Our ultimate goal is to develop a novel antibody detection platform for dynamic population-scale monitoring of disease spread that can be commercialized and translated to the clinic. To achieve this, we are working to integrate our antibody detection assay with a single-channel microfluidic device that will allow automatic processing of the blood samples. This versatile platform can be applied to detect antibodies associated with other diseases, such as autoimmune and infectious diseases, through straightforward substitution of the capture antigen. Overall, this antibody detection platform could allow for rapid and facile assessment of immune protection, which can transform our understanding and targeting of disease.
To achieve sensitive detection of immunoglobulin G (IgG), we created a yeast surface-displayed error-prone library based on the anti-human IgG Fc antibody HP6017 that mutagenized complementarity-determining regions (CDRs) of both the heavy and light chains. Magnetic-activated cell sorting (MACS) and fluorescence-activated cell sorting (FACS) against human IgG Fc were performed to evolve clones with enhanced binding affinity. After five rounds of sorting, we achieved excellent enrichment of our libraries against human IgG. We then reformulated promising clones as full-length antibodies and antibody-invertase (Ab+Invertase) fusion proteins and determined their binding affinity by biolayer interferometry. Our human IgG binders exhibited significantly tighter binding compared to parental HP6017, as both full-length antibodies and Ab+Invertase fusion proteins. We then assessed their in-assay performance for detecting human IgG compared to the parent clone HP6017 and found the affinity matured antibody variants showed enhanced catalytic performance in SARS-CoV-2 antibody detection. Currently we are testing its application in other diseases, such as HIV and Hepatitis B.
In conclusion, we have designed, produced, and validated Ab+Invertase fusion proteins that allow for the quantitative assessment of disease-protective antibodies in patient serum using commercially available glucometers. Through affinity maturation, we selected anti-IgG antibody that detects the targets with greater sensitivity. In particular, these molecules show faster association rates compared to the original HP6017, allowing for shorter incubation times to expedite the diagnostic assay. The development of this novel antibody detection platform represents a significant advance in the field of disease monitoring and has the potential to revolutionize our ability to combat a range of health conditions and improve response to future pandemics.