Identification of varicella-zoster virus-specific CD8 T cells in patients after T-cell-depleted allogeneic stem cell transplantation

Increased frequency of HLA-A*02 in patients with atherosclerosis is associated with VZV seropositivity

BACKGROUND

HLA molecules are inherited key molecules in the immune inflammation and specific responses to environmental pathogens. We investigated the association of HLA-A alleles with Varicella zoster virus (VZV) seropositivity in patients with atherosclerosis (AS).

MATERIALS AND METHODS

Plasma Anti-VZV IgG and molecular HLA type were detected in 203 (100 AS⁺ and 103 AS^-) individuals.

RESULTS

Of 100 AS⁺ individuals, 66 were anti-VZV⁺ and 34 were anti-VZV^-. Of 103 age/sex-matched AS^- individuals, 59 were anti-VZV⁺ and 44 were anti-VZV^-. Anti-VZV-IgG in AS⁺ cases was higher than AS^- controls (p = .034). The mean anti-VZV IgG in HLA-A*02⁺AS⁺ individuals was higher than HLA-A*02⁺AS^- controls (p < .001). HLA-A*02 was associated with VZV-seropositivity (p = .01) in AS⁺ patients. A higher frequency of HLA-A*02-allele in AS⁺ patients compared to AS^- controls (p = .015) and an accumulation of HLA-A*02-allele in AS⁺ anti-VZV⁺ group (33.3%, p = .004) was observed.

CONCLUSIONS

HLA-A alleles and immune responses to VZV are associated with clinical atherosclerosis.

Antigen-shift in varicella-zoster virus-specific T-cell immunity over the course of Fingolimod-treatment in relapse-remitting multiple sclerosis patients

BACKGROUND

Fingolimod (FTY) applied as treatment regimen of relapsing-remitting multiple sclerosis (RRMS) induces downregulation of sphingosine-1-phosphate receptors on the lymphocytes. As a result CC chemokine receptor type 7 (CCR7) expressing lymphocytes are retained within the peripheral lymph nodes thus suppressing their accumulation into the cerebrospinal fluid of multiple sclerosis (MS) patients and hampering disease progress. Unfortunately, MS patients treated with FTY suffer from an increased incidence of varicella-zoster virus (VZV) infections which has been associated with a decrease of VZV immediate early 63 (IE63)-specific T-cell immunity. To elucidate VZV-specific T-cell immunity over the course of FTY-treatment, we analyzed T-cell immunity for immediate early, early and late VZV-antigens.

METHODS

T-cell immune responses were detected via intracellular IFN-γ staining after stimulation with VZV-specific peptide mixes for IE62 and IE63 and recombinant proteins for open reading frame 26 (ORF26), ORF9 and glycoprotein E (gE) using flow cytometry. Analyzed samples comprised of different groups including 18 patients with RRMS at baseline (BL), 6 and 12 months after FTY-treatment start, 12 patients with long-term (LT) FTY-treatment, one FTY-treated patient, before and after VZV-reactivation. In addition, VZV-specific IgG and IgM titers were assessed by ELISA.

RESULTS

After FTY-treatment start, absolute numbers of CCR7 expressing CD4⁺ T cells and CD8⁺T cells dropped rapidly. However, VZV-specific immunity could be detected in the majority of RRMS patients throughout FTY-treatment with increasing prevalence after 6 months of treatment. We found an increase in the prevalence of VZV-specific IFN-γ⁺CD8⁺ T-cell immunity in FTY-treated patients after six months of therapy, while in parallel VZV-specific IFN-γ⁺CD4⁺ T cells declined dramatically. Additionally, a strong correlation between VZV-specific IgG serum titers and the percentage of RRMS patients with detectable VZV-specific T cells was observed (r = 0.985). Most remarkably, FTY-treated RRMS patients presented a shift in the predominant CD8⁺ T cell-mediated antigen-response from immediate early (IE62) to early virus antigens (ORF26) six months after treatment in parallel to a decrease of VZV-specific CD4⁺ T-cell immunity. ORF26-specific CD8⁺ T cells still dominated the VZV-specific cellular immunity at month 12 after FTY-treatment start and in LT FTY-treated MS patients. In a RRMS patient an increase of VZV-specific CD4⁺ T cells at VZV-reactivation accompanied with a four-fold increase of a VZV-specific IgG titer was detected which might indicate an important role in cellular immune control of VZV-infections.

CONCLUSION

Monitoring VZV-specific T-cell immunity might provide a valuable tool to RRMS patient risk management during FTY-treatment.

