HSV Reactivation Research Articles

Physiological oxygen concentration during sympathetic primary neuron culture improves neuronal health and reduces HSV-1 reactivation.

Herpes simplex virus-1 (HSV-1) establishes a latent infection in peripheral neurons and periodically reactivates in response to a stimulus to permit transmission. In vitro models using primary neurons are invaluable to studying latent infection because they use bona fide neurons that have undergone differentiation and maturation in vivo. However, culture conditions in vitro should remain as close to those in vivo as possible. This is especially important when considering minimizing cell stress, as it is a well-known trigger of HSV reactivation. We recently developed an HSV-1 model system that requires neurons to be cultured for extended lengths of time. Therefore, we sought to refine culture conditions to optimize neuronal health and minimize secondary effects on latency and reactivation. Here, we demonstrate that culturing primary neurons under conditions closer to physiological oxygen concentrations (5% oxygen) results in cultures with features consistent with reduced stress. Furthermore, culture in these lower oxygen conditions diminishes the progression to full HSV-1 reactivation despite minimal impacts on latency establishment and earlier stages of HSV-1 reactivation. We anticipate that our findings will be useful for the broader microbiology community as they highlight the importance of considering physiological oxygen concentration in studying host-pathogen interactions.IMPORTANCEEstablishing models to investigate host-pathogen interactions requires mimicking physiological conditions as closely as possible. One consideration is the oxygen concentration used for in vitro tissue culture experiments. Standard incubators do not regulate oxygen levels, exposing cells to oxygen concentrations of approximately 18%. However, cells within the body are exposed to much lower oxygen concentrations, with physiological oxygen concentrations in the brain being 0.55%-8% oxygen. Here, we describe a model for herpes simplex virus 1 (HSV-1) latent infection using neurons cultured in 5% oxygen. We show that culturing neurons in more physiological oxygen concentrations improves neuronal health to permit long-term studies of virus-cell interactions and the impact on reactivation.

A fur plucking model to study herpes simplex virus reactivation and recurrent disease.

Herpes simplex viruses (HSV-1 and HSV-2) have infected over half of the US adult population to cause a lifelong, persistent infection; however, our understanding of the mechanisms that govern HSV reactivation and recurrent disease is incomplete. This is in part due to limitations in the animal models used to study recurrent disease, which are laborious and inefficient in mice. To address this technical gap, we developed a mouse model in which fur plucking after flank skin infection is sufficient to induce episodes of HSV reactivation and recurrent disease. Our work provides a model for the field to investigate the pathogenic mechanisms of HSV and immune responses during recurrent disease and provides an opportunity to investigate the neurobiology of HSV infection.

Single-cell RNA Sequencing Reveals the Diversity of the Immunological Landscape Response to Genital Herpes

Genital herpes (GH) is a common sexually transmitted disease, which is primarily caused by herpes simplex virus type 2 (HSV-2), and continues to be a global health concern. Although our understanding of the alterations in immune cell populations and immunomodulation in GH patients is still limited, it is evident that systemic intrinsic immunity, innate immunity, and adaptive immunity play crucial roles during HSV-2 infection and GH reactivation. To investigate the mechanisms underlying HSV-2 infection and recurrence, single-cell RNA sequencing (scRNA-seq) was performed on immune cells isolated from the peripheral blood of both healthy individuals and patients with recurrent GH. Furthermore, the systemic immune response in patients with recurrent GH showed activation of classical monocytes, CD4+ T cells, natural killer cells (NK cells), and plasmacytoid dendritic cells (pDCs), especially of genes associated with the Toll-like receptor signaling pathway and T cell activation. Circulating immune cells in GH patients show higher expression of genes associated with inflammation and antiviral responses both in the scRNA-Seq data set and in independent quantitative real-time polymerase chain reaction (qRT-PCR) analysis and ELISA experiments. This study demonstrated that localized genital herpes, resulting from HSV reactivation, may influence the functionality of circulating immune cells, suggesting a potential avenue for future research into the role of systemic immunity during HSV infection and recurrence.

Analysis of HSV1/2 Infection Reveals an Association between HSV-2 Reactivation and Pregnancy.

