ABSTRACT
Newly emerging SARS-CoV-2 variants may escape monoclonal antibodies (mAbs) and antiviral drugs. By using live virus assays, we assessed the ex vivo inhibition of the B.1 wild type (WT), delta and omicron BA.1 and BA.2 lineages by post-infusion sera from 40 individuals treated with bamlanivimab/etesevimab (BAM/ETE), casirivimab/imdevimab (CAS/IMD) and sotrovimab (SOT) as well as the activity of remdesivir, nirmatrelvir and molnupiravir. mAbs and drug activity were defined as the serum dilution (ID50) and drug concentration (IC50), respectively, showing 50% protection of virus-induced cytopathic effect. All pre-infusion sera were negative for SARS-CoV-2 neutralizing activity. BAM/ETE, CAS/IMD and SOT showed activity against the WT (ID50 6,295 [4,355-8,075] for BAM/ETE; 18,214 [16,248-21,365] for CAS/IMD and 456 [265-592] for SOT) and the delta (14,780 [ID50 10,905-21,020] for BAM/ETE, 63,937 [47,211-79,971] for CAS/IMD and 1,103 [843-1,334] for SOT). Notably, only SOT was active against BA.1 (ID50 200 [37-233]) while BA.2 was neutralized by CAS/IMD (ID50 174 [134-209] ID50) and SOT (ID50 20 [9-31] ID50) but not by BAM/ETE. No significant inter-variant IC50 differences were observed for molnupiravir (1.5±0.1/1.5±0.7/1.0±0.5/0.8±0.01 μM for WT/delta/BA.1/BA.2, respectively); nirmatrelvir (0.05±0.02/0.06±0.01/0.04±0.02/0.04±0.01 μM) and remdesivir (0.08±0.04/0.11±0.08/0.05±0.04/0.08±0.01 μM). Continued evolution of SARS-CoV-2 requires updating the mAbs arsenal, however antivirals have so far remained unaffected.
ABSTRACT
The aim of this study is the characterization and genomic tracing by phylogenetic analyses of 59 new SARS-CoV-2 Italian isolates obtained from patients attending clinical centres in North and Central Italy until the end of April 2020. All but one of the newly characterized genomes belonged to the lineage B.1, the most frequently identified in European countries, including Italy. Only a single sequence was found to belong to lineage B. A mean of 6 nucleotide substitutions per viral genome was observed, without significant differences between synonymous and non-synonymous mutations, indicating genetic drift as a major source for virus evolution. tMRCA estimation confirmed the probable origin of the epidemic between the end of January and the beginning of February with a rapid increase in the number of infections between the end of February and mid-March. Since early February, an effective reproduction number (Re) greater than 1 was estimated, which then increased reaching the peak of 2.3 in early March, confirming the circulation of the virus before the first COVID-19 cases were documented. Continuous use of state-of-the-art methods for molecular surveillance is warranted to trace virus circulation and evolution and inform effective prevention and containment of future SARS-CoV-2 outbreaks.
Subject(s)
COVID-19ABSTRACT
The aim of this study is the characterization and genomic tracing by phylogenetic analyses of 59 new SARS-CoV-2 Italian isolates obtained from patients attending clinical centres in North and Central Italy until the end of April 2020. All but one of the newly characterized genomes belonged to the lineage B.1, the most frequently identified in European countries, including Italy. Only a single sequence was found to belong to lineage B. A mean of 6 nucleotide substitutions per viral genome was observed, without significant differences between synonymous and non-synonymous mutations, indicating genetic drift as a major source for virus evolution. tMRCA estimation confirmed the probable origin of the epidemic between the end of January and the beginning of February with a rapid increase in the number of infections between the end of February and mid-March. Since early February, an effective reproduction number (Re) greater than 1 was estimated, which then increased reaching the peak of 2.3 in early March, confirming the circulation of the virus before the first COVID-19 cases were documented. Continuous use of state-of-the-art methods for molecular surveillance is warranted to trace virus circulation and evolution and inform effective prevention and containment of future SARS-CoV-2 outbreaks.