Central tolerance shapes the neutralizing B cell repertoire against a persisting virus in its natural host

Viral mimicry of host cell structures has been postulated to curtail the B cell receptor (BCR) repertoire against persisting viruses through tolerance mechanisms. This concept awaits, however, experimental testing in a setting of natural virus–host relationship. We engineered mouse models expressing a monoclonal BCR specific for the envelope glycoprotein of lymphocytic choriomeningitis virus (LCMV), a naturally persisting mouse pathogen. When the heavy chain of the LCMV-neutralizing antibody KL25 was paired with its unmutated ancestor light chain, most B cells underwent receptor editing, a behavior reminiscent of autoreactive clones. In contrast, monoclonal B cells expressing the same heavy chain in conjunction with the hypermutated KL25 light chain did not undergo receptor editing but exhibited low levels of surface IgM, suggesting that light chain hypermutation had lessened KL25 autoreactivity. Upon viral challenge, these IgM $^{low}$ cells were not anergic but up-regulated IgM, participated in germinal center reactions, produced antiviral antibodies, and underwent immunoglobulin class switch as well as further affinity maturation. These studies on a persisting virus in its natural host species suggest that central tolerance mechanisms prune the protective antiviral B cell repertoire

PREVENTION OF UNFAVOURABLE PERINATAL OUTCOMES OF PLACENTAL INSUFFICIENCY AND INTRAUTERINE GROWTH RESTRICTION

Polyetiologicity of placental insufficiency and formation of the intrauterine growth restriction require permanent improvement of approaches to therapy. Magnesium deficit leads to placenta metabolism disturbance, formation of stable psychoemotional distress. Application of magnesium drugs in a complex therapy of placental insufficiency allows in a majority of observations (85%) normalization of hemodynamic values in the system “mother-placenta – fetus”. The problem of antenatal neuroprotection of the fetal brain is an urgent and complex problem of modern obstetrics, which requires performance of further studies

Precision-guided, personalized intrapleural fibrinolytic therapy for empyema and complicated parapneumonic pleural effusions: The case for the fibrinolytic potential

Complicated pleural effusions and empyema with loculation and failed drainage are common clinical problems. In adults, intrapleural fibrinolytic therapy (IPFT) is commonly used with variable results, and therapy remains empiric. Despite the intrapleural use of various plasminogen activators (PAs) - fibrinolysins - for about 60 years, there is no clear consensus about which agent is most effective. Emerging evidence demonstrates that intrapleural administration of PAs is subject to rapid inhibition by PA inhibitor-1 and that processing of fibrinolysins is significantly influenced by other factors, including the levels and quality of pleural fluid DNA. Current therapy for loculation that accompanies pleural infections also includes surgery, which is invasive and for which patient selection can be problematic. Most of the clinical literature published to date has used flat dosing of IPFT in all subjects, but little is known about how that strategy influences the processing of the administered fibrinolysin or how this influences outcomes. We developed a new test of pleural fluids ex vivo, which is called the fibrinolytic potential, in which a dose of a fibrinolysin is added to pleural fluids ex vivo after which the fibrinolytic activity is measured and normalized to baseline levels. Testing in preclinical and clinical empyema fluids reveals a wide range of responses, indicating that individual patients will likely respond differently to flat dosing of fibrinolysins. The test remains under development but is envisioned as a guide for dosing of these agents, representing a novel candidate approach to personalization of IPFT

Fibrin turnover and organization of pleural injury: Bench to bedside

Recent studies have shed new light on the role of the fibrinolytic system in the pathogenesis of pleural organization, including mechanisms by which the system regulates mesenchymal transition of mesothelial cells and how that process affects outcomes of pleural injury. The key contribution of plasminogen activator inhibitor-1 to the outcomes of pleural injury is now better understood as is its role in the regulation of intrapleural fibrinolytic therapy. In addition, mechanisms by which fibrinolysins are processed after intrapleural administration have now been elucidated, informing new candidate diagnostics and therapeutics for pleural loculation and failed drainage. The emergence of new potential interventional targets offers the potential for the development of new and more effective therapeutic candidates