The herpes simplex viruses consist of the strains, HSV-1 and HSV-2, which are prevalent worldwide and lack a definitive cure. We aimed to explore the specific characteristics of HSV 1 and 2 infections, such as differences between gender assigned at birth, age at infection, site of infection, comorbidities, and effect of pregnancy, through a data analysis. Between 2011 and 2018, the Israeli Central Virology Laboratory diagnosed 9189 samples using multiplexed real-time PCR. In addition, we extracted all of the medical data for 287 females hospitalized at the Sheba Medical Center with HSV-1 (161) or HSV-2 (126) genital infections. HSV-2 was almost absent in the orofacial samples from both genders, while in other lesion sites, HSV-2 was significantly more abundant in females than in males (p < 0.05,). HSV-2 was initially detected at puberty. In the hospitalized females' malignancies, both HSV-1 and HSV-2 were found with a non-significant difference. Simultaneously, pregnancies were more common in females who were HSV-2-positive compared with those who were HSV-1-positive (27.8% vs. 12.4%, respectively, p < 0.01). Primary infections occur more with HSV-1 than with HSV-2 (15.6% vs. 3.2%, respectively). Our findings demonstrate that genital HSV-2 infection episodes are more frequent during pregnancy, suggesting that pregnancy may serve as a risk factor for HSV-2 reactivation or infection.

CRISPR-Cas9-mediated genome editing delivered by a single AAV9 vector inhibits HSV-1 reactivation in a latent rabbit keratitis model

CRISPR-Cas9-mediated genome editing delivered by a single AAV9 vector inhibits HSV-1 reactivation in a latent rabbit keratitis model

Physiological oxygen concentration during sympathetic primary neuron culture improves neuronal health and reduces HSV-1 reactivation.

Herpes simplex virus-1 (HSV-1) establishes a latent infection in peripheral neurons and periodically reactivates in response to a stimulus to permit transmission. In vitro models using primary neurons are invaluable to studying latent infection because they use bona fide neurons that have undergone differentiation and maturation in vivo. However, culture conditions in vitro should remain as close to those in vivo as possible. This is especially important when considering minimizing cell stress, as it is a well-known trigger of HSV reactivation. We recently developed an HSV-1 model system that requires neurons to be cultured for extended lengths of time. Therefore, we sought to refine culture conditions to optimize neuronal health and minimize secondary effects on latency and reactivation. Here, we demonstrate that culturing primary neurons under conditions closer to physiological oxygen concentrations (5% oxygen) results in cultures with features consistent with reduced stress. Furthermore, culture in these lower oxygen conditions diminishes the progression to full HSV-1 reactivation despite minimal impacts on latency establishment and earlier stages of HSV-1 reactivation. We anticipate that our findings will be useful for the broader microbiology community as they highlight the importance of considering physiological oxygen concentration in studying host-pathogen interactions.

Frequency and clinical significance of Herpes simplex virus type 1/2 reactivation in adult patients with mild to moderately severe community-acquired pneumonia: a multicentre cohort study.

This study assessed the frequency, clinical significance, and risk factors for Herpes simplex virus (HSV) reactivation in immunocompetent patients with community-acquired pneumonia (CAP). The study included adult CAP-patients who were enrolled in the CAPNETZ study between 2007 and 2017 and had a residual sputum sample available for analysis. In addition to routine diagnostics, sputum and blood samples were tested for HSV-1/2 using PCR. Demographics, comorbidities, and CRB-65 score were compared between HSV-positive and negative patients using Fisher exact or Mann Whitney test. Logistic regression analyses investigated the influence of HSV reactivation on a modified hospital recovery scale (HRS) until day 7, divided into 3 categories (no oxygen therapy, oxygen therapy, ICU admission or death). Among 245 patients, HSV-1 and HSV-2 were detected in 30 patients (12.2%, 95%CI 8.7-16.9) and 0 patients, respectively. All HSV-positive patients were hospitalized, had a CRB-65 severity score of 0-2 and survived the first 28day. In the HSV-positive group, patients had a non-significantly higher median age (70.5 versus 66years) and a higher rate of oncological comorbidities (16.7% versus 8.8%) compared to the HSV-negative group. Distribution of co-pathogens and outcome parameters did not significantly differ between both groups. In a multivariate logistic regression model, age (AOR 1.029, p = 0.012) and CRB-65 score (AOR 1.709, p = 0.048), but not HSV-1 as single or co-pathogen were independently associated with higher HRS. Our study suggests that HSV-1 reactivation is common in CAP but might not be associated with specific risk factors or a complicated disease course.

