HSV-1 small non-coding RNA (sncRNA) 1 and 2 activate the Herpes virus entry mediator (HVEM) promoter

A review of HSV pathogenesis, vaccine development, and advanced applications

Herpes simplex virus (HSV), an epidemic human pathogen threatening global public health, gains notoriety for its complex pathogenesis that encompasses lytic infection of mucosal cells, latent infection within neurons, and periodic reactivation. This intricate interplay, coupled with HSV's sophisticated immune evasion strategies, gives rise to various diseases, including genital lesions, neonatal encephalitis, and cancer. Despite more than 70 years of relentless research, an effective preventive or therapeutic vaccine against HSV has yet to emerge, primarily due to the limited understanding of virus-host interactions, which in turn impedes the identification of effective vaccine targets. However, HSV's unique pathological features, including its substantial genetic load capacity, high replicability, transmissibility, and neurotropism, render it a promising candidate for various applications, spanning oncolytic virotherapy, gene and immune therapies, and even as an imaging tracer in neuroscience. In this review, we comprehensively update recent breakthroughs in HSV pathogenesis and immune evasion, critically summarize the progress made in vaccine candidate development, and discuss the multifaceted applications of HSV as a biological tool. Importantly, we highlight both success and challenges, emphasizing the critical need for intensified research into HSV, with the aim of providing deeper insights that can not only advance HSV treatment strategies but also broaden its application horizons.

The anti-apoptotic function of HSV-1 LAT in neuronal cell cultures but not its function during reactivation correlates with expression of two small non-coding RNAs, sncRNA1&2

Multiple functions are associated with HSV-1 latency associated transcript (LAT), including establishment of latency, virus reactivation, and antiapoptotic activity. LAT encodes two sncRNAs that are not miRNAs and previously it was shown that they have antiapoptotic activity in vitro. To determine if we can separate the antiapoptotic function of LAT from its latency-reactivation function, we deleted sncRNA1 and sncRNA2 sequences in HSV-1 strain McKrae, creating ΔsncRNA1&2 recombinant virus. Deletion of the sncRNA1&2 in ΔsncRNA1&2 virus was confirmed by complete sequencing of ΔsncRNA1&2 virus and its parental virus. Replication of ΔsncRNA1&2 virus in tissue culture or in the eyes of WT infected mice was similar to that of HSV-1 strain McKrae (LAT-plus) and dLAT2903 (LAT-minus) viruses. The levels of gB DNA in trigeminal ganglia (TG) of mice latently infected with ΔsncRNA1&2 virus was intermediate to that of dLAT2903 and McKrae infected mice, while levels of LAT in TG of latently infected ΔsncRNA1&2 mice was significantly higher than in McKrae infected mice. Similarly, the levels of LAT expression in Neuro-2A cells infected with ΔsncRNA1&2 virus was significantly higher than in McKrae infected cells. Reactivation in TG of ΔsncRNA1&2 infected mice was similar to that of McKrae and time of reactivation in both groups were significantly faster than dLAT2903 infected mice. However, levels of apoptosis in Neuro-2A cells infected with ΔsncRNA1&2 virus was similar to that of dLAT2903 and significantly higher than that of McKrae infected cells. Our results suggest that the antiapoptotic function of LAT resides within the two sncRNAs, which works independently of its latency-reactivation function and it has suppressive effect on LAT expression in vivo and in vitro.

Impact of actin polymerization and filopodia formation on herpes simplex virus entry in epithelial, neuronal, and T lymphocyte cells

Herpes simplex virus type 1 (HSV-1) has been known as a common viral pathogen that can infect several parts of the body, leading to various clinical manifestations. According to this diverse manifestation, HSV-1 infection in many cell types was demonstrated. Besides the HSV-1 cell tropism, e.g., fibroblast, epithelial, mucosal cells, and neurons, HSV-1 infections can occur in human T lymphocyte cells, especially in activated T cells. In addition, several studies found that actin polymerization and filopodia formation support HSV-1 infection in diverse cell types. Hence, the goal of this review is to explore the mechanism of HSV-1 infection in various types of cells involving filopodia formation and highlight potential future directions for HSV-1 entry-related research. Moreover, this review covers several strategies for possible anti-HSV drugs focused on the entry step, offering insights into potential therapeutic interventions.

