CD27 is required for protective lytic EBV antigen-specific CD8+ T-cell expansion.

Primary immunodeficiencies in the costimulatory molecule CD27 and its ligand, CD70, predispose for pathologies of uncontrolled Epstein-Barr virus (EBV) infection in nearly all affected patients. We demonstrate that both depletion of CD27+ cells and antibody blocking of CD27 interaction with CD70 cause uncontrolled EBV infection in mice with reconstituted human immune system components. While overall CD8+ T-cell expansion and composition are unaltered after antibody blocking of CD27, only some EBV-specific CD8+ T-cell responses, exemplified by early lytic EBV antigen BMLF1-specific CD8+ T cells, are inhibited in their proliferation and killing of EBV-transformed B cells. This suggests that CD27 is not required for all CD8+ T-cell expansions and cytotoxicity but is required for a subset of CD8+ T-cell responses that protect us from EBV pathology.

Attenuated immune control of Epstein-Barr virus in humanized mice is associated with the multiple sclerosis risk factor HLA-DR15.

Immune responses to Epstein-Barr virus (EBV) infection synergize with the main genetic risk factor HLA-DRB1*15:01 (HLA-DR15) to increase the likelihood to develop the autoimmune disease multiple sclerosis (MS) at least sevenfold. In order to gain insights into this synergy, we investigated HLA-DR15 positive human immune compartments after reconstitution in immune-compromised mice (humanized mice) with and without EBV infection. We detected elevated activation of both CD4+ and CD8+ T cells in HLA-DR15 donor-reconstituted humanized mice at steady state, even when compared to immune compartments carrying HLA-DRB1*04:01 (HLA-DR4), which is associated with other autoimmune diseases. Increased CD8+ T cell expansion and activation was also observed in HLA-DR15 donor-reconstituted humanized mice after EBV infection. Despite this higher immune activation, EBV viral loads were less well controlled in the context of HLA-DR15. Indeed, HLA-DR15-restricted CD4+ T cell clones recognized EBV-transformed B cell lines less efficiently and demonstrated cross-reactivity toward allogeneic target cells and one MS autoantigen. These findings suggest that EBV as one of the main environmental risk factors and HLA-DR15 as the main genetic risk factor for MS synergize by priming hyperreactive T-cell compartments, which then control the viral infection less efficiently and contain cross-reactive CD4+ T cell clones.

CD8+ T cells retain protective functions despite sustained inhibitory receptor expression during Epstein-Barr virus infection in vivo.

Epstein Barr virus (EBV) is one of the most ubiquitous human pathogens in the world, persistently infecting more than 90% of the adult human population. It drives some of the strongest human CD8+ T cell responses, which can be observed during symptomatic primary infection known as infectious mononucleosis (IM). Despite high viral loads and prolonged CD8+ T cell stimulation during IM, EBV enters latency and is under lifelong immune control in most individuals that experience this disease. We investigated whether changes in T cell function, as frequently characterized by PD-1 up-regulation, occur during IM due to the prolonged exposure to high antigen levels. We readily detected the expansion of PD-1 positive CD8+ T cells together with high frequencies of Tim-3, 2B4, and KLRG1 expression during IM and in mice with reconstituted human immune system components (huNSG mice) that had been infected with a high dose of EBV. These PD-1 positive CD8+ T cells, however, retained proliferation, cytokine production, and cytotoxic abilities. Multiple subsets of CD8+ T cells expanded during EBV infection, including PD-1+Tim-3+KLRG1+ cells that express CXCR5 and TCF-1 germinal center homing and memory markers, and may also contain BATF3. Moreover, blocking the PD-1 axis compromised EBV specific immune control and resulted in virus-associated lymphomagenesis. Finally, PD-1+, Tim-3+, and KLRG1+ CD8+ T cell expansion coincided with declining viral loads during low dose EBV infection. These findings suggest that EBV infection primes PD-1 positive CD8+ T cell populations that rely on this receptor axis for the efficient immune control of this ubiquitous human tumor virus.

Improved Diagnostics Help to Identify Clinical Features and Biomarkers That Predict Mycoplasma pneumoniae Community-acquired Pneumonia in Children.

