Iimmunotherapeutic potential of Bulgarian intravenous immunoglobulin (Immunovenin-intact 5% IgG)

Abstract

The scope of this study was to investigate the presence of antibodies against widespread pathogenic viruses, fungi, and bacteria in Bulgarian intravenous immunoglobulin (IVIG). A total of 90 batches of Immunovenin-intact 5% IgG (BB-NCIPD EAD Sofia, Bulgaria) and plasma from 64 COVID-19 convalescent donors (CCP) were studied; plasma samples of 32 healthy donors were used as controls. SARS-CoV-2 RBD IgG, IgG antibodies against Candida albicans, and IgG antibodies against alpha-hemolysin (Hla) of Staphylococcus were determined by semi-quantitative ELISAs. SARS-CoV-2-specific IgG was detected in all “pandemic” batches with a mean (min–max) level of 7.4 ± 3.9, compared to 4.1 ± 2.4 for CCP. All tested IVIG batches (90/90, 100%) contained IgG antibodies against Candida albicans with a mean (min-max) level of 27.4 ± 1.4, as compared to five positive sera (5/12, 42%) with a level of 17.2 ± 7.6. A positive result for S. aureus anti-Hla IgG was obtained for 88/90 (98%) IVIG batches tested, with a mean (min-max) absorbance of 2.21 (1.5–3.0). The presence of specific IgG antibodies against widespread pathogens in nearly all studied IVIG batches supports their potential use in passive immunization and immunotherapy, pending the development of an algorithm for assessing specific antibody content and subsequent clinical studies.