Binding of herpesvirus entry mediator (HVEM) and HSV-1 gD affect reactivation but not latency levels

Previously we reported that the HSV-1 latency associated transcript (LAT) specifically upregulates the cellular herpesvirus entry mediator (HVEM) but no other known HSV-1 receptors. HSV-1 glycoprotein D (gD) binds to HVEM but the effect of this interaction on latency-reactivation is not known. We found that the levels of latent viral genomes were not affected by the absence of gD binding to HVEM. However, reactivation of latent virus in trigeminal ganglia explant cultures was blocked in the absence of gD binding to HVEM. Neither differential HSV-1 replication and spread in the eye nor levels of latency influenced reactivation. Despite similar levels of latency, reactivation in the absence of gD binding to HVEM correlated with reduced T cell exhaustion. Our results indicate that HVEM-gD signaling plays a significant role in HSV-1 reactivation but not in ocular virus replication or levels of latency. The results presented here identify gD binding to HVEM as an important target that influences reactivation and survival of ganglion resident T cells but not levels of latency. This concept may also apply to other herpesviruses that engages HVEM.

Herpes Simplex Virus 1 MicroRNAs: An Update

BACKGROUND

Herpes simplex virus 1 (HSV-1), an important human pathogen, is capable of latent infection in neurons and productive (lytic) infection in other tissue cells. Once infected with HSV-1, the immune system of the organism cannot eliminate the virus and carries it lifelong. HSV-1 possesses approximately 150 kb of double-stranded linear genomic DNA and can encode at least 70 proteins and 37 mature microRNAs (miRNAs) derived from 18 precursor miRNAs (pre-miRNAs).

SUMMARY

These HSV-1-encoded miRNAs are widely involved in multiple processes in the life cycle of the virus and the host cell, including viral latent and lytic infection, as well as host cell immune signaling, proliferation, and apoptosis.

KEY MESSAGE

In this review, we focused primarily on recent advances in HSV-1-encoded miRNA expression, function, and mechanism, which may provide new research ideas and feasible research methods systemically and comprehensively.

A Comparison of Pseudorabies Virus Latency to Other A-Herpesvirinae Subfamily Members

Pseudorabies virus (PRV), the causative agent of Aujeszky’s disease, is one of the most important infectious pathogens threatening the global pig industry. Like other members of alphaherpesviruses, PRV establishes a lifelong latent infection and occasionally reactivates from latency after stress stimulus in infected pigs. Latent infected pigs can then serve as the source of recurrent infection, which is one of the difficulties for PRV eradication. Virus latency refers to the retention of viral complete genomes without production of infectious progeny virus; however, following stress stimulus, the virus can be reactivated into lytic infection, which is known as the latency-reactivation cycle. Recently, several research have indicated that alphaherpesvirus latency and reactivation is regulated by a complex interplay between virus, neurons, and the immune system. However, with those limited reports, the relevant advances in PRV latency are lagging behind. Therefore, in this review we focus on the regulatory mechanisms in PRV latency via summarizing the progress of PRV itself and that of other alphaherpesviruses, which will improve our understanding in the underlying mechanism of PRV latency and help design novel therapeutic strategies to control PRV latency.

Studies of Infection and Experimental Reactivation by Recombinant VZV with Mutations in Virally-Encoded Small Non-Coding RNA

Locked-nucleotide analog antagonists (LNAA) to four varicella zoster virus small non-coding RNA (VZVsncRNA 10-13) derived from the mRNA of the open reading frame (ORF) 61 gene individually reduce VZV replication in epithelial cells and fibroblasts. To study the potential roles VZVsncRNA 10-13 have in neuronal infection we generated two recombinant VZV; one in which 8 nucleotides were changed in VZVsncRNA10 without altering the encoded residues of ORF61 (VZVsnc10MUT) and a second containing a 12-nucleotide deletion of the sequence common to VZVsncRNA12 and 13, located in the ORF61 mRNA leader sequence (VZVsnc12-13DEL). Both were developed from a VZV BAC with a green fluorescent protein (GFP) reporter fused to the N terminal of the capsid protein encoded by ORF23. The growth of both mutant VZV in epithelial cells and fibroblasts was similar to that of the parental recombinant virus. Both mutants established productive infections and experimental latency in neurons derived from human embryonic stem cells (hESC). However, neurons that were latently infected with both VZV mutant viruses showed impaired ability to reactivate when given stimuli that successfully reactivated the parental virus. These results suggest that these VZVsncRNA may have a role in VZV latency maintenance and/or reactivation. The extension of these studies and confirmation of such roles could potentially inform the development of a non-reactivating, live VZV vaccine.

Small Noncoding RNA (sncRNA1) within the Latency-Associated Transcript Modulates Herpes Simplex Virus 1 Virulence and the Host Immune Response during Acute but Not Latent Infection

HSV-1 latency-associated transcript (LAT) plays a major role in establishing latency and reactivation; however, the mechanism by which LAT controls these processes is largely unknown. In this study, we sought to establish the role of the small noncoding RNA1 (sncRNA1) encoded within LAT during HSV-1 ocular infection. Our results suggest that sncRNA1 has a protective role during acute ocular infection by modulating the innate immune response to infection.