BACKGROUND: There are no reliable signs or symptoms that differentiate Mycoplasma pneumoniae (Mp) infection in community-acquired pneumonia (CAP) from other etiologies. Additionally, current diagnostic tests do not reliably distinguish between Mp infection and carriage. We previously determined that the measurement of Mp-specific immunoglobulin M antibody-secreting cells (ASCs) by enzyme-linked immunospot assay allowed for differentiation between infection and carriage. Using this new diagnostic test, we aimed to identify clinical and laboratory features associated with Mp infection. METHODS: This is a prospective cohort study of children, 3-18 years of age, with CAP from 2016 to 2017. Clinical features and biomarkers were compared between Mp-positive and -negative groups by Mann-Whitney U test or Fisher exact test, as appropriate. Area under the receiver operating characteristic curve (AUC) differences and optimal thresholds were determined by using the DeLong test and Youden J statistic, respectively. RESULTS: Of 63 CAP patients, 29 were Mp-positive (46%). Mp positivity was statistically associated with older age (median, 8.6 vs 4.7 years), no underlying disease, family with respiratory symptoms, prior antibiotic treatment, prolonged prodromal respiratory symptoms and fever, and extrapulmonary (skin) manifestations. Lower levels of C-reactive protein, white blood cell count, absolute neutrophil count, and procalcitonin (PCT), specifically PCT <0.25 µg/L, were statistically associated with Mp infection. A combination of age >5 years (AUC = 0.77), prodromal fever and respiratory symptoms >6 days (AUC = 0.79), and PCT <0.25 µg/L (AUC = 0.81) improved diagnostic performance (AUC = 0.90) (P = .05). CONCLUSIONS: A combination of clinical features and biomarkers may aid physicians in identifying patients at high risk for Mp CAP.

EBV persistence without its EBNA3A and 3C oncogenes in vivo.

The oncogenic Epstein Barr virus (EBV) infects the majority of the human population and usually persists within its host for life without symptoms. The EBV oncoproteins nuclear antigen 3A (EBNA3A) and 3C (EBNA3C) are required for B cell transformation in vitro and are expressed in EBV associated immunoblastic lymphomas in vivo. In order to address the necessity of EBNA3A and EBNA3C for persistent EBV infection in vivo, we infected NOD-scid γcnull mice with reconstituted human immune system components (huNSG mice) with recombinant EBV mutants devoid of EBNA3A or EBNA3C expression. These EBV mutants established latent infection in secondary lymphoid organs of infected huNSG mice for at least 3 months, but did not cause tumor formation. Low level viral persistence in the absence of EBNA3A or EBNA3C seemed to be supported primarily by proliferation with the expression of early latent EBV gene products transitioning into absent viral protein expression without elevated lytic replication. In vitro, EBNA3A and EBNA3C deficient EBV infected B cells could be rescued from apoptosis through CD40 stimulation, mimicking T cell help in secondary lymphoid tissues. Thus, even in the absence of the oncogenes EBNA3A and 3C, EBV can access a latent gene expression pattern that is reminiscent of EBV persistence in healthy virus carriers without prior expression of its whole growth transforming program.

Metagenomic Virome Sequencing in Living Donor and Recipient Kidney Transplant Pairs Revealed JC Polyomavirus Transmission.

BACKGROUND: Before kidney transplantation, donors and recipients are routinely screened for viral pathogens using specific tests. Little is known about unrecognized viruses of the urinary tract that potentially result in transmission. Using an open metagenomic approach, we aimed to comprehensively assess virus transmission in living-donor kidney transplantation. METHODS: Living kidney donors and their corresponding recipients were enrolled at the time of transplantation. Follow-up study visits for recipients were scheduled 4-6 weeks and 1 year thereafter. At each visit, plasma and urine samples were collected and transplant recipients were evaluated for signs of infection or other transplant-related complications. For metagenomic analysis, samples were enriched for viruses, amplified by anchored random polymerase chain reaction (PCR), and sequenced using high-throughput metagenomic sequencing. Viruses detected by sequencing were confirmed using real-time PCR. RESULTS: We analyzed a total of 30 living kidney donor and recipient pairs, with a follow-up of at least 1 year. In addition to viruses commonly detected during routine post-transplant virus monitoring, metagenomic sequencing detected JC polyomavirus (JCPyV) in the urine of 7 donors and their corresponding recipients. Phylogenetic analysis confirmed infection with the donor strain in 6 cases, suggesting transmission from the transplant donor to the recipient, despite recipient seropositivity for JCPyV at the time of transplantation. CONCLUSIONS: Metagenomic sequencing identified frequent transmission of JCPyV from kidney transplant donors to recipients. Considering the high incidence rate, future studies within larger cohorts are needed to define the relevance of JCPyV infection and the donor's virome for transplant outcomes.