Fibrin turnover and organization of pleural injury: Bench to bedside

Recent studies have shed new light on the role of the fibrinolytic system in the pathogenesis of pleural organization, including mechanisms by which the system regulates mesenchymal transition of mesothelial cells and how that process affects outcomes of pleural injury. The key contribution of plasminogen activator inhibitor-1 to the outcomes of pleural injury is now better understood as is its role in the regulation of intrapleural fibrinolytic therapy. In addition, mechanisms by which fibrinolysins are processed after intrapleural administration have now been elucidated, informing new candidate diagnostics and therapeutics for pleural loculation and failed drainage. The emergence of new potential interventional targets offers the potential for the development of new and more effective therapeutic candidates

Dose dependency of outcomes of intrapleural fibrinolytic therapy in new rabbit empyema models

The incidence of empyema (EMP) is increasing worldwide, generally occurs with pleural loculation and impaired drainage is often treated with intrapleural fibrinolytic therapy (IPFT) or surgery. A number of IPFT options are used clinically with empiric dosing and variable outcomes in adults. To evaluate the mechanisms governing intrapleural fibrinolysis and disease outcomes, rabbit models of Pasteurella multocida and Streptococcus pneumoniae-induced EMP were generated. The animals were treated with either human tissue (tPA) plasminogen activator or prourokinase (scuPA). Rabbit EMP was characterized by the development of pleural adhesions detectable by chest ultrasonography and fibrinous coating of the pleura. Similar to human EMP, rabbits with EMP accumulated sizable; 20-40 ml fibrinopurulent pleural effusions associated with extensive intrapleural organization, significantly increased pleural thickness, suppression of fibrinolytic and plasminogen activating activities and accumulation of high levels of plasminogen activator inhibitor 1, plasminogen and extracellular DNA. IPFT with tPA (0.145 mg/kg) or scuPA (0.5 mg/kg) was ineffective in rabbit EMP (n=9 and 3 for P. multocida and S. pneumoniae, respectively). 2 mg/kg tPA or scuPA IPFT (n=5) effectively cleared S. pneumoniae-induced EMP collections in 24h with no bleeding observed. While intrapleural fibrinolytic activity for up to 40 min after IPFT was similar for effective and ineffective doses of fibrinolysin, it was lower for tPA compared to scuPA treatments. These results demonstrate the similarities between rabbit and human EMP, the importance of pleural fluid PAI-1 activity and levels of plasminogen in the regulation of intrapleural fibrinolysis and illustrate the dose dependency of IPFT outcomes in EMP

Dose dependency of outcomes of intrapleural fibrinolytic therapy in new rabbit empyema models

The incidence of empyema (EMP) is increasing worldwide, generally occurs with pleural loculation and impaired drainage is often treated with intrapleural fibrinolytic therapy (IPFT) or surgery. A number of IPFT options are used clinically with empiric dosing and variable outcomes in adults. To evaluate the mechanisms governing intrapleural fibrinolysis and disease outcomes, rabbit models of Pasteurella multocida and Streptococcus pneumoniae-induced EMP were generated. The animals were treated with either human tissue (tPA) plasminogen activator or prourokinase (scuPA). Rabbit EMP was characterized by the development of pleural adhesions detectable by chest ultrasonography and fibrinous coating of the pleura. Similar to human EMP, rabbits with EMP accumulated sizable; 20-40 ml fibrinopurulent pleural effusions associated with extensive intrapleural organization, significantly increased pleural thickness, suppression of fibrinolytic and plasminogen activating activities and accumulation of high levels of plasminogen activator inhibitor 1, plasminogen and extracellular DNA. IPFT with tPA (0.145 mg/kg) or scuPA (0.5 mg/kg) was ineffective in rabbit EMP (n=9 and 3 for P. multocida and S. pneumoniae, respectively). 2 mg/kg tPA or scuPA IPFT (n=5) effectively cleared S. pneumoniae-induced EMP collections in 24h with no bleeding observed. While intrapleural fibrinolytic activity for up to 40 min after IPFT was similar for effective and ineffective doses of fibrinolysin, it was lower for tPA compared to scuPA treatments. These results demonstrate the similarities between rabbit and human EMP, the importance of pleural fluid PAI-1 activity and levels of plasminogen in the regulation of intrapleural fibrinolysis and illustrate the dose dependency of IPFT outcomes in EMP