{
  "abstract": "Background Rabbit IgG Fc amino acid sequences are highly similar to human IgG1 Fc, especially at the Fcγ receptor (FcγR) binding sites, and Biolayer Interferometry (BLI) kinetic analysis of rabbit IgG and human IgG1 showed equivalent interactions with human FcγRs. Recombinant Rabbit IgG antibody completely devoid of binding to human Fcγ can be used to reduce false positives caused by human Fcγ receptors in bioassays. Here, we describe a mutated rabbit Fc region (FcZero-rAb) designed to significantly reduce potential non-specific antibody staining caused by IgG receptors in various applications, including flow cytometric analysis of human cells.Methods We analyzed the rabbit Fc-human FcγR interface by antibody modeling and identified some novel mutations that disrupt the interface of IgGs and FcγRs. Binding between the engineered Rabbit IgG Fc domain and human and mouse Fc receptors were measured by BLI. Background signal due to Fc receptor binding was measured by flow cytometry.Results BLI kinetic analysis showed that human FcγR interactions and mouse FcγR interactions are completely abolished in engineered Rabbit IgG backbones while human FcRn interactions are unaffected. Using the FcZero-rAb backbone for antibodies used in flow cytometry results in less background and greater separation of positive and negative populations than using wild-type IgG and Fc receptor block. The mutations do not affect rabbit Fc stability and antibodies including the engineered backbone are stable for up to 5 years as shown by accelerated stability testing.Conclusions We have recombinantly engineered a Rabbit IgG backbone (FcZero-rAb) that eliminates non-specific background from Human Fc gamma receptor and Mouse Fc gamma receptor binding.",
  "authors": [
    {
      "affiliations": [
        "Proteintech, Rosemont, IL, USA"
      ],
      "name": "Qilin Zhang"
    },
    {
      "affiliations": [
        "Proteintech, Rosemont, IL, USA"
      ],
      "name": "Alice Wang"
    },
    {
      "affiliations": [
        "Proteintech, Rosemont, IL, USA"
      ],
      "name": "Ran Zhang"
    },
    {
      "affiliations": [
        "Proteintech, Rosemont, IL, USA"
      ],
      "name": "Annika Dalheim"
    },
    {
      "affiliations": [
        "Proteintech, Rosemont, IL, USA"
      ],
      "name": "Mengsha Gong"
    },
    {
      "affiliations": [
        "Proteintech, Rosemont, IL, USA"
      ],
      "name": "Yanan Lu"
    },
    {
      "affiliations": [
        "Proteintech, Rosemont, IL, USA"
      ],
      "name": "Deepa Shankar"
    }
  ],
  "title": "1008 A novel engineered rabbit IgG Fc domain that eliminates human FcγR interactions for reduced background in antibody-based bioassays",
  "uid": "b52e76c6-4e91-5d39-af3b-3c39dbdb7e3c"
}