Meningitis and epididymitis caused by Toscana virus infection imported to Switzerland diagnosed by metagenomic sequencing: a case report.

BACKGROUND: We report a rare case of Toscana virus infection imported into Switzerland in a 23-year old man who travelled to Imperia (Italy) 10 days before onset of symptoms. Symptoms included both meningitis and as well epididymitis. This is only the fourth case of Toscana virus reported in Switzerland. CASE PRESENTATION: The patient presented with lymphocytic meningitis and scrotal pain due to epididymitis. Meningitis was initially treated with ceftriaxone. Herpes simplex, tick-borne encephalitis, enterovirus, measles, mumps, rubella and Treponema pallidum were excluded with specific polymerase chain reaction (PCR) or serology. In support of routine diagnostic PCR and serology assays, unbiased viral metagenomic sequencing was performed of cerebrospinal fluid and serum. Toscana virus infection was identified in cerebrospinal fluid and the full coding sequence could be obtained. Specific PCR in cerebrospinal fluid and blood and serology with Immunoglobulin (Ig) M and IgG against Toscana virus confirmed our diagnosis. Neurological symptoms recovered spontaneously after 5 days. CONCLUSIONS: This case of Toscana virus infection highlights the benefits of unbiased metagenomic sequencing to support routine diagnostics in rare or unexpected viral infections. With increasing travel histories of patients, physicians should be aware of imported Toscana virus as the agent for viral meningitis and meningoencephalitis.

Persistent mammalian orthoreovirus, coxsackievirus and adenovirus co-infection in a child with a primary immunodeficiency detected by metagenomic sequencing: a case report.

BACKGROUND: We report a rare case of Mammalian orthoreovirus (MRV) infection in a child with a primary immunodeficiency (PID). Infections with Mammalian orthoreovirus are very rare and probably of zoonotic origin. Only a few cases have been described so far, including one with similar pathogenesis as in our case. CASE PRESENTATION: The patient, age 11, presented with flu-like symptoms and persistent severe diarrhea. Enterovirus has been detected over several months, however, exact typing of a positive cell culture remained inconclusive. Unbiased metagenomic sequencing then detected MRV in stool samples from several time points. The sequencing approach further revealed co-infection with a recombinant Coxsackievirus and Adenovirus. MRV-specific antibodies detected by immunofluorescence proved that the patient seroconverted. CONCLUSION: This case highlights the potential of unbiased metagenomic sequencing in supplementing routine diagnostic methods, especially in situations of chronic infection with multiple viruses as seen here in an immunocompromised host. The origin, transmission routes and implications of MRV infection in humans merit further investigation.

Role of the 2B4 Receptor in CD8+ T-Cell-Dependent Immune Control of Epstein-Barr Virus Infection in Mice With Reconstituted Human Immune System Components.

Patients with X-linked lymphoproliferative (XLP) disease due to deficiency in the adaptor molecule signaling lymphocytic activation molecule-associated protein (SAP) are highly susceptible to one specific viral pathogen, the Epstein-Barr virus (EBV). This susceptibility might result from impaired CD8(+) T-cell and natural killer cell responses to EBV infection in these patients. We demonstrate that antibody blocking of the SAP-dependent 2B4 receptor is sufficient to induce XLP-like aggravation of EBV disease in mice with reconstituted human immune system components. CD8(+) T cells require 2B4 for EBV-specific immune control, because 2B4 blockade after CD8(+) T-cell depletion did not further aggravate symptoms of EBV infection.

Usefulness of the GenMark ePlex RPP assay for the detection of respiratory viruses compared to the FTD21 multiplex RT-PCR.

