The Mutation of the Genes Related to Neurovirulence in HSV-2 Produces an Attenuated Phenotype in Mice.

Lei Liu,Jingjing Zhang,Xingli Xu,Ying Zhang,Xueqi Li,Xiao Feng,Shengtao Fan,Qihan Li,Jishuai Cheng,Guorun Jiang,Lichun Wang,Xiangxiong Xu,Tangwei Mou,Yun Liao

doi:10.3390/v12070770

Abstract

HSV-2 (Herpes simplex virus type 2) is a critical viral agent that mainly causes genital herpes and life-long latent infection in the dorsal root ganglia. Gene modification via CRISPR/Cas9 Clustered regularly interspaced short palindromic repeat sequences/CRISPR associated 9) was used here to construct HSV-2 mutant strains through the deletion of fragments of the RL1 (Repeat Long element 1) and/or LAT (Latency-associated Transcript) genes. The HSV-2 mutant strains LAT-HSV-2 and RL1-LAT-HSV-2 present different biological properties. The proliferation of RL1-LAT-HSV-2 in nerve cells was decreased significantly, and the plaques induced by RL1-LAT-HSV-2 in Vero cells were smaller than those induced by LAT-HSV-2 mutant and wild-type strains. The observation of mice infected with these two mutants compared to mice infected with the wild-type strain indicated that the mutant RL1-LAT-HSV-2 has an attenuated phenotype with reduced pathogenicity during both acute and latent infections and induces a stronger specific immune response than the wild-type strain, whereas the attenuation effect was not found in mice infected with the LAT-HSV-2 mutant containing the LAT gene deletion. However, the simultaneous mutation of both the RL1 and LAT genes did not completely restrict viral proliferation in nerve cells, indicating that multiple HSV genes are involved in viral replication in the neural system. This work suggests that the HSV-2 genes RL1 and/or LAT might be involved in the virulence mechanisms in mouse infections.

Highlights

Human herpes simplex virus type 2 (HSV-2) is a member of the Herpesviridae subfamilyAlphaherpesvirinae [1], which causes genital herpes in the primary infection and rapidly penetrates the neurons distributed in these tissues, traveling along the axons to the dorsal root ganglion for a life-long latent infection [2,3]
These two genes are essential for latent viral infection and spontaneous reactivation, and a deficiency of RL1 and LAT genes can lead to reduced viral proliferation in nerve cells [2,15,26]
RL1-LAT-HSV-2 involved the deletion of both the introns and exons of the RL1 and LAT genes with 190 nt sequence deleted from the LAT gene and a 240 nt sequence deleted from the RL1 gene

Summary

Introduction

Human herpes simplex virus type 2 (HSV-2) is a member of the Herpesviridae subfamilyAlphaherpesvirinae [1], which causes genital herpes in the primary infection and rapidly penetrates the neurons distributed in these tissues, traveling along the axons to the dorsal root ganglion for a life-long latent infection [2,3]. Human herpes simplex virus type 2 (HSV-2) is a member of the Herpesviridae subfamily. There are many antiviral drugs in clinical practice that inhibit HSV-2 virus replication, such as acyclovir (ACV), which has been shown to reduce the occurrence of HSV-2 lesions by approximately 50% [12,13]. No obvious clinical effect on the suppression of the latent virus has been observed with these antiviral drugs, and they have certain side effects [12,13]. There are many live attenuated vaccines and subunit vaccines in clinical trials, the absence of effective HSV-2 prophylactic or therapeutic vaccines suggests that the mechanism of HSV-2 infection and immunity needs to be further explored

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Results

Conclusion