Xenothera is a biotechnology company located in Nantes, created in 2014 from a common technology of INSERM, the Université de Nantes and the Nantes University Hospital. Immunology specialist, Xenothera has developed a unique technology based on the production in animals of humanized polyclonal antibodies. This strategy offers the following double interest: i) the “polyclonal character of the antibodies” which recognize not one, but several antigenic motifs present on the pathogen, thus neutralizing it more effectively and ii) the “glyco-humanization” of the antibodies which allows on the one hand to avoid the allergic risk due to the presence on the surface of the antibodies of xenoantigens and on the other hand to avoid “antibody-dependent enhancement * (ADE)”, a mechanism which facilitates the infection of cells by viruses coated with antibodies.

Sebastien BONI

This technology was initially and mainly developed to combat organ transplant rejection, but with possible applications in the case of viral infections, such as Ebola, Zika and the coronavirus family, where the mechanism of ADE potentiates the infection of cells.

Xenothera was thus able to react very quickly to the Covid-19 pandemic, by offering a first clinical batch of antibodies (scheduled to enter a phase II clinical trial in July 2020) which could be delivered to several hundred patients in a state of of moderate Covid-19 not placed in intensive care.

It is in this context that Xenothera requested the expertise of the lentiviral vector production core facility, LentiVec, in order to confirm the characteristics of their therapeutic tool..

LentiVec is a production core facility for Angevin lentiviral vectors created in 2013 within the SFR-ICAT of the health site of the Université d'Angers. It is part of the Atlanpole Biothérapies competitiveness cluster, in its regenerative medicine subsidiary Bioregate. She joined Biogenouest network in 2016, in the Functional Exploration Axis.

LentiVec allows the custom construction of lentiviral vectors specific to the gene of interest that the researcher wishes to express. More generally, it provides the various regional research teams and the western region with know-how and experience in gene transfer.

Lentiviral vectors, derived from HIV-1, are able to deliver stable genetic information within cells, without selection pressure. They integrate their genome into that of the cell they infect. It is possible to target this information, within a given tissue, either by placing upstream of the gene of interest a promoter specific for the targeted tissue, or by expressing on the surface of the viral particle an envelope protein whose receptor is expressed exclusively on the surface of cells constituting the target tissue.

It is thanks to this last feature, called pseudo-typing, that LentiVec was requested by Xenothera, to confirm the absence of ADE with the use of their humanized polyclonal antibodies.

The general principle is to produce lentiviral particles expressing eGFP (a gene encoding a fluorescent protein) and carrying on their surface the envelope protein of SARS-CoV-2 (nCovid-2019), then to use these particles to analyze the infection on cells provided or lacking the SARS-CoV-2 receptor (nCovid-2019): the ACE2 receptor (Angiotensin-Converting Enzyme 2).

The first stage of the project, carried out in collaboration between LentiVec and Xenothera, was the development of “ in silico Of an optimized sequence encoding the SARS-CoV-2 envelope protein (nCovid-2019) so that it can be efficiently expressed on the surface of lentiviral particles. The following steps were the molecular construction of this sequence using innovative molecular biology tools from the company TaKaRa : “In-Fusion®”, then the production of particles. Xenothera demonstrated the expression of the protein on the surface of the cells used for the production of the particles. The final stages of the project were the production and titration of the particles, under the responsibility of LentiVec, before their use through neutralization tests in the presence of cells lacking ACE2 and the humanized polyclonal antibodies of Xenothera.

* or facilitation of infection by antibodies