Serum Antibody Fingerprinting for SARS-CoV-2 Variants in Infected and Vaccinated Subjects by Label-Free Microarray Biosensor (preprint)

Both viral infection and vaccination affect the antibody repertoire of a person. Here we demonstrate that the analysis of serum antibodies carries information not only on the virus type that caused the infection, but also on the specific virus variant. We developed a rapid multiplex assay providing a fingerprint of serum antibodies against five different SARS-CoV-2 variants, based on a microarray of virus antigens immobilized on the surface of a label-free reflectometric biosensor. We analyzed serum from plasma of convalescent subjects and vaccinated volunteers and extracted individual antibody profiles of both total immunoglobulin Ig and IgA fraction. We found that Ig level profiles were strongly correlated with the specific variant of infection or vaccination and that vaccinated subjects displayed larger quantity of total Ig and lower fraction of IgA relative to the population of convalescent unvaccinated subjects.

Epidemic preparedness - Leishmania tarentolae as an easy-to-handle tool to produce antigens for viral diagnosis: application to COVID-19 (preprint)

To control future epidemics, discovery platforms are urgently needed, for the rapid development of diagnostic assays. Molecular diagnostic tests for COVID-19 emerged shortly after the isolation of SARS-CoV-2, however, serological tests based on antiviral antibody detection, revealing previous exposure to the virus, required longer developmental phases, due to the need for correctly folded and glycosylated antigens. The delay between the identification of a new virus and the development of reliable serodiagnostic tools limits our readiness for the control of a future epidemic. In this context, we propose the protozoan Leishmania tarentolae as an easy-to-handle micro-factory for the rapid production of viral antigens, to be used at the forefront of emerging epidemics. As a study model, we engineered L. tarentolae to express the SARS-CoV-2 Receptor Binding Domain (RBD) and report the ability of the purified RBD antigen to detect SARS-CoV-2 infection, with a sensitivity and reproducibility comparable to that of a reference antigen produced in human cells. This is the first application of an antigen produced in L. tarentolae for the serodiagnosis of a Coronaviridae infection. Based on our results, we propose L. tarentolae as an effective system for viral antigen production, even in countries that lack high-tech cell factories.