Background: Campylobacter jejuni (C. jejuni) is accountable for more than 400 million cases of gastroenteritis each year and is listed as a high-priority gut pathogen by the World Health Organization (WHO). Although the acute infection of C. jejuni (campylobacteriosis) is commonly treated with macrolides and fluoroquinolones, the emergence of antibiotic resistance among C. jejuni warrants the need for an alternative approach to control campylobacteriosis in humans. To this end, vaccines remain a safe, effective, and widely accepted strategy for controlling emerging and re-emerging infectious diseases. In search of a suitable vaccine against campylobacteriosis, recently, we demonstrated the potential of recombinant Haemolysin co-regulated protein (Hcp) of C. jejuni Type VI secretion system (T6SS) in imparting significant immune-protection against cecal colonization of C. jejuni; however, in the avian model. Since clinical features of human campylobacteriosis are more complicated than the avians, we explored the potential of Hcp as a T6SS targeted vaccine in a murine model as a more reliable and reproducible experimental host to study vaccine-induced immune-protection against C. jejuni. Because C. jejuni primarily utilizes the mucosal route for host pathogenesis, we analyzed the immunogenicity of a mucosally deliverable bioengineered Lactic acid bacteria (LAB), Lactococcus lactis (L. lactis), expressing Hcp. Considering the role of Hcp in both structural (membrane-bound) and functional (effector protein) exhibition of C. jejuni T6SS, a head-to-head comparison of two different forms of recombinant LAB vectors (cell wall anchored and secreted form of Hcp) were tested and assessed for the immune phenotypes of each modality in BALB/c mice.
Results: We show that regardless of the Hcp protein localization, mucosal delivery of bioengineered LAB vector expressing Hcp induced high-level production of antigen-specific neutralizing antibody (sIgA) in the gut with the potential to reduce the cecal load of C. jejuni in mice.
Conclusion: Together with the non-commensal nature of L. lactis, short gut transit time in humans, and the ability to express the heterologous protein in the gut, the present study highlights the benefits of bioengineered LAB vectors based mucosal vaccine modality against C. jejuni without the risk of immunotolerance
Sensing of intracellular Hcp levels controls T6SS expression in Vibrio cholerae
- The type 6 secretion system (T6SS) is a bacterial weapon broadly distributed in gram-negative bacteria and used to kill competitors and predators. Featuring a long and double-tubular structure, this molecular machine is energetically costly to produce and thus is likely subject to diverse regulation strategies that are largely ill defined. In this study, we report a quantity-sensing control of the T6SS that down-regulates the expression of secreted components when they accumulate in the cytosol due to T6SS inactivation. Using Vibrio cholerae strains that constitutively express an active T6SS, we demonstrate that mRNA levels of secreted components, including the inner-tube protein component Hcp, were down-regulated in T6SS structural gene mutants while expression of the main structural genes remained unchanged.
- Deletion of both hcp gene copies restored expression from their promoters, while Hcp overexpression negatively impacted expression. We show that Hcp directly interacts with the RpoN-dependent T6SS regulator VasH, and deleting the N-terminal regulator domain of VasH abolishes this interaction as well as the expression difference of hcp operons between T6SS-active and inactive strains.
- We find that negative regulation of hcp also occurs in other V. cholerae strains and the pathogens Aeromonas dhakensis and Pseudomonas aeruginosa This Hcp-dependent sensing control is likely an important energy-conserving mechanism that enables T6SS-encoding organisms to quickly adjust T6SS expression and prevent wasteful build-up of its major secreted components in the absence of their efficient export out of the bacterial cell.
Assessing COVID-19 Transmission to Healthcare Personnel: the Global ACT-HCP Case-Control Study
Objective: To characterize associations between exposures within and outside the medical workplace with healthcare personnel (HCP) SARS-CoV-2 infection, including the effect of various forms of respiratory protection.
Design: Case-control study.
Setting: Data collected via online survey from international participants.
Participants: 1130 HCP (244 cases with laboratory-confirmed COVID-19, 886 controls healthy throughout the pandemic) from 67 countries not meeting pre-specified exclusion (healthy but not working, missing workplace exposure data, COVID symptoms without lab confirmation).
Methods: Respondents were queried regarding workplace exposures, respiratory protection, and extra-occupational activities. Odds ratios for HCP infection were calculated with multivariable logistic regression and sensitivity analyses controlling for confounders and known biases.
