Bat-mouse bone marrow chimera: a novel animal model for dissecting the uniqueness of the bat immune system

Yong, Kylie Su Mei; Ng, Justin Han Jia; Her, Zhisheng; Hey, Ying Ying; Tan, Sue Yee; Tan, Wilson Wei Sheng; Irac, Sergio Erdal; Liu, Min; Chan, Xue Ying; Gunawan, Merry; Foo, Randy Jee Hiang; Low, Dolyce Hong Wen; Mendenhall, Ian Hewitt; Chionh, Yok Teng; Dutertre, Charles-Antoine; Chen, Qingfeng; Wang, Lin-Fa

The reconstituted bat immune system is functional in bat-mice. The demonstration of a functional bat immune system in NSG mice recipient holds a fundamental importance for the potential utility of this model. To investigate if bat-mice have a functional immune system, 24-week old bat-mice that were generated by injecting 1 × 10 5 BM cells during their neonatal stage (Fig. 4a) were immunized with 4-Hydroxy-3-Nitrophenylacetyl hapten conjugated to keyhole limpet hemocyanin (NP-KLH) using incomplete Freund's adjuvant (IFA) as an adjuvant to determine whether antigen-specific adaptive immune responses can be achieved in bat-mice. An ELISA based system was used to detect NP-specific bat antibodies using NP31-BSA as the ELISA antigen so that only NP-reacting antibodies will lead to a positive reading. Sera samples from the 10 immunized bat-mice showed positive reactivity with NP-antigen whereas the pre-bleed of each bat-mice and samples from the immunized NSG control mice were all negative (Fig. 4b ). In addition, ELISA titers were determined for each of the immunized bat-mice (Fig. 4c) . To confirm that antibodies produced in bat-mice were bat-specific, western and dot blot experiments utilizing anti-bat IgG antibody not only demonstrated the specificity of the goat anti-bat IgG antibody used in this study but also affirmed that only bat and bat-mice were capable of producing bat IgG antibodies. In bats and bat-mice, IgG was detectable at a dilution of 1:2000 and 1:1000, respectively ( Supplementary Fig. 3 ). All together, these results confirmed that bat-mice were able to generate an antigen-specific response, therefore suggesting the presence of functional immune cells.