Cell-Mediated Immune Responses and Immunopathogenesis of Human Tick-Borne Encephalitis Virus-Infection

Tick-borne encephalitis virus (TBEV) is a flavivirus that belongs to the Flaviviridae family. TBEV is transmitted to humans primarily from infected ticks. The virus causes tick-borne encephalitis (TBE), an acute viral disease that affects the central nervous system (CNS). Infection can lead to acute neurological symptoms of significant severity due to meningitis or meningo(myelo)encephalitis. TBE can cause long-term suffering and has been recognized as an increasing public health problem. TBEV-affected areas currently include large parts of central and northern Europe as well as northern Asia. Infection with TBEV triggers a humoral as well as a cell-mediated immune response. In contrast to the well-characterized humoral antibody-mediated response, the cell-mediated immune responses elicited to natural TBEV-infection have been poorly characterized until recently. Here, we review recent progress in our understanding of the cell-mediated immune response to human TBEV-infection. A particular emphasis is devoted to studies of the response mediated by natural killer (NK) cells and CD8 T cells. The studies described include results revealing the temporal dynamics of the T cell- as well as NK cell-responses in relation to disease state and functional characterization of these cells. Additionally, we discuss specific immunopathological aspects of TBEV-infection in the CNS

Robust T Cell Immunity in Convalescent Individuals with Asymptomatic or Mild COVID-19

SARS-CoV-2-specific memory T cells will likely prove critical for long-term immune protection against COVID-19. Here, we systematically mapped the functional and phenotypic landscape of SARS-CoV-2-specific T cell responses in unexposed individuals, exposed family members, and individuals with acute or convalescent COVID-19. Acute-phase SARS-CoV-2-specific T cells displayed a highly activated cytotoxic phenotype that correlated with various clinical markers of disease severity, whereas convalescent-phase SARS-CoV-2-specific T cells were polyfunctional and displayed a stem-like memory phenotype. Importantly, SARS-CoV-2-specific T cells were detectable in antibody-seronegative exposed family members and convalescent individuals with a history of asymptomatic and mild COVID-19. Our collective dataset shows that SARS-CoV-2 elicits broadly directed and functionally replete memory T cell responses, suggesting that natural exposure or infection may prevent recurrent episodes of severe COVID-19.Fil: Sekine, Takuya. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Perez Potti, André. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Rivera Ballesteros, Olga. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Strålin, Kristoffer. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Gorin, Jean Baptiste. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Olsson, Annika. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Llewellyn Lacey, Sian. University Hospital of Wales; Reino UnidoFil: Kamal, Habiba. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Bogdanovic, Gordana. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Muschiol, Sandra. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Wullimann, David J.. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Kammann, Tobias. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Emgård, Johanna. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Parrot, Tiphaine. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Folkesson, Elin. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Rooyackers, Olav. Karolinska Huddinge Hospital. Karolinska Institutet; Suecia. Karolinska University Hospital; SueciaFil: Eriksson, Lars I.. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Henter, Jan Inge. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Sönnerborg, Anders. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Allander, Tobias. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Albert, Jan. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Nielsen, Morten. Technical University of Denmark; Dinamarca. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas; ArgentinaFil: Klingstrom, Jonas. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Gredmark Russ, Sara. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Björkström, Niklas K.. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Sandberg, Johan K.. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Price, David A.. Cardiff University School of Medicine; Reino UnidoFil: Ljunggren, Hans Gustaf. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Aleman, Soo. Karolinska Huddinge Hospital. Karolinska Institutet; SueciaFil: Buggert, Marcus. Karolinska Huddinge Hospital. Karolinska Institutet; Sueci

Robust T cell immunity in convalescent individuals with asymptomatic or mild COVID-19

SARS-CoV-2-specific memory T cells will likely prove critical for long-term immune protection against COVID-19. Here, we systematically mapped the functional and phenotypic landscape of SARS-CoV-2-specific T cell responses in unexposed individuals, exposed family members, and individuals with acute or convalescent COVID-19. Acute-phase SARS-CoV-2-specific T cells displayed a highly activated cytotoxic phenotype that correlated with various clinical markers of disease severity, whereas convalescent-phase SARS-CoV-2-specific T cells were polyfunctional and displayed a stem-like memory phenotype. Importantly, SARS-CoV-2-specific T cells were detectable in antibody-seronegative exposed family members and convalescent individuals with a history of asymptomatic and mild COVID-19. Our collective dataset shows that SARS-CoV-2 elicits broadly directed and functionally replete memory T cell responses, suggesting that natural exposure or infection may prevent recurrent episodes of severe COVID-19