Understanding the immunology of the Zostavax shingles vaccine

Zostavax is a live-attenuated varicella zoster virus (VZV) vaccine recommended for use in adults >50 years of age to prevent shingles. The main risk factor for the development of shingles is age, which correlates with decreasing cell-mediated immunity. These data suggest a predominant role of T cell immunity in controlling VZV latency. However, other components of the immune system may also contribute. In this review, we will discuss how the immune system responds to Zostavax, focusing on recent studies examining innate immunity, transcriptomics, metabolomics, cellular, and humoral immunity.

Increased herpes zoster risk associated with poor HLA-A immediate early 62 protein (IE62) affinity

Around 30% of individuals will develop herpes zoster (HZ), caused by the varicella zoster virus (VZV), during their life. While several risk factors for HZ, such as immunosuppressive therapy, are well known, the genetic and molecular components that determine the risk of otherwise healthy individuals to develop HZ are still poorly understood. We created a computational model for the Human Leukocyte Antigen (HLA-A, -B, and -C) presentation capacity of peptides derived from the VZV Immediate Early 62 (IE62) protein. This model could then be applied to a HZ cohort with known HLA molecules. We found that HLA-A molecules with poor VZV IE62 presentation capabilities were more common in a cohort of 50 individuals with a history of HZ compared to a nationwide control group, which equated to a HZ risk increase of 60%. This tendency was most pronounced for cases of HZ at a young age, where other risk factors are less prevalent. These findings provide new molecular insights into the development of HZ and reveal a genetic predisposition in those individuals most at risk to develop HZ.

Herpes zoster in kidney transplant recipients: protective effect of anti-cytomegalovirus prophylaxis and natural killer cell count. A single-center cohort study

Despite its impact on quality of life and potential for complications, specific risk and protective factors for herpes zoster (HZ) after kidney transplantation (KT) remain to be clarified. We included 444 patients undergoing KT between November 2008 and March 2013. Peripheral blood lymphocyte subpopulations were measured at baseline and months 1 and 6. The risk factors for early (first post-transplant year) and late HZ (years 1-5) were separately assessed. We observed 35 episodes of post-transplant HZ after a median follow-up of 48.3 months (incidence rate: 0.057 per 1000 transplant-days). Median interval from transplantation was 18.3 months. Six patients (17.1%) developed disseminated infection. Postherpetic neuralgia occurred in 10 cases (28.6%). The receipt of anti-cytomegalovirus (CMV) prophylaxis with (val)ganciclovir decreased the risk of early HZ [adjusted hazard ratio (aHR): 0.08; 95% CI: 0.01-1.13; P-value = 0.062], whereas the natural killer (NK) cell at month 6 was protective for the occurrence of late HZ [aHR (per 10-cells/μl increase): 0.94; 95% CI: 0.88-1.00; P-value = 0.054]. In conclusion, two easily ascertainable factors (whether the patient is receiving anti-CMV prophylaxis and the NK cell count at month 6) might be potentially useful to tailor preventive strategies according to individual susceptibility to post-transplant HZ.

Allo-HLA Cross-Reactivities of Cytomegalovirus-, Influenza-, and Varicella Zoster Virus-Specific Memory T Cells Are Shared by Different Healthy Individuals

Virus-specific T cells can recognize allogeneic HLA (allo-HLA) through TCR cross-reactivity. The allospecificity often differs by individual (private cross-reactivity) but also can be shared by multiple individuals (public cross-reactivity); however, only a few examples of the latter have been described. Because these could facilitate alloreactivity prediction in transplantation, we aimed to identify novel public cross-reactivities of human virus-specific CD8⁺ T cells directed against allo-HLA by assessing their reactivity in mixed-lymphocyte reactions. Further characterization was done by studying TCR usage with primer-based DNA sequencing, cytokine production with ELISAs, and cytotoxicity with ⁵¹ chromium-release assays. We identified three novel public allo-HLA cross-reactivities of human virus-specific CD8⁺ T cells. CMV B35/IPS CD8⁺ T cells cross-reacted with HLA-B51 and/or HLA-B58/B57 (23% of tetramer-positive individuals), FLU A2/GIL (influenza IMP[58-66] HLA-A*02:01/GILGFVFTL) CD8⁺ T cells with HLA-B38 (90% of tetramer-positive individuals), and VZV A2/ALW (varicella zoster virus IE62[593-601] HLA-A*02:01/ALWALPHAA) CD8⁺ T cells with HLA-B55 (two unrelated individuals). Cross-reactivity was tested against different cell types including endothelial and epithelial cells. All cross-reactive T cells expressed a memory phenotype, emphasizing the importance for transplantation. We conclude that public allo-HLA cross-reactivity of virus-specific memory T cells is not uncommon and may create novel opportunities for alloreactivity prediction and risk estimation in transplantation.

