Abstract Number: OC 15.1
Meeting: ISTH 2021 Congress
Theme: COVID and Coagulation » COVID and Coagulation, Basic Science
Background: NETs are webs of extracellular DNA that entrap bacteria and potentially viruses. Unfortunately, NET degradation products (NDPs) are toxic, and growing evidence suggests that NDPs contribute to organ damage in COVID-19. We have previously shown that PF4, a platelet-specific chemokine, aggregates NETs, enhancing bacterial capture while protecting NETs from nuclease degradation, thereby limiting NDP release.
Aims: We investigated the effect of PF4 on NET-mediated entrapment and inactivation of coronaviruses.
Methods: Inactivated SARS-CoV was incubated in the absence or presence of PF4 (100 µg/ml) and confocal microscopy was used to quantify aggregate formation. NETs released by neutrophils isolated from healthy human donors, were plated on glass slides and microfluidic channels. These NETs were then incubated with PF4 (10-100 µg/ml) prior to exposure to SARs-CoV-1 or SARs-CoV-2. Some PF4-NETs were treated with KKO, a monoclonal antibody, which binds to PF4:NET complexes, improving their nuclease resistance and limiting NET toxicity. Viral-NETs adhesion was quantified with confocal microscopy and evaluated with scanning electron microscopy (SEM). A plaque forming unit assay was performed to measure the effect of PF4 on the infectivity of the SARs-related coronavirus, murine hepatitis virus (MHV)-1.
Results: Coronaviruses formed aggregates with PF4 (Figure 1A) and adhered to the NET surface in the presence of PF4 as seen on confocal microscopy (Figure 1B) and SEM (Figure 1C). In SEM studies, KKO enhanced virion adhesion to PF4:NETs. PF4 treatment at physiologic concentrations limited MHV-1 infectivity (Figure 2).
Conclusions: Just as with bacteria, PF4 binding enhances NET-mediated capture of coronaviruses, an effect enhanced by KKO. Thus, PF4 released by activated platelets may improve virion entrapment by NETs and limit infectivity, while treatment with PF4 infusions may provide additional clinical benefit. We now plan to assess whether KKO can improve NET entrapment of SARS-CoV-2 in the presence of PF4 as a combination therapy to decrease disease severity in COVID-19.
To cite this abstract in AMA style:
Ishizuka M, Estevez B, Sarkar A, kowalska MA, Rauova L, Poncz M, Gollomp K. Platelet Factor 4 (PF4) Enhances in vitro Neutrophil Extracellular Traps (NET) Capture of Coronaviruses: Clinical and Therapeutic Implications [abstract]. Res Pract Thromb Haemost. 2021; 5 (Suppl 2). https://abstracts.isth.org/abstract/platelet-factor-4-pf4-enhances-in-vitro-neutrophil-extracellular-traps-net-capture-of-coronaviruses-clinical-and-therapeutic-implications/. Accessed March 22, 2024.« Back to ISTH 2021 Congress
ISTH Congress Abstracts - https://abstracts.isth.org/abstract/platelet-factor-4-pf4-enhances-in-vitro-neutrophil-extracellular-traps-net-capture-of-coronaviruses-clinical-and-therapeutic-implications/