Role of Homologous Fc Fragment in the Potency and Efficacy of Anti‐Botulinum Antibody Preparations

Abstract

The only approved treatment for botulism relies on passive immunity which is mostly based on antibody preparations collected from hyper-immune horses. The IgG Fc fragment is commonly removed from these heterologous preparations to reduce the incidence of hyper-sensitivity reactions. New-generation therapies entering the pipeline are based on a combination of humanized monoclonal antibodies (MAbs), which exhibit improved safety and pharmacokinetics. In the current study, a systematic and quantitative approach was applied to measure the direct contribution of homologous Fc to the potency of monoclonal and polyclonal antitoxin preparations in mice. Homologous Fc increased the potency of three individual anti-botulinum toxin MAbs by up to one order of magnitude. Moreover, Fc fragment removal almost completely abolished the synergistic potency obtained from a combined preparation of these three MAbs. The MAb mixture neutralized a 400-mouse median lethal dose (MsLD50) of botulinum toxin, whereas the F(ab′)2 combination failed to neutralize 10 MsLD50 of botulinum toxin. Notably, increased avidity did not compensate for this phenomenon, as a polyclonal, hyper-immune, homologous preparation lost 90% of its potency as well upon Fc removal. Finally, the addition of homologous Fc arms to a heterologous pharmaceutical anti-botulinum toxin polyclonal horse F(ab′)2 preparation improved its efficacy when administered to intoxicated symptomatic mice. Our study extends the aspects by which switching from animal-based to human-based antitoxins will improve not only the safety but also the potency and efficacy of passive immunity against toxins.

Camelid VHHs Fused to Human Fc Fragments Provide Long Term Protection Against Botulinum Neurotoxin A in Mice

“…Protection against BoNT/A light chain was observed when scFvs fused with Fc fragments (scFv-Fc) obtained from a macaque immune library were tested ex vivo [55]. Furthermore, the substantial contribution of the homologous Fc fragment to the potency of three individual anti-botulinum mAbs in antibody preparations has been demonstrated [56].…”

Peptides, Antibodies, Peptide Antibodies and More

“…Rhesus-D Ig/rhesus syndrome prophylaxis PAb (Sp IVIG) [69] Anti-toxins/botulism PAb (Sp IVIG) [70,71] Rituximab/lymphoma, Ocrelizumab/multiple sclerosis MAb (recombinant), chimeric [72,73] Infliximab/rheumatoid arthritis MAb (recombinant), chimeric [74] Nivolumab/malignant melanoma MAb (recombinant), human [75] Panitumumab/EGFR metastatic colorectal carcinoma MAb (recombinant), human [76] Daclizumab/allograft rejection Mab (recombinant), humanized [77] HpHbR Ab-PBD conjugate/African trypanosomiasis treatment (mouse model) MAb-drug conjugate [78] Vaccines MMR live attenuated viruses vaccine/measles, mumps, rubella prophylaxis PAb in vivo [79] DiTePePolHiB SU vaccine/diphtheria-tetanus-pertussis-polio-hemophilus prophylaxis PAb in vivo [80][81][82] HPV SU vaccine/cervix cancer prophylaxis PAb in vivo [83,84] CD: cluster of differentiation. DiTePePolHiB SU: Diphteria-Tetanus-Pertussis-Polio-Hemophilus influenzae B subunit vaccine.…”

“…Table 3 illustrates therapeutic PAb products obtained from human sera or by immunization of animals. Prominent examples are Rhesus-D PAbs (RhD Ig) used for rhesus syndrome prophylaxis and anti-botulinum toxin PAbs used for treating intoxications [69][70][71].…”

Identification and genetic characterization of a novel Orthobunyavirus species by a straightforward high-throughput sequencing-based approach

“…In this study, an HTS-based approach was applied to identify the origin of a viral pathogen found to be present in plasma obtained from a hyperimmune horse 21 . To this end, we have established a straightforward procedure that includes virus enrichment in cell culture followed by RNA extraction from the growth medium, rapid library preparation, sequencing and in-depth data analyses.…”