Varicella-Zoster Virus-Specific Cellular Immune Responses to the Live Attenuated Zoster Vaccine in Young and Older Adults

The incidence and severity of herpes zoster (HZ) increases with age. The live attenuated zoster vaccine generates immune responses similar to HZ. We compared the immune responses to zoster vaccine in young and older to adults to increase our understanding of the immune characteristics that may contribute to the increased susceptibility to HZ in older adults. Young (25-40 y; n = 25) and older (60-80 y; n = 33) adults had similar magnitude memory responses to varicella-zoster virus (VZV) ex vivo restimulation measured by responder cell-frequency and flow cytometry, but the responses were delayed in older compared with young adults. Only young adults had an increase in dual-function VZV-specific CD4⁺ and CD8⁺ T cell effectors defined by coexpression of IFN-γ, IL-2, and CD107a after vaccination. In contrast, older adults showed marginal increases in VZV-specific CD8⁺CD57⁺ senescent T cells after vaccination, which were already higher than those of young adults before vaccination. An increase in VZV-stimulated CD4⁺CD69⁺CD57⁺PD1⁺ and CD8⁺CD69⁺CD57⁺PD1⁺ T cells from baseline to postvaccination was associated with concurrent decreased VZV-memory and CD8⁺ effector responses, respectively, in older adults. Blocking the PD1 pathway during ex vivo VZV restimulation increased the CD4⁺ and CD8⁺ proliferation, but not the effector cytokine production, which modestly increased with TIM-3 blockade. We conclude that high proportions of senescent and exhausted VZV-specific T cells in the older adults contribute to their poor effector responses to a VZV challenge. This may underlie their inability to contain VZV reactivation and prevent the development of HZ.

Metabolic Phenotypes of Response to Vaccination in Humans

Herpes zoster (shingles) causes significant morbidity in immune compromised hosts and older adults. Whereas a vaccine is available for prevention of shingles, its efficacy declines with age. To help to understand the mechanisms driving vaccinal responses, we constructed a multiscale, multifactorial response network (MMRN) of immunity in healthy young and older adults immunized with the live attenuated shingles vaccine Zostavax. Vaccination induces robust antigen-specific antibody, plasmablasts, and CD4⁺ T cells yet limited CD8⁺ T cell and antiviral responses. The MMRN reveals striking associations between orthogonal datasets, such as transcriptomic and metabolomics signatures, cell populations, and cytokine levels, and identifies immune and metabolic correlates of vaccine immunity. Networks associated with inositol phosphate, glycerophospholipids, and sterol metabolism are tightly coupled with immunity. Critically, the sterol regulatory binding protein 1 and its targets are key integrators of antibody and T follicular cell responses. Our approach is broadly applicable to study human immunity and can help to identify predictors of efficacy as well as mechanisms controlling immunity to vaccination.

Immunological evasion of immediate-early varicella zoster virus proteins

The varicella zoster virus (VZV) causes the childhood disease commonly known as chickenpox and can later in life reactivate as herpes zoster. The adaptive immune system is known to play an important role in suppressing VZV reactivation. A central aspect of this system is the presentation of VZV-derived peptides by the major histocompatibility complex (MHC) proteins. Here, we investigate if key VZV proteins have evolved their amino acid sequence to avoid presentation by MHC based on predictive models of MHC-peptide affinity. This study shows that the immediate-early proteins of all characterized VZV strains are profoundly depleted for high-affinity MHC-I-restricted epitopes. The same depletion can be found in its closest animal analog, the simian varicella virus. Further orthology analysis towards other herpes viruses suggests that the protein amino acid frequency is one of the primary drivers of targeted epitope depletion.

Preliminary exploration of HLA-A 1101-restricted human cytomegalovirus glycoprotein B-specific CD8⁺ T cells in allogeneic stem-cell transplant recipients

T-cell responses directed against human cytomegalovirus (HCMV) glycoprotein B (gB) contribute to protective immunity against HCMV infection in both animal models and humans. However, the gB-specific human CD8(+) T cell responses remain poorly understood. gB antigen-specific CD8(+) T cells were stained with seven major histocompatibility complex (MHC)-peptide pentamers in 16 human leukocyte antigen (HLA)-A 1101-positive, HCMV-seropositive patients following hematopoietic stem cell transplantation (HSCT). Of these seven pentamers, the most frequent CD8(+) T-cell responses were directed against the gB332-340 peptide. These gB332-340-specific CD8(+) T cells were strongly associated with the presence of plasma HCMV immunoglobulin M in all HSCT recipients and exhibited a probable causal relationship with the level of pp65 antigenemia. Together, these data suggest a role for gB332-340-specific CD8(+) T cells in HCMV reactivation after HSCT. Furthermore, the pentamer assay may be valuable in detecting antigen-specific CD8(+) T cells.

