Attenuated effector T cells are linked to control of chronic HBV infection.

Hepatitis B virus (HBV)-specific CD8+ T cells play a dominant role during acute-resolving HBV infection but are functionally impaired during chronic HBV infection in humans. These functional deficits have been linked with metabolic and phenotypic heterogeneity, but it has remained unclear to what extent different subsets of HBV-specific CD8+ T cells still suppress viral replication. We addressed this issue by deep profiling, functional testing and perturbation of HBV-specific CD8+ T cells during different phases of chronic HBV infection. Our data revealed a mechanism of effector CD8+ T cell attenuation that emerges alongside classical CD8+ T cell exhaustion. Attenuated HBV-specific CD8+ T cells were characterized by cytotoxic properties and a dampened effector differentiation program, determined by antigen recognition and TGFß signaling, and were associated with viral control during chronic HBV infection. These observations identify a distinct subset of CD8+ T cells linked with immune efficacy in the context of a chronic human viral infection with immunotherapeutic potential.

A novel HLA-DPB1 allele, HLA-DPB1*1447:01, identified by next-generation sequencing.

HLA-DPB1*1447:01 differs from HLA-DPB1*04:01:01 by a single nucleotide in exon 2 from A to C at position 134.

Next-generation sequencing reveals a novel HLA-C allele, HLA-C*15:255.

HLA-C*15:255 differs from HLA-C*15:02:01 by five nucleotide substitutions located in exons 4 and 5.

Boosting compromised SARS-CoV-2-specific immunity with mRNA vaccination in liver transplant recipients.

BACKGROUND & AIMS: Liver transplant recipients (LTRs) demonstrate a reduced response to COVID-19 mRNA vaccination; however, a detailed understanding of the interplay between humoral and cellular immunity, especially after a third (and fourth) vaccine dose, is lacking. METHODS: We longitudinally compared the humoral, as well as CD4+ and CD8+ T-cell, responses between LTRs (n = 24) and healthy controls (n = 19) after three (LTRs: n = 9 to 16; healthy controls: n = 9 to 14 per experiment) to four (LTRs: n = 4; healthy controls: n = 4) vaccine doses, including in-depth phenotypical and functional characterization. RESULTS: Compared to healthy controls, development of high antibody titers required a third vaccine dose in most LTRs, while spike-specific CD8+ T cells with robust recall capacity plateaued after the second vaccine dose, albeit with a reduced frequency and epitope repertoire compared to healthy controls. This overall attenuated vaccine response was linked to a reduced frequency of spike-reactive follicular T helper cells in LTRs. CONCLUSION: Three doses of a COVID-19 mRNA vaccine induce an overall robust humoral and cellular memory response in most LTRs. Decisions regarding additional booster doses may thus be based on individual vaccine responses as well as evolution of novel variants of concern. IMPACT AND IMPLICATIONS: Due to immunosuppressive medication, liver transplant recipients (LTR) display reduced antibody titers upon COVID-19 mRNA vaccination, but the impact on long-term immune memory is not clear. Herein, we demonstrate that after three vaccine doses, the majority of LTRs not only exhibit substantial antibody titers, but also a robust memory T-cell response. Additional booster vaccine doses may be of special benefit for a small subset of LTRs with inferior vaccine response and may provide superior protection against evolving novel viral variants. These findings will help physicians to guide LTRs regarding the benefit of booster vaccinations.

A novel null-allele, HLA-B*35:574N, containing a mutation in the start-codon.

HLA-B*35:574N contains a single nucleotide substitution at nucleotide position 2 (ATG to ACG).

Next generation sequencing reveals a novel HLA-C allele, HLA-C*16:201.

HLA-C*16:201 differs from HLA-HLA-C*16:01:01 by one nucleotide substitution in codon 73 (ACT ->GCT).

Potent high-avidity neutralizing antibodies and T cell responses after COVID-19 vaccination in individuals with B cell lymphoma and multiple myeloma.

Individuals with hematologic malignancies are at increased risk for severe coronavirus disease 2019 (COVID-19), yet profound analyses of COVID-19 vaccine-induced immunity are scarce. Here we present an observational study with expanded methodological analysis of a longitudinal, primarily BNT162b2 mRNA-vaccinated cohort of 60 infection-naive individuals with B cell lymphomas and multiple myeloma. We show that many of these individuals, despite markedly lower anti-spike IgG titers, rapidly develop potent infection neutralization capacities against several severe acute respiratory syndrome coronavirus 2 variants of concern (VoCs). The observed increased neutralization capacity per anti-spike antibody unit was paralleled by an early step increase in antibody avidity between the second and third vaccination. All individuals with hematologic malignancies, including those depleted of B cells and individuals with multiple myeloma, exhibited a robust T cell response to peptides derived from the spike protein of VoCs Delta and Omicron (BA.1). Consistently, breakthrough infections were mainly of mild to moderate severity. We conclude that COVID-19 vaccination can induce broad antiviral immunity including ultrapotent neutralizing antibodies with high avidity in different hematologic malignancies.

