The type I interferon (IFN) system plays an important role in controlling herpesvirus infections, but it is unclear which IFN-mediated effectors interfere with herpesvirus replication. Here we report that human myxovirus resistance protein B (MxB, also designated Mx2) is a potent human herpesvirus restriction factor in the context of IFN. We demonstrate that ectopic MxB expression restricts a range of herpesviruses from the Alphaherpesvirinae and Gammaherpesvirinae, including herpes simplex virus 1 and 2 (HSV-1 and HSV-2), and Kaposi’s sarcoma-associated herpesvirus (KSHV). MxB restriction of HSV-1 and HSV-2 requires GTPase function, in contrast to restriction of lentiviruses. MxB inhibits the delivery of incoming HSV-1 DNA to the nucleus and the appearance of empty capsids, but not the capsid delivery to the cytoplasm or tegument dissociation from the capsid. Our study identifies MxB as a potent pan-herpesvirus restriction factor which blocks the uncoating of viral DNA from the incoming viral capsid.

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.

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) is increasingly used for the identification of bacteria and fungi in the diagnostic laboratory. We evaluated the mold database of Bruker Daltonik (Bremen, Germany), the Filamentous Fungi Library 1.0. First, we studied 83 phenotypically and molecularly well-characterized, nondermatophyte, nondematiaceous molds from a clinical strain collection. Using the manufacturer-recommended interpretation criteria, genus and species identification rates were 78.3% and 54.2%, respectively. Reducing the species cutoff from 2.0 to 1.7 significantly increased species identification to 71.1% without increasing misidentifications. In a subsequent prospective study, 200 consecutive clinical mold isolates were identified by the MALDI Biotyper and our conventional identification algorithm. Discrepancies were resolved by ribosomal DNA (rDNA) internal transcribed spacer region sequence analysis. For the MALDI Biotyper, genus and species identification rates were 83.5% and 79.0%, respectively, when using a species cutoff of 1.7. Not identified were 16.5% of the isolates. Concordant genus and species assignments of MALDI-TOF MS and the conventional identification algorithm were observed for 98.2% and 64.2% of the isolates, respectively. Four erroneous species assignments were observed using the MALDI Biotyper. The MALDI Biotyper seems highly reliable for the identification of molds when using the Filamentous Fungi Library 1.0 and a species cutoff of 1.7. However, expansion of the database is required to reduce the number of nonidentified isolates. Molds are an important cause of morbidity and mortality among hospitalized patients, particularly among those who are immunocompromised or suffer from serious underlying disease (1-3). Traditionally, identification of molds in the diagnostic mycology laboratory is based on phenotypic traits (4-6). Sufficient growth and sporulation are required to assess macromorphological criteria, including growth on different media and at different temperatures, as well as micromorphological criteria, such as shape of conidia, spores, and mycelial structures. Conventional identification methods have important drawbacks: (i) conventional identification of molds requires a comparably long time to result, (ii) the enormous morphological variability of molds asks for extensive individual expertise of the laboratory personnel, and (iii) some mold isolates do not develop their characteristic structural features under laboratory conditions, preventing identification or even leading to misidentifications. Nucleic acid sequence analysis of the internal transcribed spacer (ITS) regions between the 18S and 28S rRNA genes has emerged as an alternative to conventional identification, especially for isolates with unusual phenotypic profiles and rare molds, including environmental contaminants (4, 7-9).Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) is increasingly used in diagnostic bacter...

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.

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.

