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

Abstract

Introduction Patients suffering from primary or secondary immunodeficiency face times of increased insecurity and discomfort in the light of the raging Covid-19 pandemic, not knowing if and to what extend their comorbidities impact a potential Covid-19 course of disease. Furthermore, recently available vaccination options might not be amenable or effective for all patients of this heterogeneous population. Therefore, these patients often rely on passive immunization with plasma-derived, intravenous or subcutaneous immunoglobulin (IVIG/SCIG). Whether the ongoing Covid-19 pandemic and/or the progress in vaccination programs lead to increased and potentially protective titers in plasma-derived immunoglobulins (Ig) indicated e.g. for humoral immunodeficiency remains a pressing question for this patient population. Purpose Here we investigated SARS-CoV-2 reactivity of US plasma-derived IVIG/SCIG products from the end of 2020 until 06/2021 as well as in convalescent plasma (CP) from 05/2020 to 08/2020. Methods Final containers of IVIG/SCIG and CP donations were analyzed by commercial ELISA for SARS-CoV-2 S1-RBD IgG as well as microneutralization assay using a patient-derived SARS-CoV-2 (D614G) isolate. Neutralization capacities of 313 plasma single donations and 119 plasma-derived IVIG/SCIG lots were determined. Results obtained from both analytical methods were normalized against the international WHO standard. Finally, based on dense pharmacokinetic profiles of an IVIG preparation from previously published investigations, possible steady-state plasma levels of SARS-CoV-2 neutralization capacities were approximated based on currently measured anti-SARS-CoV-2 potencies in IVIG/SCIG preparations. Results CP donations presented with a high variability with regards to anti-SARS-reactivity in ELISA as well as in neutralization testing. While approximately 50% of convalescent donations were none/low neutralizing, approximately 10% were at or above 1000 IU/ml. IVIG/SCIG lots derived from pre-pandemic plasma donations did not show neutralizing capacities of SARS-CoV-2. Lots produced between 12/2020 and 06/2021, entailing plasma donations after emergence of SARS-CoV-2 showed a rapid and constant increase in anti-SARS-CoV-2 reactivity and neutralization capacity over time. Neutralization capacity increased from a mean of 20 IU/ml in 12/2020 to 505 IU/ml in 06/2021, while lot-to-lot variability was substantial. Pharmacokinetic (PK) extrapolations based on non-compartmental superposition principles using steady-state reference profiles from previously published PK investigations on IVIG in PID, yielded potential steady-state trough plasma levels of 16 IU/ml based on the average final container concentration from 05/2021 with 216 IU/ml. Maximum extrapolated trough levels could reach 64 IU/ml based on the latest maximal final container potency tested in 06/2021. Conclusions SARS-CoV-2 reactivity and neutralization capacity in IVIG/SCIG produced from US plasma rapidly and in part exponentially increased in the first half of 2021. The observed increase of final container potencies is likely trailing the serological status of the US donor population in terms of Covid-19 convalescence and vaccination by at least 5 months due to production lead times and should in principle continue at least until fall 2021. In summary, the data support rapidly increasing levels of SARS-COV-2 antibodies in IVIG/SCIG products implicating that a certain level of protection could be possible against COVID-19 for regularly substituted PID/SID patients. Nevertheless, more research to confirm, which plasma levels are needed for protection against SARS-CoV-2 infection of immune-compromised patients is still needed. Patients with humoral immunodeficiency rely on plasma-derived immunoglobulin for passive immunization against numerous pathogens. Plasma-derived immunoglobulins contain increasing SARS-CoV-2 neutralization capacities with ongoing Covid-19 pandemic and vaccination campaigns. Plasma-derived immunoglobulin in prophylactic use for immunodeficient patients could potentially aid against SARS-CoV-2 infection in the future.