Herpes simplex virus 2 expresses a novel form of ICP34.5, a major viral neurovirulence factor, through regulated alternative splicing

ER stress induces caspase-2-tBID-GSDME-dependent cell death in neurons lytically infected with herpes simplex virus type 2

Neurotropic viruses, including herpes simplex virus (HSV) types 1 and 2, have the capacity to infect neurons and can cause severe diseases. This is associated with neuronal cell death, which may contribute to morbidity or even mortality if the infection is not controlled. However, the mechanistic details of HSV-induced neuronal cell death remain enigmatic. Here, we report that lytic HSV-2 infection of human neuron-like SH-SY5Y cells and primary human and murine brain cells leads to cell death mediated by gasdermin E (GSDME). HSV-2-induced GSDME-mediated cell death occurs downstream of replication-induced endoplasmic reticulum stress driven by inositol-requiring kinase 1α (IRE1α), leading to activation of caspase-2, cleavage of the pro-apoptotic protein BH3-interacting domain death agonist (BID), and mitochondria-dependent activation of caspase-3. Finally, necrotic neurons released alarmins, which activated inflammatory responses in human iPSC-derived microglia. In conclusion, lytic HSV infection in neurons activates an ER stress-driven pathway to execute GSDME-mediated cell death and promote inflammation.

Interplay between Autophagy and Herpes Simplex Virus Type 1: ICP34.5, One of the Main Actors

Herpes simplex virus type 1 (HSV-1) is a neurotropic virus that occasionally may spread to the central nervous system (CNS), being the most common cause of sporadic encephalitis. One of the main neurovirulence factors of HSV-1 is the protein ICP34.5, which although it initially seems to be relevant only in neuronal infections, it can also promote viral replication in non-neuronal cells. New ICP34.5 functions have been discovered during recent years, and some of them have been questioned. This review describes the mechanisms of ICP34.5 to control cellular antiviral responses and debates its most controversial functions. One of the most discussed roles of ICP34.5 is autophagy inhibition. Although autophagy is considered a defense mechanism against viral infections, current evidence suggests that this antiviral function is only one side of the coin. Different types of autophagic pathways interact with HSV-1 impairing or enhancing the infection, and both the virus and the host cell modulate these pathways to tip the scales in its favor. In this review, we summarize the recent progress on the interplay between autophagy and HSV-1, focusing on the intricate role of ICP34.5 in the modulation of this pathway to fight the battle against cellular defenses.

A Review of the Multipronged Attack of Herpes Simplex Virus 1 on the Host Transcriptional Machinery

During lytic infection, herpes simplex virus (HSV) 1 induces a rapid shutoff of host RNA synthesis while redirecting transcriptional machinery to viral genes. In addition to being a major human pathogen, there is burgeoning clinical interest in HSV as a vector in gene delivery and oncolytic therapies, necessitating research into transcriptional control. This review summarizes the array of impacts that HSV has on RNA Polymerase (Pol) II, which transcribes all mRNA in infected cells. We discuss alterations in Pol II holoenzymes, post-translational modifications, and how viral proteins regulate specific activities such as promoter-proximal pausing, splicing, histone repositioning, and termination with respect to host genes. Recent technological innovations that have reshaped our understanding of previous observations are summarized in detail, along with specific research directions and technical considerations for future studies.

Antiviral activity of 1,4-disubstituted-1,2,3-triazoles against HSV-1 in vitro

BACKGROUND

Herpes simplex virus 1 (HSV-1) affects a large part of the adult population. Anti-HSV-1 drugs, such as acyclovir, target thymidine kinase and viral DNA polymerase. However, the emerging of resistance of HSV-1 alerts for the urgency in developing new antivirals with other therapeutic targets. Thus, this study evaluated a series of 1,4-disubstituted-1,2,3-triazole derivatives against HSV-1 acute infection and provided deeper insights into the possible mechanisms of action.

METHODS

Human fibroblast cells (HFL-1) were infected with HSV-1 17syn+ and treated with the triazole compounds at 50 μM for 24 h. The 50% effective drug concentration (EC₅₀) was determined for the active compounds. Their cytotoxicity was also evaluated in HFL-1 with the 50% cytotoxic concentration (CC₅₀) determined using CellTiter-Glo^® solution. The most promising compounds were evaluated by virucidal activity and influence on virus egress, DNA replication and transcription, and effect on an acyclovir-resistant HSV-1 strain.

