COVID-19 Antibody Detection and Assay Performance Using Red Cell Agglutination

A novel syphilis Treponema pallidum lipoprotein peptide antigen diagnostic assay using red cell kodecytes in routine blood centre column agglutination testing platforms

BACKGROUND AND OBJECTIVES

The detection of treponemal antibodies, which are used to make a diagnosis of syphilis, is important both for diagnostic purposes and as a mandatory blood donor test in most countries. We evaluated the feasibility of using Kode Technology to make syphilis peptide red cell kodecytes for use in column agglutination serologic platforms.

MATERIALS AND METHODS

Candidate Kode Technology function-spacer-lipid (FSL) constructs were made for the Treponema pallidum lipoprotein (TmpA) of T. pallidum, using the peptide and FSL selection algorithms, and then used to make kodecytes. Developmental kodecytes were evaluated against a large range of syphilis antibody reactive and non-reactive samples in column agglutination platforms and compared against established methodologies. Overall, 150 reactive and 2072 non-reactive Syphicheck assay (a modified T. pallidum particle agglutination) blood donor samples were used to evaluate the agreement rate of the developed kodecyte assay.

RESULTS

From three FSL-peptide candidate constructs, one was found to be the most suitable for diagnostics. Of 150 Syphicheck assay reactive samples, 146 were TmpA-kodecyte reactive (97.3% agreement), compared with 58.0% with the rapid plasmin reagin (RPR) assay for the same samples. Against the 2072 expected syphilis non-reactive samples the agreement rate for TmpA-kodecytes was 98.8%.

CONCLUSION

TmpA-kodecytes are viable for use as cost-effective serologic reagent red cells for the detection of treponemal antibodies to diagnose syphilis with a high level of specificity in blood centres. This kodecyte methodology also potentially allows for introduction of the reverse-algorithm testing into low-volume laboratories, by utilizing existing transfusion laboratory infrastructure.

Simulated red cell antibody identification training panels created using SARS-CoV-2 kodecytes and immune plasma

BACKGROUND

Training is essential to develop and maintain skills required to be a competent serologist, yet samples required to achieve this are often difficult to obtain. We evaluated the feasibility of SARS-CoV-2 peptide modified red cells (1144-kodecytes) to develop simulated antibody screening and identification panels of reagent red cells suitable for practical training the recognition and grading of serologic reactions.

STUDY DESIGN AND METHODS

Red cells from a single donor were modified into kodecytes using Kode Technology function-spacer-lipid constructs bearing a short SARS-CoV-2 peptide. Kodecytes and unmodified cells were then arranged in patterns representative of red cell antibody profiles as simulated antibody screening and identification reagent cell panels (SASID), and then tested against immune donor plasma samples containing SARS-CoV-2 antibodies. Manual tube and two different gel card serologic platforms were evaluated by routinue techniques. SASID exemplars were created for antibodies including D, C^w , f (ce), Jk^a (strong, weak, dosing), mixtures of D+E, Jk^a +K, Fy^a +E, high and low frequency antibodies and a warm IgG autoantibody.

RESULTS

Kodecytes (positive reactions) and unmodified cells (negative) when arranged and tested in appropriate patterns in SASID panels were able to mimic IgG antibody reactions, and were capable of measuring both accuracy and precision in reaction grading.

CONCLUSIONS

Kodecytes can be used to rapidly create in-house simulated yet realistic antibody screening and identification panels suitable for large scale training in the recognition and grading of serologic reactions.

Modified Hemagglutination Tests for COVID-19 Serology in Resource-Poor Settings: Ready for Prime-Time?

During the ongoing COVID-19 pandemic, serology has suffered several manufacturing and budget bottlenecks. Kode technology exposes exogenous antigens on the surface of cells; in the case of red blood cells, modified cells are called kodecytes, making antibody-antigen reactions detectable by the old-fashioned hemagglutination test. In this commentary, we review evidence supporting the utility of SARS-CoV-2 Spike kodecytes for clinical diagnostic purposes and serosurveys in resource-poor settings.

Erytra blood group analyser and kode technology testing of SARS-CoV-2 antibodies among convalescent patients and vaccinated individuals

Surveillance of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic requires tests to monitor antibody formation and prevalence. We detected SARS-CoV-2 antibodies using red cells coated by Kode technology with short peptides derived from the SARS-CoV-2 spike protein (SP). Such modified red cells, called C19-kodecytes, can be used as reagent cells in any manual or automated column agglutination assay. We investigated the presence of SARS-CoV-2 antibodies in 130 samples from COVID-19 convalescent plasma donors using standard manual technique, two FDA-authorized enzyme-linked immunosorbent assay (ELISA) assays and a virus neutralisation assay. The sensitivity of the C19-kodecyte assay was 88%, comparable to the anti-SP and anti-nucleocapsid protein (NCP) ELISAs (86% and 83%) and the virus neutralisation assay (88%). The specificity of the C19-kodecyte assay was 90% (anti-SP 100% and anti-NCP 97%). Likewise, 231 samples from 73 vaccinated individuals were tested with an automated analyser, and we monitored the appearance and persistence of SARS-CoV-2 antibodies. The C19-kodecyte assay is a robust tool for SARS-CoV-2 antibody detection. Automated blood group analyser use enables large-scale SARS-CoV-2 antibody testing for vaccination monitoring in population surveys.