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Background and objectives: Timely detection of SARS-CoV-2 infection with subsequent contact tracing and rapid isolation are considered critical to containing the pandemic, which continues with the emergence of new variants. Hence, there is an ongoing need for reliable point-of-care antigen rapid diagnostic tests (Ag-RDT). This report describes the development, evaluation, and analytical sensitivity of the diagnostic performance of the InteliSwab® COVID-19 Rapid Test. Methods: Samples from 165 symptomatic subjects were tested with InteliSwab® and the results were compared to RT-PCR to determine the antigen test performance. The analytical sensitivity of InteliSwab® for the detection of different variants was assessed by limit of detection (LOD) determination using recombinant nucleocapsid proteins (NPs) and testing with virus isolates. Western immunoblot independently confirmed that each monoclonal Ab is capable of binding to all variants tested thus far. Results: The overall positivity rate by RT-PCR was 37% for the 165 symptomatic subjects. Based on RT-PCR results as the reference standard, InteliSwab® showed clinical sensitivity and specificity of 85.2% (95% CI, 74.3–92.0%) and 98.1% (95% CI, 93.3–99.7%), respectively. The overall agreement was 93.3% (Kappa index value 0.85; 95% CI, 0.77–0.74) between RT-PCR and InteliSwab® test results. Furthermore, the evaluation of analytical sensitivity for different SARS-CoV-2 variants by InteliSwab® was comparable in the detection of all the variants tested, including Omicron subvariants, BA.4, BA.5, and BQ.1. Conclusions: Due to the surge of infections caused by different variants from time to time, there is a critical need to evaluate the sensitivity of rapid antigen-detecting tests for new variants. The study findings showed the robust diagnostic performance of InteliSwab® and analytical sensitivity in detecting different SARS-CoV-2 variants, including the Omicron subvariants. With the integrated swab and excellent sensitivity and variant detection, this test has high potential as a point-of-care Ag-RDT in various settings when molecular assays are in limited supply and rapid diagnosis of SARS-CoV-2 is necessary. [ABSTRACT FROM AUTHOR]

Bacterial products such as toxins can interfere with a variety of cellular processes, leading to severe human diseases. Clostridium difficile toxins, TcdA and TcdB are the primary contributing factors to the pathogenesis of C. difficile-associated diseases (CDAD). While the mechanisms for TcdA and TcdB mediated cellular responses are complex, it has been shown that these toxins can alter chemotactic responses of neutrophils and intestinal epithelial cells leading to innate immune responses and tissue damages. The effects of C. difficile toxins on the migration and trafficking of other leukocyte subsets, such as T lymphocytes, are not clear and may have potential implications for adaptive immunity. We investigated here the direct and indirect effects of TcdA and TcdB on the migration of human blood T cells using conventional cell migration assays and microfluidic devices. It has been found that, although both toxins decrease T cell motility, only TcdA but not TcdB decreases T cell chemotaxis. Similar effects are observed in T cell migration toward the TcdA- or TcdB-treated human epithelial cells. Our study demonstrated the primary role of TcdA (compared to TcdB) in altering T cell migration and chemotaxis, suggesting possible implications for C. difficile toxin mediated adaptive immune responses in CDAD. [ABSTRACT FROM AUTHOR]

Our previous work has shown that C3H/HeN and C57BL/6 mice have differential susceptibility to Chlamydia trachomatis mouse pneumonitis ( C. muridarum) lung infection. C3H/HeN (H-2k) mice were found to be highly susceptible to C. muridarum infection with higher mortality and more severe morbidity compared to C57BL/6 (H-2b) mice. To examine the role of major histocompatibility complex (MHC) genes on host resistance to chlamydial lung infection, we compared MHC congenic mice, B6.H2k [C57BL/6 background, C3H MHC (H-2k)] and C3H.H2b [C3H/HeN background, C57BL/6 MHC (H-2b)] and their corresponding wild type C57BL/6 mice and C3H/HeN mice, respectively, in susceptibility to C. muridarum infection. We found that B6.H2k, C3H.H2b and C3H/HeN mice are more susceptible to chlamydial lung infection compared to the wild type C57BL/6 mice by showing more serious body weight loss, higher in vivo chlamydial growth and more severe pathologic changes. Congenic B6.H2k mice showed significantly lower levels of IL-12 and IFN-γ production compared to C57BL/6 as well as C3H/HeN and C3H.H2b mice. One the other hand, although congenic C3H.H2b mice displayed similar cytokine response to C57BL/6 mice, they were highly susceptible to C. muridarum infection. Overall, the results suggest that protection against chlamydial lung infection is both MHC and non-MHC gene dependent, and that the interaction between MHC and non-MHC elements may contribute to host resistance to chlamydial infection. [ABSTRACT FROM AUTHOR]

