Dr. Woodle and his colleagues validated the One Lambda™ LABScreen™ COVID Plus Assay for SARS-CoV-2 antibodies using serum samples from transplant candidates and recipients.
The assay was superior to most currently available SARS-CoV-2 tests in terms of specificity and sensitivity, and no cross-reactivity with antibodies to common cold viruses was observed.
The team concluded that the LABScreen COVID Plus Assay was highly suitable for use in transplant laboratories, and that it could easily be implemented in their workflows.
SARS-CoV-2 has had a significant impact on transplant candidates and recipients who are immunosuppressed, because they are susceptible to infection and often have underlying health conditions. Detecting and quantifying HLA antibodies is critical to accurately assess the risk of transplantation for these patients. However, SARS-CoV-2 can make such risk assessments uniquely challenging. Transplant patients often have impaired antibody responses that can result in false negative tests, while cross-reactivity with antibodies to common cold viruses can generate false positive results. A better assessment of an antibody profile can be made by taking a multiplexing approach, as it reduces the potential for false negatives and false positives.
Multiplex testing with the LABScreen COVID Plus Assay is more efficient and cost-effective than testing for individual antibodies. The comprehensive detection panel of the assay includes antibodies that target the SARS-CoV-2 spike trimer, S1 subunit, S2 subunit, receptor-binding domain (RBD), and nucleocapsid protein. The panel also includes antibodies that target the spike proteins of HCoV-229E, HCoV-HKU1, HCoV-NL63, HCoV-OC43, MERS-CoV, and SARS-CoV. With Luminex® xMAP® technology and a One Lambda™ LABScan™ 100 or LABScan3D™ System, results can be obtained in just a few hours.
With the LABScreen COVID Plus Assay, researchers can:
- Confirm and benchmark previous SARS-CoV-2 infection
- Differentiate antigenicity along the spike and nucleocapsid proteins
- Monitor changes in antibody profiles over time to assess patient risk
Dr. Woodle and his colleagues wanted to use the assay to create antibody profiles that could be used to identify transplant patients who were more likely to become severely ill with SARS-CoV-2. They also wanted to monitor antibody profiles over time to investigate the epidemiology and clinical course of SARS-CoV-2 in these patients.
The team tested a total of 189 human serum samples to validate the LABScreen COVID Plus Assay. Ninety-six of the samples came from transplant candidates who were on the United Network for Organ Sharing (UNOS) waitlist in October 2018. These samples were presumed to be negative for SARS-CoV-2 antibodies. The team also tested 51 samples from transplant candidates who were on the UNOS waitlist in May 2020. The samples had been tested previously with an ELISA assay for SARS-CoV-2 RBD antibodies. The remaining 42 samples came from non-transplant patients who were recovering from SARS-CoV-2 infections that had been confirmed with either a validated ELISA assay or a PCR test.
The team found that the LABScreen COVID Plus Assay detected antibodies against the SARS-CoV-2 spike and nucleocapsid proteins with nearly 100% specificity. Even when antibodies to common coronaviruses were present, no cross-reactivity was observed. The assay was also highly sensitive. All 42 samples from individuals with confirmed SARS-CoV-2 infections tested positive for at least three of the five SARS-CoV-2 antibodies. The assay provided semiquantitative results, so the researchers were able to evaluate the proportional response to each of the five SARS-CoV-2 antigens.
Future applications: understanding heterogeneity in the antibody response
The antibody responses of symptomatic and asymptomatic individuals infected with SARS-CoV-2 differ, as do those of survivors and individuals who die as a consequence of infection. Characterizing the antibody response to multiple SARS-CoV-2 antigens could potentially help clinicians anticipate responses to therapy and improve patient outcomes. Functional analyses to investigate antibody isotype, subclass, FcR binding capacity, and complement binding capacity could be incorporated into the assay. This type of analysis would provide valuable information about the global antibody response to SARS-CoV-2. The assay could also be used to investigate nonstructural proteins and mutated versions of the RBD, which could help researchers determine whether such mutations affect the antibody response.
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