T-cell immunity to human alphaherpesviruses

Human alphaherpesviruses (αHHV) - herpes simplex virus type 1 (HSV-1), HSV-2, and varicella-zoster virus (VZV) - infect mucosal epithelial cells, establish a lifelong latent infection of sensory neurons, and reactivate intermittingly to cause recrudescent disease. Although chronic αHHV infections co-exist with brisk T-cell responses, T-cell immune suppression is associated with worsened recurrent infection. Induction of αHHV-specific T-cell immunity is complex and results in poly-specific CD4 and CD8 T-cell responses in peripheral blood. Specific T-cells are localized to ganglia during the chronic phase of HSV infection and to several infected areas during recurrences, and persist long after viral clearance. These recent advances hold promise in the design of new vaccine candidates.

Persistence and antiviral resistance of varicella zoster virus in hematological patients

BACKGROUND

Varicella zoster virus (VZV) infections are a relevant cause of morbidity and mortality in hematological patients and especially in hematopoietic stem cell transplant (HSCT) recipients. The present study aimed to investigate the prevalence and clinical significance of viral persistence and antiviral resistance by systematically analyzing all episodes of VZV diagnosed in our laboratory in pediatric and adult hematological patients between 2007 and 2010.

METHODS

Patient charts were reviewed to document patient and disease characteristics. VZV loads were determined in all available clinical samples from the day of diagnosis and thereafter. Persistent VZV infection was defined as a VZV infection that lasted at least 7 days. Analysis of resistance was performed in all patients with persistent VZV infection by sequence analysis of viral thymidine kinase and DNA polymerase genes.

RESULTS

In total, 89 episodes occurred in 87 patients, of whom 65 were recipients of an allogeneic HSCT. Follow-up samples were available in 54 episodes. Persistent VZV was demonstrated in 32 of these episodes (59%). Complications occurred in 16 of the persistent episodes (50%) vs 2 of 22 nonpersistent episodes (9%). Mutations possibly associated with resistance were found in 27% of patients with persistent VZV, including patients with treatment-unresponsive dermatomal zoster that progressed to severe retinal or cerebral infection.

CONCLUSIONS

In hematological patients, VZV-related complications occur frequently, especially in persistent infections. Antiviral resistance is a relevant factor in persistent infections and needs to be investigated in various affected body sites, especially when clinical suspicion of treatment failure arises.

Vaccine-induced allo-HLA-reactive memory T cells in a kidney transplantation candidate

BACKGROUND

Allo-human leukocyte antigen (HLA) reactivity by naturally acquired viral-specific memory T cells is common. However, the effect of successful vaccination on the alloreactive memory T-cell repertoire is unclear. We hypothesized that vaccination could specifically induce allo-HLA-reactive memory T cells.

METHODS

A varicella-zoster virus (VZV) immediate early 62 (IE62)-specific CD8 memory T-cell clone was single cell sorted from a VZV seronegative renal transplant candidate after response to live attenuated varicella vaccination. To analyze the allo-HLA reactivity, the VZV IE62-specific T-cell clone was tested against HLA-typed target cells and target cells transfected with HLA molecules, in both cytokine production and cytotoxicity assays.

RESULTS

The varicella vaccine-induced VZV IE62-specific T-cell clone specifically produced interferon-γ when stimulated with HLA-B*55:01-expressing Epstein-Barr virus-transformed B cells and HLA-B*55:01-transfected K562 cells (single HLA antigen expressing cell line [SALs]) only. The clone also demonstrated specific cytolytic effector function against HLA-B*55:01 SALs and phytohemagglutinin blasts. Cytotoxicity assays using proximal tubular epithelial cell and human umbilical vein endothelial cell targets confirmed the kidney tissue specificity of the allo-HLA-B*55:01 reactivity, and the relevance of the cross-reactivity to clinical kidney transplantation. The results also suggest that molecular mimicry, and not bystander proliferation, is the mechanism underlying vaccine-induced alloreactivity.

CONCLUSIONS

Varicella vaccination generated a de novo alloreactive kidney cell-specific cytolytic effector memory T cell in a patient awaiting renal transplantation. Vaccination-induced alloreactivity may have important clinical implications, especially for vaccine timing and recipient monitoring.