Cartridge-based multiplex panels covering numerous pathogens offer an advantage of minimal hands-on-time and short time to result to commercial RT-PCR assays. In this study, we evaluated the performance of the ePlex respiratory pathogen panel (RPP) compared to the Fast Track Diagnostics Respiratory pathogens 21 multiplex RT-PCR assay (FTD21) using 400 clinical respiratory samples. Discrepant results were further analysed by a reference nucleic acid amplification testing (NAT) and a composite reference approach was used for final interpretation. Discordant results were observed in 56 targets corresponding to 54 samples. Sensitivities and specificities were 85.5% and 99.9% for the ePlex RPP and 95.8% and 99.7% for the FTD21 system, respectively. Altogether, the ePlex RPP is a valuable tool for the rapid detection of a number of different respiratory viruses with the exception of the coronavirus family (low sensitivity ranging from 50-80%) and samples with a low pathogen load (Ct values >33).

Evaluation of the RIDA®GENE RT-PCR assays for detection of sapovirus, astrovirus, adenovirus, and rotavirus in stool samples of adults in Switzerland.

Sapovirus (SaV) and astrovirus (AstV) increasingly are recognized as cause of acute viral gastroenteritis (AGE). We evaluated the real-time RT-PCR assays RIDA®GENE SaV and viral stool panel II (RGN RT-PCR) for detection of SaV, AstV, adenovirus (AdV) F40/41 and rotavirus (RoV) in clinical stool samples (n = 69). Results were compared with reference singleplex RT-PCRs. The sensitivity for SaV, AstV and RoV are 100%, the specificity ranges from 98.1% to 100%. In 10 out of 11 AdV (all types) samples, the RGN RT-PCR for AdV F40/41 displayed negative results. Retrospectively, 196 stool specimens from adult patients previously tested negative for norovirus (NoV) were analyzed. In about 10% of NoV-negative stool samples, AdV (n = 9), RoV (n = 6), AstV (n = 3) or SaV (n = 3) were found. The RGN RT-PCR assays are useful for detection of enteric viruses other than NoV. This study emphasizes the need for further testing of NoV-negative stool samples in patients with AGE.

EBV renders B cells susceptible to HIV-1 in humanized mice.

HIV and EBV are human pathogens that cause a considerable burden to worldwide health. In combination, these viruses are linked to AIDS-associated lymphomas. We found that EBV, which transforms B cells, renders them susceptible to HIV-1 infection in a CXCR4 and CD4-dependent manner in vitro and that CXCR4-tropic HIV-1 integrates into the genome of these B cells with the same molecular profile as in autologous CD4+ T cells. In addition, we established a humanized mouse model to investigate the in vivo interactions of EBV and HIV-1 upon coinfection. The respective mice that reconstitute human immune system components upon transplantation with CD34+ human hematopoietic progenitor cells could recapitulate aspects of EBV and HIV immunobiology observed in dual-infected patients. Upon coinfection of humanized mice, EBV/HIV dual-infected B cells could be detected, but were susceptible to CD8+ T-cell-mediated immune control.

MicroRNAs of Epstein-Barr Virus Attenuate T-Cell-Mediated Immune Control In Vivo.

The human persistent and oncogenic Epstein-Barr virus (EBV) was one of the first viruses that were described to express viral microRNAs (miRNAs). These have been proposed to modulate many host and viral functions, but their predominant role in vivo has remained unclear. We compared recombinant EBVs expressing or lacking miRNAs during in vivo infection of mice with reconstituted human immune system components and found that miRNA-deficient EBV replicates to lower viral titers with decreased frequencies of proliferating EBV-infected B cells. In response, activated cytotoxic EBV-specific T cells expand to lower frequencies than during infection with miRNA-expressing EBV. However, when we depleted CD8+ T cells the miRNA-deficient virus reached similar viral loads as wild-type EBV, increasing by more than 200-fold in the spleens of infected animals. Furthermore, CD8+ T cell depletion resulted in lymphoma formation in the majority of animals after miRNA-deficient EBV infection, while no tumors emerged when CD8+ T cells were present. Thus, miRNAs mainly serve the purpose of immune evasion from T cells in vivo and could become a therapeutic target to render EBV-associated malignancies more immunogenic.IMPORTANCE Epstein-Barr virus (EBV) infects the majority of the human population and usually persists asymptomatically within its host. Nevertheless, EBV is the causative agent for infectious mononucleosis (IM) and for lymphoproliferative disorders, including Burkitt and Hodgkin lymphomas. The immune system of the infected host is thought to prevent tumor formation in healthy virus carriers. EBV was one of the first viruses described to express miRNAs, and many host and viral targets were identified for these in vitro However, their role during EBV infection in vivo remained unclear. This work is the first to describe that EBV miRNAs mainly increase viremia and virus-associated lymphomas through dampening antigen recognition by adaptive immune responses in mice with reconstituted immune responses. Currently, there is no prophylactic or therapeutic treatment to restrict IM or EBV-associated malignancies; thus, targeting EBV miRNAs could promote immune responses and limit EBV-associated pathologies.

