Variants

Numerous SARS-CoV-2 variants have appeared over recent months, including the Californian or Epsilon (ε) variant. This new strain emerged at the beginning of 2021 in California, and had been detected in more than 34 countries, including France, by May. The spike surface protein of this variant carries the L452R mutation in the RBD (the region […]

The mutation rate of SARS-CoV-2 is relatively low due to its correcting activity during genome replication. However, its high rate of replication and its high transmissibility lead to the rapid emergence of variants. Amongst those that have emerged, the Alpha (a) or UK variant quickly became dominant. The Beta (b) or South African variant also […]

The emergence of new SARS-CoV-2 variants of concern in recent months has highlighted the shortcomings of the United States in terms of monitoring these variants: more than 30 countries sequence more strains than the Americans. The more strains are sequenced, the more it is possible to follow, to understand and to anticipate the emergence of […]

B lymphocytes are found in active form in the blood to produce antibodies, or in the form of memory B lymphocytes that will be reactivated during a second encounter with the pathogen, thereby giving long-term protection. The antibodies produced by B lymphocytes remained unchanged and determine the configuration of the humoral response, while the memory […]

The Delta (formerly Indian) variant is now present in many countries. It was first identified in India in October 2020 and rapidly became dominant in several regions of the country, then in the UK. The variant seems to be more transmissible than the Alpha (UK) variant. This strain is composed of 3 sub-types presenting different […]

The anti-SARS-CoV-2 immune response is made up of antibodies, which block viral infection, and the cellular response, which works through cytotoxic lymphocytes (CTLs) recognising and destroying infected cells. This latter function requires viral proteins presented on the surface of cells by the HLA-I (Human Leukocyte Antigen) complex to enable their recognition. Several mutations of SARS-CoV-2 […]

Brazil is one of the countries most severely affected by the health crisis caused by COVID-19 and had registered more than 13 million cases and 300 000 deaths by March 2021. Amazonas, with its capital Manaus, is among the most affected states; two thirds of its inhabitants had been infected by October 2020. But this […]

SARS-CoV-2 has a genome made up of a single-strand RNA molecule. When it is replicated by the polymerase enzyme to make new virions, copying errors can arise in the sequence. These errors, if they are selectively advantageous, can become dominant. Early in the pandemic, the D614G mutation appeared from the Wuhan strain and quickly became […]

Although SARS-CoV-2 mutates little in comparison to other RNA viruses, the relentless course of the COVID-19 pandemic and the fact of its high transmissibility means that the original Wuhan strain has already acquired a certain genetic diversity. This is shown in the regular discovery of new variants, modifying their transmission, their virulence and their capacities […]

The UK variant of SARS-CoV-2, detected for the first time in the south of England in September 2020, spread rapidly through the country and became the dominant strain. It has now been detected in more than 114 countries across the globe. This variant is characterized by 14 mutations and 3 deletions, of which 8 are […]