SARS-CoV-2 Neutralization in Convalescent Plasma and Commercial Lots of Plasma-Derived Immunoglobulin.

People with deficiencies in their immune system often have an insufficient antibody response to antigens such as bacteria, viruses, or vaccines. These patients therefore often receive antibodies from healthy people to replace the missing antibodies and build a first line of defense against infections. These antibodies (also called immunoglobulins [Ig]) are prepared from plasma, the liquid fraction of the blood without cells, of healthy donors. This plasma is then split up during pharmaceutical production into its protein components. One of these is immunoglobulin G (IgG), which is the protein family that neutralizes/inactivates infectious agents as well as marks these infectious agents so they can be recognized by other parts of the immune system. With the ongoing COVID-19 pandemic and the severe to fatal outcomes for certain patient groups, especially people with impaired immunity, these patients and their physicians are interested in whether their antibody replacement therapy also confers protection against SARS-CoV-2 infection. We analyzed the capability of plasma-derived Ig lots to (i) recognize SARS-CoV-2 protein by ELISA method as well as (ii) neutralize SARS-CoV-2 by neutralization studies using the actual virus under biosafety level 3 (BSL-3) conditions. Here we show increasing anti-SARS-CoV-2 activity over time of manufactured Ig lots produced between December 2020 and June 2021. The most recent lots had a neutralizing activity of up to 864 IU/mL. Considering that the US represents Octapharma's main plasma source, the progress in vaccination levels together with the evolution of the COVID-19 pandemic in this country suggests that the intravenous or subcutaneous immunoglobulin (IVIG/SCIG) neutralization capacities against SARS-CoV-2 might still increase and could potentially reach a level where antibody plasma concentrations in the patient confer immune protection.