Deaths from Tick-Borne Encephalitis, Sweden

We assessed standardized mortality ratio in tick-borne encephalitis (TBE) in Sweden, 2004-2017. Standardized mortality ratio for TBE was 3.96 (95% CI 2.55-5.90); no cases in patients <40 years of age were fatal. These results underscore the need for further vaccination efforts in populations at risk for TBE

Infection with Human Cytomegalovirus Alters the MMP-9/TIMP-1 Balance in Human Macrophages▿

Human cytomegalovirus (HCMV) has been suggested to contribute to the development of vascular diseases. Since matrix metalloproteinases (MMPs) have been implicated in atherosclerosis and plaque rupture, we investigated the effect of HCMV infection on MMP expression in human macrophages. We used quantitative real-time PCR, Western blotting, and gelatin zymography to study the expression and activity of MMP-2, -3, -7, -9, -12, -13, and -14 and of tissue inhibitor of metalloproteinase 1 (TIMP-1), -2, -3, and -4. HCMV infection reduced MMP-9 mRNA, protein, and activity levels but increased TIMP-1 mRNA and protein levels. Furthermore, a decrease in MMP-12, MMP-14, TIMP-2, and TIMP-3 mRNA levels could be detected. The MMP-9 and TIMP-1 mRNA alterations required viral replication. MMP-9 mRNA expression was affected by an immediate-early or early viral gene product, whereas TIMP-1 mRNA expression was affected by late viral gene products. We conclude that HCMV infection specifically alters the MMP-9/TIMP-1 balance in human macrophages, which in turn reduces MMP-9 activity in infected cells. Since MMP-9 prevents atherosclerotic plaque development in mice, these results suggest that HCMV may contribute to atherogenesis through specific effects on MMP-9 activity

The CD8 T-Cell Response against Murine Gammaherpesvirus 68 Is Directed toward a Broad Repertoire of Epitopes from both Early and Late Antigens ▿ †

Infection of mice with murine gammaherpesvirus 68 (MHV-68) robustly activates CD8 T cells, but only six class I major histocompatibility complex (MHC)-restricted epitopes have been described to date for the widely used H-2b haplotype mice. To explore the specificity and kinetics of the cytotoxic T-lymphocyte response in MHV-68-infected C57BL/6 mice, we screened for H-2Kb- and H-2Db-restricted epitopes using a set of 384 candidate epitopes in an MHC tetramer-based approach and identified 19 new epitopes in 16 different open reading frames. Of the six known H-2Kb- and H-2Db-restricted epitopes, we confirmed a response against three and did not detect CD8 T-cell-specific responses for the remaining three. The peak of the CD8 T-cell response to most peptides occurs between 6 and 10 days postinfection. The respective MHC tetramer-positive CD8 T cells display an activated/effector phenotype (CD62Llo and CD44hi) and produce gamma interferon upon peptide stimulation ex vivo. MHV-68 infection in vivo elicits a response to multiple viral epitopes, derived from both early and late viral antigens, illustrating a far broader T-cell repertoire and more-rapid activation than those previously recorded

A Gammaherpesvirus Ubiquitin-Specific Protease Is Involved in the Establishment of Murine Gammaherpesvirus 68 Infection ▿

Murine gammaherpesvirus 68 (MHV-68) contains a ubiquitin (Ub)-specific cysteine protease (USP) domain embedded within the large tegument protein ORF64, as do all other herpesviruses. The biological role of this protease is still unclear, but for the alphaherpesvirus Marek's disease virus, its USP is involved in T-cell lymphoma formation. We here study the role of the MHV-68 USP, encoded by ORF64. By constructing a mutant virus with a single cysteine-to-alanine replacement in the active site of ORF64, we demonstrate that the USP activity of ORF64 is abolished. The mutant virus replicates less efficiently in vitro, and plaque size is reduced compared to that of a revertant virus. Electron microscopy of infected cells did not reveal any obvious differences in virion morphogenesis or differences in egress for the mutant and revertant viruses. Intraperitoneal infection of C57/BL6 mice demonstrates that the mutant virus is generally cleared by day 7, indicating a role for the USP in the persistence of MHV-68 infection or efficient replication. However, the USP activity in MHV-68 is unlikely to be involved in the establishment of latency or reactivation, since we observed no significant difference in viral DNA genome copy number in the spleen or in the number of cells that reactivate MHV-68 from latency. Our results for MHV-68 ORF64 are consistent with an enzymatic function of the tegument protein that is beneficial to the virus during acute infection, particularly in vivo