RESULTS

Compounds 3 ((E)-4-methyl-N'-(2-(4-(phenoxymethyl)-1H-1,2,3-triazol1yl)benzylidene)benzenesulfonohydrazide) and 4 (2,2'-(4,4'-((1,3-phenylenebis(oxy))bis(methylene))bis(1H-1,2,3-triazole-4,1 diyl)) dibenzaldehyde) were the most promising, with an EC₅₀ of 16 and 21 μM and CC₅₀ of 285 and 2,593 μM, respectively. Compound 3 was able to inhibit acyclovir-resistant strain replication and to interfere with virus egress. Both compounds did not affect viral DNA replication, but inhibited significantly the expression of ICP0, ICP4 and gC. Compound 4 also affected the transcription of UL30 and ICP34.5.

CONCLUSIONS

Our findings demonstrated that these compounds are promising antiviral candidates with different mechanisms of action from acyclovir and further studies are merited.

Hidden regulation of herpes simplex virus 1 pre-mRNA splicing and polyadenylation by virally encoded immediate early gene ICP27

In contrast to human cells, very few HSV-1 genes are known to be spliced, although the same pre-mRNA processing machinery is shared. Here, through global analysis of splice junctions in cells infected with HSV-1 and an HSV-1 mutant virus with deletion of infectious cell culture protein 27 (ICP27), one of two viral immediate early (IE) genes essential for viral replication, we identify hundreds of novel alternative splice junctions mapping to both previously known HSV-1 spliced genes and previously unknown spliced genes, the majority of which alter the coding potential of viral genes. Quantitative and qualitative splicing efficiency analysis of these novel alternatively spliced genes based on RNA-Seq and RT-PCR reveals that splicing at these novel splice sites is efficient only when ICP27 is absent; while in wildtype HSV-1 infected cells, the splicing of these novel splice junctions is largely silenced in a gene/sequence specific manner, suggesting that ICP27 not only promotes accumulation of ICP27 targeted transcripts but also ensures correctness of the functional coding sequences through inhibition of alternative splicing. Furthermore, ICP27 toggles expression of ICP34.5, the major viral neurovirulence factor, through inhibition of splicing and activation of a proximal polyadenylation signal (PAS) in the newly identified intron, revealing a novel regulatory mechanism for expression of a viral gene. Thus, through the viral IE protein ICP27, HSV-1 co-opts both splicing and polyadenylation machinery to achieve optimal viral gene expression during lytic infection. On the other hand, during latent infection when ICP27 is absent, HSV-1 likely takes advantages of host splicing machinery to restrict expression of randomly activated antigenic viral genes to achieve immune evasion.

Little is known regarding to how HSV, a large DNA virus and known to contain very few spliced genes, escapes host pre-mRNA splicing machinery. Here, by establishing a high throughput splice junction identification platform and quantitative analysis method to assess splicing efficiency based on high throughput data, we find that HSV-1 encodes hundreds of previously unknown alternative splice junctions; however, splicing of these novel spliced genes is largely silenced in wild-type HSV-1 infected cells, explaining why only very few spliced genes have been previously identified in HSV-1. Moreover, ICP27 is required for splicing inhibition and 3’ end formation of ICP34.5, the major viral neurovirulence factor and also the major target of latently expressed viral miRNAs. These findings not only fundamentally change the view of HSV gene structure, but also reveal a mechanism by which HSV employs host splicing and polyadenylation machineries to achieve optimal gene expression during acute infection and may also contribute to immune evasion during latency when ICP27 is not expressed.