Circulating multimeric immune complexes contribute to immunopathology in COVID-19.

A dysregulated immune response with high levels of SARS-CoV-2 specific IgG antibodies characterizes patients with severe or critical COVID-19. Although a robust IgG response is considered to be protective, excessive triggering of activating Fc-gamma-receptors (FcγRs) could be detrimental and cause immunopathology. Here, we document excessive FcγRIIIA/CD16A activation in patients developing severe or critical COVID-19 but not in those with mild disease. We identify two independent ligands mediating extreme FcγRIIIA/CD16A activation. Soluble circulating IgG immune complexes (sICs) are detected in about 80% of patients with severe and critical COVID-19 at levels comparable to active systemic lupus erythematosus (SLE) disease. FcγRIIIA/CD16A activation is further enhanced by afucosylation of SARS-CoV-2 specific IgG. Utilizing cell-based reporter systems we provide evidence that sICs can be formed prior to a specific humoral response against SARS-CoV-2. Our data suggest a cycle of immunopathology driven by an early formation of sICs in predisposed patients. These findings suggest a reason for the seemingly paradoxical findings of high antiviral IgG responses and systemic immune dysregulation in severe COVID-19. The involvement of circulating sICs in the promotion of immunopathology in predisposed patients opens new possibilities for intervention strategies to mitigate critical COVID-19 progression.

COVID-19 mRNA booster vaccine induces transient CD8+ T effector cell responses while conserving the memory pool for subsequent reactivation.

Immunization with two mRNA vaccine doses elicits robust spike-specific CD8+ T cell responses, but reports of waning immunity after COVID-19 vaccination prompt the introduction of booster vaccination campaigns. However, the effect of mRNA booster vaccination on the spike-specific CD8+ T cell response remains unclear. Here we show that spike-specific CD8+ T cells are activated and expanded in all analyzed individuals receiving the 3rd and 4th mRNA vaccine shots. This CD8+ T cell boost response is followed by a contraction phase and lasts only for about 30-60 days. The spike-specific CD8+ T memory stem cell pool is not affected by the 3rd vaccination. Both 4th vaccination and breakthrough infections with Delta and Omicron rapidly reactivate CD8+ T memory cells. In contrast, neutralizing antibody responses display little boost effect towards Omicron. Thus, COVID-19 mRNA booster vaccination elicits a transient T effector cell response while long-term spike-specific CD8+ T cell immunity is conserved to mount robust memory recall targeting emerging variants of concern.

A novel HLA allele, HLA-A*03:420, identified by next-generation sequencing.

HLA-A*03:420 differs from HLA-A*03:01:01:01 by a single nucleotide in exon 1, codon -22.

Mechanisms of CD8+ T-cell failure in chronic hepatitis E virus infection.

BACKGROUND & AIMS: In immunosuppressed patients, persistent HEV infection is common and may lead to cirrhosis and liver failure. HEV clearance depends on an effective virus-specific CD8+ T-cell response; however, the knowledge gap around HEV-specific CD8+ T-cell epitopes has hindered analysis of the mechanisms of T-cell failure in persistent infection. METHODS: We comprehensively studied HEV-specific CD8+ T-cell responses in 46 patients with self-limiting (n = 34) or chronic HEV infection (n = 12), by epitope-specific expansion, functional testing, ex vivo peptide HLA class I tetramer multi-parametric staining, and viral sequence analysis. RESULTS: We identified 25 HEV-specific CD8+ T-cell epitopes restricted by 9 different HLA class I alleles. In self-limiting HEV infection, HEV-specific CD8+ T cells were vigorous, contracted after resolution of infection, and formed functional memory responses. In contrast, in chronic infection, the HEV-specific CD8+ T-cell response was diminished, declined over time, and displayed phenotypic features of exhaustion. However, improved proliferation of HEV-specific CD8+ T cells, increased interferon-γ production and evolution of a memory-like phenotype were observed upon reduction of immunosuppression and/or ribavirin treatment and were associated with viral clearance. In 1 patient, mutational viral escape in a targeted CD8+ T-cell epitope contributed to CD8+ T-cell failure. CONCLUSION: Chronic HEV infection is associated with HEV-specific CD8+ T-cell exhaustion, indicating that T-cell exhaustion driven by persisting antigen recognition also occurs in severely immunosuppressed hosts. Functional reinvigoration of virus-specific T cells is at least partially possible when antigen is cleared. In a minority of patients, viral escape also contributes to HEV-specific CD8+ T-cell failure and thus needs to be considered in personalized immunotherapeutic approaches. LAY SUMMARY: Hepatitis E virus (HEV) infection is usually cleared spontaneously (without treatment) in patients with fully functioning immune systems. In immunosuppressed patients, chronic HEV infection is common and can progress rapidly to cirrhosis and liver failure. Herein, we identified the presence of HEV-specific CD8+ T cells (a specific type of immune cell that can target HEV) in immunosuppressed patients, but we show that these cells do not function properly. This dysfunction appears to play a role in the development of chronic HEV infection in vulnerable patients.

