Klinische Performance eines neuen SARS-CoV-2-Antigen-Tests in der Notaufnahme eines Maximalversorgers

Ein Baustein zur Eindämmung der COVID-19-Pandemie ist die Verfügbarkeit von Tests mit hoher Sensitivität und Spezifität zur Detektion von SARS-CoV-2, insbesondere um Infizierte in vulnerablen Einrichtungen, z. B. Krankenhäusern und Pflegeeinrichtungen, zeitnah identifizieren und isolieren zu können. Dies betrifft alle Personengruppen dieser Einrichtungen, also Patient*innen/Bewohner*innen, Besucher*innen als auch Personal. Bisheriger Goldstandard für den Nachweis einer SARS-CoV-2-Infektion ist die RT-PCR. SARS-CoV-2-Antigen-Tests sind aufgrund ihres Point-of-Care-Ansatzes, der einfachen Handhabung und des günstigeren Preises eine wertvolle Ergänzung zur RT-PCR-Diagnostik. Sie erkennen mit ausreichender Sicherheit SARS-CoV-2-Infektionen bei symptomatischen Patient*innen und in Proben mit niedrigen Ct-Werten in der RT-PCR. Als Einzeltestung bei asymptomatischen Patient*innen ist ihre Wertigkeit dagegen deutlich eingeschränkt. Hier sollten repetitive Antigen-Testungen oder primär PCR-basierte Verfahren zur Anwendung kommen

Protective Immunity to Listeria Monocytogenes Infection Mediated by Recombinant Listeria innocua Harboring the VGC Locus

In this study we propose a novel bacterial vaccine strategy where non-pathogenic bacteria are complemented with traits desirable for the induction of protective immunity. To illustrate the proof of principle of this novel vaccination strategy, we use the model organism of intracellular immunity Listeria. We introduced a, low copy number BAC-plasmid harbouring the virulence gene cluster (vgc) of L. monocytogenes (Lm) into the non-pathogenic L. innocua (L.inn) strain and examined for its ability to induce protective cellular immunity. The resulting strain (L.inn::vgc) was attenuated for virulence in vivo and showed a strongly reduced host detrimental inflammatory response compared to Lm. Like Lm, L.inn::vgc induced the production of Type I Interferon's and protection was mediated by Listeria-specific CD8+ T cells. Rational vaccine design whereby avirulent strains are equipped with the capabilities to induce protection but lack detrimental inflammatory effects offer great promise towards future studies using non-pathogenic bacteria as vectors for vaccination

Role of the CD8+ Dendritic Cell Subset in Transmission of Prions▿

Controversial results have been observed in mouse models regarding the role of lymphoid tissues in prion pathogenesis. To investigate the role of dendritic cells (DC), we used a transgenic mouse model. In this model (CD11c-N17Rac1), a significant reduction of CD8+ CD11chi DC has been described, and the remaining CD8+ DC demonstrate a reduced capacity for the uptake of apoptotic cells. After intraperitoneal prion infection, significantly longer incubation times were observed in CD11c-N17Rac1 mice than in controls, indicating that a defect in CD8+ CD11chi DC significantly impedes neuroinvasion after intraperitoneal infection. In contrast, no distinct differences were observed between CD11c-N17Rac1 mice and controls after oral infection. This provides evidence that oral and intraperitoneal prion infections differ in lymphoreticular requirements

Antibody Targeting the Ferritin-Like Protein Controls Listeria Infection ▿ †

The acquisition of iron during the infection process is essential for the growth of pathogenic microorganisms (S. C. Andrews, Adv. Microb. Physiol. 40:281-351, 1998; H. M. Baker, B. F. Anderson, and E. N. Baker, Proc. Natl. Acad. Sci. U. S. A. 100:3579-3583, 2003). Since the solubility of iron is low and it is toxic at low concentrations, following uptake, iron is stored in subcellular microenvironments in the iron storage protein ferritin (C. Cheers and M. Ho, J. Reticuloendothel. Soc. 34:299-309, 1983). Here, we show that ferritin-like proteins (Frl) are highly conserved in the genus Listeria and demonstrate that these proteins are present in both the cytoplasm and cell wall fractions of these bacteria. Even though Frl is expressed under different growth conditions, transcriptional mapping revealed that its regulation is complex. When bacteria are grown in brain heart infusion medium, extracellular expression involves both sigma A (SigA)- and sigma B (SigB)-dependent promoters; however, during intracellular growth, initiation of transcription is additionally SigB dependent. The expression of Frl is greatly enhanced in bacteria grown in the presence of blood, and a mutant strain lacking the frl gene was defective for growth in this medium. Using the monoclonal antibody (MAb) specific for Frl, we demonstrate that administration of anti-Frl MAb prior to infection confers antilisterial resistance in vivo, evidenced in reduced bacterial load and increased survival rates, thereby demonstrating the in vivo significance of upregulated cell surface-associated Frl expression. In vitro studies revealed that the antilisterial resistance is due to increased listerial phagocytosis

Bacterial load and IFN expression during the course of primary infection.

<p><b>A.</b> Course of primary infection in mice with the wild type <i>Lm</i> (EGD-e) and the recombinant <i>L. inn</i>::vgc strain. Mice were infected i.v. with 10³ cfu <i>Lm</i>, 10⁷ cfu <i>L.inn</i>, or 10⁷ cfu <i>L.inn::vgc</i> strains. At different time intervals after the infection, mice were sacrificed and the number of viable bacteria in the organs was enumerated. <b>B.</b> Quantitative measurement of IFNα2 and IFNb1 expression in bone marrow-derived macrophages using RT-PCR at 2 h and 8 h following infection with <i>Lm</i> , <i>L.inn</i>, or the <i>L.inn</i>::<i>vgc</i> strains. *P<0.05 (<i>L.inn</i> vs. <i>Lm</i> and <i>L.inn::vgc</i> strains).</p

Expression levels of CD62L on CD8⁺ splenocytes following primary and recall infection with <i>Lm</i>, <i>L.inn</i> and the <i>L.inn::vgc</i> strain.