A novel oncolytic herpes simplex virus armed with the carboxyl-terminus of murine MyD116 has enhanced anti-tumour efficacy against human breast cancer cells

Oncolytic herpes simplex virus-1 (oHSV-1) vectors are promising therapeutic agents for cancer. The deletion of the γ34.5 gene eliminates the neurovirulence but attenuates virus replication at the same time. The carboxyl-terminus of protein phosphatase 1 regulatory subunit 15A (also known as MyD116/GADD34) is homologous to that of γ34.5; hence, it may substitute for γ34.5 to enhance the replication and cytotoxicity of the virus. To investigate whether the C-terminus of MyD116 can enhance the anti-tumour efficacy of G47Δ on human breast cancer cells, a GD116 mutant was constructed by inserting a γ34.5-MyD116 chimaera into the G47Δ genome using a bacterial artificial chromosome and two recombinase systems (Cre/loxP and FLPE/FRT). A GD-empty mutant containing only the cytomegalovirus sequence was also created as a control using the same method. Next, the replication and cytotoxicity of these two virus vectors were evaluated in breast cancer cells. Compared with the GD-empty vector, GD116 possessed an enhanced replication capability and oncolytic activity in MCF-7 and MDA-MB-231 cells. On the fifth day after infection with GD116 at MOIs of 0.01 and 0.1, 49.2 and 82.8% of MCF-7 cells, respectively, were killed, with 35.0 and 50.2% of MDA-MB-231 cells, respectively, killed by GD116 at MOIs of 0.1 and 0.3. Additionally, the insertion of the γ34.5-MyD116 chimaera promoted virus replication in MDA-MB-468 at 48 h after infection, although no increased cytotoxic effect was observed. The findings of the present study indicate that the C terminus of the MyD116 gene can be substituted for the corresponding domain of the γ34.5 gene of oHSV-1 to promote the replication of the virus in infected cells. Furthermore, the novel virus mutant GD116 armed with a γ34.5-MyD116 chimaera has enhanced anti-tumour efficacy against human breast cancer cells in vitro.

Varicella-Zoster Virus Infectious Cycle: ER Stress, Autophagic Flux, and Amphisome-Mediated Trafficking

Varicella-zoster virus (VZV) induces abundant autophagy. Of the nine human herpesviruses, the VZV genome is the smallest (~124 kbp), lacking any known inhibitors of autophagy, such as the herpes simplex virus ICP34.5 neurovirulence gene. Therefore, this review assesses the evidence for VZV-induced cellular stress, endoplasmic-reticulum-associated degradation (ERAD), and autophagic flux during the VZV infectious cycle. Even though VZV is difficult to propagate in cell culture, the biosynthesis of the both N- and O-linked viral glycoproteins was found to be abundant. In turn, this biosynthesis provided evidence of endoplasmic reticulum (ER) stress, including a greatly enlarged ER and a greatly diminished production of cellular glycoproteins. Other signs of ER stress following VZV infection included detection of the alternatively spliced higher-molecular-weight form of XBP1 as well as CHOP. VZV infection in cultured cells leads to abundant autophagosome production, as was visualized by the detection of the microtubule-associated protein 1 light chain 3-II (LC3-II). The degree of autophagy induced by VZV infection is comparable to that induced in uninfected cells by serum starvation. The inhibition of autophagic flux by chemicals such as 3-methyladenine or ATG5 siRNA, followed by diminished virus spread and titers, has been observed. Since the latter observation pointed to the virus assembly/trafficking compartments, we purified VZ virions by ultracentrifugation and examined the virion fraction for components of the autophagy pathway. We detected LC3-II protein (an autophagy marker) as well as Rab11 protein, a component of the endosomal pathway. We also observed that the virion-containing vesicles were single-walled; thus, they are not autophagosomes. These results suggested that some VZ virions after secondary envelopment were transported to the outer cell membrane in a vesicle derived from both the autophagy and endosomal pathways, such as an amphisome. Thus, these results demonstrate that herpesvirus trafficking pathways can converge with the autophagy pathway.

