They develop a test capable of detecting ‘invisible’ antibodies against Covid-19

A new test of “extreme” sensitivity developed at the General Hospital of Alicante, based on CSIC technology, it is capable of detect hitherto invisible covid-19 antibodies in patients who have overcome the virus and who, apparently, had not generated any immunity.

From a fingerstick, the innovative test has been designed by Hematology and Immunology researchers from the Alicante hospital center Fabián Tarín (Valencia, 54 years old), Francisco Marco (Elche, Alicante, 57) and Paula Piñero (Seville, 30) as part of the Alicante Health and Biomedical Research Institute (Isabial).

This advance, published in the prestigious journal Scientific Reports, has had the collaboration of the company Vitro Diagnóstica and the Incliva Health Research Institute.

“To date we had evidence that a minority percentage of people with proven infection (around 5 percent), especially mild, asymptomatic or immunosuppressed, did not seem to develop antibodies and probably remained unprotected in the event of a possible reinfection,” he commented to Efe Tarín.

This technique, more sensitive than conventional ones, reveals that “Almost half of these patients have antibodies in small amounts, invisible to other techniques, and therefore could have some protection against SARS-CoV-2 ”, he continued.

Therefore, the detection of these low rates of antibodies that are undetectable in other tests provides valuable information for the medical strategy of these patients who, in fact, could be protected in case of being infected again.

The work of Tarín, Marco and Piñero is based on the cell lines obtained by genetic engineering in the CSIC laboratories and is based on a test known as flow cytometry that only needs one microliter of blood extracted from the finger.

Francisco Marco, member of the Spanish Immunology Society, highlighted that the test visualizes an “essential” type of antibody, IgA type, which remains for up to eight months after infection in the vast majority of patients and constitutes the first barrier against the virus.

This is so because it is located in mucous membranes such as saliva or breast milk, where it is capable of blocking germs to prevent infection.

The scientist has warned, in any case, that “we must not lower our guard” since the presence of antibodies “does not guarantee the individual an indefinite protection” against the virus and its new variants.

Even considering these precautions, Paula Piñero has assured that the first results obtained so far in vaccinated patients “indicate that patients inoculated with the different vaccines present a vigorous response.”

The greater ability to detect antibodies by the test could be especially useful to investigate the degree of protection in immunosuppressed or cancer patients, who theoretically develop weaker immune responses, are more unprotected and exposed to severe forms of infection.

The Diagnostic Hematology and Immunology sections of the General Hospital of Alicante, to which the three authors of the study belong, are immersed in ambitious research projects related to the immunity of patients with different hematological diseases.