SARS-CoV-2-specific T-cell epitope repertoire in convalescent and mRNA-vaccinated individuals.

Continuously emerging variants of concern (VOCs) sustain the SARS-CoV-2 pandemic. The SARS-CoV-2 Omicron/B.1.1.529 VOC harbours multiple mutations in the spike protein associated with high infectivity and efficient evasion from humoral immunity induced by previous infection or vaccination. By performing in-depth comparisons of the SARS-CoV-2-specific T-cell epitope repertoire after infection and messenger RNA vaccination, we demonstrate that spike-derived epitopes were not dominantly targeted in convalescent individuals compared to non-spike epitopes. In vaccinees, however, we detected a broader spike-specific T-cell response compared to convalescent individuals. Booster vaccination increased the breadth of the spike-specific T-cell response in convalescent individuals but not in vaccinees with complete initial vaccination. In convalescent individuals and vaccinees, the targeted T-cell epitopes were broadly conserved between wild-type SARS-CoV-2 variant B and Omicron/B.1.1.529. Hence, our data emphasize the relevance of vaccine-induced spike-specific CD8+ T-cell responses in combating VOCs including Omicron/B.1.1.529 and support the benefit of boosting convalescent individuals with mRNA vaccines.

IFNL4 rs368234815 polymorphism does not predict risk of BK virus associated nephropathy after living-donor kidney transplant: A case-control study.

BACKGROUND: BK polyoma virus (BKPyV) associated nephropathy (BKPyVAN) is a major cause of kidney graft loss in renal transplant patients. Interferons (IFNs) are an important innate immune response against viral infections and genetic polymorphisms of the IFN-pathways can affect susceptibility and mortality during viral infection. Here, we investigated whether the dinucleotide polymorphism rs368234815 (ΔG/TT) in the IFNL4 gene contributed to BKPyV reactivation or BKPyVAN after living-donor kidney transplantation. METHODS: This retrospective case-control study determines the prevalence of IFNL4 variants in a Caucasian population of living-donor kidney transplant recipients and donors and explores its association with BKPyV infection and BKPyVAN development. We included 28 recipients with BKPyV reactivation, 10 of which developed BKPyVAN and 30 BKPyV negative controls. Targeted sequencing of the IFNL4 gene from both recipients and their respective donors was performed. RESULTS: We found IFNL4 rs368234815 ΔG allele frequencies of 41.7% in BKPyV negative and 39.3% in BKPyV positive recipients (P = .85), and 41.7% and 40.4% (P>.99) in their respective donors. IFNL4 rs368234815 ΔG allele frequencies in BKPyVAN developing recipients and their respective donors were 50% and 43.7% (P = .60 and P>.99). CONCLUSIONS: Our results indicate that the IFNL4 rs368234815 ΔG allele is not associated with BKPyV reactivation, nor the manifestation of BKPyVAN.

The novel HLA-DQB1*06 null allele, HLA-DQB1*06:423N, identified in a volunteer blood donor.

A single nucleotide exchange in exon 2 at position 370 (C ->T) generates a preterminal STOP encoding a C-terminally truncated protein.

Rapid and stable mobilization of CD8+ T cells by SARS-CoV-2 mRNA vaccine.

SARS-CoV-2 spike mRNA vaccines1-3 mediate protection from severe disease as early as ten days after prime vaccination3, when neutralizing antibodies are hardly detectable4-6. Vaccine-induced CD8+ T cells may therefore be the main mediators of protection at this early stage7,8. The details of their induction, comparison to natural infection, and association with other arms of vaccine-induced immunity remain, however, incompletely understood. Here we show on a single-epitope level that a stable and fully functional CD8+ T cell response is vigorously mobilized one week after prime vaccination with bnt162b2, when circulating CD4+ T cells and neutralizing antibodies are still weakly detectable. Boost vaccination induced a robust expansion that generated highly differentiated effector CD8+ T cells; however, neither the functional capacity nor the memory precursor T cell pool was affected. Compared with natural infection, vaccine-induced early memory T cells exhibited similar functional capacities but a different subset distribution. Our results indicate that CD8+ T cells are important effector cells, are expanded in the early protection window after prime vaccination, precede maturation of other effector arms of vaccine-induced immunity and are stably maintained after boost vaccination.