Control of Candida albicans morphology and pathogenicity by post-transcriptional mechanisms

Candida albicans is a major human fungal pathogen responsible for both systemic and mucosal infections in a wide variety of immunocompromised individuals. Because the ability of C. albicans to undergo a reversible morphological transition from yeast to filaments is important for virulence, significant research efforts have focused on mechanisms that control this transition. While transcriptional and post-translational mechanisms have been well-studied, considerably less is known about the role of post-transcriptional mechanisms. However, in recent years several discoveries have begun to shed light on this important, but understudied, area. Here, I will review a variety of post-transcriptional mechanisms that have recently been shown to control C. albicans morphology, virulence and/or virulence-related processes, including those involving alternative transcript localization, mRNA stability and translation. I will also discuss the role that these mechanisms play in other pathogens as well as the potential they may hold to serve as targets for new antifungal strategies. Ultimately, gaining a better understanding of C. albicans post-transcriptional mechanisms will significantly improve our knowledge of how morphogenesis and virulence are controlled in fungal pathogens and open new avenues for the development of novel and more effective antifungals.

Herpes simplex virus ICP27 regulates alternative pre-mRNA polyadenylation and splicing in a sequence-dependent manner

The herpes simplex virus (HSV) infected cell culture polypeptide 27 (ICP27) protein is essential for virus infection of cells. Recent studies suggested that ICP27 inhibits splicing in a gene-specific manner via an unknown mechanism. Here, RNA-sequencing revealed that ICP27 not only inhibits splicing of certain introns in <1% of cellular genes, but also can promote use of alternative 5' splice sites. In addition, ICP27 induced expression of pre-mRNAs prematurely cleaved and polyadenylated from cryptic polyadenylation signals (PAS) located in intron 1 or 2 of ∼1% of cellular genes. These previously undescribed prematurely cleaved and polyadenylated pre-mRNAs, some of which contain novel ORFs, were typically intronless, <2 Kb in length, expressed early during viral infection, and efficiently exported to cytoplasm. Sequence analysis revealed that ICP27-targeted genes are GC-rich (as are HSV genes), contain cytosine-rich sequences near the 5' splice site, and have suboptimal splice sites in the impacted intron, suggesting that a common mechanism is shared between ICP27-mediated alternative polyadenylation and splicing. Optimization of splice site sequences or mutation of nearby cytosines eliminated ICP27-mediated splicing inhibition, and introduction of C-rich sequences to an ICP27-insensitive splicing reporter conferred this phenotype, supporting the inference that specific gene sequences confer susceptibility to ICP27. Although HSV is the first virus and ICP27 is the first viral protein shown to activate cryptic PASs in introns, we suspect that other viruses and cellular genes also encode this function.

Viral interactions with components of the splicing machinery

Eukaryotic genes are often interrupted by stretches of sequence with no protein coding potential or obvious function. After transcription, these interrupting sequences must be removed to give rise to the mature messenger RNA. This fundamental process is called RNA splicing and is achieved by complicated machinery made of protein and RNA that assembles around the RNA to be edited. Viruses also use RNA splicing to maximize their coding potential and economize on genetic space, and use clever strategies to manipulate the splicing machinery to their advantage. This article gives an overview of the splicing process and provides examples of viral strategies that make use of various components of the splicing system to promote their replicative cycle. Representative virus families have been selected to illustrate the interaction with various regulatory proteins and ribonucleoproteins. The unifying theme is fine regulation through protein-protein and protein-RNA interactions with the spliceosome components and associated factors to promote or prevent spliceosome assembly on given splice sites, in addition to a strong influence from cis-regulatory sequences on viral transcripts. Because there is an intimate coupling of splicing with the processes that direct mRNA biogenesis, a description of how these viruses couple the regulation of splicing with the retention or stability of mRNAs is also included. It seems that a unique balance of suppression and activation of splicing and nuclear export works optimally for each family of viruses.

Herpes Simplex Virus: The Interplay Between HSV, Host, and HIV-1

Herpes simplex virus proteins interact with host (human) proteins and create an environment conducive for its replication. Genital ulceration due to herpes simplex virus type 2 (HSV-2) infections is an important clinical manifestation reported to increase the risk of human immunodeficiency virus type 1 (HIV-1) acquisition and replication in HIV-1/HSV-2 coinfection. Dampening the innate and adaptive immune responses of the skin-resident dendritic cells, HSV-2 not only helps itself, but creates a "yellow brick road" for one of the most dreaded viruses HIV, which is transmitted mainly through the sexual route. Although, data from clinical trials show that HSV-2 suppression reduces HIV-1 viral load, there are hardly any reports presenting conclusive evidence on the impact of HSV-2 coinfection on HIV-1 disease progression. Be that as it may, understanding the interplay between these three characters (HSV, host, and HIV-1) is imperative. This review endeavors to collate studies on the influence of HSV-derived proteins on the host response and HIV-1 replication. Studying such complex interactions may help in designing and developing common strategies for the two viruses to keep these "partners in crime" at bay.

