Replacement of the Alpha variant of SARS-CoV-2 by the Delta variant in Lebanon between April and June 2021 (preprint)

Background The COVID-19 pandemic continues to expand globally, with case numbers rising in many areas of the world, including the Eastern Mediterranean Region. Lebanon experienced its largest wave of COVID-19 infections from January to April 2021. Limited genomic surveillance was undertaken, with just twenty six SARS-CoV-2 genomes available for this period, nine of which were from travellers from Lebanon detected by other countries. Additional genome sequencing is thus needed to allow surveillance of variants in circulation. Methods Nine hundred and five SARS-CoV-2 genomes were sequenced using the ARTIC protocol. The genomes were derived from SARS-CoV-2-positive samples, selected retrospectively from the sentinel COVID-19 surveillance network, to capture diversity of location, sampling time, gender, nationality and age. Results Although sixteen PANGO lineages were circulating in Lebanon in January 2021, by February there were just four, with the Alpha variant accounting for 97% of samples. In the following two months, all samples contained the Alpha variant. However, this had changed dramatically by June and July, when all samples belonged to the Delta variant. Discussion This study provides a ten-fold increase in the number of SARS-CoV-2 genomes available from Lebanon. The Alpha variant, first detected in the UK, rapidly swept through Lebanon, causing the country’s largest wave to date, which peaked in January 2021. The Alpha variant was introduced to Lebanon multiple times despite travel restrictions, but the source of these introductions remains uncertain. The Delta variant was detected in Gambia in travellers from Lebanon in mid-May, suggesting community transmission in Lebanon several weeks before this variant was detected in the country. Prospective sequencing in June/July 2021 showed that the Delta variant had completely replaced the Alpha variant in under six weeks.

SARS-CoV-2 and ORF3a: Non-Synonymous Mutations and Polyproline Regions (preprint)

The effect of the rapid accumulation of non-synonymous mutations on the pathogenesis of SARS-CoV-2 is not yet known. To predict the impact of non-synonymous mutations and polyproline regions identified in ORF3a on the formation of B-cell epitopes and their role in evading the immune response, nucleotide and protein sequences of 537 available SARS-CoV-2 genomes were analyzed for the presence of non-synonymous mutations and polyproline regions. Mutations were correlated with changes in epitope formation. A total of 19 different non-synonymous amino acids substitutions were detected in ORF3a among 537 SARS-CoV-2 strains. G251V was the most common and identified in 9.9% (n=53) of the strains and was predicted to lead to the loss of a B-cell like epitope in ORF3a. Polyproline regions were detected in two strains (EPI_ISL_410486, France and EPI_ISL_407079, Finland) and affected epitopes formation. The accumulation of non-synonymous mutations and detected polyproline regions in ORF3a of SARS-CoV-2 could be driving the evasion of the host immune response thus favoring viral spread. Rapid mutations accumulating in ORF3a should be closely monitored throughout the COVID-19 pandemic. ImportanceAt the surge of the COVID-19 pandemic and after three months of the identification of SARS-CoV-2 as the disease-causing pathogen, nucleic acid changes due to host-pathogen interactions are insightful into the evolution of this virus. In this paper, we have identified a set of non-synonymous mutations in ORF3a and predicted their impact on B-cell like epitope formation. The accumulation of non-synonymous mutations in ORF3a could be driving protein changes that mediate immune evasion and favoring viral spread.