Asselta, R. | Search bioRxiv

bioRxiv2022

Regulation of inflammation and protection against invasive pneumococcal infection by the long pentraxin PTX3

Streptococcus pneumoniae is a major pathogen in children, elderly subjects and immunodeficient patients. PTX3 is a fluid phase pattern recognition molecule (PRM) involved in resistance to selected microbial agents and in regulation of inflammation. The present study was designed to assess the role of PTX3 in invasive pneumococcal infection. In a murine model of invasive pneumococcal infection, PTX3 was strongly induced in non-hematopoietic (particularly, endothelial) cells. The IL-1{beta}/MyD88 axis played a major role in regulation of the Ptx3 gene expression. Ptx3-/- mice were more susceptible to invasive pneumococcal infection. Although high concentrations of PTX3 had opsonic activity in vitro, no evidence of PTX3-enhanced phagocytosis was obtained in vivo. In contrast, Ptx3-deficient mice showed enhanced recruitment of neutrophils and inflammation. Using P-selectin deficient mice, we found that protection against pneumococcus was dependent upon PTX3-mediated regulation of neutrophil inflammation. In humans, PTX3 genetic polymorphisms were associated with invasive pneumococcal infections. Thus, this fluid phase PRM plays an important role in tuning inflammation and resistance against invasive pneumococcal infection.

immunology↗

bioRxiv2019

Analysis of factor V in zebrafish demonstrates minimal levels needed for hemostasis and risk stratifies human variants

In humans, coagulation factor V (F5) deficiency is a rare, clinically heterogeneous bleeding disorder, suggesting that genetic modifiers may contribute to disease expressivity. Complete loss of mouse F5 results in early lethality. Zebrafish possess many distinct advantages including high fecundity, optical clarity, external development, and homology with the mammalian hemostatic system, features that make it ideal for genetic studies. Our aim was to study the role of F5 in zebrafish through targeted mutagenesis, and apply the model to the study of human F5 variants. CRISPR-mediated genome editing of the zebrafish f5 locus was performed, generating mutants homozygous for a 49 base pair deletion in exon 4. Thrombus formation secondary to vascular endothelial injury was absent in f5-/- mutant embryos and larvae. Despite this severe hemostatic defect, homozygous mutants survived before succumbing to severe hemorrhage in adulthood. Human F5 variants of uncertain significance from patients with F5 deficiency were evaluated, and the causative mutations identified and stratified by their ability to restore thrombus formation in larvae. Analysis of these novel mutations demonstrates variable residual F5 function, with minimal activity being required to restore hemostasis. This in vivo evaluation may be beneficial for patients whose factor activity levels lack correlation with bleeding symptomatology. Furthermore, homozygous mutant embryos tolerate what is a severe and lethal defect in mammals, suggesting the possibility of species-specific factors enabling survival, and allowing further study not possible in the mouse. Identification of these factors or other genetic modifiers could lead to novel therapeutic modalities.\n\nKey PointsO_LIF5 mutant fish embryos tolerate symptoms lethal in mammals but succumb to bleeding in adulthood\nC_LIO_LIAnalysis of human variants demonstrate that all have some residual function and that minimal F5 activity is required to restore hemostasis\nC_LI

genetics↗