Basal Autophagy Is Required for Herpes simplex Virus-2 Infection

Autophagy is a conserved catabolic process of the cell, which plays an important role in regulating plethora of infections. The role of autophagy in Herpes simplex virus-2 (HSV-2) infection is unknown. Here, we found that HSV-2 does not allow induction of an autophagic response to infection, but maintains basal autophagy levels mostly unchanged during productive infection. Thus, we investigated the importance of basal autophagy for HSV-2 infection, using pharmacological autophagy suppression or cells genetically deficient in an autophagy-essential gene (ATG5). Interference with basal autophagy flux in cells significantly reduced viral replication and diminished the infection. These results indicate that basal autophagy plays an indispensable role required for a productive infection. Importantly, this study draws a sharp distinction between induced and basal autophagy, where the former acts as a viral clearance mechanism abrogating infection, while the latter supports infection.

Marek's disease: Genetic regulation of gallid herpesvirus 2 infection and latency

Gallid herpesvirus-2 (GaHV-2) is an oncogenic α-herpesvirus that causes Marek's disease (MD), a T cell lymphosarcoma (lymphoma) of domestic fowl (chickens). The GaHV-2 genome integrates by homologous recombination into the host genome and, by modulating expression of viral and cellular genes, induces transformation of latently infected cells. MD is a unique model of viral oncogenesis. Mechanisms implicated in the regulation of viral and cellular genes during GaHV-2 infection operate at transcriptional, post-transcriptional and post-translational levels, with involvement of viral and cellular transcription factors, along with epigenetic modifications, alternative splicing, microRNAs and post-translational modifications of viral proteins. Meq, the major oncogenic protein of GaHV-2, is a viral transcription factor that modulates expression of viral genes, for example by binding to the viral bidirectional promoter of the pp38-pp24/1.8 kb mRNA, and also modulates expression of cellular genes, such as Bcl-2 and matrix metalloproteinase 3. GaHV-2 expresses viral telomerase RNA subunit (vTR), which forms a complex with the cellular telomerase reverse transcriptase (TERT), thus contributing to tumorigenesis, while vTR independent of telomerase activity is implicated in metastasis. Expression of a viral interleukin 8 homologue may contribute to lymphomagenesis. Inhibition of expression of the pro-apoptotic factors JARID2 and SMAD2 by viral microRNAs may promote the survival and proliferation of GaHV-2 latently infected cells, thus enhancing tumorigenesis, while inhibition of interleukin 18 by viral microRNAs may be involved in evasion of immune surveillance. Viral envelope glycoproteins derived from glycoprotein B (gp60 and gp49), as well as glycoprotein C, may also play a role in immune evasion.

An investigation of herpes simplex virus type 1 latency in a novel mouse dorsal root ganglion model suggests a role for ICP34.5 in reactivation

After a primary lytic infection at the epithelia, herpes simplex virus type 1 (HSV-1) enters the innervating sensory neurons and translocates to the nucleus, where it establishes a quiescent latent infection. Periodically, the virus can reactivate and the progeny viruses spread back to the epithelium. Here, we introduce an embryonic mouse dorsal root ganglion (DRG) culture system, which can be used to study the mechanisms that control the establishment, maintenance and reactivation from latency. Use of acyclovir is not necessary in our model. We examined different phases of the HSV-1 life cycle in DRG neurons, and showed that WT HSV-1 could establish both lytic and latent form of infection in the cells. After reactivating stimulus, the WT viruses showed all markers of true reactivation. In addition, we showed that deletion of the γ(1)34.5 gene rendered the virus incapable of reactivation, even though the virus was clearly able to replicate and persist in a quiescent form in the DRG neurons.