Two Years of Viral Metagenomics in a Tertiary Diagnostics Unit: Evaluation of the First 105 Cases.

Metagenomic next-generation sequencing (mNGS) can capture the full spectrum of viral pathogens in a specimen and has the potential to become an all-in-one solution for virus diagnostics. To date, clinical application is still in an early phase and limitations remain. Here, we evaluated the impact of viral mNGS for cases analyzed over two years in a tertiary diagnostics unit. High throughput mNGS was performed upon request by the treating clinician in cases where the etiology of infection remained unknown or the initial differential diagnosis was very broad. The results were compared to conventional routine testing regarding outcome and workload. In total, 163 specimens from 105 patients were sequenced. The main sample types were cerebrospinal fluid (34%), blood (33%) and throat swabs (10%). In the majority of the cases, viral encephalitis/meningitis or respiratory infection was suspected. In parallel, conventional virus diagnostic tests were performed (mean 18.5 individually probed targets/patients). mNGS detected viruses in 34 cases (32%). While often confirmatory, in multiple cases, the identified viruses were not included in the selected routine diagnostic tests. Two years of mNGS in a tertiary diagnostics unit demonstrated the advantages of a single, untargeted approach for comprehensive, rapid and efficient virus diagnostics, confirming the utility of mNGS in complementing current routine tests.

Plasmacytoid dendritic cells respond to Epstein-Barr virus infection with a distinct type I interferon subtype profile.

Infectious mononucleosis, caused by infection with the human gamma-herpesvirus Epstein-Barr virus (EBV), manifests with one of the strongest CD8+ T-cell responses described in humans. The resulting T-cell memory response controls EBV infection asymptomatically in the vast majority of persistently infected individuals. Whether and how dendritic cells (DCs) contribute to the priming of this near-perfect immune control remains unclear. Here we show that of all the human DC subsets, plasmacytoid DCs (pDCs) play a central role in the detection of EBV infection in vitro and in mice with reconstituted human immune system components. pDCs respond to EBV by producing the interferon (IFN) subtypes α1, α2, α5, α7, α14, and α17. However, the virus curtails this type I IFN production with its latent EBV gene products EBNA3A and EBNA3C. The induced type I IFNs inhibit EBV entry and the proliferation of latently EBV-transformed B cells but do not influence lytic reactivation of the virus in vitro. In vivo, exogenous IFN-α14 and IFN-α17, as well as pDC expansion, delay EBV infection and the resulting CD8+ T-cell expansion, but pDC depletion does not significantly influence EBV infection. Thus, consistent with the observation that primary immunodeficiencies compromising type I IFN responses affect only alpha- and beta-herpesvirus infections, we found that EBV elicits pDC responses that transiently suppress viral replication and attenuate CD8+ T-cell expansion but are not required to control primary infection.

Metagenomic sequencing complements routine diagnostics in identifying viral pathogens in lung transplant recipients with unknown etiology of respiratory infection.

