Selective Expression of CCR10 and CXCR3 by Circulating Human Herpes Simplex Virus-Specific CD8 T Cells

Deficiency of peripheral CLA+ Tregs and clinical relevance in Behcet's syndrome

BACKGROUND

Autoimmune responses have been suggested to involvement in patients with Behcet's syndrome (BS). There has been growing attention towards the roles of cutaneous lymphocyte antigen (CLA)+ regular T cells (Tregs) in autoimmune diseases. The role of CLA+ Tregs in BS is still uncertain. This study aims to clarify the impact of CLA+ Tregs on BS.

METHODS

We collected peripheral blood from a total of 107 patients with BS and 114 healthy controls (HCs). The number of CLA+ Tregs, natural killer (NK) cells, B cells, and several subtypes of CD4+ T cells were detected using flow cytometry and compared between patients and HCs.

RESULTS

The absolute number and proportion of CLA+ Tregs among CD4+ T lymphocytes and CD4+ Tregs were lower in patients with BS than in HCs. CLA+ Tregs were positively related with NK cells (r = 0.500, P < 0.001) and B cells (r = 0.470, P < 0.001) and negatively related with effector T cells (r=-0.402, P < 0.001) in patients with BS. Patients with BS and arterial aneurysms had CLA+ Treg cell deficiency. A decreased proportion of CLA+ Tregs was associated with arterial aneurysms in patients with BS. The proportion of CLA+ Tregs in patients with BS increased with corticosteroids and immunosuppressants.

CONCLUSION

CLA+ Tregs decrease in association with arterial aneurysm in patients with BS. CLA+ Tregs may be a predictor of response to BS treatment.

CLA+ memory T cells in atopic dermatitis

Circulating skin-homing cutaneous lymphocyte-associated antigen (CLA)+ T cells constitute a small subset of human memory T cells involved in several aspects of atopic dermatitis: Staphylococcus aureus related mechanisms, the abnormal Th2 immune response, biomarkers, clinical aspects of the patients, pruritus, and the mechanism of action of targeted therapies. Superantigens, IL-13, IL-31, pruritus, CCL17 and early effects on dupilumab-treated patients have in common that they are associated with the CLA+ T cell mechanisms in atopic dermatitis patients. The function of CLA+ T cells corresponds with the role of T cells belonging to the skin-associated lymphoid tissue and could be a reason why they reflect different mechanisms of atopic dermatitis and many other T cell mediated skin diseases. The goal of this review is to gather all this translational information of atopic dermatitis pathology.

HSV-2-Specific Human Female Reproductive Tract Tissue Resident Memory T Cells Recognize Diverse HSV Antigens

Antigen-specific TRM persist and protect against skin or female reproductive tract (FRT) HSV infection. As the pathogenesis of HSV differs between humans and model organisms, we focus on humans with well-characterized recurrent genital HSV-2 infection. Human CD8+ TRM persisting at sites of healed human HSV-2 lesions have an activated phenotype but it is unclear if TRM can be cultivated in vitro. We recovered HSV-specific TRM from genital skin and ectocervix biopsies, obtained after recovery from recurrent genital HSV-2, using ex vivo activation by viral antigen. Up to several percent of local T cells were HSV-reactive ex vivo. CD4 and CD8 T cell lines were up to 50% HSV-2-specific after sorting-based enrichment. CD8 TRM displayed HLA-restricted reactivity to specific HSV-2 peptides with high functional avidities. Reactivity to defined peptides persisted locally over several month and was quite subject-specific. CD4 TRM derived from biopsies, and from an extended set of cervical cytobrush specimens, also recognized diverse HSV-2 antigens and peptides. Overall we found that HSV-2-specific TRM are abundant in the FRT between episodes of recurrent genital herpes and maintain competency for expansion. Mucosal sites are accessible for clinical monitoring during immune interventions such as therapeutic vaccination.

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

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.

B cells, antibody-secreting cells, and virus-specific antibodies respond to herpes simplex virus 2 reactivation in skin

Tissue-based T cells are important effectors in the prevention and control of mucosal viral infections; less is known about tissue-based B cells. We demonstrate that B cells and antibody-secreting cells (ASCs) are present in inflammatory infiltrates in skin biopsy specimens from study participants during symptomatic herpes simplex virus 2 (HSV-2) reactivation and early healing. Both CD20+ B cells, most of which are antigen inexperienced based on their coexpression of IgD, and ASCs - characterized by dense IgG RNA expression in combination with CD138, IRF4, and Blimp-1 RNA - were found to colocalize with T cells. ASCs clustered with CD4+ T cells, suggesting the potential for crosstalk. HSV-2-specific antibodies to virus surface antigens were also present in tissue and increased in concentration during HSV-2 reactivation and healing, unlike in serum, where concentrations remained static over time. B cells, ASCs, and HSV-specific antibody were rarely detected in biopsies of unaffected skin. Evaluation of samples from serial biopsies demonstrated that B cells and ASCs followed a more migratory than resident pattern of infiltration in HSV-affected genital skin, in contrast to T cells. Together, these observations suggest the presence of distinct phenotypes of B cells in HSV-affected tissue; dissecting their role in reactivation may reveal new therapeutic avenues to control these infections.

