SCOVAM, a new serological trial for COVID-19

2020-06-17

Figure: Image of SCOVAM fluorescences obtained after analysis of two serum samples, one negative and one positive, of COVID-19. Yellow rectangles frame the virus proteins immobilized in SCOVAM, in duplicate and two different concentrations. The green dots indicate abundant presence of the IgG antibody, which in this case dominates over the IgM. Vertical point columns of decreasing intensity are markers of IgM (red) and IgG (green) with known concentrations (number of antibody molecules). The pairs of red dots in the corners are placeholders. Credit: CAB-INTA-CSIC.


An international team of researchers from the Center for Astrobiology (CAB, CSIC-INTA), in collaboration with other research centers and the Central Defense Hospital "Gómez Ulla" has developed SCOVAM, a serological trial for COVID-19. It is based on the biochip technology that CAB has been developing for years for the detection of life in planetary exploration. One advantage of SCOVAM over other detection methods is that it uses several of the virus's proteins, improving its ability to detect antibodies.


The Astrobiology Center has been developing fluorescent immunoassays and instrumentation for the detection of molecular traces of life in extreme environments for planetary exploration (particularly Mars) for nearly two decades. The experience gained and the collaboration with other research centers and the Central Defense Hospital "Gómez Ulla" have allowed to develop, to get ready and validate a serological trial for COVID-19 through the use of microarrays (biochips) of SARS-Cov2 virus proteins. The method, called SCOVAM (SARS COV-2 Antigen Microarray), is a fluorescence test to simultaneously detect serum IgM and IgG antibodies. The fluorescence detection method is slower (about three hours) than the fast (or lateral flow) tees but, in return, is much more sensitive (it is able to detect a smaller amount of antibodies), is semi-quantitative, scalable and scalable, as it can be operated in multiple format (up to 96 samples simultaneously, such as the classic ELISA -Enzyme-Enzyme-Linkedsorbent Assay-) as it is automated.

One advantage of SCOVAM, over other antibody detection methods such as ELISA, is that it uses several of the virus proteins to capture the antibodies present in the blood serum that are able to bind specifically to SARS-Cov2. Having several viral proteins such as "hook" allows the identification of antigenic patterns of the virus, since each person can develop a different antibody response to the different proteins. On the other hand, in the event that future research identifies predictive markers of disease progression, SCOVAM could be adapted and updated for simultaneous detection of antibodies and such markers (e.g. markers of inflammation).

SCOVAM has been ready with samples of positive and negative serums (pre-pandemic and during the pandemic) previously analyzed by two commercial methods (ELISA and chemoluminescence). The group of positive serums had also previously been tested by RT-PCR (reverse transcription coupled to polymerase chain reaction) tests to detect the presence of the virus in naso-pharyngeal samples. The method developed in the CAB shows a more than 91% match with commercial tests and, in several cases, corrects the results of false negatives of the PCR. It should be noted that 9% of discrepancies can be attributed to both the SCOVAM and commercial methods, since all methods have a range of uncertainty that prevents distinguishing a positive result from the result produced by negative serums.

The development of methods for detecting viral (including RT-PCR) and serological RNA detection methods may be skewed if only samples from people admitted or from the health care collective are used. For this reason, the CAB and the microbiology laboratory of the Central Defense Hospital "Gómez Ulla" are currently conducting a randomized and voluntary serological study in order to validate SCOVAM on a sample without apparent bias. In addition to finding out the incidence of COVID-19 in this group, the immune load against the virus will be monitored over time, so that both the titra d'or the antibody concentration (the concentration of antibodies) and its prevalence in the blood can be inferred.

SCOVAM is a powerful tool to study the existence of antigen-antibody patterns between positive serums and even to infer interactions with greater neutralizing capacity. In turn, SCOVAM could be used as a method of monitoring the effectiveness of future vaccines, in the different phases of study and/or application. 

SCOVAM's development project has involved the Central Defense Hospital "Gómez Ulla", which has provided samples and comparative studies; the Centre for Genomic Regulation (CRG) in Barcelona; CIMUS of the University of Santiago de Compostela; National Biotechnology Centre (CNB-CSIC); eurofins-Ingenase, which have provided porteins of the virus for testing.

 

Fuente: UCC-CAB

Fecha: 2020-06-17

 

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