Genome Evolution of Two Genetically Homogeneous Infectious Bursal Disease Virus Strains During Passages in vitro and ex vivo in the Presence of a Mutagenic Nucleoside Analog

Liliana Cubas-Gaona (1, 2) , Alexandre Flageul (1, 2) , Céline Courtillon (1, 2) , Francois-Xavier Briand (1, 2) , Maud Contrant (1, 3) , Stephanie Bougeard (1, 4) , Pierrick Lucas (1, 3) , Hélène Quenault (1, 3) , Aurélie Leroux (1, 3) , Alassane Keita (1, 5) , Michel Amelot (1, 5) , Béatrice Grasland (1, 2) , Yannick Blanchard (1, 3) , Nicolas Eterradossi (1, 2) , Paul Alun Brown (1, 2) , Sébastien Mathieu Soubies (1, 2)

1 Laboratoire de Ploufragan-Plouzané-Niort [ANSES]
2 VIPAC - Virologie, Immunologie, Parasitologie Avaires et Cunicoles
3 GVB - Génétique Virale et Biosécurité
4 EPISABE - Epidémiologie, Santé et Bien-être
5 SELEAC - Service d'élevage et d'expérimentation avicole et cunicole

The avibirnavirus infectious bursal disease virus (IBDV) is responsible for a highly contagious and sometimes lethal disease of chickens ( Gallus gallus ). IBDV genetic variation is well-described for both field and live-attenuated vaccine strains, however, the dynamics and selection pressures behind this genetic evolution remain poorly documented. Here, genetically homogeneous virus stocks were generated using reverse genetics for a very virulent strain, rvv, and a vaccine-related strain, rCu-1. These viruses were serially passaged at controlled multiplicities of infection in several biological systems, including primary chickens B cells, the main cell type targeted by IBDV in vivo . Passages were also performed in the absence or presence of a strong selective pressure using the antiviral nucleoside analog 7-deaza-2′-C-methyladenosine (7DMA). Next Generation Sequencing (NGS) of viral genomes after the last passage in each biological system revealed that (i) a higher viral diversity was generated in segment A than in segment B, regardless 7DMA treatment and viral strain, (ii) diversity in segment B was increased by 7DMA treatment in both viruses, (iii) passaging of IBDV in primary chicken B cells, regardless of 7DMA treatment, did not select cell-culture adapted variants of rvv, preserving its capsid protein (VP2) properties, (iv) mutations in coding and non-coding regions of rCu-1 segment A could potentially associate to higher viral fitness, and (v) a specific selection, upon 7DMA addition, of a Thr329Ala substitution occurred in the viral polymerase VP1. The latter change, together with Ala270Thr change in VP2, proved to be associated with viral attenuation in vivo . These results identify genome sequences that are important for IBDV evolution in response to selection pressures. Such information will help tailor better strategies for controlling IBDV infection in chickens.

Mots clés: 7DMA; IBDV; chicken B cells; evolution; mutation frequency; passages; viral diversity

Domaines: Médecine vétérinaire et santé animale

Liliana Cubas-Gaona, Alexandre Flageul, Céline Courtillon, Francois-Xavier Briand, Maud Contrant, et al.. Genome Evolution of Two Genetically Homogeneous Infectious Bursal Disease Virus Strains During Passages in vitro and ex vivo in the Presence of a Mutagenic Nucleoside Analog. Frontiers in Microbiology, 2021, 12, pp.678563. ⟨10.3389/fmicb.2021.678563⟩. ⟨anses-03455514⟩