Convalescent Antibodies Infusion in COVID 19 Patients

The outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), 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 treatment with pulsed methylprednisolone. 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. Moreover, plasma-exchange is expensive and requires large volumes of substitution fluid 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 use of plasma as a substitution fluid further increases treatment costs and is associated with risk of infections, allergic reactions and citrate-induced hypocalcemia. Albumin is better tolerated and less expensive, but exchanges using albumin solutions increase the risk of bleeding because of progressive coagulation factor depletion.

The aforementioned limitations of plasma therapy can be in part overcome by using selective apheresis methods, such as double-filtration plasmapheresis (DFPP)3. During DFPP, plasma is separated from cellular components by a plasma filter, and is then allowed to pass through a fractionator filter. Depending on the membrane cut-off, the fractionator filter retains larger molecules and returns fluid along with smaller molecules to the circulation. Thus, the selection of a membrane with an appropriate sieving coefficient for IgG allows to efficiently clear autoantibodies in patients with antibody-mediated diseases (e.g., macroglobulinemia, myasthenia gravis and rheumatoid arthritis) with negligible fluid losses and limited removal of albumin and coagulation factors1.

In patients with severe membranous nephropathy and high titer of autoreactive, nephritogenic antibodies against the podocyte-expressed M type phospholipase A2 receptor (PLA2R), DFPP accelerated anti PLA2R depletion4. Measurement of the antibody titer in treated patient and recovered fluid showed that antibody removal was extremely effective and that large part of antibodies was removed during the first DFPP procedure. This therapeutic regimen was safe and well tolerated and easy to apply4. In an ongoing pilot study we found that the same methodological approach can be used to remove circulating antibodies from patients who recovered from COVID 19 and to infuse these antibodies in patients with active viral infection. Treatment was well tolerated and preliminary findings are encouraging. Thus, in this novel pilot study we aim 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 patients with earlier stages of coronavirus (COVID-19) pneumonia requiring oxygen supply without mechanical ventilation.