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.

Ventilator-associated Pneumonia Due to MRSA vs MSSA: What Should Guide Empiric Therapy? (preprint)

The guidelines on ventilator-associated pneumonia (VAP) recommend an empiric therapy against methicillin-resistant Staphylococcus aureus (MRSA) according to its the prevalence rate. Considering the MRSA and MSSA VAP prevalence over the last 9 years in our tertiary care Hospital, we firstly compared patients with MRSA VAP to those with MSSA VAP in terms of length of stay (LOS) in intensive care unit (ICU) and mortality and secondly, we assessed the clinical value of the MRSA nasal-swab screening in either predicting or ruling out MRSA VAP. We extracted the data of 1461 patients with positive bronchoalveolar lavage (BAL). Regarding the MRSA nasal-swab screening, 170 patients were positive for MRSA or MSSA. Overall, MRSA had a high prevalence in our ICU. Despite the COVID pandemic, there was a significant downward trend in MRSA prevalence, while MSSA remained steady over time. Having VAP due to MRSA did not have any impact on LOS and mortality. Finally, the MRSA nasal-swab testing demonstrated a very high negative predictive value for MRSA VAP. Our results suggested the potential value of a patient-centered approach to improve antibiotic stewardship.

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.

Identification of variable sites in Sars-CoV-2 and their abundance profiles in time (preprint)

The SARS-CoV-2 pandemic that we are currently experiencing is exerting a massive toll both in human lives and economic impact. One of the challenges we must face is to try to understand if and how different variants of the virus emerge and change their frequency in time. Such information can be extremely valuable as it may indicate shifts in aggressiveness, and it could provide useful information to trace the spread of the virus in the population. In this work we identified and traced over time 7 amino acid variants that are present with high frequency in Italy and Europe, but that were absent or present at very low frequencies during the first stages of the epidemic in China and the initial reports in Europe. The analysis of these variants helps defining 6 phylogenetic clades that are currently spreading throughout the world with changes in frequency that are sometimes very fast and dramatic. In the absence of conclusive data at the time of writing, we discuss whether the spread of the variants may be due to a prominent founder effect or if it indicates an adaptive advantage.