Genetic analysis of SARS-CoV-2 strains collected from North Africa: viral origins and mutational spectrum

The SARS-CoV-2 identified as coronavirus species associated with severe acute respiratory syndrome. At the time of writing, the genetic diversity of Moroccan strains of SARS-CoV-2 is poorly documented. The present study aims to analyze and identify the genetic variants of fortyeight Moroccan strains of SARS-CoV-2 collected from mid-March to the end of May and the prediction of their possible sources. Our results revealed 108 mutations in Moroccan SARS-CoV-2, 50% were non-synonymous were present in seven genes (S, M, N, E, ORF1ab, ORF3a, and ORF8) with variable frequencies. Remarkably, eight non-synonymous mutations were predicted to have a deleterious effect for (ORF1ab, ORF3a, and the N protein. The analysis of the haplotype network of Moroccan strains suggests different sources of SARS-CoV-2 infection in Morocco. Likewise, the phylogenetic analysis revealed that these Moroccan strains were closely related to those belonging to the five continents, indicating no specific strain dominating in Morocco. These findings have the potential to lead to new comprehensive investigations combining genomic data, epidemiological information, and clinical characteristics of SARS-CoV-2 patients in Morocco and could indicate that the developed vaccines are likely to be effective against Moroccan strains.

Genomic diversity and hotspot mutations in 30,983 SARS-CoV-2 genomes: moving toward a universal vaccine for the "confined virus"?

The COVID-19 pandemic has been ongoing since its onset in late November 2019 in Wuhan, China. Understanding and monitoring the genetic evolution of the virus, its geographical characteristics, and its stability are particularly important for controlling the spread of the disease and especially for the development of a universal vaccine covering all circulating strains. From this perspective, we analyzed 30,983 complete SARS-CoV-2 genomes from 79 countries located in the six continents and collected from December 24, 2019, to May 13, 2020, according to the GISAID database. Our analysis revealed the presence of 3,206 variant sites, with a uniform distribution of mutation types in different geographic areas. Remarkably, a low frequency of recurrent mutations has been observed; only 169 mutations (5.27%) had a prevalence greater than 1% of genomes. Nevertheless, fourteen non-synonymous hotspot mutations (> 10%) have been identified at different locations along the viral genome; eight in ORF1ab polyprotein (in nsp2, nsp3, transmembrane domain, RdRp, helicase, exonuclease, and endoribonuclease), three in nucleocapsid protein and one in each of three proteins: spike, ORF3a, and ORF8. Moreover, 36 non-synonymous mutations were identified in the RBD of the spike protein with a low prevalence (<1%) across all genomes, of which only four could potentially enhance the binding of the SARS-CoV-2 spike protein to the human ACE2 receptor. These results along with mutational frequency dissimilarity and intra-genomic divergence of SARS-CoV-2 could indicate that the SARS-CoV-2 is not yet adapted to its host. Unlike the influenza virus or HIV viruses, the low mutation rate of SARS-CoV-2 makes the development of an effective global vaccine very likely.

Large scale genomic analysis of 3067 SARS-CoV-2 genomes reveals a clonal geodistribution and a rich genetic variations of hotspots mutations

In late December 2019, an emerging viral infection COVID-19 was identified in Wuhan, China, and became a global pandemic. Characterization of the genetic variants of SARS-CoV-2 is crucial in following and evaluating it spread across countries. In this study, we collected and analyzed 3,067 SARS-CoV-2 genomes isolated from 55 countries during the first three months after the onset of this virus. Using comparative genomics analysis, we traced the profiles of the whole-genome mutations and compared the frequency of each mutation in the studied population. The accumulation of mutations during the epidemic period with their geographic locations was also monitored. The results showed 782 variant sites, of which 512 (65.47%) had a non-synonymous effect. Frequencies of mutated alleles revealed the presence of 38 recurrent non-synonymous mutations, including ten hotspot mutations with a prevalence higher than 0.10 in this population and distributed in six SARS-CoV-2 genes. The distribution of these recurrent mutations on the world map revealed certain genotypes specific to the geographic location. We also found co-occurring mutations resulting in the presence of several haplotypes. Moreover, evolution over time has shown a mechanism of mutation co-accumulation which might affect the severity and spread of the SARS-CoV-2. On the other hand, analysis of the selective pressure revealed the presence of negatively selected residues that could be taken into considerations as therapeutic targets We have also created an inclusive unified database (http://genoma.ma/covid-19/) that lists all of the genetic variants of the SARS-CoV-2 genomes found in this study with phylogeographic analysis around the world.