Dendritic cells (DC) play a key role in establishing protective adaptive immunity in intracellular bacterial infections, but the cells influencing DC function in vivo remain unclear. In this study, we investigated the role of NK cells in modulating the function of DC using a murine Chlamydia infection model. We found that the NK cell-depleted mice showed exacerbated disease after respiratory tract Chlamydia muridarum infection, which was correlated with altered T cell cytokine profile. Furthermore, DC from C. muridarum-infected NK-depleted mice (NK-DC) exhibited a less mature phenotype compared with that of DC from the infected mice without NK depletion (NK+DC). NK-DC produced significantly lower levels of both IL-12 and IL-10 than those of NK+DC. Moreover, NK-DC showed reduced ability to direct primary and established Ag-specific Th1 CD4+ T cell responses in DC-T coculture systems. More importantly, adoptive transfer of NK-DC, in contrast to NK+DC, failed to induce type 1 protective immunity in recipients after challenge infection. Finally, NK cells showed strong direct enhancing effect on IL-12 production by DC in an NK-DC coculture system, which was partially reduced by blocking NKG2D receptors signaling and virtually abolished by neutralizing IFN-γ activity. The data demonstrate a critical role of NK cells in modulating DC function in an intracellular bacterial infection. [ABSTRACT FROM AUTHOR]

Background and Objectives: Timely detection of SARS-CoV-2 infection with subsequent contact tracing and rapid isolation are considered critical to containing the pandemic, which continues with the emergence of new variants. Hence, there is an ongoing need for reliable point-of-care antigen rapid diagnostic tests (Ag-RDT). This report describes the development, evaluation, and analytical sensitivity of the diagnostic performance of the InteliSwab ® COVID-19 Rapid Test. Methods : Samples from 165 symptomatic subjects were tested with InteliSwab ® and the results were compared to RT-PCR to determine the antigen test performance. The analytical sensitivity of InteliSwab ® for the detection of different variants was assessed by limit of detection (LOD) determination using recombinant nucleocapsid proteins (NPs) and testing with virus isolates. Western immunoblot independently confirmed that each monoclonal Ab is capable of binding to all variants tested thus far., Results: The overall positivity rate by RT-PCR was 37% for the 165 symptomatic subjects. Based on RT-PCR results as the reference standard, InteliSwab ® showed clinical sensitivity and specificity of 85.2% (95% CI, 74.3-92.0%) and 98.1% (95% CI, 93.3-99.7%), respectively. The overall agreement was 93.3% (Kappa index value 0.85; 95% CI, 0.77-0.74) between RT-PCR and InteliSwab ® test results. Furthermore, the evaluation of analytical sensitivity for different SARS-CoV-2 variants by InteliSwab ® was comparable in the detection of all the variants tested, including Omicron subvariants, BA.4, BA.5, and BQ.1., Conclusions: Due to the surge of infections caused by different variants from time to time, there is a critical need to evaluate the sensitivity of rapid antigen-detecting tests for new variants. The study findings showed the robust diagnostic performance of InteliSwab ® and analytical sensitivity in detecting different SARS-CoV-2 variants, including the Omicron subvariants. With the integrated swab and excellent sensitivity and variant detection, this test has high potential as a point-of-care Ag-RDT in various settings when molecular assays are in limited supply and rapid diagnosis of SARS-CoV-2 is necessary.

Bacterial products such as toxins can interfere with a variety of cellular processes, leading to severe human diseases. Clostridium difficile toxins, TcdA and TcdB are the primary contributing factors to the pathogenesis of C. difficile-associated diseases (CDAD). While the mechanisms for TcdA and TcdB mediated cellular responses are complex, it has been shown that these toxins can alter chemotactic responses of neutrophils and intestinal epithelial cells leading to innate immune responses and tissue damages. The effects of C. difficile toxins on the migration and trafficking of other leukocyte subsets, such as T lymphocytes, are not clear and may have potential implications for adaptive immunity. We investigated here the direct and indirect effects of TcdA and TcdB on the migration of human blood T cells using conventional cell migration assays and microfluidic devices. It has been found that, although both toxins decrease T cell motility, only TcdA but not TcdB decreases T cell chemotaxis. Similar effects are observed in T cell migration toward the TcdA- or TcdB-treated human epithelial cells. Our study demonstrated the primary role of TcdA (compared to TcdB) in altering T cell migration and chemotaxis, suggesting possible implications for C. difficile toxin mediated adaptive immune responses in CDAD.

