Methods
We treated four critically ill children actively infected with
SARS-CoV-2 with CP at the Children’s Hospital of Philadelphia (CHOP)
under emergency Investigational New Drug applications (eINDs) through
the Food and Drug Administration (FDA). Patients were considered for CP
if they met FDA guidance for life-threatening disease (Appendix S1). We
prospectively screened and enrolled these patients into a larger
SARS-CoV-2 biobanking protocol. Patients were enrolled on the biobank
protocol if they had evidence of SARS-CoV-2 infection on
reverse-transcriptase polymerase chain reaction (RT-PCR) testing from
respiratory tract mucosa. This protocol was approved by the CHOP
Institutional Review Board. Consent was obtained for both protocols from
a legal authorized representative per the Declaration of Helsinki
(written informed consent for CP; verbal consent for biobanking).
Clinical data were abstracted from patient charts to standardized forms
by a research assistant using a REDCap database and verified by a
physician. Blood samples were obtained from participants prior to CP
infusion, following CP infusion and weekly thereafter until death or
discharge. Remnant donor CP was retained.
SARS-CoV-2 specific antibodies were measured by ELISA as previously
described.8 Antibodies in serially diluted plasma
(starting at 1:50) were measured against RBD of the SARS-CoV-2 spike (S)
protein,9 full-length S protein, and the N protein
(Sino Biological, Wayne, PA). Reciprocal plasma dilutions were
calculated from an optical density (OD) threshold from a set
concentration. Standard curves were generated by diluting an
RBD-specific monoclonal antibody (CR3022) starting at 0.5 µg/mL (RBD and
S ELISAs) or serially diluted pooled serum from actively SARS-CoV-2
infected adults (N ELISAs). See Appendix S2 for detailed methods.