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Detection of antibodies against SARS-CoV-2 both in plasma pools for fractionation and in commercial intravenous immunoglobulins produced from plasma collected in Italy during the pandemic.

BACKGROUND
We investigated the presence of anti-SARS-CoV-2 antibodies in Italian plasma pools and intravenous immunoglobulins sent to our Institute (Italian National Institute of Health - Istituto Superiore di Sanità) in the context of the Official Control Authority Batch Release. The plasma pools were made up from donations collected in several different Italian regions from May 2017 to October 2020, i.e. in the pre-pandemic and pandemic periods.


MATERIALS AND METHODS
All plasma pools were initially tested for the qualitative detection of anti-SARS-CoV-2 antibodies against the nucleocapsid protein using the Roche Elecsys® Anti-SARS-CoV-2 test kit. Plasma pools positive for these antibodies were further tested using the Roche Elecsys® Anti-SARS-CoV-2 S test kit for the quantitative detection of antibodies against SARS-CoV-2 spike receptor binding domain. All plasma pools showing reactivity to these antibodies were tested undiluted for the presence of SARS-CoV-2 RNA using the Grifols Procleix SARS-CoV-2 transcription-mediated amplification assay. Intravenous immunoglobulins were tested using both test kits to determine the presence of anti-SARS-CoV-2 antibodies.


RESULTS
All plasma pools made up from donations collected in the pre-pandemic period were negative for anti-SARS-CoV-2 antibodies against the nucleocapsid protein. Of the plasma pools made up from donations collected from December 2018 to March 2020, only 1 pool out of 68 (1.4%), that was made up from donations from the Lombardy region, was reactive for these antibodies. Interestingly, 105 out of 174 (60.3%) of the plasma pools made up from donations collected from November 2018 to October 2020 showed the presence of these antibodies. All plasma pools positive for these antibodies were tested for antibodies against SARS-CoV-2 spike receptor binding domain and were confirmed positive.


DISCUSSION
None of these plasma pools tested were reactive for SARS-CoV-2 RNA. In the case of intravenous immunoglobulins, 20 out of 25 (80%) batches showed the presence of both anti-SARS-CoV-2 antibodies, reflecting the concentration in the plasma pools used for their production.