An acute respiratory syndrome (COVID-19), caused by a novel coronavirus (SARS-CoV-2) with a high rate of morbidity and elevate mortality, has emerged as one of the most important threats to humankind in the last centuries. Rigorous determination of SARS-CoV-2 infectivity is very difficult owing to the continuous evolution of the virus, with its single nucleotide polymorphism (SNP) variants and many lineages. However, it is urgently necessary to study the virus in depth, to understand the mechanism of its pathogenicity and virulence, and to develop effective therapeutic strategies. The present contribution summarizes in a succinct way the current knowledge on the evolutionary and structural features of the virus, with the aim of clarifying its mutational pattern and its possible role in the ongoing pandemic.

COVID-19 outbreak had a major impact on the organization of care in Italy, and a survey to evaluate provision of for arrhythmia during COVID-19 outbreak (March-April 2020) was launched. A total of 104 physicians from 84 Italian arrhythmia centres took part in the survey. The vast majority of participating centres (95.2%) reported a significant reduction in the number of elective pacemaker implantations during the outbreak period compared to the corresponding two months of year 2019 (50.0% of centres reported a reduction of > 50%). Similarly, 92.9% of participating centres reported a significant reduction in the number of implantable cardioverter-defibrillator (ICD) implantations for primary prevention, and 72.6% a significant reduction of ICD implantations for secondary prevention (> 50% in 65.5 and 44.0% of the centres, respectively). The majority of participating centres (77.4%) reported a significant reduction in the number of elective ablations (> 50% in 65.5% of the centres). Also the interventional procedures performed in an emergency setting, as well as acute management of atrial fibrillation had a marked reduction, thus leading to the conclusion that the impact of COVID-19 was disrupting the entire organization of health care, with a massive impact on the activities and procedures related to arrhythmia management in Italy.

Background Since the first outbreak of SARS-CoV-2, the clinical characteristics of the Coronavirus Disease 2019 (COVID-19) have been progressively changed. Data reporting a viral intra-host and inter-host evolution favouring the appearance of mild SARS-CoV-2 strains are since being accumulating. To better understand the evolution of SARS-CoV-2 pathogenicity and its adaptation to the host, it is therefore crucial to investigate the genetic and phenotypic characteristics of SARS-CoV-2 strains circulating lately in the epidemic. Methods Nasopharyngeal swabs have been analyzed for viral load in the early (March 2020) and late (May 2020) phases of epidemic in Brescia, Italy. Isolation of SARS-CoV-2 from 2 high viral load specimens identified on March 9 (AP66) and on May 8 (GZ69) was performed on Vero E6 cells. Amount of virus released was assessed by quantitative PCR. Genotypic characterization of AP66 and GZ69 was performed by next generation sequencing followed by an in-depth in silico analysis of nucleotide mutations. Results The SARS-CoV-2 GZ69 strain, isolated in May from an asymptomatic healthcare worker, showed an unprecedented capability of replication in Vero E6 cells in the absence of any evident cytopathic effect. Vero E6 subculturing, up to passage 4, showed that SARS-CoV-2 GZ69 infection was as productive as the one sustained by the cytopathic strain AP66. Whole genome sequencing of the persistently replicating SARS-CoV-2 GZ69 has shown that this strain differs from the early AP66 variant in 9 nucleotide positions (C2939T; C3828T; G21784T; T21846C; T24631C; G28881A; G28882A; G28883C; G29810T) which lead to 6 non-synonymous substitutions spanning on ORF1ab (P892S; S1188L), S (K74N; I95T) and N (R203K, G204R) proteins. Conclusions Identification of the peculiar SARS-CoV-2 GZ69 strain in the late Italian epidemic highlights the need to better characterize viral variants circulating among asymptomatic or paucisymptomatic individuals. The current approach could unravel the ways for future studies aimed at analyzing the selection process which favours viral mutations in the human host.

SARS-CoV-2-associated acute respiratory distress syndrome (ARDS) and acute lung injury are life-threatening manifestations of severe viral infection. The pathogenic mechanisms that lead to respiratory complications, such as endothelialitis, intussusceptive angiogenesis, and vascular leakage remain unclear. In this study, by using an immunofluorescence assay and in situ RNA-hybridization, we demonstrate the capability of SARS-CoV-2 to infect human primary lung microvascular endothelial cells (HL-mECs) in the absence of cytopathic effects and release of infectious particles. Preliminary data point to the role of integrins in SARS-CoV-2 entry into HL-mECs in the absence of detectable ACE2 expression. Following infection, HL-mECs were found to release a plethora of pro-inflammatory and pro-angiogenic molecules, as assessed by microarray analyses. This conditioned microenvironment stimulated HL-mECs to acquire an angiogenic phenotype. Proteome analysis confirmed a remodeling of SARS-CoV-2-infected HL-mECs to inflammatory and angiogenic responses and highlighted the expression of antiviral molecules as annexin A6 and MX1. These results support the hypothesis of a direct role of SARS-CoV-2-infected HL-mECs in sustaining vascular dysfunction during the early phases of infection. The construction of virus-host interactomes will be instrumental to identify potential therapeutic targets for COVID-19 aimed to inhibit HL-mEC-sustained inflammation and angiogenesis upon SARS-CoV-2 infection.

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