Results: HCP infection was associated with non-aerosol-generating contact with COVID-19 patients (adjusted OR 1.4, 95% CI 1.04-1.9, p=0.03) and extra-occupational exposures including gatherings of ten or more, patronizing restaurants or bars, and public transportation (adjusted ORs ranging 3.1-16.2). Respirator use during aerosol-generating procedures (AGPs) was associated with lower odds of HCP infection (adjusted OR 0.4, 0.2 to 0.8, p=0.005), as was exposure to intensive care and dedicated COVID units, negative pressure rooms, and personal protective equipment (PPE) observers (adjusted ORs ranging 0.4-0.7).
Conclusions: COVID-19 transmission to HCP was associated with medical exposures currently considered lower-risk and multiple extra-occupational exposures, while exposures associated with proper use of appropriate PPE were protective. Closer scrutiny of infection control measures surrounding healthcare activities and medical settings considered lower risk, and continued awareness of the risks of public congregation, may reduce the incidence of HCP infection.
Controls Kit. Baculovirus controls. |
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| K26 | AB Vector LLC | 1 Kit | 295 EUR |
PlasmoTest™ Controls |
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| pt-ctr2 | InvivoGen FR | 200 tests | 122.85 EUR |
Primer Set for PCR Controls |
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| MBS412588-025mL | MyBiosource | 0.25mL | 140 EUR |
Primer Set for PCR Controls |
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| MBS412588-5x025mL | MyBiosource | 5x0.25mL | 430 EUR |
Rat Anti-KLH IgM with controls |
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| KT-568 | Kamiya Biomedical Company | 96 tests | 778 EUR |
Rat Anti-KLH IgG with controls |
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| KT-570 | Kamiya Biomedical Company | 96 tests | 778 EUR |
NATtrol GI Controls (12 x 0.2 mL) |
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| NATGIC-BIO | Zeptometrix | 12 x 0.2 mL | 487 EUR |
NATtrol RP Controls (12 x 0.25 mL) |
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| NATRPC-NNS | Zeptometrix | 12 x 0.25 mL | 501 EUR |
CO‐Oximeter Calibration Verification Controls |
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| CVC223 | RNA Medical | each | 396 EUR |
Spoligotyping Kit with Primers and Controls |
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| IM9701 | Mapmygenome | each | 1620 EUR |
Leptospira IFA IgG Pos/Neg Human Controls |
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| LE-GC | Fuller Laboratories | each | 60 EUR |
Leptospira IFA IgM Pos/Neg Human Controls |
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| LE-MC | Fuller Laboratories | each | 60 EUR |
NATtrol Respiratory Panel 2 (RP2) Controls (Ea) |
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| NATRPC2-BIO | Zeptometrix | Ea | 550.46 EUR |
A549 HCP Control Antigen |
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| F237 | Cygnus Technologies | 50 ul | 308.4 EUR |
E.coli HCP Control Antigen |
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| F417 | Cygnus Technologies | 50 ul | 280.8 EUR |
Coxiella burneti IFA Human IgG Pos/Neg Controls |
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| Q-GC | Fuller Laboratories | each | 60 EUR |
Coxiella burneti IFA Human IgM Pos/Neg Controls |
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| Q-MC | Fuller Laboratories | each | 60 EUR |
Rickettsia typhi IFA IgG Human Pos/Neg Controls |
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| RT-GC | Fuller Laboratories | each | 60 EUR |
Rickettsia typhi IFA IgM Human Pos/Neg Controls |
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| RT-MC | Fuller Laboratories | each | 60 EUR |
HEK 293 HCP Control Antigen |
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| F656 | Cygnus Technologies | 70 ul | 678 EUR |
Zika IgM/IgG Control Pack (IgM,IgG & Negative Controls, 0.25mL) |
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| 0801020 | Zeptometrix | 0.25mL | 66 EUR |
Zika IgM/IgG Control Pack (IgM,IgG & Negative Controls, 0.25mL) |
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| 801020 | Zeptometrix | 0.25mL | 66 EUR |
Selective control of fcc and hcp crystal structures in Au-Ru solid-solution alloy nanoparticles.
Binary solid-solution alloys generally adopt one of three principal crystal lattices-body-centred cubic (bcc), hexagonal close-packed (hcp) or face-centred cubic (fcc) structures-in which the structure is dominated by constituent elements and compositions. Therefore, it is a significant challenge to selectively control the crystal structure in alloys with a certain composition. Here, we propose an approach for the selective control of the crystal structure in solid-solution alloys by using a chemical reduction method.
By precisely tuning the reduction speed of the metal precursors, we selectively control the crystal structure of alloy nanoparticles, and are able to selectively synthesize fcc and hcp AuRu3 alloy nanoparticles at ambient conditions. This approach enables us to design alloy nanomaterials with the desired crystal structures to create innovative chemical and physical properties.