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pdf). All assays tested were found to be highly specific for SARS-CoV-2, with no cross-reactivity with other respiratory viruses observed in our analyses regardless of the primer/probe set or kit used. These results will provide valuable information to other clinical laboratories who are actively developing SARS-CoV-2 testing protocols at a time when increased testing capacity is urgently needed worldwide. Copyright © 2020 Nalla et al.The gram-positive bacterium Erysipelothrix rhusiopathiae is a zoonotic pathogen that causes erysipelas in a wide range of mammalian and avian species. Historically, E. rhusiopathiae has been differentiated from other Erysipelothrix species by serotyping. Among 28 serovars of Erysipelothrix species, specific serovars, namely, 1a, 1b, and 2 of E. rhusiopathiae, are associated mainly with the disease in pigs, poultry, and humans; however, other serovar strains are often simultaneously isolated from diseased and healthy animals, indicating the importance of isolate serotyping for epidemiology. The traditional serotyping protocol, which uses heat-stable peptidoglycan antigens and type-specific rabbit antisera in an agar-gel precipitation test, is time consuming and labor intensive. To develop a rapid serotyping scheme, we analyzed sequences of the 12-kb to 22-kb chromosomal region, which corresponds to the genetic region responsible for virulence of serovar 1a and 2 strains of E. rhusiopathiae, of the 28 serovars of Erysipelothrix species. We confirmed that the serovar 13 strain lacks the genomic region and that some serovar strains possess very similar or the same genetic structure, prohibiting differentiation of the serovars. We created 4 multiplex PCR sets allowing the simultaneous detection and differentiation of the majority of Erysipelothrix serovars. Together with a previously reported multiplex PCR that can differentiate serovars 1a, 1b, 2, and 5, the multiplex PCR-based assay developed in this study covers all but one (serovar 13) of the reported serovars of Erysipelothrix species and should be a valuable tool for etiological as well as epidemiological studies of Erysipelothrix infections. Copyright © 2020 American Society for Microbiology.Currently available diagnostic tests for Clostridioides difficile infection (CDI) lack specificity or sensitivity, which has led to guideline recommendations for multistep testing algorithms. Ultrasensitive assays for detection of C. difficile toxins provide measurements of disease-specific markers at very low concentrations. These assays may show improved accuracy compared to current testing methods and offer a potential standalone solution for CDI diagnosis, although large studies of clinical performance and accuracy are lacking. Copyright © 2020 American Society for Microbiology.C-reactive protein (CRP) can increase up to 1000-fold in blood and form complexes with very low density lipoproteins (VLDL). These complexes are associated with worse outcomes for septic patients, and this suggests a potential pathological role in sepsis. Complex formation is heightened when CRP is over 200 mg/l and levels are associated with the severity of sepsis and blood bacterial culture positivity. Using a mouse bacteremia model, blood bacterial clearance can be delayed by i.v. PD98059 inhibitor injection of CRP-VLDL complexes. Complexes are more efficiently taken up by activated U937 cells in vitro and Kupffer cells in vivo than VLDL alone. Both in vitro-generated and naturally occurring CRP-VLDL complexes reduce phagocytosis of bacteria by activated U937 cells. Fcγ and scavenger receptors are involved and a competitive mechanism for clearance of CRP-VLDL complexes and bacteria is demonstrated. Interaction of phosphocholine groups on VLDL with CRP is the major driver for complex formation and phosphocholine can disrupt the complexes to reverse their inhibitory effects on phagocytosis and bacterial clearance. Increased formation of CRP-VLDL complexes is therefore harmful and could be a novel target for therapy in sepsis. Copyright © 2020 by The American Association of Immunologists, Inc.Citrobacter rodentium colonizes at the colon and causes mucosal inflammation in mice. Previous studies have revealed the importance of the innate and adaptive immune response for controlling C. rodentium infection. In the present study, we examined the role of T follicular helper (Tfh) cells in intestinal C. rodentium infection using mice with Bcl6 deficiency in T cells. Tfh cells were absolutely required at the late, but not the early, phase to control infection. Compared with control mice, we observed systemic pathogen dissemination and more severe colitis in Tfh-deficient mice. Furthermore, the susceptibility of Tfh-deficient mice correlated with an impaired serum IgG1 response to infection, and serum Abs from infected wild-type mice protected Tfh-deficient mice from infection. The transfer of wild-type Tfh cells also restored the levels of IgG1 and led to effective clearance of the pathogens in Tfh-deficient mice. Moreover, during C. rodentium infection, IL-21- and IL-4-producing Tfh cells were increased obviously in wild-type mice, correlating with IgG1 as the major isotype in germinal center B cells. Taken together, our work highlights the requirement and the function of Tfh cells in regulating humoral response for the host protection against C. rodentium infection. Copyright © 2020 by The American Association of Immunologists, Inc.Central tolerance prevents autoimmunity, but also limits T cell responses to potentially immunodominant tumor epitopes with limited expression in healthy tissues. In peripheral APCs, γ-IFN-inducible lysosomal thiol reductase (GILT) is critical for MHC class II-restricted presentation of disulfide bond-containing proteins, including the self-antigen and melanoma Ag tyrosinase-related protein 1 (TRP1). The role of GILT in thymic Ag processing and generation of central tolerance has not been investigated. We found that GILT enhanced the negative selection of TRP1-specific thymocytes in mice. GILT expression was enriched in thymic APCs capable of mediating deletion, namely medullary thymic epithelial cells (mTECs) and dendritic cells, whereas TRP1 expression was restricted solely to mTECs. GILT facilitated MHC class II-restricted presentation of endogenous TRP1 by pooled thymic APCs. Using bone marrow chimeras, GILT expression in thymic epithelial cells (TECs), but not hematopoietic cells, was sufficient for complete deletion of TRP1-specific thymocytes.