Since early May 2022, some monkeypox virus (MPXV) infections have been reported from countries where the disease is not endemic. Within 2 months, the number of patients has increased extensively, becoming the most considerable MPXV outbreak described. Smallpox vaccines demonstrated high efficacy against MPXVs in the past and are considered a crucial outbreak control measure. However, viruses isolated during the current outbreak carry distinct genetic variations, and the cross‐neutralizing capability of antibodies remains to be assessed. Here we report that serum antibodies elicited by first‐generation smallpox vaccines can neutralize the current MPXV more than 40 years after vaccine administration.

(1) Background: Our aim is the evaluation of the neutralizing activity of BNT162b2 mRNA vaccine-induced antibodies in different in vitro cellular models, as this still represents one of the surrogates of protection against SARS-CoV-2 viral variants. (2) Methods: The entry mechanisms of SARS-CoV-2 in three cell lines (Vero E6, Vero E6/TMPRSS2 and Calu-3) were evaluated with both pseudoviruses and whole virus particles. The neutralizing capability of sera collected from vaccinated subjects was characterized through cytopathic effects and Real-Time RT PCR. (3) Results: In contrast to Vero E6 and Vero E6/TMPRSS2, Calu-3 allowed the evaluation of both viral entry mechanisms, resembling what occurs during natural infection. The choice of an appropriate cellular model can decisively influence the determination of the neutralizing activity of antibodies against SARS-CoV-2 variants. Indeed, the lack of correlation between neutralizing data in Calu-3 and Vero E6 demonstrated that testing the antibody inhibitory activity by using a single cell model possibly results in an inaccurate characterization. (4) Conclusions: Cellular systems allowing only one of the two viral entry pathways may not fully reflect the neutralizing activity of vaccine-induced antibodies moving increasingly further away from possible correlates of protection from SARS-CoV-2 infection.

Host microRNAs (miRNAs) are widely proposed as innate antiviral effectors against SARS-CoV-2, yet whether they actually restrict infection in lung epithelial cells remains unresolved. Two of the most-cited candidates, miR-29a-3p and miR-15b-5p, are predicted to bind both the viral genome and key entry/trafficking factors such as Furin and ATG9A, but functional evidence is fragmented and often contradictory. Here, we put both miRNAs to the test in human Calu-3 cells infected with the SARS-CoV-2 Beta and Omicron BA.1 variants, using parallel gain- and loss-of-function strategies coupled to RT-qPCR of viral and cellular transcripts and back-titration of infectious progeny on VeroE6/TMPRSS2 cells. Both miRNAs transiently suppressed viral gene expression at 6 hpi, but this early dampening was followed by a marked transcript rebound at 24 hpi, especially for Omicron, with virtually no impact on total extracellular viral RNA. More strikingly, miR-15b modulation enhanced infectious virus output during Beta infection, and miR-29a overexpression boosted Omicron BA.1 infectivity, while Furin, ATG9A, AKT3, and TFEB showed only modest, condition-dependent shifts. Rather than acting as clean antiviral effectors, miR-29a and miR-15b emerge as context-dependent modulators that can paradoxically favor SARS-CoV-2 replication—a cautionary signal for miRNA-based antiviral strategies.

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused a global pandemic, significantly impacting social and economic aspects of society. While belonging to the Coronaviridae family, SARS-CoV-2 exhibited unique characteristics that facilitated its widespread transmission and pathogenicity. This study aimed to investigate the molecular characterization and infection kinetics of emerging SARS-CoV-2 variants, focusing on four key virological aspects: viral entry mechanisms, replication dynamics, immune evasion strategies, and surface persistence. We isolated 11 SARS-CoV-2 variants from clinical samples and conducted in vitro studies using Calu-3 cell lines and pseudovirus systems to explore viral entry. Whole-genome sequencing identified mutations linked to increased replication and enhanced immune evasion, particularly through the inhibition of interferon responses. Additionally, persistence studies on common environmental surfaces (copper, aluminum, and plastic) revealed that certain variants, such as G446S, contributed to increased viral stability, suggesting potential for indirect transmission beyond direct person-to-person contact. Furthermore, we evaluated the effectiveness of “green” disinfectants, including tea tree oil and quercetin-based compounds, which demonstrated viral load reductions of over 95% within minutes, outperforming conventional alcohol- and UV-based disinfection methods. Notably, two influenza virus isolates belonging to highly divergent subtypes are sanitized as well while showing different persistence surface profiles compared to SARS-CoV-2. These findings highlight the evolutionary strategies employed by SARS-CoV-2 to ensure transmission, its ability to adapt under selective pressure, and the importance of ongoing surveillance of emerging variants. Moreover, the efficacy of environmentally sustainable disinfectants presents a promising strategy for reducing viral transmission in both clinical and community settings. IMPORTANCE: In this study, we evaluated the molecular profile of 11 SARS-CoV-2 variants, focusing on four key virological aspects: viral entry mechanisms, replication dynamics, immune evasion strategies, and surface persistence. Through whole-genome sequencing, we identified mutations linked to enhanced replication and immune evasion, notably through the suppression of interferon responses. Additionally, persistence studies on common environmental surfaces (copper, aluminum, and plastic) demonstrated that certain mutations, such as G446S, exhibited increased stability, suggesting a potential role for indirect transmission. This study underscores the need for continuous monitoring and the potential of eco-friendly disinfection approaches in controlling the spread of SARS-CoV-2 and possibly of other respiratory viruses.