Local Immune Responses to Herpes Simplex Virus

Editors

Haina Shin

Washington University in St. Louis

Smita Gopinath

School of Public Health, Harvard University

Joshua Tisdell Schiffer

Fred Hutchinson Cancer Center

Impact

Review

15 September 2021

Local Immune Control of Latent Herpes Simplex Virus Type 1 in Ganglia of Mice and Man

Anthony J. St. Leger

, 2 more and

Georges Michel G. M. Verjans

Herpes simplex virus type 1 (HSV-1) is a prevalent human pathogen. HSV-1 genomes persist in trigeminal ganglia neuronal nuclei as chromatinized episomes, while epithelial cells are typically killed by lytic infection. Fluctuations in anti-viral responses, broadly defined, may underlay periodic reactivations. The ganglionic immune response to HSV-1 infection includes cell-intrinsic responses in neurons, innate sensing by several cell types, and the infiltration and persistence of antigen-specific T-cells. The mechanisms specifying the contrasting fates of HSV-1 in neurons and epithelial cells may include differential genome silencing and chromatinization, dictated by variation in access of immune modulating viral tegument proteins to the cell body, and protection of neurons by autophagy. Innate responses have the capacity of recruiting additional immune cells and paracrine activity on parenchymal cells, for example via chemokines and type I interferons. In both mice and humans, HSV-1-specific CD8 and CD4 T-cells are recruited to ganglia, with mechanistic studies suggesting active roles in immune surveillance and control of reactivation. In this review we focus mainly on HSV-1 and the TG, comparing and contrasting where possible observational, interventional, and in vitro studies between humans and animal hosts.

8,395 views

18 citations

Original Research

04 January 2022

Endogenous Retroviruses Provide Protection Against Vaginal HSV-2 Disease

Radeesha Jayewickreme

, 11 more and

Maria Tokuyama

7,452 views

3 citations

(A) Evaluation of IFN-γ effect on HSV immediate early (IE) gene transcription via RNA FISH. In situ detection and visualization of IE gene expression using pooled probes specific to each of the five IE genes. Primary human keratinocytes 6 h.p.i. with K26 (MOI=1) either mock-treated or pretreated with IFN-γ (10 U/ml or 100 U/ml). Scale bar, 50 µm. (B) Quantitative assessment of IFN-γ-mediated reduction of IE gene expression via qRT-PCR. Primary human fibroblasts infected with wildtype strain KOS, MOI=1, 4 h.p.i. Mock treated compared to IFN-γ treated, 100 U/ml. (C) IFN-γ effect on HSV gene transcription (ICP27, ICP8, and glycoprotein B) in the presence or absence of interferon blockers, GIR208 and B18R. Primary human keratinocytes infected with KOS, MOI=1, 4 h.p.i. (D) Time-dependent inhibition by IFN-γ. Percentage of GFP-expressing cells in K26-infected primary human keratinocytes 16 h.p.i. (MOI=1) with IFN-γ treatment initiated at 2, 4, 8, 16, 24, or 48 hours prior to infection. (E, F) Dose-dependent inhibition by IFN-γ. GFP expression (E) and viral DNA replication (F) under increasing dosage of IFN-γ in K26-infected keratinocytes. MOI=1, 16 h.p.i. HSV genome DNA were quantified by qPCR and compared between 2 and 16 h.p.i. (G) Growth kinetics of strain KOS under low and high MOI in primary human fibroblasts with (100 U/ml) or without IFN-γ. (H) Responsiveness to IFN-γ in IFI16 knockout and Cas9 control human fibroblasts. Immunoblot of whole-cell lysate from IFI16 knockout and Cas9 control cells mock-treated or pretreated with IFN-γ (500U/mL) for 20 hours. One of three biological replicates is shown. (I) Viral yield 12 h.p.i. following wildtype HSV-2 strain 186 infection (MOI=0.1) of IFI16 knockout and Cas9 control fibroblasts mock-treated or pretreated with IFN-γ (500U/mL) for 20 hours. Two-way ANOVA with Holm-Sidak’s multiple comparisons test. Values are mean ± S.D. (error bars), from three independent experiments.

Original Research

06 September 2021

Tissue-Resident-Memory CD8+ T Cells Bridge Innate Immune Responses in Neighboring Epithelial Cells to Control Human Genital Herpes