Co-option of mitochondrial nucleic acid sensing pathways by HSV-1 UL12.5 for reactivation from latent Infection.

Although viruses subvert innate immune pathways for their replication, there is evidence they can also co-opt anti-viral responses for their benefit. The ubiquitous human pathogen, Herpes Simplex Virus-1 (HSV-1), encodes a protein (UL12.5) that induces the release of mitochondrial nucleic acid into the cytosol, which activates immune sensing pathways and reduces productive replication in non-neuronal cells. HSV-1 establishes latency in neurons and can reactivate to cause disease. We found that UL12.5 is required for HSV-1 reactivation in neurons and acts to directly promote viral lytic gene expression during initial exit from latency. Further, the direct activation of innate immune sensing pathways triggered HSV reactivation and compensated for a lack of UL12.5. Finally, we found that the induction of HSV-1 lytic genes during reactivation required intact RNA and DNA sensing pathways, demonstrating that HSV-1 can both respond to and active antiviral nucleic acid sensing pathways to reactivate from a latent infection.

Expansion of the HSV-2-specific T cell repertoire in skin after immunotherapeutic HSV-2 vaccine.

The skin at the site of HSV-2 reactivation is enriched for HSV-2-specific T cells. To evaluate whether an immunotherapeutic vaccine could elicit skin-based memory T cells, we studied skin biopsies and HSV-2-reactive CD4+ T cells from PBMCs by T cell receptor (TCR) β chain (TRB) sequencing before and after vaccination with a replication-incompetent whole-virus HSV-2 vaccine candidate (HSV529). The representation of HSV-2-reactive CD4+ TRB sequences from PBMCs in the skin TRB repertoire increased after the first vaccine dose. We found sustained expansion after vaccination of unique, skin-based T cell clonotypes that were not detected in HSV-2-reactive CD4+ T cells isolated from PBMCs. In one participant, a switch in immunodominance occurred with the emergence of a TCR αβ pair after vaccination that was not detected in blood. This TCRαβ was shown to be HSV-2 reactive by expression of a synthetic TCR in a Jurkat-based NR4A1 reporter system. The skin in areas of HSV-2 reactivation possessed an oligoclonal TRB repertoire that was distinct from the circulation. Defining the influence of therapeutic vaccination on the HSV-2-specific TRB repertoire requires tissue-based evaluation.

Tear lactoferrin concentration in patients with recurrent herpetic stromal keratitis and therapeutic effect of Lacto eyedrops in the multicomponent treatment for this disorder