<p>Flow cytometry was performed on spleen cells, isolated from mice on day 60 after the primary infection or day 5 after the challenge. Cells were stained with FITC-labelled anti-Lyt-2 and biotinylated anti-CD62L. The binding of anti-CD62L on the cell surface was detected with PE-conjugated streptavidin. Numbers shown are gated CD8⁺CD62^lo T cells and analyzed with CELLQuest software.</p

Measurement of proinflammatory cytokine levels in serum.

<p>Sera was obtained from mice on days 1, 2, 3, and 4 post-infection after inoculation with 10³ cfu <i>Lm</i>, 10⁷ cfu <i>L.inn</i>, or 10⁷ cfu <i>L.inn::vgc</i>. Levels of IL-1ß, IL-6, IL-12(p70), and TNF-alpha were quantified using a multiplex cytokine assay kit. *P<0.05 (EGD-e vs. <i>L.inn</i> and <i>L.inn::vgc</i> strains).</p

Examination of spleens and DTH response after infection with <i>Lm</i> and the recombinant <i>L.inn::vgc</i> strain.

<p><b>A.</b> Morphological examination of spleens from mice inoculated i.v. with the wild type <i>Lm</i> and the recombinant <i>L.inn::vgc</i> strain. Spleens of mice infected i.v. as mentioned in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035503#pone-0035503-g001" target="_blank">Fig. 1</a> were isolated on day 3 after infection. Shown is a spleen from mice infected with the wild type <i>Lm</i>, the wild type <i>L.inn</i> and its recombinant mutant strain <i>L.inn::vgc</i>. Infiltration of monocytic cells and granulomatous lesions are only detectable in the spleens isolated from mice infected with the wild type <i>Lm</i>. <b>B.</b> Spleen sections were stained with HE and examined. Granulomas with massive leukocyte aggregates can only be detected in spleens of mice infected with <i>Lm</i>. <b>C.</b> DTH response to listerial antigen 9 days after primary infection. Mice were infected with 10³ CFU of <i>Lm</i>, 10⁷ CFU of <i>L.inn</i>, or 10⁷ CFU of <i>L.inn::vgc</i> strain. 9 days after infection, DTH was triggered through injection of soluble somatic listerial antigen. Twenty-four hours later, the specific skin response was determined. The mean value ± S.E. of five animals of a representative experiment is shown.*P<0.05 (EGD-e vs. <i>L.inn::vgc</i> strain).</p

Protective immunity and cellular immune response after infection with <i>Lm</i> and the <i>L.inn::vgc</i> strain.

<p><b>A.</b> Induction of protective immunity conferred after infection with the <i>L.inn::vgc strain</i>. Groups of 15 mice were infected i.v. as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035503#pone-0035503-g001" target="_blank">Fig. 1</a>. Two months later all mice were challenged with a lethal dose (20×LD₅₀) of the wild type <i>Lm</i>. As a control, a group of uninfected normal mice was included. Survival of mice after the challenge was monitored up to 8 days. <b>B.</b> Number of antigen-specific IFN-gamma producing CD8+ T cells in spleens of mice infected i.v. with the wild type <i>Lm</i>, <i>L.inn</i> and <i>L.inn::vgc</i> strain determined by ELISPOT. Spleen cells from infected mice were isolated either on day 9 after the primary infection or day 5 after challenge infection and stimulated with the immunodominant MHC class I peptide LLO_91–99 in triplicates in nitrocellulose based 96-well culture plates. Number of specific IFN-gamma producing cells against the dominant H-2K^d restricted LLO_91–99 epitope were determined by counting the number of spots under the microscope. *P<0.05 (<i>L.inn</i> vs. <i>Lm</i> and <i>L.inn::vgc</i> strains).</p

Klinische Performance eines neuen SARS-CoV-2-Antigen-Tests in der Notaufnahme eines Maximalversorgers

Ein Baustein zur Eindämmung der COVID-19-Pandemie ist die Verfügbarkeit von Tests mit hoher Sensitivität und Spezifität zur Detektion von SARS-CoV-2, insbesondere um Infizierte in vulnerablen Einrichtungen, z. B. Krankenhäusern und Pflegeeinrichtungen, zeitnah identifizieren und isolieren zu können. Dies betrifft alle Personengruppen dieser Einrichtungen, also Patient*innen/Bewohner*innen, Besucher*innen als auch Personal. Bisheriger Goldstandard für den Nachweis einer SARS-CoV-2-Infektion ist die RT-PCR. SARS-CoV-2-Antigen-Tests sind aufgrund ihres Point-of-Care-Ansatzes, der einfachen Handhabung und des günstigeren Preises eine wertvolle Ergänzung zur RT-PCR-Diagnostik. Sie erkennen mit ausreichender Sicherheit SARS-CoV-2-Infektionen bei symptomatischen Patient*innen und in Proben mit niedrigen Ct-Werten in der RT-PCR. Als Einzeltestung bei asymptomatischen Patient*innen ist ihre Wertigkeit dagegen deutlich eingeschränkt. Hier sollten repetitive Antigen-Testungen oder primär PCR-basierte Verfahren zur Anwendung kommen