defenses could exist in other species of bats and future studies would help in revealing them.