Background: Herpetic stromal keratitis (HSK) is an immunomodulatory disease that develops as a result of herpes simplex virus (HSV)1 or HSV2 reactivation. HSK is the most common form (20-50%) of recurrent herpetic keratitis (HK) that most commonly results in significantly reduced vision. It is well known that changes in biological compound levels in tear fluid can be indicative of the state of the ocular surface and determine whether ocular surface pathology is present, and, therefore, can be used as diagnostic markers of pathological changes in the ocular surface. Lactoferrin (LF) is one of these compounds and has been proven to have innate antibacterial, antifungal, antiviral, antiparasite, anti-inflammatory, immunomodulatory, antioxidative and other properties. Purpose: To determine tear Lf concentration in patients with recurrent acute HSK, its effect on functional characteristics of the ocular surface, and the therapeutic effect of Lacto eyedrops in the comprehensive treatment for this disorder. Material and Methods: The study was conducted at the site of Corneal Pathology Department and Immunology Laboratory of the Institute in January to December 2021. Seventeen patients (17 affected eyes and 17 fellow eyes) with recurrent acute HSK were included in the study. Mean patient age plus or minus standard deviation (SD) was 48.7 ± 16.0 years. The ophthalmological examination included biomicroscopy of the bulbar conjunctiva and cornea, fluorescein test, determination of corneal sensation and basal tear production (Schirmer’s II test), and microbiological examination of the conjunctiva. Tear Lf concentration was determined by a human Lf enzyme-linked immunosorbent assay (ELISA) kit (Elabscience Biotechnology, Inc., Wuhan, China). The results were photometrically measured at 450 nm with an ELISA reader (Stat Fax 2100, Awareness Technology Inc, Palm City, FL). Lacto eyedrops were administered two times a day for 30 days. Tear Lf concentrations were determined at baseline and at day 30. Results: Mean tear LF concentration plus or minus SD in eyes of patients with recurrent HSK was 1.21 ± 0.52 g/l, with no significant difference between the affected eye and fellow eye. However, a subnormal tear LF concentration was more common in the affected eye than in the fellow eye (2 = 4.24, р = 0.04). After a 30-day anti-inflammatory treatment with Lacto eyedrops, mean tear LF concentration plus or minus SD increased by 47% to 1.78 ± 0.7 g/l in the affected eyes. A corneal sensation score of 1 to 9 was 12.4 times more common in HSK eyes than in fellow eyes (OR = 12.4; 95% CI, 2.0–76.8), which reflects neurosensory abnormalities in the affected eye. Corneal sensation loss, was, however, more common in HSK eyes with a low tear Lf concentration than in fellow eyes with a low tear Lf concentration. Median basal tear production (as assessed by Schirmer’s II test) was as low as 7-8 mm in eyes with a low tear Lf concentration and as high as 13-16 mm in eyes with a high tear Lf concentration (p less 0.05). There was a direct correlation between the basal tear production and the tear Lf concentration (r=0.45; p less 0.05). Among study patients with recurrent HSK, 24.9% showed baseline microbiological evidence of potentially pathogenic or fungal organisms in the conjunctiva. A course of multicomponent anti-inflammatory treatment with Lacto eyedrops contributed to complete removal of these organisms. Conclusion: We determined mean tear Lf concentrations in affected and fellow eyes of patients with recurrent HSK, and established certain relationships between functional characteristics of the ocular surface and tear Lf concentrations in these eyes. A disinfecting effect of Lacto eyedrops against any microorganisms present in the conjunctival sac of patients with recurrent HSK was confirmed by the absence of culture growth on completion of the multicomponent anti-inflammatory treatment.

A randomized phase II study of acyclovir for the prevention of chemotherapy-induced oral mucositis in patients undergoing autologous hematopoietic stem cell transplantation

ObjectivesTo prove our hypothesis that acyclovir prophylaxis in autologous hematopoietic stem cell transplantation (AHSCT) recipients with hematologic malignancies (HM) reduces the incidence of chemotherapy-induced oral mucositis (CIOM) by inhibiting the intraoral HSV reactivation during the neutropenic period, we conducted a randomized phase II study of acyclovir for the prevention of CIOM in adult HSV sero-positive AHSCT recipients.MethodsPatients were randomized to either the study group (acyclovir 400 mg PO bid until neutrophil engraftment) or the control group (no prophylaxis) and received AHSCT. Oral examination and sampling for HSV were performed at three timepoints of AHSCT.ResultsIn 54 patients who were randomized (for intention-to-analysis), the incidence of CIOM was 16.0% (4/25 patients) and 58.6% (17/29 patients) in the study group and the control group, respectively (P = 0.001). In 49 patients who completed the study (for per-protocol analysis), the incidence of CIOM was 13.0% (3/23 patients) and 61.5% (16/26 patients) in the study group and the control group, respectively (P = 0.001). In addition, HSV-1 PCR positivity in the study group was significantly lower than that the control group (4.3% vs. 46.2%, P = 0.001). A strong association between the HSV-1 reactivation status and CIOM was reconfirmed.ConclusionsProphylactic use of oral acyclovir effectively reduced the incidence of CIOM in patients with HM who were undergoing AHSCT.Trial registrationsThis trial was registered at the Clinical Research Information Service in the Republic of Korea under the number KCT0003885 (registration date 03/05/2019).

Orthotopic Heart Transplantation Followed By Autologous Stem Cell Transplantation in Patients with Cardiac AL Amyloidosis: Results from a Single Centre Prospective Study

