Convalescent Antibodies Infusion in Critically Ill COVID 19 Patients

Overview

The 2019 outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 or COVID 19), which originated in Wuhan, China, has become a major concern all over the world. Convalescent plasma or immunoglobulins have been used as a last resort to improve the survival rate of patients with SARS whose condition continued to deteriorate despite any attempted treatment.. Moreover, several studies showed a shorter hospital stay and lower mortality in patients treated with convalescent plasma than those who were not treated with convalescent plasma. Evidence shows that convalescent plasma from patients who have recovered from viral infections can be used effectively as a treatment of patients with active disease. The use of solutions enriched of antiviral antibodies has several important advantages over the convalescent plasma including the high level of neutralizing antibodies supplied. Plasma-exchange is expensive and requires large volumes of substitution fluid. Albumin is better tolerated and less expensive, but exchanges using albumin solutions increase the risk of bleeding because of progressive coagulation factor depletion. With either albumin or fresh frozen plasma, increasing the risk of cardiovascular instability in the plasma donor and in the recipient, which can be detrimental in a critically ill patient with COVID 19 pneumonia. The aforementioned limitations of plasma therapy can be overcome by using selective apheresis methods, such as double-filtration plasmapheresis (DFPP).DFPP is a modality of plasma purification that performs an initial plasma separation from blood, and the subsequent separation of specific molecules, on the basis of their specific molecular weight (cut-off), by using a fractionation filter. The Fractionation Filter 2A20, because of its membrane sieving cut-off, retains larger molecules and returns plasma along with smaller molecules to the circulation, including the major part of the albumin. The selection of the membrane 2A20 is related to the appropriate Sieving Coefficient for IgG that allows to efficiently collect antibodies from patients which are recovered from COVID-19, with negligible fluid losses and limited removal of albumin. The total amount of antibodies obtained during one DFPP session exceeds by three to four times the total amount provided to recipients with one unit of plasma obtained during one plasma-exchange session from one COVID-19 convalescent donor. This should result in more effective viral inhibition and larger benefit for the patient achieved with one unit of enriched immunoglobulin solution obtained with DFPP than with one unit of plasma obtained with plasma exchange. These observations provide the background for a pilot study aimed to explore whether the infusion of antibodies obtained with one single DFPP procedure from voluntary convalescent donors could offer an effective and safe therapeutic option for critically ill patients with severe coronavirus (COVID-19) pneumonia requiring mechanical ventilation.