Comprehensive proteomics and meta-analysis of COVID-19 host response

Abstract COVID-19 is characterised by systemic immunological perturbations in the human body, which can lead to multi-organ damage. Many of these processes are considered to be mediated by the blood. Therefore, to better understand the systemic host response to SARS-CoV-2 infection, we performed systematic analyses of the circulating, soluble proteins in the blood through global proteomics by mass-spectrometry (MS) proteomics. Here, we show that a large part of the soluble blood proteome is altered in COVID-19, among them elevated levels of interferon-induced and proteasomal proteins. Some proteins that have alternating levels in human cells after a SARS-CoV-2 infection in vitro and in different organs of COVID-19 patients are deregulated in the blood, suggesting shared infection-related changes.The availability of different public proteomic resources on soluble blood proteome alterations leaves uncertainty about the change of a given protein during COVID-19. Hence, we performed a systematic review and meta-analysis of MS global proteomics studies of soluble blood proteomes, including up to 1706 individuals (1039 COVID-19 patients), to provide concluding estimates for the alteration of 1517 soluble blood proteins in COVID-19. Finally, based on the meta-analysis we developed CoViMAPP, an open-access resource for effect sizes of alterations and diagnostic potential of soluble blood proteins in COVID-19, which is publicly available for the research, clinical, and academic community

Specificity and Dynamics of Effector and Memory CD8 T Cell Responses in Human Tick-Borne Encephalitis Virus Infection

<div><p>Tick-borne encephalitis virus (TBEV) is transferred to humans by ticks. The virus causes tick-borne encephalitis (TBE) with symptoms such as meningitis and meningoencephalitis. About one third of the patients suffer from long-lasting sequelae after clearance of the infection. Studies of the immune response during TBEV-infection are essential to the understanding of host responses to TBEV-infection and for the development of therapeutics. Here, we studied in detail the primary CD8 T cell response to TBEV in patients with acute TBE. Peripheral blood CD8 T cells mounted a considerable response to TBEV-infection as assessed by Ki67 and CD38 co-expression. These activated cells showed a CD45RA-CCR7-CD127- phenotype at day 7 after hospitalization, phenotypically defining them as effector cells. An immunodominant HLA-A2-restricted TBEV epitope was identified and utilized to study the characteristics and temporal dynamics of the antigen-specific response. The functional profile of TBEV-specific CD8 T cells was dominated by variants of mono-functional cells as the effector response matured. Antigen-specific CD8 T cells predominantly displayed a distinct Eomes+Ki67+T-bet+ effector phenotype at the peak of the response, which transitioned to an Eomes-Ki67-T-bet+ phenotype as the infection resolved and memory was established. These transcription factors thus characterize and discriminate stages of the antigen-specific T cell response during acute TBEV-infection. Altogether, CD8 T cells responded strongly to acute TBEV infection and passed through an effector phase, prior to gradual differentiation into memory cells with distinct transcription factor expression-patterns throughout the different phases.</p></div

Activation of T cells in the acute phase of TBE infection.

<p>(A) CD38 and Ki67 co-expressing cells in the total CD8 T cell population over time in one representative patient. (B) Median and 10–90th percentiles of CD38 and Ki67 co-expression in CD8 T cell subsets at day 0, 7, 21 and 90 after hospitalization in infected subjects (n = 20) and in healthy controls (n = 20). (C) Ki67 expression vs CMV-pp65 HLA MHC class I tetramer staining over time in one donor. Percent Ki67⁺ CMV pp65⁺ cells are indicated in the plot. (D) Kinetics of Ki67 expression in CMV⁺ (red line) and CMV⁻ (black line) CD8 T cells in four donors over time. (E) Stainings of perforin, CD45RA, PD-1, Bcl-2, CD127, granzyme B, CD27 and HLA-DR at day 7 after hospitalization. Gated on total CD8 T cells. (F) Bar plots show the 10–90th percentiles of HLA-DR, Bcl-2, PD-1, granzyme B, perforin and CD127 expression together with CD27 in terms of mean fluorescence intensity in CD38 and Ki67 co-expressing CD8 T cell subset at day 7 after hospitalization, non-activated Ki67⁻CD38⁻ (N-A) cells at day 7 after hospitalization or in non-activated healthy controls (N-A HC). (G) Bar chart represents the subset distribution of CCR7, CD45RA and CD127 (IL7Rα) in CD38 and Ki67 co-expressing cells at day 7 after hospitalization. (H) CD38 and Ki67-coexpressing cells in CD4 cell population over time in one infected patient. (I) Median and 10–90^th percentiles of CD38 and Ki67 co-expression in CD4 T cell subset at the day of hospitalization (day 0) and at day 7, 21 and 90 after hospitalization in infected subjects (n = 20) together with healthy controls (n = 20). Statistical analysis was performed using non-parametric repeated measures ANOVA test or the Mann-Whitney test. *, p < 0.05; **, p < 0.01; ***, p < 0.001.</p