BTLA-HVEM Checkpoint Axis Regulates Hepatic Homeostasis and Inflammation in a ConA-Induced Hepatitis Model in Zebrafish

The BTLA-HVEM checkpoint axis plays extensive roles in immunomodulation and diseases, including cancer and autoimmune disorders. However, the functions of this checkpoint axis in hepatitis remain limited. In this study, we explored the regulatory role of the Btla-Hvem axis in a ConA-induced hepatitis model in zebrafish. Results showed that Btla and Hvem were differentially expressed on intrahepatic Cd8⁺ T cells and hepatocytes. Knockdown of Btla or Hvem significantly promoted hepatic inflammation. Btla was highly expressed in Cd8⁺ T cells in healthy liver but was downregulated in inflamed liver, as evidenced by a disparate proportion of Cd8⁺Btla⁺ and Cd8⁺Btla^- T cells in individuals without or with ConA stimulation. Cd8⁺Btla⁺ T cells showed minimal cytotoxicity to hepatocytes, whereas Cd8⁺Btla^- T cells were strongly reactive. The depletion of Cd8⁺Btla^- T cells reduced hepatitis, whereas their transfer enhanced hepatic inflammation. These observations indicate that Btla endowed Cd8⁺Btla⁺ T cells with self-tolerance, thereby preventing them from attacking hepatocytes. Btla downregulation deprived this tolerization. Mechanistically, Btla-Hvem interaction contributed to Cd8⁺Btla⁺ T cell tolerization, which was impaired by Hvem knockdown but rescued by soluble Hvem protein administration. Notably, Light was markedly upregulated on Cd8⁺Btla^- T cells, accompanied by the transition of Cd8⁺Btla⁺Light^- to Cd8⁺Btla^-Light⁺ T cells during hepatitis, which could be modulated by Cd4⁺ T cells. Light blockade attenuated hepatitis, thereby suggesting the positive role of Light in hepatic inflammation. These findings provide insights into a previously unrecognized Btla-Hvem-Light regulatory network in hepatic homeostasis and inflammation, thus adding a new potential therapeutic intervention for hepatitis.

Herpes Simplex Virus Type 2 Infection-Induced Expression of CXCR3 Ligands Promotes CD4+ T Cell Migration and Is Regulated by the Viral Immediate-Early Protein ICP4

HSV-2 infection-induced CXCR3 ligands are important for the recruitment of virus-specific CD8⁺ T cells, but their impact on CD4⁺ T cell trafficking remains to be further determined. Given that recruitment of CD4⁺ T cells to infection areas may be one of the mechanisms that account for HSV-2 infection-mediated enhancement of HIV-1 sexual transmission, here we investigated the functionality of HSV-2 infection-induced CXCR3 ligands CXCL9, CXCL10, and CXCL11 in vivo and in vitro, and determined the viral components responsive for such induction and the underlying mechanisms. We first found that the expression of CXCR3 ligands CXCL9, CXCL10, and CXCL11 was increased in mice following vaginal challenge with HSV-2, while CXCL9 played a predominant role in the recruitment of CD4⁺ T cells to the vaginal foci of infected mice. HSV-2 infection also induced the production of CXCL9, CXCL10, and CXCL11 in human cervical epithelial cells. Of note, although HSV-2 induced the expression of all the three CXCR3 ligands, the induced CXCL9 appeared to play a predominant role in promoting CD4⁺ T cell migration, reflecting that the concentrations of CXCL10 and CXCL11 required for CD4⁺ T cell migration are higher than that of CXCL9. We further revealed that, ICP4, an immediate-early protein of HSV-2, is crucial in promoting CXCR3 ligand expression through the activation of p38 MAPK pathway. Mechanistically, ICP4 binds to corresponding promoters of CXCR3 ligands via interacting with the TATA binding protein (TBP), resulting in the transcriptional activation of the corresponding promoters. Taken together, our study highlights HSV-2 ICP4 as a vital viral protein in promoting CXCR3 ligand expression and CXCL9 as the key induced chemokine in mediating CD4⁺ T cell migration. Findings in this study have shed light on HSV-2 induced leukocyte recruitment which may be important for understanding HSV-2 infection-enhanced HIV-1 sexual transmission and the development of intervention strategies.

The Role of CXCR3 and Its Chemokine Ligands in Skin Disease and Cancer

Chemokines and their receptors play an important role in the recruitment, activation and differentiation of immune cells. The chemokine receptor, CXCR3, and its ligands, CXCL9, CXCL10, and CXCL11 are key immune chemoattractants during interferon-induced inflammatory responses. Inflammation of the skin resulting from infections or autoimmune disease drives expression of CXCL9/10/11 and the subsequent recruitment of effector, CXCR3⁺ T cells from the circulation. The relative contributions of the different CXCR3 chemokines and the three variant isoforms of CXCR3 (CXCR3A, CXCR3B, CXCR3alt) to the inflammatory process in human skin requires further investigation. In skin cancers, the CXCR3 receptor can play a dual role whereby expression on tumor cells can lead to cancer metastasis to systemic sites while receptor expression on immune cells can frequently promote anti-tumor immune responses. This review will discuss the biology of CXCR3 and its associated ligands with particular emphasis on the skin during inflammation and carcinogenesis.