Researchers are investigating monoclonal antibodies as an alternative to traditional anti-RhD prophylaxis for preventing hemolytic disease of the fetus and newborn (HDFN), according to a study recently published in Blood Advances.
While polyclonal immunoglobulin G (RhD-pIgG) has significantly reduced HDFN cases in developed countries, access remains limited in lower-income nations. The study explored targeted Fc domain mutations to enhance antibody-dependent cellular cytotoxicity (ADCC), showing promising results in improving monoclonal antibody efficacy.
Many nations across the world have limited anti-RhD prophylaxis options available because of inadequate public health care resources and high costs. HDFN still affects large numbers of infants in low-income and middle-income countries worldwide, with perinatal deaths reported in more than 160,000 babies each year and more than 100,000 cases of related disability reported annually.
What is HDFN?
Hemolytic disease of the fetus and newborn (HDFN) is an immune-mediated red blood cell disorder that occurs when a baby’s RBCs break down quickly, which is called hemolysis. HDFN is caused by a mismatch between a mother’s and her baby’s blood type (A, B, AB, or O) or Rhesus (Rh) factor (Rh-positive or Rh-negative) during pregnancy.
Although the mechanism involved in preventing HDFN remains to be clarified, the development of alternative anti-RhD monoclonal antibodies has concentrated on guaranteeing antibody-dependent phagocytosis and antibody-dependent cellular cytotoxicity (ADCC) by natural killer (NK) cells. Of note, several anti-RhD monoclonal antibodies have been produced and assessed in clinical trials; however, none has demonstrated equivalent activity to the RhD-pIgG derived from blood donors.
Read more about the prognosis of HDFN
This issue might be the result of “differing glycosylation profiles of anti-RhD [monoclonal antibodies] produced in cell lines.” Glycosylation—specifically afucosylation—of antibody constant regions can enhance ADCC by strengthening the binding of IgG to fragment crystallizable (Fc) gamma receptors (FcγRs) on NK cells. An additional potential strategy for improving ADCC is the introduction of point mutations in the monoclonal antibody Fc domain.
The investigators sought to improve ADCC mediated by two existing anti-RhD monoclonal antibodies—Brad3 and Fog1—via targeted Fc domain mutagenesis. They evaluated Fc mutagenesis and afucosylation, and compared the functional impact of these modified monoclonal antibody variants with RhD-pIgG.
The Fc regions of Brad3 and Fog1 were exposed to mutagenesis, in order to introduce ADCC-enhancing mutations, then were expressed in Chinese hamster ovary (CHO) cells under standard conditions.
Results of the study showed that targeted Fc mutagenesis enhanced ADCC significantly compared with the use of wild-type monoclonal antibodies, while, at the same time, “preserving RhD binding and efficient production in CHO cells.”
The authors concluded that “Fc mutations improve the function of anti-PhD monoclonal antibodies without glycoengineering.”