Streptococcus tigurinus sp. nov., isolated from blood of patients with endocarditis, meningitis and spondylodiscitis

Background: The use of probiotics as prophylaxis for necrotizing enterocolitis (NEC) in preterm infants is being increasingly practised. Objective: We report, for the first time, a case series of 3 preterm, very-low-birth-weight (VLBW) infants who developed bacteremia with Bifidobacterium longum on probiotic therapy with Infloran® containing viable B. longum. Methods: We retrospectively reviewed data of3 infants (of gestational age <30 weeks and birth weight <1,230 g). They were admitted to the neonatal intensive care unit. Clinical data were retrieved from their medical records. Results: In infants 1 and 2, B. longum was isolated from the blood cultures when they were on probiotic therapy with Infloran or shortly after, respectively, and was interpreted as transient bacteremia. The clinical presentation of these infants did not require antibiotic treatment after the isolation of B. longum. Infant 3 developed an NEC despite probiotic therapy with Infloran and the blood cultures showed B. longum growth. This infant required explorative laparotomy and antibiotic treatment. The clinical isolates of B. longum and the strain of the Infloran capsule showed an identical profile on biochemical, mass-spectrometric and molecular analyses, suggesting a direct correlation between the administration of probiotics and bacteremia with B. longum in all 3 infants. Conclusions: The occurrence of bacteremia with bifidobacteria after its prophylactic administration in VLBW infants and its possible clinical consequences are a matter of concern. In the interests of safety, the use of probiotics in such a population should be indicated with caution and requires further investigation.

eWe recently described the novel species Streptococcus tigurinus sp. nov. belonging to the Streptococcus mitis group. The type strain AZ_3aT of S. tigurinus was originally isolated from a patient with infective endocarditis. According to its phenotypic and molecular characteristics, S. tigurinus is most closely related to Streptococcus mitis, Streptococcus pneumoniae, Streptococcus pseudopneumoniae, Streptococcus oralis, and Streptococcus infantis. Accurate identification of S. tigurinus is facilitated by 16S rRNA gene analysis. We retrospectively analyzed our 16S rRNA gene molecular database, which contains sequences of all clinical samples obtained in our institute since 2003. We detected 17 16S rRNA gene sequences which were assigned to S. tigurinus, including sequences from the 3 S. tigurinus strains described previously. S. tigurinus originated from normally sterile body sites, such as blood, cerebrospinal fluid, or heart valves, of 14 patients and was initially detected by culture or broad-range 16S rRNA gene PCR, followed by sequencing. The 14 patients had serious invasive infections, i.e., infective endocarditis (n ‫؍‬ 6), spondylodiscitis (n ‫؍‬ 3), bacteremia (n ‫؍‬ 2), meningitis (n ‫؍‬ 1), prosthetic joint infection (n ‫؍‬ 1), and thoracic empyema (n ‫؍‬ 1). To evaluate the presence of Streptococcus tigurinus in the endogenous oral microbial flora, we screened saliva specimens of 31 volunteers. After selective growth, alpha-hemolytic growing colonies were analyzed by matrix-assisted laser desorption ionizationtime of flight mass spectrometry (MALDI-TOF MS) and subsequent molecular methods. S. tigurinus was not identified among 608 strains analyzed. These data indicate that S. tigurinus is not widely distributed in the oral cavity. In conclusion, S. tigurinus is a novel agent of invasive infections, particularly infective endocarditis. (1,3,8,11,17). In addition, we have shown that S. mitis strain ATCC 15914 was initially misassigned when it was identified in 1977 (9); molecular analyses revealed the identification of strain ATCC 15914 as S. tigurinus (21). S. tigurinus colonies on sheep blood agar are alpha-hemolytic, smooth, and white to grayish with a diameter of 0.5 to 1 mm after incubation at 37°C with CO 2 for 24 h (21). Analyses by Vitek 2 resulted in identification as S. mitis/S. oralis, and analyses by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) revealed identification as S. pneumoniae with a score of Ն2.2 (21). However, the limited discriminative power of MALDI-TOF MS within the S. mitis group has been recognized previously by other authors (10,18,20). Hence, an identification result of S. pneumoniae, even with a score as high as Ն2.2, has to be interpreted with caution. Thus, analyses by commercial test systems, such as Vitek 2, or by MALDI-TOF MS are helpful for initial assignment to the S. mitis group, but genetic analyses are required for definitive assignment as S. tigurinus. We demonstrated a significant sequence demarcation within the 5...