Tao Peng

, 20 more and

Jia Zhu

Tissue-resident-memory T cells (TRM) populate the body’s barrier surfaces, functioning as frontline responders against reencountered pathogens. Understanding of the mechanisms by which CD8TRM achieve effective immune protection remains incomplete in a naturally recurring human disease. Using laser capture microdissection and transcriptional profiling, we investigate the impact of CD8TRM on the tissue microenvironment in skin biopsies sequentially obtained from a clinical cohort of diverse disease expression during herpes simplex virus 2 (HSV-2) reactivation. Epithelial cells neighboring CD8TRM display elevated and widespread innate and cell-intrinsic antiviral signature expression, largely related to IFNG expression. Detailed evaluation via T-cell receptor reconstruction confirms that CD8TRM recognize viral-infected cells at the specific HSV-2 peptide/HLA level. The hierarchical pattern of core IFN-γ signature expression is well-conserved in normal human skin across various anatomic sites, while elevation of IFI16, TRIM 22, IFITM2, IFITM3, MX1, MX2, STAT1, IRF7, ISG15, IFI44, CXCL10 and CCL5 expression is associated with HSV-2-affected asymptomatic tissue. In primary human cells, IFN-γ pretreatment reduces gene transcription at the immediate-early stage of virus lifecycle, enhances IFI16 restriction of wild-type HSV-2 replication and renders favorable kinetics for host protection. Thus, the adaptive immune response through antigen-specific recognition instructs innate and cell-intrinsic antiviral machinery to control herpes reactivation, a reversal of the canonical thinking of innate activating adaptive immunity in primary infection. Communication from CD8TRM to surrounding epithelial cells to activate broad innate resistance might be critical in restraining various viral diseases.

9,282 views

21 citations

Original Research

30 August 2021

Fas/FasL Contributes to HSV-1 Brain Infection and Neuroinflammation

Malgorzata Krzyzowska

, 3 more and

Kristina Eriksson

Cell counts for CD4+ T cells, CD8+ T cells and NK cells were measured by flow cytometry in brains (A) and trigeminal ganglia (B) of mice uninfected and infected with HSV-1 at 8 d p.i. Data were presented as mean ± SEM, N = 8. Data analysis was performed by comparing Fas-deficient (lpr) and FasL-deficient (gld) groups with wild-type (C57BL/6) mice. **p ≤ 0.001, *p ≤ 0.05. (C) HSV-1 specific CD8+ T cells (SSIEFARL+) in brains and ganglia of wild-type, lpr and gld mice measured by flow cytometry. Data were presented as mean ± SEM, N = 8. Data analysis was performed by comparing lpr and gld groups with wild-type (C57BL/6) mice. P ≤ 0.05. (D) Numbers of T cells (CD4+ and CD8+) positive for active form of caspase-3 in brains of wild-type, lpr and gld mice at 8 dp.i. Data were presented as mean ± SEM, N = 8. Data analysis was performed by comparing lpr and gld groups with wild-type (C57BL/6) mice and between control and uninfected groups. **indicates P ≤ 0.001, while *P ≤ 0.05 compared to wild-type mice; #indicates P ≤ 0.001, ##indicates P < 0.05, in pairs control – infected.

The Fas/FasL pathway plays a key role in immune homeostasis and immune surveillance. In the central nervous system (CNS) Fas/FasL is involved in axonal outgrowth and adult neurogenesis. However, little is known about the role of the Fas/FasL pathway in herpes encephalitis. In this study, we used a neuropathogenic clinical strain of herpes simplex virus type 1 (HSV-1) to explore infection-induced inflammation and immune responses in the mouse brain and the role of Fas/FasL in antiviral CNS immunity. HSV-1 CNS infection induced the infiltration of Fas- FasL-bearing monocytes and T cells in the brain and also to an up-regulation of Fas and FasL expression on resident astrocytes and microglia within infected sites. Upon infection, Fas- and FasL-deficient mice (lpr and gld) were partially protected from encephalitis with a decreased morbidity and mortality compared to WT mice. Fas/FasL deficiency promoted cell-mediated immunity within the CNS. Fas receptor stimulation abrogated HSV-1 induced activation and inflammatory reactions in microglia from WT mice, while lack of Fas or FasL led to a more pronounced activation of monocytes and microglia and also to an enhanced differentiation of these cells into a pro-inflammatory M1 phenotype. Furthermore, the specific immune system was more efficient in Fas- and FasL-deficient mice with significantly higher numbers of infiltrating HSV-1-specific cytotoxic T cells in the brain. Our data indicate that the Fas/FasL pathway leads to excessive neuroinflammation during HSV-1 infection, which is associated with a diminished anti-viral response and an excessive neuroinflammation.

4,119 views

20 citations

Type I and III IFNs directly suppress HSV-2 replication in the genital mucosa. Concurrently, type I IFN signaling promotes IM recruitment and production of IL-18. This in turns stimulates NK cell IFN-γ production. Type I IFNs stimulate adaptive immunity both directly and indirectly through IM differentiation into APCs, maturation of DCs, and inducing CD4+ T cell expansion. Type I IFNs can both promote neutrophil function, and negatively regulate innate immune responses to prevent immune-mediated pathology by suppressing neutrophil recruitment and limiting IFN-γ production by NK cells. IFN-γ production, highly dependent on type I IFN signaling, promotes IgG2 antibody production, M1 macrophage polarisation and DC maturation, which will promote CD4+ memory T cell retention via production of CCL4 and CXCL9. Type III IFNs, similar to type I IFNs, have also been shown to suppress neutrophil activity and monocyte-mediated NK cell activation, but this is not yet demonstrated in the vaginal mucosa.

Review

18 August 2021

Immunoregulatory Functions of Interferons During Genital HSV-2 Infection

Emily Feng

, 2 more and

Ali A. Ashkar

7,404 views

8 citations