New Tanzanian Variant Detected In Angola From An Entirely New Branch Of SARS-CoV-2

The versatility of SARS-CoV-2 to evolve new variants that increase transmissibility, virulence, and immune evasion is a new troubling feature of the Covid-19 pandemic. The recent discovery of a novel variant emerging from Tanzania adds a new chapter to this disturbing story. Up until the discovery of the new variant, all other variants of interest or concern derive from a common ancestral virus, the B.1 strain that first made its appearance in early 2020. This is not so for the newly described variant. It evolved from an entirely different source, the A lineage, a finding that substantially expands our understanding of the repertoire of mutants we must be prepared to contend with in the months and years ahead.

The difference between the A and B lineages are three mutations that have come to define the B lineage that has displaced almost all others around the world. The common understanding is that a single amino acid change in the spike protein, the D614G mutation, increases both the ability of the virus to bind to the ACE2 receptor and, at the same time, stabilizes the interaction between the S1 and S2 protein of the spike, conferring an increase in transmissibility. I and others have suggested that the D614G substitution may not be all to the story of success for the B.1 variant. The B.1 linage viruses carry two additional mutations: the P323L mutation in the RNA-dependent RNA polymerase (NSP12), which is the key to virus replication and the production of viral mRNA and another mutation in the 5 prime untranslated region of the genome. Although hardly studied, both of these mutations may contribute, along with D614G, to the replication competence and transmissibility in the spike protein.

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© William A. Haseltine, PhD. All Rights Reserved.