BACKGROUND: Lung transplant patients are a vulnerable group of immunosuppressed patients that are prone to frequent respiratory infections. We studied 60 episodes of respiratory symptoms in 71 lung transplant patients. Almost half of these episodes were of unknown infectious etiology despite extensive routine diagnostic testing. METHODS: We re-analyzed respiratory samples of all episodes with undetermined etiology in order to detect potential viral pathogens missed/not accounted for in routine diagnostics. Respiratory samples were enriched for viruses by filtration and nuclease digestion, whole nucleic acids extracted and randomly amplified before high throughput metagenomic virus sequencing. Viruses were identified by a bioinformatic pipeline and confirmed and quantified using specific real-time PCR. RESULTS: In completion of routine diagnostics, we identified and confirmed a viral etiology of infection by our metagenomic approach in four patients (three Rhinovirus A, one Rhinovirus B infection) despite initial negative results in specific multiplex PCR. Notably, the majority of samples were also positive for Torque teno virus (TTV) and Human Herpesvirus 7 (HHV-7). While TTV viral loads increased with immunosuppression in both throat swabs and blood samples, HHV-7 remained at low levels throughout the observation period and was restricted to the respiratory tract. CONCLUSION: This study highlights the potential of metagenomic sequencing for virus diagnostics in cases with previously unknown etiology of infection and in complex diagnostic situations such as in immunocompromised hosts.

Persistent KSHV Infection Increases EBV-Associated Tumor Formation In Vivo via Enhanced EBV Lytic Gene Expression.

The human tumor viruses Epstein-Barr virus (EBV) and Kaposi sarcoma-associated herpesvirus (KSHV) establish persistent infections in B cells. KSHV is linked to primary effusion lymphoma (PEL), and 90% of PELs also contain EBV. Studies on persistent KSHV infection in vivo and the role of EBV co-infection in PEL development have been hampered by the absence of small animal models. We developed mice reconstituted with human immune system components as a model for KSHV infection and find that EBV/KSHV dual infection enhanced KSHV persistence and tumorigenesis. Dual-infected cells displayed a plasma cell-like gene expression pattern similar to PELs. KSHV persisted in EBV-transformed B cells and was associated with lytic EBV gene expression, resulting in increased tumor formation. Evidence of elevated lytic EBV replication was also found in EBV/KSHV dually infected lymphoproliferative disorders in humans. Our data suggest that KSHV augments EBV-associated tumorigenesis via stimulation of lytic EBV replication.

Cognate HLA absence in trans diminishes human NK cell education.

NK cells are innate lymphocytes with protective functions against viral infections and tumor formation. Human NK cells carry inhibitory killer cell Ig-like receptors (KIRs), which recognize distinct HLAs. NK cells with KIRs for self-HLA molecules acquire superior cytotoxicity against HLA- tumor cells during education for improved missing-self recognition. Here, we reconstituted mice with human hematopoietic cells from donors with homozygous KIR ligands or with a mix of hematopoietic cells from these homozygous donors, allowing assessment of the resulting KIR repertoire and NK cell education. We found that co-reconstitution with 2 KIR ligand-mismatched compartments did not alter the frequency of KIR-expressing NK cells. However, NK cell education was diminished in mice reconstituted with parallel HLA compartments due to a lack of cognate HLA molecules on leukocytes for the corresponding KIRs. This change in NK cell education in mixed human donor-reconstituted mice improved NK cell-mediated immune control of EBV infection, indicating that mixed hematopoietic cell populations could be exploited to improve NK cell reactivity against leukotropic pathogens. Taken together, these findings indicate that leukocytes lacking cognate HLA ligands can disarm KIR+ NK cells in a manner that may decrease HLA- tumor cell recognition but allows for improved NK cell-mediated immune control of a human γ-herpesvirus.

Human natural killer cells prevent infectious mononucleosis features by targeting lytic Epstein-Barr virus infection.

Primary infection with the human oncogenic Epstein-Barr virus (EBV) can result in infectious mononucleosis (IM), a self-limiting disease caused by massive lymphocyte expansion that predisposes for the development of distinct EBV-associated lymphomas. Why some individuals experience this symptomatic primary EBV infection, whereas the majority acquires the virus asymptomatically, remains unclear. Using a mouse model with reconstituted human immune system components, we show that depletion of human natural killer (NK) cells enhances IM symptoms and promotes EBV-associated tumorigenesis mainly because of a loss of immune control over lytic EBV infection. These data suggest that failure of innate immune control by human NK cells augments symptomatic lytic EBV infection, which drives lymphocyte expansion and predisposes for EBV-associated malignancies.