Functional comparison of herpes simplex virus 1 (HSV-1) and HSV-2 ICP27 homologs reveals a role for ICP27 in virion release

Numerous studies have focused on the regulatory functions of ICP27, an immediate-early (IE) protein of herpes simplex virus 1 (HSV-1). However, its homolog in HSV-2, termed ICP27t2, has been little studied. Here, we used two different approaches to functionally compare ICP27t2 and ICP27. In transfection-based assays, ICP27t2 closely resembled ICP27 in its capacity to enhance HSV-1 late gene expression, suppress the splicing of a viral intron, and complement the growth of an HSV-1 ICP27 null mutant. To study ICP27t2 in the context of viral infection, we engineered K2F1, an HSV-1 mutant that encodes ICP27t2 in place of ICP27. In Vero cells, K2F1 replicated with wild-type (WT) kinetics and yields, expressed delayed-early and late proteins normally, and was fully capable of activating several cellular signal transduction pathways that are ICP27 dependent. Thus, we conclude that ICP27t2 and ICP27 are functionally very similar and that ICP27t2 can mediate all ICP27 activities that are required for HSV-1 replication in cell culture. Surprisingly, however, we found that K2F1 forms plaques that are morphologically different from those of WT HSV-1. Investigation of this trait demonstrated that it results from the decreased release of progeny virions into the culture medium. This appears to be due to a reduction in the detachment of K2F1 progeny from the extracellular surface of the infected cell. We identified two HSV-1 ICP27 amino-terminal deletion mutants with a similar release defect. Together, these results demonstrate that ICP27 plays a heretofore-unappreciated role in modulating the efficiency of progeny virion release.

IMPORTANCE

ICP27 is an essential, multifunctional regulatory protein that has a number of critical roles in the HSV-1 life cycle. Although ICP27 homologs are encoded by all known members of the Herpesviridae, previous work with several of these homologs has shown that they cannot substitute for ICP27 in the context of HSV-1-infected cells. Here, we identify ICP27t2 as the first homolog that can efficiently replace ICP27 in HSV-1 infection. Unexpectedly, our results also reveal that the sequence of the ICP27 gene can affect the release of HSV-1 progeny virions from the infected cell. Thus, our comparative study has revealed a novel function for ICP27 in the regulation of virus release.

Autophagic flux without a block differentiates varicella-zoster virus infection from herpes simplex virus infection

Autophagy is a process by which misfolded and damaged proteins are sequestered into autophagosomes, before degradation in and recycling from lysosomes. We have extensively studied the role of autophagy in varicella-zoster virus (VZV) infection, and have observed that vesicular cells are filled with >100 autophagosomes that are easily detectable after immunolabeling for the LC3 protein. To confirm our hypothesis that increased autophagosome formation was not secondary to a block, we examined all conditions of VZV infection as well as carrying out two assessments of autophagic flux. We first investigated autophagy in human skin xenografts in the severe combined immunodeficiency (SCID) mouse model of VZV pathogenesis, and observed that autophagosomes were abundant in infected human skin tissues. We next investigated autophagy following infection with sonically prepared cell-free virus in cultured cells. Under these conditions, autophagy was detected in a majority of infected cells, but was much less than that seen after an infected-cell inoculum. In other words, inoculation with lower-titered cell-free virus did not reflect the level of stress to the VZV-infected cell that was seen after inoculation of human skin in the SCID mouse model or monolayers with higher-titered infected cells. Finally, we investigated VZV-induced autophagic flux by two different methods (radiolabeling proteins and a dual-colored LC3 plasmid); both showed no evidence of a block in autophagy. Overall, therefore, autophagy within a VZV-infected cell was remarkably different from autophagy within an HSV-infected cell, whose genome contains two modifiers of autophagy, ICP34.5 and US11, not present in VZV.