Low Pre-Transplant Caveolin-1 Serum Concentrations Are Associated with Acute Cellular Tubulointerstitial Rejection in Kidney Transplantation.

Acute and chronic transplant rejections due to alloreactivity are essential contributors to graft loss. However, the strength of alloreactivity is biased by non-immunological factors such as ischemia reperfusion injury (IRI). Accordingly, protection from IRI could be favorable in terms of limiting graft rejection. Caveolin-1 (Cav-1) is part of the cell membrane and an important regulator of intracellular signaling. Cav-1 has been demonstrated to limit IRI and to promote the survival of a variety of cell types including renal cells under stress conditions. Accordingly, Cav-1 could also play a role in limiting anti-graft immune responses. Here, we evaluated a possible association between pre-transplant serum concentrations of Cav-1 and the occurrence of rejection during follow-up in a pilot study. Therefore, Cav-1-serum concentrations were analyzed in 91 patients at the time of kidney transplantation and compared to the incidence of acute and chronic rejection. Higher Cav-1 levels were associated with lower occurrence of acute cellular tubulointerstitial rejection episodes.

Memory-like HCV-specific CD8+ T cells retain a molecular scar after cure of chronic HCV infection.

In chronic hepatitis C virus (HCV) infection, exhausted HCV-specific CD8+ T cells comprise memory-like and terminally exhausted subsets. However, little is known about the molecular profile and fate of these two subsets after the elimination of chronic antigen stimulation by direct-acting antiviral (DAA) therapy. Here, we report a progenitor-progeny relationship between memory-like and terminally exhausted HCV-specific CD8+ T cells via an intermediate subset. Single-cell transcriptomics implicated that memory-like cells are maintained and terminally exhausted cells are lost after DAA-mediated cure, resulting in a memory polarization of the overall HCV-specific CD8+ T cell response. However, an exhausted core signature of memory-like CD8+ T cells was still detectable, including, to a smaller extent, in HCV-specific CD8+ T cells targeting variant epitopes. These results identify a molecular signature of T cell exhaustion that is maintained as a chronic scar in HCV-specific CD8+ T cells even after the cessation of chronic antigen stimulation.

Characterization of pre-existing and induced SARS-CoV-2-specific CD8+ T cells.

Emerging data indicate that SARS-CoV-2-specific CD8+ T cells targeting different viral proteins are detectable in up to 70% of convalescent individuals1-5. However, very little information is currently available about the abundance, phenotype, functional capacity and fate of pre-existing and induced SARS-CoV-2-specific CD8+ T cell responses during the natural course of SARS-CoV-2 infection. Here, we define a set of optimal and dominant SARS-CoV-2-specific CD8+ T cell epitopes. We also perform a high-resolution ex vivo analysis of pre-existing and induced SARS-CoV-2-specific CD8+ T cells, applying peptide-loaded major histocompatibility complex class I (pMHCI) tetramer technology. We observe rapid induction, prolonged contraction and emergence of heterogeneous and functionally competent cross-reactive and induced memory CD8+ T cell responses in cross-sectionally analyzed individuals with mild disease following SARS-CoV-2 infection and three individuals longitudinally assessed for their T cells pre- and post-SARS-CoV-2 infection. SARS-CoV-2-specific memory CD8+ T cells exhibited functional characteristics comparable to influenza-specific CD8+ T cells and were detectable in SARS-CoV-2 convalescent individuals who were seronegative for anti-SARS-CoV-2 antibodies targeting spike (S) and nucleoprotein (N). These results define cross-reactive and induced SARS-CoV-2-specific CD8+ T cell responses as potentially important determinants of immune protection in mild SARS-CoV-2 infection.

Modelling and Measurement of Magnetically Soft Nanowire Arrays for Sensor Applications.

Soft magnetic wires and microwires are currently used for the cores of magnetic sensors. Due to their low demagnetization, they contribute to the high sensitivity and the high spatial resolution of fluxgates, Giant Magnetoimpedance (GMI), and inductive sensors. The arrays of nanowires can be prepared by electrodeposition into predefined pores of a nanoporous polycarbonate membrane. While high coercivity arrays with square loops are convenient for information storage and for bistable sensors such as proximity switches, low coercivity cores are needed for linear sensors. We show that coercivity can be controlled by the geometry of the array: increasing the diameter of nanowires (20 µm in length) from 30 nm to 200 nm reduced the coercivity by a factor of 10, while the corresponding decrease in the apparent permeability was only 5-fold. Finite element simulation of nanowire arrays is important for sensor development, but it is computationally demanding. While an array of 2000 wires can be still modelled in 3D, this is impossible for real arrays containing millions of wires. We have developed an equivalent 2D model, which allows us to solve these large arrays with acceptable accuracy. Using this tool, we have shown that as a core of magnetic sensors, nanowires are efficiently employed only together with microcoils with diameter comparable to the nanowire length.