key: cord-0874219-tmog8u6r
authors: Farcet, Maria R; Karbiener, Michael; Schwaiger, Julia; Ilk, Reinhard; Kreil, Thomas R
title: Rapidly Increasing SARS-CoV-2 Neutralization by Intravenous Immunoglobulins Produced from Plasma Collected During the 2020 Pandemic
date: 2021-03-16
journal: J Infect Dis
DOI: 10.1093/infdis/jiab142
sha: e838fec0f3938fbec56c07d31705e6c360eeecf5
doc_id: 874219
cord_uid: tmog8u6r

Immunoglobulin (IG) lots (N=176) released since March 2020 were tested for SARS-CoV-2 neutralizing antibodies, with first positive results for September 2020 lots, mean = 1.7 IU/ml, 46% of lots positive. From there, values steadily increased, in correlation with the cumulative COVID-19 incidence, to reach a mean of 31.2 IU/ml and 93% of lots positive by January 2021. Extrapolating the correlation, IGs could reach an anti-SARS-CoV-2 potency of ~345 IU/ml by July 2021. At that stage, prophylactic IG treatment for primary/secondary immunodeficiency could contain similar doses of anti-SARS-CoV-2 as convalescent plasma which is used for treatment of COVID-19.

A c c e p t e d M a n u s c r i p t pandemic did not neutralize SARS-CoV-2 [1] .

By the end of 2020, close to 100 million COVID-19 cases had been reported globally, with almost a quarter of them in the US alone [2] . The US is quantitatively the most important origin of plasma for fractionation [3] , and thus an increasing proportion of the plasma supply will be collected from donors post COVID-19, plasma that is now expected to also carry antibodies to SARS-CoV-2.

Here, we report the results from an investigation into the seroconversion of the US supply of plasma for fractionation, through testing of IVIGs derived exclusively from US plasma for SARS-CoV-2 neutralization, which revealed rapidly increasing antibody titers which correlated with cumulative COVID-19 incidence. Together with the characterization of SARS-CoV-2 neutralizing antibody (nAb) titers in a large collection of COVID-19 convalescent plasma (CP) donations, this permits a near-term projection of potentially A c c e p t e d M a n u s c r i p t protective SARS-CoV-2 antibody levels in future IG lots, particularly when used in a prophylactic setting for substitution therapy.

A total of 176 IVIG lots (Gammagard Liquid; Baxter Healthcare Corp., Westlake Village, CA) released between March 2020 and January 2021 from plasma collected by plasmapheresis (source plasma) in the US were analyzed. For a subset of 12 of these IVIG lots, information about the dates of plasma collection was obtained.

438 COVID-19 CP samples collected between March and July 2020 were obtained from Austrian (n = 300) and US (n = 138) plasma donation centers (BioLife). The samples originated from donors who had PCR-confirmed SARS-CoV-2 infections or who described a disease progression consistent with COVID-19 and for which SARS-CoV-2 neutralization was confirmed. Information on disease severity was requested from each donor. Donors signed informed consent.

SARS-CoV-2 and HCoV-229E neutralizing antibody (nAb) titers were determined using materials and methods previously reported [1] . Briefly, 2-fold serially diluted samples were incubated with equal volumes of SARS-CoV-2 (strain "BavPat1/2020", Charité Berlin, Germany) or HCoV-229E (for IVIG samples, Cat. no. VR-740, ATCC, Rockville, MD) at SARS-CoV-2 detection limit in IVIG: ≤ 1:2) was determined using the Spearman-Kärber formula, and the calculated neutralization titer for 50% of the wells reported as 1:X. For further analyses, samples with a neutralization titer below the detection limit were assigned a value of 0.5x the detection limit. The National Institute of Biological Standards and Control (NIBSC, Potters Bar, UK) WHO International Standard 20/136, for which a potency in international units has recently been assigned [4] , was included in the study and the concentration of SARS-CoV-2 nAbs therefore reported in IU/ml.

Testing was done using a fully validated analytical method (for SARS-CoV-2 nAbs) or a controlled assay that included several validity criteria, i.e. confirmatory titration of input virus infectivity and cell viability (for HCoV-229E nAbs).

Overall COVID-19 incidence in the US was taken from the Centers for Disease Control and Prevention (CDC) COVID data tracker [2] . Data analysis and visualization was done using Mean SARS-CoV-2 antibody values for IVIG lots released in a month were correlated against the cumulative incidence of COVID-19 in the US that was recorded 6 months prior to IVIG release, e.g. the mean antibody potency measured for IVIG lots released in September 2020 was correlated against cumulative COVID-19 incidence in the US in March 2020. A log-transformed linear model and a polynomial regression model indicated comparable quality of fit and both were used to calculate an extrapolation beyond the period for which A c c e p t e d M a n u s c r i p t antibody measurements were made. The slope at the highest observed cumulative incidence (i.e. July 2020; 1.39%) was used for extending the models in a linear manner.

preparations SARS-CoV-2 nAbs were undetectable for IVIG lots released to the market between March and August 2020 (n = 63). For IVIG lots released in September 2020, 12 of 26 lots (46%) were seropositive with a mean SARS-CoV-2 nAb concentration of 1.7 IU/ml ( Figure 1A) . HCoV-229E nAb titers of the same IVIG lots remained at similar levels throughout the period surveyed ( Figure 1A ) and the observed variations in HCoV-229E nAb titers were similar to previously observed ranges [1] .