Background: Patients with advanced cardiac AL amyloidosis have a dismal prognosis, with an overall survival (OS) of only 5 months for Stage IIIb patients (Palladini et al, 2023). Induction chemotherapy followed by high dose chemotherapy and autologous stem cell transplantation (HDT and ASCT) has been widely used as treatment for AL amyloidosis. However, patients with advanced cardiac AL amyloidosis are often not suitable for HDT and ASCT due to high transplant related mortality (TRM). Orthotopic cardiac transplantation (OHT) following induction treatment may improve patient fitness and thus allow HDT and ASCT to deepen and prolong responses. We present our single centre, prospective study of patients with Stage IIIa and Stage IIIb cardiac AL amyloidosis who received OHT followed by sequential HDT and ASCT. Aims: The primary outcomes were 3 year OS and progression-free survival (PFS). Efficacy and safety were assessed as secondary outcomes. Efficacy was evaluated by light chain and cardiac response after ASCT. Safety was assessed by rate of TRM, cardiac rejection, opportunistic infections, and cytopenia related complications. Methods: During 2015 to 2021, patients with Stage IIIa or Stage IIIb AL amyloidosis aged under 65 years underwent OHT followed by HDT and ASCT. Patients with multiple myeloma were excluded. At approximately 6 months following OHT, patients underwent stem cell mobilization with granulocyte colony-stimulating factor alone followed by peripheral blood apheresis stem cell collection. Mycophenolate immunosuppression was temporarily withheld during stem cell mobilization and collection. Patients then received a high dose melphalan ASCT followed by 3-6 monthly assessments. Results: Nine patients (median age of 53 years, range 47-60 years) completed both OHT and ASCT. Seven other patients were screened but did not proceed with OHT. The cohort included both stage IIIa (55%) and stage IIIb (44%) patients. Most patients received cyclophosphamide-bortezomib-dexamethasone induction therapy (89%) and one patient received lenalidomide-bortezomib-dexamethasone. The median time from diagnosis of AL amyloidosis to OHT was 11 months (range 5-57 months) and median time from OHT to ASCT was 7 months (range 5-8 months). 3 year OS was 83% and PFS was 56% (Figure 1). At a median follow up of 37 months (range 17-69 months), 89% of patients remain alive. One patient with Stage IIIa disease who underwent HDT and ASCT with progressive disease (PD) died 28 months following ASCT due to PD. Subgroup analysis demonstrated 3 year OS in Stage IIIa patients of 75% compared to 100% in Stage IIIb (p=0.48). 3 year PFS was 53% in Stage IIIa patients and 66% in Stage IIIb (p=0.8). Patients in complete remission (CR) prior to ASCT had an improved 3 year OS of 100% compared to 66% for those in partial remission (PR) or with PD (p=0.32). 3 year PFS was significantly improved at 100% when ASCT occurred in CR compared to 0% in those in PR or with PD (p=0.01) (Figure 2). All patients either maintained a CR or achieved an improved haematological response following HDT and ASCT, with 89% of patients in CR at 6 months post ASCT. At the median follow up of 37 months, 78% were in CR and 22% had PD. At last follow up, there has been no documented amyloid recurrence in a cardiac allograft. There was no TRM noted in this study. All patients had cardiac rejection with 66% developing Grade 3A/2R rejection requiring methylprednisone. The most common infective complication was CMV reactivation (44%). Other infective complications included cryptococcal infection (11%), aspergillus and MAC infection (11%) and HSV reactivation requiring hospitalization (11%). During admission for HDT and ASCT, 89% had febrile neutropenia and there were no bleeding complications. Conclusions: We have demonstrated, in a prospective design, that sequential OHT/ASCT following induction therapy is safe in patients with Stage IIIa/b cardiac AL amyloidosis without an increase in TRM. This approach was associated with excellent survival outcomes compared with historical cohorts. Given the deep and prolonged responses seen with daratumumab based induction, a risk adapted strategy may be more appropriate moving forward, with only those not achieving a haematological CR undergoing consolidation ASCT following OHT.

A viral lncRNA tethers HSV-1 genomes at the nuclear periphery to establish viral latency.

Herpes simplex virus 1 (HSV-1) establishes lifelong latency in neuronal cells. Following a stressor, the virus reactivates from latency, virus is shed at the periphery and recurrent disease can occur. During latency, the viral lncRNA termed the latency-associated transcript (LAT) is known to accumulate to high abundance. The LAT is known to impact many aspects of latency though the molecular events involved are not well understood. Here, we utilized a human neuronal cell line model of HSV latency and reactivation (LUHMES) to identify the molecular-binding partners of the LAT during latency. We found that the LAT binds to both the cellular protein, TMEM43, and HSV-1 genomes in LUHMES cells. Additionally, we find that knockdown of TMEM43 prior to infection results in a decreased ability of HSV-1 to establish latency. This work highlights a potential mechanism for how the LAT facilitates the establishment of HSV-1 latency in human neurons.

