ABSTRACT
Fowl cholera is an infectious disease that affects both poultry and wild birds, characterized by hemorrhagic and septicemic symptoms, caused by Pasteurella multocida (P. multocida), and leading to substantial economic losses in the poultry sector. The development of genetic engineering vaccines against avian P. multocida encountered early-stage challenges due to the limited availability of effective gene editing tools. Presently, NgAgoDM-enhanced homologous recombination stands as a potent technique for achieving efficient gene knockout in avian P. multocida. Hence, this study employed NgAgoDM-enhanced homologous recombination to target and knockout hyaE (239-359aa), hyaD, hexABC, and hexD, denoted as ΔhyaE (239-359aa), ΔhyaD, ΔhexABC, and ΔhexD, respectively. Additionally, we generated a hyaD recovery strain with two point mutations, designated as mhyaD. Thus, this study systematically examined the impact of capsular synthetic gene clusters on the pathogenicity of P. multocida. Moreover, the study demonstrated the critical role of hyaD activity in the virulence of avian P. multocida. This study offers novel insights for enhancing attenuated vaccines further.
Subject(s)
Pasteurella Infections , Pasteurella multocida , Poultry Diseases , Pasteurella multocida/genetics , Pasteurella multocida/pathogenicity , Animals , Pasteurella Infections/veterinary , Pasteurella Infections/microbiology , Virulence/genetics , Poultry Diseases/microbiology , Bacterial Vaccines/immunology , Bacterial Vaccines/genetics , Homologous Recombination , Vaccines, Attenuated/immunology , Vaccines, Attenuated/genetics , Gene Knockout Techniques , Chickens/microbiology , Bacterial Proteins/genetics , Bacterial Proteins/metabolism , Birds/microbiology , Multigene Family , Virulence Factors/genetics , Poultry/microbiologyABSTRACT
An enhanced ultraviolet (UV) nanosecond laser milling cutting method is innovatively adopted to cut carbon fiber reinforced plastic (CFRP) composites. This paper aims to achieve a more efficient and facile way to cut the thicker sheet cutting mode. The technology of UV nanosecond laser milling cutting is studied in detail. The effects of milling mode and filling spacing on the cutting effect are explored in milling mode cutting. Cutting with the milling method can obtain a smaller heat-affected zone at the slit entrance and a shorter effective processing time. When the longitudinal milling method is adopted, the machining effect of the lower side of the slit is better when the filling spacing is 20 µm and 50 µm, with no burr or other defects. Additionally, the filling spacing below 50 µm can obtain a better machining effect. The coupled photochemical and photothermal effects of UV laser cutting CFRP are elucidated, and the experiments verify this phenomenon successfully. Overall, it is anticipated that this study can offer a practical reference for UV nanosecond laser milling cutting CFRP composites and make contributions to military fields.
ABSTRACT
A tailored 2D finite element model (FEM) is proposed to describe the temperature distribution and stress distribution by the UV nanosecond pulsed laser cutting of carbon fiber reinforced plastic (CFRP) composites. This model coupled thermodynamic and thermal stress and considers the heat conduction, thermal stress, and heat flux effects during the UV laser cutting of CFRP composites. In this study, the main mechanism of UV laser cutting of CFRP is elucidated, such as pressure gradient, plasma, and vaporization effects. The temperature field and stress field in a single pulse period are successfully simulated based on these theoretical models. We believe that this research will supply a theoretical reference for the UV laser cutting of CFRP composites and pave the way for applications in the aerospace industry in the future.
ABSTRACT
Streptococcus suis (S. suis) is an emerging zoonotic pathogen that can cause multiple diseases, including streptococcal toxic shock-like syndrome (STSLS). The S. suis SC-19 strain could cause NOD-like receptor thermal protein domain-associated protein 3 (NLRP3) inflammasome hyperactivation, then induce a cytokine storm and STSLS. Although IL-18 is the downstream effector of NLRP3 signaling, the role of IL-18 signaling on STSLS remains to be elucidated. Thus, il18r1 gene knockout mice were constructed and challenged with the SC-19 strain. Alleviated clinical signs and tissue damages, as well as improved survival were observed in il18r-/- mice compared with the WT mice post-SC-19 challenge. Meanwhile, an obvious decrease in the inflammatory cytokine levels in blood was observed in the il18r-/- mice infected with SC-19. Therefore, IL-18, the downstream effector of NLRP3 inflammasome activation, was responsible for the cytokine storm and STSLS development caused by S. suis, suggesting that IL-18/IL-18Rα signaling could serve as a new target for STSLS.