The invention features polypeptides that include variants of plasminogen activator inhibitor 1 (PAI-1) having a reduced ability to bind with vitronectin, having a reduced ability to interact with the PAI-1 clearance receptor LDL receptor-related protein 1 (LRP1), and having the ability to efficiently inhibit neutrophil elastase in the presence of neutrophil extracellular traps (NETS). In some embodiments, a polypeptide of the invention includes PAI-1 variants optionally fused to an Fc domain monomer or moiety. The invention also features pharmaceutical compositions and methods of using the polypeptides to treat diseases and conditions characterized with aberrant neutrophil elastase activity (e.g., Idiopathic Pulmonary Fibrosis).

Disclosed herein, in some embodiments, are modified Serp-1 proteins. The modified Serp-1 protein may include a therapeutic enhancing moiety, and be biologically active. In some cases, the therapeutic enhancing moiety is a water soluble polymer such as polyethylene glycol.

The present invention relates to methods of producing recombinant plasminogen in a mammalian expression system. A method for producing plasminogen, the method comprising (i) providing a host cell comprising a first recombinant polynucleotide encoding plasminogen and a second recombinant polynucleotide encoding a plasminogen activation inhibitor; (ii) culturing said host cell in a suitable culture medium under conditions to effect expression of plasminogen from the first polynucleotide and plasminogen activation inhibitor from the second polynucleotide.

COVID-19 results from the infection of the SARS-CoV-2 virus and has spread quickly to literally infected the world. Although coronavirus spike proteins can recognize a broad range of host cell-surface proteins, inhibiting spike protein binding to a survival factor called GRP78 results in a significant reduction in SARS-CoV-2 attachment, entry and replication in lung and kidney cells. This inhibition is accomplished with a novel type of inhibitor that potently blocks the binding of SARS-CoV-2 spike protein and whole virus to surface-bound GRP78. These novel GRP78 inhibitors also down regulate cytokines (IL10, IL6), immune co-inhibitory checkpoint proteins (PD-L1, B7H3, B7H4), and up regulate immune co-stimulatory proteins (MHC-II, CD-86) resulting in the reduction of the immune suppressive nature of infected lung alveolar epithelial cells in vitro and in vivo. Finally, these novel GRP78 inhibitors inhibit the hyperfibrinolysis of infected lung cells by reducing the activation of plasmin on cell surfaces.

In some aspects, the disclosure relates to compositions and methods that are useful for treating inflammatory disorders and conditions. In some embodiments, the disclosure provides recombinant adeno-associated virus (rAAV) vectors and particles encoding a transgene that expresses a Myxomavirus serine proteinase inhibitor (Serp) protein (e.g., Serp-1) and methods for treating inflammatory disorders using the same.

Healthy functional platelets are mass produced. A method for producing platelets, comprising: (1) a culture step of culturing megakaryocytes in a platelet producing medium in the presence of mechanical stress and platelet production promoting factors including MIF, NRDc, IGFBP2, TSP-1, PAI-1, and CCL5, and (2) a harvest step of harvesting the platelets obtained by the culture step; wherein the culture step comprises: (a) a step of promoting a release of the platelet production promoting factors from megakaryocytes by mechanical stress; and/or (b) a step of externally adding platelet production promoting factors including MIF, NRDc, and IGFBP2.

Healthy functional platelets are mass produced. A method for producing platelets, comprising: (1) a culture step of culturing megakaryocytes in a platelet producing medium in the presence of mechanical stress and platelet production promoting factors including MIF, NRDc, IGFBP2, TSP-1, PAI-1, and CCL5, and (2) a harvest step of harvesting the platelets obtained by the culture step; wherein the culture step comprises: (a) a step of promoting a release of the platelet production promoting factors from megakaryocytes by mechanical stress; and/or (b) a step of externally adding platelet production promoting factors including MIF, NRDc, and IGFBP2.

Healthy functional platelets are mass produced. A method for producing platelets, comprising: (1) a culture step of culturing megakaryocytes in a platelet producing medium in the presence of mechanical stress and platelet production promoting factors including MIF, NRDc, IGFBP2, TSP-1, PAI-1, and CCL5, and (2) a harvest step of harvesting the platelets obtained by the culture step; wherein the culture step comprises: (a) a step of promoting a release of the platelet production promoting factors from megakaryocytes by mechanical stress; and/or (b) a step of externally adding platelet production promoting factors including MIF, NRDc, and IGFBP2.

The present invention relates to the use of plasminogen in the treatment and/or elimination of hepatic injury, thereby providing a new therapeutic strategy for treating different types of hepatic injuries.

COVID-19 results from the infection of the SARS-CoV-2 virus and has spread quickly to literally infected the world. Although coronavirus spike proteins can recognize a broad range of host cell-surface proteins, inhibiting spike protein binding to a survival factor called GRP78 results in a significant reduction in SARS-CoV-2 attachment, entry and replication in lung and kidney cells. This inhibition is accomplished with a novel type of inhibitor that potently blocks the binding of SARS-CoV-2 spike protein and whole virus to surface-bound GRP78. These novel GRP78 inhibitors also down regulate cytokines (IL10, IL6), immune co-inhibitory checkpoint proteins (PD-L1, B7H3, B7H4), and up regulate immune co-stimulatory proteins (MHC-II, CD-86) resulting in the reduction of the immune suppressive nature of infected lung alveolar epithelial cells in vitro and in vivo. Finally, these novel GRP78 inhibitors inhibit the hyperfibrinolysis of infected lung cells by reducing the activation of plasmin on cell surfaces.