Role of group A streptococcal IgG-binding proteins in triggering experimental glomerulonephritis in the rabbit

Our previous studies have indicated that the IgG-binding M-family proteins (IgGBP) of group A streptococci may be involved in eliciting experimental acute poststreptococcal glomerulonephritis (APSGN) in the rabbit. These surface proteins were also found to trigger production of anti-IgG, which might conceivably act to enhance renal deposition of immune complexes (IC). In the present study, a clinical isolate of serotype M22 (strain AL168), an isogenic double mutant deficient for both the IgGBPs Mrp and Emm, as well as mutants deficient in only one of the proteins were tested for capacity to induce glomerulonephritis. Streptococci to be used for injecting rabbits were heat-killed. Surface-bound IgG was removed by 1 M KSCN and cells were then repeatedly washed in PBS before use. Rabbits were injected intravenously with 109 cells three times a week for 8 weeks and, following one month of rest, for another 6 weeks. Deposits of IgG and C3 as well as induced chemokines TNF-alpha, IL-1beta and IL-6 were traced in cryostat sections using specific antibodies and appropriate peroxidase-labelled anti-antibodies. In four rabbits immunized with the double mutant strain, no deposits were found, and as examined by TEM, only subtle and transient renal changes were observed. In contrast, the original strain AL168 induced pronounced inflammatory and degenerative glomerular changes in all four rabbits injected, and deposits of TNF-alpha, IL-1beta and IL-6 were found in mesangial and endothelial cells. Similar deposits and glomerular changes were seen in all eight rabbits injected with the mrp-emm+ mutant and in four out of seven animals receiving the mrp+emm- mutant. There was a highly significant correlation between high levels of circulating anti-IgG and development of APSGN. These results confirm an important role of streptococcal IgGBP in triggering experimental APSGN as earlier proposed by our group.     

Changes in Anti-SARS-CoV-2 IgG Subclasses over Time and in Association with Disease Severity

IgG is the most prominent marker of post-COVID-19 immunity. Not only does this subtype mark the late stages of infection, but it also stays in the body for a timespan of at least 6 months. However, different IgG subclasses have different properties, and their roles in specific anti-COVID-19 responses have yet to be determined. We assessed the concentrations of IgG1, IgG2, IgG3, and IgG4 against different SARS-CoV-2 antigens (N protein, S protein RBD) using a specifically designed method and samples from 348 COVID-19 patients. We noted a statistically significant association between severity of COVID-19 infection and IgG concentrations (both total and subclasses). When assessing anti-N protein and anti-RBD IgG subclasses, we noted the importance of IgG3 as a subclass. Since it is often associated with early antiviral response, we presumed that the IgG3 subclass is the first high-affinity IgG antibody to be produced during COVID-19 infection.     

Structure,Mechanical and Magnetic Properties of Selective Laser Melted Fe-Si-B Alloy

Original 1CP powder was studied and it was founded that powder material partially consists of the amorphous phase, in which crystallization begins at 450 °C and ends at 575 °C. Selective laser melting parameters were investigated through the track study, and more suitable ones were found: laser power P = 90, 120 W; scanning speed V = 1200 mm/s. Crack-free columnar elements were obtained. The sample obtained with P = 90 W, contains a small amount of amorphous phase. X-ray diffraction of samples shows the presence of α-Fe(Si) and Fe₂B. SEM-image analysis shows the presence of ordered Fe₃Si in both samples. Annealed samples show 40% less microhardness; an annealed sample containing amorphous phase shows higher soft-magnetic properties: 2.5% higher saturation magnetization, 35% higher residual magnetization and 30% higher rectangularity coefficient.     

Discitis associated with pregnancy and spinal anesthesia.

Discitis (inflammation of the intervertebral disk) most commonly develops as a rare complication of bacterial infection or chemical or mechanical irritation during spine surgery (1) with a postoperative incidence of 1%-2.8% (2). It is also a complication of discography-the intradiscal injection of saline or contrast material (3). The incidence of postdiscography discitis is 1%-4% (3); no cases have been reported when prophylactic antibiotics have been used, supporting the theory of bacterial contamination (3). Although it is controversial whether discitis can be caused by an aseptic or infectious process, recent data suggest that persistent discitis is almost always bacterial (4). Honan et al. (5) reported 16 cases of spontaneous discitis and reviewed another 52 patients from the literature. In their series, patients tended to have one or more comorbid conditions, such as diabetes, vertebral fracture, or a preexisting spine injury. Spontaneous discitis has also been associated with advanced age, IV drug abuse, IV access contamination, urinary tract infection, and immunocompromised states (5,6). No cases of infectious discitis associated with pregnancy and spinal anesthesia have been reported in the English literature. Discitis presents as spasmodic pain in the back that may be referred to the hips or groin (7). The pain may radiate to the lower extremities. The erythrocyte sedimentation rate is usually increased. Radiological changes in discitis include narrowing of the intervertebral disk space, vertebral sclerosis, and erosion of the end plates. The best diagnostic measure may be magnetic resonance imaging (MRI) or a combination of bone and gallium scanning (2). The mainstay for discitis treatment is pain control and antibiotics; surgical intervention is usually not required. Complications of discitis include intervertebral fusion, epidural abscess, and paralysis. IMPLICATIONS: This is a case report of a disk infection (discitis) caused by the bacteria, Streptococcus bovis after spinal anesthesia for cesarean delivery. S. bovis rarely causes discitis, and spinal anesthesia for labor and delivery has not been reported as a cause of discitis.     

Free-standing Li+-conductive films based on PEO–PVDF blends

Solid electrolytes are of high interest for the development of advanced electrochemical energy storage devices with all-solid-state architectures. Here, we report the fabrication of the electrolyte membranes based on LiTFSI (LiN(CF₃SO₂)₂) and PEO–PVDF blends with improved properties. We show that addition of PVDF enables preparation of free-standing films of the compositions within the so called “crystallinity gap” of the LiTFSI–PEO system known to provide high ion conductivity. We show that optimal PVDF content enables preparation of the films with reasonable elastic modulus and high ionic conductivity of about 0.3 mS cm⁻¹ at 60 °C and about 0.1 mS cm⁻¹ at room-temperature. Combining FTIR spectroscopy, XRD and DSC measurements we show that a noticeable fraction of PVDF remains crystalline and enhances the mechanical properties of the material, and at the same time it additionally promotes LiTFSI dissociation and disordering. Density functional theory calculations showed that the Li⁺–PEO–PVDF complexation energy magnitude is almost as high as that of Li–PEO complexes, thus the salt dissociation ability can be retained in spite of the introduction of the substantial amounts of PVDF required for mechanical stability.

Addition of PVDF to LiTFSI–PEO solid electrolytes enables preparation of free-standing films with the compositions within the so called “crystallinity gap” of LiTFSI–PEO system. Such films possess ionic conductivity of about 0.3 mS cm⁻¹ at 60 °C.