Although studies suggest that NKT cell (NKT) activation modulates the function of dendritic cells (DCs) in inducing T cell responses, it is unknown whether this modulating effect is biased to a DC subset. We previously reported that NKT activation could modulate DC function in inducing protective T cell immunity to Chlamydia pneumoniae, an intracellular bacterial infection. In this study, we investigated the effect of NKT activation on DC subsets, using multiple approaches, including gene knockout mice, alpha- galactosylceramide stimulation, adoptive transfer of invariant NKT (iNKT), and functional analysis of DC subsets in both in vitro and in vivo settings. We found a preferential modulating effect of iNKTs on the CD8alpha(+) DC subset. Specifically, we found that iNKT-deficient mice, compared with wild-type (WT) mice, showed reduced CD8alpha(+) DC expansion with lower CD40 expression and IL-12 production, whereas enhancing iNKT activation in WT mice or adoptive transfer of iNKTs to Jalpha18(-/-) mice resulted in increased function of CD8alpha(+) DCs in inducing type 1 immune responses. Further, DC-iNKT coculture experiments showed a direct CD40L-dependent enhancing effect of iNKTs on IL-12p70 production by CD8alpha(+) DCs. More importantly, CD8alpha(+) DCs from Jalpha18(-/-) mice, compared with those from WT mice, showed significantly reduced ability to activate IFN-gamma-producing T cells in vitro and to induce type 1 immunity and protection in vivo. Moreover, a similar CD8alpha(+) DC subset alteration was found in the Jalpha18(-/-) mice following Leishmania major infection. Our data provide the first direct evidence that iNKTs preferentially promote the functional development of a subset of DC to generate protective immunity against infections.

Type I IFNs (IFNIs) have pleiotropic functions in regulating host innate and adaptive immune responses to pathogens. To elucidate the role of IFNIs in host resistance to chlamydial infection in vivo, we compared IFN-alpha/beta receptor knockout (IFNAR(-/-)) and wild-type control mice in susceptibility to Chlamydia trachomatis mouse pneumonitis (Chlamydia muridarum) lung infection. We found that the IFNAR(-/-) mice were significantly more resistant to C. muridarum infection showing less bacterial burden and bodyweight loss, and milder pathological changes. However, IFN-gamma response, which is believed to be critical in host defense against chlamydial infection, was similar between the wild-type and IFNAR(-/-) mice. More importantly, TUNEL analysis showed less macrophage apoptosis in IFNAR(-/-) mice, which was consistent with lower expressions of IFNI-induced apoptotic factors, TRAIL, Daxx, and PKR. Furthermore, depletion of lung macrophages with dichloromethylene diphosphonate-liposome significantly increased the susceptibility of the IFNAR(-/-) mice to C. muridarum, confirming the importance of macrophages. Overall, the data indicate that IFNIs play a promoting role in C. muridarum lung infection, largely through increase of local macrophage apoptosis.

Our previous work has shown that C3H/HeN and C57BL/6 mice have differential susceptibility to Chlamydia trachomatis mouse pneumonitis (C. muridarum) lung infection. C3H/HeN (H-2(k)) mice were found to be highly susceptible to C. muridarum infection with higher mortality and more severe morbidity compared to C57BL/6 (H-2(b)) mice. To examine the role of major histocompatibility complex (MHC) genes on host resistance to chlamydial lung infection, we compared MHC congenic mice, B6.H2k [C57BL/6 background, C3H MHC (H-2(k))] and C3H.H2b [C3H/HeN background, C57BL/6 MHC (H-2(b))] and their corresponding wild type C57BL/6 mice and C3H/HeN mice, respectively, in susceptibility to C. muridarum infection. We found that B6.H2k, C3H.H2b and C3H/HeN mice are more susceptible to chlamydial lung infection compared to the wild type C57BL/6 mice by showing more serious body weight loss, higher in vivo chlamydial growth and more severe pathologic changes. Congenic B6.H2k mice showed significantly lower levels of IL-12 and IFN-gamma production compared to C57BL/6 as well as C3H/HeN and C3H.H2b mice. One the other hand, although congenic C3H.H2b mice displayed similar cytokine response to C57BL/6 mice, they were highly susceptible to C. muridarum infection. Overall, the results suggest that protection against chlamydial lung infection is both MHC and non-MHC gene dependent, and that the interaction between MHC and non-MHC elements may contribute to host resistance to chlamydial infection.