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Kati Tormanen, Shaohui Wang, Ujjaldeep Jaggi, Jack Yu, Homayon Ghiasi; HSV-1 virus lacking the small non-coding RNA 1 (sncRNA1) region has increased virulence in ocularly infected mice. Invest. Ophthalmol. Vis. Sci. 2021;62(8):2685.
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© ARVO (1962-2015); The Authors (2016-present)
HSV-1 LAT locus contains several miRNA and two sncRNA sequences. Currently, the function of the two sncRNAs in vivo is largely unknown. LAT is known to play a role in efficient establishment of latency and wild type reactivation, which are in part dependent on the antiapoptotic activity of LAT. Recently, the sncRNA sequences of LAT were shown to promote cell survival in vitro. Therefore, we tested what role, if any, one of these two sncRNAs is playing in vitro and in vivo by constructing a mutant virus (ΔsncRNA1), which lacks the sncRNA1 sequence.
We constructed an HSV-1 recombinant virus lacking sncRNA1 in McKrae background (i.e., ΔsncRNA1). Replication of the ΔsncRNA1 virus, was measured by plaque assay and LAT stability and expression of ICP0, ICP4 and gB transcripts in infected cells were measured by qRT-PCR. Female C57BL/6 mice were infected ocularly with 2x105 PFU/eye of wild type (WT) HSV-1 strain McKrae, LAT-deficient HSV-1 (dLAT2903) or ΔsncRNA1 virus. Virus replication in the eye (days 1-7) and eye disease (day 28) were determined. Level of latency, expression of viral and host transcripts and reactivation from latency were measured on day 28 post infection.
Deletion of the 62 bp sncRNA1 sequence was verified by whole genome sequencing of the mutant virus. ΔsncRNA1 replicated slightly less efficiently in vitro, but similar to dLAT2903 and wt McKrae in vivo. There were no differences in eye disease, latency or reactivation between ΔsncRNA1 and wt McKrae. Interestingly, mouse mortality after ocular infection with ΔsncRNA1 was significantly higher when compared to either dLAT2903 or wt McKrae.
Our results suggest that sncRNA1 sequence of LAT may act to dampen the virulence of HSV-1 during an acute infection. The exact mechanism is currently not known, but likely involves regulating the host immune response to the virus. This hypothesis is currently being tested by Nanostring® assays.
This is a 2021 ARVO Annual Meeting abstract.
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