For the first 12 IVIG lots that contained measurable SARS-CoV-2 nAbs, the time of collection for the several thousand plasma units used for production was analyzed. On average, plasma was collected six months before IVIG lot release. Thus, the cumulative incidence as the underlying cause for the seroprevalence in any given month would be expected to determine the level of antibodies present in IVIG lots released six months later.

The low SARS-CoV-2 antibody content of IVIG lots released in September 2020 would thus on average be derived from plasma collected in March 2020, when the cumulative COVID-19 incidence was 0.06% of the US population ( Figure 1A ). By July 2020, the cumulative A c c e p t e d M a n u s c r i p t incidence had increased to 1.39%, i.e. about 20-fold, and similarly the mean SARS-CoV-2 antibody concentration increased from 1.7 IU/ml for September 2020 IVIG lots, to 31.2 IU/ml for IVIG lots released in January 2021 ( Figure 1A) . Based on the increasing cumulative COVID-19 incidence since August 2020, an estimation of SARS-CoV-2 nAb concentrations in future IVIG lots is possible ( Figure 1B) . Given a cumulative incidence of 7.94% in January 2021, IG lots to be released in July 2021 can be expected to contain a mean SARS-CoV-2 nAb concentration of around 345 IU/ml ( Figure 1B) . campaigns under way at this moment, approximately 9.6% of the US population has already been vaccinated by the end of January 2021 [2] . Vaccine-induced antibodies will thus further increase the anti-SARS-CoV-2 potency of future lots of IGs, and based on the current cumulative incidence of 7.94% in addition to a 9.6% vaccination rate, and higher mRNA vaccine-induced antibody titers than post-COVID [5, 6] , the anti-SARS-CoV-2 potency of future IG products may potentially be higher than the SARS-CoV-2 potency extrapolated here ( Figure 1B ).

To date, the level of SARS-CoV-2 neutralizing antibody titers required in IG to provide protection against COVID-19 has not been determined. A comparison of the antibody potency contained in CP, to those expected in IG soon may provide for some perspective.

In a large cohort of COVID-19 convalescents, a median anti-SARS-CoV-2 potency of 132 IU/ml was determined (Figure 2 ). The original US FDA emergency use authorization for transfusion of CP required use of plasma at a potency of above the median, as determined by a high throughput binding assay [7, 8] . The mean neutralization potency of above median units of the cohort of samples tested here is 437 IU/ml. Joyner et al. [7] did, however, report significantly better clinical success when using CP above the 80 th percentile, the mean of This prospect is of particular importance for PID patients, for whom a 10-fold higher COVID-19 mortality rate has been reported [11] . The above calculations are quite conservative, as in the US already now the proportion of vaccinated individuals has surpassed those with post COVID-19, a trend that can be expected to accelerate in the months to come.

In addition, currently available data indicate superior levels of SARS-CoV-2 antibodies after mRNA-based vaccines as currently in use in the US [5, 6] . Cumulatively, these circumstances would appear to support rapidly increasing levels of SARS-CoV-2 antibodies in IG, so that IG-mediated protection against COVID-19 for regularly substituted PID / SID seems quite possible. More research to confirm the extrapolations from this study is currently under way.

The ongoing emergence of SARS-CoV-2 variants will add further complexity to the anti-SARS-CoV-2 potency of IG, as initially these virus variants may be less well neutralized by antibodies generated against earlier virus strains. At a later point though, antibodies against newer virus variants will also appear in these IG preparations.

For COVID-19 treatment, rather than prophylaxis, a hyper-IVIG manufactured exclusively from plasma of COVID-19 convalescent donors is currently under evaluation in a phase III clinical trial [12] . M a n u s c r i p t A c c e p t e d M a n u s c r i p t 

No SARS-CoV-2 Neutralization by Intravenous Immunoglobulins produced from Plasma Collected Before the 2020 Pandemic

CDC) COVID Data Tracker; available at covid.cdc.gov/covid-data-tracker/#datatracker-home (last accessed

Regulation of plasma for fractionation in the United States

Establishment of the WHO International Standard and Reference Panel for anti-SARS-CoV-2 antibody

An mRNA vaccine against SARS-CoV-2 -preliminary report

Safety and immunogenicity of two RNA-based COVID-19 vaccine candidates

Convalescent plasma antibody levels and the risk of death from COVID-19

Letter of Authorization, Reissuance of Convalescent Plasma EUA

Early high-titer plasma therapy to prevent servere COVID-19 in older adults

A randomized trial of convalescent plasma in COVID-19 severe pneumonia

Impact of SARS-CoV-2 pandemic on patients with Primary Immunodeficiency

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A c c e p t e d M a n u s c r i p t