Brain-resident memory cells (bT RM) and virus reactivation

Abstract

Abstract Background Neuroimmune responses terminate MCMV acute infection, however, a subset of neurons still harbor latent viral genomes. Factors regulating viral reactivation remain to be elucidated. Methods Using RNAscope, IE1 nucleic acid was detected within brains at D5 and D30 p.i. Using real-time RT-PCR, we assessed expression of IE1, E1, and gB transcripts. Using multi-color flow cytometry, we assessed depletion of bT RMfollowing icv injection of either α-CD8 Ab or α-CD103-sap. Using luciferase-expressing transgenic mice, we longitudinally assessed reactivation of cre-MCMV after T-cell depletion using live small animal imaging. Explant assay was employed to study the role of bT RMin reactivation. Using Nanostring, we identified changes following bT RM-depletion. Results Brain infection was demonstrated by X-gal staining as well as IE1 staining using RNAscope at 5 d p.i. After 30 d p.i., the virus established latency, as indicated by absence of transcripts (IE1, E1, and gB). After establishment, we injected either α-CD8 Ab or α-CD103-sap into the brain and showed 90–95% T-cell depletion. We infected mice with cre-MCMV, which expresses Cre recombinase. We observed enhanced imaging signals indicative of IE promoter activity in depleted animals. Surprisingly, we efficiently recovered virus from untreated mice, but not from those depleted of bT RM. Furthermore, on Nanostring analysis, we identified gpnmband hmox1, upregulated 11.48- and 6.7-fold following bT RMdepletion. Conclusion When we depleted bT RM, there was transient IE expression, sufficient to activate surveying microglia. This eventually resulted in a tissue-wide anti-viral state. These data provide new insights into the role of bT RMin controlling reactivation. This project was supported by award numbers NS-038836 from the National Institute of Neurological Disorders and Stroke