Abstract
Purpose :
The role of neuropeptides in the maintenance and reactivation of latent HSV-1 is not well studied. In this study, we determined the level of CGRP neuropeptide during ex-vivo reactivation of HSV-1 from the latent TG culture. We also measured the outcome of in vivo administration of CGRP antagonist CGRP8-37 in latently infected mice on viral reactivation.
Methods :
HSV-1 infection was carried out by corneal scratching followed by topical application of HSV-1RE in the scratched eye. The cytopathic effect because of the addition of supernatant from latent TG culture to Vero cell culture signified the reactivation of the latent virus. The copy number of glycoprotein B (gB) and latency-associated transcript (LAT) in latent TGs on different days post-culture were determined by quantitative polymerase chain reaction. The viral reactivation was further confirmed by HSV-1 antigen staining in cryo-sectioned TGs obtained from different days post-culture. The TGs were collected on 0-, 2-, and 4-day post-culture, followed by acetic acid extraction, and then EIA was performed to determine the CGRP level. α-CGRP (8-37)/vehicle was injected intraperitoneally into HSV-1RE infected mice during the latent stage of infection. Ex-vivo TG culture from the antagonist and vehicle-treated mice determined viral reactivation.
Results :
Our data show the reactivation of HSV-1 in latent TG culture on day 3 or day 4 post-culture. The increasing trend of gB copy number and decreasing trend of LAT copy number in latent TG at 2- and 4-day post-culture corroborated with the viral reactivation. HSV-1 antigen staining seen in cryo-sectioned TG further demonstrated the HSV-1 reactivation in latent TG. The EIA results showed a significantly reduced level of CGRP in latent than uninfected TG. However, during the initial stages of ex-vivo viral reactivation, a significant increase in CGRP level was seen in the latent TG. Furthermore, in vivo blocking of CGRP signaling, using CGRP 8-37 antagonist, in the latently infected mice delayed ex-vivo reactivation of HSV-1 from the latent TG.
Conclusions :
Our data documents the possible involvement of CGRP neuropeptide in promoting reactivation of HSV-1 from the latent TG. The ongoing experiments are determining the underlying mechanisms by which CGRP regulates HSV-1 reactivation.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.