HIGH-RESOLUTION MAPPING OF T-CELL HYBRID IMMUNITY TO THE ENTIRE SARS-CoV-2 PROTEOME

Background: To understand T-cell responses to SARS-CoV-2, it is essential to define the contribution of infection versus immunization to virus-specific hybrid immunity. Here, we characterized the breadth and magnitude of T-cell responses to the entire SARS-CoV2 proteome over a 2-year follow-up period in infected and vaccinated (CoV2+Vac+) and vaccinated and infected (Vac+CoV2+) individuals. Method(s): We selected samples from 38 (19 CoV2+ and 19 CoV2-, time1, T1) ProHEpiC-19 cohort participants, a prospective, longitudinal study starting in March 2020 involving 7,776 healthcare workers in Spain. Longitudinal samples were available from 10 of them after a 3-dose mRNA vaccination, including 5 CoV2+Vac+ and 5 Vac+CoV2+, at 824.5 and 250.5 days from symptoms onset (DfSO, time 2, T2). We measured the breadth and magnitude of IFN-y T-cell responses by ELISpot assay in cryopreserved PBMCs, using a 15-mer overlapping peptide (OLP) library of 2,790 SARS-CoV-2 peptides in 100 pools. Result(s): We identified immunodominant T-cell responses in S1, S2, nsp3, Env, NC, and M proteins across the SARS-CoV2 proteome. We observed an increased breadth of T-cell responses (responding pools over the entire region) to S1 (44 - 30%) and S2 (31 - 40%) in CoV2+Vac+ and Vac+CoV2+, respectively. In addition, CoV2+Vac+ had an exclusive and sustained response to M. We found significantly stronger responses in CoV2+Vac+ (P=0.0313). Particularly the total magnitude was greater in CoV2+Vac+ vs. Vac+CoV2+ in S1 (4476.88 vs. 1498.53), Env (457.34 vs. 250.50), and M (455.13 vs. 0.00) but not in S2 and nsp3. The total number of peptides for deconvolution was higher in CoV2+Vac+ (32 peptides) than in Vac+CoV2+ (3 peptides) during the follow-up. Seventy-five percent of the responses targeted S, and 25% M, ORF1a, and Env. Conclusion(s): These results profile immunodominant T-cell responses in S1, S2, nsp3, Env, NC, and M proteins across the entire SARS-CoV2 proteome. The data delineate differences in the number of T-cell responses primed hybrid immunity by infection previous to vaccination (CoV2+Vac+), being broader and of higher magnitude and underlining an exclusive T-cell response to the M region. Overall, these findings identify differences in long-term T-cell hybrid immunity primed by infection or vaccination, which may have implications in protection from re-infection and vaccine design.

Early core signature of soluble factors in mild to moderate SARSCOV-2 infection

Background: Understanding the kinetics of early immune responses to SARSCoV-2 infection is critical to identify potentials biomarkers of disease outcome. A myriad of soluble mediators including, pro-inflammatory, immune-suppressors and growth factors, play a relevant role in the disease progression. However, to date, limited data is available about the role of soluble factors and most studies focus only in severe cases with limited follow-up. Here, we studied with high resolution the kinetics of soluble mediators in mild to moderate cases of SARSCoV-2 infection 1-90 days from symptom onset (DfSO). Methods: We selected individuals from the ProHEpiC-19 cohort study that included mainly healthcare workers with a PCR+ and mild or moderate disease within 1-14 DfSO. IgG and IgM levels were determined by ELISA. We selected plasma samples (n=30) in the range of 1-90 DfSO, and performed a Luminex multiplex assay including 45 soluble human factors. Results: We identified a core signature including 19 highly correlated soluble factors at 1-14 DfSO, based on clustering analysis. The core signature contained three sub-clusters: #1 (RANTES, IL13, TGFa, PDGF-AB, PDGF-AA, EGF, MIP1b, CD40L and GROb), #2 (G-CSF, PDL1-B7, Fractalkine, IL8, IFNg, Granzyme B and IL10) and #3 (IL7, IL6, and VEGF). We found major changes in #2 and #3 cluster composition between 1-14 and 30-45 DfSO, due to the loss of PDL1-B7, Fractalkine, IL8, IL7, IL6, and VEGF association. Moreover, by 60-75 DfSO, the soluble factor association in #2 and #3 disappeared from the core signature. In addition, we observed a negative correlation between IgG and IgM levels with IL4 production at 1-14 DfSO (IgG: ρ =-0.82, p=0.012;IgM ρ=-0.83, p=0.011). Similarly, a negative correlation was observed between Igs and Mip3a at 30-45 DfSO (IgG: ρ=-0.78, p=0.023;IgM: ρ =-0.81, p=0.022). Conclusion: We delineated a core signature of soluble factors in mild to moderate SARS-CoV-2 infection, including growth factors, chemokines and pro-inflammatory cytokines. The longitudinal follow-up of this signature revealed significant changes during the 1-90 DfSO. This information can provide new insights for the definition of biomarkers for patient stratification in mild or moderate SARS-Cov-2 infection. Further data is needed to understand the association between IL4 and Mip3a with low Igs levels.

[Descriptive study of the health service workers of a Primary Care Department confined by Covid-19.]

OBJECTIVE: The Covid-19 pandemic is testing the resistance of health systems, the preservation of health professionals is a priority in processes of this type. The professionals' exposure to suspicious contacts often requires their confinement. The objective was to know the epidemiological characteristics of the primary care professionals who required confinement. METHODS: The research was carried out in the North Metropolitan Primary Care Area of Barcelona, from February 17 to May 3, 2020. 1,418 professionals who required confinement due to the epidemic by Covid-19 participated. The reasons for confinement, symptomatology, the confinement time and the results of PCR tests results were recorded. Univariate descriptive analysis was performed. RESULTS: 78.8% of the professionals were women and the mean age was 45.2 years. 67.8% were doctors and nurses, in the remaining 32.2% there were different healthcare and non-care professionals. 64.1% of the sample presented symptoms compatible with Covid-19. Participants described multiple symptoms during confinement. 1,050 diagnostic RT- PCR tests were performed, being positive in 323 cases, of which 33 were in asymptomatic people. CONCLUSIONS: The impact of the epidemic by Covid-19 is anticipated in health personnel compared to the general population. The distribution of symptoms in healthcare professionals is similar to that of other studies in the general population. Of the total number of professionals requiring isolation, 22.7% confirmed the diagnosis.