Lama antibodies to fight the coronavirus

The plasma of a young Belgian llama contains special little antibodies. The latter are capable of neutralizing the infection of the coronaviruses, responsible for SARS, the Seas but also Covid-19.

Winter is a llama -year-old boy peacefully grazing on the grass near the city of Ghent in Belgium. The young camelid could also play a key role in research treatments against Covid-19.

Indeed, Winter was immunized with a infusion containing the protein surface (protein S) of two coronavirus : the Seas-CoV and the Sars-CoV-1. Scientists have identified in the plasma of the little lama antibody neutralizers which have been shown to be effective against two pseudotyped viral particles (one lentivirus modified to express the surface proteins of coronaviruses) mimicking two strains of coronaviruses against which Winter has been immunized, as well as the SARS-CoV-2.

The results of this study will appear in the journal Cell. A preliminary, but peer-reviewed, version is already available.

Small neutralizing antibodies

These particular antibodies are a subclass of IgG specific for camelids called VHH. They only have a heavy chain whereas conventional IgGs have a light chain and a heavy chain. VHH therefore have only one variable domain, located on the heavy chain.

A crystallographic analysis made it possible to determine on which part of the virus reconstituted VHH from Winter plasma bind: the receptor binding domain (RBD) of protein S. Several have demonstrated their neutralizing action against Sars-CoV-1 and Mers-CoV on cell cultures in vitro. One of them, VHH-72, is capable of neutralizing the infection of the viral pseudo-particle imitating Sars-CoV-1 but also that imitating Sars-CoV-2.

Smaller than conventional IgG, VHH are stable and could be administered via an inhalation spray, in particular to treat respiratory infections. Scientists hope that the neutralizing ability of llama's VHHs makes them serious candidates for treating the Covid-19.

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Coronavirus: tomorrow, all masked? SARS-CoV-2. It appeared in China in December 2019. Since then, it has claimed tens of thousands of lives worldwide. To limit the spread of this coronavirus and in the absence of treatment or vaccine, various measures have been devised. Among them, the wearing of a mask.

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