Immune signature in vaccinated versus non-vaccinated aged people with COVID-19 pneumonia.

BACKGROUND: A definition of the immunological features of COVID-19 pneumonia is needed to support clinical management of aged patients. In this study, we characterized the humoral and cellular immune responses in presence or absence of SARS-CoV-2 vaccination, in aged patients admitted to the IRCCS San Raffaele Hospital (Italy) for COVID-19 pneumonia between November 2021 and March 2022. METHODS: The study was approved by local authorities. Disease severity was evaluated according to WHO guidelines. We tested: (A) anti-SARS-CoV-2 humoral response (anti-RBD-S IgG, anti-S IgM, anti-N IgG, neutralizing activity against Delta, BA1, BA4/5 variants); (B) Lymphocyte B, CD4 and CD8 T-cell phenotype; (C) plasma cytokines. The impact of vaccine administration and different variants on the immunological responses was evaluated using standard linear regression models and Tobit models for censored outcomes adjusted for age, vaccine doses and gender. RESULT: We studied 47 aged patients (median age 78.41), 22 (47%) female, 33 (70%) older than 70 years (elderly). At hospital admission, 36% were unvaccinated (VACno), whilst 63% had received 2 (VAC2) or 3 doses (VAC3) of vaccine. During hospitalization, WHO score > 5 was higher in unvaccinated (14% in VAC3 vs. 43% in VAC2 and 44% VACno). Independently from vaccination doses and gender, elderly had overall reduced anti-SARS-CoV-2 humoral response (IgG-RBD-S, p = 0.0075). By linear regression, the anti-RBD-S (p = 0.0060), B (p = 0.0079), CD8 (p = 0.0043) and Th2 cell counts (p = 0.0131) were higher in VAC2 + 3 compared to VACno. Delta variant was the most representative in VAC2 (n = 13/18, 72%), detected in 41% of VACno, whereas undetected in VAC3, and anti-RBD-S production was higher in VAC2 vs. VACno (p = 0.0001), alongside neutralization against Delta (p = 0141), BA1 (p = 0.0255), BA4/5 (p = 0.0162). Infections with Delta also drove an increase of pro-inflammatory cytokines (IFN-α, p = 0.0463; IL-6, p = 0.0010). CONCLUSIONS: Administration of 3 vaccination doses reduces the severe symptomatology in aged and elderly. Vaccination showed a strong association with anti-SARS-CoV-2 humoral response and an expansion of Th2 T-cells populations, independently of age. Delta variants and number of vaccine doses affected the magnitude of the humoral response against the original SARS-CoV-2 and emerging variants. A systematic surveillance of the emerging variants is paramount to define future vaccination strategies.

Salivary molecular testing for SARS-CoV-2: simplifying the diagnosis without losing accuracy

BackgroundQuantitative RT-PCR on NasoPharyngeal Swab (NPS) is still considered the standard for the diagnosis of SARS-CoV-2 infection, even if saliva has been evaluated in several studies as a possible alternative. The use of point of care (POC) platforms, providing highly specific results performed on saliva could simplify the diagnosis of COVID-19 and contribute to contain the spreading of SARS-CoV-2. MethodsWe assess the sensitivity and specificity of molecular testing performed on saliva in comparison to NPS using two different POC platforms (DiaSorin Simplexa and Cepheid Xpert(R)). NPS and saliva were collected prospectically from asymptomatic health care workers and mildly symptomatic patients. Moreover, the stability of saliva samples after storage at -80{degrees}C for up to 45 days was tested. ResultsThe obtained results in comparison to NPS demonstrated for both DiaSorin Simplexa and Xpert(R) Xpress a specificity of 100% and a sensitivity of 90.24%. The overall agreement between the tests performed on saliva was 98%. A positive correlation in Ct values detected on saliva and on NPS was identified for all the targets shared by the tests in analysis (Orf1ab, E and N2). Both S Ct values and Orf1ab Ct values were not significantly different before and after the freezing in the tested saliva samples. ConclusionThe obtained results demonstrated an overall performance of saliva comparable to NPS, confirming that RT-PCR performed using POCs on saliva could represent a valid public health solution for controlling SARS-CoV-2 pandemic.

SARS-CoV-2 antibodies rapid tests: a valuable epidemiological tool in challenging settings

BackgroundDuring the last year, mass screening campaigns have been carried out to identify immunological response to SARS-CoV-2 and establish a possible seroprevalence. The obtained results gained new importance with the beginning of SARS-CoV-2 vaccination campaign, as the lack of doses has persuaded several countries to introduce different policies for individuals who had a history of COVID 19. LFAs may represent an affordable tool to support population screening in LMICs, where diagnostic tests are lacking, and epidemiology is still widely unknown. However, LFAs have demonstrated a wide range of performance and the question of which one could be more valuable in these settings still remains. MethodsWe evaluated the performance of 11 LFAs in detecting SARS-CoV-2 infection, analysing samples collected from 350 subjects. In addition, samples from 57 health care workers collected at 21-24 days after the first dose of Pfizer-BioNTech vaccine were also evaluated. FindingsLFAs demonstrated a wide range of specificity (92.31% to 100%) and sensitivity (50 to 100%). The analysis of serum samples post vaccination was used to describe the most suitable tests to detect IgG response against S protein RBD. History of TB therapy was identified as a potential factor affecting the specificity of LFAs. ConclusionsThis analysis identified which LFAs represent a valuable tool not only for the detection of prior SARS-CoV-2 infection, but also to detect IgG elicited in response to vaccination. These results demonstrated that different LFAs may have different applications and the possible risks of their use in high TB burden settings.