HSV-2 Induced Cerebellitis: A Case Report of HSV-2 Reactivation by SARS-CoV-2 Infection

Background: Herpes simplex virus type 2 rarely causes encephalitis in humans. Some DNA viruses, such as HSV-1 and HSV-2, can be reactivated by COVID-19 infection. SARS-CoV-2 causes a wide spectrum of neurological deficits, such as stroke, delirium, movement disorders, and neuropathy. Case Presentation: An unusual manifestation of HSV-2 was diagnosed as cerebellitis in our patient. It was concluded that SARS-CoV-2 can reactivate DNA viruses, such as HSV-2. Here, we reported a 1-year-old female infant with cerebellitis due to herpes simplex virus type 2 infection. Conclusion: The patient was treated with intravenous acyclovir and oral prednisolone for three weeks. Finally, during her 9-month neurological follow-up, she was able to walk with minimal ataxia.

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.

Recurrent infection transiently expands human tissue T cells while maintaining long-term homeostasis.

Chronic viral infections are known to lead to T cell exhaustion or dysfunction. However, it remains unclear if antigen exposure episodes from periodic viral reactivation, such as herpes simplex virus type-2 (HSV-2) recrudescence, are sufficient to induce T cell dysfunction, particularly in the context of a tissue-specific localized, rather than a systemic, infection. We designed and implemented a stringent clinical surveillance protocol to longitudinally track both viral shedding and in situ tissue immune responses in a cohort of HSV+ volunteers that agreed to avoid using anti-viral therapy for the course of this study. Comparing lesion to control skin biopsies, we found that tissue T cells expanded immediately after reactivation, and then returned numerically and phenotypically to steady state. T cell responses appeared to be driven at least in part by migration of circulating T cells to the infected tissue. Our data indicate that tissue T cells are stably maintained in response to HSV reactivation, resembling a series of acute recall responses.

Investigating the Distinct Tissue Repair and Immunosuppressive Roles of Regulatory T cells in HSV-2 Infection

Abstract Herpes Simplex Virus 2 (HSV-2) is the primary cause of genital herpes, affecting 500 million people worldwide of which approximately 64% are women. Despite this disproportionately high burden, the female reproductive tract and its unique mucosal immune environment is surprisingly understudied. Tregs are necessary for CD4 +T cell priming in the draining lymph node (dLN), though their role in shaping tissue-resident memory T cell (T rm) responses during HSV-2 reactivation is unclear. Our preliminary data indicate that activated Tregs accumulate and persist in mouse vaginal tissue (VT) after above baseline out to at least 90 days post-infection (p.i.), thus implicating Tregs in memory recall responses to reinfection. We hypothesize that Tregs restrain robust T rmrecall responses to HSV-2 challenge. Additionally, we hypothesize that vaginal Tregs promote tissue healing in the VT in response to inflammatory alarmins through the expression of the epidermal growth factor ligand, amphiregulin (Areg). Female FoxP3 DTRmice were infected intravaginally with attenuated HSV-2, then systemically depleted of Tregs via intraperitoneal injection of diphtheria toxin and challenged with WT HSV-2 on day 30 p.i. Systemically Treg-depleted mice show increased activation and proliferation of T cells, and increased frequency of cytotoxic HSV-2-specific CD8 +T cells in the VT by day 3 post-challenge. Treg-depleted mice also have significantly higher pathology scores in H&amp;E-stained VT. We also report that VT Tregs from infected mice express more Areg than dLN Tregs via flow cytometry and single cell RNAseq. Ongoing work includes characterization of Areg expressing VT Tregs and further dissection of the T rmrecall responses in Treg-depleted mice. NIH (T32 AI07140, R01 AI141435)

HSV-1 Infection Among COVID-19 Cases with Ocular and Neurological Manifestations

Introduction: SARS-CoV-2 progression depends on multiple factors, including the compromised immune system and underlying diseases. HSV-1 reactivation in SARS-CoV-2 infection, more likely in patients with pneumonia and immunodeficiency, may be potentially life-threatening and implicate the prognosis. Case Presentation: We report two COVID-19 cases presenting ocular and neurological manifestations suspicious for HSV-1 encephalitis. Conclusions: Our study showed HSV-1 ocular manifestation among two COVID-19 cases. So, the recurrence of HSV-1 infection probably is related to immune responses during COVID-19 pathophysiology.

