Abstract
Purpose :
We previously demonstrated that HSV-1 glycoprotein K (gK) binds to SPP in vitro and this binding is required for cell surface expression of gK and virus replication. Thus, the goal of this study was to determine if conditional knockout mice lacking SPP expression may contribute to HSV-1 infectivity and pathogenesis in vivo.
Methods :
Originally, we attempted to make SPP knockout mice and our results suggested that mice lacking SPP are embryonically lethal. Thus, we made SPP conditional knockout mice with Tamoxifen inducible Cre. The SPP conditional knockout mice were treated with Tamoxifen to deplete SPP. WT (C57BL/6) and SPP conditional mice were infected ocularly with 2 X 105 PFU/eye of WT HSV-1 strain McKrae. Effect of the absence of SPP on viral replication in the eye of infected mice (days 1-5) and on latency-reactivation (day 28) in the trigeminal ganglia (TG) of ocularly infected mice was monitored using standard plaque assay and qRT-PCR.
Results :
Tamoxifen treatment reduced SPP RNA expression up to 93% in SPP conditional knockout mice, while the SPP protein was not detectable in the eye or TG of treated mice. The absence of SPP in Tamoxifen treated mice significantly reduced HSV-1 replication in the eye of ocularly infected mice compared with control mice. Similarly, the absence of SPP expression reduced the level of latency and time of reactivation compared with control mice. Decrease of latency in SPP depleted mice correlated with a significant decline in the level of CD8 and PD-1 expression compared with control mice. The SPP depleted mice also show higher cornea sensitivity within the first several days post infection.
Conclusions :
These results confirm our in vitro results and extend them by demonstrating for the first time that HSV-1 gK interaction with cellular SPP is required for virus infectivity and latency-reactivation in vivo. As there is currently no effective treatment for HSV-1 recurrences, blocking SPP-gK interaction may represent a clinically effective and expedient target in developing HSV-1 therapeutics
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.