|Reference : Contribution à l’étude de l’activité antivirale et du mécanisme moléculaire de la MX1...|
|Dissertations and theses : Doctoral thesis|
|Life sciences : Veterinary medicine & animal health|
|Contribution à l’étude de l’activité antivirale et du mécanisme moléculaire de la MX1 bovine|
|[en] Antiviral activities of the bovine MX1 and contribution to the study of its molecular mechanism|
|Baise, Etienne [Université de Liège - ULg > Département des sciences de la vie > Macromolécules biologiques >]|
|Université de Liège, Liège, Belgium|
|Doctorat en Sciences|
|HORISBERGER Michel A. (Membre étranger), Michel A.|
|Van Den Berg, Thierry|
|[en] MX ; IFN-alpha ; virus ; Influenza ; innate immunity ; MX1 ; bovine MX ; highly pathogenic|
|[fr] interferon ; MX1 ; immunité innée ; antiviral|
Type I interferons (IFNs a/b) induce the synthesis of many factors belonging to the innate immune system which is known to play an essential role as the first defence line against the viral infection. Among these contributors, the MX protein (a member of the large GTPase family) along with the double stranded (ds) RNA dependent protein kinase R (PKR) and the 2’5’ oligoadenylate synthetase/Rnase L system, has been shown to be one of the most efficient among the murine and the human species. The bovine counterpart of the MX system was, at the beginning of this work, described at the sole gene level (the CDS sequence) but its functional capacity was still totally unexplored. Accordingly, our first aim was to assess the ability of the bovine GTPase we called boMX1 to inhibit viruses infecting cattle. A Vero cell line (V103) conditionally expressing the boMX1 was established. To proof the concept, we firstly tested the inhibition of a canonical virus on this field, the vesicular stomatitis virus (VSV) which was confirmed to be as sensitive to boMX1 as previously shown to MXA (Homo sapiens). In a second step, we focused our investigation on the activity of boMX1 against two Paramyxoviridae viruses, the boRSV and the boPI3, both of these being sensitive to IFNs as reported in the literature and furthermore confirmed by our previous in vitro experiments. Although boMX1 was expected to be the most important factor of the type I interferon resistance recorded against boPI3 and boRSV, our study has shown that the bovine protein was not able to block these viruses belonging to the Respirovirus genus. Conversely, the famous Orthomyxoviridae virus member, Influenza A was shown to be almost completely inhibited in cells expressing boMX1. The inhibitory potential of boMX1 was so strong it could only be measured upon the replacement of the low pathogenic H1N1 strain used in the first assays by the hypervirulent H7N7 one. In this case, the protection rate was as high as 108. Typically, the value found for the human counterpart MXA is in the range of 103 – 104 and according to our knowledge, none of the MX proteins investigated so far have never been shown to be so effective against Influenza A. In the wave of these results, the well-known avian H5N1 Influenza A strain has been tested in vitro and in vivo. All the data reinforced the concept of a very high anti-Influenza A activity for BoMX1.
A such important antiviral effect appeared as an opportunity to initiate an experimental approach of the largely unknown underlying mechanism(s) of the MX antiviral activity. Our first objective was to identify the “primum movens” of the inhibition mechanism. Therefore, we followed the kinetic of the infection in V103 expressing or not the boMX1 during one single cycle. The evidence of an important activity of the bovine GTPase in the first hours post-infection led us to identify at the RNA level which replication step was the first to be blocked. Following the collected results, we adapted a primer extension method to quantify the genomic viral RNA (vRNA) early entry in the induced and non induced cell cultures. Finally, we tested a first interaction hypothesis between the boMX1 and a potential interacting protein sister.
|Département de Morphologie et Pathologie, Service de Pathologie spéciale|
|projet n° S-6042 octroyé par le Service fédéral publique belge pour la Santé publique, la Sécurité de la Chaîne alimentaire et de l’Environnement. ; This study is supported by the Belgian Federal Public Services for Public health, security of the food chain, and environment, grant S-6042|
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