Herpes simplex virus 2 ICP34.5 confers neurovirulence by regulating the type I interferon response

The γ34.5 gene of herpes simplex virus (HSV) 2 encodes ICP34.5, which enhances HSV-2 neurovirulence by an unknown mechanism. We found that an HSV-2 γ34.5-null mutant (γ34.5(-/-)) replicated less robustly than its rescue virus (γ34.5R) in wild-type mouse embryo fibroblasts (MEFs), and in cells primed with IFNβ. Increased eIF2α phosphorylation correlated with γ34.5(-/-) attenuation. However, γ34.5(-/-) achieved titers equivalent to γ34.5R in MEFs lacking the type I IFN receptor (IFNα/βR(-/-)) or lacking protein kinase R. γ34.5(-/-) also replicated poorly in the vaginal mucosa of wild-type mice, caused little genital inflammation, and spread to the nervous system at lower levels compared to γ34.5R. In IFNα/βR(-/-) mice, however, γ34.5(-/-) regained the capacity to replicate and cause disease equivalent to γ34.5R after intravaginal infection or direct inoculation into the central nervous system. Thus, the capacity of HSV-2 ICP34.5 to interdict the type I IFN response in vivo largely determines its neurovirulence.

Global gene expression changes in human peripheral blood after H7N9 infection

A novel avian influenza A virus (H7N9) of human infection emerged in eastern China in 2013, causing mild to lethal human respiratory infections. However, the underlying molecular mechanism remains largely unknown. In this work, we attempt to gain insights into the underlying genetic basis of this disease at the transcription level. We collected peripheral blood samples from patients with H7N9 infection and healthy people, and then we performed transcriptome profiling to comprehensively investigate their expression signatures, which would help us to better understand the molecular basis of the etiology upon viral infection. By employing the high throughput RNA-seq analysis of samples with and without H7N9 viral infection, we totally identified 1091 significantly differentially expressed genes. We found that several biological pathways related to the immunity and inflammation response in the differentially expressed genes. A genome-wide screening of gene regulation between H7N9 virus carrier and healthy people provided some insights into understanding and responsiveness to this potential threat.

Up to four distinct polypeptides are produced from the γ34.5 open reading frame of herpes simplex virus 2

The herpes simplex virus 1 (HSV-1) ICP34.5 protein strongly influences neurovirulence and regulates several cellular antiviral responses. Despite the clinical importance of HSV-2, relatively little is known about its ICP34.5 ortholog. We found that HSV-2 produces up to four distinct forms of ICP34.5 in infected cells: a full-length protein, one shorter form sharing the N terminus, and two shorter forms sharing the C terminus. These forms appeared with similar kinetics and accumulated in cells over much of the replication cycle. We confirmed that the N-terminal form is translated from the primary unspliced transcript to a stop codon within the intron unique to HSV-2 γ34.5. We found that the N-terminal form was produced in a variety of cell types and by 9 of 10 clinical isolates. ICP27 influenced but was not required for expression of the N-terminal form. Western blotting and reverse transcription-PCR indicated the C-terminal forms did not contain the N terminus and were not products of alternative splicing or internal transcript initiation. Expression plasmids encoding methionine at amino acids 56 and 70 generated products that comigrated in SDS-PAGE with the C1 and C2 forms, respectively, and mutation of these sites abolished C1 and C2. Using a recombinant HSV-2 encoding hemagglutinin (HA)-tagged ICP34.5, we demonstrated that the C-terminal forms were also produced during infection of many human and mouse cell types but were not detectable in mouse primary neurons. The protein diversity generated from the HSV-2 γ34.5 open reading frame implies additional layers of cellular regulation through potential independent activities associated with the various forms of ICP34.5.

IMPORTANCE

The herpes simplex virus 1 (HSV-1) protein ICP34.5, encoded by the γ34.5 gene, interferes with several host defense mechanisms by binding cellular proteins that would otherwise stimulate the cell's autophagic, translational-arrest, and type I interferon responses to virus infection. ICP34.5 also plays a crucial role in determining the severity of nervous system infections with HSV-1 and HSV-2. The HSV-2 γ34.5 gene contains an intron not present in HSV-1 γ34.5. A shorter N-terminal form of HSV-2 ICP34.5 can be translated from the unspliced γ34.5 mRNA. Here, we show that two additional forms consisting of the C-terminal portion of ICP34.5 are generated in infected cells. Production of these N- and C-terminal forms is highly conserved among HSV-2 strains, including many clinical isolates, and they are broadly expressed in several cell types, but not mouse primary neurons. Multiple ICP34.5 polypeptides add additional complexity to potential functional interactions influencing HSV-2 neurovirulence.