In order to determine the humoral protective response against SARS-CoV-2, the vaccine-induced and naturally induced neutralizing antibodies (NtAbs) responses against SARS-CoV-2 variants circulating in Italy through in vitro live virus neutralization assay were evaluated. A total of 39 SARS-CoV-2 recovered subjects (COVID-19+) and 63 subjects with a two-dose cycle of the BNT16262 vaccine were enrolled. A single serum sample was tested for COVID-19+ at 35–52 days post-positive swab, while vaccinees blood samples were taken at one (V1) and at three months (V3) after administration of the second vaccine dose. Significantly higher NtAb titers were found against B.1 and Alpha in both COVID-19+ and vaccinees, while lower NtAb titers were detected against Delta, Gamma, and Omicron variants. A comparison between groups showed that NtAb titers were significantly higher in both V1 and V3 than in COVID-19+, except against the Omicron variant where no significant difference was found. COVID-19+ showed lower neutralizing titers against all viral variants when compared to the vaccinees. Two-dose vaccination induced a sustained antibody response against each analyzed variant, except for Omicron. The evolution process of SARS-CoV-2, through variants originating from an accumulation of mutations, can erode the neutralizing effectiveness of natural and vaccine-elicited immunity. Therefore, a need for new vaccines should be evaluated to contain the ongoing pandemic.

This study evaluated the epidemiology and seasonal patterns of respiratory viruses in adults hospitalized with acute respiratory tract infections during two consecutive post-COVID-19 pandemic seasons. A retrospective study was conducted at the University Hospital “P. Giaccone”, Palermo, from September 2022 to September 2024. Multiplex molecular assays were used to detect the ten respiratory viruses most relevant from an epidemiological perspective in respiratory samples (n = 1110) of 1081 patients. A respiratory viral infection was identified in 29.6% of patients. The highest viral infection rate was observed in the 31–50 age group. Human rhinovirus/enterovirus (HRV/EV) was the most frequently detected (40%), followed by influenza A virus (IAV; 18.4%) and human coronaviruses (HuCoVs; 12.8%). Viral co-infections were identified in 10.9% of positive cases, with HRV/EV, adenovirus (ADV), and parainfluenza virus (PIV) being most frequently involved. Influenza and respiratory syncytial viruses (RSVs) showed a winter seasonality, while diverse circulation patterns were revealed for the other viruses. This study demonstrated a sustained circulation of respiratory viruses in adults hospitalized with severe respiratory symptoms, with HRV/EV accounting for most of them. Syndromic multiplex molecular testing, although limited to the detection of a small fraction of epidemiologically relevant known viruses, has proven to be a valuable tool, not only for diagnostic purposes but also for acquiring genotyping data and implementing epidemiological information from sentinel surveillance systems.

From July 2022, a novel Echovirus 11 (E11) variant has been associated with severe neonatal infections and liver failure. Currently, there are no vaccines or antiviral options for the targeted treatment of non-polio enterovirus (EV) infections; therefore, anti-EV drugs are urgently needed. In this study, the putative anti-E11 activity of two isoxzoline-carbocyclic monophosphate nucleotides (4a and 4b) was evaluated in vitro by cytopathic effect (CPE) reduction in VERO 76 cells and qRT-PCR. Treatment with nucleotide 4a at 25 and 50 μM successfully diminished the CPE caused by E11 by 90% and 75%, respectively, and induced a reduction in viral RNA in the supernatant by 72% and 89%. In contrast, the treatment with 25 and 50 μM of 4b caused a minor inhibition of CPE (58 and 38%), and no significant E11 RNA level changes were observed. A time course viral progeny production assay was performed to assess the inhibitory effect of nucleotide 4a on E11 infection progression. Compared to the control, the treated group showed a significant drop in viral RNA levels, with reductions of 43% at 10 h, 65% at 24 h, and 96% at 48 h post-infection. The results showed the extensive antiviral properties of the monophosphate nucleotide 4a in vitro. Moreover, a retrospective molecular docking study strongly supports that nucleotide 4a is an RdRp inhibitor capable of decreasing E11 genome replication and virus particle formation in VERO 76 cells.