Cell-to-cell spread inhibiting antibodies constitute a correlate of protection against herpes simplex virus type 1 reactivations: A retrospective study.

Herpes simplex viruses (HSV) cause ubiquitous human infections. For vaccine development, knowledge concerning correlates of protection is essential. Therefore, we investigated (I) if humans are in principle capable producing cell-to-cell spread inhibiting antibodies against HSV and (II) whether this capacity is associated with a reduced HSV-1 reactivation risk. We established a high-throughput HSV-1-ΔgE-GFP reporter virus-based assay and evaluated 2,496 human plasma samples for HSV-1 glycoprotein E (gE) independent cell-to-cell spread inhibiting antibodies. Subsequently, we conducted a retrospective survey among the blood donors to analyze the correlation between the presence of cell-to-cell spread inhibiting antibodies in plasma and the frequency of HSV reactivations. In total, 128 of the 2,496 blood donors (5.1%) exhibited high levels of HSV-1 gE independent cell-to-cell spread inhibiting antibodies in the plasma. None of the 147 HSV-1 seronegative plasmas exhibited partial or complete cell-to-cell spread inhibition, demonstrating the specificity of our assay. Individuals with cell-to-cell spread inhibiting antibodies showed a significantly lower frequency of HSV reactivations compared to subjects without sufficient levels of such antibodies. This study contains two important findings: (I) upon natural HSV infection, some humans produce cell-to-cell spread inhibiting antibodies and (II) such antibodies correlate with protection against recurrent HSV-1. Moreover, these elite neutralizers may provide promising material for immunoglobulin therapy and information for the design of a protective vaccine against HSV-1.

HSV-1 LAT Promoter Deletion Viruses Exhibit Strain-Specific and LAT-Dependent Epigenetic Regulation of Latent Viral Genomes in Human Neurons.

Herpes simplex virus 1 (HSV-1) establishes latency in neurons and expresses long noncoding RNAs termed the latency-associated transcripts (LATs). Two previous studies using HSV-1 recombinants containing deletions in the LAT promoter revealed opposing effects of the promoter deletion regarding the heterochromatinization of latent viral genomes in mice ganglia. Confounding variables in these studies include viral strains utilized (17syn+ versus KOS), anatomical infection site (footpad versus eye) and infectious virus dose (500 versus 1 × 105 PFU), and to date the basis for the differences between the two studies remains unresolved. We recently reported that 17syn+ and KOS display distinct differences in heterochromatin levels during latency in human neurons. This raised the possibility that the discrepancy seen between the two previous studies could be explained by strain-specific differences within the LAT region. Here, we examine two recombinants containing orthologous 202 bp LAT promoter deletions, 17ΔPst and KOSΔPst, in a human neuronal model of latency and reactivation (LUHMES). We found that LUHMES neurons recapitulate previous observations in mice where deletion of the LAT promoter results in an increase in H3K27me3 deposition on the viral genome compared to the parental strain 17syn+ but a decrease compared to the parental strain KOS. We also found distinct strain-specific differences in the production of viral transcripts and proteins during latency. These results indicate that the function and/or regulation of the LATs differs between HSV-1 strains and may shed light on some discrepancies found in the literature when examining the function of the LATs. IMPORTANCE Herpes simplex virus 1 (HSV-1) establishes a lifelong infection in neuronal cells. Periodically, the virus reactivates from this latent state and causes recurrent disease. Mechanisms that control entry into and maintenance of latency are not well understood, though epigenetic posttranslational modification of histones associated with the viral genome are known to play an important role. During latency, the latency-associated transcript (LAT) is known to impact epigenetic marks, but the ultimate effect has been a point of controversy. Here, we utilize a human neuronal cell line model of HSV latency and reactivation (LUHMES) to characterize latency for two HSV-1 wild-type strains and their respective LAT promoter deletion viruses. We find that the LAT acts in a strain-specific manner to influence levels of chromatin marks, viral transcription, and viral protein production. This work highlights the need to account for strain-specific differences when characterizing the LAT's function and the dynamics of reactivation.